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Title:
The Gatun structure a geological assessment of a newly recognized impact structure near Lake Gatun in the Republic of Panama
Physical Description:
Book
Language:
English
Creator:
Tornabene, Livio Leonardo
Publisher:
University of South Florida
Place of Publication:
Tampa, Fla.
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Subjects

Subjects / Keywords:
Meteorite craters -- Panama -- Lake Gatun Region   ( lcsh )
meteorite impact
impact crater
astrobleme
cryptovolcanic
shock metamorphism
impactites
spherules
maskelynite
lithic breccias
asteroid impact
breccias
melt breccias
glass breccias
impacts
Dissertations, Academic -- Geology -- Masters -- USF   ( lcsh )
Genre:
government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
ABSTRACT: The Gatun Structure, (Latitude N 09° 05ʹ 58.1", Longitude W 79° 47ʹ 21.8", situated in the triple-canopy rainforest 10 km to the WSW of the Gamboa and about 2 km south of the Isle of Barbacoas, Republic de Panama), is a partially inundated, quasi-concentric surface feature 2.2 - 3km in diameter, which appears in aerial photographs and in radar imagery as an arcuate chain of islands with a raised center. Although the structure has been heavily weathered and altered, it has retained morphology consistent with complex craters: an elevated circular central uplift 500-600 m in diameter and 50m high, and arcuate boundary ridges (a rim structure?) ranging from 50-100 meters high. Within the central peak, highly altered and fractured siltstone of the Gatuncillo (?) formation (Eocene) (+-) older rocks are uplifted and exposed through surrounding calcareous units of the Caimito formation (Oligocene) and the Las Cascadas formation (Miocene), the major target rocks in the region. Lithologies in the structure include highly fractured siliciclastic rocks (siltstone, sandstones and greywackes), limestones with anomalous spherical glass inclusions, both black and white hypocrystalline glasses (possible melt rocks), lithic fragmental breccias, and melt-bearing breccias (possible impact melt breccias and suevites), some of which contain flow banding and evidence for selective melting of minerals. Three types of spherules (glass, fluid-drop and lithic), a pyroxene-quartz "necklace" disequilibrium structure (coronas), plagioclase feldspars exhibiting mosaicism and partially amorphization, possible liquid immiscibility between melts of calcite and felpspathic glass, as well as decomposition of titanomagnite or ulvospinel, are all petrographic indicators of a hypervelocity impact event. The structure is crosscut by numerous dikes of unshocked basalt and basaltic andesite related to volcanism along the Panamanian segment of the Central American arc to the south. However, the lithologies of the Gatun Structure are chemically inconsistent with the regional volcanic rocks and the unshocked volcanic rocks that crosscut the structure. The lack of an igneous relationship between the Gatun structure and the explosive volcanism of Panamanian arc the presence of classical shock lithologies within the site, and the occurrence of spherules, maskelynite and other disequilibrium shock features in the rocks, an impact origin is our preferred interpretation for the Gatun structure.
Thesis:
Thesis (M.S.)--University of South Florida, 2002.
Bibliography:
Includes bibliographical references.
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System Details:
Mode of access: World Wide Web.
Statement of Responsibility:
by Livio Leonardo Tornabene.
General Note:
Title from PDF of title page.
General Note:
Document formatted into pages; contains 558 pages.
General Note:
Original thesis submitted in HTML and can be accessed at http://www.lib.usf.edu/ETD-db/theses/available/etd-10122001-142859/unrestricted/frame.html
General Note:
td.pdf

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oclc - 48982775
notis - AJL6119
usfldc doi - E14-SFE0000019
usfldc handle - e14.19
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ABSTRACT: The Gatun Structure, (Latitude N 09 05 58.1", Longitude W 79 47 21.8", situated in the triple-canopy rainforest 10 km to the WSW of the Gamboa and about 2 km south of the Isle of Barbacoas, Republic de Panama), is a partially inundated, quasi-concentric surface feature 2.2 3km in diameter, which appears in aerial photographs and in radar imagery as an arcuate chain of islands with a raised center. Although the structure has been heavily weathered and altered, it has retained morphology consistent with complex craters: an elevated circular central uplift 500-600 m in diameter and 50m high, and arcuate boundary ridges (a rim structure?) ranging from 50-100 meters high. Within the central peak, highly altered and fractured siltstone of the Gatuncillo (?) formation (Eocene) (+-) older rocks are uplifted and exposed through surrounding calcareous units of the Caimito formation (Oligocene) and the Las Cascadas formation (Miocene), the major target rocks in the region. Lithologies in the structure include highly fractured siliciclastic rocks (siltstone, sandstones and greywackes), limestones with anomalous spherical glass inclusions, both black and white hypocrystalline glasses (possible melt rocks), lithic fragmental breccias, and melt-bearing breccias (possible impact melt breccias and suevites), some of which contain flow banding and evidence for selective melting of minerals. Three types of spherules (glass, fluid-drop and lithic), a pyroxene-quartz "necklace" disequilibrium structure (coronas), plagioclase feldspars exhibiting mosaicism and partially amorphization, possible liquid immiscibility between melts of calcite and felpspathic glass, as well as decomposition of titanomagnite or ulvospinel, are all petrographic indicators of a hypervelocity impact event. The structure is crosscut by numerous dikes of unshocked basalt and basaltic andesite related to volcanism along the Panamanian segment of the Central American arc to the south. However, the lithologies of the Gatun Structure are chemically inconsistent with the regional volcanic rocks and the unshocked volcanic rocks that crosscut the structure. The lack of an igneous relationship between the Gatun structure and the explosive volcanism of Panamanian arc the presence of classical shock lithologies within the site, and the occurrence of spherules, maskelynite and other disequilibrium shock features in the rocks, an impact origin is our preferred interpretation for the Gatun structure.
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PAGE 1

The Gatun Structure Table of Contents The Gatun Structure: A geological assessment of a newly recognized impact structure near Lake Gatun in the Republic de Panama by Livio Leonardo Tornabene A thesis submitted in partial fulfillment of the requirements for the degree of Master Of Science Department of Geology College of Arts and Sciences University of South Florida Jeffrey G. Ryan Ph.D., Major Professor Sarah E. Kruse Ph.D., Member Peter J. Harries Ph.D., Member November, 2001 Keywords: impacts, meteorite impact, asteroid impact, impact crater, astrobleme, cryptovolcanic, shock metamorphism, maskelynite, spherules, impactites, breccias, melt breccias, glass breccias, lithic breccias Copyright 2001 [University of South Florida]. All rights reserved. Revised: November 21, 2001 09:46:41 PM

PAGE 3

The Gatun Structure: A geological assessment of a newly recognized impact structure near Lake Gatun in the Republic de Panama by Livio Leonardo Tornabene A thesis submitted in partial fulfillment of the requirements for the degree of Master Of Science Department of Geology College of Arts and Sciences University of South Florida Jeffrey G. Ryan Ph.D., Major Professor Sarah E. Kruse Ph.D., Member Peter J. Harries Ph.D., Member November, 2001 Keywords: impacts, meteorite impact, asteroid impact, impact crater, astrobleme, cryptovolcanic, shock metamorphism, maskelynite, spherules, impactites, breccias, melt breccias, glass breccias, lithic breccias Copyright 2001 [University of South Florida]. All rights reserved. Revised: November 21, 2001 09:46:41 PM

PAGE 4

DEDICATION This work is dedicated to my family who always believes in me, especially when I do not. My brother Mark gives me courage to stand up for what I believe in, my mother Diana gives me wisdom and faith to conquer my fears, and my father Rosario gives me good sense and the desire to persevere even when I am faced with defeat. I owe most of my success to them. This work is also dedicated to Robert H. Stewart, the pioneering Panamanian geologist who was well ahead of his time, without him, none of this work would be possible.

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ACKNOWLEDGMENTS I would like to thank all the people who have made this work possible. Dr. Jeffrey G. Ryan went above and beyond the call of duty when he allowed me to pursue a thesis well outside the scope of his own research. He has my eternal gratitude for his patience, advice and, most importantly, for the moral support he gave me when I believed I could not succeed. I am especially grateful to Robert H. Stewart, whom bestowed upon me this project when he gave me the eleven samples he collected from the Gatun Structure in 1990 and 1995. I would like to thank the other members of my committee, Dr. Peter J. Harries and Dr. Sarah Kruse for their constructive criticism and especially for their patience with my project and I. This work would be nigh impossible if it were not for the companionship and patience of my officemates Ivan P. Savov and Megan C. Davis. I would like extend a very special thanks to two of my very best friends Thomas J. Carey and Gene Foster. Without Thomas, my expedition in the Republic de Panama would have been extremely difficult, if not impossible. Gene was always there to help me (when no one else would), support me, mock me, make me laugh, keep me company, hear out my most outrageous ideas and lose sleep with me while I processed my samples and conducted unorthodox experiments. I owe much to my friends and colleagues down in the Republic de Panama. Francia C. de Sierra, Director General De Recursos Minerales, granted Thomas J. Carey and I permits to

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conduct geological research in the Republic de Panama. Dr. Anthony G. Coates of STRI (Smithsonian Tropical Research Institute) bestowed upon us information, maps and all-weather note books. Without the help of Pablo Prieto and Doug Allen, the journey to the site would have been nigh impossible. Thanks to the use of their boat, the journey to the site was made possible on a daily basis. Fransico Lineares was indispensable as my machetero and as my guide in the jungle. I am grateful to the Department of Geological Sciences at Florida International University for use of their facilities, both FCAem (Florida Center for Analytical Electron Microscopy) and CeSMEC (Center for the Study of Matter at Extreme Conditions), and for the enormous hospitality they showed me while I visited. I would like to thank the chairman of the FIU Geology Department Dr. Gautum Sen for open access to their facilities, Dr. Florintine Maurosse for his expertise and especially for the impatites he donated to me, Thomas H. Beasley for all things pertaining to the probe and SEM, Shantanu Keshav for his relentless interest and dedication to my project John Sowerby for his assistance with the raman spectrometer, and finally, Zac Atlas and Sedelia Durand for their support and friendship. I would like to send out a special thanks to the Holiday Cafe and to its friendly and supportive staff. I am grateful to them for the multiple doses of caffeine and hilarity they supplied me. I thank them for not ejecting me from their facilities for loitering and writing 99.99% of my thesis plugged into their outlet. Lastly, I would like to acknowledge the Sigma Xi Honor Society and the Geological society of America ( GSA ), including the southeastern section of GSA ( SE-GSA ), of whom generously contributed funding to the analytical techniques that led to the success of this project.

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ABSTRACT The Gatun Structure (N 09 05 58.1, W 79 47 21.8, situated in the triple-canopy rainforest 10 km to the WSW of the Gamboa and about 2 km south of the Isle of Barbacoas, Republic de Panama), is a partially inundated, quasi-concentric surface feature ~3km in diameter, which appears in aerial photographs and in radar imagery as an arcuate chain of islands with a raised center. Although the structure has been heavily weathered and altered, it has retained morphology consistent with complex craters: an elevated circular central uplift 500-600 m in diameter and approximately 70 m high, and arcuate boundary ridges (a rim structure?) ranging from ~50-110 meters high. Within the central peak, highly altered and fractured siltstone of the Gatuncillo Formation (?) (Eocene) older rocks are uplifted and exposed through surrounding calcareous units of the Caimito Formation (Oligocene) and the Las Cascadas Formation (Miocene), the major target rocks in the region. Lithologies in the structure include highly fractured siliciclastic rocks (siltstone, sandstones and greywackes), limestones with anomalous spherical glass inclusions, both black and white hypocrystalline glasses (possible melt rocks), lithic fragmental breccias, and melt-bearing breccias (possible impact melt breccias and suevites) containing flow banding and evidence for selective melting of minerals. Three types of spherules (glass, fluid-drop and lithic), a pyroxenequartz necklace disequilibrium structure (coronas), plagioclase feldspars exhibiting mosaicism and partially amorphization and zeolitization, possible liquid immiscibility between melts of calcite and felpspathic glass, as well as decomposition of titano-magnetite, are all petrographic

PAGE 8

criteria that suggest a hypervelocity impact event. The structure is crosscut by numerous dikes of unshocked basalt and basaltic andesite related to volcanism along the Panamanian segment of the Central American arc to the south. However, the lithologies of the Gatun Structure are chemically inconsistent with the regional volcanic rocks and the unshocked volcanic rocks that crosscut the structure. An impact origin is our preferred interpretation for the Gatun structure due to the lack of an igneous relationship between the Gatun structure and the explosive volcanism of Panamanian arc, the presence of classical impactite lithologies within the site, the occurrence of spherules, maskelynite (as suggested by Raman Spectroscopy) and other disequilibrium shock features in the Gatun suite of rocks.

PAGE 9

INTRODUCTION Brecciated rocks can be formed by landslides, tectonic movements, volcanic processes, contact and / or regional metamorphism, or fracturing due to hydrothermal fluid injection, as well as due to a catastrophic, hypervelocity collision of an asteroid or comet. Breccias occur in a variety of geologic settings, which means that breccias per se are not diagnostic of a hypervelocity impact event. However, several different varieties of breccias are always associated with impact sites, because there is a certain degree of overlap between shock deformation, which is purely impact generated, and tectonic and hydrothermal alteration events associated with the subsequent modification of the initial, transient crater. Purely impact generated materials are often altered by tectonic settling and / or hydrothermal modification of the initial crater, creating breccias with a tectonic or hydrothermal overprint. Differentiating between the different types of breccias in such a setting can virtually be impossible. To prove an impact origin for any site, disturbed lithologies must be compared with the locally undisturbed country rocks. Within the disturbed lithologies of an impact site there must be evidence of transient, high-temperature and pressure effects (shock metamorphism). In addition, there may be chemical contamination of the target rocks by elements that are relatively abundant in extraterrestrial materials (i.e., iridium and / or other platinum group elements [PGEs]), but relatively depleted in terrestrial crustal rocks. The occurrence of breccias that include both glass fragments, spherules, and phases with indicators of flow and plastic deformation, have been found within a circular feature near the Panama Canal--the Gatun structure. A confined circular feature (approximately 2.2-3 km in diameter) that includes

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such a complex and diverse suite of rocks merits an investigation as the site of a possible meteor impact. The purpose of this study is to ascertain the origins of the Gatun Structure, its relationship to the regional geology, and specifically to test the hypothesis of an impact origin, based on both detailed field examination of the site, and through macroand micro-scale sample analysis utilizing petrographic, electron microprobe (EMP), geochemical and Raman spectroscopic techniques.

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GEOLOGICAL SUMMARY AND PAST STUDIES The Gatun Structure is roughly 2.2 3 km in diameter, and is centered at N 09 05' 58.1", W 79 47' 21.8" in the central region of the Isthmus of Panama. It is approximately 10 km to the WSW of the Gamboa and about 2 km south of the Isle of Barbacoas ( Figure 1 ). The structure is partially inundated on the northwest side, giving it a quasi-circular surface expression that is clearly distinguishable from above, but not as obvious at ground level. Although the structure is heavily eroded and weathered, it still preserves a morphology suggestive of a complex crater: it has an elevated circular central feature approximately 500-600 m in diameter and 70m high ( Figure 2a-2c ; Figures 3a-d ), and arcuate boundary ridges (a rim structure?) ranging from 50110 meters above sea level, which are expressed as ridges on land, and as an arcuate chain of islands where partially submerged. These features are clearly recognizable in the contour map for the Escobal region, and also in the detailed geologic map of the Gatun Structure ( Figure 4 and 5b ). The structure was first identified in August 1972 as a circular topographic feature approximately 1-1.5 km across on the shore of one of the numerous manmade locks of the Panama Canal, Lake Gatun from Side Looking Aperture Radar (SLAR) images of central Panama. The feature was surveyed and sampled in 1990 (the P8 series of samples) and in 1995 ( 2-14-95 series ) by R. H. and J. L. Stewart, as part of a geological mapping project of the Panama Canal Zone

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region (see Figure 5a-b and the Geological Map of the Panama Canal and Vicinity by Stewart et al. 1980, in Woodring et al., 1982b ). Stewart confirmed the circular morphology, and identified a series of disrupted sedimentary and volcanic lithologies at the site, including shocked limestones, and breccias that included clasts which he described as consisting of unknown glassy material resembling chert. The Gatun structure lies behind the back-arc region of the largely dormant Panamanian Arc system. The nearest explosive volcanic edifice, El Valle, is situated > 30 km north of the center of the structure ( Defant et al., 1992 ). The bedrock in this region consists of interbedded, fossiliferous carbonates and siliciclastic carbonate rocks with intercalated pyroclastics (mostly tuffs and some agglomerates), and crosscutting dikes of basalts, basaltic andesite and andesite. Metamorphic rocks are generally not encountered in this region of Panama. Lithologies within the Gatun structure are mapped as part of the Eocene Gatuncillo Formation (mudstones, siltstones, sandstones and algal foraminiferal limestone), the Oligocene Caimito Formation (graywackes, foraminiferal limestones, agglomerates and tuffs) and the Miocene Las Cascadas Formation (agglomerate and tuff) ( Figure 5a ) ( Woodring et al., 1982b ). Stewart described the structure as perfectly circular, with an inner ring composed of brecciated debris of the Caimito Formation, mostly of fine-grained brecciated sandstones and brecciated metamorphosed carbonates that have been recemented with zeolites ( Figure 5a-b ). Overlapping this ring and further from the center are erosion-resistant, glass breccias that cap three ridges which radiate outward from the center of the structure ( Figure 5b ). The outer ring was described as brecciated the disturbed volcanic rocks of the Las Cascadas Formation (mostly tuffs). Rocks of the central feature were mapped by Stewart as Gatuncillo Fm., and consisted mainly of fractured siltstone, sandstone and greywacke. The Gatuncillo Fm.

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unconformably overlies an altered and strongly deformed volcanic basement consisting of tuffs that contain marine fossils, intruded by dioritic lavas ( Woodring et al., 1982a ).

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MAPS, AREA PHOTOS, FIGURES AND GRAPHS Major and Trace Element Data Microprobe Data CIPW Norms Figure 1 Location Map of the Gatun Structure The image of the quasi-circular structure in the upper left hand corner of the map is a 3 km by 3 km box. The location of the Gatun Structure is marked by a fading red sphere roughly at the center of the map between Panama City and Colon and off the Panama Canal. A B C

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Figure 2a A circa 1953 U.S. Naval aerial photograph of the Gatun Structure and the surrounding Panamanian countryside including the Canal Zone and the Lake Gatun area. The disturbed area is shaded slightly in red, which is roughly 3 km in diameter. The red circle marks the boundaries of the sample area. Figure 2b Satcom Radar image of the Panama Canal Zone The disturbed area is shaded slightly in red, which is roughly 3 km in diameter. Figure 2c Aerial photograph of the Gatun Structure the disturbed area is shaded slightly in red. The shaded areas is roughly 3 km in diameter. A B C D Figure 3a Northeast of the Central Uplift Figure 3b North of the Central Uplift Figure 3c East of the Central Uplift and Macho Island Figure 3d Southwest of the Central Uplift Figure 4 Contour map of the Gatun Structure and part of the Gatun Lake area. The disturbed area is shaded slightly in red. The shaded areas is roughly 3 km in diameter. (Sheet 4243 III;

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Series E762; Edition 2-DMA; Escobal; Scale 1:50,000; Interval is 20 m) Figure 5a -Geologic map (Panama Canal and Vicinity by Stewart et al. 1980, which is included in USGS Professional paper 306F; Woodring et al., 1982 ). Each square section is 10 by 10 kilometers. Figure 5b Redrawn detailed geologic map of the Gatun Structure from 1990 and 1995 field excursions given to me by Stewart. Sample locations for the P8 and 2-14-95 series are marked on the map. Each square section is 1 by 1 kilometers (Scale 1:50,000; Interval is 10 m). With a lower contour interval than the map above, a quasi-circular ridge system is better recognized on this map. Figure 6a Sample location map (clickable and linked locations) drawn and color coded contour map of the Gatun Structure and the surrounding Gatun Lake area. Each square section is 1 by 1 kilometers.

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Figure 6b Profile from A to A' and possible reconstruction of impactite locations based on the sample location map (Figure 6a). The profile is a cross-sectional cut the Gatun structure running SE-NW. Note the morphological and structural relationships between the Gatun profile and profiles from other complex structures (below Figure 6c A and B central peak and rim structures). The color coded spots beneath the structure's relief outline corresponds to lithologies that were along the profile path between A and A' prime (Above see Figure 6a), and the color coded spots above correspond to inferred lithologic occurrences within the site. These inferences are based on the occurrence of these lithologic types elsewhere in the structure at a given distance from the center and at a certain elevation within the site. The concentric and elevation related facies changes seen at the Gatun structure is consistent with most complex impact structures. Figure 6c A profile and location of impactite types within simple and complex impact structures. (A) a schematic radial cross-section a complex impact structure featuring a central uplift ( French, 1998 ) showing the location and level at which glasses (melt), melt-bearing breccias (suevite and impact-melt breccias) and lithic breccias occur within a complex impact structure. (B) A profile of the 15-km diameter Logoisk structure Belarus ( Dressler and

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Reimold, 2001 ). (C) a cross-section of a simple impact structure ( French, 1998 ). Figure 7 Raman spectra of GS-06a-00 labradorites compared to a spectra of a gem quality labradorite standard from Madagascar. The pattern in red was produced from a gem-grade labradorite standard from Madagascar. The enhanced background in the pattern is a manifestation of the unpolished and uneven surface of the labradorite standard. The two patterns from sample GS-06a-00 are in purple and blue. Patterns span from a wavenumber of 200 up to 1450. Figure 8 (TiO2 vs. FeO) Spherules from GS-06a-00 (Suevite?). A variation diagram of TiO2 vs. FeO in the glass and glass rims of the lithic (cored) spherules found in sample GS-06a-00, which is designated as a possible impact suevite. The source for the data for the spherules came from microprobe analysis and Energy Dispersive X-ray Spectroscopy (EDS). Mineral compositions for magnetite and ilmenite are provided from the microprobe and the text: The Rock-Forming Minerals ( Deer et al., 1993 )

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Figure 9 (SiO2 vs. FeO) The Pyroxene-Quartz Corona from sample GS-10-00. The bulk composition of GS-10-00 is plotted along with the pyroxene (diopside), brown glass, and quartz that is associated with the Pyroxene-Quartz corona reaction structure found in sample GS-1000 Figure 10 (SiO2 vs. Al2O3) Glasses, Breccias, and Volcanics of the Gatun Structure and the Surrounding Country Rock. A Harker diagram of the variations of silica vs. Al2O3 in the glasses and melt-bearing breccias, lithic breccias, suevites?, volcanics, the siliceous component in the shocked carbonate (the melt blebs? in GS-30-00) and the microprobe data for the spherules contained in GS-06a-00 (Suevite?), the white glass, the white-spotted gray glass and the black glasses in the glass breccias. Mineral and phase compositions included are from microprobe analysis of minerals in the Gatun samples, microprobe standards, and from the text: The RockForming Minerals ( Deer et al., 1993 ) Figure 11 (SiO2 vs. CaO) Glasses, Breccias, and Volcanics of the Gatun Structure and the Surrounding Country Rock. A Harker diagram of the variations of silica vs. CaO in the glasses and melt-bearing breccias, lithic breccias, suevites?, volcanics and the microprobe data for the spherules contained in GS-06a-00 (Suevite?) and the black glasses in the glass breccias. Mineral and phase compositions included are from microprobe analysis of minerals in the

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Gatun samples, microprobe standards, and from the text: The Rock-Forming Minerals ( Deer et al., 1993 ) Figure 12 (K2O vs. Na2O) Glasses, Breccias, and Volcanics of the Gatun Structure and the Surrounding Country Rock. A variation diagram of K2O vs. Na2O in the glasses and meltbearing breccias, lithic breccias, suevites?, volcanics and the microprobe data for the spherules contained in GS-06a-00 (Suevite?) and a black glass fragment found in the weathered breccia GS-08-00, which is similar in chemistry and appearance to the black glass fragments found in the glass breccias. Figure 13a K2O-CaO-Na2O ternary of the Carbonates, Glasses, Breccias, and Volcanics of the Gatun Structure and the Surrounding Country Rock. Figure 13b AFM diagram of the Carbonates, Glasses, Breccias, and Volcanics of the Gatun Structure and the Surrounding Country Rock.

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Figure 14 (CaO vs. TiO2) Carbonates of the Gatun Structure and the Surrounding Country Rock. A variation diagram of CaO vs. TiO2 in the Gatun structure carbonates and the country rock carbonates, which includes three samples of undisturbed Caimito Fm., a limestone and two tuffaceous limestones from outside of the structure. Mineral compositions included are from microprobe analysis of minerals in the Gatun samples (calcite). Major and Trace Element Data Microprobe Data CIPW Norms

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APPENDIX B: TABLE 16a and 16b MAJOR AND TRACE ELEMENT DATA Microprobe Data CIPW Norms Maps, Area Photos, Figures and Graphs Table 16a Majors and Traces View Major and Trace Elements in XLS format SUEVITES SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TOTAL ALKALIS TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) GS-06a-00 62.31 0.82 16.1 7.395 0.224 2.37 6.95 1.16 2.33 3.49 99.699 19.445 602.32 492.735 31.953 22.276 44.719 125.78 70.40871 49.96893 25.5869 GS-11-00 59.64 0.93 17 7.24 0.216 2.69 4.25 4 4.65 8.65 100.62 6.8134 505.75 1936.63 25.003 30.526 31.784 222.85 122.1175 63.71494 29.2365 GLASS AND MELT BRECCIAS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) GS-01-00 79.88 0.65 6.57 7.838 0.162 0.16 0.81 1.55 3.03 4.58 100.5 11.339 328.35 831.599 7.3069 4.77506 2.9727 22.53 27.14087 2.706463 n/a GS-03-00 78.03 0.56 8.21 8.087 0.08 0.08 1.64 2.05 2.11 4.16 100.78 7.1865 316.85 776.824 4.8217 7.57587 3.8987 34.678 46.23047 7.208194 n/a GS-25-00 75.19 0.82 12.3 3.222 0.108 0.11 2.47 3.1 3.23 6.32 100.44 3.5352 417.04 1131.4 6.0908 8.40235 2.4049 40.131 56.60396 8.061989 n/a 2-14-95-4 78.12 0.75 11 2.034 0.113 0.11 2.07 3.06 2.96 6.02 100.08 2.5545 285.63 814.168 4.7312 6.4929 3.6489 27.985 34.1074 4.708266 n/a 2-14-95-5 78.24 0.47 8.84 6.889 0.215 0.21 1.29 2.64 2.31 4.95 100.89 10.669 232.84 701.98 6.292 4.17696 3.36 30.229 41.6985 6.750715 n/a P8-2-4-90 76.75 0.6 12.8 1.551 0.257 0.26 1.98 3.97 3 6.98 100.94 2.587 204.64 896.31 3.1402 7.85298 1.93 131.19 29.52844 7.703081 n/a GS-22-00 70.71 0.93 14.9 3.751 0.378 0.38 2.46 3.57 3.28 6.85 100.07 4.2286 257.76 1222.7 12.993 14.4305 10.237 62.639 100.8164 19.56027 20.9168 GS-08-00 69.57 1.49 20.9 6.627 0.33 0.33 0.23 0.72 0.86 1.58 100.8 11.924 59.384 403.575 8.0044 12.5994 6.1821 64.115 52.06479 26.9512 n/a GLASSES SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) GS-13-00 70.46 0.53 14 3.035 0.083 0.69 1.93 4.03 4.48 8.51 99.242 1.6499 162.7 1134.04 6.151 7.58575 8.6433 37.163 70.80135 27.65482 54.9709 GS-23-00 73.24 0.77 13.6 3.098 0.085 0.31 2.25 3.69 2.89 6.59 99.907 3.3316 255.11 957.105 8.5541 3.999 8.9168 25.235 82.24756 24.64788 92.9752 GS-15-00 72.77 0.67 13.8 4.009 0.051 0.15 2.01 3.16 3.1 6.26 99.681 4.3804 182.43 953.735 27.466 12.2387 32.367 n/a 32.32627 20.54235 n/a GS-17-00 68.36 0.91 16.2 2.937 0.012 0.22 3.41 4.32 3.63 7.94 99.971 2.3579 295.54 1041.8 12.111 15.8553 6.2184 1210.2 52.61994 26.21558 n/a GS-06-00 78.6 0.21 12.7 1.324 0.016 0.09 0.98 3.25 2.75 6 99.911 4.9156 237.02 1285.93 23.742 2.8315 11.174 11.044 6.540603 10.78065 n/a GS-21-00 69.46 .903 17.44 4.393 0.031 .031 2.971 3.258 .592 1.505 100.56 2.8691 3482 1469.317 8.96839 11.6217 17.8009 156.83 78.609639 39.786764 77.56736 LITHIC BRECCIAS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) GS-14-00 63.62 0.57 18.9 5.224 0.206 0.26 6.51 3.54 2 5.55 100.79 5.8138 515.68 1244.38 31.282 23.2794 98.745 156.52 81.21454 33.7838 27.1049 GS-18-00 62.59 0.54 19.9 5.469 0.313 0.31 7.04 4.07 0.33 4.4 100.38 5.3147 713.08 948.777 33.62 22.1149 112.02 169.05 75.82371 66.23253 29.888

