Areas of Active Research
Using both field and experimental techniques, I investigate how geochemistry relates to rheology and the physical processes that result in plate tectonics.
Water in mantle minerals
The majority of my research focuses on the effects of water on deformation processes. Volatiles are fascinating species that have drastic effects on whatever material contains them. In melts, the presence of water decreases the viscosity of the melt, while the presence of carbon dioxide makes explosive eruptions more likely. In hard rocks, trace amounts of water in nominally anhydrous minerals (minerals with non-stoichiometric water contents) also reduces viscosity, in addition to causing melting at lower temperatures. The crystal preferred orientation (CPO) that develops during the deformation of anisotropic minerals like olivine and pyroxene can also change depending on the amount of water in the system, affecting interpretations of seismic anisotropy.
Laboratory investigations of mineral strength
Unlike field studies, where conditions are inferred based on chemical and microstructural analyses, the conditions of deformation experiments can be precisely controlled. This allows us to learn the effects of specific conditions, such as temperature or pressure, on properties like mineral strength. Experimental findings can then be applied to naturally deformed rocks in new field studies.
I utilize nanoindentation and deformation-DIA experiments to look at the behavior of minerals at low-temperature and high-stress conditions. I am particularly interested in understanding the strength profile of Earth’s lithosphere (aka tectonic plates) as this has implications for the processes behind earthquakes and friction on faults, the bending of plates beneath glacial loads and at subduction zones, and the tectonic styles of other planets.
Nanoindentation D-DIA HR-EBSD
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Field studies in the Josephine
Most of my Ph.D. research focused on understanding small-scale deformation in the mantle, which can tell us about the beginnings of plate boundary formation. I have a field site in the Josephine Peridotite of southwestern Oregon, USA. The outcrop I examine, called Fresno Bench, contains dozens of shear zones (areas of localized deformation), each a few centimeters to tens of meters wide. These shear zones are small and have accommodated less strain than deformed peridotites from established plate boundaries like oceanic transform faults. By analyzing samples from transects across these shear zones, I link chemical and rheological properties to understand how the shear zones formed millions of years ago.
SEM/EBSD EPMA SIMS LA-ICPMS TLS SfM