硅酸盐熔体和液态铁的两相模拟与核幔间的氧交换

Coexistence simulations of silicate melts and liquid iron and the exchanges of oxygen between the Earth′s mantle and core

地球早期经历了很多撞击事件,其中与地月系统形成相关的大撞击甚至造成深达核幔边界的全球规模的岩浆洋,在此过程中的核幔分异基本确定了地幔与地核的物质组成,也决定了地球随后的演化路径.我们采用基于量子力学理论的第一性原理方法和机器学习技术,实现了硅酸盐熔体和液态铁的超大体系两相分子动力学模拟,获得了核幔边界条件下的两相平衡数据,为超深岩浆洋中的核幔分异过程提供了重要约束.基于本研究模拟结果和现有的高温高压实验数据,我们还建立了能够准确预测核幔间元素交换的平衡模型,利用该模型深入探讨了核幔间的氧交换问题,并分析了其与地球生长、大撞击和岩浆洋事件、地球早期磁场等争议问题之间的关系.

The Earth experienced many catastrophic collisions in its early history,among which the Giant Impact that leaded to the formation of the Earth-Moon system might have generated a global super-deep magma ocean down to the core-mantle boundary.The accompanying core-mantle differentiations determined the compositions of the mantle and core and set up the subsequent evolution history of the Earth.In this study,we carried out coexistence simulations of silicate melts and liquid iron with unprecedented large systems based on first principles and machine learning techniques.We obtained the equilibrium properties of the two phases under core-mantle boundary conditions,which is important for constraining the super-deep core-mantle differentiations.Using these new simulation data and literature experimental results,we refined a new equilibrium model that could be more accurate for quantifying the element exchanges between the Earth′s mantle and core.With this model we discussed the exchanges of oxygen and the compositions of the core and proposed a new scenario to solve the still disputed problems.