Receiver Function Imaging of the Mantle Transition Zone beneath SE Tibet: Evidence for Burmese Microplate Eastward Deep Subduction

Abstract:

Burma microplate subducted eastward beneath SE Tibet since Mesozoic, and the origin of the Tengchong volcanism is related to the subduction. However, do the subduction and the volcanism affect the structure of the mantle transition zone (MTZ)? These issues are still unclear. Here, we used 398 seismic stations from ChinArray program and IRIS DMC, and then calculated 13928 P-wave receiver functions with iterative deconvolution method to detect the structure of the MTZ and its lateral variations. The topography of the 410 and the 660 km discontinuities is closely related to the subduction and the volcanism, which revealed by seismic tomography. Combining previous researches, we improved the model of upper mantle structure under the Indian plate, Burmese Arc and SE Tibet. We suggest that the subduction of the Burmese slab extend down across the 410 km discontinuity and then stagnates in the MTZ. The stagnant slab in the MTZ may penetrate into the lower mantle. Beneath the Tengchong volcano, the hot material upwelling from the dehydration of the subducted slab originates in the MTZ, which affect the topography of the 410 km discontinuity.