Thermal Structure Beneath the Himalayan Orogen Revealed by Pn‐Wave Receiver Function Imaging

Abstract

The Himalayan orogen formed through convergence between the Indian and Eurasian plates, and parts of the subducting Indian crust were impeded by the Lhasa terrane and accreted into the orogen. However, whether the Indian lower crust was stripped from the downgoing plate and incorporated into the orogen, and by what mechanism, remain debated. We image crustal structures beneath the Himalayan orogen using Pn‐wave receiver functions derived from Hi‐CLIMB broadband seismic data. Our results reveal progressive northward thinning of the Indian crust, with the Main Himalayan Thrust reaching a depth of ∼50 km and it is overlain by a wedge‐shaped low‐velocity zone. These features are consistent with a hot Himalayan crust primarily heated by radiogenic heat production. We interpret the incorporation of deep Indian crust into the Himalayan crust as a thermally controlled, ductile transformation dominated near‐isothermal or heating exhumation process, with extrusion of rigid crustal wedges playing a subordinate role.