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USGS Mendenhall Postdoctoral  Research Fellowship Program

S1. Noble Gas Isotopes, Stable Isotopes, or Thermochronology Applied to Iron Oxide-Copper-Gold Deposits in the United States

The U.S. Geological Survey is about to embark on an assessment of the Nations mineral resources ( Of particular significance for assessing copper, gold, uranium, and energy critical elements (American Physical Society Panel on Public Affairs and The Materials Research Society, 2011) is the broad class of hydrothermal ore deposits commonly referred to as IOCG (iron oxide-copper-gold) deposits (Williams and others, 2005; Groves and others, 2010). IOCG deposits represent enigmatic targets for assessment because they apparently form under diverse hydrothermal environments (for example, magmatic, basinal, or metamorphic) and contain widely varying abundances of iron, copper, gold, uranium, and elements that have come to be recognized as critical for emerging energy technologies, including rare earth elements, scandium, yttrium, cobalt, silver, rhenium, and indium.  The United States has several recognized and potential IOCG districts that require a better geologic understanding so that the potential for future resource discoveries can be predicted with the highest possible confidence. 

We seek a Mendenhall Fellow to conduct research on one or more IOCG districts in the United States with the goals of identifying the sources of volatiles and metals for mineralizing fluids, determining thermal and exhumation histories, and determining the potential for undiscovered resources. We are particularly interested in candidates with experience in noble gas isotope geochemistry, light stable isotope geochemistry, or U-Th-He or K-Ar thermochronology.

Applicants are free to identify critical scientific questions the answers to which will advance the understanding of IOCG deposits within the United States. Research plans should include testable hypotheses and follow a realistic time frame. Examples of topics that could be addressed include (1) noble gas isotope compositions of fluid inclusions to determine volatile sources; (2) light stable isotope geochemistry of hydrothermal mineral assemblages as a constraint on thermal history and indicator of the source and history of water, carbon, and sulfur in ore-forming fluids; (3) thermochronology of IOCG deposits as determined by noble gas diffusion experiments to elucidate heating and burial/exhumation histories; (4) halogen contents of fluid inclusions by nuclear irradiation and measurement of daughter noble gas isotopes; and (5) broader genetic aspects, including the relation of IOCG districts to the geodynamic evolution of North America.


American Physical Society Panel on Public Affairs and The Materials Research Society, 2011, Energy critical elements—Developing new technologies to foster U.S. energy independence: Washington D.C., American Physical Society, 24 p.

Williams, P.J., Barton, M.D., Johnson, D.A., Fontbote, L., de Haller, A., Mark, G., Oliver, N.H.S., and Marschik, R., 2005, Iron oxide copper-gold deposits: Geology, space-time distribution, and possible modes of origin, in Hedenquist, J.W., Thompson, J.F.H., Goldfarb, R.J., and Richards, J.P., eds., Society of Economic Geologists 100th anniversary volume, p. 371–406.

Groves, D.I., Bierlein, F.P., Meinert, L.D., and Hitzman, M.W., 2010, Iron oxide copper-gold (IOCG) deposits through Earth history: Implications for origin, lithospheric setting, and distinction from other epigenetic iron oxide deposits: Economic Geology, vol.105, no. 3, p. 641.

Proposed Duty Station: Denver, CO

Areas of Ph.D.: Geology, isotope geochemistry, thermochronology, economic geology (candidates holding a Ph.D. in other disciplines but with knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Chemist
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisors: Craig Johnson, (303) 236-7935,; Mike Cosca, (303) 236-4974,; Al Hofstra, (303) 236-5530,; Rich Goldfarb, (303) 236-2441,, Andrew Hunt, (303) 236-4931,

Human Resources Office contact: Candace Azevedo, (916) 278-9393,

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U.S. Department of the Interior, U.S. Geological Survey
Direct inquiries to Rama K. Kotra at
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