Sulphur from heaven and hell

Abstract

Fingerprints of sulphur isotopes in rocks from the ridge beneath the Atlantic Ocean suggest that a substantial fraction of sulphur at Earth's surface is left over from the formation of the planet's core. See Letter p.208 The differentiation of early Earth's subsurface material into core and mantle layers should be reflected in the residual mantle composition, as most of the iron-loving elements, presumably including sulphur, would have been scavenged by the liquid core. However, previous analyses of Earth's mantle have identified stable sulphur isotope ratios resembling those seen in chondritic meteorites, perhaps the result of a 'late veneer' meteoritic origin for mantle material. But here Jabrane Labidi et al. provide evidence that the mantle displays heterogeneous sulphur isotope ratios directly correlated to strontium and neodymium isotope ratios. The authors conclude that these results can be reconciled by fractionation during core-mantle differentiation.