[Withdrawn] Upper Mantle Anisotropy Study Beneath Abaga Area, Inner Mongolia, China

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

Central Asian Orogenic Belt (CAOB) is one of the largest Paleozoic orogens on Earth, which evolved from the latest Mesoproterozoic to the late Paleozoic, with the accretion of ophiolites, island arcs, accretionary wedges, oceanic islands and microcontinental fragments. Being the middle-eastern part of the CAOB, Inner Mongolia is characterized by widespread Cenozoic intraplate volcanisms and lithospheric deformation possibly related to the closure of the Paleo-Asian Ocean. However, the mechanism of lithosphere deformation is poorly understood. Seismic anisotropy determined by the splitting of shear waves, especially the core-refracted phases like SKS, is one of the most direct and effective ways to image the deformation in the interior of the Earth. A total of 120 pairs of shear wave splitting measurements and 113 null measurements are obtained at 32 portable seismic stations in Abaga area, Inner Mongolia. Delay times vary from 0.4 s to 1.4 s with an average value of 0.77±0.21 s; while fast directions trend from N101°W to N45°E. One group of fast directions in line with the strike of regional faults, trending N82.0°E±12.3°, is caused by lattice-preferred orientation of mantle crystals; the other group of fast directions observed in the North China Craton with an average value of N146.8°E± 9.5° are parallel to the direction of lithospheric deformation in Early Cretaceous, which may origin from fossil anisotropy remaining in the lithosphere. In addition, solely null measurements in the northern part of study area may suggest small-scale hot mantle upwellings which eroded the fossil anisotropy in lithosphere.

Presenting Author: Zhengyang Qiang

Authors