The Geology department at UC Davis offers interdisciplinary curricula in geochemistry, leading to the Master of Science and Doctor of Philosophy degrees. Tools involve the use of stable isotope and trace element mass spectrometry to address problems in aqueous, marine and environmental geochemistry, and studies applied to sedimentary, metamorphic and igneous systems. Our students are encouraged to design individual academic programs involving both empirical and theoretical approaches. Opportunities exist for students to participate in international field research programs on land and throughout the ocean basins.

The department has outstanding facilities to support geochemical research. In house light stable isotope ratio mass spectrometers (IRMS) include Fisons Optima and Finnigan MAT 251 mass spectrometers with automated capabilities for analyzing carbon and oxygen isotope ratios on very small carbonate samples, carbon and nitrogen isotope ratios on organic matter, and oxygen and hydrogen isotope ratios on waters. A third continuous flow IsoPrime IRMS is available for sulfur, carbon and nitrogen isotope analyses. Off line isotopic separation facilities include vacuum lines for carbonates, organic carbon, SCO₂ in water, hydrogen and oxygen in silicates, and sulfur in sulfides and sulfates. Additional departmental equipment includes: a cathodoluminescence microscope, an epi-fluorescence reflected light microscope, and petrographic microscopes; cooled CCD camera with video and digital image capture systems for use with the microscopes; and a pH-stat system for mineral precipitation/dissolution experiments at constant pH. The department also houses a fully automated CAMECA electron microprobe and the UC Davis campus has recently been funded to purchase a state of the art multicollector ICP-MS for trace element and radiogenic isotope measurements.

Kari Cooper (Ph.D., UCLA, 2001): Isotope geochemistry of volcanic rocks; dynamics of magma reservoir systems including magma storage, crystallization/differentiation, and interaction with wallrocks, with emphasis on crystal ages from uranium-series disequilibria measured in minerals and coexisting liquids; origin and distribution of chemical heterogeneity in the mantle with emphasis on stable-isotope tracers of recycled crustal material, including oxygen isotope variations in fresh MORB and lithium isotopic composition of altered oceanic crust. Current and recent projects include timing of magma mixing and assimilation of wallrocks beneath Icelandic volcanoes; magma storage and differentiation timescales at Mount St Helens; crystal and magma residence times at Kilauea and Mauna Loa, Hawaii; oxygen-isotope records of crustal recycling in the upper mantle beneath the Mid-Atlantic Ridge and the Australian-Antarctic Discordance; timescales and mechanisms of hydrothermal alteration of oceanic crust using U-series disequilibria and lithium isotopic composition.

Tessa Hill (Ph.D., University of California, Santa Barbara, 2004): Research focuses on the geochemistry of microfossils and corals (including d¹⁸O, d¹³C, d¹⁵N, trace elements, radiocarbon) to determine rates and magnitude of climate change and forcing mechanisms behind recent (Quaternary) climate change. Recent studies have been on geochemical evidence for gas hydrate dissociation and the penetration of rapid warming to the ocean’s interior.

Charles Lesher (Ph.D., Harvard, 1985): Experimental igneous petrology and geochemistry; phase equilibria and kinetics of silicate systems at elevated pressure and temperature; physical, transport and thermodynamic properties of silicate melts. Recent projects include (a) Laboratory: low to high pressure phase equilibria studies of basaltic systems; trace element partitioning; chemical and self diffusion studies of silicate melts; solution properties of silicate liquids from thermal diffusion. (b) Field: magmatic evolution of the North Atlantic Ocean basin and the evolution of the Iceland hot spot; petrologic studies of early Tertiary volcanic and plutonic rocks of East Greenland.

Isabel Montañez (Ph.D., Virginia Polytechnic Institute, 1990): Research interests are in the sedimentary record of coupled physical and chemical variation in paleo-oceans, global biogeochemical cycling in marine and terrestrial records, and carbonate fluid-rock interaction in sedimentary basins using stratigraphy, petrography and geochemistry, including stable and radiogenic isotopes and trace elements.

James Rustad (Ph.D., Minnesota, 1992): Interfacial and mineral surface geochemistry; mineralogy; mineral physics. Research is focused on computational chemical models of interfacial structure as well as surface charging, sorption, dissolution, and precipitation phenomena at oxide-water interfaces. Computational methods are also applied to problems in mineralogy and in aqueous and silicate melt geochemistry, including physics of hydrated minerals, ligand exchange and electron transfer reactions. Current projects include large-scale molecular dynamics modeling of surface charging, aggregation, and electron transfer reactions on colloidal iron oxide particles, and multiscale description of mineral surfaces.

Peter Schiffman (Ph.D., Stanford, 1978): Metamorphic petrology and clay mineralogy of active and fossil hydrothermal systems in terrestrial and submarine settings; weathering, palagonitization, and biomineralization of basalt glass; mineralogy of equine enteroliths and urinary calculi in dogs, cats, and horses. Recent projects include studies in Hawaii, Iceland, and the intestinal and urinary tracts of felines, canines, and equines.

