The manner in which magmas go towards mid-oceanic ridges is reasonably well understood. Yet, manner in which they move through continental lithosphere is much more poorly understood and at the same time much more relevant as people tend to live there. Only a small fraction of melts ever make it to the surface and large quantities get stuck along the way in batholiths. There are some ideas on how melt moves through colder rocks, but those ideas remain largely cartoon models without quantification of key dynamic parameters: 1) magma production rates, 2) physical barriers to magma flow, 3) magma ascent rates, 4) magma reservoir lifetimes, and 5) physical mechanisms to reactivate conduits and feeder systems.
Driven by buoyancy and sometimes by tectonic stress, magmas are mobile agents of mass and energy transfer both within the solid Earth and from the solid Earth to the atmosphere. Silicate melts initially form on the boundaries between crystals and must migrate into larger structures to efficiently travel large distances. Once magma forms and becomes buoyant, it rises through cracks in the earth. Understanding how faults form in the face of growing magma batches will help us predict where volcanoes will form and allow us to develop models of how seismicity relates to volcanic unrest.
Magma supply requires flow, and this may occur through discontinuities and channels in solid crustal rocks or along grain boundaries in partly molten rocks. Magma migration therefore constitutes a coupled fluid-rock system that leads to the transfer of both thermal and mechanical energy of both viscous and elastic (solid state) nature. We develop and use multi-phase numerical geodynamic models of migration processes and are working on coupling them with realistic thermodynamic models of the melting process itself. Modeling the formation and migration of volatile-laden magma bodies – a key goal in this theme – must account for the rates of flow, heat production, heat loss and solid-to-liquid state phase transitions (melting/crystallization). Some of these variables are known for a few key magma types, but a comprehensive knowledge is not yet firmly in hand.
Example of a folded turbidite, Namibia
Magma transport channels: an isoclinally folded aplite vein (bottom) in a mylonitic gneiss, is cut by leucogranite dykes with a thin offshoot parallel to the foliation (at left).
Example of 2D geodynamic models of tectonic lithospheric deformation (with visco-elasto-plastic rheologies) coupled with multiphase fluid migration that can occur along shear bands, in dikes or through two-phase compaction instabilities.
You can also check this YouTube video on multiphase models.
Prof. Cees Passchier focuses on the rheological behaviour and microstructural deformation of rocks.
Prof. Boris Kaus leads the research on computational modelling of lithospheric processes at multiple scales.