Conditions and characteristics of cryogenic mineral formation in the caves of southern part of Siberian platform folding margins (Western Pre-Baikal region and Eastern Sayan)

Authors present the new data on the cryogenic mineral formation in the caves of Pre-Baikal region and Eastern Sayan. The mineral composition of cryogenic forms is represented by lansfordite and ikaite with gypsum and barite impurities. The results of calculation of the molecular ratio СаО, MgO and of the host carbonate rock, ice crust, and cryogenic minerals suggested that crystallization of ikaite from the solution reduces the СаО content, thereby producing the favorable conditions for magnesium minerals crystallization. It was revealed that the flattened ice crystals and aggregates with a flat bottom appears due to formation of cryogenic lansfordite precipitates in a thin film of water solution on the ice surface, or by wetting the mineral grains with water in result of ice melting. Mineral grains released from the ice crust by evaporation have no secondary transformations. Lansfordite was encountered as a cryogenic mineral at first time. It was the first finding of barite as part of cryogenic formations in the caves of Baikal region.