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Reddy, N. S.
- Tungabhadra Kimberlite Field, Kurnool District, Andhra Pradesh
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Authors
Affiliations
1 Geological Survey of India, Southern Region, Hyderabad – 500 068, IN
1 Geological Survey of India, Southern Region, Hyderabad – 500 068, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No Spl Iss 3 (2007), Pagination: 611-618Abstract
The diamondiferous Upper Proterozoic conglomerates and the associated sandstone beds display sedimentary structures that are suggestive of provenance in the northwest, i.e. towards the Tungabhadra river drainage basin. Multidisciplinary surveys in this region have led to the discovery of a kimberlite body (350 m x 470 m), concealed under alluvial soil spread on the left bank of the Tungabhadra River near Mantralayam. The study area, represented by the granitoids of Peninsular Gneissic Complex with remnants of Gadwal schist belt, presents a domal upwarp that plunges into the river. The domal surface displays intense fracturing with prominent NW-SE/WNW-ESE and subordinate NE-SW trends, which show marked preponderance and dilation on the northern low angle plunge parts. Traverses coupled with extensive stream sediment sampling and the study of specific mineral chemistry is suggestive of presence of kimberlite, which is supported by actual recovery of micro-diamonds from the yellow ground. The kimberlite contains mantle nodules of phlogopite-bearing websterite and siliceous mica-garnet-chrome diopside bearing lherzolite; the selective non-silicification of interstitial chrome diopside in the latter being enigmatic. The silicification of these mantle nodules could be due to the emplacement of kimberlite into a surface water body and subsequent action of silicasaturated groundwater.Keywords
Kimberlite, Microdiamonds, Mantle Nodules, Tungabhadra River, Kurnool District, Andhra Pradesh.- Pillowed Spilitic Basalts from the Tadpatri Formation of Cuddapah Basin
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Authors
Affiliations
1 Petrology Division, Geological Survey of India, Mukharamjahi Road, Hyderabad 500 001, IN
1 Petrology Division, Geological Survey of India, Mukharamjahi Road, Hyderabad 500 001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 32, No 1 (1988), Pagination: 65-67Abstract
Pillow structures are noticed in the spilitised basalts occurring within the shales of Tadpatri Formation indicating subaqueous eruption as against the traditional notion of subaerial volcanism in Cuddapah basin. The basalt is enriched in alkalis and silica and depleted in calcium and magnesium. The pillows are separated by a black siliceous inter-pillow material. The pillowed basalt is under1ain by a massive Java with a thin intervening bed of aphanitic rock and nodular limestone. This pillowed and massive lava flow appears to extend for long distances in the Cuddapah basin.- 'Pseudo-Charnockites' from the Greenstone Terrain of Northeast Dharwar Craton
Abstract Views :219 |
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Authors
Affiliations
1 Centre for Earth Science Studies, Trivandrum 695 031, IN
2 Geological Survey of India, Hyderabad 500 001, IN
1 Centre for Earth Science Studies, Trivandrum 695 031, IN
2 Geological Survey of India, Hyderabad 500 001, IN