Crystallization history of primitive Deccan basalt from Pavagadh hill, Gujarat, western India

The Three Phenocryst Basalts' (TPB) from Pavagadh hill constitute one of th e most primitive basalts in Deccan traps. Electron microprobe analyses of p henocryst minerals from the TPB reveal that the Fo % of olivine varies from 89 to 68, the dinopyroxene grains are diopside/salite or augite and the Cr # [Cr/ (Cr+Al)] in spinel is about 0.65. The An content of feldspar varies from 63 to 67. The mineral chemical data allow us to infer that olivine. an d spinel crystallized early, and when olivine attained Fo76-73%, the crysta llization of clinopyroxene was initiated. Plagioclase crystallization occur red at the late stage. It is indicated that the source region of the TPB ma y possibly be undepleted mantle (Iherzolite zone) at about 85 km depth and 27 kbar pressure, where Cr# of spinel is about 0.47.