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Sesha Sai, V. V.
- 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.
- Sheeted Dykes in Kandra Ophiolite Complex, Nellore Schist Belt, Andhra Pradesh-Vestiges of Precambrian Oceanic Crust
Authors
1 Petrology Division, Geological Survey of India, Southern Region, Hyderabad - 500068, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 74, No 4 (2009), Pagination: 509-514Abstract
Extensive field and petrological studies carried out in Kandra ophiolite complex (KOC) in the southern part of Nellore schist belt (NSB) revealed the existence of sheeted dykes in Kandra- Kondakuru-Gollapalli section. The sheeted dykes occur in the northern part of the complex and compositionally vary from medium-grained dolerites showing typical sub-ophitic texture to diabase dykes that are extremely fine grained aphanitic to fine-grained cryptocrystalline parallel basic dykes (varying in width from 4 cm to 1.25 m). These dykes show chilled margins on either side with the host dykes into which these are intruded. Veins of oceanic plagiogranite (0.5 × 5 m) are noticed in a major sheeted dyke. Occurrence of oceanic plagiogranite as ovoid / semicircular patches of 6 cm diameter resembling "immiscible droplets" within basic dykes is also noticed. The southern part of the complex is made of a major NW-SE trending cumulus gabbro that grades into olivine gabbronorite in its eastern part. The southern gabbros represent the plutonic component and form the deeper part of the complex. In this paper an attempt has been made to present the field, petrographic and mineral chemistry account of various lithounits that constitute the Kandra ophiolite complex in a succinct manner.Keywords
Sheeted Dykes, Kandra Ophiolite, Precambrian Oceanic Crust, Nellore Schist Belt, Andhra Pradesh.References
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