School of Earth, Energy and Environmental Sciences
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Professor of Geological Sciences
Current Research and Scholarly InterestsMy research focuses on the exploration & exploitation of geological resources, from data acquisition to decision making under uncertainty and risk assessment.
Victoria and Roger Sant Director, Earth Systems Program, Associate Professor of Earth System Science and Senior Fellow at the Woods Institute for the Environment
Current Research and Scholarly InterestsAssistant Professor in EESS, focus on marine chemistry and biogeochemistry.
Professor of Geological Sciences
Current Research and Scholarly InterestsResearch
I use stable and radiogenic isotopes to understand Earth system history. These studies examine the link between climate, tectonics, biological, and surface processes. Projects include: 1) examining the terrestrial climate history of the Earth focusing on periods of time in the past that had CO 2-levels similar to the present and to future projections; and 2) addressing how the chemical weathering of the Earth's crust affects both the long- and short-term carbon cycle. Field areas for these studies are in the Cascades, Rocky Mountains, Sierra Nevada, the European Alps, Tibet and the Himalaya and the Southern Alps of New Zealand.
Much of the research that I do has an international component. Specifically, I have collaborations with: 1) the Senckenberg Biodiversity and Climate Research Center in Frankfurt Germany as a Humboldt Fellow and 2) the Chinese University of Geosciences in Bejiing China where I collaborate with Professor Yuan Gao.
I teach courses at the undergraduate and graduate level in isotope biogeochemistry, Earth system history, and the relationship between climate, surface processes and tectonics.
Editor American Journal of Science; Co-Director Stanford Stable Isotope Biogeochemistry Laboratory (present);Chair, Department of Geological and Environmental Sciences (2004-07); Co-Director Stanford/USGS SHRIMP Ion microprobe facility (2001-04)
Cecil H. and Ida M. Green Professor of Geophysics, Emeritus
Current Research and Scholarly InterestsReflection Seismology
Phys Sci Res Assoc, Geological Sciences
BioFrom 2012 until 2019, I co-managed the SHRIMP-RG ion-microprobe at Stanford University. I oversaw operation of the laboratories and work closely with Stanford scientists, students, and visiting scientists to undertake measurements on the SHRIMP-RG. This includes training users in SIMS methods, assisting with sample preparation/characterization, data acquisition, reduction, interpretation, and publication of results. I also contribute to the development and refinement of new techniques and standard development efforts on the SHRIMP-RG.
My research focuses on understanding the timescales of magmatic processes and the sources of crystal diversity in magmatic systems. To accomplish this, I use radiometric dating (238U-230Th, 238U-206Pb, 40Ar-39Ar, and U-Th/He) and chemical analysis of minerals to investigate the temporal and compositional history of magmas. I integrate these results to better understand how magmas evolved in the crust leading up to eruption, and the geology of these deposits exposed on Earth’s surface today. The methods I utilize involve electron microprobe (EMP), secondary ion mass spectrometry (SIMS), nanoSIMS, and inductively coupled plasma mass spectrometry (ICP-MS).
One of the exciting and challenging components of my research is finding analytical techniques to answer complicated petrogenetic questions. To do this, one of the main tools I employ is the high spatial resolution of SIMS in order to measure trace elements and isotopic ages simultaneously, often in-situ, from the same analyte volume (~4 ng). Additionally, using the relatively slow sputter rate of the SIMS method (10’s of nm/min), I have applied this approach to depth profiling into fresh, unpolished mineral surfaces to target the last phase of mineral growth. This have been extremely useful for dating zircons with complicated histories. For example, I have been working on radiometrically dating geologically young volcanic zircons (Quaternary in age) where the outermost micron of grain yields crystallization ages that agree with Ar-Ar and U-Th/He eruption ages, whereas the interiors contain older inherited portions of the grains. Another example is applying this technique to dating thing (<2 micron) metaphoric rims surround an older protolith core, which would be impossible to analyze using traditional techniques of polishing zircon to expose the interiors of the grains.
Please visit https://shrimprg.stanford.edu/ for more information about the SHRIMP-RG and SIMS.
I have recently moved to Wellington, New Zealand. However, I remain actively involved in numerous on-gong projects at Stanford University and in the SHRIMP- RG lab as a consulting scientist. Please contact me using my stanford.edu or gmail accounts if you have question about previous or ongoing research projects.