Howard Spero (Ph.D., UC Santa Barbara, 1986): Research focuses on the biological and environmental parameters that affect the stable isotope and trace metal geochemistry of the shells of recent and fossil organisms; marine micropaleontology, paleoclimatology, and paleoceanography. An ongoing multi-year field research program involving graduate and undergraduate students has been studying living planktonic foraminifera in the Southern California Borderland and the Caribbean. The results of this study are being used to interpret fossil foraminifera stable isotope data from Indian and Atlantic Ocean deep sea cores in order to reconstruct paleoenvironmental sea surface temperatures, nutrient levels and CO₂ concentrations during the Pleistocene.

Dawn Sumner (Ph.D., Massachusetts Institute of Technology, 1995): Research uses stratigraphic, petrographic, and low temperature geochemical techniques to address the biological and abiotic controls on carbonate precipitation with the intent to understand ancient ocean chemistry and the interactions between microbial communities and their environment. Please see http://www.geology.ucdavis.edu/~sumner/ for ongoing projects.

Qing-zhu Yin (Ph.D., Max-Planck-Institute for Chemistry, 1995): Using extinct radioactivity and general isotopic anomalies in the early solar system recorded in primitive meteorites as a tool to study the time scales and site of nucleosynthesis, the time of formation of the solar system and planetary differentiation. Isotope and trace element geochemistry with applications to crust-mantle evolution. Heavy metal stable isotope fractionation in low temperature environments on planetary surfaces or in biological systems using newly emerging high precision mass spectrometry techniques. The development of associated experimental techniques involving high precision mass spectrometry and ultra-clean sample processing in Class-100 clean laboratories for isotope analyses.

Robert Zierenberg (Ph.D., Wisconsin, 1983): Aqueous geochemistry; stable isotope geochemistry; economic geology. Research has focused on water/rock interaction in active and ancient hydrothermal systems, including the "black smokers" on the mid-ocean ridges. Recent work includes investigation of seafloor hydrothermal systems on sediment-covered portions of the northern Juan de Fuca Ridge and southern Gorda Ridge during Leg 169 of the Ocean Drilling Program. Ancient analogs of seafloor hydrothermal systems investigated include the Turner-Albright massive sulfide deposit in the Josephine Ophiolite, OR, and the Red Dog Pb-Zn-Ag deposit in the Brooks Range, AK. Other interests include the environmental effects of mining, particularly the generation of acid mine drainage, mercury contamination in Clear Lake related to the abandoned Sulphur Bank Hg mine, and the geochemical and biological cycling of sulfur.

Charles Alpers (Ph.D., U.C. Berkeley, 1986): Research Associate. Environmental geochemistry of mineral deposits; mercury contamination and bioaccumulation associated with historical mining; trace metals and colloid transport in surface waters; acid mine drainage; efflorescent sulfate minerals;application of stable and radiogenic isotopes to environmental problems.

Gry Barfod (Ph.D. University of Copenhagen, 2002): Geochronology and isotope geochemistry. Calibration of Precambrian and Cambrian stratigraphical time-scale by radiometric dating of sediment/fossils, rate of geological processes in metamorphic terranes, closure temperature for metamorphic apatite, geochronology and geochemistry of igneous rocks, technique development of separation methods for elements from geological materials.

William Casey (Ph.D., Penn State): Professor. Aqueous geochemistry. Thermodynamics of aqueous solutions; mineral-fluid surface chemistry; surface spectroscopy; diagenesis; kinetics of ligand-exchange reactions; degradation pathways of toxicants; field geochemistry.

Maria Mange (Ph.D, Lorand Eotvos, Budapest, Hungary, 1975): Associate Research Geologist. Sedimentary mineralogy and petrography, heavy mineral geochemistry, heavy mineral and tectono-stratigraphy. High-resolution heavy mineral analysis applied to sedimentary sequences to determine provenance, map the temporal and spatial evolution of ancient dispersal systems and to reconstruct the evolution and unroofing phases of orogenic regimes.

Alexandra Navrotsky (Ph.D., University of Chicago, 1967): Professor. Research interests have centered about relating microscopic features of structure and bonding to macroscopic thermodynamic behavior in minerals, ceramics, and other complex materials. She has made contributions to mineral thermodynamics; mantle mineralogy and high pressure phase transitions; silicate melt and glass thermodynamics; order-disorder in spinels; framework silicates; and other oxides; ceramic processing; oxide superconductors; and the general problem of structure-energy-property systematics. The main technical area of her laboratory is high temperature reaction calorimetry.

Ann Russell (Ph.D., University of Washington, 1994): Assistant Research Oceanographer. Paleoceanography and chemical oceanography. Research focuses on development and application of geochemical tracers of changes in ocean chemistry, including metals and stable isotopes in foraminiferal shells, and redox-sensitive metals in bulk sediments. She uses these geochemical tracers to reconstruct changes in ocean temperature, carbon chemistry, and redox environment from deep-sea sediment cores.

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