Heliborne magnetic, radiometric and time domain electromagnetic signatures of Aravalli Supergroup of rocks, Rajasthan as an aid in deciphering surface and subsurface geological information

High resolution heliborne magnetic, time domain electromagnetic and gamma-ray spectrometric data acquired over a part of Paleo-Proterozoic Aravalli Fold Belt (AFB) have brought out the surface and subsurface geological attributes owing to physical property contrast. Complexly deformed meta-volcano-sedimentary sequence of Paleo-Proterozoic arcuate lower and middle sequence of Aravalli Supergroup unconformably overlying Archean basement of Bhilwara Supergroup extends from Nathdwara in the north to Banswara in south. Concealed extension of basic volcanics of Debari Group below the overlying metasediments is identified based on the longer wavelength, higher amplitude and trend of magnetic anomalies. The younger basic plugs/ dykes transecting the basinal sequence and faults varying from NW to NE trend have been picked up from magnetic signatures. The nature of radioelement distribution obtained from gamma-ray spectrometric data clearly differentiate the Archean basement and its inliers in Sarara-Mando ki Pal sector, basinal sediments of Debari Group, Udaipur Group and intrusive granites. Occurrence of another inlier at Metwala is revealed through radiometric signature. Conductive carbonaceous phyllite of Debari Group reflected in time domain electromagnetic data prominently reflects the folded structure in southeastern part near Parsola-Banswara tract thereby aiding to delineate axial trend and map the fold pattern. Conductive signature and subsequent ground validation revealed occurrence of carbonaceous partings in some parts of dolomite of Debari Group. Interpretation of heliborne geophysical data has enhanced geological knowledge of the Aravalli Supergroup. (author)