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

岩浆地球动力学中尚未解决的主要问题之一是从物理上理解从软流圈或下地壳内的源区到浅层侵入、岩浆房或挤出的熔体上升的完整序列。超固相线源区内熔体上升的物理过程通常用可变形蠕动岩石基质中熔体的两相流动来描述。通常求解熔体和基质的质量守恒方程、动量守恒方程和能量守恒方程。岩浆通过未熔融的地下岩石圈或地壳上升，通常用岩墙通过脆性-弹性介质传播的力学模型来描述。在这个项目中，我们将第一次在一个自我一致的人中结合和耦合这两种方法。一个先进的熔体提取和就位模块将扩展包括熔体两相流在内的地壳或岩石圈尺度模型，该模块将在地球动力学时间步长(年到千年)采用两相流代码给出的分布的部分熔体体积和应力场，以计算在小时到天的时间尺度上的自洽岩脉传播，并将堤坝截留或挤压后修正的岩浆分布和演化的应力场反馈到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，岩墙的熔体提取将首次与源区熔体的产生和构造系统的地球动力学演化直接耦合。新方法将应用于地壳岩浆作用，如阿尔蒂普兰诺(安第斯山脉)等增厚地壳情景，以及软流圈-岩石圈规模裂谷-羽流系统，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.