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GS-18a-00 66.16 0.52 18 5.14 0.174 0.17 5.02 3.79 1.54 5.34 100.45 1.9886 588.69 915.558 22.374 15.8584 90.428 115.76 52.38175 67.4587 25.5679 VOLCANICS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) GS-04-00 63.73 0.88 18.9 8.369 0.243 1.37 2.51 2.18 2.76 4.95 100.91 9.9739 351.24 1501.67 20.259 21.6948 20.086 128.4 111.7157 47.0322 21.3148 *GS-05-00 25.41 0.13 5.26 1.573 0.084 1.88 65.1 0.21 0.41 0.62 100.03 5.7685 1903.7 91.7797 25.473 47.2814 59.066 75.176 116.293 40.57055 99.9638 9-5a-86 59.83 0.94 17.4 7.811 0.246 1.96 5.1 4.14 2.23 6.37 99.674 2.2882 403.46 1328.59 18.849 18.4074 20.109 133.44 115.1922 19.96043 24.0321 27-3a-86 61.15 0.68 18.1 6.476 0.13 1.84 7.22 2.45 1.7 4.15 99.749 2.8902 682.33 776.791 27.22 21.6447 35.312 134.62 88.60111 53.20892 23.9425 8-1-86 55.84 1.33 16.8 10.36 0.164 4.7 4.94 4.7 1.52 6.22 100.39 11.248 522.51 643.865 15.713 15.7059 38.211 268.56 106.2402 98.58687 46.953 P8-2-1-90 56.1 1.2 17.1 10.83 0.438 2.9 6.11 4.04 0.98 5.01 99.738 6.27 488.98 453.768 16.035 28.0861 18.373 279.37 124.7627 65.75592 23.0952 GS-07-00 59.73 1.07 16.8 7.762 0.254 2.47 6.73 3.6 1.73 5.34 100.2 4.2927 463.9 827.422 9.8821 13.5187 15.794 166.4 97.87933 59.58542 40.8893 GS-08a-00 52.09 0.99 19.4 9.63 0.146 4.78 10.5 2.7 0.68 3.38 100.96 3.7887 465 348.955 27.275 26.7121 88.243 302.73 98.83382 94.21109 71.2829 GS-10-00 50.51 0.72 14.6 10.07 0.158 8.48 12.6 1.95 0.93 2.88 100.07 4.7413 901.29 463.2 36.957 32.0076 280.58 285.24 97.88761 127.0395 77.3419 GS-13a-00 50.38 0.68 13.5 10.89 0.161 9.13 12.8 2.12 1.21 3.33 100.87 2.2014 775.65 625.24 39.196 22.4796 317.2 235.59 101.7392 112.2927 65.4625 GS-27-00 51.21 0.75 13.7 10.23 0.198 8.45 12.5 2.1 1.16 3.26 100.32 3.6346 785.81 542.453 37.642 21.0391 302.49 234.09 104.9422 105.0611 65.5844 P8-2-6-90 50.79 0.99 17.3 9.991 0.2 6.19 10.1 2.93 0.79 3.72 99.34 3.4168 411.14 355.838 37.986 21.4983 129.94 256.2 105.6682 87.93796 97.5784 GS-20-00 64.23 0.98 16.1 6.208 0.153 1.56 4.59 4.05 2.24 6.3 100.08 1.1273 328.63 1161.2 16.605 22.7378 13.584 109.22 93.71014 25.67566 29.0216 SANDSTONES AND TUFFACEOUS ROCKS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) P8-2-2-90 79 0.13 14 0.714 0.015 0.12 0.6 3.39 2.97 6.36 100.91 3.6649 139.46 735.039 3.1626 n/a 2.2772 n/a n/a n/a n/a GS-09-00 69.74 0.79 15.4 3.595 0.046 0.16 1.66 5.75 3.38 9.14 100.52 1.4731 209.12 848.217 n/a 3.93129 n/a 266.92 10.19969 n/a n/a GS-24-00 94.76 0 0.01 4.888 0.008 0.01 0.01 0 0.04 0.04 99.728 12.002 n/a 1.63257 5.8205 4.95131 14.98 15.536 33.18849 12.57063 n/a GS-26-00 78.42 0.14 17.9 1.258 0.016 0.08 0.1 0.28 1.15 1.44 99.302 1.2819 31.002 198.149 5.7298 1.23284 1.9464 4.8002 16.54278 3.28477 n/a GS-12-00 79.24 0.14 14 0.94 0.018 0.11 0.43 2.67 2.36 5.03 99.933 11.211 87.858 587.041 5.4081 4.73161 1.8335 10.734 40.19305 9.74364 13.1841 GS-28-00 66.53 1.47 25.1 6.31 0.031 0.44 0.19 0.22 0.42 0.64 100.73 14.898 34.523 276.818 20.396 24.2708 20.264 177.37 88.19973 22.41814 10.8122 CARBONATES SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) GS-19-00 39.04 2.22 9.83 4.378 0.089 1.54 25.1 4.1 1.68 5.78 87.942 6.9098 1468.2 563.349 29.289 2.94137 28.857 137.26 137.7412 46.47484 6.6002 GS-29-00 30.4 1.65 5.67 2.45 0.251 0.36 37.9 0.29 0.93 1.22 79.913 5.5936 1196.8 199.614 25.224 3.06849 19 98.722 77.89552 43.12349 6.13302 P8-2-5-90 19.2 1.45 5.79 1.929 0.277 0.85 42.3 0.38 0.29 0.67 72.447 14.761 1117.5 124.639 22.266 3.22648 23.675 119.59 75.67031 31.20035 5.93907 GS-30-00 22.73 2.11 7.04 5.168 0.62 6.3 41.9 0.06 0.06 0.12 85.954 25.314 1344.7 100.166 41.048 3.78659 40.445 148.4 105.7599 48.51713 7.77073 P8-2-7-90 11.97 1.32 4.97 5.559 0.624 8.71 47.9 0.01 0.06 0.07 81.154 5.7685 1191.9 121.703 30.249 3.65014 27.601 107.47 104.6703 43.81959 7.69506 Country Rock Carbonates SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) CR LS 0 0.13 0.76 0.304 0.013 0.92 67.8 0.03 0.06 0.09 70.044 23.229 1931.6 17.0471 26.455 4.16886 23.602 65.82 58.59068 27.51308 7.39819 Caimito Core 43.14 0.57 9.52 4.59 0.123 1.58 24.6 2.55 1.32 3.87 88.022 3.3664 720.02 408.559 42.16 26.9627 59.543 108.3 117.7176 31.90345 n/a Und. Caimito 17.07 0.08 1.96 0.989 0.058 1.12 49.2 0.22 0.37 0.58 71.035 20.321 1248.2 66.2207 46.71 28.6662 61.747 121.82 72.73461 27.0061 n/a

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Table 16b Majors and Traces AVERAGES SUEVITES SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TOTAL ALKALIS TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 60.97 0.875 16.57 7.318 0.22 2.533 5.597 2.58 3.489 6.068 100.16 13.13 554.0382 1214.68 28.4781 26.401 38.2513 174.32 96.2631 56.8419 27.41171 GLASS AND MELT BRECCIAS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 76.7 0.681 10.66 4.767 0.019 0.188 1.819 2.848 2.845 5.693 100.53 6.014 291.8741 910.712 6.48224 7.67238 4.06452 49.911 48.018 8.09985 20.91678 GLASSES SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 72.15 0.665 14.61 3.133 0.046 0.738 2.305 3.172 3.061 6.233 99.878 3.251 769.1768 1140.32 14.4987 9.02199 14.1867 136.92 53.8576 24.938 75.17117 LITHIC BRECCIAS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 64.12 0.541 18.92 5.278 0.147 0.249 6.192 3.802 1.292 5.094 100.54 4.372 605.8158 1036.24 29.0918 20.4176 100.399 147.11 69.8067 55.825 27.52028 VOLCANICS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 54.76 0.935 16.5 9.406 0.21 5.09 8.867 3.073 1.293 4.366 100.13 4.477 590.0054 636.612 26.6755 22.1099 124.626 229.62 104.175 82.364 53.61622 SANDSTONES AND TUFFACEOUS ROCKS SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 77.95 0.445 14.4 2.951 0.022 0.153 0.499 2.053 1.722 3.775 100.19 7.422 100.3928 441.149 8.10341 7.82356 8.26027 95.071 37.6647 12.0043 11.99814 CARBONATES SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 24.67 1.75 6.661 3.897 0.372 3.552 39.01 0.968 0.605 1.573 81.482 11.67 1263.8 221.894 29.6153 3.33461 27.9157 122.29 100.347 42.6271 6.827616 Country Rock Carbonates SiO2 TiO2 Al2O3 Fe Total MnO MgO CaO Na2O K2O TA TOTAL LOI Sr (ppm) Ba (ppm) Ni (ppm) Sc (ppm) Cr (ppm) V (ppm) Zn (ppm) Cu (ppm) Co (ppm) 20.07 0.26 4.083 1.961 0.064 1.205 47.21 0.931 0.582 1.513 76.367 15.64 1299.963 163.942 38.4414 19.9326 48.2974 98.646 83.0143 28.8075 7.398193

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Major and Trace Element Data Microprobe Data Maps, Area Photos, Figures and Graphs

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APPENDIX B: Tables 1-15 Microprobe Data Major and Trace Element Data CIPW Norms Maps, Area Photos, Figures and Graphs View all the microprobe Data in one workbook (Tables 1-15) in XLS format Table 1 Some Standards contains spot analyses of microprobe standards APATITE, DOLOMITE, AN65 PLAG, QUARTZ, and MARCASITE. Table 2 GS0600 White Glass : contains analyses of the hypocrystalline glass matrix (White Glass), the phenocrysts of Plagioclase (andesine), amorphous glassy areas (quartz glass lechatlierite?), an altered feldspar (now kaolinite) and the dominant opaque in the white glass, pyrite. The hypocrystalline glass matrix was analyzed to ascertain its average composition, which compares quite well to the bulk composition of the whole rock. The white glass mesostasis appears to consist of fused quartz and Na-rich feldspars and clays. The presence of the clays and the pyrite indicate that this sample may have been subsequently altered after it had formed.

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Table 3, 4a and 4b GS06a00 Suevite : Table 3contains analyses on several spherules, including analyses of several volatile elements (CO2, SO3 and Cl). Petrographic observations indicate that spherules rims and the brown siliceous glass matrix in sample GS-06a-00 appear to be similar in composition. X-ray maps (2-SL thru 2-K) and microprobe analyses reveal that the composition of the spherule rims are Fe, Mg, and Ti-rich (with minor Mn) aluminous silicate glass. Spherule totals are not 100%, which is likely to be the result of post-formation hydrothermal alteration, or volatilization caused by the beam, a common issue with analyses of glassy phases. Table 4a contains analyses of a full transect across a lithic spherule, the interior of another lithic spherule, augite, titano-magnetite / ulvospinel and an apatite. The interior of the lithic spherules appears to be clay derived from plagioclase feldspar, possibly the labradorite occurring in sample GS-06a-00. Table 4b contains analyses from three different areas (glass, crystalline, and melt) associated with the maskelynite grain seen in plate 4.17 and in X-ray maps 4.1-Al to 4.1-K By comparing these three areas, several observations can be made concerning the movements of the primary elements in feldspars: Si, Al, Ca, Na and K. Si is relatively enriched in the melt and slightly more enriched in the glass (maskelynite). Al appears to be most enriched in the crystalline feldspar, slightly depleted in the glassy areas and even more depleted in the melt. The greatest contrasts are in Ca and Na. The crystalline areas correspond to an An 65 feldspar (labradorite), while the maskelynite appears to be completely depleted in Ca and enriched in Na. The melt is Ca enriched with some K. Na remains behind either in the crystalline material, in the glass, or both. Table 5 GS0800 Weathered Breccia : contains analyses on two unaltered hypocrystalline glass inclusions, a euhedral apatite, and a still undetermined yellowish-orange opaque mineral in the weathered breccia GS-08-00 The data indicate that the glass inclusions ( plates 5.5-10 ) are rather heterogeneous in composition but the average composition of these glasses correspond quite well to the glass breccias in bulk composition.

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Table 6 GS1000 Pyroxene-quartz corona : Analyses of the brown glass (dark and light regions, see plates 7.13-24 ) between quartz cores and pyroxene coronas of the Pyroxene-Quartz corona; a quartz-to-glass transect that shows the sharp chemical contrast between quartz and glass; and the pyroxene that makes up the coronas (diopside) in basalt GS-10-00 Table 7 GS1300 Porphyritic Glass : contains data pertaining to the flow-banded porphyritic glass GS-13-00. Analyses of the matrix material, which is similar in composition the average bulk chemistry of the glass breccias and the individual black glass fragments. The major opaque minerals appears to be magnetite / ulvspinel. Table 8 GS1400 Lithic Breccia : Analyses of various phases contained in the lithic fragmental breccia GS-14-00 Analyses of altered amphiboles, a magnetite grain and quartz. Analysis of a amphibole that had been replaced by carbonates and another black amorphous phase. The black amorphous material does not seem to conform with any amphibole composition this researcher is familiar with. It consists of Fe and Na with almost 1 wt % of Ca and Al substituting for Si. The bulk chemistry is more consistent with altered feldspars than with amphiboles, but the remnant 60-120 cleavages attests to amphibole as the original mineral. The carbonate replacing the amphiboles is a relatively pure calcite. The dominant opaque phase in this sample and the other altered igneous rocks (GS-18-00 and GS-18a-00) is magnetite, which contains exsolved ilmenite, and the dominant plagioclase is andesine. Table 9 GS1500 White Spotted Gray Glass : Contains analyses pertaining to the white-spotted gray glasses GS-15-00 and GS-17-00 This glass also bears similarities with the Glass breccias with differences in Al, Fe and Ti. Unlike the white glass, the white-spotted gray glass contains magnetite/ulvospinel as the primary opaque. A plagioclase feldspar (andesine) with planar fractures (tensional cracks?) was observed and analyzed in GS-15-00 ( plates 11.12-16 ). The

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analyses of the phases contained in the fractures reveal them to be clays (probably kaolinite). Fe-rich, euhedral apatites are common as accessory phases in this sample ( plates 11.17 and 11.18 ). Table 10 GS1800 Gray Andesite and Table 11GS18a00 Red Andesite : contain data pertaining to the altered igneous rocks GS-18-00 and GS-18a-00 which may be the source of the clasts in the lithic breccia, GS-14-00. Analyses for the kinked biotite seen in the altered gray igneous rock GS-18-00 ( plates 10.23-25 ). The matrices of these two samples are similar, consisting of mainly of feldspars, quartz and carbonates. Analyses of the dominant matrix phase in GS-18-00, ostensibly quartz, yields 85% SiO2 with as much as 9.41 % Al2O3 and 3.05% Na. Matrix carbonates in the GS-18a-00 sample appears to be pure calcite, while carbonates in GS-18-00 are more Fe and Mn-rich. Fe and Mn-rich calcite also occurs as a replacement phase in amphiboles of GS-18-00 ( plates 10.13-14 and 10.19-20 ). The plagioclases in both samples are andesine, and the major oxide is titanomagnetite. Euhedral apatite crystals are observed as inclusions in the altered igneous rocks ( plates 10.19 and 10.20 ). Microprobe and EDS results reveal that the opaque amphiboles seen in samples GS-1400, GS-18-00 and GS-18a-00 are variable in composition at the m scale. The compositions seen in altered amphiboles match alkali and plagioclase feldspar, various Fe-Ti oxides, carbonates and occasionally apatites. EDS scans reveal that some of these areas are have high Mn and S. Table 12 GS1900 Silicate/Carbonate rock : Analyses of zeolites, carbonates and pyrite from the silicate / carbonate rock GS-19-00 The zeolites occur in a vein that intrudes both the silicate and carbonate side of the contact ( plates 13.6 and 13.7 ). The zeolites deeper in the silicate portion are rich in Na while those in the carbonate region are rich in Ca. The sodium-rich zeolite is analcime and the calcium-rich zeolite is likely to be heulandite. The zeolite vein quickly

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transforms into calcite as it crosses into the carbonate region. Opaque phases were confirmed as pyrite. Table 13 GS2200 Green and Beige Melt Breccia : Analyses of selected features in GS-22-00 Analyses across a fossil-like cavity fill ( plates 15.16-20 ) revealed the infill material to be chalcedony; analysis of a greenish, rhombohedral inclusion in the chalcedony revealed it to be a Fe, Mn, K aluminous silicate, and the surrounding greenish, amorphous material to be Fe-rich silicate (glass?). Analyses across the cavity fill in plates 15.21 and 15.22 revealed a composition consistent with kaolinite but with significant amounts of Fe, Ca, and Mn. Some odd yellowish-orange inclusions in a cavity fill ( plates 15.23 and 15.24 ) and adjacent to several euhedral apatites, may once have been sphenes, judging by the SiO2 and TiO2 content: if they were, they are now heavily depleted in Ca and enriched in Al and Fe. The dominant feldspar in this sample is Andesine, with inclusions of Na-bearing orthoclase. A swath of plastically deformed, granular material (a deformed siltstone clast ? plates 15.9-14 ) is rich in quartz with traces of Al, Ca, and Na. The most intriguing features are abundant clots of reddish-brown material found in some of the most intensely deformed clasts and throughout the matrix ( plates 15.9-14 ). Secondary light and backscatter imaging reveals these globules to be distinct features both morphologically and chemically ( plates 15.25-28 ). X-ray mapping of a chondrule-like feature and some of the "blebs" demonstrate a chemical distinction between the features ( plates 15.1-Si to 15.1-Fe and 15.2-Si to 15.2-Fe ). The chondrule-like feature appears to be a unmixing (?) spinel that exhibits two chemically distinct areas, one rich in Ti and Fe, and the other rich in Si and Al. Analysis of a Siand Alrich area shows the presence significant Ti and Fe, 8.79 wt.% and 7.03 wt. % respectively. Analysis of the most Ti and Fe rich areas in the chondrule-like feature demonstrates that some Si and Al has remained in these areas, 7.27 wt. % and 2.74 wt.% respectively. The Fe-rich bleb (white plate 15.25 ) that contains the chondrule-like feature

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(black and white) was also analyzed, as well as the silica rich (dark gray) rim of the feature. The Fe-rich bleb is likely to be hematite based on its chemistry and appearance in thin section (reddish). The silica-rich rim approximates quartz, but like the quartz seen in the recrystallized matrix of the gray igneous rock GS-18-00, its high in Al ( 6.32 wt. %) and has significant quantities of Na and K (1.69 and 1.21 wt % respectively). The edge of the silica-rich rim appears to have a composition consistent with an Na-bearing orthoclase. Table 14 GS2500 Glass breccia : Analyses of a black glass clast and a devitrified clast in glass breccia GS-25-00 The black glass clasts are Fe-rich feldspathic glass with an average TiOs of 0.7%. The devitrified clast (plates 1.25 and 1.26) is similar to the black clast in composition, but contains quartz-rich areas (the devitrified areas) and areas that are still glass. The TiO2 content of this clast is as high as 9.78 wt. %. Table 15 GS3000 Shocked Carbonate : Analyses of the glassy and amorphous blebs contained in the shocked carbonate GS-30-00 Although abundant, not all blebs appeared homogenous in backscatter images. The most homogenous appearing blebs (ones showing mainly one shade of gray) were chosen for analysis. The glassy and amorphous blebs are very rich in Si, Mg and Al, and contain signficiant amounts of Fe, Ca, and Mn. Major and Trace Element Data Microprobe Data Maps, Area Photos, Figures and Graphs

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APPENDIX B: Table 17 CIPW NORMS AND IUGS-TAS CLASSIFICATION Major and Trace Element Data Microprobe Data Maps, Area Photos, Figures and Graphs Sample Number: GS0100 (Glass Breccia) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 53.2867 orthoclase 17.8174 plagioclase 15.0606 (albite) (13.0506) (anorthite) (2.0100)

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diopside 1.7611 (wollastonite) (0.8303) (enstatite) (0.0388) (ferrosilite) (0.8920) Hypersthene 8.5838 (enstatite) (0.3578) (ferrosilite) (8.2260) magnetite 2.2622 ilmenite 1.2284 TOTAL 100.0002 Sample Number: GS2500 (Glass Breccia Fused) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 38.4796 orthoclase 19.0881 plagioclase 36.3377 (albite) (26.2312) (anorthite) (10.1065) diopside 1.8879

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(wollastonite) (0.8965) (enstatite) (0.0854) (ferrosilite) (0.906) Hypersthene 2.19 (enstatite) (0.1886) (ferrosilite) (2.0014) magnetite 0.9337 ilmenite 1.5574 TOTAL 100.4744 Sample Number: GS0400 (Porphyritic Andesite possible impact melt rock) IUGS TAS Name: High-K Dacite Mineral Wt Norm quartz 28.5595 corundum 7.7626 orthoclase 16.3106 plagioclase 30.8986 (albite) (18.4465) (anorthite) (12.4521) hypersthene 13.3074

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(enstatite) (3.4123) (ferrosilite) (9.8951) magnetite 2.4271 ilmenite 1.6713 TOTAL 100.9371 Sample Number: GS0600 (White Glass) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 46.2914 corundum 2.5949 orthoclase 16.2515 plagioclase 32.3623 (albite) (27.5005) (anorthite) (4.8618) hypersthene 1.6421 (enstatite) (0.2242) (ferrosilite) (1.4180) magnetite 0.3842 ilmenite 0.3988

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TOTAL 99.9252 Sample Number: GS06a00 (Suevite) IUGS TAS Name: High-K Andesite Mineral Wt Norm quartz 21.7265 orthoclase 19.4427 plagioclase 38.9581 (albite) (9.8156) (anorthite) (29.1425) diopside 4.4739 (wollastonite) (2.2282) (enstatite) (0.9065) (ferosillite) (1.3392) hypersthene 12.3780 (enstatite) (4.9966) (ferrosilite) (7.3814) magnetite 2.1444 ilmenite 1.5384 TOTAL 100.662

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Glass spherules contained in GS06a00 IUGS TAS Name: Leucitite Mineral Wt Norm quartz 0.9212 orthoclase 3.9817 plagioclase 23.8865 (albite) (7.6372) (anorthite) (16.2493) diopside 3.8558 (wollastonite) (1.9199) (enstatite) (0.7782) (ferosillite) (1.1577) hypersthene 40.0715 (enstatite) (16.1084) (ferrosilite) (23.9630) magnetite 8.7513 ilmenite 18.0746 apatite 0.4954 TOTAL 100.038

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Sample Number: GS0700 (Andesite) IUGS TAS Name: Medium-K Andesite Mineral Wt Norm quartz 11.9364 orthoclase 10.2092 plagioclase 54.9550 (albite) (30.4189) (anorthite) (24.5361) diopside 7.3736 (wollastonite) (3.6760) (enstatite) (1.5194) (ferrosilite) (2.1782) hypersthene 11.2527 (enstatite) (4.6240) (ferrosilite) (6.6287) magnetite 2.2471 ilmenite 2.0293 TOTAL 100.0033 Sample Number: GS08a00 (Basaltic andesite)

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IUGS TAS Name: Medium-K Basalt Mineral Wt Norm quartz 1.9081 orthoclase 3.9879 plagioclase 61.0898 (albite) (22.6390) (anorthite) (38.4508) diopside 10.8709 (wollastonite) (5.4975) (enstatite) (2.7697) (ferrosilite) (2.6037) hypersthene 17.5151 (enstatite) (9.0280) (ferrosilite) (8.4871) magnetite 2.7671 ilmenite 1.8631 TOTAL 100.002 Sample Number: GS1000 (Basalt) IUGS TAS Name: Medium-K Basalt

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Mineral Wt Norm orthoclase 5.4946 plagioclase 44.8265 (albite) (16.4962) (anorthite) (28.3303) diopside 27.7770 (wollastonite) (14.2643) (enstatite) (8.5539) (ferrosilite) (4.9588) hypersthene 11.6805 (enstatite) (7.3941) (ferrosilite) (4.2864) olivine 5.9356 (forsterite) (3.6217) (fayalite) (2.3139) magnetite 2.9208 ilmenite 1.3671 TOTAL 100.0021 Sample Number: GS1100 (Suevite/Melt breccia?) IUGS TAS Name: Trachyandesite

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Mineral Wt Norm quartz 3.0365 orthoclase 27.3110 plagioclase 48.2455 (albite) (33.6389) (anorthite) (14.6066) diopside 5.2907 (wollastonite) (2.6506) (enstatite) (1.1785) (ferrosilite) (1.4616 ) hypersthene 12.2773 (enstatite) (5.4805) (ferrosilite) (6.7968 ) magnetite 2.0866 ilmenite 1.7554 TOTAL 100.003 Sample Number: GS1300 (Porphyritic Black Glass) IUGS TAS Name: High-K Rhyolite

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Mineral Wt Norm quartz 21.8183 orthoclase 26.6787 plagioclase 41.2943 (albite) (34.3628) (anorthite) (6.9315) diopside 2.2961 (wollastonite) (1.1344) (enstatite) (0.4031) (ferrosilite) (0.7586) hypersthene 3.8293 (enstatite) (1.3287) (ferrosilite) 2.5006 magnetite 0.8869 ilmenite 1.0143 TOTAL 100.3185 Sample Number: GS13a00 and GS2700 (Basalt) IUGS TAS Name: Medium-K Basalt Mineral Wt Norm orthoclase 7.0892

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plagioclase 41.3263 (albite) (17.7846) (anorthite) (23.5417) diopside 32.0596 (wollastonite) (16.4566) (enstatite) (9.8259) (ferrosilite) (5.7771) hypersthene 1.5727 (enstatite) (0.9904) (ferrosilite) (0.5823) olivine 13.5446 (forsterite) (8.2189) (fayalite) (5.3257) magnetite 3.1293 ilmenite 1.2804 TOTAL 100.0021 Sample Number: GS1400 (Lithic Breccia) IUGS TAS Name: Medium-K Dacite Mineral Wt Norm

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quartz 18.5756 orthoclase 11.7214 plagioclase 59.2326 (albite) (29.7063) (anorthite) (29.5263) diopside 2.1975 (wollastonite) (1.0448) (enstatite) (0.1080) (ferrosilite) (1.0447) hypersthene 5.6994 (enstatite) (0.5342) (ferrosilite) (5.1652) ilmenite 1.5026 titanite 1.0736 TOTAL 100.00 Sample Number: GS1700 (White Spotted Gray Glass) IUGS TAS Name: Trachydacite Mineral Wt Norm quartz 21.2472

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orthoclase 21.4526 plagioclase 50.6262 (albite) (36.5556) (anorthite) (14.0906) diopside 2.4456 (wollastonite) (1.1803) (enstatite) (0.2396) (ferrosilite) 1.0257 hypersthene 1.6291 (enstatite) (0.3084) (ferrosilite) (1.3207) magnetite 0.8511 ilmenite 1.7283 TOTAL 101.01 Sample Number: GS1800 (Gray Andesite) IUGS TAS Name: Low-K Andesite Mineral Wt Norm quartz 19.0979 corundum 0.0472

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orthoclase 1.9431 plagioclase 69.1129 (albite) (34.3142) (anorthite) (34.7987) hypersthene 7.1980 (enstatite) (0.7693) (ferrosilite) (6.4287) magnetite 1.5804 ilmenite 1.0219 TOTAL 100.00 Sample Number: GS18a00 (Reddish Andesite) IUGS TAS Name: Medium-K Dacite Mineral Wt Norm quartz 24.4414 corundum 0.9710 orthoclase 9.1008 plagioclase 56.9740 (albite) (32.0698) (anorthite) (24.9042)

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hypersthene 6.5044 (enstatite) (0.4234) (ferrosilite) (6.0810) magnetite 1.4905 ilmenite 0.9876 TOTAL 100.47 Sample Number: GS2100 (Black Glass) IUGS TAS Name: Medium-K Dacite Mineral Wt Norm quartz 46.6879 corundum 8.8344 orthoclase 8.8203 plagioclase 21.0599 (albite) (4.9676) (anorthite) (16.0924) hypersthene 11.6275 (enstatite) (7.3608) (ferrosilite) (4.2667) magnetite 1.2696

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ilmenite 1.7008 TOTAL 100.0004 Sample Number: GS2300 (Altered Black Glass BrecciaClast poor) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 34.1272 corundum 0.3107 orthoclase 17.0908 plagioclase 42.4155 (albite) (31.2455) (anorthite) (11.1701) hypersthene 3.6938 (enstatite) (0.7727 ) (ferrosilite) (2.9212) magnetite 0.8996 ilmenite 1.4634 TOTAL 100.00

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Major and Trace Element Data Microprobe Data Maps, Area Photos, Figures and Graphs

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TABLE 1 ( Back to Microprobe Data ) SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: APATITE 0.28 0 0 0 0.031 0 0 54.67 0.039 0 17.67 72.69 DOLOMITE 0 0 0 0 0.034 0.051 22.85 32.54 0 0 0 55.475 AN65 PLAG 54.754 0.074 28.894 0 0.54 0.014 0.102 11.76 4.254 0.335 0.018 100.745 QUARTZ 99.53 0.017 0.01 0 0.012 0.017 0 0 0.016 0 0 99.602 MARCASITE 0 0 0.01 0 66.99 0 0 0 0 0 0.01 67.01

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TABLE 2 ( Back to Microprobe Data ) White Glass White Glass Line SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 98.43 0.018 0.632 0.033 0.033 0.016 0.012 0.099 0.109 0.053 0.01 99.45 2 93.26 0 3.49 0 0.045 0.02 0.049 0.272 0.855 0.526 0.01 98.53 3 86.25 0.013 7.53 0 0.061 0.007 0 0.284 2.05 3.27 0.023 99.49 4 73.47 0.026 14.12 0 0.112 0.007 0.164 0.768 4.39 1.88 0.03 94.97 5 57.52 0 28.05 0 0.187 0.008 0.047 2.28 4.04 1.18 0.017 93.33 6 61.13 0.046 22.75 0 0.359 0.039 0.101 1.97 6.75 2.27 0.182 95.6 7 82.86 0.104 9 0 0.102 0.038 0.056 0.686 2.38 0.821 0 96.05 8 72.92 0 11.49 0 0.063 0 0.02 0.439 1.88 0.541 0.028 87.38 9 88.17 0.024 7.03 0.032 0.066 0 0 0.381 2.12 1.82 0 99.64 10 97.39 0.01 1.365 0.016 0.212 0 0.17 0.1 0.049 0.052 0 99.36 11 75.1 0.059 14.52 0 0.141 0.042 0.117 1.083 3.74 2.16 0.017 96.98 12 76.05 0.021 9.69 0.01 0.036 0 0.014 0.77 3.81 1.45 0.015 91.87 13 65.22 0.047 21.59 0 0.298 0.061 0 3.22 7.4 1.48 0.016 99.33 14 62.96 0.029 21.51 0 0.37 0.129 0.139 3.23 7.95 1.66 0.021 98 15 46.97 0.014 36.18 0.01 0.065 0.022 0.052 0.156 0.359 0.568 0.063 84.46 16 75.19 0.075 14.89 0.036 0.175 0 0.026 1.61 4.67 1.91 0.033 98.62 17 77.01 1.408 11.37 0 0.166 0.035 0.021 0.466 1.78 1.6 0.015 93.87 18 66.15 0.018 21.13 0.009 0.208 0.04 0.044 2.79 7.41 2.25 0 100 19 94 0 3.52 0 0.424 0.038 0.121 0.231 0.961 0.273 0 99.57 20 60.68 0.009 21.49 0 0.195 0 0.133 0.629 3.04 1.3 0.01 87.49 Average 75.54 0.096 14.07 0.0073 0.166 0.025 0.064 1.073 3.287 1.353 0.025 95.7 Bulk GS-06-00 78.6 0.207 12.69 0 1.324 0.085 0.976 0.016 3.25 2.755 0 99.91 Plagioclase Line 1 57.8 0 26.18 0.009 0.247 0 0 7.97 6.85 0.176 0.016 99.25 Andesine 2 58.19 0.024 26.33 0 0.212 0.01 0.022 8.24 6.77 0.175 0.01 99.98 3 57.65 0 26.06 0.012 0.257 0.008 0.037 8.19 6.6 0.17 0.022 99.01 4 57.6 0 25.92 0.012 0.233 0 0.028 8.12 6.73 0.195 0.031 98.87 5 59.91 0 24.69 0.037 0.209 0 0.01 6.22 7.53 0.259 0.01 98.88 Average 58.23 0.005 25.84 0.014 0.232 0.004 0.019 7.748 6.896 0.195 0.018 99.2

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Quartz Glass Line 1 98.08 0 0.53 0 0.128 0 0 0.074 0.037 0.027 0 98.88 Lechatlierite? 2 98.49 0.009 0.575 0 0.309 0.01 0.074 0.055 0.017 0.025 0 99.56 3 98.74 0.009 0.544 0 0.313 0.023 0.031 0.054 0.036 0.009 0 99.76 4 98.15 0 0.503 0.027 0.414 0 0.082 0.047 0.038 0.031 0.01 99.3 5 98.19 0.042 0.037 0.513 0.219 0 0 0.056 0 0.058 0.034 99.15 Average 98.33 0.012 0.438 0.108 0.277 0.007 0.037 0.057 0.026 0.03 0.009 99.33 Altered Feldspar 1 49 0 39.18 0 0.128 0.02 0.064 0.177 0.198 0.074 0.063 88.9 Kaolinite? Pyrite 1 0.047 0.02 0 0.027 65.36 0 0 0.015 0.17 0.032 0.01 65.68 2 0.142 0.01 0.021 0.013 66.08 0 0.087 0.023 0.158 0 0.055 66.59 Average 0.095 0.015 0.011 0.02 65.72 0 0.044 0.019 0.164 0.016 0.033 66.14

