地球形成早期核幔分异平衡程度研究

It is a consensus that the Earth is formed by the accretion of planetary embryos. There are two ways for the embryo's core merges with that of the Earth. One is that the embryo's core emulsifies into small liquid drops and passes through liquid-state mantle (magma ocean). Another is that the embryo's core does not divide and merge directly with the Earth's core. High equilibrium degree of the embryo's core with proto-Earth's mantle is expected in the first case while non-equilibrium is expected in the second case. The equilibrium degree influences the chemical compositions of both the core and the mantle of the Earth. More importantly, it influences our determination of the timing of Earth formation. Thus, we propose to study the core-mantle equilibrium degree in the early history of the Earth. The research will be divided into four steps. The first one is the determination of the light element content of the core by combining geophysical and mineral physical methods. The second step is the determination of the partition coefficients of light elements between liquid iron and silicate melt at various temperatures and pressures. The third step is to build earth accretion models, and the fourth step is to use the light element content of the core as a criterion to infer the valid core-mantle equilibrium degree. The innovative point of the present research is the combination of light element content of the core with core-mantle equilibrium degree.

现在一般认为地球的形成是由于星胚相互撞击聚合形成。星胚撞击到地球，星胚本身的铁核进入到地核中有两种方式。一种是星胚的核发生分解，变成小液滴，穿过处于液态的岩浆洋地幔，进入地核；另外一种是星胚核没有分解，呈大球体直接进入地核。第一种方式，液态铁与地幔有很好的平衡；而第二种方式液态铁与地幔没有平衡。地核与地幔的平衡程度对地核和地幔成分，以及地球早期形成历史的研究均具有重要意义，因此本项申请将地球早期核幔平衡程度作为研究目标。核幔平衡程度研究将分为四个大的步骤。首先将地球物理与矿物物理方法相结合，确定地核轻元素的含量；第二步通过两相法第一原理分子动力学确定轻元素在各种温压条件下，在液态铁和硅酸盐熔体之间的配分系数；第三步是建立星胚聚合模型；第四步以地核轻元素含量作为标准，获得有效的平衡程度值。将地核轻元素含量和核幔平衡程度相结合是本项研究的创新之处。