Informatics Publishing Limited

A. K. Roy ¹, A. Saha ², R. P. Singh ³, R. M. Sinha ³

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, New Delhi, IN
2 Atomic Minerals Directorate for Exploration and Research Jamshedpur, IN
3 Atomic Minerals Directorate for Exploration and Research, Hyderabad-16, IN

Abstract

A radioactive fault breccia zone trending N30°E is exposed intermittently within the puru granite dome, near Kuchanapalle village in the NE margin of Cuddapah basin. A major part of the fault zone is under soil cover. Within this fault zone, a dark coloured ferruginous and uraniferous fault breccia is exposed over an area of 150m x 2.5m. In order to trace the continuity of the concealed fault zone, the uraniferous breccia zone was tested by closed circuit soil-gas radon (CCT) measurement, solid state nuclear track detection (SSNTD) survey, and trace element analysis of augur-hole soil samples. Radon levels in 164 auger holes vary from 9 to 863 per 50 sec. The alpha track density on cellulose nitrate films used in SSNTD surveys varies from 27 to 820 per sq. mm. The iso-alpha track density map has confirmed the anomalous patterns obtained by the soil-radon survey.

Trace element data of soil samples have been processed using R-mode factor analysis of correlation matrix. These data along with radon and SSNTD surveys have thus been found to be very effective in delineating the extension of the radioactive breccia zone under soil cover, up to 1200 m towards north.

Keywords

Economic Geology, Exploration Geochemistry, Soil Radon Surveys, Uranium, Cuddapah Basin, Andhra Pradesh.

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A. Panneer Selvam ¹, R. N. Prasad ², R. Dhana Raju ¹, R. M. Sinha ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560072, IN
2 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500016, IN

Abstract

Metaluminous granitoids of the South Khasi batholith (SKB) in the West Khasi Hills district of Meghalaya define a Rb-Sr whole-rock isochron age of 757 ± 60 Ma, with (⁸⁷Sr/⁸⁶Sr) of 0.71069 ±0.00092. SKB and other granitoids of Meghalaya like Mylliem, Nongpoh and Kyrdem have many common features such as the presence of basic enclaves of hornblende gneiss and amphibolite, lateto post-tectonic nature, predominance of biotite amongst mafic silicates, overall metaluminous nature and high (⁸⁷Sr/⁸⁶Sr) of more than 0.709. All these indicate much similarity in the genesis of their melts due to partial melting of lower crustal rocks. The Rb-Sr isochron ages of SKB and other granitoids in Meghalaya point to a major tectonomagmatic activity during ca. 760-480 Ma, which is almost coeval with ca. 800-500 Ma Mid-Upper.Pan-African activity. The data, thus imply the possible imprint of the widespread Pan-African activity in northeastern India, besides southern India.

Keywords

South Khasi Batholith (Meghalaya), Rb-Sr Isochron Age, Geochronology, Pan-African Activity.

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V. P. Saxena ¹, R. M. Sinha ¹, O. R. Yadav ¹, R. V. S. Sesha Rao ²

Affiliations
1 AMD Complex, Begumpet, Hyderabad - 500 016, IN
2 AMD Complex, Civil Lines, Nagpur - 440 001, IN

Abstract

Signatures of concealed Unconformity-Related uranium mineralization at the contact of Chhotanagpur Granite Gneissic Complex [CGGCJ/Mahakoshal and Lower Vindhyan Semri sequence have come to light at Baskati, in Vindhyan- Mahakoshal Basin, following a multipronged exploration strategy. Systematic lithogeochemical sampling brought out uranium halos and most significant signals with concentration sufficiently above the normal background closely associated with breccias along reactivated faults and fractures occurring parallel and also oblique to the unconformity contact extending for a strike length of 17 km. Alteration halos and signatures like hematitisation, chloritisation and ilhtisation characterize the vicinity of these reactivated faults and fractures Geochemical study indicates a hypogene source for mineralizing fluids supported by geology, structure and lithogeochemistry and an 'Unconformity-Related uranium mineralization model' has been envisaged with the target area narrowed down for subsurface exploration.

Keywords

Geochemical Modelling. Uranium Mineralization, Unconformity, Alteration Halos, Baskati Area, Madhya Pradesh.

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A. V. Jeyagopal ¹, R. V. Singh ¹, P. Nageswara Rao ¹, V. P. Saxena ¹, R. M. Sinha ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 0 16, IN

Abstract

Recent geological studies have brought out the presence of hitherto unknown Cumbum shale/Phyllite in the Julakallu-Pinneli area, Guntur district, Andhra Pradesh within the Palnad Sub-Basin of the Cuddapah basin. Cumbum shale/Phyllite and quarzite was found to rest above the Narji Limestone at southeast of Petasannigandla. This has necessitated northward shift of thrust boundary separating the Cumbum Formation and Narji Limestone from earlier known location. Subsurface data have confirmed larger thickness of the Narji Limestone than that reported in the literature. Geochemical characteristics of the Cumbum shale/Phyllite have indicated its deposition as first cycle of sediments in a tectonically active setting. This is supported by the depletion of immobile oxide Al₂O₃ and enrichment of mobile oxide CaO in the Cumbum shale. The A-CN-K plot indicates that provenance for shale/Phyllite could be granodiorite to granite in composition, which is also supported by petrological observations. The field, petrological and geochemical interpretations have brought out much new information on this part of the basin, which necessitates, revision of the geology of area.

