ИСПОЛЬЗОВАНИЕ БИОТИТА КАК ОСНОВЫ ОЦЕНКИ ВАЖНЕЙШИХ ПЕТРОЛОГИЧЕСКИХ ПАРАМЕТРОВ КРИСТАЛЛИЗАЦИИ ГРАНИТОИДОВ ЗОЛОТОНОСНЫХ РАЙОНОВ ВЕРХНЕГО ПРИАМУРЬЯ

Abstract

Composition of biotite was used as the base to calculate parameters of the coexisting fluid phase: fO2, fHF / fHCl, fHF / fH20, fHCl / fH20, fH20 ; furthermore, an estimation of acidity-alkalinity and PT conditions of crystallization were carried out for the Late Mesozoic granitoids of gold-bearing areas of the Upper Priamurye (Russian Far East). Thus, it was revealed that granitoids have been crystallized from melts with the higher alkalinity, high potassium potential within the wide range of temperatures and pressures. The most common tendency in fluid regime of those granitoids was the growing activity of fluorine with decrease of chlorine participation at transition from the most productive monzodiorite-granite association (bearing gold and gold-rare-metal mineralization of skarn and hydrothermal types) to the Hayktisky and Chubaehinsky granitoid complexes with gold-rare-metal greisen mineralization, and then to the second phase granosyenite-granite association connecting the poor gold and gold-rare-metal mineralization. It is shown that, by composition of the fluid phase, the Upper Priamurye ore-magmatic granitoid systems with gold, gold-rare-metal and Mo mineralization are similar to granitoids of Cl-type ore-magmatic systems with Mo and Cu-Mo mineralization, but they differ from the fluorine-type systems with Sn, Sn-W rare-metal mineralization. Calculated composition of fluid phase for granitoids of the gold-bearing areas is similar to composition of fluid of magmatogenic gold-ore deposits, and according to experimental data it is favorable for gold concentration from the melt.