Cryogenic Mineral Formation in Caves

• Main Authors: Žák, Karel, Onac, Bogdan P, Kadebskaya, Olga Ivanovna, Filippi, Michal, Dublyansky, Yuri, Luetscher, Marc
• Format: Book Part
• Language: unknown
• Published: Digital Commons @ University of South Florida 2018
• Subjects: Salt rejection; Water freezing; Cryogenic cave minerals; Paleo-permafrost proxy; C and O stable isotopes; Earth Sciences; Ice; permafrost
• Online Access: https://digitalcommons.usf.edu/geo_facpub/1919; https://doi.org/10.1016/B978-0-12-811739-2.00035-8

Freezing of karst water in caves forces the segregation of solutes, a process of rejection of dissolved ions by the advancing ice-water front during the growth of ice crystals. This process causes supersaturation of the unfrozen residual part of the solution and precipitation of some of dissolved compounds as minerals. Water evaporation and solution degassing additionally enhance the mineral formation. The cryogenic cave minerals constitute a variety of speleothems, which differ in practically all aspects from their counterparts formed in caves unaffected by freezing. The morphology and mineralogy of cryogenic cave minerals largely depend on the initial chemical composition of the karst water, the thickness of the water layer that freezes, and the freezing rate. The most common cryogenic minerals in the ice caves of limestone karst are fine-grained (powdery) carbonates produced by rapid water freezing in thin water layers. In contrast, slower freezing of large water volumes at cave temperature near 0°C produces coarse-grained cryogenic cave carbonates, which are typically associated with present or past permafrost conditions. Overall, the cryogenic cave carbonates are characterized by C and O isotope signatures different from that of speleothems in temperate environments. Apart from the cryogenic carbonates, several other freeze-related minerals have been identified in caves. By far, the richest diversity of cryogenic minerals occurs in gypsum-hosted ice caves.