Special Seminar (Brown Bag) - Luo

Sep 23, 2022, 10:00 am11:00 am
Brown Bag
Event Description

The hypothesis of late veneer has been commonly employed to explain the origin of certain volatile elements and highly siderophile elements (HSEs: Ru, Rh, Pd, Re, Os, Ir, Pt, and Au) of bulk silicate Earth. However, the necessity of the late veneer is still in debate due to the lack of metal-silicate partition coefficients of HSEs under high-pressure and high-temperature conditions as experienced during core formation. In fact the newest experimental data suggest that there is too much Pt left behind after core formation and the late veneer is not required to explain the abundance of Pt in the mantle (Suer et al., 2021). Sulfide segregation (the “Hedean matte”) is a widely proposed mechanism to remove excess HSEs (if any), but there are even fewer studies on sulfide-silicate partition coefficients of HSEs during core formation. Here we have calculated molten metal/sulfide - silicate melt partition coefficients of HSEs under core formation conditions based on ab initio molecular dynamics simulations coupled with thermodynamic integration method. It is shown that most of the metal-silicate partition coefficients of HSEs still differ from each other by 0.5-3 orders of magnitude up to 135 GPa and 4200 K. This implies that late veneer is still needed to explain the abundances of at least some of HSEs in the primitive upper mantle. Our calculated sulfide-silicate partition coefficients of HSEs suggest that sulfide segregation might help remove some excess HSEs (e.g., Pd), but it could help preserve even more HSEs in the mantle in some other cases (e.g., Pt).


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