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Ghosh, R. N.
- Gold Mineralisation around Babaikundi Area in Singhbhum Group of Rocks, Ranchi District, Jharkhand
Authors
1 Petrology Division, Geological Survey of India, Southern Region, Bandlaguda, Hyderabad - 500068, IN
2 Operations West Bengal, Geological Survey of India Complex, Korunamayee, Salt lake, Kolkata - 700 091, IN
3 39-B, Govinda Auddy Road, Kolkata - 700027, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 64, No 2 (2004), Pagination: 133-138Abstract
The volcano-Sedimentary assemblage of rocks belonging to the Singhbhum Group of Proterozoic age is exposed around Babaikundi, in Ranchi district of Jharkhand state. The east-West trending Tamar-Porapahar shear zone passes north of Babaikundi area. The Chotanagpur Granite Gneissic Complex (CGGC) is to the north of the area, while the rocks of the Dalma Volcanic Belt (DVB) are exposed towards the south. The rocks of the area have undergone polyphase deformation and subjected to metamorphism ranging from greenschist to lower amphibolite facies.
Gold mineralisation is of epigenetic type and is mainly confined to the lensoidal sheared quartz vein traversing the litho-Contacts of the quartz-Mica schist and amphibolite of the Singhbhum Group. The attitude of the mineralised quartz vein is in conformity with the regional schistosity trending ENE-WSW. At the footwall contact of the mineralised quartz vein extensive wall rock alteration halos are observed in the amphibolite unit in the fOrm of pervasive biotitisation, carbonatisation, sericitisation, chloritisation, sulphidisation and Silicification. Ore microscopic studies of the mineralised quartz vein reveal that the native gold is associated, at places, with pyrrhotite and sphalerite. Pyrite and chalcopyrite along with magnetite are also present within the mineralised quartz vein. The paper presents the salient details on the occurrence of primary gold mineralisation in Babaikundi area.
Keywords
Gold Mineralisation, Singhbhum Group, Babaikundi, Jharkhand.
- PGE Distribution in Chromite Placers from Andaman Ophiolite and its Boninitic Parentage
Authors
1 Geological Survey of India, Opn: WB-SK-AN, ER, Geological Survey of India, 5th floor, North Building, Bhubignan Bhawan, DK-6 Block, Salt Lake, Kolkata - 700 091, IN
2 Geology Department, Indian School of Mines, Dhanbad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 62, No 6 (2003), Pagination: 671-679Abstract
Chromite placers occurring in Rutland coast of Andaman and Nicobar Islands, India, show PGE incidence. Serpentinised dunite containing thin stringers/lenses of chromite occurring adjacent to placer was possibly the source rock of the chromite placers. Chemical analysis of these chromite placers show PGE elements incidence in the range: Ru <10-56 ppb, Ir <10-12 ppb, Rh <10-14 ppb, Pd <10-136 ppb, Pt <10-28 ppb. Normalization of these PGE values against CI-chondrite indicates enrichment of Ir and Ru and depletion of Rh and Pt, a typical character of ophiolitic chromite. Except few Pd values, the PGE values depict highly fractionated PGE distribution pattern. High Nig-olivine (Fo92-90)and highly fractionated PGE pattern may suggest derivation of the source rock from boninitic melt. Ru-Ir-Os bearing sulphides or alloys were crystallised at early magmatic stage, Pt, Pd were remobilized during hydrothermal activity and concentrated in serpentine.Keywords
Chromite Placers, PGE Incidence, S-Undersaturation, Boninite, Rultand, Andamans.- Li-Cs-Rb Mineralisation in Proterozoic Zoned Pegmatites of Beku, West Bengal
Authors
1 Geological Survey of India, Op. WB-S-A&N, GSI Office Complex, DK-Block, Sector 11, Salt Lake City, Kolkata -700 091, IN
2 Geological Survey of India, Zorem building, Nongrim Hills, Shillong - 793 003, IN