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TABLE 3 Spot analysis of individual spherule ( Back to Microprobe Data ) Suevite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 CO2 SO3 Cl Total Spherule rim 27.28 6.78 5.82 0.015 21.47 0.565 4.83 3.19 0.643 0.48 0.149 26.74 0.296 0.29 98.548 Solid glass Spherule 32.1 0.407 7.58 0.008 17.9 0.749 12.41 1.82 0.178 0.248 0.016 22.92 0.11 0.165 96.611 Solid glass Spherule 36.33 2.72 8.01 0.008 8.1 0.387 4.11 3.12 0.191 0.267 0.052 25.83 0.203 0.11 89.438 Solid glass Spherule 44.33 0.205 9.01 0.023 18.07 0.263 9.91 2.1 0.461 1.06 0.047 11.42 0.108 0.06 97.067 Solid glass Spherule 33.28 0.588 6.91 0 17.62 0.26 5.74 1.366 0.505 2.92 0.032 27.11 0.12 0.04 96.491 Solid glass Spherule 65.65 0.07 13.81 0.024 1.014 0.221 1.196 3.83 0.413 0.864 0.033 9.57 0.06 0.049 96.804 EDS spherule data 7.41 29.91 for Fe and Ti 7.71 38.14 6.43 29.89 2.7 10.11 4.86 18.05 TABLE 4a (Spherules and various phases) and 4b (Maskelynite) Spherule Transect SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 Cl Total Comments: 1 44.03 1.325 10.24 0 14.82 0.384 3.1 3.32 0.656 1.65 0.645 0.261 0.299 80.73 Glassy rim 2 63.03 0.01 13.38 0.014 0.195 0.007 0.075 6.09 0.42 0.963 0 0.039 0.05 84.27 Clay dervied by plag infill 3 66.11 0 13.97 0.01 0.21 0.038 0.05 6.54 0.413 0.874 0.013 0.036 0.023 88.29 4 57.96 0.011 10.1 0.043 0.155 0 0.016 5.93 0.363 0.774 0.01 0.021 0.038 75.42 5 63.69 0.017 12.12 0 0.123 0.025 0.039 5.98 0.349 0.953 0.01 0.01 0.018 83.33 6 63.83 0.01 14.24 0 0.156 0.024 0.029 6.35 0.426 0.899 0.029 0 0.022 86.02 7 66.36 0 13.79 0.013 0.223 0.021 0.058 6.15 0.674 1.21 0.01 0.079 0.157 88.75 8 65.34 0 14.1 0.028 0.438 0.062 0.071 6.23 0.489 1.22 0.01 0.018 0.113 88.12 9 64.97 0.023 13.75 0 0.107 0 0.037 6.2 0.5 1.38 0 0.042 0.054 87.06 10 62.51 0 11.34 0.015 0.12 0 0.028 5.54 0.483 1.54 0.01 0.033 0.066 81.69 11 64.55 0 13.4 0 0.264 0.054 0.029 6.01 0.43 1.124 0.013 0.082 0.134 86.09 12 63.24 0 13.33 0.01 0.276 0 0.026 6.18 0.519 1.051 0.01 0.027 0.055 84.72 13 64.91 0.027 13.75 0.02 0.244 0.13 0.096 6.26 0.561 0.768 0.041 0.036 0.101 86.94 14 61.04 0.01 12.85 0.041 0.206 0 0.03 6.29 0.549 0.82 0.04 0.015 0.044 81.94 15 62.41 0.019 13.09 0.009 0.239 0.036 0.098 6.28 0.623 0.943 0.019 0.064 0.037 83.87 16 41.8 4.48 8.45 0 17.65 0.392 6.8 3.55 0.442 0.873 0.316 0.138 0.138 85.03 Glassy rim 17 34.23 4.16 7.05 0.013 19.12 0.405 8.26 2.92 0.398 0.966 0.182 0.137 0.15 77.99 18 38.65 3.14 8.04 0 13.53 0.406 3.46 3.33 0.62 0.949 0.128 0.256 0.149 72.66 19 44.03 1.79 9.03 0 9.39 0.287 3.56 3.09 0.925 1.071 0.121 0.113 0.104 73.51 Spherule infill trans. SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 Cl 1 56.22 0.01 11.31 0.023 0.096 0.019 0.026 4.36 0.184 1.28 0 0.01 0.038 73.58 Clay dervied by plag infill 2 56.82 0 12.18 0 0.152 0 0.013 4.67 0.194 1.23 0 0.064 0.018 75.34

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3 65.39 0.01 14.38 0 0.133 0 0.049 5.01 0.087 1.088 0 0.01 0 86.16 4 60.75 0.01 10.87 0.01 0.134 0 0.03 4.8 0.241 1.65 0.01 0.088 0.025 78.62 5 61.56 0.02 9.74 0 0.125 0 0.028 4.97 0.566 1.35 0.01 0 0.024 78.39 Average 60.15 0.01 11.696 0.0066 0.128 0.004 0.0292 4.762 0.254 1.32 0.004 0.034 0.021 78.42 Augite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 Cl 1 52.59 0.441 2.16 0.01 8.98 0.321 15.74 18.94 0.26 0.035 0.015 0 0.021 99.51 2 52.23 0.472 2.31 0.059 9.11 0.301 15.85 19.03 0.265 0.028 0.012 0.01 0.007 99.68 3 52.03 0.461 2.2 0.018 9.38 0.328 15.63 18.94 0.305 0.016 0.015 0 0.021 99.34 4 52.17 0.491 2.33 0.039 9.39 0.32 15.49 19.09 0.27 0.01 0.012 0 0 99.61 5 51.67 0.606 2.8 0.05 9.6 0.31 14.94 19.45 0.294 0.024 0.01 0 0.014 99.77 Average 52.14 0.494 2.36 0.0352 9.292 0.316 15.53 19.09 0.279 0.023 0.0128 0.002 0.013 99.58 Magnetite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 Cl 1 0.112 9.12 4.26 0.084 82.9 0.347 3.84 0 0 0.014 0.015 0.077 0.021 100.8 Exsolution from magnetite? 2 0.116 9.03 4.27 0.1 83.78 0.334 3.87 0 0.036 0 0 0 0.01 101.5 3 0.064 9.08 4.33 0.075 83.15 0.359 4 0.015 0.047 0 0.033 0.066 0 101.2 4 0.108 9.07 4.21 0.157 83.11 0.372 3.92 0 0.034 0 0 0.034 0 101 5 0.104 9 4.24 0.123 82.69 0.378 4.03 0.045 0.039 0 0.023 0.01 0.029 100.7 6 0.12 9.68 3.91 0.075 81.92 0.38 3.76 0.03 0.019 0 0 0.01 0.011 99.92 7 0.103 9.61 3.98 0.08 81.93 0.382 3.89 0.037 0.038 0 0 0.03 0.017 100.1 Average 0.104 9.227 4.1714 0.0991 82.7829 0.365 3.9014 0.018 0.03 0.002 0.0101 0.032 0.013 100.8 Apatite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 Cl Total 1 0.21 0 0.021 0.508 0 0.131 0.318 38.98 0.011 0 17.83 0.182 0.661 58.85 2 0.21 0 0.01 0.422 0 0.075 0.342 38.78 0.024 0.011 17.46 0.12 0.644 58.1 3 0.187 0 0.019 0.432 0.021 0.073 0.294 39.14 0.021 0.015 17.98 0.174 0.697 59.05 Average 0.202 0 0.0167 0.454 0.007 0.093 0.318 38.97 0.019 0.009 17.757 0.159 0.667 58.67 TABLE 4b Maskelynite Glass 1 SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 Total 1 57.48 0 23.75 0.036 0 0 0 0.108 9.88 0.01 0 0.024 91.29 3 56.45 0.01 23.86 0.008 0.01 0 0 0.11 7.91 0.01 0 0 88.37 4 55.26 0.021 23.2 0 0.018 0 0 0.117 10.89 0.009 0 0 89.52 5 55.03 0 23.33 0 0 0.01 0 0.103 11.5 0.018 0 0 89.99 6 59.26 0.013 23.68 0 0 0 0.013 0.083 6.76 0.032 0 0.042 89.88 7 61.81 0 25.49 0 0.022 0 0 0.12 7.27 0 0 0.027 94.74 8 55.42 0 23.76 0 0.015 0 0 0.082 11.1 0.019 0 0.033 90.43

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9 55.55 0.026 23.64 0.036 0.021 0.013 0.019 0.106 11.49 0.022 0.017 0 90.94 10 55.94 0.011 23.73 0 0.028 0.046 0 0.069 11.69 0.03 0 0 91.54 Average 56.91 0.009 23.827 0.0089 0.01267 0.008 0.0036 0.1 9.832 0.017 0.0019 0.014 90.74 Maskelynite Glass 2 SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 1 55.6 0.013 23.02 0 0.04 0 0.017 0.034 11.98 0.037 0.01 0 90.75 2 55.71 0 22.9 0.007 0 0.01 0 0.057 12 0.056 0 0.03 90.77 3 55.82 0 22.75 0.024 0 0 0.01 0.055 11.95 0.046 0 0 90.66 4 53.02 0 22.72 0 0 0 0.028 0.038 12.69 0.02 0 0 88.52 5 55.53 0 22.72 0 0 0 0 0.01 11.65 0.066 0 0 89.98 Average 55.14 0.003 22.822 0.0062 0.008 0.002 0.011 0.039 12.05 0.045 0.002 0.006 90.13 Maskelynite Xtalline SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 1 54.45 0.052 28.08 0 0.68 0.009 0.11 11.3 4.26 0.254 0 0 99.2 2 54.33 0 27.97 0 0.651 0.01 0.086 11.79 4.14 0.235 0 0.021 99.23 3 54.09 0.029 28.28 0 0.646 0 0.077 11.53 4.11 0.216 0 0 98.98 4 54.08 0 28.05 0 0.682 0 0.102 11.84 4.09 0.215 0.025 0.01 99.09 5 53.09 0.038 28.79 0.01 0.664 0 0.075 12.59 3.79 0.226 0.01 0 99.28 Average 54.01 0.024 28.234 0.002 0.6646 0.004 0.09 11.81 4.078 0.229 0.007 0.006 99.16 Maskelynite Melt SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 SO3 1 64.31 0 13.38 0.037 0.045 0.043 0.066 5.84 0.114 1.118 0 0 84.95 2 63.63 0 12.31 0 0.087 0.013 0 5.55 0.078 1.141 0 0.01 82.82 3 63.47 0.02 12.62 0 0 0.038 0.021 5.66 0.08 1.118 0 0.027 83.05 4 65.96 0 13.53 0 0.068 0.018 0 5.78 0.061 1.077 0.01 0.01 86.51 5 65.47 0 13.63 0.026 0.041 0.026 0 6.06 0.05 1.036 0 0 86.34 Average 64.57 0.004 13.094 0.0126 0.0482 0.028 0.0174 5.778 0.077 1.098 0.002 0.009 84.74

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Zeolite Tuff or Suevite? (Plate set 4) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-06a-00 and possibly GS-11-00 Suevite SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-06a-00 62.31 0.82 16.1 7.395 2.37 6.95 0.22 1.16 2.33 99.699 GS-11-00 59.64 0.93 17 7.24 2.69 4.25 0.22 4 4.65 100.62 Hand Samples 1 2 3 These three photographs represent partially polished hand specimens of GS-06a-00. Upon first inspection, this sample appears to be a welded volcanic tuff. Textural, compositional, and structural evidence reveal it to be a suevite composed of turquoise-blue clasts (up to 6 cm in diameter in hand specimen), beige colored clasts and smaller yellowish clasts that are contained in a frothy beige matrix with rounded dark gray phases and specks of black phases. Plate 2 is a high resolution composite of the front and back of a hand specimen that is approximately 3 inches in length. Flow and plastic deformation can be seen in a creamy brown colored clast near the center of the specimen at the bottom of the image. Plate 3 is a high resolution scan of the billet for GS-11-00. Note the light beige clast near the center of the

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specimen, which is portrayed under plane-polarized (PPL) and cross-polarized light on the right hand side of plates 8 and 9. The billet measures roughly one and a half inches in length. Photomicrographs, SEM, Microprobe, and X-ray maps 4 5 6 7 8 9 PPL and XPL 15 X images (1-2, 5-6 and 9-10) and 40 X images (3-4 and 7-8) of sample GS-06a-00 (1-8) and GS-1100 (9-10) Plates 4 and 5 represents an overview image of GS-06a-00. Two turquoise -blue clasts can be seen in this image, which appear to represent quenched or devitrifying melt clasts (larger clast is on the right border and a smaller more crystalline clast is on the left border). Several beige clasts (andesite or tuff) can also be seen in these photos, as well as, augite, a few titano-magnetites and shocked plagioclase feldspar. Plates 6 and 7 are 40 x close-ups of one of turquoise-blue clasts. These clasts appear to be composed almost entirely out of microlites of feldspar, zeolites, rare calcite and chlorite(?). Plates 8 and 9 An overview image of GS-11-00, which may represent an impactite that is somewhat transitional between impact melt breccia and suevite. Notice the annealed clast on the right hand side of the photos, which was seen in hand sample (above, plate 3). Maskelynite 10 11 12 13 14 15 16 17 18 19 A

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The above photos consist of photomicrographs and Scanning Electron Microscopy (SEM) images of a partially diaplectic and altered labradorites. Plate 10 is a 100 x PPL image of an altered labradorite phenocryst with nonto low birefringent areas (maskelynite and analcime), and melt features that can be seen in the lower right side of the photo and also at the terminus of the crystal in the upper right corner. Plates 11 and 12 are 100x XPL images of the nonto low birfringent areas that are amorphous (maskelynite) and replaced by analcime, and birefringent areas that have remained crystalline (average ~An 65 labradorite). Plate 12 is rotated 90 from plate 11. During this rotation, these dark areas, which appear to be extinct, remains opaque indicating that it has undergone amorphization or has been replaced by analcime (cubic). Within the crystalline areas (mostly white), remnant albite twinning can be ascribed exhibiting first order gray in one twin plane against white in the opposing twin plane. Plates 13 and 14 (100 x PPL and XPL) The swath of feldspathic melt can be seen coming off near center left and at the terminus of the crystal on the right of these photos. Plates 15 and 16 (PPL and XPL) are 400x close-up of melt effects seen at the terminus of the crystal. Plates 17 and 18 are SEM backscatter images with different shades of black and white representing differences in composition. Plate 17 is of the altered labradorite phenocryst seen in plates 10-16. Plate 18 has two features (1) a recrystallized zeolite vein (bottom left half of the Plate) in contact with (2) a partially diaplectic and altered labradorite phenocryst. Plate 19 is a composite image (75 x) of a backscatter image of a partially diaplectic labradorite (above) with a topographic image of the same area (below). This composite image serves to prove that the isotropic areas are representative of the crystal and not plucked areas that have created a window into the glass of the thin section. Note that the areas that are crystalline are marked "lab" for labradorite, and the diaplectic and altered areas are marked "mask" for maskelynite are level in the topographic image. Plate A is a photomicrograph of a Manicouagan maskelynite grain; note the patchy texture of isotropic vs. non-isotropic areas, which is the result of an incomplete transformation of plagioclase feldspar into a diaplectic glass, which is visually similar to the plagioclase feldspars seen in GS-06a-00. X-ray Images of Altered Labradorite Phenocryst 1-Al 1-Fe 1-Ca 1-Na 1-K These five images (100 x) are Energy Dispersive X-ray (EDAX) maps of a maskelynite grain (from the images from above, Plates 10-17). The most noticeable features that are distinguished by the individual elemental maps are the zeolitized / diaplectic areas, the persevered crystalline areas, the melt that flows off the crystal and the surrounding

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matrix. (There is a "halo" effect and a fiber, which is easily seen in the Al image in black, in these images that should be ignored.) The "halo" is caused by ink that was used to mark the grain on the thin section. This "halo" can easily be seen in the Al image (bluish) and Fe image (greenish). The x-ray map within this "halo" is unaffected by the chemistry of the ink.) The zeolitized / diaplectic areas are marked by an extreme enrichment in Na (white areas in the Na map) and a complete depletion of Ca (black in the Ca map). The crystalline areas are marked in the Ca map by the white areas, which clearly contrasts with the analcime and diaplectic glass (black). The melt contains significant quantities of Ca, Al, and K, but no Na ( see microprobe data ), which is presently a zeolite phase (heulandite?) and appears to be flowing through the matrix (enriched in Fe). Mosaicism and Checkerboard Textures 20 21 22 23 24 25 26 Various photomicrographs and SEM images of mosaicism and Checkerboard textures. Plates 1-3 (PPL and XPL 50x) A large lath of labradorite with mosaic-like texture where offset platelets of the crystal exhibiting zeolite and glass as well as low-birefringent areas that have highly undulatory extinctions that are not simultaneous to one another (mosaicism?). Plates 4-7 (4 and 5 PPL and XPL 100x) (6 SEM backscatter 150x and 7 100x) Plagioclase crystals (probably labradoritic) exhibiting a checkerboard texture (CBT). Backscatter images show how lighter areas (crystalline) are chemically different than the darker areas (glassy). Spherules

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27 28 29 30 31 Glass type (100 x) Fluid-drop (40 x) Lithic type (40 x) A B C PPL, XPL and an SEM image of spherules of the three different types of spherules (glass, fluid-drop, and lithic). These brown glass spherules are rich in Fe, Mg and Ti, which was determined by Energy Dispersive Spectroscopy (EDS) and Electron Microprobe analysis (EMP) ( see microprobe data ). The larger spherules are in-filled with zeolite, plagioclase feldspar and clays. Plates 27 and 28 are 40 x PPL and XPL images of a spherule-rich cavity containing mostly lithic type spherules and a few fluid-drop spherules (those that have a spinifex texture). Plates 29 and 30 are 100 x PPL and XPL images of a spherule-rich cavity containing mostly glass type spherules with some pockets of altered plagioclase, zeolites and lithic type spherules. Plate 31 is a 150 x SEM backscatter image of the spherule-rich cavity seen in Plates 29 and 30 rotated 90 to the right. Included here are three close-ups of the three types of spherules seen in GS-06a-00: Glass, Fluid-drop and Lithic ( Graup, 1981 ). Plates A, B, and C Photos included for comparative proposes. The observed morphology of the Gatun spherules are somewhat consistent with several other types of "spherules" of extraterrestrial origins: chondrules (A. Axtell, a carbonaceous chondrite CV3), Lunar spherules (B) and K-T impact spherules (C). X-ray Images of Spherules

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2-SL 2-Si 2-Ti 2-Al 2-Fe 2-Mn 2-Mg 2-Ca 2-Na 2-K Energy Dispersive X-ray (EDAX) maps of a spherule-rich area (on the left side of the image) that is adjacent to a plagioclase feldspar lath (on the right) ( see microprobe data ) These elemental x-ray maps show the concentrations of the major elements in a spherule rich area (on the left) that is in contact with an altered plagioclase phenocryst (on the right). The brown glassy rims of the spherules (see plates 27 and 28 above) are enriched in Fe, Mg, Ti and even shows some concentration of Mn. K is entirely concentrated in the matrix and in the cracks (melt?) in altered plagioclase, while Na is entirely enriched within the confines of the crystal lath. Plastic Deformation And Melt Effects 32 33 34 35 36 37 38 39 PPL and XPL images of Plastic and melt effects of plagioclase feldspar in GS-06a-00. Plates 31 and 33 are 15x PPL and XPL images of partially melted "plasticized" plagioclase feldspar (requires a minimum of 3 GPa or 30 kbar). Note that the primary feature exhibits pinched out ends (indicating that it flowed) and a rim of quenched crystals. Plates 34 39 provide various PPL and XPL images of plagioclase melt effects and zeolite implacement seen throughout the sample GS-06a-00.

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Calcite Melt and/or Calcite Silicate Liquid Immiscibility 40 41 42 43 PPL and XPL images of Blue clasts and possible calcite melt effects seen within them. Plates 40-43 are PPL and XPL images of a blue clast (quenched melt) made up of microlites of plagioclase feldspar (grayish-white) and immiscible melt blebs? of calcite (yellowish) surrounded by a frothy glass matrix. Plates 40 and 41 are at 15 x magnification and 42 and 43 are at 40 x magnification. Fossils and Other Features 44 45 46 47 48 49 50 51 Plates 44 and 45 show a diversity of clasts and effects. Dead center in these photos is a fossil (possibly a bryozoa) and just above this clast a plagioclase feldspar has melted and plastically deformed around a lithic clast (the original lath shape of the plagioclase feldspar can be seen up and to the right from the fossil). Plates 46 and 47 also show a fossil (possibly a pelecypoda fragment) in contact with quenched plagioclase feldspar melt? (to the bottom left of the fossil fragment). Plates 48 and 49 are 100 x PPL and XPL images of a cluster of an odd cluster of oxides (magnetite and ulvspinel?). Plates 50 and 51 are 100 x PPL and XPL images of a dark rimmed (the rim was revealed to be very Mnrich by EDS analysis, as high as 22-46%) cored inclusion of anomalous plagioclase feldspars (also indicated by EDS data). CIPW Norms and TAS Identification

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Sample Number: GS06a00 (Suevite) IUGS TAS Name: High-K Andesite Mineral Wt Norm quartz 21.7265 orthoclase 19.4427 plagioclase 38.9581 (albite) (9.8156) (anorthite) (29.1425) diopside 4.4739 (wollastonite) (2.2282) (enstatite) (0.9065) (ferrosilite) (1.3392) hypersthene 12.3780 (enstatite) (4.9966) (ferrosilite) (7.3814) magnetite 2.1444 ilmenite 1.5384 TOTAL 100.662 Glass spherules contained in GS06a00 IUGS TAS Name: Leucitite Mineral Wt Norm quartz 0.9212 orthoclase 3.9817 plagioclase 23.8865 (albite) (7.6372)

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(anorthite) (16.2493) diopside 3.8558 (wollastonite) (1.9199) (enstatite) (0.7782) (ferosillite) (1.1577) hypersthene 40.0715 (enstatite) (16.1084) (ferrosilite) (23.9630) magnetite 8.7513 ilmenite 18.0746 apatite 0.4954 TOTAL 100.038 View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 5 ( Back to Microprobe Data ) Weathered Breccia Glass Fragment 1 SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 71.13 0.656 13.68 0.03 3.81 0.265 0.1 1.107 4.08 4.61 99.468 Unaltered black glass 2 70.88 0.466 15.89 0 2.62 0.065 0.041 2.26 5.24 3.2 100.66 with plagioclase and 3 72.65 0.67 13.61 0 3.29 0.109 0.051 0.845 3.67 5.19 100.09 apatite inclusions 4 69.71 0.447 15.23 0 2.28 0.072 0.054 2.52 4.66 3.04 98.013 5 71.02 0.641 14.07 0 3.6 0.226 0.045 1.5 4.45 3.75 99.302 6 75.22 0.692 12.25 0.009 2.73 0.045 0.041 1.51 3.57 3.08 99.147 7 69.29 0.424 17.02 0 1.95 0.04 0.035 2.78 5.66 2.99 100.19 8 70.28 0.604 15.04 0 2.6 0.127 0.035 2.26 4.57 3.17 98.686 9 72.81 0.406 13.07 0 3.04 0.112 0.037 1.66 4.16 3.38 98.675 10 73.07 0.548 11.68 0 3.92 0.062 0.081 0.957 3.12 5.11 98.548 11 70.6 0.514 15.04 0.044 3 0.182 0.024 1.57 4.69 3.72 99.384 12 71.87 0.685 13.94 0.018 3.72 0.2 0.099 1.156 4.55 4.41 100.65 13 73.92 1.021 12.86 0 1.78 0.01 0.053 0.734 3.7 5.17 99.248 14 64.82 0.239 20.68 0 1.42 0.056 0.007 4.86 6.47 1.73 100.28 15 70.41 0.612 14.59 0.017 3.12 0.065 0.029 1.48 4.35 4.52 99.193 16 71.43 0.748 13.44 0.01 3.6 0.162 0.077 0.979 4 4.92 99.366 17 71.01 0.689 13.73 0.009 3.78 0.169 0.047 1.66 4.27 3.34 98.704 18 70.95 0.625 13.84 0.019 3.49 0.079 0.033 1.219 4.27 4.24 98.765 19 70.02 0.616 15.28 0.013 2.36 0.042 0.032 1.68 4.82 4.33 99.193 20 69.06 0.232 14.89 0 1.85 0.078 0 3.27 4.66 1.77 95.81 21 71.74 0.713 14.49 0.037 3.12 0.1 0.047 1.8 4.59 3.25 99.887 22 66.36 0.284 18.98 0 1.67 0.047 0.025 3.92 6.01 2.08 99.376 23 71.15 0.671 13.53 0 3.76 0.128 0.024 0.886 4.11 4.93 99.189 24 66.34 0.416 12.3 0.027 1.79 0.211 0.027 1.296 3.43 4.27 90.107 25 68.42 0.437 17.36 0.017 2.67 0.109 0.072 3.34 5.61 2.45 100.49 Average 70.57 0.562 14.66 0.01 2.839 0.11 0.045 1.89 4.508 3.706 98.896 Glass Fragment 2 SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 69.83 0.152 17.41 0 0.387 0.016 0 1.99 5.6 4.27 99.655 Unaltered black glass 2 68.46 5.97 12.05 0 6.34 0 0.022 1.44 3.64 2.49 100.41 with plagioclase and

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3 71.15 0.257 16.95 0 0.739 0 0.025 2.26 5.4 3.24 100.02 apatite inclusions 4 75.47 0.531 12.16 0 1.86 0 0.046 1.296 3.38 4.27 99.013 This clast exhibited schileren 5 74.37 0.339 14.25 0 0.682 0.015 0.031 1.64 4.25 3.62 99.197 with strong flow banding Average 71.86 1.45 14.56 0 2.002 0.006 0.025 1.725 4.454 3.578 99.66 Glass and melt-bearing breccias Bulk rocks avg. 76.7 0.681 10.66 0 4.767 0.019 0.188 1.819 2.848 2.845 100.53 Glass Clast avg. 70.6 0.704 14.74 0.005 2.186 0.014 0.039 2.72 3.408 2.187 96.603 Apatite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 0.222 0.016 0 0 0.564 0.204 0.143 53.37 0.082 0.015 54.616 One of the apatites in the Black glass Altered Opaque Mineral 1 44.42 1.94 26.98 0 6.41 0.326 0 0.011 0.213 0 80.3 Yellowish opaque mineral 2 44.73 0.282 27.73 0 5.56 0.388 0.042 0.021 0.237 0 78.99 with a spinel structure 3 47.83 0.841 24.34 0 10.26 0.485 0 0.038 0.273 0.006 84.073 4 47.03 0.825 26.27 0.021 7.58 0.451 0 0.028 0.263 0 82.468 5 45.44 2.13 25.94 0 5.89 0.315 0.012 0.05 0.227 0.009 80.013 Average 45.89 1.204 26.25 0.004 7.14 0.393 0.011 0.03 0.243 0.003 81.169

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Weathered Breccia (Plate Set 5) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-08 Weathered Breccia SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-08-00 69.57 1.492 20.94 6.627 0.33 0.226 0.037 0.72 0.862 100.8 Field Photos 1 Plate 1 a massive occurrence of weathered breccia outcrops partially submerged on the north side of Potra Island. Beige and gray clasts occur in a reddish brown oxidized matrix of comminuted rock and mineral fragments. Hand Sample 2

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Plate 2 a close up high resolution scan of a billet of weathered breccia. Brecciated and comminuted fragments can be seen occurring pervasively throughout the sample. The billet measures roughly one and a half inches in length. Photomicrographs, SEM, Microprobe, and X-ray maps 3 4 5 6 7 8 9 10 XPL AND PPL images of the weathered breccias and relict unaltered black glass fragments. Plates 3 and 4 are 15 x images that represents the overall texture of sample GS-08-00. Plates 5 and 6 are 400x images of a opaque and nearly holohyaline fragment (glass w/o crystals) that has survived the alteration affects seen throughout this sample. Plates 7 and 8 are 15 x images of a hypocrystalline fragment exhibiting a flow-banded texture. Plates 9 and 10 are 400 x images, a close up, of the flow banding seen in the hypocrystalline fragment. View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 6 ( Back to Microprobe Data ) Qtz-Cpx corona Light Brown Glass SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 69.2 0.477 10.16 0.03 7.51 0.144 0.707 2.28 0.425 3.8 0.052 88.23 2 73.01 0.495 10.89 0 1.38 0.024 0.061 0.509 0.326 4.9 0.116 85.86 3 73.13 0.615 10.77 0 2.57 0.057 0.151 0.782 0.543 5.37 0.192 87.29 4 72.16 0.652 10.26 0 2.76 0.019 0.171 0.761 0.357 5.07 0.158 86.02 5 75.1 0.53 10.37 0 2.6 0.037 0.138 0.655 0.333 4.84 0.052 88.78 6 71.49 0.581 10.63 0 3.14 0.048 0.164 0.802 0.365 5.09 0.153 86.05 7 68.75 0.577 10.28 0 5.86 0.129 0.629 2.61 0.353 4.12 0.159 86.23 8 72.28 0.462 10.21 0 3.04 0.021 0.046 0.378 0.36 5.05 0.064 86.06 9 72.08 0.459 10.26 0 2.29 0.041 0.177 1.125 0.355 4.68 0.097 85.31 10 71.62 0.509 10.29 0 3.24 0.024 0.261 1.7 0.299 4.42 0.082 85.94 Average 71.88 0.536 10.41 0.003 3.439 0.054 0.251 1.16 0.372 4.734 0.113 86.58 Darker Brown Glass SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 83.69 0.175 3.24 0 2.53 0.018 0.882 0.827 0.25 0.783 0.031 90.54 2 88.61 0.219 3.31 0.01 1.94 0.029 0.502 0.667 0.309 0.991 0.032 94.62 3 80.85 0.228 6.76 0 2.99 0.044 0.19 0.391 0.341 2.16 0.016 91.06 4 80.73 0.205 6.87 0 2.86 0.029 0.218 0.418 0.405 2.19 0 90.91 5 80.48 0.28 6.7 0.01 2.84 0.037 0.207 0.396 0.407 1.94 0 90.55 Average 82.87 0.221 5.376 0.004 2.632 0.031 0.4 0.54 0.342 1.613 0.016 91.54 Glass to Quartz Trans SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 73.9 0.356 8.3 0.026 5.03 0.075 1.051 2.49 0.249 3.18 0.068 88.74 Glass 2 78.61 0.278 6.95 0 3.6 0.042 0.734 1.057 0.366 2.23 0.022 90.21 3 79.39 0.226 6.52 0 3.69 0.024 0.7 0.954 0.401 2.25 0.021 90.55 4 78.93 0.246 6.88 0.015 4 0.027 0.747 0.938 0.418 1.91 0.021 90.85 5 76.61 0.221 7.84 0 4.43 0.071 0.857 1.093 0.171 3.75 0 90.03 6 78.77 0.223 4.66 0 6.27 0.091 1.526 4.24 0.139 0.364 0.02 91.54 7 99.39 0 0.064 0 0.046 0.008 0 0 0 0.012 0 99.51 Quartz

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8 99.19 0 0.042 0 0.013 0 0 0.01 0 0 0 99.25 9 99 0 0.028 0 0.035 0 0 0 0.041 0.01 0 99.06 10 99.17 0.013 0.045 0 0.036 0 0 0.01 0 0.022 0 99.26 Pyroxenes Diopside SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 54.24 0.015 0.087 0.009 7.27 0.212 16.89 20.88 0.173 0.008 0.013 78.72 2 54.23 0.063 0.107 0.032 6.87 0.16 17.13 21.64 0.175 0 0.01 78.59 3 54.32 0.095 0.143 0.031 7.21 0.208 16.91 20.89 0.227 0.02 0.014 78.92 Average 54.26 0.058 0.112 0.024 7.117 0.193 16.98 21.14 0.192 0.009 0.012 78.74

