Mineral Deposits and Underground Waters of the Caves of the Surkhantau Range (Uzbekistan)

The morphology, chemical, and isotopic composition of mineral deposits of three caves in the high-mountain region of the Surkhantau Range, located in the southeast of Uzbekistan, have been studied for the first time. The range is part of the southwestern spurs of the Hisar Range, which belongs to the Hisaro–Alay mountain system of the Southern Tien Shan. Four types of mineral deposits have been identified in the caves under consideration, the most significant of which are water-chemogenic formations. These deposits, morphologically represented by aggregates of gravitational, subaqueous, corallite–crystallictite crusts; cave powder; and fibrous formations, are composed mainly of calcite with inclusions of fluorapatite, barite, magnetite, goethite, rutile, plagioclase, epidote, and quartz. The deposits from the entrance of Vishnevsky Cave are distinguished by an increase in δ13С with almost identical δ18О values, which indicates negative temperatures. The data on the composition of groundwater are presented, and the conditions of their formation during speleolithogenesis are described based on hydrogeochemical and isotope studies. The isotopic composition of karst waters is indicative of the predominance of winter snow feeding. Large calcite aggregates and a thick layer of loose sediments in underground cavities provide evidence of the formation of caves in warm and humid climates by abundant watercourses with a feeding area in nonkarst sandstones, which are currently almost destroyed by erosion. The development of underground cavities continues in the bottom parts due to the activity of groundwater and in the entrance parts due to landslide processes.