Primordial and recycled helium isotope signatures in the mantle transition zone

Abstract

Diamond window into the deep mantle Helium isotopes provide a window into the very deepest and oldest parts of Earth's voluminous mantle. However, several processes tend to obscure the helium isotope signal from reservoirs in basaltic lavas that have erupted at the surface. Timmerman et al. identified a set of diamonds that formed deep within Earth and were rapidly erupted, which have avoided near-surface contamination. They find evidence for a deep, primordial rock source along with mixing of sediments from old subducting plates. The signatures extracted from these diamonds have implications for chemical and dynamic models of Earth. Science , this issue p. 692