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Anomalous Volcanics (Plate Set 7) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-10, GS-13A, GS-27 and P8-2-6-90 Anomalous Volcanic SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-10-00 50.51 0.719 14.65 10.07 8.479 12.6 0.158 1.955 0.927 100.07 GS-13a-00 50.38 0.677 13.48 10.89 9.125 12.84 0.161 2.121 1.211 100.87 GS-27-00 51.21 0.75 13.71 10.23 8.449 12.51 0.198 2.098 1.16 100.32 P8-2-6-90 50.79 0.987 17.35 9.991 6.19 10.12 0.2 2.929 0.788 99.34 Field Photos 1 Plate 1 Photograph of an outcrop of Macho Island sample GS-10-00. Hand Samples

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2 3 4 5 6 Plates 2 is a digital photograph of a hand sample of GS-10-00 from Macho Island, and Plate 3 is a high resolution scan of the sample (refer to plate 2 for scale) Plates 4 and 5 are digital photos of sample GS-13a-00 and Plate 6 is one of GS-27-00. Note the layering in these two igneous rocks. Photomicrographs, SEM, Microprobe, and X-ray maps 7 8 9 10 11 12 XPL and PPL images of the samples GS-10-00 (plates 7 and 8), GS-13a-00 (plates 10 and 11) and GS-27-00 (plates 11 and 12) Plates 7-12 are images of three samples that are similar mafic igneous rocks bearing phenocrysts and glomerocrysts of clinopyroxene (some of which is altered) and several phenocrysts of serpentinized olivine grains. The matrix is dominated by plagioclase feldspar, altered cpx and magnetite. Some serpentine/chlorite and several clots of calcite are found throughout the matrix of this sample. Samples GS-13a-00 and GS-27-00 are almost identical to sample GS-10-00, with the exception that the GS-10-00 contains less altered olivine phenocrysts and is not strongly layered. Pyroxene Necklace Structure (Diopside Corona formed around feldspathic glass with a quartz core) 13 14 15 16 17 18

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19 20 21 22 23 24 PPL, XPL and SEM backscatter (compositional) images of a well preserved pyroxene "necklace" (pyroxene-quartz corona) in GS-10-00. These three igneous samples differ from the rest in that they contain pyroxene necklaces or pyroxene-quartz coronas, a reaction texture commonly formed around a xenocryst of quartz in reaction with a more mafic melt. Plates 13 and 14 are 15 x images of the overall well preserved reaction corona, quartz is at the near center exhibiting a typical first order gray color, but is highly fractured, shows undulatory extinction and evidence of plastic deformation (upper left of the crystal). The brown material almost completely surrounding the quartz is a brown glass (feldspathic melt), which can be seen better in close up images in Plates 15-22. Diopsides displaying higher birefringence colors surrounds the quartz xenocryst and the brown glass completely. Other distinguishing features are two large vesicles in the quartz crystal, one of which appears to be rimmed by the brown glass (plates 19-24). Plates 23 is a SEM backscatter image (compositional) of the areas portrayed in plates 21 and 22. Here we can see clearly how the composition ranges from quartz (darkest gray) to glass (moderately dark gray) to pyroxene (light gray). Plate 24 is a SEM backscatter image (compositional) of a glass rimmed vesicle found in the quartz crystal that lies at the center of the pyroxene necklace. CIPW Norms and TAS Identification Sample Number: GS1000 (Basalt) IUGS TAS Name: Medium-K Basalt Mineral Wt Norm orthoclase 5.4946 plagioclase 44.8265 (albite) (16.4962) (anorthite) (28.3303) diopside 27.7770 (wollastonite) (14.2643) (enstatite) (8.5539)

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(ferrosillite) (4.9588) hypersthene 11.6805 (enstatite) (7.3941) (ferrosillite) (4.2864) olivine 5.9356 (fosterite) (3.6217) (fayalite) (2.3139) magnetite 2.9208 ilmenite 1.3671 TOTAL 100.0021 Sample Number: GS13a00 and GS2700 (Basalt) IUGS TAS Name: Medium-K Basalt Mineral Wt Norm orthoclase 7.0892 plagioclase 41.3263 (albite) (17.7846) (anorthite) (23.5417) diopside 32.0596 (wollastonite) (16.4566) (enstatite) (9.8259) (ferrosillite) (5.7771) hypersthene 1.5727 (enstatite) (0.9904) (ferrosillite) (0.5823) olivine 13.5446 (fosterite) (8.2189)

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(fayalite) (5.3257) magnetite 3.1293 ilmenite 1.2804 TOTAL 100.0021 View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 7 ( Back to Microprobe Data ) Porphyritic Glass Flow Banded Glass SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 78.42 0.48 10.52 0 1.153 0 0.062 0.201 1.225 5.24 97.3 2 77.76 0.433 10.27 0.03 1.4 0.01 0 0.213 1.25 5.04 96.41 3 76.76 0.438 10.91 0 1.29 0.012 0.009 0.295 1.47 5.09 96.27 4 71.91 0.292 13.9 0.012 1.052 0.02 0 0.881 3.65 4.14 95.86 5 76.89 0.377 10.3 0 1.43 0.013 0.044 0.233 1.44 5.06 95.79 6 75.83 0.366 10.01 0 1.285 0.095 0.045 0.4 1.45 4.94 94.42 7 63.37 0.877 11.89 0 10.96 1.98 0.408 2.27 4.21 2.72 98.69 8 70.82 0.361 10.07 0.034 4.08 1.091 0.182 1.72 2.1 4.41 94.87 Average 73.97 0.453 10.98 0.0095 2.831 0.403 0.094 0.777 2.099 4.58 96.2 Glass and melt-bearing breccias Bulk rocks avg. 76.7 0.681 10.66 0 4.767 0.019 0.188 1.819 2.848 2.845 100.5 Glass Clast avg. 70.6 0.704 14.74 0.0053 2.186 0.014 0.039 2.72 3.408 2.187 96.6 Spinel 1 2.78 15.57 2.71 0.016 70.74 1.493 1.127 0.117 0.063 0.135 94.75 ulvspinel?

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TABLE 8 ( Back to Microprobe Data ) Lithic Breccia Altered Amphibole SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 55.79 0.103 17.19 0 3.68 0 0.224 0.324 4.63 0.377 82.32 2 46.91 0.163 14.7 0 18.42 0 0.044 1.363 5.84 0.653 88.09 3 41.7 0.23 12.88 0.025 22.6 0 0.051 0.521 6.96 0.315 85.28 4 50.94 0.1 18.36 0 12 0.011 0.369 1.45 6.81 0.799 90.84 5 42.58 0.099 17.66 0.014 18.92 0 0.478 0.737 6.63 0.215 87.33 6 48.12 0.058 18.26 0.068 13.76 0.025 0.737 1.163 0.853 3.05 86.09 7 44.68 0.089 14.6 0.062 17.57 0 0.148 0.846 6.63 0.422 85.05 8 47.3 0.179 13.64 0 21.54 0.043 0.025 0.501 7.29 0.356 90.87 9 45.41 0.023 21.29 0.01 9.73 0 0.566 1.24 2.54 1.035 81.84 10 43.67 0.156 13.1 0.013 27.76 0.043 0.011 0.461 6.48 0.692 92.39 Average 46.71 0.12 16.168 0.0192 16.6 0.012 0.265 0.861 5.466 0.791 87.01 Magnetite and ilmenite exsolution 1 0.338 2.48 2.16 0.106 92.37 0.44 0.545 0.124 0.066 0.013 98.64 Magnetite 2 0.252 2.76 1.823 0.227 91.21 0.422 0.24 0.099 0.046 0.018 97.1 3 0.51 35.21 0.419 0.114 56.4 0.431 0.601 0.112 0.034 0.012 93.84 Ilmenite 4 0.263 39.46 0.305 0.075 53.08 0.606 1.75 0.062 0.008 0.029 95.64 5 0.15 41.8 0.234 0.016 51.2 0.376 1.379 0.052 0.012 0.013 95.23 6 0.186 42.53 0.219 0.044 50.87 0.387 1.443 0.046 0 0 95.73 7 0.01 40.35 0.179 0.044 57.89 0.393 3.08 0.037 0.031 0 102 8 0.018 39.87 0.185 0.063 57.84 0.188 0 2.02 0.009 0.008 100.2 9 0.172 41.76 0.241 0.064 51.64 0.227 1.162 0.054 0 0 95.32 Average 0.211 31.8 0.6406 0.0837 62.5 0.386 1.133 0.29 0.023 0.01 97.08 Amphibole altered to Calcite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 3.03 0 1.107 0 0.483 0.487 0 53.85 0.359 0.017 59.33

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Plagioclase Feldspar 1 57.35 0 25.82 0 0.205 0.014 0.023 8.75 6.19 0.246 98.6 Andisine Magnetite ilmenite exsolution 1 0.079 36.57 0.175 0.023 57.7 0.751 1.468 0.066 0.02 0 96.85 Quartz 1 99.92 0 0.044 0 0 0 0 0.016 0.369 0 100.3

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Lithic breccia and altered igneous rocks (Plate Set 10) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-14, GS-18 and GS-18A Lithic Breccia and Altered Igneous Rocks SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-14-00 63.62 0.565 18.86 5.224 0.261 6.514 0.206 3.542 2.004 100.79 GS-18-00 62.59 0.538 19.92 5.469 0.313 7.038 0.108 4.071 0.327 100.38 GS-18a-00 66.16 0.519 17.97 5.14 0.174 5.024 0.129 3.793 1.543 100.45 Field Photos 1 2 3 4 5 Outcrops of Lithic (fragmental) breccia and the lithic breccia / white-spotted gray glass contact (?). Plates 1-4 a boulder of lithic breccia GS-14-00 found on the eastern side of the central peak, which contains various discrete fragments including altered igneous clasts, mineral fragments and possibly other rock types. Plate 5 a photograph of a possible contact between the white-spotted gray glass (on the right) and the lithic breccia (on the left). Hand Samples

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6 7 8 9 10 Plate 6-8 are hand sample specimens of GS-14-00 the lithic (fragmental) breccia. Plate 8 is a high resolution scan of the lithic breccia (refer to plate 7 for scale relationship). Note the discrete fragments of altered gray and reddish igneous clasts in a matrix of comminuted rock and mineral fragments. Plate 9 is a digital photograph of GS-18-00 the altered gray igneous rock. Plate 10 a digital photograph of GS-18a-00 the altered reddish igneous rock. Photomicrographs, SEM, Microprobe, and X-ray maps 11 12 13 14 15 16 17 18 PPL and XPL 15 x images of the lithic (fragmental) breccias and the altered gray and reddish igneous rocks. Plates 11 and 12 are images of the lithic (fragmental) breccia GS-14-00. The fragments are rather discrete in plane-polarized light, but difficult to discern in cross-polarized light. The dominate fragmental clast appears to consist of the altered gray igneous rock GS-18-00. Plates 13-16 are images of the altered gray igneous rock Plates 13 and 14 has a kinked-banded biotite grain (on the right) and Plates 15 and 16 exhibit a relatively large fractured quartz grain. Plates 17 and 18 are images that show the overall texture and mineral abundances of the altered reddish volcanic rock (hand sample above in plate 10). Completely opaque amphiboles dominate. Altered Amphibole

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19 20 PPL and XPL image of a typical altered amphibole grain from GS-18-00. Plates 19 and 20 are images of an altered amphibole that has been replaced by an opaque amorphous material, Fe and Mn-rich calcite, euhedral apatites and aggregates of various other minerals that are difficult to discern under the microscope. Note the intruding veinlet near the midsection of the altered amphibole that appears to come from a lath of plagioclase feldspar from the upper right of the photo. Fractured Quartz w/ Calcite 21 22 Plates 21 and 22 are 100 x PPL and XPL images of a fractured quartz crystal with calcite occurring as the dominate fracture fill phase. Kink-banded Biotite 23 24 25 PPL, XPL and SEM backscatter images of the kinked-banded biotite grain found in sample GS-18-00. Plates 23 and 24 are 100 x images of a kinked-biotite surrounded by an annealed matrix of quartz and feldspars with two altered amphiboles and a zoned plagioclase feldspar near the top. Plate 25 is a SEM backscatter image (compositional) which best portrays the kinking in the biotite. Detached fragments within the biotite have motions indicative of a compressional stress field. Also noteworthy is the annealed matrix seen in the upper left and lower right of the image.

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CIPW Norms and TAS Identification Sample Number: GS1400 (Lithic Breccia) IUGS TAS Name: Medium-K Dacite Mineral Wt Norm quartz 18.5756 orthoclase 11.7214 plagioclase 59.2326 (albite) (29.7063) (anorthite) (29.5263) diopside 2.1975 (wollastonite) (1.0448) (enstatite) (0.1080) (ferrosillite) (1.0447) hypersthene 5.6994 (enstatite) (0.5342) (ferrosillite) (5.1652) ilmenite 1.5026 titanite 1.0736 TOTAL 100.00 Sample Number: GS1800 (Gray Andesite) IUGS TAS Name: Low-K Andesite Mineral Wt Norm quartz 19.0979 corundum 0.0472 orthoclase 1.9431 plagioclase 69.1129

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(albite) (34.3142) (anorthite) (34.7987) hypersthene 7.1980 (enstatite) (0.7693) (ferrosillite) (6.4287) magnetite 1.5804 ilmenite 1.0219 TOTAL 100.00 Sample Number: GS18a00 (Reddish Andesite) IUGS TAS Name: Medium-K Dacite Mineral Wt Norm quartz 24.4414 corundum 0.9710 orthoclase 9.1008 plagioclase 56.9740 (albite) (32.0698) (anorthite) (24.9042) hypersthene 6.5044 (enstatite) (0.4234) (ferrosillite) (6.0810) magnetite 1.4905 ilmenite 0.9876 TOTAL 100.47 View a list of the samples

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Choose samples by appearance Choose samples by location

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TABLE 9 ( Back to Microprobe Data ) Gray Glass Grey Glass Matrix SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 85.92 0.073 8.69 0 0.296 0.019 0.028 0.082 2.24 4.15 101.5 2 96.19 0.047 1.669 0.042 0.097 0.01 0 0.032 0.325 0.798 99.21 3 66.2 0.132 17.8 0.011 1.246 0.041 0 2.56 4.84 3.3 96.13 4 75.68 0.11 7.92 0 0.653 0.158 0.018 3.73 2.45 0.637 91.36 5 62.96 0.73 19.4 0 1.64 0.038 0.028 3.92 5.59 2.52 96.83 6 51.8 0.052 24.3 0 3.25 0.127 0 4.12 4.77 0.695 89.11 7 59.43 0.144 22.65 0 1.7 0.084 0.007 2.28 3.85 2.6 92.75 8 58.8 0.104 23.63 0 1.41 0.033 0 5.98 6.14 1.067 97.16 9 82.17 0.286 6.42 0 0.372 0.041 0 0.944 2.19 1.84 94.26 10 51.59 0.163 27.07 0 2.65 0.097 0 1.57 1.92 0.546 85.61 11 71.1 0.242 16.34 0.008 0.532 0.018 0 1.92 4.37 4.43 98.96 12 61.75 0.084 23.6 0.017 1.79 0.079 0 6 5.09 0.561 98.97 13 72.08 0.055 11.67 0.015 0.369 0.07 0.028 3.3 2.68 6.16 96.43 14 62.23 0.071 20.7 0.057 0.818 0.012 0 6.03 6.22 1.25 97.39 15 50.71 0.126 25.07 0 1.89 0.143 0.01 2.17 2.74 0.7 83.56 16 73.94 0.179 15.71 0 1.15 0.033 0.01 2.96 4.73 1.89 100.6 17 74.11 0.058 15.75 0.02 0.549 0.024 0 2.85 4.85 1.78 99.99 18 56.92 0.098 23.43 0.02 2.6 0.066 0 4.45 5.43 1.88 94.89 19 75.28 0.061 14.06 0 0.249 0.01 0 0.158 3.3 7.54 100.7 20 65.05 0.019 19.25 0 1.127 0.254 0 0.313 3.82 7.47 97.3 21 56.3 0.053 21.67 0 3.04 0.763 0 1.5 3.02 1.081 87.43 22 58.59 0.087 22.92 0.021 1.35 0.124 0 3.56 4.82 1.65 93.12 23 78.58 0.527 9.5 0 0.479 0 0 0.153 2.62 4.85 96.71 24 66.79 0.066 17.17 0 1.051 0.02 0 0.876 4.23 5.28 95.48 25 82.53 0.087 5.04 0.012 0.636 0.218 0 0.411 0.548 1.88 91.36 Average 67.87 0.146 16.86 0.009 1.238 0.099 0.005 2.475 3.711 2.662 95.07 Plagioclase SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments:

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1 56.09 0.028 24.93 0.039 0.46 0.022 0 8.93 5.91 0.405 96.81 Andesine 2 56 0.026 25.86 0 0.575 0.026 0.011 9.47 5.69 0.361 98.02 3 54.79 0 25.4 0 0.427 0.034 0.033 9.32 5.55 0.35 95.9 Average 55.63 0.018 25.4 0.013 0.487 0.027 0.015 9.24 5.717 0.372 96.91 Plagioclase w/ PFs SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 57.4 0.05 24.7 0 0.465 0.023 0 8.14 6.32 0.544 97.64 Andesine 2 59.24 0 23.28 0 0.369 0.061 0 6.98 6.91 0.689 97.53 3 58.28 0.011 22.55 0.016 0.37 0.021 0.041 5.99 7.34 0.825 95.44 4 59.56 0.009 23.39 0 0.319 0.048 0 6.89 6.88 0.683 97.78 Average 58.62 0.018 23.48 0.004 0.381 0.038 0.01 7 6.863 0.685 97.1 The PFs SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 48.01 0.01 31.52 0 4.33 0.148 0 1.99 1.71 0.292 88.01 Clay Alteration 2 46.18 0 35.91 0.01 1.63 0.036 0.031 0.186 0.401 0.254 84.64 Kaolinite? 3 49.82 0 34.55 0.02 1.95 0.303 0.024 0.284 0.146 0.154 87.25 4 46.25 0 32.52 0 1.91 0.334 0 0.361 0.116 0.127 81.62 5 43.64 0 33.2 0.033 2.04 0.069 0.012 0.261 0.161 0.268 79.68 Average 46.78 0.002 33.54 0.013 2.372 0.178 0.013 0.616 0.507 0.219 84.24 Apatite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 0.258 0.201 0.063 0 3.85 0.252 0.095 48.55 0.077 0.039 53.39 2 0.191 0.44 0.167 0 9.06 0.324 0.097 45.59 0.041 0.036 55.95 3 0.196 0 0 0 0.819 0.303 0.058 51.03 0.066 0.039 52.51 4 0.188 0 0.01 0 2.04 0.34 0.086 50.73 0.072 0.013 53.48 5 3.31 0 1.44 0.013 1.232 0.363 0.071 47.65 0.067 0.039 54.19 Average 0.829 0.128 0.336 0.003 3.4 0.316 0.081 48.71 0.065 0.033 53.9 Spinel SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 2.68 19.61 3.03 0.041 63.94 0.028 0.1 0.138 0.089 0.022 89.68 ulvspinel?

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White-spotted gray glass (Plate Set 11) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-15 and GS-17 Gray Glass SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-15-00 72.77 0.667 13.76 4.009 0.153 2.011 0.051 3.159 3.103 99.681 GS-17-00 68.36 0.913 16.17 2.937 0.218 3.408 0.012 4.315 3.629 99.971 Field Photos 1 Plate 1 a photograph of a possible contact between the white-spotted gray glass (on the right) and the lithic breccia (on the left). Hand Sample 2 3 4 5 Hand samples of GS-15-00 and GS-17-00, white spotted-gray glasses from southeast of the central peak. Plate 2-5 are

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hand samples of a white-spotted gray glass that was found associated with a lithic breccia and altered igneous rocks of just southeast of the central peak. Plates 2 and 3 exhibit the type of gray glass that has been hydrothermally altered and intruded by veins and veinlets of chalcedony and hematite? (reddish-brown material). Upon closer inspection, the white spots do not appear to be a crystalline phase. Plates 4 and 5 are of GS-17-00, a gray glass that has avoided the hydrothermal affects seen in GS-15-00. This sample exhibits a strong indication of flow and layering in hand specimen that GS-15-00 seems to lack. Plate 5 is a highresolution scan of GS-17-00. The sample is approximately three and a half inches in length. Abundant fractures can be seen in both samples. Photomicrographs, SEM, Microprobe, and X-ray maps 6 7 8 9 10 11 PPL and XPL 15 x images of the white-spotted gray glasses GS-15-00 and GS-17-00. Plate 6 and 7 shows an area in GS-1500 that is densely populated by white spots. These white spotted areas appear to be localized spots of devitrification. These areas are difficult to discern at higher magnification. Plates 8 and 9 exhibits a fractured area in GS-17-00. This sample has a white spotted appearance like GS-15-00, but they are smaller and less apparent than the ones seen in GS-15-00. One aspect of GS-1700 that is more noticeable than in GS-15-00 is the flow-banded matrix and preferentially aligned phenocrysts. Plates 10 and 11 displays one of many quartz veins that is pervasive through out sample GS-15-00. Plagioclase feldspar w/ planar fractures 12 13 14 15 16 PPL, XPL (with and without a gypsum plate filter) and SEM backscatter imagery of a fractured plagioclase feldspar. Plates 12 and 13 are 100 x images of a plagioclase feldspar (Andesine) with planar fractures (PFs). Note the microlites of feldspars in the matrix that appear to flow around the phenocryst. Plates 14 and 15 are 100 x XPL images with the gypsum plate inserted to accentuate the PFs and the infilled material that has an extinction angle different from the host crystal. Plate 15 is rotated 45 degress from plate 14. Plate 16 is an SEM backscatter compositional image of the andesine with PFs. In this image different shades of gray translate as different compositions (see table 9 the microprobe data, for further details).

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Apatite in a flow-banded hypocrystalline mesostasis 17 18 PPL and XPL image of an euhedral apatite crystal from GS-15-00, a white-spotted gray glass. Plates 17 and 18 are 500 x images of a euhedral apatite exhibiting a purplish-blue color in plane-polarized light (PPL). Note the white amorphous glassy matrix that flows around the crystal. CIPW Norms and TAS Identification Sample Number: GS1700 (White Spotted Gray Glass) IUGS TAS Name: Trachydacite Mineral Wt Norm quartz 21.2472 orthoclase 21.4526 plagioclase 50.6262 (albite) (36.5556) (anorthite) (14.0906) diopside 2.4456 (wollastonite) (1.1803) (enstatite) (0.2396) (ferrosillite) 1.0257 hypersthene 1.6291 (enstatite) (0.3084) (ferrosillite) (1.3207) magnetite 0.8511 ilmenite 1.7283

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TOTAL 101.01 View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 10 ( Back to Microprobe Data ) Altered Gray volcanic rock Kinked Biotite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 36.59 3.16 14.34 0.02 16.44 0.119 14.58 0.106 0.997 7.47 93.82 2 36.56 3.18 14.42 0.022 15.94 0.127 14.47 0.058 0.945 7.4 93.12 3 36.85 3.12 14.72 0 16.2 0.108 14.31 0.089 0.947 7.06 93.4 4 36.46 2.82 15.74 0.045 17.22 0.112 13.41 0.13 0.679 6.95 93.57 Average 36.62 3.07 14.805 0.022 16.45 0.117 14.19 0.096 0.892 7.22 93.48 Recrystallized Matrix 1 85.14 0.172 9.41 0.022 0.588 0 0.029 1.66 3.05 0.678 100.7 Quartz? Altered Amphibole SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 30.53 16.19 18.1 0.054 10.51 0.021 0.771 0.366 1.133 0.148 77.82 High-Ti! 2 32.72 0.913 17 0.034 18.82 0.027 0.837 0.99 1.61 0.264 73.22 3 38.47 0.133 20.7 0 15.96 0.017 0.734 1.89 2.38 0.284 80.57 4 26.54 2.25 9.61 0.125 46.71 0 0.143 1.57 4.24 0.202 91.39 High-Fe! 5 7.63 0.026 0.925 0.028 3.66 0.939 0.078 46.02 0.531 0.033 59.87 High Fe and Mn Carbonate 6 2.95 0 1.627 0.013 2.54 2.18 0.405 51.94 0.095 0.025 61.78 High Fe and Mn Carbonate 7 10.51 0.11 3.47 0.031 5.66 1.54 0.552 41.45 1.47 0.18 64.97 High Fe and Mn Carbonate Carbonate in the Matrix SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 0.01 0 0.013 0.009 2.63 3.11 0.481 53.67 0 0 59.92 High Fe and Mn Carbonate 2 0 0 0.01 0.013 2.21 2.58 0.444 54.46 0 0 59.72 High Fe and Mn Carbonate 3 0.065 0 0.011 0.009 1.95 2.52 0.303 55.41 0 0 60.27 High Fe and Mn Carbonate Average 0.025 0 0.0113 0.01 2.263 2.737 0.409 54.51 0 0 59.97 Titano-magnetite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 0.051 3.63 1.9 0.238 90.21 0.462 1.609 0.037 0.032 0 98.17 2 0.174 3.65 1.92 0.217 89.85 0.442 1.501 0.019 0.048 0 97.82 3 0.01 3.5 1.875 0.236 89.73 0.435 1.72 0.039 0.025 0 97.57 Average 0.078 3.593 1.8983 0.23 89.93 0.446 1.61 0.032 0.035 0 97.85

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Plagioclase SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 56.83 0 25.55 0.011 0.13 0 0.01 8.66 6.07 0.235 97.5 Andesine

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TABLE 11 ( Back to Microprobe Data ) Altered Reddish Igneous Rock Matrix Composition SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 1.411 0.141 0.377 0.061 5.09 0.654 1.97 48.51 0.143 0.012 0.031 58.4 carbonate 2 10.62 1.278 3.89 0.016 19.4 0.181 0.829 28.62 1.79 0.091 0.016 66.73 3 43.64 1.214 15.46 0.019 20.46 0.152 0.026 2.22 4.9 0.446 0.046 88.58 amphibole? 4 6.56 0.531 3.07 0.014 16.1 0.301 1.74 33.7 0.86 0.04 0.013 62.93 carbonate 5 16.83 1.591 6.14 0.04 25.89 0.158 0.634 21.85 2.59 0.351 0.021 76.1 6 38.87 1.239 14.26 0.032 17.23 0.322 0.043 3.54 3.29 2.01 0.613 81.45 amphibole? 7 28.54 1.313 12.17 0.062 26.82 0.391 0.04 2.01 3.33 1.41 0.045 76.13 8 34.42 1.033 10.75 0.016 18.16 0.188 0.03 0.713 3.44 2.73 0.023 71.5 9 34.3 0.682 11.8 0.033 27.68 0.296 0.184 1.12 3.95 0.235 0.023 80.3 10 34.55 0.957 11.39 0.029 20.17 0.103 0.038 1.68 5.49 0.518 0 74.93 11 75.91 0.016 13.7 0 0.351 0.009 0 2.91 4.26 0.406 0 97.56 plagioclase? 12 90.55 0.079 3.91 0.01 0.241 0.01 0.012 1.061 1.227 0.134 0.073 97.31 quartz Average 34.68 0.84 8.91 0.0277 16.47 0.23 0.462 12.33 2.939 0.699 0.075 77.66 amphibole? Plagioclase SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 56.45 0 26.68 0 0.395 0.01 0 8.61 6.01 0.37 0.018 98.54 Andesine 2 56.55 0 26.6 0 0.284 0 0 8.63 5.96 0.375 0 98.4 3 56.28 0 26.41 0.017 0.331 0 0 8.57 6.1 0.408 0 98.12 4 56.74 0 26.58 0.023 0.29 0 0.008 8.47 6.03 0.39 0.01 98.54 5 55.69 0.021 26.76 0 0.251 0.008 0 9.13 5.83 0.397 0 98.09 Average 56.34 0.004 26.61 0.008 0.31 0.004 0.002 8.682 5.986 0.388 0.006 98.34 Apatite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 0.039 0 0 0 0.275 0.165 0.153 52.6 0 0 17.56 70.79 Altered Feldspar 1 62.34 0.038 20.52 0.011 0.538 0.144 0 1.76 5.18 5.93 0 96.46 Sanidine?

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TABLE 12 ( Back to Microprobe Data ) Carbonate/Silicate rock Zeolites SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 56.77 0 22.84 0 0.278 0.145 0.025 1.69 5.63 0.05 87.43 Silicate side 2 60.21 0 21.54 0 0.186 0 0 0.309 6.15 0.078 88.47 Analcime 3 58.22 0.14 21.09 0 0.784 0.258 0.009 0.939 5.76 0.078 87.28 4 55 0.068 12.66 0 9.96 2.83 0.077 9.32 3.89 0.041 93.85 5 59.1 0.01 20.08 0.028 1.024 0.451 0.025 1.64 5.94 0.041 88.34 6 60.08 0 21.23 0.009 0.259 0.109 0.039 0.734 6.12 0.032 88.61 7 61.1 0 20.77 0.01 0.275 0.08 0.009 0.531 6.58 0.075 89.43 8 59.46 0.04 21.98 0 0.084 0 0 0.255 7.61 0.041 89.47 9 60.66 0.438 20.84 0.019 0.299 0.019 0.009 1.271 6.26 0.377 90.19 10 60.67 0 21.62 0 0.223 0.041 0 0.457 7.62 0.191 90.82 Zeolites SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 40.55 0 29.43 0.018 0.173 0.034 0.015 11.03 1.92 0.01 83.18 Carbonate side 2 41.27 0 29.32 0 0.256 0.027 0 10.59 2.14 0 83.6 Heulandite? 3 42.2 0.01 28.68 0 0.724 0.064 0.037 10.18 2.16 0.019 84.07 4 41.02 0 28.82 0 0.201 0 0 11.33 2.11 0.016 83.5 Average 41.26 0.003 29.06 0.005 0.339 0.031 0.013 10.78 2.083 0.011 83.59 Carbonate SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 4.65 0 0.646 0 0.199 0.098 0.036 51.41 0.056 0.031 57.13 Carbonate Line SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 24.84 0 8.62 0 0.443 0.094 0.081 30.23 2.13 0.03 66.47 ? 2 58.14 0.01 21.51 0.01 0.156 0.028 0 0.444 8.11 0.04 88.45 Analcime 3 16.71 0.01 5.68 0.034 0.237 0.14 0.007 38.69 1.52 0.027 63.06 ? 4 0.144 0 0.022 0 0.649 0.185 0.104 57.1 0.038 0.026 58.27 Calcite

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Pyrite SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 7.53 0 0.617 0.011 58.65 1.33 0.014 1.8 0.103 0 70.06

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Silicate/Carbonate melt rock? (Plate Set 13) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-19 Silicate/Carbonate rock SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-19-00 39.04 2.223 9.832 4.378 1.536 25.06 0.089 4.099 1.677 87.942 Hand Sample 1 Plate 1 a one and a 1 1/2" by 1" thin section billet of GS-19-00 exhibiting a possible contact between a silicate melt and a tuffaceous carbonate. Photomicrographs, SEM, Microprobe, and X-ray maps 2 3 4 5 PPL and XPL 15 x images of the carbonate and silicate / carbonate boundary seen in GS-19-00. Plates 2 and 3 are images of the carbonate side of GS-19-00. In the center of the image can be seen a lath shaped feldspar? that has been replace by calcite. Plates 4 and 5 are images of the boundary between carbonate (lower left) and silicate (upper right).

