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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D. K. Sinha ¹, D. V. Subba Rao ²

Affiliations
1 Scientific Officer/G, AMD, Plot No 188, Laxmi Nagar, Niwaru Road, Jhothwara, Jaipur - 302 012, IN
2 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

No Abstract.

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D. K. Sinha ¹, A. Rai Choudhuri ², D. B. Guha ²

Affiliations
1 Plot no. 188, Laxmi Nagar, Niwaru Road, Jhothwara, Jaipur - 302 012, IN
2 Geological Survey of India, Salt Lake city, Kolkata - 700 091, IN

Abstract

No Abstract.

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D. K. Sinha ¹

Affiliations
1 Sarala Sadan, Laxmi Nagar, Jhothwara, Jaipur, IN

Abstract

No Abstract.

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D. K. Sinha ¹, Sohail Fahmi ¹, B. C. Sarkar ¹, M. K. Roy ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, 521207 Pratap Nagar, Tonk Road, Sanganer-Jaipur -303 609, IN

Abstract

Uraniferous polymetallic veins are found in the Gyangarh Asind acidic igneous suite and Sandmata Complex near Chhota-Udaipur in Rajasthan. These veins occur in continuation of the well-known U-Co-Mo mineralised albitite zone in Rajasthan and represent a potential target.

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D. K. Sinha ¹, K. A. Raju ², D. Veera Bhaskar ², K. Asha ³

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Jaipur - 302 018, IN
2 Atomic Minerals Directorate for Exploration and Research, Nagpur - 440 001, IN
3 Atomic Minerals Directorate for Exploration and Research, Hyderabad - 500 016, IN

Abstract

Rocks of Singhora Group, Chhattisgarh Supergroup, deposited in a protobasin, contain pyrite and galena near Juba and Banjhapalli villages of Raipur District, Madhya Pradesh. Veins of fluorite, quartz and quartz-feldspathic material reported along the eastern and western margins of the protobasin contain galena and pyrite in the sedimentary rocks. Pyrites are developed diagenetically, epigenetically and by remobilization in Rehatikhol Formation of Singhora Group, while only epigenetic pyrite occurs in the basement. High positive δ³⁴S values (+3 1.58‰ δ³⁴S samples) for diagenetic pyrite indicate reaction between iron-bearing minerals and H₂S and/or HS^- generated by reduction of seawater sulphate. High δ³⁴S value (+23.35‰) for galena is due to reaction between diagenetic pyrite and base metal-bearing fluids at elevated temperatures. The galena-pyrite pair developed epigenetically shows 135°C temperature for their formation at near equilibrium conditions. Galena grains collected from quartzo-feldspathic/quartz veins from the eastern margin of Singhora protobasin near Chiwarkuta village yielded δ³⁴S value of +11.1‰, while pyrite from quartz veins of Birsinghpali-Kapudih tract of western margin has givenδ³⁴S value of +3.3‰. These values suggest an igneous source for the fluids, probably from a magma that assimilated sulphur from the country rocks. High δ³⁴S value (+27‰) of pyrite in black shale of Saraipalli Formation explains its deposition below mud-water interface. Quartz arenite of Bhalucona Formation overlying the Saraipalli shales contains pyrite concretions having a δ³⁴S value of +23.7‰. δ³⁴S value (+3.4‰) of pyrites from migmatite and quartz veins intruding the crystallines of eastern margin i.e. Sambalpur Granitoid that forms the basement to Chhattisgarh Supergroup, also shows magmatic source of sulphur that could have been generated from the upper mantle or homogenized crust.

Keywords

Sulphur Isotopes, Pyrite, Galena, Chhattisgarh Basin.

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