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Dhurandhar, A. P.
- Petrology and Geochemistry of Meso-Proterozoic Arenaceous Sediments of the Barapani Formation of Shillong Group in Parts of Meghalaya and Assam
Authors
1 Atomic Minerals Directorate, Department of Atomic Energy, Bangalore, IN
2 Atomic Minerals Directorate, Department of Atomic Energy, Hyderabad, IN
3 Atomic Minerals Directorate, Department of Atomic Energy, Nagpur, IN
4 Atomic Minerals Directorate, Department of Atomic Energy, Shillong, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 5 (2008), Pagination: 683-692Abstract
In the Proterozoic Shillong Group, the Meso-Proterozoic arenaceous Barapani Formation, unconformably overlies the Paleo proterozoic Tyrsad Formation. Argillaceous quartz arenite, quartzite and quartz wacke are the constituents of Barapani Formation, in both Meghalaya plateau and Mikir Hilis in Assam. Samples from both the domains contain same type of detrital grains. Monocrystalline quartz forms about 70 to 90 % and feldspars and lithic fragments form minor part of the framework constituents. Sericite is the major mineral in matrix. Geochemical data (major and trace elements) of these arenites show overall similar elemental composition of all the samples from both Meghalaya plateau and Mikir Hills, Assam, indicating constancy of provenance. However, samples from the Mikir Hills as compared to that from Meghalaya Plateau show depletion in FeO(t), CaO, and MgO and enrichment in V, Cr, Co, Ni and Cu. Samples from both the Meghalaya plateau and Mikir Hills indicate a passive margin tectonic setting of sedimentation.Keywords
Petrology, Geochemistry, Mid-Proterozoic, Barapani Arenite, Meghalaya, Mikir Hills, Assam.
- Geochronology and Petrochemistry of the Dubha Granite, Sonbhadra District, Uttar Pradesh
Authors
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Shillong- 793 01 1, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Hyderabad 500 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 65, No 4 (2005), Pagination: 459-467Abstract
The Rb-Sr isotopic systematics and petrochemistry of Dubha Granite occurring in the migmatite complex of Chhotanagpur Granite Gneiss Complex (CGGC) in parts of Sonbhadra district, Uttar Pradesh have been investigated.The Rb-Sr data on the whole rock samples (n=13) yields an isochron age of 17545±166 Ma with initial 87Sr/86Sr ratio of 0.7043±0.011.
The Dubha Granite is composed of quartz (34.2%), K-feldspar (37.4%), plagioclase (An2-40) (16.1%), biotite (9.6%), hornblende (1.9%), and accessory garnet, sphene, apatite, zircon, anatase, ilrnenite, magnetite, goethite, and chalcopyrite (0.8%). It is an anorogenic, metaluminous, ilmenite series, rift related granite, enriched in Ni, Cr, Co, V, Zn, Cu, Rb, Ba, Zr, Nb, Ce, U, Th and depleted in Sr and Y as compared to the normal granite. The Dubha Granites may have been generated by the anatexis of lower crustal material in the vicinity Son Narmada South Fault (SNSF).