The Influence of pressure and temperature on the metal-silicate partitioning of V, Cr, and Mn: implications for the formation of the Earth’s core

During the formation of the Earth’s core, all elements were fractionated between the metallic core and the silicate mantle according to their chemical affinity. Slightly siderophile elements, such as vanadium, chromium and manganese, are believed to be depleted in the Earth\u27s Primitive Mantle due to a combination of the core formation process and their volatility. Although the Earth\u27s deep interior is inaccessible for direct sampling, it is possible to simulate the manner in which chemical elements fractionated between the core and mantle via metal-silicate partitioning experiments. In the present study, the influence of pressure and temperature on the liquid metal-liquid silicate partitioning of vanadium, chromium and manganese has been determined at pressures between 1 and 4 GPa, temperatures between 1823 and 2023 K, and oxygen fugacities between -3.1 and -2.6 log units below the iron-wüstite oxygen buffer, by piston cylinder experiments. The present study’s results indicate that the partitioning of V, Cr and Mn are independent of pressure. A weak-to-negligible partitioning dependence on temperature is observed, with V and Cr displaying decreasingly siderophile behavior with increasing temperatures and Mn displaying the opposite trend. Since chemical elements partition based upon pressure, temperature, oxygen fugacity and melt composition, the partitioning behavior of V, Cr and Mn provides valuable insight into the conditions as which core-mantle differentiation may have occurred. Parameterization of the effects of P and T on element partitioning indicates that single-stage core formation is plausible in a deep magma ocean, but unlikely in a shallow or intermediate depth magma ocean