Mantle Driven Dynamic Uplift of Hangay Dome: New Seismological Constraints from Adjoint Tomography

Tuesday, 16 December 2014
Min Chen, Rice Univ-Earth Science, Houston, TX, United States, Fenglin Niu, Rice University, Houston, TX, United States, Qinya Liu, University of Toronto, Toronto, ON, Canada and Jeroen Tromp, Princeton University, Princeton, NJ, United States
The origin and nature of Hangay Dome, an unusual large-scale doming structure in Central Mongolia, remains enigmatic, partly due to lack of knowledge on its underlying seismic structure. Here we present a new high-resolution multi-parameter seismic model derived from adjoint tomography, utilizing the full wavefield recorded by an unprecedented seismographic network in its surroundings. The new seismological constraints include Vs perturbation, the Vp/Vs ratio and radial anisotropy, (Vsh-Vsv)/Vs. We observe clear correlation between the high topography of the dome and regions with a low Vs and high Vp/Vs ratio down to 150 km. We also observe negative radial anisotropy (faster Vsv) at deeper asthenospheric depths (250 - 500 km) underlying positive radial anisotropy (faster Vsh) at shallow depths (< 250 km) right below the dome, and negative radial anisotropy at shallower depths (50 - 150km) on the flanks of the dome. These observations are consistent with a scenario that a deep asthenospheric upwelling arises from the mantle transition zone, producing decompression melting that feeds magmatism causing high topography of the area.