Petrology and Geochemistry of the Lamprophyric Rocks from the Bokaro Coalfield, Bihar and their Economic Potential

The dyke swarms intruding the Gondwana sequence in the east Bokara Coalfield, Bihar include lamprophyres and lamproites such as olivine lamproties, olivine-leucite lamproites and leucite lamproites. Basic intrusives and rare siderite rich carbonates (carbonatite ?) are also found. The olivine lamproites contain xenocrysts of olivine and rare xenoliths of harzburgite. Gold values upto 3.6 ppm on grab samples have been noted from the intrusive rocks in the area. These lampropbyric rocks are considered to have formed from a highly incompatible element enriched metasomatised mantle source probably of harzburgitic composition.