Modelling melt ascent through the asthenosphere-lithosphere-continental crust system: Linking melt-matrix-two-phase flow with dyke propagation

岩浆地球动力学中一个尚未解决的主要问题是对熔体从软流圈或下地壳内的源区上升到浅侵入体、岩浆房或喷出物的完整序列的物理理解。超固相线源区内熔体上升的物理过程通常用熔体在可变形蠕变岩石基质内的两相流动来描述。熔体和基体的质量、动量和能量守恒方程通常是求解的。岩浆上升通过未熔融的，subsolidus岩石圈或地壳通常是通过一个脆弹性介质岩墙传播的力学模型来描述。在这个项目中，我们将联合收割机和耦合这两种方法首次在一个自我consisten manner。本文将采用一个先进的熔体提取和侵位模块来扩展包括熔体两相流的地壳或岩石圈尺度模型。该模块将采用由两相流程序给出的在地球动力学时间步长上的分布的部分熔体体积和应力场（年至千年）以计算数小时至数天时间尺度上的自洽堤坝传播，并将岩脉停止或挤出之后的修改的岩浆分布和演化的应力场反馈到用于下一个地球动力学时间步长的地球动力学模型中。通过这种方法，岩墙熔体提取将首次直接耦合到源区熔体生成和构造系统的地球动力学演化。新的方法将被应用于地壳岩浆活动，如在加厚地壳的情况下，如高原（安第斯山脉），和软流圈-岩石圈规模的裂谷-羽状系统，如东非裂谷系统。

One of the major unresolved questions in magmatic geodynamics is the physical understanding of the complete sequence of melt ascent from the source regions within the asthenosphere or lower crust to shallow intrusions, magma chambers or extrusions. The physics of melt ascent within the supersolidus source regions is usually described by two-phase flow of melt within a deformable, creeping rock matrix. Conservation equations of mass, momentum and energy for melt and matrix are usually solved. Magma ascent through the unmolten, subsolidus lithosphere or crust is usually described by mechanical modelling of dyke propagation through a brittle-elastic medium. In this project we will combine and couple these two approaches for the first time in a self-consisten man-ner. Crustal or lithospheric scale models including two-phase flow of melt will be extended by an ad-vanced melt extraction and emplacement module, This module will take distributed partial melt volumes and stress fields given by the two-phase flow code at geodynamic time steps (years to kyears) to calculate self-consistently dyke propagation on timescales of hours to days, and feed the modified magma distribution after dyke arrest or extrusion and the evolved stress field back into the geodynamic model for the next geodynamic time-step. By this approach melt extraction by dykes will be directly coupled to melt generation in the source region and the geodynamic evolution of the tectonic system for the first time. The new approach will be applied to crustal magmatism such as in thickened crust scenarios like the Altiplano (Andes), and to asthenosphere – lithosphere scale rift-plume systems such as the East African Rift System.