Gypsum deposits in the Frasassi Caves, Central Italy
- Permanent Link:
- Gypsum deposits in the Frasassi Caves, Central Italy
- Series Title:
- Journal of Cave and Karst Studies
- Galdenzi, Sandro
- Publication Date:
- Subjects / Keywords:
- H2s ( local )
Frasassi Cave ( local )
Gypsum ( local )
- serial ( sobekcm )
- The Frasassi Caves are hypogenic caves in central Italy, where H2S-rich groundwater flows in the lowest cave level. Near the water table, the H2S is converted to sulfuric acid by biotic and abiotic processes, which have enhanced cave development. The sulfate generally deposits above the water table as a replacement gypsum crust coating limestone walls or as large gypsum crystals. Although the oxidation of sulfide also occurs below the water table, sulfate saturation is not achieved, therefore, sulfate does not precipitate below the water table.
In the upper dry levels of the cave, three main types of ancient gypsum deposits occurs: (1) replacement crusts, similar to the presently forming deposits of the active zone, (2) microcrystalline large and thick floor deposits, and (3) euhedral crystals inside mud. The study of the depositional setting and the analysis of sulfur isotopes in the gypsum and groundwater clearly demonstrate that all the sampled gypsum in the cave formed by H2S oxidation above the water table. Some fraction of small sulfur isotopic differences between H2S in the water and gypsum can be explained by isotopic fractionation during abiotic and/or biotic oxidation of H2S.
- Original Version:
- Journal of Cave and Karst Studies, Vol. 65, no. 2 (2003-08-01).
- Source Institution:
- University of South Florida Library
- Holding Location:
- University of South Florida
- Rights Management:
- 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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