Magnetic field modelling and interpretation of the Himalayan–Tibetan Plateau and adjoining north Indian Plains

Abstract

A prominent magnetic low is seen over the Himalayan–Tibetan plateau and the northern Indian shield region in satellite anomaly data. Here we model the sources for the observed magnetic low in the region. The induced magnetic field is modelled based on a crustal magnetisation model computed in a Geographical Information System, with horizontal layers containing susceptibility derived from the geology and a tectonic map of the region and global seismic crustal thickness model. The modelling results indicate that the upper crust of the Himalayan–Tibetan plateau is magnetised while much of the middle crust and the lower crust appears non-magnetic. Thermal modelling corroborates the predictions, placing the Curie isotherm in the southern Tibetan Plateau no deeper than 10 km. The results suggest that the sources of the magnetic low observed in the region are likely to be a thin magnetised crust, because of the elevated Curie isotherm in this region. The Indian shield region is believed to extend up to the foothills of the Himalayas in the north, but most of the shield is obscured by a thick sediment cover of the Gangetic Plains to the north. The magnetic field modelling suggests a weakly magnetic crust in the region indicating either the Indian shield may not extend up to the base of the Himalayas or the lower crust in the region has been modified.