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Zeolites 6 7 8 9 10 11 PPL and XPL images of veins, veinlets and cavities filled with zeolites and calcite. Plates 6 and 7 exhibits a vein that intrudes into both regions of this sample (silicate-left and carbonate-right). On the silicate side, the calcite of the carbonate side immediately transitions into zeolites (analcime and heulandite). Plates 8 and 9 are 100 x close-ups of the zeolite-rich part of the vein. Plates 10 and 11 are 100 x images of a plagioclase feldspar that has altered into zeolite in the vesiculated silicate region of GS-19-00. View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 13 ( Back to Microprobe Data ) Green and Beige melt breccia Fossil-like feature--infilled vesicles SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: Chalcedony 97.16 0.216 1.48 0 0.022 0.024 0 0.044 0.139 0.022 0 99.11 Cavity-fill Greenish glassy rim 90.45 0.031 1.105 0 2.1 0.479 0.054 0.218 0.117 1.086 0 95.64 Greenish-brown amorphous rim Green rhombohedral inclusion 69.46 0.043 4.95 0.019 10.65 2.51 0.064 0.323 0.08 3.64 0.01 91.75 Tannish-Green inclusion surrounded by chalcedony Green Inclusion Line SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: 1 45.96 0 29.01 0.02 2.05 0.324 0.007 0.829 0.066 0.129 0.107 78.5 Kaolinite? 2 48.81 0 32.3 0 1.84 0.419 0.011 0.553 0.148 0.134 0.05 84.27 3 47.03 0 34.47 0.01 0.729 0.163 0.015 0.192 0.09 0.06 0.02 82.78 4 41.63 0 29.41 0.022 0.858 0.208 0 0.199 0.164 0.103 0 72.59 5 42.51 0 31.61 0 0.905 0.175 0.04 0.225 0.083 0.082 0.016 75.65 6 51.73 0 35.85 0 1.152 0.299 0 0.463 0.07 0.127 0.116 89.81 Average 46.28 0 32.108 0.0087 1.256 0.265 0.012 0.41 0.104 0.106 0.0515 80.6 Cavity fill with Odd inclusions SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: Yellowish-orange inclusion 32.88 35.56 16.86 0 4.08 0.625 0.016 1.001 0.271 0.054 0.072 91.42 Altered Sphene? 0.234 0 0.029 0 0.456 0.3 0.116 52.35 0.049 0.014 18.09 71.64 Apatites 0.347 0.016 0 0 1.59 0.354 0.116 49.35 0 0.016 16.95 68.74 adjacent to Yellowish-orange opaques Plagioclase SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: 1 57.64 0.023 26.2 0.01 0.653 0.06 0.008 9.32 5.71 0.454 0.01 100.1 Andesine 2 57.28 0.03 26.55 0 0.632 0.06 0 9.66 5.6 0.372 0.01 100.2 3 58.51 0.023 25.89 0.013 0.591 0.054 0.01 8.85 5.74 0.46 0.01 100.2 4 58.49 0.035 25.87 0.009 0.587 0.05 0.011 8.88 5.91 0.464 0.01 100.3 5 57.88 0.031 26 0 0.636 0.047 0 9.13 5.84 0.467 0.01 100 Average 57.96 0.028 26.102 0.0064 0.62 0.054 0.006 9.168 5.76 0.443 0.01 100.2 Inclusion in Plagioclase SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: 1 64.43 0.011 19.25 0 0.419 0.01 0.064 2.42 5.75 5.29 0.015 97.66 Na-rich orthoclase? Quartz melt? SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: 1 92.55 0.046 1.201 0 0.098 0.056 0.038 0.345 0.117 0.302 0 94.75 echatlierite? Immiscibility melts? Line across Chondrule-like Bleb SiO2TiO2Al2O3Cr2O3FeO MnO MgO CaO Na2O K2O P2O5Total Comments: 1 17.85 45.18 4.99 0 22.07 0.324 0.035 0.4 0.222 0.146 0.364 91.58 ? 2 38.68 10.5 13.2 0 24.88 0.619 0 0.456 0.314 0.314 0.205 89.17 ? 3 18.21 52.04 11.21 0.014 10.69 0.265 0.013 0.256 0.176 0.109 0.323 93.31 ? 4 25.42 42.51 15.26 0.025 5.82 0.359 0.02 0.271 0.14 0.137 0.185 90.15 ? 5 43.65 7.33 15.38 0 21.29 0.864 0.03 0.352 0.323 0.38 0.148 89.75 ?

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Si-rich part of Chondrule-like bleb SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 50.63 8.79 22.51 0 7.16 1.125 0 0.319 0.297 0.386 0.068 91.29 ? Ti-rich part of Chondrule-like Bleb SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 7.27 71.46 2.74 0 7.03 0.182 0.012 0.233 0.182 0.065 0.316 89.49 ? Dark Blebs within globules SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 97.16 0.216 1.48 0 0.022 0.024 0 0.044 0.139 0.022 0 99.11 Quartz Fe-rich globule that contains the Chondrule-like bleb 1 16 0 1.322 0 71.36 0.125 0.232 0.299 0.21 0.062 0.511 90.12 Hematite? 2 15.05 0 1.212 0 74.02 0.112 0.301 0.231 0.274 0.014 0.467 91.68 3 13.64 0.014 0.999 0 73.41 0.081 0.335 0.262 0.284 0.027 0.432 89.48 4 16.49 0.013 1.411 0 70.7 0.124 0.212 0.336 0.289 0.051 0.515 90.14 5 15.17 0.013 1.2 0.011 72.46 0.078 0.205 0.285 0.207 0.034 0.474 90.14 6 14.26 0 1.031 0 72.95 0.046 0.35 0.222 0.255 0.047 0.408 89.57 Si-rich rim on Fe-rich globule SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: 1 96.44 0.138 1.408 0 0.679 0.045 0.02 0.053 0.148 0.045 0 98.98 Quartz 2 97.26 0.152 1.344 0 0.4 0.01 0 0.071 0.515 0.022 0.01 99.78 3 97.52 0.099 1.316 0.01 0.458 0 0 0.06 0.147 0.016 0 99.63 4 97.18 0.171 1.288 0 0.394 0.01 0 0.071 0.082 0 0 99.2 5 89.93 0.119 6.32 0 0.581 0.01 0.01 0.655 1.69 1.21 0 100.5 Quartz? Rim on the Si-rich rim of the globule 1 66.3 0.608 19.02 0 0.681 0.011 0 2.43 5.73 4.95 0.014 99.74 ??? Similar to inclusions in Plagioclase xtals Na-rich Orthoclase

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Green and beige melt breccia (Plate Set 15) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-22 Green and beige melt breccia SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-22-00 70.71 0.929 14.95 3.751 0.378 2.462 0.039 3.571 3.279 100.07 Field Photos 1 2 3 Plates 1-3 massive bodies of greenish melt-bearing breccias in outcrop from the southwest region of the structure. Plates 1 and 2 plasticized beige clasts several centimeters in length can be seen in these breccias aligning to an apparent flow direction. Hand Samples

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4 5 6 7 8 Plate 4-7 are digital photographs of hand samples of GS-22-00, the beige and green melt-bearing breccia. This sample consists of poorly sorted beige and light greenish-beige clasts (sub-millimeter to a few centimeters in diameter) that are undergoing extreme plastic deformation and are supported by an emerald green, clast-rich, glassy mesostasis. Note the layering in the beige clasts, which may represent layering in the original clast or flow-banding as a result of melting and flow. The clasts lithologic origins are not recognizable in hand sample but may represent a rock type of clastic origins, possibly a siltstone or greywacke considering the geological setting for the Gatun Lake area. Plate 8 is a high resolution scan of the hand sample from plates 6 and 7 (refer to plates 6 and 7 for scale). Photomicrographs, SEM, Microprobe, and X-ray maps 9 10 11 12 13 14 15 PPL and XPL 15 x images of various clasts and melt effects seen in GS-22-00, the green and beige melt breccia. Plates 9 and 10 exhibits a basalt(?) clast (on the left) and a deformed, layered and vesiculated clast (on the right). Plates 11-12 are images of lenticular dark green and lime green bands noted in hand specimen. There appears to be no mineral that would indicate or explain the origin of the strong greenish color noted in hand specimen. The darker green band (centered) is highly vesiculated and contains rounded crystals of feldspars and quartz. Plates 13 and 14 is an image of a beige clast that was observed to have abundant red splotched in hand specimen. Several phenocrysts of plagioclase align themselves to the sense of flow. The red splotches (hematite?) appears to be oxidized iron bearing phases. Plate 15 may represent an annealed and plastically deformed siltstone clast (?). The clast appears to have been smeared across the slide and a veinlet from the smeared clast goes to or from a feldspar lath.

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Cavity Fills 16 17 18 19 20 21 22 PPL, XPL and SEM backscatter (compositional) images of various cavity fills found in GS-22-00, the green and beige melt breccia. Plates 16 and 17 are 50 x images of vesicle cavity fills (amygdules) that are pervasive throughout this sample. This particular feature caught our interest because of its remarkable resemblance to a turritella gastropoda, but its greenish Fe-rich feldspathic amorphous glassy rim and the common vesicles (some of which are also adjoined but do not bear this resemblance) distinguishes it from a fossiliferous origin (plates 18 and 19, 100 x). Plate 20 is a 75 x backscatter image of the bottom cavity fill and half of the one from the mid section. The infill materials are mostly quartz, chalcedony and quartz itself, which can be seen in PPL images as blocky crystals growing inward off the inner rim of the vesicles and outlined in a lighter gray by the scale bar in the SEM image. The crystal lath that shows up in white (near to the upper center of the image) is a rare barite crystal. Plates 21-22 are 100 x images of a rimmed cavity fill containing a green acicular mineral (kaolinte?) and alkali feldspars. Odd opaque minerals 23 24 PPL and XPL images of strange yellowish orange opaque in a cavity fill. Plates 23 and 24 are 100 x images of a cavity fill containing a strange yellowish orange phase that consists mainly of Ti, Si and Al with a few wt. % Fe, andesine, chlorapatite, barite, clays and possibly chlorite (green mineral, too small to resolve with EDS). Metal/Silicate Immiscibility

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25 26 27 28 SEM / Microprobe backscatter and secondary light images of reddish globules. Plates 25 and 26 are 300 x compositional images of one of the many reddish globules commonly seen in this sample. In compositional mode, metal bearing phases show up in very bright shades and silicates exhibit dark shades. The two white spherical objects are Fe-rich globules. The dark gray sinuous features that penetrate the two spherical forms in white are almost pure quartz. In plate 25, phases are marked based on their microprobe analyses results ( table 13 ) (Q quartz, Or? orthoclase? and Ap apatites) Based on their morphologies and chemistries (see below) these features most likely represent silicate/metal liquid immiscibility. Plate 27 is a 900 x compositional image close-up of the central chondrule-like feature that can be seen centered right in plate 25 and centered upward in 26. The colors have been inverted to better distinguish metal phases (now dark shades) from the silicate phases (now lighter shades). Plate 28 is a 900 x secondary light image of the feature exhibited in the previous plate. X-ray Maps of Metal/Silicate Immiscibility 1-Si 1-Ti 1-Al 1-Fe 2-Si 2-Ti 2-Al 2-Fe Si, Ti, Al, and Fe X-ray maps of the chondrule-like feature seen in plates 27 and 28 (above). Group 1 represents the unscaled data; group 2 represents scaled data in which white indicates areas of highest concentration of the given element. Group two better portrays the areas that are highly concentrated in a given element. The central feature in these images has a spinel shape in cross section and may represent a melting or decomposing spinel (titano-magnetite or a ulvspinel? see table 13 ) Within the feature, Ti-rich areas have segregated from areas rich in Si and Al. The feature is surrounded by an Fe-rich matrix and blebs of quartz that have Fe-rich rims that rapidly grade into almost pure quartz (>97% SiO2) that appear to have a morphology consistent with immiscibility affects (best seen in 2-Si and 2-Fe).

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View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 14 ( Back to Microprobe Data ) Glass breccia Black Glass Clast SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 68.01 0.609 16.13 0 2.23 0 0.014 3.05 4.03 3.37 97.443 2 72.05 0.672 13.89 0 1.205 0 0 2.63 3.68 3.61 97.737 3 69 0.814 15.8 0.013 1.63 0.012 0.01 3.17 4.13 2.83 97.409 4 70.05 0.679 15.13 0 2.56 0.008 0.036 3.19 3.63 2.5 97.783 5 69.83 0.789 14.54 0 2.03 0 0.089 2.75 2.74 1.7 94.468 6 68.79 0.561 15.89 0 2.25 0.033 0.025 3.25 4.12 2.21 97.129 7 65.34 0.587 18.22 0.017 1.027 0 0.074 2.2 1.63 1.88 90.975 8 70.61 0.631 13.75 0.03 2.04 0.042 0.031 3.25 3.86 2.16 96.404 9 90.27 0.265 3.97 0 2.35 0.01 0.014 0.632 1.051 0.542 99.104 10 68.87 0.397 16.72 0 1.29 0.01 0.183 2.29 2.77 1.164 93.694 11 75.86 1.089 12.4 0.022 1.55 0 0.028 2.59 2.81 1.67 98.019 12 64.4 0.77 18.88 0 2.24 0 0.069 2.03 1.96 1.61 91.959 13 70.36 0.628 14.4 0 2.07 0 0.012 2.31 4.04 3.21 97.03 14 71.32 0.975 14.13 0.007 2.34 0.019 0.03 2.92 3.63 2.04 97.411 15 69.68 0.753 15.19 0 2.3 0 0.026 3.59 4.38 1.91 97.829 16 71.05 0.703 14.58 0 1.59 0.041 0.026 3.25 4.12 2.05 97.41 17 69.98 0.85 15.65 0 1.87 0.01 0.052 2.34 2.8 1.98 95.532 18 67.89 0.404 17.59 0.017 1.142 0.029 0.032 2.85 4.91 3.23 98.094 19 66.92 1.151 14.91 0 7.35 0.024 0 3.05 4.05 2.2 99.655 20 71.8 0.762 12.94 0 2.66 0.032 0.026 3.05 3.82 1.88 96.97 Average 70.6 0.704 14.74 0.005 2.186 0.014 0.039 2.72 3.408 2.187 96.603 Devitrifying clast SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O Total Comments: 1 92.46 0.01 2.43 0.018 0.369 0.007 0.309 0.299 0.333 0.508 96.743 2 74.53 2.52 13.17 0 2.11 0.015 0.017 1.97 3.69 2.76 100.78 3 60.76 0.359 19.17 0.019 3.56 0.049 1.102 5.5 4.71 1.22 96.449

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4 57.44 9.78 12.04 0 11.65 0.035 0.349 2.43 3.7 1.58 99.004 High-Ti 5 69.66 0.092 17.87 0 0.591 0.007 0.05 4.37 5.19 1.67 99.5 6 61.84 0.345 22.34 0 0.942 0 0.064 5.6 5.57 1.81 98.511 7 61.74 0.117 22.48 0 0.942 0.008 0.053 6.15 6.65 1.6 99.74 8 82.8 0.078 7.25 0.008 0.303 0 0.036 1.076 1.82 2.02 95.391 9 62.07 0.341 22.49 0.04 0.885 0.012 0.045 6.25 5.8 1.93 99.863 10 87.95 0.408 5.46 0 0.614 0 0.026 0.959 1.196 1.57 98.183 Average 71.13 1.405 14.47 0.009 2.197 0.013 0.205 3.46 3.866 1.667 98.417

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The Glass Breccias (Plate set 1) View a list of the samples Choose samples by appearance Choose samples by location Samples GS-01, GS-03, GS-25, P8-2-4-90, 2-14-95-4 and 2-14-95-5 Glass Breccias SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-01-00 79.88 0.65 6.57 7.838 0.16 0.81 0.01 1.55 3.03 100.5 GS-03-00 78.03 0.56 8.21 8.087 0.08 1.64 0.02 2.05 2.11 100.78 GS-25-00 75.19 0.82 12.3 3.222 0.11 2.47 0.03 3.1 3.23 100.44 2-14-95-4 78.12 0.75 11 2.034 0.11 2.07 0.01 3.06 2.96 100.08 2-14-95-5 78.24 0.47 8.84 6.889 0.21 1.29 0.01 2.64 2.31 100.89 P8-2-4-90 76.75 0.6 12.8 1.551 0.26 1.98 0.02 3.97 3 100.94 Field Photos 1 2 3 4 5 Massive bodies of glass breccias found on a ridges to south and southwest of the central uplift. The Panamanian

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quarter is roughly the same size of an American quarter. Hand Samples 6 7 8 9 10 11 12 These hand samples represent two varieties of glass breccias found in association with one another on a ridges found to southwest of the central uplift. The first four (Plates 6 to 9) on the right distinguish themselves from the last three samples (Plates 10-12) on the left in that they are made up of discrete clasts that have sharp boundaries in a reduced matrix of finely pulverized glass, mineral fragments and sulfides, whereas the last two samples appear to have been annealed to the point where clast boundaries are not as sharp and the matrix is reduced to less than a few percent of the total rock. Plates 9 and 12 are high resolution scanned images of the samples in the plates that immediately proceed them (scale is not included in these images, but is provided in the previous images). The sample in plate 9 is approximately 5 inches in length and the sample in plate 12 is approximately 2 1/2 inches in length.

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Photomicrographs, SEM, Microprobe, and X-ray maps 13 14 15 16 17 18 PPL and XPL 15 X images (Plates 13 and 14) and 40 X images (Plates 15-18) of glass breccias. Notice the degree of fracturing and brecciation that is pervasive throughout the sample. The degree of fragmentation of the dark glass is most apparent in the veinlets of the sample represented by the (best seen in plate 13 and 14) photomicrographs. Dark clasts are highly fractured while beige clasts appear to be vesiculated or may be devitrified versions of the dark clasts (see below). The dark glass fragments appear to be enclosed by finely comminuted glass and mineral fragments, which appears beige in PPL images and isotropic in XPL images. This is best seen in plates 17 and 18. These veinlets also contain recrystallized or secondary microcrystalline quartz (chalcedony). Although the chalcedony is readily noticeable the veinlets, the veinlets are not dominated by this phase. Devitrification of Glass 19 20 21 22 23 24 25 26 27 28 PPL and XPL images of glass clasts undergoing devitrification. Images 21 and 22, 27 and 28 are at 40 x

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magnification, while all others are at 15 x. Plates 19 and 20 portray an excellent example of a glass fragment that grades into an area that is undergoing devitrification. Plates 21 and 22 is a close up, at 40 x, of this devitrifying area. Plates 24 and 25 show three types of clasts found in the glass breccias, the left side is occupied mostly by a devitrifying clast while the upper right is taken up by a glass fragment with some microlites aligning to flow features and the lower right which is occupied by a rare siltstone / graywacke clast. Plates 26 and 27 are PPL and XPL images of a centimeter sized devitrified clast that is barely discernable under crossed-polarized light. X-ray Map of a pyrite crystal 29 1-Si 1-Ti 1-Al 1-Fe 1-Mg 1-Na 1-K 1-S Plate 29 is a 100 x Reflected light photomicrograph exhibiting a pyrite crystal enclosed in glass and veinlets of microcrystalline material. The remaining plates are Energy Dispersive X-ray images (75 x) of pyrite (plate 29) and the surrounding glass and microcrystalline filled veinlets. The note worthy highlights of these x-ray maps are the differences between the microcrystalline veinlets and the glass, and the inclusion of glass in the pyrite. The glass in this particular sample distinguishes itself from the microcrystalline material found in the veinlets in that it is feldspathic and the veinlets are filled with probably chalcedony (see Plates 1-Si, 1-AL, 1-Na and 1-K). The inclusion of this feldspathic glass in the pyrite suggests that the glass is primary and that the pyrite in these breccias formed as a secondary phase. CIPW Norms and TAS Identification Sample Number: GS0100 (Glass Breccia)

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IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 53.2867 orthoclase 17.8174 plagioclase 15.0606 (albite) (13.0506) (anorthite) (2.0100) diopside 1.7611 (wollastonite) (0.8303) (enstatite) (0.0388) (ferrosilite) (0.8920) Hypersthene 8.5838 (enstatite) (0.3578) (ferrosilite) (8.2260) magnetite 2.2622 ilmenite 1.2284 TOTAL 100.0002 Sample Number: GS2500 (Glass Breccia Fused) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 38.4796 orthoclase 19.0881 plagioclase 36.3377 (albite) (26.2312)

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(anorthite) (10.1065) diopside 1.8879 (wollastonite) (0.8965) (enstatite) (0.0854) (ferrosilite) (0.906) Hypersthene 2.19 (enstatite) (0.1886) (ferrosilite) (2.0014) magnetite 0.9337 ilmenite 1.5574 TOTAL 100.4744 View a list of the samples Choose samples by appearance Choose samples by location

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TABLE 15 ( Back to Microprobe Data ) Shocked Carbonate Amorphous and Glassy areas SiO2 TiO2 Al2O3 Cr2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Comments: Bleb1 38.16 0.012 4.2 0.022 1.244 0.421 26.6 0.542 0.156 0.184 0.01 71.55 Bleb2 23.23 0.027 2.9 0 0.982 0.174 14.08 25.23 0.262 0.144 5.03 72.06 Bleb3 37.17 0.088 2.94 0 2.5 5.72 29.2 1.46 0.315 0.055 0.082 79.53 Bleb4 42.9 0.01 4.04 0.01 1.5 0.424 33.39 0.71 0.345 0.173 0.025 83.53 Bleb5 38.14 0.037 4.66 0 2.18 0.52 23.91 0.757 0.352 0.254 0.015 70.83 Average 35.92 0.035 3.748 0.006 1.681 1.452 25.44 5.74 0.286 0.162 1.032 75.5 Calcite 0 0 0 0 0.235 0.03 0.36 59.98 0.008 0.028 0.017 60.66

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Shocked Carbonate? (Plate Set 17) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-30 and P8-2-7-90 Shocked Carbonate SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-30-00 22.73 2.11 7.042 5.168 6.305 41.86 0.62 0.055 0.065 85.954 P8-2-7-90 11.97 1.321 4.971 5.559 8.712 47.92 0.624 0.014 0.059 81.154 Field Photos 1 2 Plates 1 and 2 photographs of the outcrop of shocked carbonate which juts out of the waters of Lake Gatun quite dramatically. The carbonate appears to be quite resistant to weathering and seemingly has been recrystallized. This particular carbonate, when compared with the local limestones and carbonates beyond the perimeter of the structure, exhibits remarkably strong induration, conchoidal fracture and sparks when struck with a hammer. Hand Samples

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3 Plates 3 a high resolution scan of two billets from GS-30-00 and P8-2-7-90. The billets are roughly one and a half inches in length. Note the spotted appearance of this sample and abundant fusilinids (?) in this sample. These "spots" appear be vitreous and are randomly distributed throughout the sample. Photomicrographs, SEM, Microprobe, and X-ray maps 4 5 6 7 8 9 PPL and XPL images of samples P8-2-7-90 and GS-30-00, the shocked carbonate. Plates 4 an 5 are 40 x images that best portray the "spots" or blebs of amorphous and glassy materials. In plane-polarized light (PPL), these areas are characterized by dark brownish black aggregates of an opaque material and clear glass (actual glass, void spaces, plucked areas?). These areas are completely opaque and isotropic under crossed Nichols (XPL), which gives this sample a very distinct mottles appearance in XPL. At the bottom left of these images, sparry calcite can be observed (possibly a recrystallized fossil ?). Plates 6-9 are 15 x images of GS-30-00, which is more fossiliferous than the sample P8-2-7-90. The most abundant fossils have morphologies consistent with a fusilinids. The blebs in these samples do not appear to be as discrete as those in P8-2-7-90. X-ray image of highly concentrated area of blebs 1-CP 1-Si 1-Ti 1-Al 1-Fe 1-Mn 1-Mg 1-Ca 1-Na Elemental x-ray maps (100 x) of the sample P8-2-7-90, a shocked carbonate with blebs of glassy and amorphous materials. 1CP is a compositional image which shows carbonates in white and light shades of gray and silicates in black and darker shades gray.

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The biggest distinction observed in this sample is between silicates and carbonates and the elements associated with these two primary elements. By comparing these maps, it can be seen that Si and Ca are divided with some degree of overlap. Ti and Na appear to be evenly distributed throughout the rock, while Mg, Al and Fe are mostly concentrated in the Si-rich areas. These observations are also corroborated by EDS and EMP analyses. Several Mg and silica rich areas exhibit EDS patterns consist with spinels and pyroxenes. The Ca-rich areas have spectra and major element distributions consistent with calcite. There were no signs or traces of dolomite to be found in the sample in thin section or during EDS or SEM analysis. View a list of the samples Choose samples by appearance Choose samples by location

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REFERENCES Bohor, B. F. and Glass, B. P., 1998, The crystalline lunar spherules; their formation and implications for the origin of meteoritic chondrules: Meteoritics and Planetary Science, v. 33, no. 1, p. 13-29 Boles, J. R., Flanigen, E.M., Gude, A.J., Hay, R.L., Mumpton, F.A. (ed.), Surdam, R.C.,1977, Minerolgy and Geology of Natural Zeolites: MSA Short Course Notes, v. 4. 233 p. Chen, M. and El Gorsey, A., 2000, The nature of maskelynite in shocked meteorites: not diaplectic glass but a glass from shock-induced dense melt at high pressures: Earth and Planetary Science Letters, v. 179, p. 489-502 Daniel, I., Gillet, P., McMillan, P. F., Wolf, G., and Verhelst, M. A., 1997, High-pressure behavior of anorthite: Compression and amorphization: Journal of Geophysical Research, v. 102, No. B5, p. 10,313-10,325 Deer, W. A. Howie, R. A., and Zussman, J., reprint 1993, An Introduction to rock forming minerals: Longman Scientific & Technical, Hong Kong, China. 696 p. Defant, M. J., Jackson, R. E., Drummond, M. S., deBoer, J. Z., Bellon, J., Feigenson, M. D., and Stewart, R. H., 1992, The geochemistry of recent volcanism throughout western Panama and southeastern Costa Rica: An overview: Jour. Geol. Soc. London, v. 149, p. 569-579 Dressler, B. O., and Reimold, W. U., 2001, Terrestrial impact melt rocks and glasses: EarthScience Reviews, v. 56, p. 205-284 Dressler, B. O., Grieve, R. A. F., and Sharpton, V. L., eds. 1994, Large Meteorite Impacts and Planetary Evolution: GSA Special Paper 293. 348 p. El Goresy, A., 1968, The opaque minerals in impactite glasses: In Shock Metamorphism of Natural Materials (B. M. French and N. M. Short, eds.), Mono Book Corp., Baltimore, p. 531553

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French, B. M., Koeberl, C., Gilmour, I., Shirey, S. B., Dons, J. A., and Naterstad, J., 1997, The Gardnos impact structure, Norway: Petrology and geochemistry of target rocks and impactites: Geochimica et Cosmochimica Acta, v. 61, no. 4, p. 873-904 French, B. M., 1998, Traces of Catastrophe: A handbook of shock-metamorphic effects in terrestrial meteorite impact structures: Houston, Lunar and Planetary Institute, LPI Contribution No. 954, 120 p. Graup, G., 1981, Terrestrial chondrules, glass spherules and accretionary lapilli from the suevite, Ries Crater, Germany: Earth and Planetary Science Letters, v. 55, p. 407-418 Graup, G., 1999, Carbonate-silicate liquid immiscibility upon impact melting: Ries Crater, Germany: Meteoritics and Planetary Science, v. 34, p. 425-438 Grieve, R. A. F., 1978, The melt rocks at Brent Crater, Ontario, Canada: Proceedings of the 9th Annual Lunar and Planetary Science Conference, p. 2579-2608 Grieve, R. A. F., 1991, Terrestrial Impact: The record in the rocks: Meteoritics, v. 26, p. 175-194 Grieve, R. A. F. and Pesonen, L. J., 1992, The terrestrial impact cratering record: Tectonophysics, v. 216, p. 1-30 Koeberl, C., and Anderson, R. R., eds. 1996, The Manson Impact Structure, Iowa: Anatomy of Impact Crater: GSA Special Paper 302. 468 p. Leroux, H., 2001, Microstructural shock signatures of major minerals in meteorites: Eur. J. Mineral., v. 13, p. 253-272 Melosh, H. J., 1989, Impact Cratering: A geologic process: Oxford University, New York, New York. 245 p. Montanari, A. and Koeberl, C., Impact Stratigraphy: The Italian Record: Verlag Berlin Heidelberg, Springer Press, Berlin, Germany. 364 p.

