Mineral sediments of the Kholodnyy grotto cave (Bzyb gorge, Abkhazia) and 13С carbon and 18О oxygen isotope composition of karstogenic carbonates

The article is devoted to the results of the study of the mineral and isotopic composition of speleothems of the of the Kholodnyy Grotto cavein the Bzyb gorge of Abkhazia. The cavity was mapped and various types of secondary mineral deposits were recorded. The following mineral formations (speleothems) have been established in the cave: Mondmilch, corallites, guhrs, carbonate breccias, biogenic phosphates. Attention is drawn to the abundance of allogeneic mineral inclusions in drip calcite associated with the weathering products of igneous rocks (zircon, potassium feldspar, ilmenite, rutile, monazite, apatite). The source of these minerals is presumably the weathering crust of the Middle Jurassic volcanics. The oxygen isotope composition of all studied carbonates reflects the participation of meteoric waters. Moreover, the isotopic composition of carbon is subject to significant variations associated with kinetic fractionation (CO2 degassing). Based on the results of petrographic and isotopic studies, an attempt was made to typify speleothems according to the nature of their feeding and the characteristics of crystallization. Also, the cave revealed phosphate mineralization in the form of dark brown thin-layered crusts of hydroxylapatite, formed in place of old guano deposits.