MINERALOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE BASAL QUARTZ-PEBBLE CONGLOMERATE OF DHANJORI GROUP, SINGHBHUM CRATON, INDIA AND THEIR SIGNIFICANCE

The basal quartz-pebble conglomerate of Dhanjori Group of Singhbhum-Or issa craton is characterised by a distinct heavy mineral assemblage of pink zircon, chromite, pyrite, monazite and rutile-silicate intergrow th. Statistical analysis of morphometric features of zircons shows tha t they are significantly different from those found in Older Metamorph ic Group and Older Metamorphic Tonalite Gneiss, but they have resembla nce to those found in Singhbhum Granite. The trace and REE characteris tics of the conglomerates, and the morphology and chemistry of zircon, identify the Singhbhum Granite Complex as the predominant source rock . At the same time, abundant detrital chromite, the positive trend of Cr-Ni and Cr-Co plots, and high Cr/Th ratios of the QPCs suggest a mix ed provenance with an ultramafic component of komatiitic affinity (old er greenstones) in the granite complex. The relative proportion of old er greenstones was higher towards western and southern margins of the Dhanjori basin.