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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Yamuna Singh ¹, K. D. P. Singh ¹, A. K. Bhatt ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Begumpet, Hyderabad- 500016, IN
2 J. L. N. Road, Jaipur-302004, IN

Abstract

X-ray powder diffraction data are presented for phurcalite [Ca₂(UO₂)₃ (PO₄)₂ (OH₄ 4H₂O], with orthorhombic symmetry, a very rare, yellow coloured, secondary uranium mineral, from Putholi (24°57'45":74"38'30"). The host rock is quartzite which contains fluorapatite, pyrite, goethite, hematite, magnetite, chlorite and mica as accessory minerals. Measured cell parameters of the phurcalite are: a₀ = 17.3416 Å,  b₀ = 16.1138 Å and c₀ = 13.5491 Å, with a cell volume of 3786.16 ų.

Keywords

Mineralogy, Phurcalite, Rajasthan.

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A. K. Dwivedi ¹, Joydip Sen ¹, C. Murugan ¹, G. Bairwa ¹, A. K. Bhatt ¹, P. V. Ramesh Babu ¹, S. A. Pandit ²

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Jamshedpur-831002, IN
2 Atomic Minerals Directorate for Exploration and Research, Hyderabad-500016, IN

Abstract

Hydrogeochemical exploration were earned out over an area of 700 sq km in Barabazar-Manbazar area of Purulia district, West Bengal, in order to identify target areas for the uranium mineralization. Water samples were collected from 504 borewells in the Singhbhum Group meta-Sediments and Chhotanagpur Granite Gneissic Complex (CGGC) including South Purulia Shear Zone (SPSZ). For individual Iithological domains, univariate and multivariate statistical techniques were applied to the analytical data on 10 variables, i.e. U, Na⁺, K⁺ , Mg⁺², Ca⁺², SO₄^-2, HCO₃, Cl^-, conductivity and pH. Five hydro uranium anomalous zones withm CGGC were delineated at Raghunathpur, Tentla, Chepua-Dighi, Ban and Jitujon areas. However, distinct pattern of high uranium values along with uranium/Conductivity are observed only in Raghunathpur-Tentla and Chepua-Dighi areas in the proximal tectonized zones of SPSZ. Based on the distinctive hydrogeochemical attributes, and favourable geology and structure, the areas in the vicinity of Raghunathpur-Tentla and Chepua-Dighi in the northern proximal contact of SPSZ, are designated as potential target areas for detailed geological and geophysical exploration.

Keywords

Hydrogeochemistry, Uranium, SPSZ, CGGC, Singhbhum Group, Purulia, West Bengal.

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Ajay K. Naithani ¹, A. K. Bhatt ², K. S. Krishna Murthy ³

Affiliations
1 National Institute of Rock Mechanics, Kolar Gold Fields - 563 117, IN
2 Water and Power Consultancy Services (I) Ltd., Gurgaon, IN
3 928, 22nd Main Road, IV T Block, Jayanagar, Bangalore - 560 041, IN

Abstract

The project area, forming a part of Bhagirathi valley, exposed rocks classed as central Himalayan crystallines and are medium to high grade metamorphics. The rock types exposed are feldspathic gneisses, quartz-biotite schists, garnet-biotite schist, biotite gneisses, migmatites and amphibolites. To design the rock support for the underground structures of desilting chambers, HRT, surge shaft, pressure shafts, power house, TRT and for the foundations of barrage and intake of desilting chambers, rock mass classifications was attempted following the methods of Bieniawski Rock Mass Rating (RMR) Classification and Tunnelling Quality Index (Q) of Barton et al. RMR technique involves collection of data on rock strength, RQD (%), spacing of discontinuities, condition of discontinuities and groundwater condition, while the 'Q' involves collection of data on RQD (%), joint set numbers (Jn), joint roughness number (Jr), joint alternation number (Ja), joint water reduction factor (Jw) and stress reduction factors (SRF). The permeability test in the overburden was done by the constant head method, while in the bed rock portion conducted by packer test. The result indicates that the rock masses of the area fall under the good, fair and poor rock quality. Augen gneiss of power house area is coming under the category of moderately strong rock as proved by deformability characteristics and strength parameter. On the basis of above study recommendations have been made for the proper and safe construction of the project components.

Keywords

Hydroelectric, Rock Mass Classification, Tunnel Quality Index, Garhwal Himalaya, Uttarakhand.

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A. K. Dwivedi ¹, U. K. Pandey ¹, C. Murugan ¹, A. K. Bhatt ², P. V. Ramesh Babu ¹, Mallikarjun Joshi ³

Affiliations
1 Atomic Minerals Directorate for Exploration and Research (AMD), Hyderabad - 500629, IN
2 Atomic Minerals Directorate for Exploration and Research (AMD), Jamshedpur - 831 002, IN
3 Banaras Hindu University, Varanasi - 221005, IN

Abstract

The Barabazar granite, exposed at the northern margin of Singhbhum craton, Eastern India, occurs along the South Purulia Shear Zone (SPSZ) and is emplaced into the Palaeoproterozoic metapelites and felsic volcanics of Singhbhum Group. Geochemical, petrographical and geochronological studies on the Barabazar granite addressed in the work have wide implications on understanding the geodynamics of SPSZ during Palaeoproterozoic to Mesoproterozoic. Geochemically, Barabazar granite displays limited range of major oxides, alkali enrichment and highly fractionated features (SiO₂ > 75%; Eu/Eu^* = 0.16-0.33; enrichment of K, Rb, Th, U and Nb; depletion of Ba, Sr, P and Ti). It is predominantly peraluminous (molar Al₂O₃/CaO+Na₂O+K₂O (A/CNK) = 1.14-144) and contains abundant alkali feldspar, perthite, and minor plagioclase, biotite and accessory minerals. Geochemical and petrological data indicates that it is A-type granite, which formed in 'Within plate granite' tectonic set up. The Barabazar granite was emplaced at ca. 1771 Ma (Pb-Pb) in rift related environs and evolved by partial melting of stabilized lower/middle crust (initial ⁸⁷Sr/⁸⁶Sr = 0.7302 ± 0.0066 and μ₁ = 8.5 ± 0.5). Subsequently, the shear zone (SPSZ) developed during the closure of the riftogenic basin and was reactivated during the Grenvillian orogeny (Ca. 900-1300 Ma), resulting in rehomogenisation of the strontium isotopes and thereby yielding younger whole-rock Rb-Sr isotope age of c. 971 Ma for the Barabazar granite. Probably during this tectonic event, the Singhbhum craton (Southern India Shield) would have finally juxtaposed with Northern Indian Shield along Central Indian Tectonic Zone (CITZ) during the global Grenvillian orogeny.

Keywords

A-Type Barabazar Granite, Geochemistry, Geochronology, Grenvillian Orogeny, Singbhhum Craton, SPSZ, West Bengal.

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