Tracing the sources of cave sulfates: a unique case from Cerna Valley, Romania
- Permanent Link:
- Tracing the sources of cave sulfates: a unique case from Cerna Valley, Romania
- Series Title:
- Chemical Geology
- Onac, Bogdan P.
Wynn, Jonathan G.
Sumrall, Jonathan B.
- Publication Date:
- Subjects / Keywords:
- Sulfur Isotopes ( local )
Cave Sulfates ( local )
Thermo-Mineral Springs ( local )
Sulfuric Acid Speleogenesis ( local )
- serial ( sobekcm )
- In order to reliably distinguish between different genetic processes of cave sulfate formation and to quantify the role of thermo-mineral waters on mineral deposition and cave morphology, it is critical to understand sulfur (S) sources and S transformations during hydrological and speleogenetic processes. Previous work has shown that sulfuric acid speleogenesis (SAS) often produces sulfate deposits with 34S-depleted isotopic signatures compared to those of the original source of S in sulfate rocks. However, 34S-depleted isotopic composition of S-bearing minerals alone does not provide enough information to clearly distinguish SAS from other speleogenetic processes driven by carbonic acid, geothermal heat, or other processes. The isotopic composition (Î´18O and Î´34S) of sulfate minerals (mainly gypsum) from seven caves of the Cerna Valley (Romania) defines three distinct populations, and demonstrates that the Î´34S values of SAS-precipitated cave sulfates depend not on the source of the S, but also on the H2S:SO42âˆ’ ratio during aqueous S species reactions and mineral precipitation. Population 1 includes sulfates that are characterized by relatively low Î´34S values (âˆ’ 19.4 to âˆ’ 27.9â€°) with Î´18O values between 0.2 and 4.3â€° that are consistent with oxidation of dissolved sulfide produced during methane-limited thermochemical sulfate reduction (TSR) that presently characterizes the chemistry of springs in the upper Cerna Valley. Population 2 of cave sulfates has 34S-enriched Î´34S values (14.3 to 19.4â€°) and more 18O-depleted Î´18O values (from âˆ’ 1.8 to âˆ’ 10.0â€°). These values argue for oxidation of dissolved sulfide produced during sulfate-limited TSR that presently characterizes the chemistry of springs further downstream in the Cerna Valley. The Î´18O values of cave sulfates from Population 1 are consistent with oxidation under more oxic aqueous conditions than those of Population 2. Î´34S values of cave sulfates within Population 3 (Î´34S: 5.8 to 6.5â€°) may be consistent with several scenarios (i.e., pyrite oxidation, oxid
- Original Version:
- Chemical Geology, Vol. 288, no. 3-4 (2011-09-25).
- Source Institution:
- University of South Florida Library
- Holding Location:
- University of South Florida
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- This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.
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