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Poag, C. W., 1999, Chesapeake Invader: Discovering Americas Giant Meteorite Crater: Princeton University Press, Princeton, New Jersey. 183 p. Reimold, W. U., Barr, J. M., Grieve, R. A. F. and Durrheim, R. J., 1990, Geochemistry of the melt and country rocks of the Lake St. Martin impact structure, Manitoba, Canada:Geochimica et Cosmochimica Acta, v. 54, p. 2093-2111 Reimold, W. U., Koeberl, C. and Brandt, D., 1997, Suevite at the Roter Kamm impact crater, Namibia: Meteoritics and Planetary Science, v. 32, p. 431-437 Roddy D. J. and Davis, L. K., 1977, Shatter cones formed in large-scale experimental explosion craters. In Impact and Explosion Cratering: Planetary and Terrestrial Implications (D. J. Roddy, R. O. Pepin, and R.B. Merrill, eds.): Pergamon, New York, New York. 1301 p. Simon, S., Grossman, I., Casanova, S, Symes, S., Benoit, P., Sears, D. and Wacker J., 1995, Axtell, a new CV3 chondrite from Texas: Meteoritics and Planetary Science, v. 30, n. 1, p. 4246 Spudis, P. D., 1993, The Geology of Multi-ring Impact Basins: The moon and other planets: New York, Cambridge University Press, 263 p. Stoffler D. and Lagenhorst F., 1994, Shock-metamorphism of quartz in nature and experiment: I. Basic observation and theory: Meteoritics and Planetary Science, v. 29, p. 155-181 Stoffler, D., and Grieve, R.A.F., 1994, Classification and nomenclature of impact metamorphic rocks: A proposal to the IUGS subcomission on the systematics of metamorphic rocks: European Science Foundation Network on Impact Cratering Newsletter, v. 2, p. 8-15 Tenthorey, E. A., Ryan, J. G., and Snow, E. A., 1996, Petrogenesis of sapphirine-bearing metatroctolites from the Buck Creek ultramafic body, south Appalachians: Journal of Metamorphic Geology, v. 14, p. 103-114 Tyburczy, J. A. and Ahrens, T.J., 1986, Dynamic compression and volatile release of carbonates: Journal of Geophysical Research, v. 91, p. 4730-4744 Tornabene, L.L., Stewart, R.H. and Ryan, J.G., 1999, Characterization and Age of a Probable

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Tertiary Impact Site near Gamboa, Panama Canal Zone: Abstract Presented at GSA Annual meeting, v. 31, no. 7, p. 174. Tornabene, L.L., Stewart, R.H. and Ryan, J.G., 2001, A petrographic and geochemical investigation into the Gatun Structure, a possible Tertiary impact structure near Gamboa, Republic de Panama: Abstract Presented at the AGU Spring Meeting, v. 82, no. 20, p. S249 White, J. C., 1993, Shock-induced amorphous textures in plagioclase, Manicouagan, Quebec, Canada: Contrib Mineral Petrol, v. 113, p. 524-532 Williams, Q., and Jeanloz, R., 1989, Static amorphization of anorthite at 300 K and comparison with diaplectic glass, Nature, v. 338, p. 413-415 Woodring, W. P., 1982a, Geology and Paleontology of Canal Zone and Adjoining Parts of Panama: U.S. Geological Survey Paper 306-b, United States Government Priniting Office, Wasington D.C. Woodring, W. P., 1982b, Geology and Paleontology of Canal Zone and Adjoining Parts of Panama: U.S. Geological Survey Paper 306-f, United States Government Priniting Office, Wasington D.C., 745 p. Revised: January 23, 2002

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The Gatun Suite (collected in July 2000 by Livio L. Tornabene) Sample ID Plate Set # Rock Type GS-01-03-00, GS-25-00 1 Glass breccias GS-04-00 2 Porphyritic andesite? (possible impact melt rock?) GS-05-00 2 Basaltic andesite GS-06-00 3 White glass (impact melt?) GS-06A-00 4 Turquoise blue clast breccia (suevite?) w/ glass spherules and maskelynite GS-07-00 2 Basaltic andesite w/ fossil fragments GS-08-00 5 Heavily weathered glass breccia GS-08A-00 2 Basaltic andesite GS-09-00 6 Shocked Sandstone? GS-10-00 7 Basalt? w/ pyroxene-quartz coronas (crystalline impact melt?) GS-11-00 4 Tuffaceous breccia (suevite / impact melt breccia?) w/ melt components and possible maskelynite GS-12-00 8 Graywacke

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GS-13-00 9 Hypocrystalline glass w/ phenocrysts of plagioclase and flow features (impact melt?) GS-13A-00 7 Layered porphyritic basaltic andesite? w/ pyroxenequartz coronas (crystalline impact melt?) GS-14-00 10 Lithic or fragmental breccia (igneous, siliciclastic, and carbonates fragments) GS-15-00 11 White-spotted gray fractured hypocrystalline glass with flow features and veins of chalcedony (impact melt?) GS-16-00 12 Chert w/ veins of chalcedony GS-17-00 11 White-spotted gray hypocrystalline glass with flow features (impact melt?) GS-18-00 10 Altered gray igneous rock (polymict breccia?) GS-18A-00 10 Altered reddish igneous rock (polymict breccia?) GS-19-00 13 Recrystallized carbonate cemented w/ zeolites and siliceous material (silicate/carbonate melt rock?) GS-20-00 14 Green tuffaceous rock GS-21-00 9 Spherulitic hypocrystalline glass w/ flow features and phenocrysts of plag. and pyroxenes (impact melt?) GS-22-00 15 Green and beige melt breccia w/ abundant flow features (impact melt breccia?) GS-23-00 9 Altered hypocrystalline clast poor glass breccia w/ phenocrysts of plagioclase (similar to glass breccias) GS-24-00 6 Shocked sandy siltstone? GS-26-00 12 Sandy chert w/ veins of chalcedony GS-27-00 7 Layered porphyritic basaltic andesite? w/ pyroxenequartz coronas (crystalline impact melt?) GS-28-00 8 Graywacke (identical to GS-12-00) GS-29-00 16 Tuffaceous Carbonate like P8-2-5-90 GS-30-00 17 Shocked Carbonate? like P8-2-7-90

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The P8 and 2-14-95 Stewart Suite (collected in 1990 and 1995 by R. H. Stewart) Sample ID Plate Set # Rock Type P8-2-1-90 2 Andesite *P8-2-2-90 6 Shocked sandy siltstone? *P8-2-4-90 1 Glass breccia P8-2-5-90 16 Fragmental tuffaceous carbonate w/ fragments of Plagioclase and other igenous materials (carbonate fragmental breccia?) P8-2-6-90 7 Basaltic andesite *P8-2-7-90 17 Shocked carbonate? *2-14-95-4 1 Sulfide-rich glass breccia *2-14-95-5 1 Glass breccia Caimito Core na Calcareous graywacke Und. CR Caimito na Calcareous graywacke Caimito country rock CR Limestone na Limestone Country rock

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Dark or Black Glasses (Plate Set 9) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-13, GS-21 and GS-23 Dark Glasses SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-13-00 70.46 0.531 14.01 3.035 0.694 1.927 0.083 4.026 4.479 99.242 GS-21-00 69.46 0.903 17.44 4.393 2.971 3.258 0.031 0.592 1.505 100.56 GS-23-00 73.24 0.772 13.57 3.098 0.309 2.248 0.085 3.692 2.895 99.907 Field Photos 1 Plate 1 outcrop of GS-21-00, a massive hypocrystalline black glass exhibiting excellent conchoidal fracture from the southwest part of the structure. Hand Samples

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2 3 4 5 6 7 Hand samples of massive dark glasses of the Gatun Structure. Plates 2 and 3 sample of the GS-13-00 porphyritic glass exhibiting phenocrysts of plagioclase feldspar and pyroxenes and a very irregular fracture. Plates 4 and 5, this sample is a massive dark hypocrystalline brown glass that bears a strong spherulitic texture that can even be seen in hand specimen (best seen in the bottom half of plate 5). Of all the glasses found in this suite, this sample is the most crystal poor, however, it closely resembles sample a less crystalline version of GS-13-00. Partially assimilated phenocrysts of plagioclase, magnetite and pyroxene are found but not common (less than 5 % total). The smaller population of phenocrysts, primarily feldspars, exhibits a strong alignment with the apparent direction of flow. Plates 6 and 7 This sample is a massive dark gray glass breccia that is cut by numerous veinlets of a white material that is pervasive throughout the sample and in outcrop (maybe glass or microcrystalline quartz). This sample is relatively clast poor, but it contains several partially assimilated or annealed greenish gray clasts that are not clearly identifiable in hand specimen. Photomicrographs, SEM, Microprobe, and X-ray maps 8 9 10 11 12 13 14 15 16 17 18 PPL, XPL (15x) and SEM images of the black glasses and their textures. Plates 8 and 9 are images from the porphyritic black glass GS-13-00 with a strong flow-banded texture and exhibiting dark schlieren that appear to be emitting from plagioclase phenocrysts, possibly representing quenched melts of plagioclase feldspar. The phenocrysts of plagioclase feldspar and opaques in these glasses are strongly aligned to the apparent direction of flow. Plates 10-13 GS-21-00, including GS-13-00, differ in thin section from the other glasses (white and white-spotted gray) in that they contain larger phenocrysts (they also include some phenocrysts of augite), and they both have a spherulitic texture, which is a common devitrification

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texture found in impact glasses (French, 1998) This texture is very prominent in sample GS-21-00 that it is even discernable in hand specimen (above plate 9.5) and is best seen in plate 18, which is a SEM composition image of GS-13-00. Plates 1418 are images of GS-23-00 is an altered glass breccia, which differs from the glass breccias found southeast of the central peak mainly in that it is clast poor and contains pyroxenes. Sporadically brecciated and comminuted in cavities and veins are pervasive through out the sample (plates 14 and 15). A large, cm-size porphyritic volcanic clast (andesite?) can be seen in plates 16 and 17. CIPW Norms and TAS Identification Sample Number: GS1300 (Porphyritic Black Glass) IUGS TAS Name: High-K Rhyolite Mineral Wt Norm quartz 21.8183 orthoclase 26.6787 plagioclase 41.2943 (albite) (34.3628) (anorthite) (6.9315) diopside 2.2961 (wollastonite) (1.1344) (enstatite) (0.4031) (ferrosillite) (0.7586) hypersthene 3.8293 (enstatite) (1.3287) (ferrosillite) 2.5006 magnetite 0.8869 ilmenite 1.0143 TOTAL 100.3185

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Sample Number: GS2100 (Black Glass) IUGS TAS Name: Medium-K Dacite Mineral Wt Norm quartz 46.6879 corundum 8.8344 orthoclase 8.8203 plagioclase 21.0599 (albite) (4.9676) (anorthite) (16.0924) hypersthene 11.6275 (enstatite) (7.3608) (ferrosillite) (4.2667) magnetite 1.2696 ilmenite 1.7008 TOTAL 100.0004 Sample Number: GS2300 (Altered Black Glass BrecciaClast poor) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 34.1272 corundum 0.3107 orthoclase 17.0908 plagioclase 42.4155 (albite) (31.2455) (anorthite) (11.1701) hypersthene 3.6938

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(enstatite) (0.7727 ) (ferrosillite) (2.9212) magnetite 0.8996 ilmenite 1.4634 TOTAL 100.00 View a list of the samples Choose samples by appearance Choose samples by location

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Graywackes (Plate Set 8) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-12 and GS-28 Graywackes SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-12-00 79.24 0.142 14.02 0.94 0.105 0.434 0.018 2.667 2.364 99.933 GS-28-00 66.53 1.473 25.12 6.31 0.439 0.186 0.031 0.221 0.421 100.73 Field Photos 1 Plate 1 A weakly to moderately indurated graywacke (sample GS-12-00) found in an intermittent drainage stream in the eastern part of the structure. Photomicrographs, SEM, Microprobe, and X-ray maps 2 3

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PPL and XPL 15 x images of GS-12-00 graywacke. Plates 2 and 3 are overall textural images of GS-12-00. This sample contains angular grains of plagioclase feldspars and quartz that are poorly sorted in a matrix of various clasts of tuffaceous materials, siltstone clasts, micritic mud clasts, clays and oxides. View a list of the samples Choose samples by appearance Choose samples by location

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Tuffaceous Carbonate (Plate Set 16) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-29 and P8-2-5-90 Tuffaceous Carbonate SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-29-00 30.4 1.646 5.669 2.45 0.362 37.91 0.251 0.292 0.932 79.913 P8-2-5-90 19.2 1.448 5.79 1.929 0.846 42.28 0.277 0.382 0.292 72.447 Hand Samples 1 Plate 1 a high resolution scan of sample GS-29-00, a tuffaceous carbonate billet. The billet is roughly one and a half inches in length. Photomicrographs, SEM, Microprobe, and X-ray maps 2 3 PPL and XPL 15 x images of a tuffaceous carbonate rock. Plates 2 and 3 are images of a tuffaceous carbonate GS-29-00 and P82-5-90 found just southeast and southwest (respectively) of the central peak. Abundant fossil fragments and tuffaceous material and

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volcanogenic materials can be seen throughout the sample. Algal fossils, bryozoa, pelecypods (?) are the most abundant fossils found in these samples. Laths of plagioclase are abundant amongst the clast and they all exhibiting undulatory extinction indicating that they have been subjected to stresses subsequent to their formation. View a list of the samples Choose samples by appearance Choose samples by location

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Chert (Plate Set 12) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-16 and GS-26 Chert SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-26-00 78.42 0.143 17.85 1.258 0.082 0.097 0.016 0.285 1.154 99.302 Field Photos 1 Plate1 a photograph of an outcrop of a chert body which exhibits areas with a greenish coloration. Hand Sample 2 Plate 2 a high resolution scan of sample GS-26-00, a tan colored sandy chert billet with pervasive veins of chalcedony. The billet is roughly one and a half inches in length.

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Photomicrographs, SEM, Microprobe, and X-ray maps 3 4 PPL and XPL 15 x images of sample GS-26-00 a sandy chert. Plate 3 and 4 are images of a sandy chert with veins of chalcedony from the southwest part of the structure. The sample appears to consist mainly of precipitated quartz crystals that have a brownish staining or amorphous material coating them. View a list of the samples Choose samples by appearance Choose samples by location

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Green Tuffaceous rock (Plate Set 14) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-20 Green Tuff SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-2000 64.23 0.981 16.07 6.208 1.555 4.59 0.153 4.054 2.244 100.08 Field Photos

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1 2 Plates 1 and 2 are photos of an outcrop of a moderately indurated greenish tuffaceous material. Photomicrographs, SEM, Microprobe, and X-ray maps 3 4 Plates 3 and 4 this thin section could not be properly cut due to expansion due to water interaction and friability issues. Phenocrysts of plagioclase feldspar are enclosed in a matrix of highly altered ash, volcanoclastics and clay that appears as an amorphous yellowish green material under plane and crossed-polarized light. View a list of the samples

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Choose samples by appearance Choose samples by location

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Shocked Graywackes, Siltstones and Sandstones (Plate Set 6) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-09, GS-24, and P8-2-2-90 Sandstones, siltstones and Graywackes SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL P8-2-2-90 79 0.127 13.98 0.714 0.121 0.6 0.015 3.392 2.966 100.91 GS-09-00 69.74 0.786 15.4 3.595 0.163 1.663 0.046 5.753 3.383 100.52 GS-24-00 94.76 0 0.01 4.888 0.005 0.013 0.008 0 0.044 99.728 Field Photos 1 2 3 4 5 Plates 1-5 Outcrops of disturbed Gatuncillio formation (graywackes and siltstones and sandstones) of the central peak. This rock type occurs at the waters edge on the northeast, northwest and southwest side of the central peak and in an intermittent drainage stream (Plate 4) near the summit of the peak. Hand Samples

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6 7 Plate 6 and 7 Hand specimens showing the fractured and chalky texture typical of the lithologies of the central peak. The clip on the pencil cap is about one inch in length. Photomicrographs, SEM, Microprobe, and X-ray maps 8 9 10 11 12 13 14 15 PPL and XPL images of graywackes, siltstones and sandstones from the central feature exhibiting annealed "sugar" textures and prominent sub-planar to planar fractures. Plates 8 and 9 are 100 x images of an annealed graywacke from the central peak. Note the lack of matrix and the sub-hexagonal shapes of the grains. Plates 10-13 are 15 x images of sandy siltstones of Tres Dedos Island west of the central peak. In plates 12 and 13 a slightly shocked phenocryst of plagioclase can be seen exhibiting undulatory extinction and possibly diaplectic areas. Note the subparallel lath-like voids of as yet, undetermined origin, which are best portrayed in SEM backscatter imagery in plates 14 (250 x) and 15 (500 x). The dark shades of gray are quartz and the lighter gray areas are alkali and plagioclase feldspars and the white areas were revealed to be a Ce-bearing phase of unknown origins. View a list of the samples Choose samples by appearance Choose samples by location

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Various Volcanic Rocks (Plate Set 2) View a list of the samples Choose samples by appearance Choose samples by location Samples GS-04, GS-05, GS-07, GS-08A and P8-2-1-90 Various Volcanics SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-04-00 63.73 0.88 18.9 8.369 1.37 2.51 0.24 2.18 2.76 100.91 *GS-05-00 25.41 0.13 5.26 1.573 1.88 65.1 0.08 0.21 0.41 100.03 GS-07-00 59.73 1.07 16.8 7.762 2.47 6.73 0.25 3.6 1.73 100.2 GS-08a-00 52.09 0.99 19.4 9.63 4.78 10.5 0.15 2.7 0.68 100.96 P8-2-1-90 56.1 1.2 17.1 10.83 2.9 6.11 0.44 4.04 0.98 99.738 May have been contaminated or misread Field Photos 1 2 GS-07-00 basalt found on the northern side of Dos Burros Island. The pencil is roughly six inches in length. Photomicrographs, SEM, Microprobe, and X-ray maps

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3 4 5 6 7 8 9 10 11 12 PPL and XPL images of various basaltic andesites and andesites from the Gatun structure. Plates 9 and 10 are at 40 x magnification while all others are at 15 x. Plates 3 and 4 represents an porphyritic andesite (GS0400) from the western most part of the structure. Many of the plagioclase phenocrysts in this particular sample are highly fractured, exhibit undulatory extinction and may have undergone partial diaplectic transformation into maskelynite. This sample, for all intents and purposes, appears to be an andesite, but in light of the possible presence of maskelynite, it may in fact be an impact melt rock. It has been included in this section until further proof comes to light that it is impact induced. Plates 5 and 6 are images of a porphyritic basaltic andesite (GS0500) from the southeast side of Congo Island. Plates 7 and 8 are of a basaltic andesite (GS0700) from Dos Burros Island that contains a carbonate clast with a fragment of a possible fossilized pelecypoda (circled in red in the upper center of both PPL and XPL images). Plates 9 and 10 are 40 x close-ups of the fossil fragment. Note the reaction rim around the clast (probably due to de-carbonation). Plates 9 and 10 are of an andesite (GS08a00) from Potra Island that has abundant carbonate clots (tan in PPL and brown in XPL). CIPW Norms and TAS Identification Sample Number: GS0400 (Porphyritic Andesite possible impact melt rock) IUGS TAS Name: High-K Dacite Mineral Wt Norm quartz 28.5595 corundum 7.7626 orthoclase 16.3106 plagioclase 30.8986 (albite) (18.4465)

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(anorthite) (12.4521) hypersthene 13.3074 (enstatite) (3.4123) (ferrosilite) (9.8951) magnetite 2.4271 ilmenite 1.6713 TOTAL 100.9371 Sample Number: GS0700 (Andesite) IUGS TAS Name: Medium-K Andesite Mineral Wt Norm quartz 11.9364 orthoclase 10.2092 plagioclase 54.9550 (albite) (30.4189) (anorthite) (24.5361) diopside 7.3736 (wollastonite) (3.6760) (enstatite) (1.5194) (ferrosilite) (2.1782) hypersthene 11.2527 (enstatite) (4.6240) (ferrosilite) (6.6287) magnetite 2.2471 ilmenite 2.0293 TOTAL 100.0033

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Sample Number: GS08a00 (Basaltic andesite) IUGS TAS Name: Medium-K Basalt Mineral Wt Norm quartz 1.9081 orthoclase 3.9879 plagioclase 61.0898 (albite) (22.6390) (anorthite) (38.4508) diopside 10.8709 (wollastonite) (5.4975) (enstatite) (2.7697) (ferrosilite) (2.6037) hypersthene 17.5151 (enstatite) (9.0280) (ferrosilite) (8.4871) magnetite 2.7671 ilmenite 1.8631 TOTAL 100.002 View a list of the samples Choose samples by appearance Choose samples by location

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White Glass (Plate Set 3) View a list of the samples Choose samples by appearance Choose samples by location Sample GS-06 White Glass SiO2 TiO2 Al2O3 Fe Total MgO CaO MnO Na2O K2O TOTAL GS-06-00 78.6 0.21 12.7 1.324 0.09 0.98 0.02 3.25 2.75 99.911 Field Photos 1 2 3 Massive dike-like bodies of white glass found on the southeast side of Mula Island. The pencil is roughly six inches in length. The body appears to be dipping to the SSE parallel to this dip is the apparent flow direction of the flow features in this glass that can be clearly seen in out crop and in hand sample. Hand Samples

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2 3 4 Plates 2 and 3 are photographs representing a partially polished hand specimen of GS-06-00, a hypocrystalline white glass. Plate 4 is a high resolution scanned image of both sides of the sample (scale is not included in this image, but is provided in the previous images). The sample is approximately 2 inches in length. Reflective yellowish-silver opaque minerals can be found throughout the sample, but most have been aligned according to the strong flow-banding that can be easily seen in these photographs as contrasting alternating bands of white and black. Photomicrographs, SEM, Microprobe, and X-ray maps 5 6 7 8 PPL and XPL 15 X images (1 and 2) and 40 X images (3 and 4) of glass breccias. Plates 5 and 6 represents the overall texture of the white glass. Plagioclase feldspar and some sporadic pyrite crystals are enclosed in a hypocrystalline matrix of flow banded siliceous and feldspathic glass. The phenocrysts of both of these recognizable phases commonly align themselves to the apparent direction of flow. Plates 7 and 8 are 40 x close-ups of one of the many flow bands in the white glass. This band is composed of plagioclase feldspar and pyrite. CIPW Norms and TAS Identification Sample Number: GS0600 (White Glass) IUGS TAS Name: Medium-K Rhyolite Mineral Wt Norm quartz 46.2914 corundum 2.5949

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orthoclase 16.2515 plagioclase 32.3623 (albite) (27.5005) (anorthite) (4.8618) hypersthene 1.6421 (enstatite) (0.2242) (ferrosilite) (1.4180) magnetite 0.3842 ilmenite 0.3988 TOTAL 99.9252 View a list of the samples Choose samples by appearance Choose samples by location

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ANALYTICAL METHODS Detailed field investigations were conducted during a July 2000 field session. Outcrops and unaltered lithologies were rare to non-existent due to the effects of tropical weathering and the dense cover of a triple-canopy rainforest. My colleague, Thomas J. Carey, and I collected thirtythree rock samples from the Gatun site. Eleven samples collected by R. H. Stewart in 1990 and 1998 were also used in this study. The samples were trimmed to remove oxidized and altered areas; one slab was billeted for thin sections, and another was crushed, sonified in deionized H2O, and powdered for chemical analysis using a tungsten carbide ball mill. Polished thin sections of each sample were prepared for examination by petrographic microscope, as wellas analysis by scanning electron microscopy (SEM), and electron microprobe. JEOL 5510 SEM, and a JEOL JXA-8800 SuperProbe that are part of the Florida Center for Analytical Electron Microscopy ( FCAEM ) at Florida International University (Miami), were utilized in this study. Accelerating voltage on the SEM was15 kV, and both secondary and backscatter imaging were utilized. Preliminary mineral compositions were acquired using a highresolution Energy Dispersive X-ray Spectroscopy (EDS) system at a 25-35 micrometer spot size. FIU microprobe operating conditions were an accelerating voltage of 15 kV, a 20nA current, and a spot size of 1-2 micrometers for wavelength dispersive (WDS) analysis. Counting times were 10s for each element, with a background count of 5s. Analyses of glassy phases were obtained under similar voltage and current conditions, but utilizing a defocused beam (10 micrometer diameter) to minimize volatile losses.

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Structural assessments of possible maskelynite (amorphous feldspar) in some Gatun samples was conducted at CeSMEC (Center for the Study of Matter at Extreme Conditions) at FIU using Raman spectroscopy. The Raman system consists of a 5 w Ar laser, which empowers a Tisapphire laser that is tunable to 950 nm. Scattered light from the sample is fed into a Kaiser holographic band pass spectrometer, with an Andor 2D, silicon-based CCD detector. Measurements were made with the Ar laser at 1.8 w, the Ti-sapphire laser between 20-23 mw, 5 second counting times, and 30 accumulations. Bulk-rock major and trace element compositions were measured by Direct Current Plasma Emission Spectrometry, using a FISONS Spectra-Span VII (DCP-AES), following sample digestion via a modified LiBO2 flux-fusion method (see Tenthorey et al. 1996 ). Loss on ignition (LOI) Sample powders were devolatilized and oxidized before analysis via heating to 1050 C for fifteen minutes in a muffle furnace, and Loss on Ignition (LOI) percentages were recorded. Solutions were diluted 250:1 for trace element analysis (0.2 g sample in 50 ml solution), and diluted a second step (2.5 ml Aliquots of the sample solution to 50 ml; 5000:1 total dilution factor) for major element analysis. DCP runs were calibrated using a combination of USGS standards: RGM-1 (rhyolite), SDO-1 (shale), AGV-1 (andesite), MAG-1 (marine mud), SDC-1 (schist), BIR-1 (basalt), COQ-1 (carbonitite); and a Japanese Geological Survey standard JLs-1 (limestone). Standard powders were prepared and analyzed along with Gatun samples to generate working curves. Based on replicate analyses of rock standards in the USF lab over time, overall uncertainties are <1% for Si and Al, % for Mg, Ca, and Fe, and -3% for Mn, Na, K, and Ti. The precision for trace elements varies from -15%.

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RESULTS 1. Field Observations and New Samples 2. Petrography 3. Microprobe Analysis 4. Raman Spectroscopy 5. Bulk Chemistry Majors and Traces 1. Field Observations and New Sampling During field studies and sample reconnaissance in July of 2000, I and my field assistant, Thomas J. Carey, confirmed the concentric layout of the site, and thoroughly resampled the structure ( Figure 6a ). We identified several unsampled and unmapped lithologies (the GS series samples), most of which were exposed in intermittent drainages and in rare, erosion-resistant outcrops. These unsampled lithologies included melt-bearing breccias (impact melt rocks and/or suevites?), glasses or hypocrystalline lithologies, and a lithic breccia consisting predominantly of andesite and mineral fragments. The melt-bearing lithologies occurred near to the periphery of what is believed to be the rim of

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the structure. Two samples with a tuff-like appearance, GS-06a-00 and GS-11-00 were found on opposites sides of the structure, but equidistant from its center ( Figure 6a ). These lithologies occur as large boulders or blocks, that may represent ejected suevites. Another melt-bearing sample, GS-22-00 ( plates 15.1-3 ), was taken from a low lying, dike-like feature on the southwestern margin of the structure. The sample is a breccia with a matrix of green glass, and includes light gray to green clasts that are plastically deformed and exhibit indications of flow ( plates 15.4-8 ). Of the five glass samples found in the Gatun structure, two came from near the apices of the inner and outer ridges: a white glass ( GS-06-00 ) was found high up on Mula Island in the outer northwest region of the structure; and a porphyritic black glass ( GS-13-00 ) was found in the eastern part of the structure. The other three were found in lower elevation regions: one near the center ( GS-15-00 and GS-17-00 ), two from southwest of the center ( GS-21-00 and GS-22-00 ). There is a possible sixth glass, also found in the southwest, ( GS-23-00 ) that may actually represent a clast-poor breccia. Massive blocks of a lithic breccia (sample GS-14-00: plates 10.1-5 ), were found SSE of the center of the structure, in contact with a white-spotted, gray glass ( GS-15-00 ). The clasts in this fragmental breccia are similar to some of the local volcanic rocks (samples GS-18-00 a altered, gray andesite; and GS-18a-00 a reddish, altered andesite). Near the center of the structure, chalky sandstones and siltstones of the Gatuncillio formation are associated with a carbonate rock cemented with zeolites (as described by Stewart). In this area, we collected a sample preserving a discrete contact between carbonate rock and highly altered silicate rock. Upon first inspection this rock, sample GS-19-00 ( plate 13.1 ) appears to be an aphanitic basalt with a highly altered, brownish-yellow reaction rind, but the dark, seemingly

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unaltered, portions of the sample react violently with 10% HCl, indicating nearly pure calcite. Proximal to the site of sample GS-19-00, is an unmapped, but previously sampled, outcrop of anomalous limestone (samples GS-30-00 and P8-2-7-90 ). The rocks are beige in color, heavily recrystallized and have a spotted appearance (i.e., brownish amorphous-glassy inclusions). Trace algal fossils identify them as sedimentary in origin, however these limestones seem to be unusually resistant to weathering and alteration when compared to the local carbonate rocks ( plate 17.1 and 17.2 ). 2. Petrography I have divided the Gatun Structure samples into several lithologic classes: (1) Glasses and melt-bearing breccias (including sub-class: suevite?) (2) Lithic breccias (fragmental breccias) (3) Shocked carbonates (4) Non-shocked carbonates (5) Siliciclastic rocks (6) Volcanics For a complete petrologic description of all the samples and their features see Appendix A

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Glasses and Melt-Bearing Breccias Many of the breccias found in the Gatun structure can be described as glass breccias, consisting almost entirely of poorly sorted, amorphous to opaque clasts. It should be noted that when the term "glass" is used in this context, it is referring to any of the lithologies or fragments that consist of translucent to opaque, hypocrystalline to hyaline material. Samples GS-01-00, GS-03-00, GS-25-00, P8-2-4-90, 2-14-95-4 and 2-14-95-5 are glass and melt-bearing breccias found near to the central peak structure. Sample GS-08-00 is a highly altered glass breccia that was found submerged on the north side of Portra island, in the extreme northern part of the Gatun structure ( Figure 6a ). Many of the glassy clasts are themselves highly fragmented, angular to sub-angular, and have been intruded by sporadic veinlets of brecciated glass and probable hydrothermal minerals (quartz, feldspars, zeolites, pyrite and sphalerite: plate 1.29 and 1.1-Si to 1.1-S ). Clasts are almost entirely opaque, in some cases exhibiting a swirled fabric, possibly indicating melting and / or flow ( plate 1.23 and 1.24 ). Rims of some black clasts, and many beige clasts, exhibit a highly vesiculated appearance ( plate 1.19-28 ) and may be the result of zeolite replacement. Sample GS-22-00 differs from other glass and melt-bearing breccias by its coloration (emerald green w/ beige and green clasts), a higher proportion of matrix, and clasts that exhibit plastic deformation. In thin section, boundaries between matrix and clasts are not discrete, which gives the sample an overall igneous appearance. GS-22-00 includes abundant, intensely deformed, vesiculated and flow-banded (fiamme structure?) greenish-beige, yellowish beige and grayishgreen clasts, ranging from a few millimeters to several centimeters in diameter. Included with these clasts are rare, undeformed igneous rock fragments (basalt or basaltic andesite) ( plate

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15.9 and 15.10 ). Bands of beige, grainy, partly crystalline areas, are abundant in the sample, and may represent intensely deformed and/or partially melted siltstone fragments ( plate 15.15 ). Globules of a reddish oxide (hematite?) are common throughout the sample and are associated with areas of intense plastic deformation. Phenocrysts of plagioclase in GS-22-00 are highly fractured and exhibit undulose extinction. All of these fragments are enclosed in an emerald green, flow-banded, hypocrystalline matrix that is highly vesiculated and contains abundant cavity fills of microcrystalline quartz (chalcedony) ( plate 15.16-22 ). The dominant green coloration of this specimen may result from abundant microcrystalline chlorite, pumpellyite and / or zeolite. In some cavity fills, opaques exhibiting an anomalous yellowish-orange coloration occur associated with euhedral apatite and chlorite ( plates 15.23 and 15.24 ). GS-23-00 also differs from the glass breccias found southeast of the central peak. It is an altered, clast poor breccia containing basaltic or basaltic andesite fragments, plagioclase feldspar grains and rare clinopyroxene (augite) grains (this was the only glass breccia found with intact pyroxenes) in a dark brown to black, hypocrystalline matrix that contains sporadically brecciated and comminuted glass in cavities and veins ( plate 9.14 and 9.15 ). The semibrecciated matrix contains indications for flow, devitrification, and alteration into zeolites, which are best seen in plane-polarized light. The specimen exhibits abundant veinlets and cavity fills of microcrystalline quartz and an unknown phase (possibly a zeolite). A large, cm-size altered porphyritic igneous clast (andesite?) can be seen in the thin section ( plate 9.16 and 9.17 ). Plagioclase feldspars in this clast are highly fractured and exhibit undulose extinction. Flow banding in the matrix follows the boundaries of large clasts, indicating that the clasts were part of the sample while it was behaving plastically, or when it was partially molten.

