Research | Geochemistry
Geochemistry
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
Jonathan
Patchett – Crustal evolution, sedimentation, radiogenic isotopes
Jay
Quade – Soils, tectonics, radiogenic and stable isotopes
Joaquin
Ruiz – Tectonics, ore deposits, radiogenic isotopes
Joellen
Russell - Biogeochemistry, oceanography, climate dynamics and 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 – four 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.
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