School of Earth, Energy & Environmental Sciences
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Professor (Research) of Geological and Environmental Sciences, Emeritus
Current Research and Scholarly InterestsFormation, geometric patterns and fluid flow properties of fractures and faults in a broad range of scales.
Professor of Geological Sciences, Emeritus
Current Research and Scholarly InterestsTheoretical geochemistry of reactions among aqueous solutions and minerals in magma-hydrothermal systems; environmental geochemistry of toxic metals in the Mother Lode Gold region, CA, and the emergence of life in the aftermath of the Moon-forming impact, ca. 4.4Ga.
Associate Professor of Geological Sciences
Current Research and Scholarly InterestsPaleontology; Evolution of plant physiology & development; Geochemistry of fossil preservation; Evolution of terrestrial ecosystems and environments
Dorrell William Kirby Professor of Geology in the School of Earth Sciences, Emeritus
Current Research and Scholarly InterestsSurface and interface geochemistry; environmental fate of heavy metals; nanotechnology, applications of synchrotron radiation in geochemistry and mineralogy
Phys Sci Res Assoc, Geological Sciences
BioI manage the Stanford Mineral and Microchemical Analysis Facility. My primary responsibilities include developing and testing procedures for measuring major and trace element concentrations in a variety of solid materials, working with Stanford researchers (and external users) to design experiments and collect, interpret, and publish data, and overseeing the long-term development and trajectory of the Mineral and Microchemical Analysis Facility both within the Stanford School of Earth, Energy, and Environmental Sciences and in the greater Stanford community.
Professor of Geological Sciences
Current Research and Scholarly InterestsMy research interest are varied, but a constant is the practical application of data science to address geological science questions as well as other areas of the Earth Sciences. My recent focus involves including physics into stochastic modeling and assessing uncertainty for decision making in geo-engineering applications.
Phys Sci Res Assoc, Geological Sciences
BioI co-manage the SHRIMP-RG ion-microprobe at Stanford University, where I oversee operation of the laboratories and work closely with Stanford scientists and students as well as 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.
I am always interested in new dating and trace element applications, analytical approaches, or methodology that can utilize the high-spatial resolution and high mass-resolution of the SHRIMP-RG. Please contact me if you are interested in new method development ideas to tackle specific Earth science questions.
Please visit https://shrimprg.stanford.edu/ for more information about the SHRIMP-RG and SIMS.