THE EVOLUTION OF THE FLUID PHASE DURING THE CRYSTALLIZATION OF GRANITE TYPES: SALMI PLUTON, KARELIA, RUSSIA

Abstract

Two main geochemiscl types of granites are distingushed in the Salmi pluton: 1) ovoid biotite-hornblende granites, 2) non-ovoid biotite granites. The first one is characterized by higher CO2, CO and CH4 concentrations. The second type is rich in fluorine and shows similarities with rare metal Phanerozoic granites. Both granite types began to crystallize when Pf, tot, but non-ovoid granites, which crystallized in a wider temperature range, reached conditions Pf, > POtot at the final stage. The mole fraction of carbon group gases (CO2, CO and CH4) decreases and that of H2O increases in all granites from early crystallizing minerals to those of late crystallization.Compositional differences between ovoid biotite-hornblende and non-ovoid biotite granites are due to differences in the protolith composition.