Earthquakes, metamorphism, and melting: understanding the behaviour and evolution of mountain ranges

Despite being some of the most spectacular geological features on Earth, debate still rages surrounding the processes that control the behaviour, sizes, shapes, and evolution through time of mountain ranges. Specific questions concern the material properties of the crust and upper mantle, how they vary through time, and how they are affected by metamorphism and melting. These material properties in turn control the large-scale behaviour and deformation of mountain ranges, and therefore control their sizes, shapes, and evolution through time. Typically, previous studies have used individual methods in isolation to address these questions. In contrast, this project will make new insights by integrating research into earthquakes (using seismology, geodesy, and fieldwork), metamorphism (using fieldwork, petrology, and phase equilibria modelling), melting (using the geochemistry of volcanic rocks), and dynamic modelling. It will therefore be possible to attain a coherent overall understanding of the factors that control the processes and evolution of mountain building, and how they are linked.

The project will study at least two mountain ranges, chosen from a list of exciting potential targets in Eastern Europe, the Middle East, and Asia (which can be discussed in more detail by contacting the supervisors). The present-day deformation will be established using earthquake seismology, satellite geodesy, and fieldwork studies of active faulting. Metamorphic and igneous petrology will be used to probe the history of mountain-building, and the thermal structure at depth (from pressure-temperature-time histories of metamorphic rocks and the chemistry and ages of igneous rocks). These observations will then be synthesised by using dynamic models to investigate the interplay between tectonics, metamorphism, and melting, in order to understand the factors that control the behaviour and evolution of mountain ranges.

The student will begin by conducting fieldwork to collect igneous and metamorphic samples, and make field observations of active faulting preserved in the geomorphology. The samples will be used for petrological analysis, and the modelling of metamorphic phase equilibria and igneous compositions (e.g. Weller et al, 2013). In tandem, the student will use earthquake seismology and satellite geodesy to make new insights into the present-day deformation of the target regions (e.g. Copley et al, 2015). The student will then construct mechanical and thermal models to combine these diverse new observations into an overall understanding of the material properties, deformation, and thermal structure of the ranges (e.g. Copley et al, 2011). Varying the parameters of these models, and investigating which are consistent with the full range of available observations, will therefore reveal the relative importance of the possible factors that control the material properties and behaviour of the ranges (e.g. temperature, metamorphic phase changes, melting, fault strength and reactivation).