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B. Banerjee , Aparajita Nandi , S. Nath , S. K. Banerjee

Abstract

Soil of quality class I Eucalyptus tereticornis in South Bengal have been studied for their morphological characteristics and physicochemical attributes. The soils are acidic and poor in organic matter. The sudace soils are light but clay translocation is common in most of the profiles. The chemical composition of the soils has been influenced to a great extent by drainage condition, differential transport of eroded material, leaching, translocation, redeposition of mobile soil constituents and formation and abundance of mottles. Chemical composition also indicates trends of laterisation of organic matter and break-down of parent material into free silica and sesquioxides.

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Dinesh Gupta ¹, Radhe Shyam ¹, A. K. Agarwal ¹, B. B Bhattacharya ², B. Banerjee ³

Affiliations
1 Geological Survey of India, 15-16 Jhalana Doongri, Jaipur-302004, IN
2 Indian School of Mines, Dhanbad-826004, IN
3 Marine Wing, Geological Survey of India, Calcutta -700016, IN

Abstract

In surface geophysical surveys, resistivity contrast between the ore and host rock plays a vital role in the success ratio of the surveys. To overcome the problem of insufficient resistivity contrast, a modified method, Mise-a-la-masse, as tried and found to be very effective in tracing the extensions of polymetallic sulphides intersected in a borehole. The method was applied to Pb-Zn and sulphide hosted gold prospects in Rajasthan and the results obtained indicate that Mise-a-la-masse method can be successfully employed for delineating subsurface extension of polymetallic sulphide deposits.

Keywords

Exploration Geophysics, Electrical Resistivity Contrast, Polymetallic Sulphides, Rajasthan.

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L. K. Das ¹, D. C. Mishra ², D. Ghosh ¹, B. Banerjee ¹

Affiliations
1 Central Geophysics Division, Geological Survey of India; P-49; C II Road, Beliaghata, Calcutta-700 016, IN
2 National Geophysical Research Institute, Hyderabad-500 007, AP, IN

Abstract

Ground magnetic survey of part of central India covering the Vindhyan Basin of the upper Son valley region has delineated some subsurface vsolcanogenic Proterozoic rifts below the Vindhyan cover and several faults which have controlled the tectonics of the region. The magnetic map in general shows four distinctly different domains with magnetic anomalies differing both in amplitude and their nature. In general, the Vindhyan basin is characterized by low amplitude broad anomalies while the Mahakoshal (lower Proterozoic) Group depicts large amplitude sharp anomalies due to the presence of high susceptibility (2-19 × 10^-3 CGS units) ferruginous rocks in them. The domain boundaries are either faults or indicate formational contacts between the different types of rocks with contrasting susceptibility values.

The subsurface basement relief map of the Pre-Vindhyan topography determined by 2-dimensional Harmonic Inversion of the magnetic data reveals an asymmetric graben structure with the southern boundary fault between the Vindhyans and the Mahakoshals as the most prominent linear structure.

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