A Hybrid Mechanism for Enhanced Core‐Mantle Boundary Chemical Interaction

Abstract

AbstractDetection of chemical signatures from the core‐mantle boundary (CMB) could provide an unprecedented glimpse into our planet's deep interior and ancient past. Several isotopic and elemental anomalies in ocean island basalts (OIBs) have been proposed as core tracers. However, the process(es) by which particular chemical signatures from the core are conveyed into the mantle remain uncertain. Here, we propose a hybrid mechanism that results from a collaborative feedback between dynamic topography, porous infiltration of liquid metal into submerged rock, gravitational collapse of weakened metal‐silicate mush, and draw‐down of additional rocks from above in the induced small‐scale mantle circulation. Using a mantle convection model coupled to gravitational spreading of a thin layer, we show that induced mantle circulation due to the gravitational collapse of the layer becomes comparable to buoyancy‐driven mantle flow when the viscosity of the mushy layer is reduced to values ∼105 times smaller than the overlying mantle.