Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Radha R. Das ¹, K. K. Dwivedy ¹, T. R. Mahalingam ², C. K. Mathews ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Begumpet, Hyderabad - 500016, IN
2 Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu - 603 102, IN

Abstract

The relative abundance of radiogenic lead varies depending on the mineralogical characteristics of the ore. In high uranium containing coaly matter, radiogenic lead is > 80% of the total, whereas in a composite ore, as much as 60% of the total is of the initial common lead. The uranium-lead 'apparent ages' are in the range of 25 Ma to 95 Ma and are related to the mineralogical assemblage in the ore. The most recent of the uranium mineralization, of 'apparent age'-25Ma is with the coaly matter separates that contain considerable amount of pyrite. The variations in the abundance and distribution of radiogenic lead isotopes and the resultant orderly changes in 'apparent ages' of uranium mineralizations in different type of mineral separates are attributed to the existing favourable conditions in the ore for movement of uranium from the rock and preferential concentration and retention in the coaly matter, leading to more than one stage uranium mineralization.

Keywords

Geochemistry, Lead Isotope, U-Pb Apparent Ages, Meghalaya.

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Sunil Kumar ¹, S. K. Dash ¹, U. P. Sharma ¹, K. Ramadoss ¹, Rajendra Singh ², K. K. Dwivedy 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

Univariate and multivariate statistical analyses, especially correlation study and factor analysis of uranium and other major ions in the groundwater of Chenchalapalle-Mulapalle area, known for its fracture controlled uranium mineralization, in the southwestern crystalline margin of Middle-Upper Proterozoic Cuddapah basin have revealed - (i) several well defined and distinct anomaly zones of > 200, > 500, > 1000 ppb of uranium, (ii) enriching factors like TDS(Ec), HCO₃^-, Na⁺, K⁺, Ca⁺² , Mg⁺², Cl^-, SO₄^-2 have poor to negligible influence on high uranium content and (iii) factor-3, identified as "mineralization factor" has high loading for uranium (0.948). The study on saturation indices of several uranium and other minerals indicated undersaturation for most of the aqueous uranium species, except for a few hydroxides. Particularly, schoepite (2UO₃.5H₂O) has low to moderate degree of supersaturation in samples from major anomalous zones.

Based on the distinctive hydrogeochemical attributes and geological and structural favourability factors, the tracts in the vicinity of Varikuntapalle (VKP). Dapepalle (DPL) and Pulikunta (PLK) villages, between Chenchalapalle-Mulapalle area in the southwestern crystalline margin of Cuddapah basin, are designated as potential target areas for detailed exploration.

Keywords

Hydrogeochemistry, Uranium, Groundwater, Cuddapah Basin, Andhra Pradesh.

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S. R. Shivananda ¹, K. K. Dwivedy ¹, Ravi Kaul ¹

Affiliations
1 Atomic Minerals Division, Begumpet, Hyderabad 500 016, IN

Abstract

Uranium mineralisation in Domiasiat sandstone is due to migration and fixation by biogenic processes, and leaching and redistribution by surface and groundwater. Fine-sized pitchblende and coffinite are associated with carbonaceous matter and pyrite. Characterization of the extractable uranium indicates that its nature varies from sample to sample and appears to be dependent on pH, Eh and the amount of soluble sulphates in them and to some extent on gangue minerals like calcite which can neutralise the acid component. It is inferred that alteration of sulphides and formation of sulphates results in an acidic condition favouring mobilisation.

Keywords

Uranium, Khasi Hills, Meghalaya.

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Harsh K. Gupta ¹, K. K. Dwivedy ²

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 Atomic Minerals Division, Begumpet, Hyderabad - 500 O16, IN

Abstract

Drilling at Killari in the Meizoseismal area of the 1993 Latur earthquake has revealed that the Deccan Basalt sequence here is 338 m thick, andis underlain by Peninsular Gneiss basement with an intervening 8 m Infra-Trappean sequence.

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I. V. Sastry ¹, T. P. S. Rawat ¹, K. K. Dwivedy ²

Affiliations
1 Atomic Minerals Division Shillong - 793 001, IN
2 Atomic Minerals Division Hyderabad - 560016, IN

Abstract

Basaltic andesites of Precambrian age are reported and described for the first time from Garo Hills, Meghalaya. These volcanics occur as xenoliths within Proterozoic granitoids. Petromineralogical and petrochemkal characters of the volcanics revealed them to be basaltic andesite. The basaltic andesite are observed both as porphyritic and aphyric types.

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