Mineralogical and Geochemical Characteristics of the Basal Quartz - Pebble Conglomerate of Dhanjori Group, Singhbhum Craton, India and their Significance

he basal quartz-pebble conglomerate of Dhanjori Group of Singhbhum-Orissa craton is characterised by a distinct heavy mineral assemblage of pink zircon, chromite, pyrite, monazite and rutile-silicate intergrowth. Statistical analysis of morphometric features of zircons shows that they are significantly different from those found in Older Metamorphic Group and Older Metamorphic Tonalite Gneiss, but they have resemblance to those found in Singhbhum Granite. The trace and REE characteristics 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 mixed provenance with an ultramafic component ofkomatiitic affinity (older greenstones) in the granite complex. The relative proportion of older greenstones was higher towards western and southern margins of the Dhanjori basin.