Curie depth and apparent magnetic susceptibility contrast mapping from aeromagnetic data in parts of Dharwar Greenstone Belt and Singhbhum Craton and Mobile Belt, India

Curie depth and apparent magnetic susceptibility contrast (AMSC) have been mapped from aeromagnetic data for parts of Dharwar Greenstone Belt (DGB), and Singhbhum Craton and Mobile Belt (SCM), India. The Curie depth has been estimated using harmonic inversion of the total field aeromagnetic anomaly. Curie depth maps, thus obtained, show broad Curie depth variations, in the range of 51-63 km for DGB, and from 19 to 28 km for SCM. The mapped Curie crust shows a gradual increase from north to south in both areas under study. Based on a linear relation between the surface heat flow density and the Curie depths, Curie depths have also been estimated by using surface heat flow density information from the area. Curie depths, thus estimated, are found to be of the order of 22.5 km, 35 km and 67 km for Singhbhum mobile belt, Singhbhum craton, and DGB respectively, corresponding to their surface heat flow densities of 60 mWm-2, 39 mWm-2 and 20 mWm-2. AMSC mapping has been carried out using a stochastic inversion algorithm. In order to estimate AMSC, average crustal thicknesses (based on Curie depth variations) were taken as 57 km for DGB and 23 km for SCM. AMSC contour values (maps), thus derived, depict broad apparent magnetic susceptibility contrast variations for DGB ( 0 to 10x10-3 SI) and for SCM (-32x10-3 to 16x10-3 SI), that are progressively on the increase from southeast to northeast, reflecting the overall subsurface magnetic characteristics of the areas under study.