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

A. K. Talapatra ¹

Affiliations
1 Department of Geology, Presidency College, Calcutta, IN

Abstract

Detailed petrographic study of the rocks of the Mosaboni copper mine, Singhbhum district, Bihar, suggests that quantitative petrographic data may be successfully utilised here for locating the lode zones in the lower levels where exploration is going on. In this study the mineralogical compositional variation was drawn in the form of 'isopleth map' prepared with the modal percentage of important mineralogical constituents of all the samples collected from two vertical sections of the Mosaboni mine. The isopleth maps suggest that within the portion of the mine already worked, the mineralogical compositional variation of the country rocks shows close relationship with the lode zone. From the trend of mineralogical variation, it might be possible to extrapolate the position of the lode zone from any mine level to the nearby areas in the same level and at depths. Thus the petrographic data may guide the explorer in the right direction in such a mine.

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A. K. Banerji ¹, A. K. Talapatra ², A. V. Sankaran ³, T. K. Bhattacharyya ³

Affiliations
1 Geology Department, Presidency College, Calcutta, IN
2 Geological Survey of India, Patna, IN
3 Petrology Laboratory, Atomic Minerals Division, New Delhi, IN

Abstract

Study of the trends of geochemical migration of some major and minor elements during progressive migmatisation within part of the Singhbhum shear zone supports the view that apatite-magnetite, uraninite and copper sulphide deposits and the associated wall rock alterations are related to processes of migmatisation therein. During migmatisation extensive mobilisation of elements took place when Si, Al, Na and small quantities of Ga, U and Zr were introduced into the pre-existing basic metavolcanics within the shear zone, and Fe, Mg, Ca, K, Ti, Mn, P, Ba, Rb, Sr, Li, Ni, Co, Cr, V, Cu, and Y were expelled from these rocks. The addition of the former group of elements brought about transformation of these rocks, into felspathic schists and gneisses (the soda-granites) while the expulsion of the latter group of elements from these rocks and their addition to the migmatising fluids caused progressive changes in the chemical composition of these fluids. At the closing stages of the process these fluids were transformed into mineralising solutions that gave rise to apatite-magnetite, uraninite and copper sulphide deposits and to extensive sericitisation, chloritisation, biotitisation and silicification within the shear zone. The various elements, present in traces, entered the crystal lattices of these minerals, in accordance with their geochemical preferences and in proportion to their concentration in the mineralising solutions. The resulting deposits should be regarded as 'metasomatic hydrothermal'.

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A. K. Talapatra

Abstract

No Abstract.

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D. D. Sarma ¹, A. Ghosal ², A. K. Talapatra ³, J. V. Subbaraman ⁴

Affiliations
1 2-1 6- 104, Prashanthinagar, Uppal, Hyderabad - 500 039, IN
2 Pitampura, New Delhi, IN
3 Geology Department, Presidency College, Kolkata - 700 073, IN
4 # 1126, Geetha Road, Robertsonpet K.G.F - 563 122, IN

Abstract

No Abstract.

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