Research | Geochemistry

Cracked-mud creek bed winding through terrain with mountains in backgroundGeochemistry has evolved from a science practiced by a few specialists to a very broad area that contributes to more than half of all research in Earth Sciences. The Geosciences Department at the University of Arizona employs a large number of geochemical techniques that are applied to problems ranging from Archean and Proterozoic crustal evolution, all the way through to Holocene climate, and from whole Earth to micron scales.

Faculty

Mark Barton – Ore deposits, stable isotopes
Julia Cole – Climate, environmental change, stable isotopes
Mihai Ducea – Tectonics, radiogenic isotopes
Timothy Jull – AMS of radiocarbon and other cosmogenic isotopes
Jay Quade – Soils, tectonics, radiogenic and stable isotopes
Joaquin Ruiz – Tectonics, ore deposits, radiogenic isotopes
Joellen Russell - Biogeochemistry, oceanography, climate dynamics and modeling
Jessica Tierney -
Geochemistry, biogeochemistry, drought, reconstruction & modeling
 

Faculty with related interests

Andy Cohen - Stratigraphy, paleobiology
Peter DeCelles - Sedimentology, tectonics
Karl Flessa - Invertebrate paleontology, paleobiology
Jibamitra Ganguly - Petrology, geochemistry
George Gehrels - Tectonics, geochronology
Jonathan Overpeck - Paleoclimatology, paleoecology, climate dynamics
Peter Reiners - Tectonics, radiogenic isotopes, and geomorphology
Eric Seedorff - Economic geology
Spencer Titley - Mineral deposits, regional geology
George Zandt - Geophysics, tectonics

Researchers

Mark Baker – Radiogenic isotopes
Warren Beck – Paleoclimate and climate change
John Chesley – Radiogenic isotopes
David Dettman – Stable isotopes
Chris Eastoe - Stable isotopes

Clark Isachsen - Thermo/geochronology
Nathaniel Lifton – Cosmogenic isotopes

Facilities, Equipment, and Resources

The Department operates 12, soon to be 13 mass spectrometers, which analyze elements from hydrogen to uranium. This large concentration reflects the major contribution that Geochemistry, particularly Isotope Geochemistry, currently makes to understanding of Earth processes. Other laboratories are Scanning Electron Microscope, micro-X-ray Fluorescence, ICP-AES, and Scintillation Counters for C-14 and Tritium. Examples of our laboratories are:

  • Accelerator Mass Spectrometer facility – shared with the Dept. of Physics, under the direction of Timothy Jull. The laboratory produces carbon-14 ages in support of many of the Department’s projects, and also analyzes cosmogenic isotopes.

  • Biogeochemical Dynamics Laboratory - uses (and, when possible, collects) in situ and remote measurements of the ocean, atmosphere, terrestrial biosphere and paleo-records to monitor, understand and predict changes in the Earth's climate system.

  • Inductively-Coupled Plasma Mass Spectrometry – an Isoprobe mass spectrometer under the direction of Ruiz, used for U-Pb dating by laser (Gehrels, Ducea), Hf isotopes (Patchett), and Cu and Fe isotopes (Ruiz).

  • Noble Gases Laboratory - Primarily devoted to 40Ar/39Ar cosmochronology (Swindle) andÊthermo/geochronology (Isachsen), the paired gas extraction line and mass spectrometer are also designed for analysis of krypton, xenon, and neon isotopes. The broad range of application of these isotopic systems range from dating primordial solar system materials in the form of meteorites to recent terrestrial volcanic rocks, and as a thermochronologic tool, the laboratory forms an integral link with the Laserchron lab (U-Pb) and the ARHDL lab (U-TH/He) to cover a wide range of closure temperatures for a comprehensive characterization of orogenic thermal histories.

  • Scanning Electron Microscope Laboratory (Ducea) – used to characterize a wide range of materials, including zircons for age analysis.

  • Stable Isotope Laboratories – six mass spectrometers that analyze O, C, H, S, and N isotopes on a range of samples from carbonates, organic matter, and waters (Cole, Dettman, Eastoe, Quade) through silicates and hydrothermal minerals (Barton). The application of stable isotopes is thus very broad, involves large numbers of analyses, and ranges from Holocene climate through hydrology to economic geology. In addition to stable isotope work, the Environmental Isotope Laboratory uses liquid scintillation spectrophotometers for measurement of 3H and 14C.

  • Thermal Ionization Mass Spectrometry – three machines in laboratories under direction of Patchett, Ruiz, Ducea, Gehrels, and Quade. They are used for Sr, Nd, Hf and Os isotopes, as well as U-Th (U-series) and U-Pb geochronology.

  • (U-Th)/He Dating Lab - Decay of uranium and thorium to helium provides a versatile chronometer for examining the timing and rates of a wide variety of events and processes in earth and planetary science. (U-Th)/He dating is often used to constrain thermal histories of rocks and the timing and rate of orogenic events and the topographic evolution. Using (U-Th)/He thermochronology in this way we work with a wide range of geomorphologists and tectonicists to address problems related to uplift, erosion, faulting, and other orogenic issues. He dating is also used in a wide range of other applications, including dating young volcanic rocks, estimating meteorite thermal histories, thermal histories of sedimentary basins, and tracing the effects of wildfire on the earth's surface. In the ARHDL we work on applications such as these all over the world, and develop new ways to do and use He dating.