I am an associate professor in the Department of Earth Sciences at the University of Oregon. My group designs new experimental methods and mathematical models to interpret isotopic and chemical variations in geologic materials. The lab projects we are working on include:
Our current field areas are:
The abundances of stable isotopes in carbonate minerals are widely used to infer paleo-environmental conditions. Oxygen isotopes, for example, record the temperature of carbonate formation. Although these types of proxies work in many settings, there are important details that need to be worked out to fully capitalize on stable isotope measurements. We are growing calcite and aragonite in the lab from aqueous solutions to figure out what environmental variables in addition to temperature are recorded in the oxygen, carbon, and clumped isotope composition of carbonates.
Crystal and bubble shapes in magma are sensitive to temperature, pressure, and magma ascent rate. We simulate volcanic conditions in the lab by heating/cooling and compressing/decompressing magma to figure out how textures in volcanic rocks are created by non-observable processes in the subsurface. The photo is a pumice created by undergraduate Eamonn Needham.
Bubbles are generally thought to grow as magma rises. Volatile concentration gradients around bubbles, however, show that bubbles can undergo cycles of growing and shrinking as a consequence of magma deformation. We are growing bubbles in the lab, sintering ash, and studying pyroclasts from volcanoes in Oregon and California to better understand what actually happens to volatiles when magma rises through the shallow crust.
Magmatic-hydrothermal fluids in the crust transport and deposit ore metals in some settings, and in other settings, they feed hot water into high-temperature geothermal systems used to produce electricity. Exactly how minerals precipitate in these environments is not well understood because we cannot directly observe the processes. We are growing quartz crystals in the lab under controlled conditions to find ways of figuring out the temperature, depth and growth histories of quartz crystals in natural hydrothermal systems.
A key assumption in many geochronological studies is that minerals retain the parent and daughter nuclides throughout their existence. Diffusive separation of the parent and daughter isotopes, which can occur when a rock is subjected to reheating events or during the initial cooling of a rock, can give rise to apparent ages that can be too old or too young. We applied these principles to understand why Lu-Hf ages of eucrite meteorites appeared to (erroneously) pre-date the age of the solar system.
The goal of stable isotope geochemistry is to interpret variations in isotopic abundances that are observed in nature. This requires an understanding of how isotopes are separated during diffusion, chemical reactions, and partitioning between phases. We are measuring small differences in the diffusivities of isotopes to figure out how cations diffuse in liquids and to predict where and when diffusion is responsible for stable isotope variations in nature.
We're always going down new rabbit holes and undergrads are encouraged to participate. Current and past undergrads have worked on snowflake obsidian, travertine formation, the Soret effect, crystallization experiments, and FTIR measurements of volatiles in obsidian pyroclasts. Many of the projects involve hands-on experience with high-temperature, high-pressure experimental apparatuses and high-tech instrumentation housed in the Lokey Lab.