Mechanisms and Geochemical Models of Core Formation
Mechanisms and Geochemical Models of Core Formation
复制标题
岩心形成机制和地球化学模型
DOI：
10.1002/9781118992487.ch14
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Seth Andrew Jacobson
中科院分区：
文献类型：
--
作者：
D. Rubie;Seth Andrew Jacobson
地核的形成是行星吸积和地球内部过程的结果。行星分化的机械过程很可能发生在由行星胚胎碰撞形成的大型（即使不是全球性）岩浆海洋中。根据实验室实验和计算，与颗粒级渗滤不同，岩浆海洋中的金属硅酸盐分离快速有效地发生。随着行星吸积的进行，核心形成过程的地球化学模型变得越来越现实。单阶段和连续核心形成模型已发展为多阶段模型，这些模型与行星形成巨大撞击阶段的动力学模型的输出耦合。基于实验得出的元素分配系数，最成功地匹配地幔化学成分的模型表明，金属硅酸盐平衡的温度和压力必须随着时间和质量累积的函数而增加，平衡材料的氧逸度也必须增加。如果硅进入核心并通过氧化材料的后期输送，则可能发生后者。耦合动力吸积和多阶段核心形成模型同时预测了所有类地行星不断演化的地幔和核心成分，并对原行星盘中原始天体的整体成分和氧化态施加了严格的限制。
The formation of the Earth's core is a consequence of planetary accretion and processes in the Earth's interior. The mechanical process of planetary differentiation is likely to occur in large, if not global, magma oceans created by the collisions of planetary embryos. Metal-silicate segregation in magma oceans occurs rapidly and efficiently unlike grain scale percolation according to laboratory experiments and calculations. Geochemical models of the core formation process as planetary accretion proceeds are becoming increasingly realistic. Single stage and continuous core formation models have evolved into multi-stage models that are couple to the output of dynamical models of the giant impact phase of planet formation. The models that are most successful in matching the chemical composition of the Earth's mantle, based on experimentally-derived element partition coefficients, show that the temperature and pressure of metal-silicate equilibration must increase as a function of time and mass accreted and so must the oxygen fugacity of the equilibrating material. The latter can occur if silicon partitions into the core and through the late delivery of oxidized material. Coupled dynamical accretion and multi-stage core formation models predict the evolving mantle and core compositions of all the terrestrial planets simultaneously and also place strong constraints on the bulk compositions and oxidation states of primitive bodies in the protoplanetary disk.