Partitioning behavior at 9Â GPa in the Fe-S system and implications for planetary evolution

Solid metal/liquid metal partitioning experiments were conducted at 9 GPa and 1323-1873 K in the Fe-S system. Analysis of the experimental charges by in situ laser ablation inductively coupled plasma mass spectrometry enabled partitioning results to be obtained for a total of 21 trace elements (Co, Ni, Cu, Ga, Ge, As, Mo, Ru, Rh, Pd, Ag, Sn, Sb, W, Re, Os, Ir, Pt, Au, Pb, and Bi). This new, elevated pressure dataset for the Fe-S system allows a direct comparison to the extensive data available at 0.1 MPa and permits evaluation of the effect of pressure on partitioning in this system. The majority of the elements studied exhibit different solid metal/liquid metal partitioning behaviors at 9 GPa than at 0.1 MPa. Additionally, the nature of these differences varies significantly between the 21 trace elements studied, spanning the range of behaviors of partitioning from more strongly into solid metal, to less strongly into solid metal, and to becoming insensitive to the metallic liquid composition. We conclude that pressure affects solid metal/liquid metal partitioning behavior in the Fe-S system and discuss the implications for fractionations due to Earth's core solidification and for planetary differentiation models.

Research highlights► New solid metal/liquid partitioning data in the Fe-S system at 9 GPa, 1323-1873 K. ► Comparison to 0.01 MPa data reveals pressure has a large effect on partitioning. ► Data for 21 elements show effect of pressure differs significantly between elements. ► Results have implications for planetary core formation and evolution models.