Analytical Results of the Interpretation of Aero-Magnetic Data of the Kanker-Dhamtari area,Chhattisgarh Basin, Bastar Craton,Central India

摘要

The analyses and the interpretation results of multi-sensor aero-geophysical data of the Kanker-Dhamtari area of the, Chhattisgarh basin,Bastar Craton are presented. Multi-sensor airborne geophysical data was acquired by the Geological Survey of India, employing magnetic and spectrometric sensors, in parts of Kanker, Durg, Bastar, Raipur and Rajnandgaon districts of Chhattisgarh and the Koraput district of Orissa. The objective of this work was to understand the sub-surface geology and its, structural aspects and to identify potential areas for mineralisation. The area falls in the southern part of the Chhattisgarh basin, within the Precambrian Bastar Craton. The study area exposes rocks of the Archaean Bengpal, Bailadila and Dongargarh Groups in the southern part that are overlain in the north and south by the rocks of the Neoproterozoic Chhattisgarh Supergroup. The Bengpal Group of rocks, comprising upper amphibolite facies, BIF, meta-pelite and amphibolites, occur as small mappable units within migmatite and granite gneiss. Prominent E-W sub-surface magnetic features, with en-echelon shifts, not reflected in the geological map and with sub-horizontal dips as reflected from 2D modelling, are inferred to represent shears. The radially averaged power spectrum of the magnetic data brought out three magnetic interfaces at depths of 964 m, 1,156m and 19,170 m below the observation plane which was 950 m above MSL (150 m for ground clearance) and matched layer filter maps reflect the anomaly pattern at different depths obtained from the power spectrum which helped in understanding the sub-surface lithology. Besides, 3D-modelling of the anomalies falling close to the intersection of different anomaly trends and thought to be potential for mineralisation, identified from a reduced-topole (RTP) map, was carried out to obtain parameters like, depth to the top of body, depth to the bottom of the body and susceptibility contrast with respect to the host rock. 3D modelling revealed that some of the causative sources emplaced in the second layer are found to be extending to the third layer with depths ranging up to 7 km. The quantitative interpretation of the magnetic data using these different methods yielded good correlation and facilitated understanding of the nature of various causative sources. The Euler-3D de-convolution method, adopting constraints judiciously, helped in obtaining the depth estimates which are in good agreement with 2D and 3D modelling results.