An analysis of crustal magnetic anomaly and Curie surface in west Himalayan syntaxis and adjacent area

Abstract

In this paper, the magnetic model NGDC-720-V3 is used to investigate the distribution of crustal magnetic anomaly and the depth of Curie surface in west Himalayan syntaxis and its adjacent area. The Curie surface is compared with regional heat flow, the Moho, and seismicity. The results show that the magnetic anomaly and Curie surface are both consistent with the regional tectonic setting. Tarim craton, Tadjik Basin, and Indian Plate have positive magnetic anomaly and a Curie surface deeper than 36 km, corresponding to low heat flow there. In contrast, orogenic belts such as west Himalayan syntaxis, Tianshan Mountain, Afghanistan, and Tibetan Plateau have negative anomaly and a Curie surface shallower than 32 km, corresponding to high heat flow. The north of the syntaxis presents a positive anomaly on the surface, resulting from Ferghana Basin, while the negative anomaly in large depth is probably associated with the subduction of the slab and the resulting heat. The depth of the Curie surface has an inverse relationship to the Moho depth, which is attributed to temperature and isostatic balance. The distribution of earthquakes with epicenter deeper than 100 km clearly suggests the subduction of the Indian plate deep down to the asthenosphere and the deep earthquakes were caused by shear motion within the subducting slab.