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Bhattacharyya, D.
- Gold Potential of Epithermal Breccia along the Deldar- Kui-Chitrasani Fault in South Delhi Fold Belt, Southwest Rajasthan and Northern Gujarat
Authors
1 Geological Survey of India, A.M.S.E. Wing, Central Zone, Seminary Hills, Nagpur - 440 006, IN
2 Geological Survey of India, Western Region, 15-16, Jhalana Dungri, Jaipur - 302 004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 57, No 2 (2001), Pagination: 149-156Abstract
The Deldar-Kui-Chitrasani (DKC) fault is a brittle structure manifested by anastomosing system of fractures in the southwestern part of the South Delhi Fold Belt (SDFB). Based on the identification of cross-fibre and 'jigsaw puzzle' type structures, presence of vugs lined with cryptocrystalline quartz, replacement of calcite by chalcedonic quartz and evidences of argillic alteration, the breccia along the fault is recognised by present workers as epithermal breccia. Lithogeochemical sampling of the breccia reveals that, besides moderate base metal signatures, gold values are consistently present in significant concentrations comparable to regional anomalies associated with epithermal gold deposits in the United States. In view of the high proportion of magmatic rocks in the southwestern part of the SDFB, the DKC fault zone is considered a favourable target for searching epithermal type of gold mineralisation.Keywords
Economic Geology, Epithermal Breccia, Lithogeochemistry, Gold Anomaly, Faults, Shear Zone, South Delhi Fold Belt, Rajasthan, Gujarat.
- Uranium Mineralisation Associated with Felsic Volcanism at Mohar, Shivpuri District, Madhya Pradesh
Authors
1 Atomic Minerals Directorate for Exploration and Research, Bangalore, 560 072, IN
2 Atomic Minerals Directorate for Exploration and Research, Shillong – 793 011, IN
3 Atomic Minerals Directorate for Exploration and Research, Hyderabad – 560 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 78, No 1 (2011), Pagination: 57-62Abstract
Several small lensoidal bodies of felsic volcanics are exposed in a curvilinear pattern within the brecciated granitoids of Bundelkhand Gneissic Complex (BGC) at Mohar. Sub-surface data reveals extensive presence of these felsic volcanics below the sediment of Vindhyan Supergroup. It occurs like a sheet with thickness varying from 12 m to 134 m. Its lateral extent has been traced upto 4.8 km. Multiple flows of felsic magma are identified based on colour, granularity, cross cutting relations and cyclic distribution of multiple vesicular bands along the entire thickness of felsic magma. The felsic rock contains upto 13.21% K2O. Chemical composition of these felsic volcanics varies across the column. Petrographically and chemically all these felsic volcanics are identified as rhyolite or rhyolite tuff.
Significant uranium mineralisation of 0.0165% eU3O8 average grade has been intercepted for 11.10 m thick with <0.005% ThO2 within the felsic rock. Radiometric assay of a mineralised intercept (15 cm length) has revealed up to 0.15% U3O8 with disequilibrium in favour of parent. Uranium occurs as disseminated grains of coffinite - (Y) associated with pyrite, chalcopyrite, galena, molybdenite, hematite, fluorite, anglesite and cerrusite. Mineral assemblage and mode of occurrence of the uranium and other minerals in the host rock indicates its hydrothermal nature. This is the first reported uranium occurrence from the volcanogenic environment of Bundelkhand.