[S-IT14] Deep Earth Sciences

[SIT14-P21] Carbon partitioning during core-mantle differentiation constrained from ab initio simulations

*Shengxuan Huang¹, Taku Tsuchiya¹ (1.Geodynamics Research Center, Ehime University)

Keywords:carbon partitioning, core-mantle differentiation, ab initio molecular dynamics, thermodynamic integration method

Carbon, as an Earth’s major volatile element, plays a key role in regulating the climate and habitable surface environment, and is extensively involved in mantle geodynamical processes. The abundance of carbon in the bulk silicate Earth (BSE) is estimated to be 90~130 ppm. And the BSE is characterized as super-chondritic C/N, sub-chondritic C/H and chondritic C/S ratios. Understanding the origin of such features is essential to unveil the origin and delivery of life-essential volatile elements and requires the knowledge of their partitioning behaviors during core-mantle differentiation. Among these elements, the results about carbon partition coefficients under high-pressure and high-temperature are highly controversial. For instance, previous experiments conducted at relatively low pressures (< 8 GPa) have reported that carbon is strongly siderophile and becomes more with increasing pressure. By contrast, experimental and theoretical evidences demonstrate that carbon is much less siderophile at pressures of 35~60 GPa, though those data scatter more than an order of magnitude. In this study, we perform ab initio molecular dynamics combined with the thermodynamic integration method to calculate partition coefficients of carbon between iron and silicate melts to 135 GPa and 5000 K. These results enable us to evaluate the effects of different physical and chemical variables on the partitioning behavior of carbon. And they will provide important constraints on the distribution of carbon in the deep Earth and the origin of the Earth’s volatiles.