Thermal structure of the lithosphere beneath the Deccan Trap along the western Indian continental margin: Evidence from xenolith data

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 of fluid induced metasomatism. P-T estimates on carefully selected mafic granulite and pyroxenite xenolith s define a palaeogeotherm from 550 degrees C, 5 kb to similar to 830 degree s C, 8.5 kb for the Mumbai region along the western continental margin. Thi s elevated geotherm suggests advective heat transfer from magmas ponded nea r 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 pyro xenites. Spinel peridotites interlayered with pyroxenites predominate below similar to 20 km. The seismic Moho is located within the layered pile.