shear-induced metal segregation in ordinary chondrites: implications for planetary core formation

这个项目是关于成长中的行星体的核心形成过程。样品材料是一颗陨石（技术上是H6普通球粒陨石），含有Ni-Fe-S形式的“金属”。目前，我们基于实验的理解是，在非静水条件下，变形机制（剪切）为液态金属分离提供了独立于表面张力影响的局部高渗透性路径。在部分熔融的硅酸盐基质中，变形在促进分离（有时称为渗滤）方面的作用挑战了长期存在的想法，即行星体中的核心形成需要岩浆海洋。然而，迄今为止，只有少数实验室对自然样品进行了实验。尽管这些实验很重要，但它们不能提供关于剪切过程中液态金属运输的详细流体动力学的可靠信息，也不能对变形驱动的岩心形成中的多孔流动的更大规模影响作出显著评论，而只能通过推测。所需的信息水平只能从数字模型中获得。然而，实验确实提供了关键的纹理和几何信息，并在天然样品中提供了与孔隙尺度流动有关的地球化学数据。我们提供了一个综合的方法，使用纹理数据从真实的陨石，在实验室条件下变形，作为我们的数值模型的输入数据。这一结果将使我们能够在行星核心形成的更广泛背景下探索铁金属硅酸盐熔体偏析的微观物理和化学后果。

This project is concerned with the process of core formation in growing planetary bodies. The sample material is a meteorite (technically an H6 ordinary chondrite) that contaims 'metal' in the form Ni-Fe-S. Presently, our understanding based on experiments is that under non-hydrostatic conditions, deformation mechanisms (shearing) provide local high permeability pathways for liquid metal segregation independent of surface tension effects. The role of deformation in promoting segregation (sometimes referred to as percolation) in a partially-molten silicate matrix challenges the long-standing idea that core formation in planetary bodies requires a magma ocean. However, only a small number of laboratory experiments on natural samples have been done to date. As important as they are, these experiments cannot provide robust information on the detailed fluid dynamics of liquid metal transport during shear, nor comment significantly on the wider scale implications of deformation driven porous flow in core formation other than through speculation. The required level of information can only be obtained from numerical modelling. Experiments do however provide critical textural and geometrical information and in natural samples, geochemical data pertinent to pore-scale flow. We offer a combined approach that uses textural data from real meteorites, deformed under laboratory conditions, as input data for our numerical models. The result will allow us to explore the microscale physics and chemical ramifications of Fe metal-silicate melt segregation in the wider context of planetary core formation.