Sulfuric acid caves in Calabria (South Italy): Cave morphology and sulfate deposits

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Publication Date

12-18-2018

Publication Title

Geomorphology

Volume Number

328

Abstract

Research on karst in the Calabria region recognized three different hypogenic cave systems, all related to sulfidic thermal springs. Cave morphology, the depositional setting and isotopic characteristics of gypsum deposits reveal that the main process for cave formation was the oxidation of H2S to sulfuric acid. This process, known as sulfuric acid speleogenesis, was induced by thermal water rising towards the oxidizing zone in tectonic windows where dolomitic or limestone rocks outcrop. The δ34S values of most gypsum deposits prove they originated from sulfuric acid produced by H2S oxidation in the cave atmospheres. Most gypsum deposits in the Calabrian caves, in fact, exhibit δ34S values very similar to those of H2S, not to those of sulfate in the groundwater. On the contrary, the barite and part of the gypsum in the Terme Luigiane have δ34S values similar to those for sulfate in the water, implying that the sulfate minerals precipitated in a subaqueous environment. A large-scale deposition of replacement gypsum occurred only in the water table caves of Cassano, where subaerial corrosion greatly influenced cave morphology and the typical passage cross-sections. In the Terme Luigiane and Mount Sellaro cave systems, these subaerial processes caused only minor changes in inclined passages that had evolved mainly in subaqueous conditions.

Keywords

Caves, Karst, Hydrogen sulfide, Geochemistry, Gypsum

Document Type

Article

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.geomorph.2018.12.014

Language

English

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