March 31 @ 12:00 pm - 12:50 pm CDT
Who: Dr. Min Chen & Hehe Jiang
When: Noon, Friday, March 31, 2017
Where: Room 100, KWGL
Chen: Lithospheric foundering and underthrusting imaged beneath Tibet
Long-standing debates exist over the timing and mechanism of uplift of Tibetan Plateau, and more specifically, over the connection between lithospheric evolution and the surface expressions of plateau uplift and volcanism. Our new tomographic model reveals a T-shaped high wave speed structure beneath South-Central Tibet, interpreted as remnant in the upper mantle from an earlier lithospheric foundering event. Its spatial correlation with ultrapotassic and adakitic magmatism supports the hypothesis of convective removal of thickened Tibetan lithosphere causing major uplift of Southern Tibet during the Oligocene. Lithospheric foundering induces an asthenospheric drag force, which drives continued underthrusting of the Indian continental lithosphere and shortening and thickening of the Northern Tibetan lithosphere. Surface uplift of Northern Tibet is subject to more recent asthenospheric upwelling and thermal erosion of thickened lithosphere, which is spatially consistent with the recent potassic volcanism and an imaged narrow low wave speed zone in the uppermost mantle.