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液体（称为熔体）的迁移密切相关，液体从超固相线区域迁移到次固相线区域，在超固相线区域，液体因部分熔融而起源于亚固相线区域，最终在亚固相线区域形成并冻结为岩床、岩体或火山产物。超固相线和次固相线区域中的熔体迁移已分别成功地建模为压实基质内熔体的两相多孔流和穿过主固体岩石传播的岩脉。然而，从超固相线区域到亚固相线区域过渡时熔体传输过程的演变仍然知之甚少。当向表面迁移时，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。 尽管超固相线区域的热不平衡发展可能是理解接近亚固相线过渡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。该项目旨在评估热不平衡对超固相线区域熔体偏析和传输的影响，以及对向次固相线过渡时岩脉萌生的影响。使用 Schmeling 等人提出的公式。 （2017）针对多孔流中的热不平衡，我们建议开发一种非热平衡两相流模型。通过这个新模型，我们将评估和量化热效应对熔体偏析和传输的影响。结果可能会为堤坝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数值模型，用于熔体从原始熔化区域迁移到最终安置区域，该模型支持超固相线到次固相线过渡时的熔体输运演化。该博士后项目将在美因河畔法兰克福歌德大学地球物理学研究小组内进行，研究人员将特别与 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.