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

大洋和大陆地壳的形成与被称为熔体的液体从超固相线区域(由于部分熔融而起源)到亚固相线区域的迁移密切相关，在那里它们最终以岩床、深成岩或火山产物的形式就位并冻结。超固相线区域和亚固相线区域的熔体迁移分别被成功地模拟为熔体在压实基质中的两相渗流和岩脉在承压固体岩石中的传播。然而，熔体传输过程在从超固相线区域向亚固相线区域的转变过程中的演变仍然知之甚少。当熔体向表面迁移时，熔体路径合并并加宽，熔体传输条件从热平衡演变为不平衡。虽然超固相区的热不平衡发展可能是理解向亚固相线转变时熔体输运演化的关键，但在熔体迁移两相流模型中从未考虑过它。本项目旨在评估热不平衡对超固相线区域熔体分凝和迁移的影响，以及在向亚固相线过渡时对岩脉启动的影响。使用Schmeling等人提出的公式。(2017)对于渗流中的热不平衡，我们提出了一个非热平衡两相流模型。从这个新的模型中，我们将评估和量化热效应对熔体分离和传输的影响。研究结果可能会对堤坝的启动过程提供有趣的见解。然后，我们将与Herbert Wallner，Harro Schmeling和Eleonora Rivalta合作，利用这些信息开发一个自洽的熔体从原始熔融区迁移到最终侵入区的数值模型，该模型支持熔体在超固相线到亚固相线转变时的迁移演化。这个博士后项目将在美因河畔法兰克福的歌德大学地球物理研究组内举行，研究人员将特别与哈罗·施梅林和赫伯特·沃尔纳合作。

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.