20-EPN2-91: Experimentally determined distribution of highly siderophile elements between sulfide- and silicate melts at highly reduced conditions: implications for terrestrial late accretion models
Visit by Edgar Steenstra, Institute of Mineralogy, WWU Muenster (Germany) to TA2.2 VU (Exo)Planetary Interior Simulation Laboratory (PISL).
Dates of visit: 22 – 24 November 2022
Report Summary: Fifteen high-pressure experiments on the PISL end-loaded piston cylinder press were performed at 1 GPa and 1873 K to systematically investigate the effects of Cu and Ni on metal- and sulfide-silicate partitioning of highly siderophile elements (HSE) Pd, Ru, Pt and Ir. Run times at peak conditions varied around 60-90 minutes. The starting compositions consisted of silicate, sulfide and metal powders with added metallic Si. The experimental run products consist of well-segregated metallic and sulfide blobs in a silicate glass. The addition of metallic Si and the initial reduction of the experiments result in the suppression of nugget formation. The glass does contain minute specks typical of S- saturated silicate melts – subsequent LA-ICP-MS measurements of the run products show that these specks do not contain HSE, as initially hypothesized. Electron microprobe and LA-ICP-MS analyses further show that the experimental run products are homogeneous and no compositional zoning was observed. Initial results show that the addition of Cu and Ni to the sulfide liquid decreases the O content of that sulfide liquid at a given FeO value of the silicate melt. This will most certainly affect the partitioning of the elements of interest – preliminary results for Pt confirm this by its variation by three orders of magnitude at a given FeO content. Preliminary results also show that Pd, Ru, Pt, Ir are all preferentially partitioned into the metallic liquid instead of the sulfide melt, confirming their preference for S-poor alloys relative to S-rich liquids.