The Mineral Assemblage of Caves Within Şălitrari Mountain (Cerna Valley, SW Romania): Depositional Environment and Speleogenetic Implications

Eighteen minerals belonging to eight chemical groups were identified from three caves within Şălitrari Mountain, in the upper Cerna River basin (Romania) by means of scanning electron microscopy, electron microprobe analysis, and X-ray powder diffraction. One passage in the Great Cave from Şălitrari Mountain, the largest cave investigated, exhibits abnormal relative humidity and temperature ranges, allowing for a particular depositional environment. The cave floor is covered by alluvial sediments (ranging from cobble, sand, and clay to silt-sized material), bear bones, bat guano, and rubble. These materials reacted with percolating meteoric water and hydrogen sulfide-rich hypogene hot solutions, precipitating a variety of secondary minerals. Most of these minerals are common in caves (e.g. calcite, gypsum, brushite), however, some of them (alunite, aluminite, and darapskite) require very particular environments in order to form and persist. Cave passage morphologies suggest a complex speleogenetic history that includes changes from phreatic to vadose conditions. The latter was punctuated by a sulfuric acid dissolution/precipitation phase, partly overprinted by present-day vadose processes. The cave morphology and the secondary minerals associated with the alluvial sediments in these caves are used to unravel the region’s speleogenetic history