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

D. K. Sinha ¹, Sohail Fahmi ¹, A. K. Bhatt ¹, Govind Singh ¹, Rajendra Singh ²

Affiliations
1 Department of Atomic Energy, C-31, Devnagar, Tonk Road, Jaipur-302018, IN
2 Department of Atomic Energy, AMD Complex, Begumpet, Hyderabad-560016, IN

Abstract

Albitite and albitised banded gneissic country rock from the Ladera-Sakhun area, situated about 80km southwest of Jaipur, show several evidences for soda metasomatism. Megascopic evidences include reddening of outcrops due to aventurisation, gradational contacts between albitite and gneisses, development of metasomatic minerals, dequartzification, epidotization and cataclasitisation. Microscopic evidences include relict microcline in the newly formed albite grain, poor and discontinuous development of twin lamellae in albite giving step-like appearance, ubiquitous sweeping extinction in albite due to cataclasitisation, occasional mortar texture in albitite, tapering of twin lamellae within the grain, twin lamellae forming in chequered fashion, development of aventurine albite containing dusty Fe-oxide inclusions, development of albite along twin/cfeavage plane of microcline, formation of new albite in plagioclase, destruction of sericite in plagioclase of albitised granite, formation of myrmekite of intergranular, intragranular and rim types, development of epidote corona around clinopyroxene in pyroxenite, partial to complete dequartzification and filling up of voids by calcite. Petrochemical evidences of increased characteristic values of Na₂O from 3.17 to 7.00 wt%, K₂O and Si₂O from -0.03 to -6.00 wt% and -0.76 to -10.55 wt% in the unalbitised to albitised rocks respectively, provide further support for soda metasomatism. Albitisation at Ladera-Sakhun area extends over a considerable distance into Haryana in the NE and beyond Tal in the SW, attesting to its regional significance and its potential for mineralisation.

Keywords

Petrology, Metasomatism, Albitite, Ladera-Sakhun, Rajasthan.

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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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G. R. Narayan Das ¹, D. K. Sharma ¹, Govind Singh ¹, Rajendra Singh ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, New Delhi-110022, IN

Abstract

Uranium mineralisation of segregated type consisting mostly of uraninite and less commonly of brannerite has been noted in the pink quartzo-feldspathic or aplitic emplacements along shear zones in Rohil-Ghateshwar-Khandela-Diara and Saladipura area in Sikar district of Rajasthan. Ilmenite, molybdenite, pyrrhotite, chalcopyrite and pyrite are noted along with uraninite.

Mineralisation is controlled by structure and generally occurs along linear shears that are parallel to the main tectonic lineament. In Ghateshwar area, the mineralised quartzo-feldspathic emplacements have undergone refolding along with the rest of the formations. Uranium mineralisation is near to the main tectonic lineament that passes through the axis of the Ajabgarh synclinorium. Integrated radiometric and hydrogeochemical surveys have indicated continuity of the uranium bearing quartzo-feldspatbic emplacements along a 16 km belt.

The Salwari fluorite occurrence 10 km NE of Khandela is a post feldspathic emplacement and probably formed during the final phases of mineralisation.

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Rajendra Singh ¹, R. Dhana Raju ², A. K. Singh ³

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500 016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560 072, IN
3 Atomic Minerals Division, Department of Atomic Energy, Calcutta-700 026, IN

Abstract

A zirconium-rare earth (RE)-thorium-uranium fossil placer with about 60-84% heavy and resistant minerals is recorded in association with quartzite and metagreywacke of the Proterozoic Miri Group from the Boleng area in East Siang District of Arunachal Pradesh. The heavy minerals occur as thin layers with variable thickness of a fraction of a cm to a maximum of 12 cm. The mineralised rocks are hard, highly compact, very heavy (sp. gr. 3.96-4.66), massive (at places, banded) and exhbit clastic texture with rounded to subrounded and well sorted fine grains of heavy minerals pointing to a long distance of transportation. Mineralogically, it consists of 46-61% opaques (mostly Ti-hematite), 9-13% rutile, 3-9% cyrtolite, 0.7-4.5% monazite and 0.2-0.9% thorite, all set in 10-30% sericitic matrix. Chemically, it is markedly different from the widespread unconsolidated coastal and inland placers, and analyses about 43-62% iron oxides, 1.7-5.4% Zr0₂, 0.5-3.1 % (RE,Y)₂O₃, 0.1-0.5% ThO₂, and 0.01-0.9% U₃O₈. Chondrite-normalizcd REE-pattems show light REE enrichment and heavy REE depletion, with (Ce/Yb)_cn ratio of 9-10 and markedly negative Eu-anomaly (Eu/Eu: 0.18-0.22). Generally, consolidated placers (fossil placers) are monazite-rich, whereas unconsolidated placers are, zircon-rich and viewed in this light, the cyrtolite (zircon)-rich fossil placer from the Boleng area is a rare occurrence.

Keywords

Fossil Placer, Radioactivity, Boleng, Arunachal Pradesh.

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Navin Goyal ¹, Siby K. Varughese ¹, P. K. Hansda ¹, S. Ramachandran ¹, Rajendra Singh ²

Affiliations
1 Atomic Minerals Division, Baroda - 390 001, IN
2 Atomic Minerals Division, Hyderabad - 500 016, IN

Abstract

The Precambrian Champaner Group of rocks are intruded by Godhra granites in Jambughoda area. Significant uranium mineralisation has been located in the fractures in the dolomitic limestone of Lower Champaners with uraninite occurring as the primary uranium mineral. The geochemical features observed for the granites suggest that the granite melt, originated by the partial melting of relatively silicic crust, was further modified by fractionation processes during which uranium was concentrated in the late magmatic and subsequent hydrothermal fluids. The Champaner deformation resulted in the formation of WNW-ESE regional fracture system and crush zones, thus making the rocks highly penneable for the passage of uranium-rich hydrothermal fluids and offering open spaces for precipitation of uranium under suitable physicochemical conditions.

Keywords

Geochemistry, Champaners, Granites, Uranium, Gujarat.

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P. B. Maithani ¹, Y. V. Rathaiah ¹, Siby K. Varughese ¹, Rajendra Singh ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Baroda-390 001, IN
2 Hyderabad-500016, IN

Abstract

The granites around Zoz represent a differentiated, calc-alkaline, subaluminous, A-type granite with higher uranium content. The A-type affinity points to the possibility of encountering Sn, Mo, Bi, Nb, Ta and F mineralisation in the area. The low Th/U ratio also favours vein type U-deposits within granites or in adjacent metasediments.

Keywords

Geochemistry, Godhra Granite, Zoz, Champaner, Gujarat.

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