Thermal Structure of the Lithosphere Beneath the Deccan Trap along the Western Indian Continental Margin: Evidence from Xenolith Data

Abstract

Abstract Late alkaline lamprophyre-intrusives from the Deccan Trap along the western Indian continental margin entrain rare granulite and pyroxenite xenoliths some of which contain kaersutite ± phlogopite ± apatite ± scapolite ± sulphides providing evidence orfluid induced metasomatism. P-Testimates on carefully selected mafic granulite and pyroxenite xenoliths define a palaeogeotherm from 550°C, 5 kb to -830°C, 8.5 kb for the Mumbai region along the western continental margin. This elevated geotherm suggests advective heat transfer from magmas ponded near the crust mantle boundary. Xenolith petrology coupled with seismic data suggests that the lower crust beneath Mumbai consists of mafic granulites under- and intra-plated by pyroxenites. Spinel peridotites interlayered with pyroxenites predominate below -20 km. The seismic Moho is located within the layered pile.