Spatial Characteristics of Recycled and Primordial Reservoirs in the Deep Mantle

The spatial distribution of the geochemical domains hosting recycled crust and primordial (high-3He/4He) reservoirs, how they are linked to mantle convection, poorly understood. Two continent-sized seismic anomalies located near core-mantle boundary—called Large Low Shear Wave Velocity Provinces (LLSVPs)—are potential reservoir hosts. It has been suggested that high-3He/4He hotspots spatially confined LLSVPs, sampling continental associated with only one shows no relationship latitude. We reevaluate links between LLSVPs isotopic signatures hotspot lavas using improved flow models including plume conduit advection. While most highest-3He/4He can indeed be traced LLSVP interiors, at least hotspot, Yellowstone, is outside LLSVPs. This suggests not geographically Instead, a positive correlation buoyancy flux maximum 3He/4He it dynamics (i.e., buoyancy), geography, which determines whether dense, deep, possibly widespread entrained. also show plume-fed EM (enriched mantle, low-143Nd/144Nd), signaling crust, both primarily in southern hemisphere. Lastly, we confirm HIMU (“high-?,” or high 238U/204Pb) limited These findings clarify advance our understanding deep distributions, discuss oceanic subduction consistent decoupling HIMU.