Seminar Lucas Calvo

Abstract

Volatile elements are essential for life and planetary evolution, and understanding their delivery to Earth is crucial for assessing planetary habitability in general. The scientific community has long debated whether the volatile element budget and isotopic signatures observed in Earth’s mantle result from planetary differentiation during the magma ocean stage or from the subsequent « late veneer » event that occurred after core formation. Elements that are both siderophile and volatile provide key constraints on these processes, particularly when investigated through high-pressure and high-temperature experiments that simulate the conditions and compositions of early terrestrial planets.

Here, we present experiments conducted under conditions representative of a deep magma ocean, focusing on moderately siderophile and volatile elements such as sulfur (S), selenium (Se), and tellurium (Te). The experimentally determined siderophile behavior of these elements suggests that most volatile elements were accreted during Earth’s primary accretion phase, with a much smaller contribution from the late veneer than previously proposed. These findings are consistent with the S isotopic composition of Earth’s mantle, although previous studies have reached differing conclusions regarding the influence of planetary differentiation on its signature. We additionally present a second set of experiments at lower-pressure and lower-temperature suggesting that a combination of metal–silicate and vapor–melt isotopic fractionation processes likely established Earth’s mantle isotopic composition. Together, these results imply that both elemental and isotopic evidence point to a limited late veneer contribution to Earth and, by extension, to other terrestrial bodies.