Low-Temperature Geyserite and Ephemeral Minerals of Mogoiskii Thermal Spring (Northern Transbaikalia, Baikal Rift Zone)

Five samples of modern mineral sediments were collected during hydrogeochemical study of the Mogoiskii thermal spring in Northern Transbaikalia. Two of them contain opal as the major component of geyserite; carbonates, fluorides, and sodium sulfates predominate in the other three. Calculations of deep temperatures showed that the formation of geyserite was associated with low-temperature hydrotherms and was explained by a decrease in their temperatures upon discharge. Precipitation of easily soluble brine minerals occurs on the evaporation barrier, and they may dissolve completely and disappear in the rainy periods.