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

M. M. Mukherjee ¹, W. K. Natarajan ¹, K. Shashidharan ¹

Affiliations
1 Geological Survey of India, Southern Region, Bangalore 560011, IN

Abstract

Several parallel to sub-parallel auriferous mineralised zones of economic significance occur over a strike length of 3 km and spread over a width of about 1 km in 'Chigargunta area of South Kolar schist belt. The host rocks for mineralisation are metamorphosed basalt and acid tuff ('Champion gneiss'). The mineralised zones represent ductile shear zones transecting the regional north-south trending schistosity (S₂) at low angle. The pre-existing planar and linear fabrics of the rocks have been rotated into parallelism with the shear zone. The shear zones display mylonitic foliation with prominent downdip lineation, folds of variable orientation, boudinaging and crenulations. Such deformation features are confined only to these strongly tectonised zones believed to have evolved by simple shear deformation. A progressive grain size reduction accompanied by hydrothermal retrogressive metamorphism of the amphibolite facies host rocks culminates laterally into the centre of the mineralised zones with lower grade greenschist assemblage. Nondilatant pegmatite veins and some high temperature alteration minerals indicate possible strain heating. The auriferous lodes occurring in Kolar Gold Field might have a simiiar tectonic evolution.

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D. S. Jeere ¹, K. Shashidharan ¹, A. Guha ¹, V. W. Khangan ¹

Affiliations
1 Geological Survey of India, Central Region, Seminary Hills, Nagpur - 440 006, IN

Abstract

The paper deals with the relationship between soil chemistry, surface & sub-surface water chemistry and geology of the Kuhi mineral belt, Nagpur district, Maharashtra. Water samples were collected from shallow aquifers and surface water and were analyzed for major ions and trace elements. The study was also made to assess the suitability of these waters for irrigation use. Topsoil samples were collected and analyzed for trace elements. Chemical analysis shows that majority of the groundwater of the area is calcium bicarbonate type. Statistical analysis determines high positive correlation values for cobalt and nickel in water as well as soil. The spatial distribution of Co, Ni, in soil and Co, Ni and Pb in groundwater are nearly similar. Water samples, 7 out of 46 were found un-suitable for irrigation use based on RSC, salinity hazard and Boron concentration parameters. The surface water samples of Nag River show decreasing concentration of major ions and trace elements along the flow. Based on field and laboratory observations it was found that the Nag River water is suitable for irrigation even though it contains high detergents with objectionable colour, taste and odour.

Keywords

Irrigation, Trace Elements, Mineralisation, Water Quality, Sakoli Fold Belt, Maharashtra.

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M. M. Mukherjee ¹, W. K. Natarajan ¹, K. Shashidharan ¹, Stephen George ¹

Affiliations
1 Geological Survey of India, IN

Abstract

Auriferous zones are confined to ductile shear zones in the mafic unit (metabasalt/metagabbro) as well as in the felsic unit ('Champion gneiss'). The occurrence of significant gold mineralisation in the' Champion gneiss' comprising quartzo-feldspathic schist is being reported for the first time.

Low grade (about 4 grammes per tonne) gold reserve of the order of 4.7 million tonnes under all categories (probable+possible) in the new prospect has been established.

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