Non thermal equilibrium two-phase flow of melt in a compacting matrix : insights on melt migration and dike initiation in the upper mantle

海洋和大陆地壳的形成与被称为熔体的液体的迁移密切相关，这些液体从超固相区域（由于部分熔融而产生）迁移到亚固相区域，在那里它们最终安置并冻结为岩质、岩体或火山产物。熔体在超固相和亚固相区域的迁移已经成功地分别模拟为熔体在压实基质内的两相多孔流动和在宿主固体岩石中传播的岩脉。然而，从超固区到亚固区的熔体输运过程的演变仍然知之甚少。在向地表迁移的过程中，熔体路径合并并加宽，熔体输运条件由热平衡向不平衡演变。虽然超固相区域的热不平衡发展可能是理解向亚固相过渡时熔体输运演变的关键，但在熔体迁移两相流模型中从未考虑过这一点。本项目旨在评估热不平衡对超固相区域熔体偏析和输运的影响，以及对向亚固相过渡时岩脉形成的影响。利用Schmeling等人（2017）提出的多孔流动中热不平衡的公式，我们建议建立一个非热平衡两相流模型。根据这个新模型，我们将评估和量化热效应对熔体偏析和输运的影响。结果可能为岩脉的形成过程提供有趣的见解。在与Herbert Wallner， Harro Schmeling和Eleonora riverta的合作中，我们将利用这些信息开发一个自一致的熔体从原始融化区到最终安置区的迁移数值模型，该模型支持熔体在超固体到亚固体过渡阶段的迁移演化。该博士后项目将在法兰克福的Goethe Universität进行，在地球物理研究小组内，研究人员将与Harro Schmeling和Herbert Wallner合作。

The formation of oceanic and continental crust is tightly linked with the migration of liquids, called melts, from super-solidus regions, where they originate because of partial melting, to sub-solidus regions where they finally emplace and freeze as sills, plutons, or volcanic products. Melt migration in super- and sub-solidus regions has been successfully modeled respectively as two-phase porous flow of melt within a compacting matrix and as dikes propagating through the hosting solid rock. However, the evolution of melt transport processes at the transition from super- to sub-solidus regions remains poorly understood. While migrating towards the surface, melt pathways merge and widen, and melt transport conditions evolve from thermal equilibrium to disequilibrium. Although thermal disequilibrium development in super-solidus regions may be key for understanding melt transport evolution when approaching the transition to sub-solidus, it has never been considered in melt migration two-phase flow models. This project aims at evaluating the influence of thermal disequilibrium on melt segregation and transport in super-solidus regions, as well as on dikes initiation at the transition to sub-solidus. Using the formulation proposed by Schmeling et al. (2017) for thermal disequilibrium in a porous flow, we propose to develop a non thermal equilibrium two-phase flow model. From this new model we will evaluate and quantify the influence of thermal effects on melt segregation and transport. Results may provide interesting insights on dikes initiation processes. In collaboration with Herbert Wallner, Harro Schmeling and Eleonora Rivalta, we will then use these informations for developing a self-consistent numerical model for melt migration from the original melting area to final emplacement zones, that supports melt transport evolution at the super- to sub-solidus transition. This post-doctoral project will be held in the Goethe Universität in Frankfurt am Main, within the Geophysics research group, from which the researcher will especially collaborate with Harro Schmeling and Herbert Wallner.