Abstract

A mantle story told with metal and gas Differences in isotopic compositions of trace elements can help identify how regions of Earth's mantle have evolved over time. Mundl et al. identified several ancient domains that have been isolated from mantle homogenization and thus contain signatures of primordial material. Tungsten and helium isotope values indicate fractionation and isolation of these mantle domains just after Earth's formation. The findings help constrain ancient processes such as core formation, but also provide insight into unexplained structures in the lower mantle today. Science , this issue p. 66