Fluid inclusion characteristics of sapphires from Thailand

Fluid inclusion studies of Bo Ploi sapphire indicate three main inclusion types. Type 1 are vapour-rich CO2 with variable densities, up to about 0.86 g/cm(3) Type 2 multiphase (v+l+s) inclusions, which contain several daughter minerals hypersaline brine, and a CO2-rich vapour phase. Total homogenisation ranging from 920-1000 degrees C. Type 3 (silicate?) melts inclusions contain immobile vapour bubbles within an isotropic/weakly anisotropic phase of low relief. The bubbles move when the inclusions are heated beyond 800 degrees C. Some type 1, and most type 2 and 3 inclusions, appear primary, suggest the coexisting of three separate fluid phases;CO2 vapour, hypersaline NaCl brines (up to 73 eq. wt.% NaCl) and silicate melt were present during the growth of these sapphires. The results suggest magmatic source for these sapphires. However, the reliable PT trapping conditions is difficult to establish because many inclusions apparently exhibit decrepitation/leakage, which may indicate incorporation of sapphires and basalt magma.