Favourable IOCG and polymetallic environs in Marwar - Khetri, NW Indian Shield imprints from aerogeophysical data analysis

Abstract

The analysis of aeromagnetic data reveals two significant broad oval-shaped aeromagnetic anomalies oriented in the NE-SW direction, west of Laxmangarh and east of Fatehpur. These significant anomalies identified beneath sand-alluvium-covered areas of Rajasthan's Marwar region are of a low dominance nature. These magnetic signatures are associated with gravity gradients in the regional Bouguer gravity map. Magnetic anomalies and subsurface modeling revealed that the remanence source had a high magnetic susceptibility. The ground gravity profiles across the Laxmangarh anomaly show a high gravity variation of 5 mGal/km. The integration of geochemical distribution patterns, spectrometric elemental concentrations, different ratios, and composite image maps has brought out alteration/shear zones that are favourable for mineralization. The results of selective 2D-profiles, plate modeling, and 3D-inversion modeling of these anomalies reveal that the depth of the causative source varies from 300 to 1000 m. The higher-order magnetic susceptibilities, geochemical dispersion pattern, and spectrometric ratio maps and composite images distinguished hydrothermal alteration zones characterised by potassium enrichment. The results indicate the possibility of concealed source rocks with high magnetic mineral content (magnetite, maghemite, titanomaghemite, pyrrhotite, and franklinite?) and a relatively high density. The geophysical signatures observed around Fatehpur and Laxmangarh, with high magnetic contrast, low dominance, and remanence coupled with high gravity values, as well as hydrothermal alteration zones, appear to have striking similarities with the geophysical and geochemical scenarios of some of Australia's Iron Oxide Copper-Gold (IOCG) prospects in the Gawler, Arunta, Tennant, and Mount Isa regions. Therefore, these anomalous areas may be explored for the possibilities of an IOCG or polymetallic type of mineral.