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

L. N. Singh ¹, T. Lal ², A. K. Agrawal ³, S. L. Singh ⁴, Narendra Singh ¹

Affiliations
1 Geological Survey of India, Northern Region, Lucknow - 226 020, IN
2 Department of Geophysics, Banaras Hindu University, Varanasi - 221 005, IN
3 Geological Survey of India AMSE Wing, Bangalore - 560 078, IN
4 Geological Survey of India Western Region, Jaipur - 302 004, IN

Abstract

Lead-zinc mineralisation in Sawar metasedimentary belt is essentially sediment-hosted type it is of Proterozoic age and occurs in the two-carbonate members of Sawar group lnduced Polansation cum resistivity survey has delineated 22 anomaly zones located in lower marble, lower schist and upper marble and at the mutual contacts formed by these different litho-units of Sawar group Out of these, eight zones have been drill tested proving mineralisation and the remaining 14 zones in the area are yet to be tested Drilllng results in the area have clearly indicated that there is a fair correlation between induced polarisation cum resistivity anomalies and mineralised zones intersected in the different boreholes.

Induced Polarisation cum resistivity pseudo depth sections constructed in few zones located over different rock units have established depth persistence of inferred shallow conductors The resistivity survey has demarcated the contact of different litho-units of Sawar group occuring in the area even under soil cover The lithocontacts inferred from resistivity data coincide fairly accurate with extrapolated geological contacts The Interpretation of induced polarisation and resistivity pseudo sechons by inversion technique has brought the model and its geometry, whch compares well wlth the subsurface geology The resistivity model correlates the measured and calculated apparent resistivity pseudo sections The chargeability model also corroborates these inferences.

Keywords

IP Survey, Pb-Zn mineralised zones, Qualitative and quantiiative interpretation, Sawar metasedimentary belt, Ajmer district, Rajasthan.

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C. L. Singh ¹, T. Lal ¹, A. Kumar ¹, S. K. Prajapati ²

Affiliations
1 Department of Geophysics, Banaras Hindu University, Varanasi - 221 005, IN
2 National Geophysical Research Institute, Hyderabad - 560 007, IN

Abstract

Gravity survey was conducted in an area of about 13000 sq km covering northeastern part of Chhattisgarh Basin, Bilaspur-Raigarh gneissic belt and the central part of Mahanadi graben. Analysis of gravity anomalies has helped in the demarcation of the boundary of Chhattisgarh Basin and Mahanadi graben as well as in the determination of extent of basins and associated structures. The thickness of sediments in Chhattisgarh Basin and Mahanadi graben is estimated to be 3 5 km and 2 5 km respectively above the crystalline basement. Two prominent gravity high closures in the vicinity of Bilaspur and Akaltra are new findings and are attributed to presence of high density metamorphic schist belt below the Chhattisgarh Basin.

Keywords

Gravity Method, Graben, Schist, Gneissic Belt, Chhattisgarh Basin.

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