Slab-driven transport of ultra-low velocity material in the deep mantle

It has been suggested that the present-day locations of ultra-low velocity zones (ULVZs), which are thin features just above the core-mantle boundary (CMB), are influenced by mantle convection; however, apart from their preferential locations, there is little direct evidence for this connection. Observations of deep mantle anisotropy can be used to infer mantle dynamics but are not usually jointly analyzed with ULVZ structure. We newly detect and characterize a ULVZ beneath the Himalaya, located approximately at the edge between an (almost) isotropic and a large anisotropic region in the lowermost mantle. Using global wavefield simulations to model realistic mineral physics scenarios, we show that the seismic anisotropy is indicative of northeast-southwest flow directions. The southwestwards flow is likely induced by slab remnants at the CMB, and the ULVZ is located at the southwestern edge of the anisotropic province, which is indicative of slab-induced ULVZ displacement.