Deformation of Earth Materials
An understanding of the deformation mechanisms and rheology of Earth materials is important in comprehending the dynamics of our active and hazardous planet. Integrated research using field studies, advanced microcopy and experimental work is needed to investigate key problems in the deformation behaviour of Earth materials, including the micro- and nanoscale mechanisms that control slip in seismic fault zones, and the coupling of recrystallization to solid-state flow during large strain deformation. The key flow issue controls the behaviour of trans-crustal faults or shear zones of the convecting mantle and of polar ice sheets. The internal crystal plastic flow of ice sheets is also an important, poorly understood, parameter in the large-scale flow and melting of glaciers and polar ice sheets. Current research on ice flow is funded by the (Helmholtz Young Investigators project; Ernst-Jan Kuiper, dr. Ilka Weikusat).
Field-based research on exposed crustal and mantle rocks, in exhumed terranes and xenolith samples, provides insights into the structure, formation, evolution and tectonics of both continental and oceanic lithosphere. Current research topics include the strength contrast between crust and mantle, the origin of metamorphic soles beneath ophiolites (ERC-SINK project; Kalijn Peters) the nature of the lithosphere-asthenosphere transition and also the nature and rheology of plate boundary shear zones (Marie Curie funded project; dr. Vasileios Chatzaras).
The physical and chemical properties of the Earth and other terrestrial planets depend on the atomic to nanoscale structure of their constituent rocks, minerals and fluids. Nanoscience is concerned with investigating material properties that change as physical dimensions approach the atomic scale and quantum effects become important. Earth materials with at least one nanoscale dimension are ubiquitous and include fault rocks, magnetic particles in sediments, biominerals and nanofossils, exsolutions in igneous and metamorphic crystals, intercrystalline fluid films and weathering layers at mineral surfaces, as well as nanoparticles in the atmosphere, oceans and polar ice sheets. Crucially, almost all elementary interactions between the lithosphere, atmosphere, biosphere and hydrosphere generally occur at the nanoscale across mineral surfaces.
Nanogeosciences involves the integration of microscopy, spectroscopy, and theoretical modeling combined with experimental and fieldwork studies on the bulk behaviour associated with nanoscale mechanisms. Electron microscopy and related spectroscopy methods have been key techniques in this field for decades. However, technical advances in instrumentation mean that the field of electron microscopy is now evolving to allow many new advances in the nanoscale study of the structure and properties of Earth materials. Applications include probing the nanoscale structures and processes controlling the dynamic frictional behaviour of seismogenic faults (dr. Oliver Plümper, Bart Verberne). Within the strategic Sustainability theme of Utrecht University, the Faculties of Science and Geosciences are linking their research in the Energy and Resources sector, addressing both upstream and downstream aspects of the resources supply chain. Our research involves characterizing the nanoscale paths and processes controlling flow of natural gas in rocks (dr. Maartje Houben, dr. Yang Liu).
The transformation of rocks and minerals at extremely high pressure and temperature is a fundamental process in the dynamic Earth. Our research on extreme metamorphism concentrates on ultra-high-pressure rocks, produced deep in the Earth and on the role of extraterrestrial impacts in Earth history. Furthermore, ultra-high pressure (UHP) metamorphic rocks exposed at the Earth’s surface provide key data on crustal subduction and/or eduction processes, the nature of deep fluids in the Earth, and crust-mantle interactions during subduction and continental collisions. Work on impact metamorphism has involved the development of new microscopy techniques for the fast identification of shocked minerals, enabling an improved understanding of the role and rate of extraterrestrial impacts in Earth history. Such impacts are a very special type of hazard, which occur infrequently but with devastating effects.
Our research on fluid-rock and mineral interaction spans a large range of scales, from the fundamental interfacial physics of hydration reactions to the mechanisms of fluid release during rock dehydration in subduction zones. An aspect of this interaction is reaction-induced fracture as a potential mechanism for fluid flow and reaction in tight rocks (VENI funded; dr. Oliver Plümper).