Mantle flow and olivine fabric transition in the Myanmar continental subduction zone

Abstract

One of the major advances in mineral physics and seismology is the realization that different olivine fabric types are functions of temperature, shear stress, and water content in oceanic subducting systems. The distribution of different olivine fabric types and geodynamic processes in the mantle wedge above a subducting continental slab remain poorly understood. Here, based on splitting analysis of shear waves recorded by 46 stations recently deployed in central Myanmar, we reveal trench-perpendicular fast orientations between the 80 and 100 km slab contours sandwiched between trench-parallel fast orientations from the mantle wedge tip to the backarc. The dramatic change in fast orientations indicates the transition of olivine fabric types in the mantle wedge combined with corner flow. Cold continental subduction and shear stress reduction caused by partial melting favor B-type and C- or E-type olivine fabrics, respectively.