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Shah, V. L.
- Mineralogical and Geochemical Characteristics of the Basal Quartz - Pebble Conglomerate of Dhanjori Group, Singhbhum Craton, India and their Significance
Authors
1 Ore Dressing Section, Bhabha Atomic Research Centre, Hyderabad 500 016, IN
2 Analytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, IN
3 Atomic Minerals Division, Begumpet, Hyderabad 500 016, IN
4 Prem Mandir, Anugrah Narayan Road, Kadamkuan, Patna 800 003, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 51, No 6 (1998), Pagination: 761-776Abstract
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.Keywords
Mineralogy, Geochemistry, Quartz-Pebble Conglomerate, Dhanjori Group, Singhbhum-Orissa Craton.
- Stratigraphic Succession of Precambrian of Singhbhum: Evidence from Quartz Pebble Conglomerate
Authors
1 Prem Mandir, Anugrah Narayan Road, Kadamkuan, Patna - 800 003, IN
2 Ore Dressing Section, Bhabha Atomic Research Centre, Hyderabad - 500 016, IN
3 Atomic Minerals Division, Begumpet, Hyderabad - 500 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 49, No 5 (1997), Pagination: 577-588Abstract
Though the stratigraphic succession in the Precambrian of Singbhum-Orissa region of the Indian shield given by Saba et al. is widely accepted, there are several contentious issues whieh have been hotly debated over the years. The occurrence of uraninite and pyrite bearing quartz-pebble conglomerate at the base of Iron Ore Group (lOG) as well as the Dhanjori Group has indicated the necessity for a revision in the stratigraphic succession in view of the temporal significance of such conglomerate the world over.
The conglomerate contains a significant population of zircon, chromite and shows a typical minor and trace element composition. The zircon has morphometric properties similar to those found in several members of the Singhbhum Granite Complex. The presence of detrital chromite and high Cr content indicate the occurrence of older mafics/ultramafics in the provenance along with the Singhbhum Granite Complex. It is suggested that some mafic and ultramafic members presently grouped within the IOG may represent such "older greenstones". The IOG as well as the Dhanjori Group with basal QPC horizon lie over a basement of Singhbhum Granite-Greenstone Complex. From available evidences it is surmised that both IOG sensu stricto (the BIF sequence and associated ferruginous cherts. greywackes and acid-intennediate volcanics) and the Dhanjori Group represent late Archaean (2500-3000 Ma) supracrustals and hence are nearly coeval. The Singhbhum Group north of the shear zone represents early Proterozoic supracrustals.