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Thursday, March 16 • 4:00pm - 5:30pm
Poster: Lithospheric Foundering and Underthrusting beneath Tibet revealed by Adjoint Tomography

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New adjoint tomographic images unveil a large-scale, high wave speed structure beneath South-Central Tibet in the middle to lower portions of the upper mantle. We interpret this structure as a remnant of an earlier lithospheric foundering event. Spatial correlations between foundering lithosphere and ultrapotassic and adakitic magmatism support the hypothesis of convective removal of thickened Tibetan lithosphere causing a major rise of Southern Tibet during the Oligocene. Lithospheric foundering induces an asthenospheric drag force, which drives continued underthrusting of the Indian continental lithosphere and associated shortening of the remaining Tibetan lithosphere. We speculate that more recent asthenospheric upwelling leads to a thermal modification of thickened lithosphere beneath Northern Tibet and subsequent surface uplift, consistent with the correlation of recent potassic volcanism and an imaged narrow low wave speed zone in the uppermost mantle. In contrast, the unusually high seismic wave speeds in the uppermost mantle beneath Southern Tibet, reminiscent of images beneath the North American craton, suggest a possible prototype of modern craton formation due to continued under-accretion of Indian continent.

Thursday March 16, 2017 4:00pm - 5:30pm
Exhibit Hall BRC