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

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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.