Keywords

Cumbum Formation, Narji Limestone, Thrust Boundary, Cuddapah Basin, Julakallu, Andhra Pradesh.

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I. Bhattacharjee ¹, A. R. Mukundhan ¹, A. S. Sachan ¹, K. N. Tiwary ¹, R. M. Sinha ², R. K. Gupta ²

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy Nagpur- 440 001, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy Hyderabad - 500 016, IN

Abstract

No Abstract.

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P. Nageswara Rao ¹, Anjan Som ¹, T. Perumal ¹, P. B. Maithani ¹, V. P. Saxena ¹, R. M. Sinha ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 016, IN

Abstract

Recent investigations have brought out significant uranium occurrences (up to 0 65% U₃0₈)spread over as discontinuous zones (up to 300 m × 280 m × 1-3 m) over an area of about 7 km × 2 km along the northern part of Palnadu Sub-Basin. The radioactive zones are exposed along the Upper Proterozoic unconformity contact between the basement granite and the Banganapalle quartzite near Lavur Tanda, Jaitram Tanda, Boligutta Tanda, Rallavagu Tanda and Gandhi Nagar villages in Nalgonda district, Andhra Pradesh. These findings are reported in this note along with some features of mineralisation.

Keywords

Uranium Occurrence, Proterozoic, Palnadu Sub-Basin, Andhra Pradesh.

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P. Nageswar Rao ¹, Prakash Kumar ¹, S. K. Srivastava ¹, R. M. Sinha ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 016, IN

Abstract

No Abstract.

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B. S. Bisht ¹, P. Rajasekaran ¹, R. M. Sinha ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research Department of Atomic Energy, Begumpet, Hyderabad- 500016, IN

Abstract

Aqueous bi-phase fluid inclusions in quartz from mineralised vein, granite and pebbly quartzite have been studied to decipher physico-chemical conditions of the unconformity-related uranium mineralisation at Lambapur- Peddagattu area in the northern fringe of Cuddapah basin. Fluid inclusions in vein- and granitic- quartz show significant similarity in phase ratios and homogenisation temperatures, though they differ in the mode of origin. main population of inclusions in vein quartz is of primary origin, while in granitic quartz it is of secondary origin. The size of fluid inclusions generally varies between lOpm to 20pm, with low gas to liquid ratios corresponding to high degree of fill (F=0.8 to 0.9). Inclusions in vein- and granitic- quartz homogenise to liquid phase between 140°C to 240°C (mode 150°C to 170°C) [T_H]. Similar temperature of homogenisation has been obtained in quartz of pebbly quartzite. The ice melting temperatures in vein quartz are in the range of -2°C to - 10°C [T_M] equivalent to salinity of 1-14 wt% eNaCl and in granitic quartz these are in the range of -6°C to -14"C[T_M] corresponding to salinity values of 10-18 wt% eNaC1. The low temperature fluid inclusions homogenising at similar range of temperatures but showing variable salinity suggest mixing of isothermal fluids of contrasting salinity. It is likely that uranium precipitated from the interaction of cooling low saline hydrothermal solution at the temperatures of 150-170°C with high saline mineralising fluid transported by recirculating meteoric water.

Keywords

Fluid Inclusions, Microthermometry, Uranium Mineralisation, Cuddapah Basin, Andhra Pradesh.

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K. S. Mishra ¹, P. Jagadeesan ¹, K. K. Pandey ¹, V. P. Saxena ², R. M. Sinha ²

Affiliations
1 AMD, CR, Nagpur - 440 001, IN
2 AMD, Hyderabad-500 016, IN

Abstract

Rare earth element (REE) geochemistry of uranium bearing columbite-tantalite and multiple Nb-Ta oxide phases from the Pandikimal-Jangapara pegmatites, Jharsuguda district, Orissa have been studied and evaluated columbite-tantalite from these areas contain low ∑REE (100-1000 ppm) with LREE/HREE_CN<0.5 and minor amounts of uranium (0.3-0.6 % U₃O₈). Multiple oxide phases (yttrotantalite, samarskite, microlite and fergusonite) contain elevated amounts of U (10-11 % U₃O₈) and REE (19-28 %) with HREE>LREE. Plot of ∑REE vs. Chondrite-Normalised LREE/HREE shows positive correlation in 'U' rich multiple oxides compared to those from columbite tantalites which tend to show a negative correlation. The LREE/HREE ratio is 0.24 with negative Eu anomaly (Eu/Eu = 0.1) indicating evolved nature of these pegmatites.

Keywords

Rare Earth Element (REE), Columbite-Tantalite, U-Bearmg Multiple Oxide Phases, Pandikimal, Orissa.

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