Primary Silicate-Melt Inclusions in Olivine Phenocrysts from the Pavagad Igneous Suite, Gujarat

Fluid inclusion studies in olivine phenocrysts from alkali olivine basalt, iddingsite basalt and three-phenocryst basalt of the Pavagad igneous suite, an outlier of the Deccan Trap, indicate the presence of highly evolved primary silicate-melt inclusions with various daughter crystals of olivine, pyroxene, plagioclase and opaques. High temperature experiments using a heating stage indicate homogenization in the range of 1040 to 1240 °C. The gas bubble within these inclusions show melting close to the triple point forpure carbon dioxide and homogenize into liquid phase between 25 and 31 °C, denoting densities of 0,70-0.50 g/cm³. Trapping pressure estimated from CO₂ equation of state barometry is about 3.8 kbar, which translates to a depth of formation of ca. 10 km. This correlates well with an independent depth estimate of 10-14 km derived from combined melt and fluid homogenization data. The melt inclusion chardcteristics in the Pavagad suite suggesllhatlhe olivines equilibrated from a slow cooling system at high pressure conditions, the parental melt having a probable alkali olivine basalt composition.