Physicochemical Conditions of Quartz Formation at the Bazov Gold-Ore Deposit (East Yakutia, Russia)

摘要

The evolution of the hydrothermal system forming the Bazov gold-ore deposit is traced by the data on the composition and properties of the fluid inclusions within the veined quartz. The gold-bearing quartz veins were formed under a moderate decrease of temperature from 290 to 230 degrees C and considerable decrease of pressure from 0.75 to 0.25 kbar. The pressure drop was accompanied by the volume crystallization of quartz from SiO2-saturated hydrothermal springs with the appearance of a residual fluid phase. In addition, the fluid composition was transformed from hydrocarbonate into hydrocarbonate-methane with the increase in the concentrations of chlorides of alkali and alkaline-earth metals (from 1 to 8 wt % of NaCl-equiv) along with the ore-forming elements (As, Sb, Fe, Zn, etc.). The pressure under which the formation of the gold-quartz veins occurred (about 0.25 kbar) limited the formation depth of the deposit to the range from 1 to 2.5 km (for the lithostatic and hydrostatic gradient, respectively).