Mineralogy of a Jamdoba-XI lamproite dyke from Jharia basin, Jharkhand, India

The Gondwana sedimentary sequences of Damodar Valley in eastern India are intruded by the potassic intrusives of Cretaceous age. This study focuses on the mineralogy of one such potassic-rich dyke occurring in an underground Jamadoba colliery seam XI in Jharia basin, Jharkhand, India. It consists of olivine, phenocrystal phlogopite, microphenocrysts of phlogopite, apatite and diopside embedded in the groundmass comprising phlogopite, apatite, amphibole, ilmenite, rutile and K-feldspar. The presence of forsteritic olivine, low Al and Fe rich phlogopite, low Al-Na diopside, Al-poor and Ti-rich amphiboles and Fe-rich K-feldspar indicate the lamproitic character of the potassic dyke. Using a mineralogical-genetic classification scheme, the Jamadoba-XI dyke is classified as an olivine-phlogopite-apatite-diopside-amphibole-feldspar lamproite.