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Zeolite Tuff or Suevite? Sample GS-06a-00 includes three types of clasts of varying color and degree of melting and possibly shock. The most prominent clasts are turquoise-blue in color and appear to be partially devitrified glass containing microlites of feldspars (zeolites?) and rare calcite. This calcite may be the product of melting under extreme pressure, and it exhibits liquid immiscibility effects with the surrounding feldspathic melt ( plate 4.40-43 ; see the discussion section ). The less abundant beige clasts are highly vesiculated, and commonly contain spherules of brown glass, altered plagioclase feldspars, augite, calcite, magnetite and cavity fills, or cored inclusions. These clasts also exhibit igneous textures and flow features, and they are clearly more intensely deformed than the blue clasts. Some of the beige clasts appear to consist entirely of cored inclusions, melt blebs? and/or spherules of brown glass ( plate 4.27, 4.28 and the X-ray images of spherules ). The cavity fills, or cored inclusions, are circular to oblate in shape and contain plagioclase feldspar crystals and possibly zeolites(?). These features are best seen in plate 4.20-22 surrounding an altered plagioclase feldspar. The third type of clast can only be distinguished under the microscope. These are yellow in color and consist of plagioclase feldspar, augite, calcite and magnetite. These clasts are the least deformed of the three, but are the most alteredlooking materials in the sample. Some of the yellow clasts contain, or are in contact with phenocrysts of altered plagioclase feldspar. These three types of clasts are enclosed in a frothy matrix of glass, rock and mineral fragments with sporadic phenocrysts of shocked and deformed plagioclase feldspar (many of which exhibit partial to fully amorphous behavior), augite, magnetite, ilmenite and three types of glass spherules (glass, fluid-drop and lithic). Other, rare clasts in this sample are rare fossil fragments of bryozoans ( plates 4.44 and 4.45 ) and pelecypods ( plates 4.46 and 4.47 ). Both the blue and beige clasts, including the mesostasis, contain phenocrysts of altered

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feldspars that are of particular interest under cross-polarized light. These feldspars exhibit a patchy alteration pattern of nonto extremely low birefringent areas (an isotropic mineral? diaplectic glass?)( plates 4.10-26 and 4.32-39 ) that are superimposed on the clearly crystalline albite twins of the original plagioclase feldspar lath ( plates 4.11, 4.12, and 4.14 ). Incipient melt effects are commonly seen in association with these altered feldspars, which exhibit some mixing with the mesostatial material and have an apparent direction of flow ( plates 4.13-16 and 4.1-Al ). These incipient melts, associated only with pheoncrysts of plagioclase feldspars, appear as a swath or wave-like feature coming off the crystal lath ( plates 4.13, and 4.14 ). The most distinctive aspect of the the matrix in these samples are that they exhibit intense deformation and flow effects. Features in these samples bear resemblances to melting effects documented in impactites from Ries, Manson, Gardnos and Chesapeake Bay ( Koeberl and Anderson, 1996; French et al., 1997; Poag, 1999 ). Overall, sample GS-06a-00 bears a close resemblance to the suevites of the Ries impact structure (especially in hand specimen). The Ries suevites like the Gatun sample GS-06a-00, has a tuffaceous texture in which glassy clasts are enclosed in a matrix of pulverized rock and mineral fragments. The Glasses The glasses of the Gatun structure come in three varieties: (1) flow-banded white glasses (2) white-spotted gray glasses (3) dark or black glasses

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All are predominately hypocrystalline and have a strong flow-banded texture (plates 3.5-8 9.8-9 and 11.8-9 ). Schlieren divide the glasses into zones rich in phenocrysts of plagioclase feldspar and opaques. Phenocrysts are strongly aligned to the apparent direction of flow. The black glasses contain larger phenocrysts, sometimes including augite, and they commonly exhibit a spherulitic texture, which is a common devitrification texture in impact glasses ( plates 9.10, 9.12 and 9.18 ) (French, 1998) This texture is so pervasive and prevalent that it is even discernable in some hand specimens ( plate 9.5 ). Lithic and Fragmental Breccias (?) Sample GS-14-00 is a fragmental lithic breccia, and it is characterized by poorly sorted fractured fragments of igneous, siliciclastics, and rare fragments of carbonate rocks. Altered igneous clasts consist of phenocrysts of plagioclase feldspar, altered amphibole (black both in PPL and XPL), magnetite, chlorite and quartz in a re-crystallized matrix of quartz and feldspar. These fragments, which are petrographically similar to the andesite samples GS-18-00 and GS-18a00 make up over 90% of the clast population. The fragments of igneous components can be easily discerned in plane-polarized light ( plates 10.11 and 10.12 ). Mineral fragments of plagioclase and alkali feldspars, altered amphiboles, quartz, opaques and rare kinked biotites also occur ( plates 10.23-25 ). Mineral fragments are angular to sub-angular and show undulose extinction. Sporadic veinlets of fibrous zeolites and calcite occur throughout the sample. Of the breccias examined, only GS-14-00 bears strong similarities to fragmental igneous rocks. It is identified as a lithic breccia based on the occurrence of country rock fragments.

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Shocked and Unshocked Carbonate, clastics and Volcanic Rocks As noted in the geologic summary the country rocks of the Gatun Lake area include greywackes, tuffs, and carbonates. Carbonate rocks ( GS-30-00 and P8-2-7-90 ) found near the central peak, show recrystallization, areas of vitrification (~1 mm diameter glassy blebs can be seen in hand sample plate 17.3 ) and dramatic grain-size reduction compared to the locally undisturbed carbonates. Viewed under the microscope, the vitreous blebs are interconnected cavities containing glassy and brownish amorphous material. The calcite and amorphous materials have very discrete boundaries under crossed nicols due to the opaque / isotropic behavior of the brown phase ( plate 17.4-9 ). Sample GS-19-00 may include a contact between carbonate rock and a siliceous melt ( plates 13.1, 13.4 and 13.5 ). The siliceous material appears to be highly altered and vesiculated. The carbonate exhibits numerous veinlets and pockets of zeolites ( plate 13.6-9 ), especially close to the silicate contact. The carbonate is foraminiferal, sparry and micritic calcite that includes altered volcanoclastic debris. Clasts of feldspar have been replaced by zeolites and / or calcite, but still maintain lath-like shapes ( plates 13.2 and 13.3 ). Numerous cubic grains of pyrite are found in the matrix, and as inclusions in the microfossils. The carbonate-silicate contact is sharp. Silicates consist of vesiculated, very fine-grained volcanoclastics with sporadic, highly altered feldspar laths ( plates 13.10 and 13.11 ). This part of the rocks is stained from oxidation, and occasionally contains clots of calcite. Greywackes, siltstones and sandstones from the central feature exhibit an annealed "sugar" texture with prominent sub-planar to planar fractures. Annealing is indicated by the lack of

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matrix and the sub-hexagonal shape exhibited by the crystals ( plates 6.8 and 6.9 ). Feldspar and quartz are the dominant phases, and almost all of these grains include small subparallel lath-like voids of undetermined origin ( plates 6.14 and 6.15 ). Although there appears to be virtually no matrix, some areas between grains contain clays and oxides. Slightly shocked phenocrysts of plagioclase exhibiting undulose extinction and possible diaplectic areas exist in vugs, veins or pore spaces ( plates 6.12 and 6.13 ). The typical volcanic rocks of the area are basalts and basaltic andesites, with a phenocryst assemblage of plagioclase, or alkali feldspars, olivine, pyroxenes, magnetite or titano-magnetites in a matrix of oxides, feldspar microlites and/or glass. Three volcanic samples ( GS-10-00, GS-13a-00 and GS-27-00 ) differ from the rest in that they contain pyroxene necklaces, or pyroxene-quartz coronas, a reaction texture commonly formed around a xenocryst of quartz in reaction with a more mafic melt ( plates 7.13-24 ). Other rare and unusual occurrences in the volcanic rocks include xenoliths of intact, fossiliferous carbonate rock ( plates 2.7-10 ). 3. Microprobe Analysis Electron Microprobe analyses were conducted to verify phase identification; to identify unknown phases that could not be resolved optically; and to obtain compositional data on glasses, sample matrices and unusual features (spherules, diaplectic glasses, pyroxene necklace structures, etc.). Microprobe results are compiled in Tables 2-15 and have been organized by sample designation and / or features therein. A summary of these results and FIU probe data for several rock and glass standards are also listed in Table 1

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The opaque, hypocrystalline glasses which are found in many Gatun breccia and glass samples are remarkably consistent in their compositions (are all some type of feldspathic glass; see Tables 2-15). Thus, it is likely that the glasses and melt-bearing breccias all have a similar origin. The samples GS-06a-00 and GS-22-00 include glasses, spherules, decomposing spinels(?) and zeolite phases. GS-06a-00 contains labradorites with nonto low birefringent patches that exhibit textural indications of partial melting. Na is concentrated in the nonto low birefringent areas of these crystals, some of which have readily altered into clays. The chemistry of these zones are consistent with analcime, a Na-rich zeolite mineral ( Deer et al.,1993 ). The spherule rim compositions in GS-06a-00 do not conform to any known mineral phase, and are very Fe and Ti-rich, with significant amounts of CO2 possibly suggesting that they may have been generated by melting and mixing of a carbonate and Ti-bearing oxide phase. GS-22-00 also includes abundant reddish blebs, which appear to be heterogeneous, multi-phased, mixtures of an Si, Al and Fe-bearing phase and Ti-bearing spinel phases. One particular spinel (diamond)shaped grain exhibited distinct chemical segregations of an almost pure Si, Fe, and Al phase surrounding it ( plates 15.25-28 and 1-Si thru 2-Fe ). Some of the Fe-rich and Ti-rich areas had Fe and Ti concentrations as high as 74% and 71.5% respectively (hematite-ilmenite). An analyzed pyroxene-quartz corona in GS-10-00 ( plates 7.13-24 ) includes a fractured and annealed quartz crystal surrounded by brown, Fe-rich feldspathic glass, with a rim of pyroxenes. The chemistry of the glass suggests the mixing of the quartz core and the mesostasis of the sample, and the pyroxenes are diopsides. Figure 9 a plot of SiO2 vs. FeO shows that the glass in the corona is consistent with a mixture of quartz and the approximate bulk composition of GS-10-00.

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GS-19-00 and GS-30-00 / P8-2-7-90 are two highly altered carbonates with high concentrations of SiO2. Silica-rich areas in GS-19-00 exhibit chemistries consistent with the zeolites analcime and heulandite, both of which suggest hydrothermal alteration of a plagioclase precursor. Silicarich areas (blebs) in GS-30-00 show the highest concentrations of Mg and Al (33.39% and 4.46% respectively), but there is no indication or trace of dolomite as a phase. 4. Raman Spectroscopy of Plagioclase Feldspars in GS06a-00 (Suevite) The Raman spectra of the plagioclase feldspars (mostly labradorite) in sample GS-06a-00, when compared with the spectra of a gem-grade labradorite from Madagascar, reveals that many plagioclase feldspars in GS-06a-00 have undergone amorphization and that diaplectic glasses (maskelynite) are present ( Figure 7 ). The peaks for the labradorite standard are at 288, 411, a major split peak near 500 (483, 510), 571, a split peak near to 800 988, and 1270. The spectral patterns produced from the gem-grade labradorite shows all the major peaks consistent with labradorite, while the two patterns from sample GS-06a-00 exhibit peak shifting, broadening, enhanced backgrounds and partial to complete peak degradation with the main peak near 500 still persisting. The peaks that have been shifted, but remain after amorphization are at 300 (288), 392 (411), 484 (500), 1100 (800), 1200 (988) and 1280 (1270) (the bolded parenthetical numbers represent the peaks in the pattern of the labradorite standard that the shifted peaks in the sample correspond to). These effects are consistent with amorphization of plagioclase feldspar (see Daniel et al., 1997 ). For more information on the Raman effect, or to view a Caltech database of minerals analyzed by Raman spectroscopy see THE RAMAN EFFECT and

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Database of Mineral Raman Spectra respectively. 5. Bulk Chemistry: Major and Trace Elements Major Element Chemistry DCP major and trace element data for thirty GS samples, the eleven samples collected by R. Stewart, and three Panamanian arc samples (donated by Dr. Marc Defant) are reported in Table 16a and 16b CIPW norms for all samples are reported in Table 17 The Gatun suite can be divided into several chemical groups: (1) Glasses and melt-bearing breccias (2) Volcanics (3) Lithic breccias and altered igneous rocks, (4) Carbonates (5) Country rock carbonates (6) The siliceous component in carbonate sample GS-30-00 I have compared our whole-rock DCP results with data for glasses and spherules from the electron microprobe in several variation diagrams described below (Figures 10-14). Figures 10 and 11 are Harker-style variation diagrams that plot SiO2 vs. Al2O3 and CaO. On

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these plots, it is clear that volcanic rocks associated with the Gatun area and the Panamanian arc are not similar to the glasses and melt-bearing breccias of the Gatun Structure. In Figure 10 whole rock and probe results for the glasses, melt-bearing breccias and lithic breccias form mixing arrays between a quartz-rich end member (tuffaceous sandstones and siltstones of the Gatuncillo or Las Cascadas Formation?) and plagioclase feldspar, specifically labradorite, which is the average composition feldspar occurring in the country rocks of the Gatun Lake. Spherules and the siliceous component in GS-30-00 form a different array, suggesting possible mixing between the melt found in GS-06a-00, the spherule host rock, and magnetite, the primary oxide phase in this sample. The analyzed volcanic rocks form a cluster on this diagram that is distinct from either Gatun structure array. Sample GS-06a-00 (suevite?) plots near the intersection of the volcanics, the spherule/ carbonate array and the glass and melt-bearing breccia array, suggesting it may approximate a mixture of all of these components. Figure 11 ( SiO2 vs. CaO) also shows a distinction between the volcanic rocks and the Gatun structure data arrays, though the distinction is more subtle, as the glasses and the melt-bearing breccias seem to form en echelon arrays distinct from that of the volcanic rocks, and the spherule array crosses the volcanics trend. The glasses and volcanics actually vary similarly, though the Gatun glasses and breccias are distinctively richer in SiO2. The spherules form two clusters: one representing larger spherules that have plagioclase / clay cores, and the other including the smaller spherules, and the brown glass that rims the larger ones. The plagioclase cores of the larger spherules are clearly biasing these analyses toward the feldspar-matrix mixing array of the glasses and volcanics, while the smaller glassy spherules are recording the admixture of something like a titano-magnetite component. Figure 12 plots Na2O vs. K2O for Gatun structure samples and associated volcanic rocks. The Na2O / K2O ratio of Gatun glasses and melt-bearing breccias 1, while the local volcanic rocks

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are distinctly richer in sodium. The black glass GS-21-00 and suevite(?) samples GS-06a-00 and GS-11-00 have Na2O/K2O similar to or higher than other Gatun structure lithologies. Gatun structure samples plot as a trend that extends from somewhere near the origin, a Na and K poor phase (quartz carbonates, etc.). The high Na-K endmember is not consistent with a particular mineral, but may represent the overall composition of the local country rocks. Spherules also plot as a cluster on this diagram which may or may not extend toward a very high K2O mineral or rock. In Figure 13a a K2O-CaO-Na2O ternary, Gatun glasses and melt-bearing rocks form a cluster, suggesting they are relatively homogeneous with respect to alkaline elements. Local volcanics are relatively much richer in Ca, and form a differentiation trend on this diagram. Figure 13b an AFM diagram, also distinguishes Gatun structure rocks from local volcanics, in that the Gatun glasses and breccias contain almost no Mg. Two shocked Gatun carbonates lie on the MgO Fe Total axis, while others suggest mixing toward a component similar to the Gatun glasses. Other samples (GS-21-00, one of the two pyroxene-bearing Gatun glasses; the silicate / carbonate sample GS-19-00; the two possible suevites, and the tuffaceous carbonates from the Caimito formation) appear to reflect mixing between these Mg-poor and alkali-poor extremes in the Gatun suite. Figure 14 a plot of TiO2 vs. CaO examines the anomalous carbonates of the Gatun suite (GS19-00, GS-29-00, GS-30-00, P8-2-5-90 and P8-2-7-90), as well as samples of undisturbed Caimito Fm. All of these rocks include a volcanic silicate component: the proportion of this component increases approximately as CaO content decreases. The Caimito Formation samples form an array suggesting inputs of relatively Ti-poor, presumably tuffaceous, volcanic materials an inference that is consistent with sample petrography. However, Gatun structure carbonates form an entirely different array, extending toward a siliceous endmember with ~ 2.5

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wt.% TiO2. Whether this difference is the result of the mechanical admixture of a Ti-rich (spinel?) component. or some other process, is not clear. However, the carbonates from within the structure clearly differ from those from outside of the structure. Trace Element Chemistry Gatun glasses and the melt-bearing breccias show rather homogenous Sr concentrations of between 200-300 ppm, while the volcanics, typical of arc lavas, are both higher and more variable, ranging from 300-900 ppm. Ba in the glass and melt-bearing breccias varies from 700 to 2000 ppm, with an average of 1059 ppm, while the volcanics are overall lower (300-800 ppm Ba: average 640 ppm Ba). Similar patterns of Sr and Ba are seen in impact rocks and glasses of the Lake St. Martin structure and the Gardnos structure ( Reimold et al., 1990; French, et al.,1997 ).

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APPENDIX A: COMPLETE PETROGRAPHIC DESCRIPTIONS, PHOTOS AND PHOTOMICROGRAPHS Plates sets 1-17: Photos and Photomicrographs View a list of the samples Choose samples by appearance Choose samples by location Complete Petrographic Descriptions

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GS-01-00, GS-03-00, GS-25-00, P8-2-4-90, 2-14-95-4, and 2-14-95-5 Glass breccias (impact-melt breccia?) These samples consist of poorly sorted subrounded to angular clasts of black and beige-brown glass ranging from >1 mm to 5 cm. These samples are mainly fragment-supported breccias with <10 vol. % matrix. Many of the clasts are fractured and crosscut by veinlets filled with microcrystalline quartz, smaller glassy fragments, and secondary opaques, including sulfur and/or sulfides (pyrite and sphalerite). Flow banding can be seen with the unaided eye in some clasts, which appear to be a mixture of the black and beige-brown glasses. Thin Section The rock consists of slightly to strongly opaque isotropic clasts that contain some zoned and albite-twinned plagioclase feldspar (~ An60), some grains of which have under gone alteration (sericitized and/or converted into diaplectic glass). All the crystals observed have undulose extinction, indicating that they have been subjected to stress. The opaque clasts range from black, dark brownish black, or beige and dark brown to black clasts with beige rims. The clasts range in size from several millimeters to centimeters across, and the fragments are angular to sub-rounded. Many of the clasts are themselves strongly brecciated, and intruded by veinlets of glass fragments and/or hydrothermally emplaced quartz, feldspars, zeolites, pyrite and sphalerite). The black clasts are almost entirely opaque, and the swirled texture is sometimes evident, along with indications of flow banding in a few. The beige rims on clasts and the small beige clasts are highly vesiculated. These vesicles may be infilled with radial feldspar and quartz crystals, or microcrystalline feldspar, quartz or cristobalite. Some of the light beige clasts are made up entirely of microlites of plagioclase feldspar. Within some clasts, may be found zoned and albite twinned plagioclase feldspar (~ An60) with undulatory extinction.

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GS-04-00 Porphyritic Andesite Thin Section This sample is made up of phenocrysts of Carlsbad twinned feldspar (sanidine?), albite twinned plagioclase, clinopyroxenes that have altered into chlorite, serpentine, and subhedral to euhedral magnetite with reaction rims of hematite. The fine-grained matrix is almost glassy, and consists predominantly of microlites of feldspar and with abundant magnetite crystals. Many of the plagioclases are highly fractured, and exhibit undulose extinction. GS-05-00 Basalt or basaltic andesite Thin Section A porphyritic basalt or basaltic andesite, it is made up of phenocrysts and glomerocrysts of plagioclase that are zoned and exhibit albite twinning; Carlsbad and polysynthetic twinned alkali feldspar, clinopyroxene (some of which is altered), and subhedral to euhedral magnetite. The matrix is made up predominately of feldspar, altered pyroxene (serpentine/chlorite) and magnetite. Several large clots of calcite are found in the sample. Some areas within the sample are relatively fresh, while some appear highly altered. The

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plagioclase grains have numerous melt inclusions, which give them a characteristic sieve texture. GS-06-00 White Glass w/ mineral bands (impact melt rock?) In outcrop and hand sample, the sample appears to be massive, white glass with some mineral banding defined by darker phases and reflective opaques. The rock has the appearance of a quartzite, but without a sugary texture. It fractures into irregular sheets. Thin Section This rock is predominantly cryptocrystalline to microcrystalline quartz and feldspar, with some phenocrysts of plagioclase and an opaque (pyrite). Compositional banding is defined by phenocrysts of plagioclase feldspar and pyrite. Many of the plagioclases are altering to a dark gray, isotropic phase. These altered areas of plagioclase appear to be clouded, with a brown to yellow color in PPL and brownish-yellow in XPL. GS-06A-00 Turquoise-blue clast breccia (suevite?) The sample has a clastic (tuff-like) texture, and is composed of poorly sorted turquoise-blue clasts and smaller off-white and beige clasts in a frothy beige matrix that includes round, dark

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gray phases and specks of black phases. The sample is moderately indurated, and exhibits strong effervescence with HCl in some areas of the blue clasts and matrix. The rock has a low density and it is quite permeable to liquids, though it does not appear to be obviously porous or vesiculated. Thin Section Under PPL, the blue clasts in this sample contain crystals of plagioclase feldspar, a cryptocrystalline, emerald green phase (possibly chlorite or pumpellyite), ovoid inclusions of radial plagioclase feldspar with chilled margins, decomposed ulvspinels, and occasionally shocked plagioclase crystals exhibiting a checkerboard texture, shock mosaicism, and partial transformation to maskelynite. In several blue clasts, calcite is the dominant phase, and exhibits yellow birefringence colors and a distinctive melt-bleb texture. However, most of these blue clasts appear to be quenched, devitrifying glass with abundant microlites of feldspar. Most of the blue clasts are intensely deformed and exhibit both flow, which may be the result of incipient melting, or extreme plastic deformation. The beige clasts are highly vesiculated, and commonly contain spherules of brown glass, shocked plagioclase, augite, calcite, magnetite / ulvspinel and cored inclusions with cavity fills of feldspars and clays. These clasts also exhibit melt textures and flow features, and they are more intensely deformed than the blue clasts. Some of the beige clasts consist entirely of cored inclusions, melt blebs and spherules of brown glass. The cavity fills (cored inclusions) are circular to oblate in shape and contain radiating feldspar crystals. Occasionally, a radiating, acicular, emerald-green mineral, possibly pumpellyite, occurs with feldspar in cavity fills. In one thin section of this sample, possible PDFs were observed in a cavity fill in one of the beige clasts. The crystal had gray birefringence, low positive relief, and it yielded an off-centered, positive, uniaxial figure, which proves it to be quartz. Within this crystal, two possible faint sets

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of PDFs can be seen in plane-polarized and crossed polarized light. A third clast type can be distinguished only under the microscope. It is yellow in color and consists of plagioclase, augite, calcite and magnetite. The calcite commonly occurs as a total or partial replacement for the plagioclase. These are the least deformed of the different clast types and are highly altered. Some of the yellow clasts include, or are in contact with, shocked plagioclase feldspar. The matrix of the clasts appears to be highly altered (sericitized?) microlites of plagioclase The clasts are enclosed in a hypocrystalline matrix of brown, flow banded glass, shocked plagioclase, augite, calcite, ulvspinel, ilmenite and undeformed calcareous microfossils. Some of the most intense localized melt effects seen in plagioclase feldspar are observed in the matrix. Some plagioclase grains in the matrix appear to be recrystallized diaplectic glass. Bryozoans, foraminifera, and other unidentified microfossils can be seen (slightly reacted on the rims, yet intact) within the matrix. (See sample GS-11-00) GS-07-00 Basalt or Basaltic andesite Thin Section This sample is made up of phenocrysts of clinopyroxene, subhedral magnetite, zoned plagioclase feldspar, and Carlsbad twinned alkali feldspar. The matrix is approximately 50% glass and 50% crystals of feldspar, altered pyroxene (serpentine/chlorite), magnetite and

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variably sized clasts of fossiliferous limestone. Many of the plagioclase feldspar crystals have numerous melt inclusions, which give them a typical sieve texture. GS-08A-00 Basaltic andesite Thin Section This sample is made up of phenocrysts of plagioclase exhibiting both Carlsbad and albite twining, some of which are chemically zoned and/or posses sieve textures. These are contained within a fine-grained matrix of clinopyroxenes, olivine or orthopyroxene altered to serpentine, subhedral to euhedral magnetite, and an undetermined, microcrystalline reddish-orange phase. The Michel-Levy test for plagioclase feldspar yields An 50 compositions. Based on textural relations, the crystallization order in this sample was magnetite, olivine, cpx, and plagioclase. GS-08-00 Highly weathered and hydrothermally altered glass breccia Thin Section This sample is highly altered and weathered, and contains clasts of brown and beige glass which occasionally include highly altered laths of plagioclase; yellowish clasts with sporadic microlites; and black clasts with flow features and aligned microlites. Veinlets of a rusty brown microcrystalline phase that resembles chalcedony cuts through many of these fragments and is pervasive throughout the sample.

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The brown and beige clasts and the yellowish tinted clasts bear a remarkable resemblance to those of one of the less weathered breccias collected by Bob Stewart in 1995. This sample, designated 2-14-95-4, is a sulfur-rich glass breccia containing abundant subhedral to euhedral pyrite crystals. However, no pyrite crystals have been observed in GS-08-00. Both the brown and beige clasts and the yellowish clasts have glassy textures, with some microlites and other crystalline inclusions. Plagioclase feldspar laths are abundant throughout, but are highly altered and sericitized. The yellowish clasts contain lesser amounts of plagioclase, but contain cotton ball-like inclusions of a yellowish phase (sulfur?). Some patchy areas in the yellowish clasts that display slight birefringence may in fact be relict plagioclase laths that have been subjected to severe alteration. The black clasts in this rock are rare, and represent inclusions of dark glass that exhibits plastic deformation. The black coloration is strongest in flow banding within the clast (possible schlieren?) These clasts are very similar to features seen in sample GS-13-00 and the glass inclusion surrounding the pyroxene necklace seen in sample GS-10-00. There is a greenish tinted, high relief phase that shows gray birefringence colors found near cavities and along veins. Serpentine is found in conjunction with this phase in one area. GS-09-00, and P8-2-2-90, GS-24-00 Annealed greywackes, siltstones and sandstones (shocked?) The samples from the central region of the structure are yellowish-white, highly fractured, brecciated, oxidized. stained, moderately indurated, chalky (alteration) siltstones, sandstones

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and greywackes. Thin Section These GS series samples are similar to sample P8-2-2-90 from Bob Stewarts suite of rocks. It is typical of the sugar textured rocks in this structure. The samples seem to have undergone annealing, as indicated by the lack of matrix and the sub-hexagonal shape exhibited by the feldspar and quartz grains. The sub-hexagonal grains of annealed feldspar and quartz dominate. Almost all of the grains contain or are bordered by small, subparallel lath-like voids or fractures of a, as of yet, undetermined origin early results suggested these voids may have contained graphite. Although there is virtually no matrix, some intergranular phases do occur. The intergranular phases include clays, oxides and an unknown phase. Slightly shocked phenocrysts of plagioclase feldspar exist in vugs, veins and pore spaces and exhibit prominent undulose extinction. GS-10-00 Basalt or melt rock? Thin Section GS-10-00 appears to be a porphyritic basalt or basaltic andesite made up of phenocrysts and glomerocrysts of variably altered clinopyroxene. The matrix is feldspar, altered pyroxene, and magnetite. Some serpentine/chlorite and clots of calcite are found in the matrix of this sample. This sample includes a texture called a pyroxene necklace, or pyroxene-quartz corona, which develops when a xenocryst of quartz melts and reacts with mafic mesostasis to create a

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surrounding corona of pyroxene. These necklace structures are also found in samples GS-13a00 and GS-27-00. GS-11-00 Tuffaceous breccia (Suevite / Impact melt breccia?) Thin Section This sample is quite similar to sample GS-06a-00, with several exceptions. Sample GS-11-00 lacks turquoise-blue melt clasts and the localized melted grains of plagioclase feldspar. It also contains virtually no pyroxenes. The matrix of this sample can also be distinguished from GS06a-00 in that it contains more glass. It may represent a rock transitional between impact melt breccia (which is clast supported) and suevite (which is matrix supported). The matrix of this sample is composed of comminuted mineral grains, predominantly feldspar, but also including spinels, rare, undeformed microfossils; and volcaniclastic and siliciclastic rock fragments. All are mixed in brown, flow banded glass. Several plagioclase laths exhibit a checkerboard texture, and partial diaplectic transformation. One clast contains highly altered spherules in a matrix of glass and microlites of feldspar. GS-12-00 and GS-28-00 Tuffaceous sandstone or greywacke (calcareous)

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Thin Section Abundant angular fragments of unaltered plagioclase and quartz are contained in a matrix of tuffaceous materials, and clasts of siltstone micrite, clays and oxides. Aside from the plagioclase and quartz, most of the other clasts in this rock are relatively small and difficult to discern, even under the highest magnification. GS-13-00 Porphyritic glass w/ phenocrysts Thin Section The sample includes phenocrysts, and glomerocrysts of plagioclase feldspar, augite and magnetite in a glassy matrix with abundant microlites of feldspar. The sample exhibits flow banding based on the alignment of the microlites. Dark, glassy bands are seen around phenocrysts and glomerocrysts, and also conform to the apparent flow direction. Many of the plagioclase phenocrysts have sieve textures. A spherulitic pattern of fracture indicates that the sample behaves more like glass then a typical aphanitic volcanic rock. A similar, if more pronounced, texture is observed in sample GS-21-00. GS-14-00 Lithic/Volcanic Breccia w/ altered igneous clasts (clasts of 18 and 18a)

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This sample appears to be a breccia of poorly sorted, angular to subrounded, gray clasts, and reddish altered clasts of an igneous origin, that vary from several millimeters to 3 centimeters in diameter. The clasts are enclosed in a comminuted matrix (30-40%) of rock, which consists of andesite and mineral fragments, and is slightly effervescent in 10% HCl. Highly altered amphiboles are recognizable throughout. The rock fragments appear to be largely similar to samples GS-18-00 (Gray Andesite) and GS-18a-00 (Reddish Andesite), which were found in the vicinity. Thin Section Distinct fragments of altered igneous rocks are easily seen in PPL, but become difficult to discern in XPL. Igneous clasts are composed of plagioclase feldspar, altered amphibole (black both in PPL and XPL)), magnetite, chlorite and quartz in a re-crystallized quartzand feldsparrich matrix. The fragments are sub-rounded to angular in shape and are supported by a comminuted matrix of tiny, angular igneous clasts, plagioclase, quartz, calcite and rare siltstone and carbonate fragments. A finely pulverized mixture of rock and mineral materials that appears dark brown to black in both plane-polarized and crossed-polarized light in turn supports these components. Veinlets of fibrous zeolites and calcite can be found throughout the sample. GS-15-00 and GS-17-00 White-spotted gray glass These samples occur in the field as a massive body of highly fractured, gray rock that exhibits randomly distributed white spots <1 mm in size. The spots do not reflect a specific phase, but are a textural feature. The sample has what appears to be a strong flow banding and a layered

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appearance. Chalcedony and hematite or jasper appear to be the main constituents infilling numerous fractures in this rock unit. Thin Section A hypocrystalline glass consisting of flow banded and strongly oriented microlites of feldspar, with phenocrysts plagioclase feldspar, magnetite, and accessory apatite and clays. The plagioclase crystals all exhibit prominent undulose extinction and occasionally have planar fractures (PFs) inclined 45 to the 010 albite-twinning plane. These planar fractures are in filled with alteration phases, possibly clays. The white spots that are clearly noticeable in hand specimen are barely discernable under the microscope, and appear to be slightly more crystalline areas within the glass. It should be noted that these white spotted areas in the glass are still cryptocrystalline. It is difficult to identify the phases in these areas, even via electron microscopy. These areas are likely to be dominated by either feldspar or quartz. Fractures are filled with chalcedony. GS-16-00 (no thin section, see GS-26-00 Chert) GS-18-00 Altered gray igneous rock Thin Section

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The sample appears to be a highly altered (hydrothermally) porphyritic andesite with phenocrysts of plagioclase feldspar, altered and replaced amphiboles, and quartz in a finegrained, recrystallized matrix of quartz and feldspar with accessory opaques (titano-magnetite) and chlorite. Upon closer inspection, it appears that most of the mineral grains are fragmented and brecciated, with some fragments intruding into others. This texture may mean this rock is a polymict breccia and not a conventional volcanic igneous rock. Amphiboles are replaced by, or altered to calcite and an aggregate of various fine-grained minerals, including opaque and amorphous phases ( plates 10.19 and10.20 ). Some altered amphiboles have opaque centers surrounded by calcite. It is inferred that these phases were once amphibole, based on the fact that they have retained the euhedral shape of a typical amphibole, along with their original 60-120 cleavage pattern, and because less altered fragments retain the typical yellow-to-brown pleochroism of hornblende. Many of the plagioclases in this sample are highly altered and rimmed, and often replaced by calcite. Linear fractures nearly perpendicular to the albite twining planes in plagioclases can be seen in some grains, and prominent undulose extinction is common. Quartz grains are often rounded and have a fine-grained corona around them of quartz and feldspar, which may indicate quenching. The quartz is often fractured, and the fractures are filled with secondary calcite ( plates 10.21 and10.22 ). A relatively large biotite grain was found in one of the thin sections that exhibits extreme undulose extinction and clear kink banding, both of which indicate stress ( plates 10.2325 ). The matrix of recrystallized, sub-hexagonal feldspar and quartz bears a remarkable resemblance to the annealed sugary textured sandstone GS-09-00 This attribute, among others in this rock, corroborates the view that it is not a typical volcanic sample of the region. GS-18A-00

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Altered reddish igneous rock Thin Section This sample bears strong similarities to GS-18-00, but can be immediately distinguished from it by its strong reddish color in hand specimen ( plate 10.10 ) Other distinguishing characteristics are seen in thin section. The amphiboles in this sample, as in sample GS-18-00, are highly altered and have a reddish-brown to black appearance. They are nearly complete opaque, with euhedral amphibole shapes intact. Highly fractured quartz grains are cut by numerous veinlets of calcite. Opaque minerals are present but are not nearly as abundant as in GS-18-00. The matrix is not so strongly annealed, and consists of comminuted, equigranular feldspar, quartz, altered hornblende, secondary calcite and opaque minerals ( plates 10.17 and 10.18 ). Several biaxial positive, fibrous minerals exhibiting anomalous first order grays, and tinted yellowish brown with brown to yellow pleochroism were noticed, but remain unidentified at this time (possibly altered biotite grains). GS-19-00 Carbonate / Silicate rock This sample is a massive black rock with a frothy brownish reaction rind. Upon first inspection it looks like weathered basalt, but the massive black areas react violently with 10 % HCl solution, clearly marking it as a carbonate. Thin Section

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This sample appears to be a contact between a highly altered, vesiculated, siliceous volcanic rock and an altered carbonate rock that includes volcanoclastic debris and numerous veinlets and pockets of zeolites. The carbonate component is a foraminiferal, sparry to micritic calcite, with clasts of highly altered feldspars that have been replaced by zeolites and/or calcite, but still maintain lath-like shapes. Numerous inclusions of cubic opaques, likely to be pyrite, can be found throughout the matrix and as inclusions in the fossils. The contact between the carbonate component and silicate component is rather sharp. The silicate component consists of vesiculated and very fine-grained volcanoclastic materials (ash?) with sporadic, highly altered feldspar laths. This area is strongly stained from oxidation and occasionally contains clots of calcite. GS-20-00 Green tuffaceous rock Thin Section This thin section could not be cut properly as it expands when in contact with water and becomes friable. The slide is several microns too thick, resulting in a erroneous birefringence colors. Plagioclase feldspars, which are easily identifiable by their lath-like shape and albite twinning, exhibit second order blues, greens and yellows. Phenocrysts of plagioclase are enclosed in a matrix of highly altered ash, volcanoclastics and what appears as an amorphous yellowish green material under plane and crossed-polarized light.

