From 4.4 billion year old detrital zircons to modern volcanism, the continental crust contains a near-continuous record of the processes that have shaped the Earth. Not only is the continental crustal a window into the past, it is a nexus connecting the deep Earth, the hydrosphere and the biosphere. My primary research interest is understanding the rates, timescales, and processes influencing the chemical evolution of the continental crust. To this end, I utilize observations of natural systems and experimental studies to investigate the chemistry of rocks and minerals from mantle conditions to the Earth's surface. Below are a few brief examples of research I am currently working on or have worked on in the past.
Research Themes
cross-polarized thin section image of quartz and feldspars from the Johnson Granite Porphyry in Yosemite National Park
Formation and Evolution of Igneous Systems
How are granitic and volcanic rocks related? Under what conditions do igneous rocks crystallize?
Minerals record the thermal, barometric, and chemical histories of the systems from which they crystallize. These histories are recorded in chemical zoning in individual crystals in granitic and volcanic rocks. One of my primary research interests is to develop and apply novel techniques to extract useful information from this zoning.
RGB Cathodoluminescence image of quartz from the Cathedral Peak Granodiorite in Yosemite National Park
RGB CL image of the Jack Hills metaconglomerate
Secular Changes in the Crust Throughout Earth’s History
When did plate tectonics start? How have the continents co-evolved with the hydrosphere and atmosphere through time? How can signs of life be recorded in the crustal rock record?
The rock record contains records of the continental crust from 4.4 billion years ago to today. I am interested in extracting information from the chemical compositions of these ancient rocks and minerals to learn more about the evolution of the crust through time.
X-ray CT scan of the Jack Hills metaconglomerate. Bright regions are assemblages of zircon, fuchsite and magnetite. Zircons in this sample range in age from 3-4.4 Ga
view from below of a Pt capsule in a 1-atm vertical tube furnace
Developing Novel Experimentally-Constrained Geochemical Tools
Our understanding of how igneous and metamorphic rocks form is driven in large part by our ability to determine the temperatures, pressures, and chemical states (e.g., oxygen fugacity) at which they crystallize. Using experiments and observations of natural systems, I develop and modify tools (geothermometers and geobarometers) that can be used to determine the conditions at which minerals crystallize.
tridymite (dark) and rutile (bright) in a synthetic glass matrix
Latourell Falls over columnar basalt outside Portland, Oregon. A tongue-in-cheek example of water interacting with (quenched) magma.
Volatiles in Magmas
How do volatile species interact with and influence silicate melts and minerals?
The concentration and speciation of volatile elements (e.g., H2O, CO2) in magmas influence magmatic melting temperatures, eruptive styles, rheology and mineralogy. I am currently using a range of experimental and analytical (e.g., NMR, FTIR, Raman) techniques to investigate how volatiles are incorporated into melts and minerals.
H NMR spectra from synthetic rhyolite glasses with different bulk water content. I am using these spectra to determine water speciation (H2O versus OH) in rhyolite glasses.
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Experimental and Analytical Techniques
I utilize a suite of experimental equipment to synthesize rocks, minerals, glasses at conditions ranging from 25 - 1800 °C, 1 atm- 5 GPa (~50,000 atm), and controlled fO2.
Shown here is the 3-post boyd-ram piston cylinder in Bjorn Mysen's lab that was designed by Ikuo Kushiro.
I use a wide range of analytical techniques to determine the chemical and physical properties of experimental and natural samples., including: EPMA, ICPMS, Raman, FTIR, XRD, and XRF.
Pictured here is the Cameca Hyperprobe FE-EPMA at the Carnegie Institution of Washington.
Additionally, I utilized synchrotron X-ray facilities at Brookhaven National Laboratory to analyze the valence and coordination of elements in minerals and glasses.
This image is the view from above of the analytical hutch at the X26A beamline at NSLS-I (now closed) at Brookhaven National Lab