My research focuses on the petrogenesis of igneous rocks, i.e., the processes of magma generation, solidification, and eruption. I am particularly interested in planetary differentiation and volcanism, and in understanding the geochemical differences and similarities amongst rocky planetary bodies. To better understand the chemistry and time scales of processes occurring in planetary interiors, I conduct experiments that characterize the high-temperature behavior of elements and their isotopes. While a primary focus of my Ph.D. has been the petrology of the Moon, I have also studied the magmas of Mars and Mercury, and am eager to study additional planets, moons, and asteroids as my career progresses.
By quantifying the speed of elemental exchange in minerals, we can decipher important information regarding the timescales of volcanic processes. Ilmenite is an iron- and titanium- bearing oxide mineral commonly found in volcanic rocks. Part of my Ph.D. work has been to experimentally determine how fast Fe, Mg, and Mn cations diffuse in ilmenite. We do this by heating a "diffusion couple" in a piston cylinder, allowing elements to exchange between the two parts of the couple, then measuring the resulting compositional gradient. One important finding from our work is that cation diffusion in ilmenite is strongly affected by oxygen fugacity. This result has important implications for the equilibrium between ilmenite and other oxide minerals in volcanic systems, as ilmenite (FeTiO3, all Fe2+) forms a solid solution with hematite (Fe2O3, all Fe3+), and the oxidation state of Fe greatly influences the migration of elements.
The formation of rocky planets involves a "magma ocean" stage wherein the planetary body is wholly or partially molten and subsequently crystallizes. Segregation and sinking of dense metal within the melt leads to the formation of a metallic core. As the molten body cools, elements are either sequestered in crystals, retained in the melt, or lost to vapor (potentially forming an atmosphere). Post-differentiation, re-melting of crystals within the planetary body generates magmas that may eventually erupt to the surface. Understanding how elements are distributed during all of these processes is essential in placing constraints on both the extent and timing of planetary differentiation and magmatism.
Evidence for Fe isotopic fractionation in igneous rocks suggests there are igneous processes capable of fractionating Fe isotopes to a measurable extent. As a major part of my Ph.D. work, I have been experimentally investigating whether the crystallization of minerals from silicate melt fractionates Fe isotopes. Additional influences on Fe isotopic fractionation in igneous rocks include Fe oxidation state, melt composition, and kinetic processes. In our recent GCA publication, we conclude that no measurable equilibrium fractionation exists between olivine and melt in reducing (all Fe2+) conditions across a wide range of TiO2 contents. We are continuing this work by determining mineral-melt fractionations for pyroxene and Fe-Ti oxides, with the goal of identifying the igneous processes responsible for generating the observed variation in the Fe isotopic compositions of the lunar mare basalts.
Planetary geochemistry is unique in that physical samples are limited to meteorites and samples returned by missions. Remote sensing is a powerful tool for studying the chemistry and petrology of planetary bodies. My research links high-temperature experiments with planetary samples and remote sensing in an effort to characterize the petrology and geochemistry of planetary bodies.