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GS-21-00 Black Glass (Impact melt rock?) This sample is a massive, hypocrystalline brown glass with a clear spherulitic texture that can be seen in hand specimen. Of all the glasses found in this suite, this sample is the most crystal poor. It closely resembles a less crystalline version of GS-13-00. Partially assimilated phenocrysts of plagioclase, magnetite and pyroxene are found but are not common (less than 5 % total). The smaller population of phenocrysts, primarily feldspars, exhibits a strong alignment with the apparent direction of melt flow. Thin Section This sample is a massive, dark brown, hypocrystalline glass containing sporadic microlites of feldspars and magnetite that strongly align to the direction of flow. This sample exhibits an extensive spherulitic texture that is more obvious than the texture seen in sample GS-13a-00. GS-22-00 Green and Beige Melt Breccia (impact-melt Breccia?) This sample consists of poorly sorted, beige and pale greenish-beige clasts, <1mm to a few centimeters in diameter, that have undergone extreme plastic deformation. These are supported by an emerald green, glassy mesostasis. The origins of the clasts are not recognizable in hand

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sample, but may be of sedimentary in origin, possibly siltstones or greywackes. Thin Section Phenocrysts of plagioclase, mineral fragments (mainly feldspars), altered and weathered opaque phases, glass fragments, siltstone fragments and rare basaltic andesite fragments are enclosed in a greenish, intensely deformed, flow banded, hypocrystalline matrix that bears a strong resemblance to the turquoise blue clasts found in GS-06a-00. The matrix is highly vesiculated and contains abundant cavity fills of microcrystalline chalcedony. Bands of beige glass are abundant and may represent intensely deformed and melted siltstone fragments. Globules of a reddish oxides (hematite?) are pervasive throughout the sample, associated with areas of intense plastic deformation. Many of the plagioclases are highly fractured and exhibit undulose extinction. Several unknown opaques exhibiting anomalous yellowish-orange coloration occur in cavity fills, associated with euhedral apatites and chlorite (?). The dominant green coloration of this specimen may be the result of abundant chlorite and possibly pumpellyite. GS-23-00 Altered clast-poor black glass breccia (impact melt rock / breccia?) This sample is a massive, dark gray glass that is cut by numerous veinlets of a white material that is pervasive throughout the outcrop (maybe microcrystalline quartz). This sample is relatively clast poor, but it contains several partially assimilated or annealed greenish gray clasts that are not clearly identifiable in hand specimen.

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Thin Section In thin section, this dark gray glassy rock contains some basaltic fragments, plagioclase grains and rare clinopyroxene grains (this was the only glass breccia found with intact pyroxenes) and it resembles very closely the glass breccias found south and southwest of the central uplift (see GS-01-00, GS-03-00, GS-25-00, P8-2-4-90, 2-14-95-4, and 2-14-95-5) and the black glasses (GS-13-00 and GS-21-00) found at various locations. The predominant glass matrix is dark brown in PPL, and shows local indications of flow, brecciation and devitrification. The specimen has abundant veinlets and cavity fills of microcrystalline quartz and (possibly) zeolites. Phenocrysts of plagioclase exhibit undulose extinction, many are highly fractured by cross cutting veinlets and some of them are completely comminuted. No indications of diaplectic transformation are present in this sample. A large, annealed, centimeter-sized porphyritic andesite clast can be seen in this thin section. The plagioclase feldspars contained in this clast are also highly fractured, and exhibit undulose extinction. Flow banding in the glass can be seen following the boundaries and flowing around this large clast indicating that the clast was incorporated in the sample while the sample was at least partially molten. GS-24-00 (see GS-09-00) GS-26-00 and GS-16-00

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Chert or Quartzite This sample appears to be a yellowish-brown, massive chert with pervasive crosscutting veinlets of microcrystalline quartz. Some of the specimens from the same outcrop are greenish in color. Thin Section In thin section this rock reveals itself to be a coarse crystalline quartzite (?) with numerous veinlets of chalcedony. The classification of this sample is based on its relatively large, interlocking quartz grains either it is metamorphic in origin, or it was hydrothermally precipitated. The sample is extensively Fe-stained and more than 90% of the quartz crystals have inclusions of reddish-brown Fe-rich pelloid-like feature, which is likely to be the source of the rocks yellowish-brown coloration. GS-27-00 and GS-13a-00 Basalt? In outcrop and hand sample these samples appear to be porphyritic basalts that exhibit a layered appearance. Mineral grains appear to be aligned parallel to these layers, possibly indicating melt flow. Thin Section This sample is porphyritic, and made up of phenocrysts and glomerocrysts of clinopyroxene (some of which is altered) and phenocrysts of serpentinized olivine. The matrix is dominated by

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plagioclase, altered pyroxene, and magnetite. Some serpentine/chlorite and several clots of calcite were found in the matrix of this sample. These samples are almost identical to sample GS-10-00, with the exception that GS-10-00 has fewer olivine phenocrysts and that it is not strongly layered. Pyroxene necklace, or pyroxene-quartz corona structures has also been observed in these samples. All the features seen in the GS-10 pyroxene necklace are recognizable in this structure, though it is much smaller and has undergone alteration. Quartz grains are surrounded by an aluminous glass that has reacted with the predominately mafic matrix to form a corona of diopsitic pyroxenes. GS-28-00 (no thin section see GS-12-00) GS-29-00 and P8-2-5-90 Tuffaceous Carbonate Thin Section These samples represent tuffaceous carbonates or carbonate lithic breccias composed of abundant fossiliferous to micritic carbonate fragments, silicate mineral fragments, and minor pyrites. Most of the carbonate fragments contained in these specimens are fossiliferous, predominantly foraminifera and some bryozoans. Along with these carbonate fragments are fragmented

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plagioclase feldspars and brown glass. All the plagioclases observed in thin section exhibit undulose extinction and some have undergone partial diaplectic transformation. The brown glasses fragments are circular to ovoid in shape. These are completely isotropic under crosspolarized light and many are heavily included with euhedral pyrite crystals. The two specimens GS-29-00 and P8-2-5-90 are identical in hand sample but differ in thin section in two ways: (1) GS-29-00 is more extensively comminuted than P8-2-5-90. As a result, we see a reduction in fragment size and preserved fossils in GS-29-00 when compared with P8-2-590/ (2) GS-29-00 contains a more siliceous/volcanogenic component than P8-2-5-90. GS-30-00 and P8-2-7-90 Shocked Carbonate? This is a massive, crystalline carbonate rock that is beige in color with brownish glassy spots less than 1 mm in diameter, which give the rock a leopard-skin appearance in hand specimen. Thin Section The specimen is composed of sparry calcite, amorphous materials, and glassy blebs that form interconnected cavities. The calcite and amorphous materials have indistinct boundaries in PPL, but have very discrete boundaries in cross-polarized light due to the opaque/isotropic behavior of these phases.

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The sparry calcite occurs throughout the sample in cavities and veinlets of relatively large interlocking crystals. This configuration of sparry calcite suggests that re-crystallization in some sections of the sample has occurred. A subset of calcite grains that have an anomalous appearance both in plane-polarized and crossed-polarized light, and may represent shock-metamorphosed calcite. In PPL these grains are readily recognizable by their rusty-brown color and arrays of small fluid inclusions. In XPL, these grains exhibit overall lower birefringence colors (second order yellows and blues) and the inclusions become difficult to discern. View a list of the samples Choose samples by appearance Choose samples by location

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DISCUSSION Both petrographic features and chemical trends observed in suite of rocks from the Gatun site provide evidence supporting the occurrence of a high P / T metamorphic event, as would be generated during a hypervelocity impact. Below we examine these features in the Gatun suite, and compare / contrast our findings with reports from documented impact sites, as well as with volcanic environments such as one could encounter in Panama. Field Relations Geometry of the site, and possible age: Due to the paucity of outcrops and visible relationships among units, it is difficult to produce a coherent picture of the geological and stratigraphic relationships within the Gatun structure. However, the distribution of rock units across this field area is what one would expect for an impact site. These features can also be easily distinguished in a cross-sectional profile ( Figure 6b ) constructed from the sample map ( Figure 6a ). By comparing the profile and lithologic layout of the Gatun structure with profiles and general reconstructions from other impact structures, we see that the abundance of "glassy" type lithologies, as well as a relatively preserved central peak and rim structure, suggest that what is now exposed at the surface is relatively shallow in a complex crater profile (compare Figure 6b and 6c ). In addition, the disturbed siliciclastic rocks (Gatuncillo Formation?) is confined to the central uplift feature of the structure, which

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appears to be surrounded by the disturbed carbonates and volcanics (Caimito Formation?) closest to the uplift and at lower elevations, and by glasses and glass breccias further out and at higher elevations. Overall, these relationships lend credence to the suggestion that the units in the Gatun Structure are in a concentric configuration. The occurrence of such a diverse suite of rocks in a small, quasi-concentric layout (the sampling area is roughly 4 km2) is significant. Almost all impact structures show a largely concentric configuration, similar to that of the Gatun site, when exposed at the surface. The geographic distribution of rock units across an impact site is often the only map-scale indicator of an impact, as terrestrial weathering processes rapidly destroy most macro-structural features (i.e., a crater rim, inverted stratigraphy along the rim, shatter cones, etc. ( Melosh, 1989, French, 1998, Montanari and Koeberl, 2000 ). However, the effects of excavation, modification and shock change the erosional characteristics of the rocks, such that circular features may be evident in the local topography. The Gatun site shows both a raised center, and a slightly elevated rim, possibly indicating complex crater morphology. Based on the scaling relationships of other complex impact structures, regardless of planet on which it was formed, there is a relationship between the diameters of the final crater, peak ring, and central uplift. The peak ring diameter and the central uplift diameter is roughly 0.5 and 0.22, respectively, of the final crater diameter ( Melosh, 1989 ). The topography of the Gatun structure suggests there may be a inner peak ring structure 1-1.5 km in diameter and the central uplift is approximately 600 meters in diameter. These figures yield an approximate crater diameter of 2.72-3 km, which appears to be consistent with the overall topography and morphology of the structure. As erosion rates in the tropics are exceptionally high (possibly as high as 30 cm/Ma R. H Stewart, 2001, personal communication), the Gatun structure is either very young, or it must have been preserved and subsequently exposed only recently. One possible scenario is that

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the Gatun structure may have been a shallow-marine impact. Following a marine impact, tsunami and resurge deposits can bury an impact structure in conjunction with conventional marine deposition, which would rapidly bury an impact structure and preserve it. Later, as the Panamanian Arc was uplifted and sutured onto North and South America (~3.6 Ma), the structure may have become exposed after overlying lithologies were eventually removed by the continual, intense tropical weathering. The age of the Gatun structure is uncertain. Preliminary K-Ar dating on the glass breccia unit yielded an age of 41.9 .3 Ma, which is older than determined paleontologic ages for the Caimito and Gatuncillo formations (R. H Stewart, 2001, personal communication). Based on estimates of erosion rates in the region, (approximately 30 cm /year) the impact must be at least as old as Pliocene to late Miocene, and if the shocked carbonates from the site are from the Caimito Fm., then the impact must be postOligocene (~ 20 Ma). Addition of atmospheric Ar may have occurred during the formation of the breccia, which resulted in anomalously old KAr dates. Impactite Lithologies: Most of the Gatun structure's suite of samples are petrographically and chemically consistent with the four most common impactites lithologies, based on the classifications of Stoffler and

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Grieve ( 1994 ) and French ( 1998 ). A number of the Gatun samples appear to be melt-bearing breccias. This class of impactite is further divided into two subclasses: Suevites (GS-06a, GS-11), which contain discrete melt fragments in a clastic matrix of rock and mineral fragments preserving varying degrees of shock metamorphism. Impact melt breccias (GS-01, GS-03, GS-08, GS-22, GS-23, GS25, P8-2-4-90, 2-14-95-4 and 2-14-95-5), which contain rock and mineral fragments contained in a matrix of holohyaline to holocrystalline melt. Glass samples GS-06, GS-13, GS-15, GS-17 and GS-21 are impact melt rocks, essentially hypocrystalline shock melts. Sample GS-14, and possibly GS-18 and 18a, are lithic breccias (fragmental impact breccias), containing fractured and broken up lithic fragments, but no melt component. The rest of the suite falls into the category of shocked and non-shocked siliciclastic rocks, carbonates and igneous rocks. Shock Metamorphic features in Gatun Suevites (samples GS-06a-00) According to the classification scheme put forth by Stoffler and Grieve ( 1994 ), the presence of melt clasts supported by a matrix of comminuted rock and mineral fragments, and the presences of shock metamorphic effects, such as those seen in plagioclase feldspar, suggests

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that sample GS-06a-00 is an impactite called a suevite. Maskelynite: A diaplectic glass is generated through the intense shocking of a crystalline substance, which subsequently disrupts its crystalline structure. The crystal is transformed in the solid state (entirely or partially) into a glass, preserving the original outline of the crystal ( Williams and Jeanolz, 1989; Grieve, 1991; Grieve and Pesonen, 1992; Daniel et al., 1997; French, 1998; Montanari and Koeberl, 2000; Leroux, 2001 ). Recent studies of meteorites indicate that maskelynite can also form via the quenching of dense melts of plagioclase feldspar formed at high-pressure and temperature ( Chen and El Gorsey, 2000 ). Regardless of the mode of formation, a minimum pressure in excess of 20 GPa (200 kbar) is required to form plagioclase feldspar glass. Experiments conducted by Daniel et al. ( 1997 ) indicate that the onset of amorphization of plagioclase begins at 14 GPa, and goes to completion at 16 GPa under static conditions. However, these pressures are not sufficient to stabilize maskelynite, as it reverts to a crystalline state when returned to ambient conditions. Irreversible amorphization of plagioclase feldspar occurs at 22-28 GPa and at 300 K ( Williams and Jeanloz, 1989; Daniel et al., 1997 ). These conditions far exceed the pressure regimes observed in terrestrial volcanic settings (.5 to 1 GPa, or 5 to 10 kbar, typically; maximum: ~5 GPa) ( Montanari and Koeberl, 2000 ) or the conditions encountered in metamorphism on the Earth (typically less than 5 GPa) ( French, 1998 ). The preservation of an amorphous state indicates pressures of at least 22 GPa ( Williams and Jeanloz, 1989 ). While the Raman results suggest that the plagioclase feldspars in sample GS-06a-00 are partially amorphous, the microprobe data indicates that these nonto low birefringent areas within these crystals are the result of hydrothermal analcime replacement and low-grade zeolite

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metamorphism ( Boles et al., 1977; Deer et. al., 1993 ). This is especially curious considering that analcime replacement in crystalline plagioclase feldspars are not common, and that the other zeolites associated with such replacements in plagioclase feldspars with a considerable An content are not present (heulandite and/or clinoptilolite, the Na-Ca-K rich zeolites). Analcime commonly is a replacement mineral for relatively pure albites and nephelines associated with feldspathoid volcanics that have undergone low-grade metamorphism, and in some basalts, where it is typically restricted to the groundmass or in vesicles as a secondary hydrothermal phase ( Deer et al.,1993 ). Analcime and zeolite replacement is commonly pervasive in hydrothermally altered volcanic glasses. As a result, it is probable that these nonto low birefringent areas in GS-06a-00, which have been suggested to be amorphous plagioclase by Raman Spectroscopy and Analcime by electron microprobe analysis, were once diaplectic glasses. Naturally, these glasses would rapidly succumb to the harsh alteration effects associated with tropical environments, and would be almost completely replaced by analcime over a short period of time. Also noteworthy is the fact that Analcime is cubic and highly ordered in relation to any glass, thus a Raman spectra of analcime can be completely distinguished from a Raman spectra that contains an amorphous phase, such as maskelynite. Feldspars in GS-06a-00 show an unusual multi-phase character in that grains grade from birefringent, crystalline zones into isotropic to low birefringent zones; and parts of the grains show indications of melting and flow within the matrix. These multi-phased character also appears to be consistent with partially amorphous plagioclase feldspars from the Manicouagan impact structure in Newfoundland, Canada ( French, 1998 )( Plates 4.13-17 and Plate A ). Maskelynites / zeolites are extremely Na-rich and Ca depleted relative to adjacent crystalline feldspar, and many of these areas have preferentially altered into other clays relative to the crystalline areas, which in some cases have remained completely pristine. The depletion in Ca and enrichment in Na seen here is similar to, but more extreme than, the redistribution of Na

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and Ca observed in some SNC maskelynites, and may reflect chemical exchanges between the melt and surrounding crystalline rocks: in this case, the associated crystalline feldspar. The undisturbed feldspars exhibit an average An 65 (labradorite) composition. Feldspars in equilibrium with evolved arc magmas as might typically erupt along the Panamanian arc segment are more sodic, so it is possible that the undisturbed Gatun feldspars were compositionally closer to andesine or possibly oligoclase. Amorphous portions of the Gatun feldspars yield lower totals for microprobe analyses than crystalline portions ( Table 4b ). These portions have been partly to completely replaced by analcime (NaAl2O6 2 H2O). The congregation of melt along grain boundaries (and apparent melt flow) reflects immiscibility between the feldspathic melt and a more Fe-rich areas, which have since become the rock mesostasis. As is noted in obsidians, Si-rich melts mix very poorly, so what we see in GS-06a00 is siliceous melt immiscibility on a very fine scale. Many of the feldspar grains in the sample exhibit evidence for partial melting and recrystallization ( Plates 4.32 and 4.39 ). In impact sites, selective melting results from high temperatures and pressures (35-60 GPa and >1000C) associated with the passage of the shock wave resulting from a hypervelocity impact. This phenomenon is often seen in feldspar grains in suevites ( French, 1998 ). Other high P-T features: Plastic deformation of feldspar grains is also observed in sample GS-06a-00 (best seen in plates 4.32 and 4.33 ). This phenomena occurs when the Hugoniot elastic limit (HEL) is exceeded ( Melosh, 1989 ). The HEL value for most rock forming minerals lies between 5-10 GPa (50-100 kbar). The onset of plastic deformation for plagioclase feldspar is approximately 3 GPa (30 kbar), beyond the pressure regime of volcanic settings ( Montanari and Koeberl, 2000 ). Therefore, the presence of plastically deformed plagioclase feldspars, like the presence of diaplectic glass, is indicative of an impact origin for the Gatun structure.

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Other related features in GS-06a-00 include carbonate/silicate melt immiscibility in several of the turquoise-blue clasts ( plates 4.40-43 ). The carbonate in the melt clasts is believed to be primary and not a replacement or alteration feature as It possesses an amorphous configuration, with fine crystals along its margins (a probable chilled margin), similar to that seen in the melted feldspars. Also, the carbonate does not appear to be replacing another phase, nor are veinlets present such as might occur due to hydrothermal replacement. Evidence for carbonate-silicate immiscibility has been observed in suevites from other sites, such as the Ries impact structure ( Graup, 1999 ). Graup ( 1999 ) demonstrated (based on data from Tyburczy and Ahrens, 1986 ) that strongly shocked carbonate would melt and not decarbonate upon release from shock pressures in excess of 42 GPa and temperatures exceeding 2000K. Glass, Zeolite and Clay-filled Impact Spherules: GS-06a-00 also includes spherules: small, chondrule-like blebs of impact melt, which range in character from glassy to finely crystalline ( plates 4.27-31 ). Chemically and mineralogically, these spherules are not consistent with a biogenic precipitate, or with a volcanic igneous origin. The Gatun Spherules are morphologically comparable with chondrules, lunar spherules, and KT impact spherules ( Simon et al., 1995; Symes, et al., 1998; Bohor and Glass, 1995 ). Spherule compositions are plotted in Figures 8 and 12 The trends seen in these diagrams attest to a origin through the melting and mixing of mineral phases that occur within sample GS-06a-00: in particular titano-magnetite, plagioclase and alkali feldspar. Three different types of spherules can be identified in sample GS-06a-00: glass, fluid-drop or

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quench, and lithic ( plates 4.27-31 ). All spherules are highly altered, but still bear a striking similarity to the types of spherules that occur in the suevites from the Ries impact structure ( Graup, 1981 ). Glass spherules are the smallest of the three types, typically <1mm in diameter; they are dark and reddish brown, have a major and minor axis ratio of 1:1 and are almost identical to those seen in the Ries suevite. The fluid-drop, or quench variety of spherule is larger than the glass-type spherule and is the rarest type found in GS-06a-00. These spherules exhibit a quenched spinfex texture of glass and crystalline material (likely to be plagioclase feldspar). The lithic spherules are by far the largest and most abundant spherules in GS-06a00. They are oblong to oblate in shape and consist of brown glass surrounding a core of coarse crystalline plagioclase feldspar that, in most cases, have been replaced by clays and zeolites. These crystalline cores typically radiates inward, which indicates that recrystallization of these phases may have occurred. The overall morphology of the lithic spherules appears to be consistent with a melting--a quenching scenario--a larger melt droplet would not have time to homogenize, but would quench on the outside (glass) and remain hot and plastic within long enough to crystallize more slowly in the interior, and plastically flow into the non-spherical shapes they presently exhibit. Impact Melts and Melt Breccias (sample GS-22-00): Sample GS-22-00 texture appears to be consistent with an impact melt breccia, containing highly altered and annealed lithic fragments enclosed in a green, extremely fine-grained to amorphous, hypocrystalline matrix ( plates 15.4-15 ). In Sample GS-22-00, original Ti-Al rich spinel (titano-magnetite?, see table 13 ) have interacted with the matrix in such a way that Tirich areas have segregated from areas rich in Si and Al. These grains surrounded by an Fe-rich

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matrix, including blebs of quartz, have morphologies consistent with immiscible melts ( plates 15.25-28; 15.1-Si to 15.1-Fe and 15.2-Si to 15.2-Fe ). Similar shock metamorphic / melting effects occur in impact glasses from Aouelloul, Bosumtwi, Henbury, Ries, Wabar ( El Goresy, 1968 ) and in the Manson impact structure, Iowa ( Koeberl and Anderson, 1996 ). The temperatures required to melt spinel phases exceeds 1300C (ulvspinel melts at 1470C Deer et al., 1993 ), which is much higher than the eruptive temperatures of basalt and basaltic andesite volcanics in the Panamanian arc segment (~1000C). The dominant clast in many of the glass breccias is an opaque (black or dark brown) hypocrystalline to hyaline material that is best described chemically and texturally as an Ferich, feldspathic glass. These glassy clasts are chemically similar to the glass samples from the Gatun structure (with the exception of variations seen in Fe and Al that may result from oxidation and clay formation; see GS0800 Weathered Breccia GS2500 Glass breccia and Table 16a and 16b ). Occurrence of these glasses and glass breccias is highly irregular given the mode of volcanism of the Panamanian arc, and compositionally they do not resemble the dacitic (adakite) volcanism that characterizes the most recent eruptive activity in this region. These rocks were the first recognized anomaly in the Gatun structure. Fe-rich feldspathic glasses, similar to those found at Gatun, have been observed at other impact structures around the world, and have been recognized in suevites from the Roter Kamm impact crater in Namibia ( Reimold et al., 1997 ). Shocked Quartz: What the rocks of the Gatun site lack in terms of a typical impact signature is shocked quartz

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(PDFs and high-pressure polymorphs). It is not entirely surprising that shocked quartz was not encountered, as the dominant target rocks in this region of Panama are basaltic / andesitic volcanoclastics, and the marine carbonate rocks. Modal quartz is quite rare as such, but plagioclase is quite abundant. The majority of the quartz found in the area is associated with the lithic breccias and shocked siltstones of the central uplift. The quartz grains in these rocks are highly fractured and annealed, exhibiting sub-parallel to parallel fractures, but do not contain bona fide PDFs as described by Stoffler and Lagenhorst ( 1994 )( Plates 9.8-9 and 9.1415 ). Quartz grains in the lithic breccias and the Gatun melt rocks are highly fractured and recrystallized. Bulk chemical constraints: The Gatun glass and melt-bearing breccias exhibit chemical trends that distinguish them from local volcanic rocks. One of the most significant observations is that all the various melt samples fall along distinct linear arrays on major element variation diagrams. Linear arrays on such plots are consistent with the mixing of endmember components. In Figures 8-12 many of the linear trends suggest endmembers consistent with the compositions of minerals common in the Gatun target lithologies (i.e., magnetite, feldspar, calcite). Since many of these mineral phases require substantial temperatures (> 1300C), and in some cases high-pressures (calcite >40 GPa, Graup, 1999 ) to melt, the reasonable conclusion is that they are the product of impact melting ,and not volcanic/endogenic processes. The highest TiO2 content in the Gatun suite is found in the carbonate component of the carbonate / silicate rock GS-19-00. In neither arc igneous nor sedimentary rocks does one encounter Ti-rich carbonates. One sees high TiO in association with igneous carbonatites,

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2 with the titanium sequestered in perovskite (CaTiO3), which does not exist in surface rocks, and does not occur in our samples. However, a Ti-rich carbonate component could develop via the mixing of siliceous and carbonate melts, derived from Caimito formation lithologies. The Gatun rocks are relatively high K compared to local volcanic rocks, and the high Ba concentrations in the glasses and melt-bearing breccias also indicate an origin other than local volcanism, probably an impact. These chemical effects have been noted at other impact sites, where impact melts crystallize abundant potassium feldspars, which sequester both K and Ba ( French et al., 1997 ).

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CONCLUSIONS Based on field relations, lithologies, sample petrography, and the chemical systematics of the Gatun structure samples, a hypervelocity impact event is the most likely mode of origin for the Gatun structure. The maskelynite signature (RAMAN spectra) found in sample GS-06a-00 requires a minimum pressure of 22 GPa (220 kbar) to form, and other melting and shock effects in these samples point to similar extreme conditions. No other mechanisms known can produce the extreme conditions indicated by the Gatun site rocks. Because the occurrence of maskelynite has only been found in meteorites, highly shocked lunar anorthosites, impact sites and nuclear test sites ( French, 1998 ), the presence of maskelynite strongly suggests an impact origin of the Gatun structure. Other observations and characteristics supporting an impact origin for the Gatun structure include: l The structure exhibits the morphological characteristics of an eroded complex crater l The presence of highly fractured and intensely deformed lithologies, consistent with the major classes of impactites, are present in the structure.

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l The chemical variations in Gatun melt samples and spherules can be most easily explained as high-temperature melting and mixing of specific minerals common in the suspected target lithologies. This body of data for the Gatun sample suite cannot be satisfactorily explained by igneous volcanic processes, such as are occurring in the Panamanian arc segment; by regional metamorphic processes associated with the uplift of Panama; contact metamorphic/hydrothermal processes associated with Panamanian volcanism; or by sedimentary processes related to the deposition of the local rock units. Although some of the typical impact fingerprints (i.e., shocked quartz) are missing, other features are present (e.g., maskelynite and Fe-Ti-rich spherules) which indicate transient, extreme P-T conditions occurred within this relatively small area. Only a hypervelocity impact is known to produce such conditions, and generate the variety of rocks we find in such a small area. In order to confirm the Gatun structure as a documented impact site, and to fit it into the regional geological history in the Panama canal zone, an age determination on the glass and melt-bearing breccias is necessary. This work is in progress, and results should be obtained in 2002. An accurate age determination will also assist in determining if the Gatun structure was formed as an isolated event, or as part of an impact swarm due to the fragmentation of a larger body. Re-Os isotopic determinations, and platinum-group element (PGE) abundances can be very useful in confirming impacts, as Re, Os and other PGEs are markedly elevated in meteoritic materials and can highly contaminate target lithologies at even <<1% additions of

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impactor material. However as all meteorites do not have high PGE contents, there is a good chance that an impact structure may exhibit no PGE elevation. The lack of PGE enrichments in other documented impact sites is not entirely understood, but one possibility is that these structures were the result of the impact of an achondrite body (e.g. a basaltic meteorite < differentiated>). Given the population of achondrites in meteorite collections around the world, there is probably a one-in-ten chance, that any given terrestrial crater was generated by an achondrite body. Lastly, a geophysical survey using both magnetic and gravity methods may help to determine the original diameter of the crater and the depth of excavation (the transient crater's dimensions), as erosion alters the surface expression.

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APPENDIX B: DATA, FIGURES AND GRAPHS Major and Trace Element Data Microprobe Data CIPW Norms Maps, Area Photos, Figures and Graphs