Physics of Two Phase Media: Evolution of the Early Earth

关于最早的地球，出现了一个主要的难题：我们如何调和完全熔融初始状态的物理论据与地球化学论据，即这种状态所暗示的差异与现在的地球不相容？一种可能的调和在于更好地理解两相介质（例如，部分熔体）的物理特性，因为关于这类介质如何表现的许多常见的先入为主的观念从未被定量地测试过。数值流体动力学实验将包括以下内容：(1)在冷却过程中剧烈转换的部分熔体的行为：熔体在多大程度上逃逸而不是就地淬火？这与钙钛矿与共存熔体的宏观分化有关。（ii）存在密度交叉时部分熔体的对流（其中液体密度=固体密度）。熔体被排出到什么程度？富含橄榄石的“栖息”层能否发育？在250到500千米的深度？（三）岩心形成时的早期地幔动力学。渗透铁能在多大程度上推动硅酸盐向下熔融？铁在多大程度上驱动破坏原始地幔分层的成分对流？（iv）大撞击造成的混合。(v)后来在稳定分层环境中部分熔化所产生的混合。

A major puzzle has arisen concerning earliest Earth: How do we reconcile the physical arguments for a fully molten initial state with the geochemical arguments that the differentiations implied by this state are incompatible with the current Earth? One possible reconciliation lies in a better understanding of the physics of two phase media (e.g., partial melts) since many of the common preconceptions about how such media behave have never been tested quantitatively. Numerical fluid dynamical experiments will include the following: (1) Behavior of a vigorously converting partial melt undergoing cooling: To what extent does the melt escape rather than be quenched it situ? This pertains to the macroscopic differentiation of perovskite from coexisting melt. (ii) Convection of a partial melt in the presence of a density cross-over (where liquid density = solid density). To what extent is melt expelled? Can an olivine-rich "perched" layer develop ;at 250 to 500 km depth? (iii) Early mantle dynamics in the presence of core formation. To what extent can percolating iron drive silicate melt downwards? To what extent can the iron drive compositional convection that destroys primordial mantle layering? (iv) Mixing created by large impacts. (v) Mixing created by later partial melting in a stably stratified environment.