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

Sunil Kumar ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Bangalore 560 072, IN

Abstract

No Abstract.

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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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Sunil Kumar ¹, R. Dhana Raju ², H. M. Varma ², N. K. Dougall ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Skyline View, G S Road, Mawtai, Shiliong 793 008, IN
2 Atomic Minerals Division, Department of Atomic Energy, 110-153, Begumpet, Hyderabad 500 016, IN

Abstract

Rocks of alkaline affinity, namely cancrinite-tinguaite and K-rich trachyte occur as dykes in the Plecambrian gneissic and migmatitic country rocks in the Nongcharam. Darugiri area of the East Garo Hills district Meghalaya Cancrinite-tinguaite is characterized mineralogically by the presence of phenocrysts of high temperature K-feldspar cancrinite nepheline aegirine-augite aeggitine, diopside, biotite and occasional barkevikite in a groundmass consisting of K-feldspar albite anorthoclase, aegirinec aegirinec-augite, nepheline, cancrinite, sodalite and chlorite and chemically by an agpaitic index' of about 1 2 K-rich trachyte exhibits porphytitic texture, and is chemically characterized by low NaO(0 45 wt %), high K₂O(13 25 wt %) resulting to high K ₄O/Na₂O ratio of nearly 3.

This occurrence of alkaline and related rocks together With the earlier reported occurence of an alkaline-carbonatite complex from the nearby Wah Sung valley, Meghalaya points to an alkaline phase of magmatic activity in this part of the Indian subcontinent.

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C. Gundu Rao ¹, Dwijendra K. Sharma ¹, Sunil Kumar ¹

Affiliations
1 Department of Geology, D. S. College, Aligarh 202001, IN

Abstract

The pink Quartzarenite Unit 3 (Q₃) of Larji Window Section (Lesser Himalaya), Kulu District, Himachal Pradesh, India, shows a lower thickness of continuous, undisturbed, uniform, horizontal laminations followed by a zone of flat stratification and this in turn by cross-bedded layers. Horizontal stratification is referred to as due to high flow regime conditions and the cross stratification to moderately shallow upper part of low flow regime conditions. Flat stratification (crenulated or wavy laminations of low amplitudes and broad wave lengths) are commonly observed in flume experiments as a function of low flow regime in shallow water formed by the migration of very small ripples or very shallow sand waves but rarely reported from the stratigraphic record. The only known two instances are from Bull Run Formation (Triassic) of Northern Virginia and Duncannon Formation (Devonian) of south-central Pennsylvania. In this connection, reporting the occurrence of flat stratification from such an ancient quartzarenite unit (Lower Upper Proterozoic) as of Larji Window may be of considerable interest from the point of view of Dynamic Stratigraphy.

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Sunil Kumar ¹

Affiliations
1 Atomic Minerals Division, Dept. of Atomic Energy, Nagarbhavi, Bangalore 560072, IN

Abstract

The pink granite of Songsak area, East Garo Hills district, Meghalaya, intrusive into Precambrian gneisses is inferred to be S-type, peraluminous, low calcium, postkinematic granite. It is characterised by initial ⁸⁷Sr/⁸⁶Sr ratio of 0.728±.002, high K₂0, high differentiation index and presence of normative corundum. The major mineral constituents are perthitic microcline, fresh interstitial microcline, orthoclase with different degree of triclinisation, two generations of quartz and biotite. Sericitization of feldspars, presence of muscovite, rare chiastolite, fluorite and uraninite are other characteristics of the pink granites. Whole rock Rb-Sr dating assigns an age of 500±40 m.y,

Keywords

Geochemistry, Geochronology, Granite, Meghalaya, East Garo Hills.

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B. C. Prabhakar ¹, S. B. K. Soman ¹, Sunil Kumar ², R. Radhamani ², R. Rangaswamy ²

Affiliations
1 Department of Geology, Gulbarga University, Sandur- 583 119, IN
2 Atomic Minerals Division (DAE), Nagambhavi, Bangalore-560 072, IN

Abstract

No Abstract.

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Sukantadey ¹, R. Gajapathi Rao ¹, R. A. Gorikhan ¹, D. Veerabhaskar ¹, Sunil Kumar ¹, Mary K. Kumar ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Bangalore - 560 072, IN

Abstract

The late Archaean Closepet Granite of the Gudur-Guledagudda area consists of equigranular pink and grey biotite granites, and porphyntic pink biotite granodionte to quartz-monzodionte. The granitoids exhibit intrusive relation with the Hungund-Kushtagi schist belt at places. The equigranular granites show limited range of major oxide compositions and compared to the porphyntic granodionte and quartz-monzodionte, are enriched in Si0₂, K₂0 and Rb but depleted in Al₂0₃, FeO, Fe₂0₃, CaO, MgO, P₂0₅, Sr, Ba, Y, Nb and REE. The granitoids fall near the boundary between peraluminous and metaluminous granitoids with the A/CNK ratios around one Fractionated LREE and flat HREE patterns and a negative Eu anomaly characterize all the samples Field evidences indicate mainly post-kinematic nature of the granitoids. The equigranular granites appear to be minimum melt derived from anatexis of Peninsular Gneiss without fractional crystallization. The porphyntic granodionte and quartz-monzodionte represent non-minimum melt derived from a different source enriched in REE Geochemical signatures indicate that the Closepet Granite of Gudur-Guledagudda area is the product of melting at shallower level compared to the southern Closepet Granite.

Keywords

Petrography, Geochemistry, Northern Closepet Granite, Gudur-Guledagudda Area, Karnataka.

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Sukanta Dey ¹, R. Gajapathi Rao ¹, Sunil Kumar ¹, D. Veerabhaskar ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Nagarabhavi, Bangalore - 560 072, IN

Abstract

The Neoproterozoic Badami Group of the Kaladgi-Badami basin consists of an undisturbed sequence of sandstone, shale and limestone exposed in the northern districts of Karnataka and adjoining parts of Maharashtra (Viswanathiah, 1977; Jayaprakash et al. 1987). The sequence unconformably overlies Archaean granitoids, schists and the Mesoproterozoic Bagalkot Group of sediments. The environment of deposition of the Badami Group has been interpreted as shallow marine (Sathyanarayan, 1994). This note presents some field evidences around Khanapur village, Bagalkot district revealing the nature of palaeo-coas tal morphology during the deposition of Cave Temple arenite (CTa), the main sandstone member of the Badami Group.

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