Tracing volatile elements delivery on Earth with S, Se and Te

Volatile elements (e.g. H, C, S) have a fundamental role in planetary evolution but how budgets of volatiles were set in planets and the mechanism of volatile depletion in planetary bodies remains poorly understood and represents a fundamental obstacle in understanding the chemical processing of terrestrial planets. Discrimination between the processes for the origin of volatile elements is a key constraint for understanding the budget of volatiles in Earths deep reservoirs and most notably the nature of light elements in the core, as well as the longstanding issue of Earths accretion process and the nature of its building blocks. Here, we provide experimental constraints on the accretion and budget in Earths interior of the moderately volatile and siderophile elements sulfur (S), selenium (Se), and tellurium (Te). These elements have similar and quite low 50% condensation temperatures but display very different degree of siderophility. Thus, relative abundances of these elements in the Earths mantle should accordingly record the imprint of core-mantle equilibration. However, recent measurements on Earths mantle samples have shown that S, Se, and Te displayed chondritic ratios consistent with the view that volatile elements were mostly provided to the Earth by a late veneer after core formation is completed. To date, partitioning data obtained from multi-anvil press (up to 18 GPa and 2400 C) have shown that metal-silicate partition coefficients are different for each of those elements (DTe > DSe > DS) supporting the model of a volatile-rich late veneer to account for the budget of volatiles in the mantle. Here we propose to measure the partitioning of S, Se and Te between metal and silicate melts at conditions directly relevant to core formation in a deep magma ocean (>50 GPa and > 3500 K) using the diamond anvil cell and laser heating techniques. These results are used to test whether the abundances of these elements can be predicted by current models of Earth differentiation involving metal-silicate equilibrium. Consequently, we evaluate if the addition of a given type of meteorite component following initial core formation can raise mantle abundances of S, Se, and Te to their current level.