Intellectual Merit: The goal of this project is to determine the stable tellurium isotope systematics of tellurium-bearing minerals, primarily in the system Au-Ag-Te (in epithermal and orogenic gold deposits), to determine the source of tellurium in these precious metal deposits (and possibly associated gold and silver), processes associated with isotope fractionation, geochemical information related to the origin of the deposits, and a better understanding of the chemistry of tellurium, in general. A question that will also be addressed is: can stable tellurium isotopes be used in mineral exploration and vectoring new ore bodies in an existing mining camp in a way that has been previously done with other stable isotopes (e.g., oxygen and copper)? The aims of the project will be achieved by analyzing the stable tellurium isotopes of tellurides, native tellurium, tellurates and tellurites, which will be sampled, and for some deposits have already been collected, from various orogenic and epithermal gold (e.g., Golden Sunlight and Mayflower, Montana; Emperor and Tuvatu, Fiji; Kensington, Alaska; Golden Mile, Western Australia), using both in situ and solution methods with a multi collector-inductively coupled plasma-mass spectrometer (MC-ICPMS) system. The study will specifically evaluate: 1. Mechanisms that produce mass-dependent isotope fractionation including, biotic or abiotic processes (e.g., redox behavior), liquid-vapor separation (since tellurium is transported in both the liquid and vapor phases), kinetics, deposition and transportation processes. The possibility that isotopes are fractionated by mass-independent processes will also be considered; 2. Potential sources of tellurium in ore deposits and what can be learned about gold speciation I deposits, since most of the minerals analyzed will be members of the system Au-Ag-Te (calaverite, krennerite, sylvanite, hessite, petzite, stützite, empressite, muthmannite); and 3. Differences between isotope compositions determined by theoretical calculations, using vibrational spectra and force-field models, and those determined from independent geothermometers from terrestrial samples.
Broader Impacts: In addition to collecting fundamental data on the systematics of stable tellurium isotopes in and the origin of hydrothermal gold deposits, information will also be obtained on the basic chemistry of this element. Tellurium, has a wide variety of uses (ceramics, glass fiber, vulcanized rubber, electronics industry), but it is used primarily in industry to form copper, lead, and iron alloys and more machinable stainless steel. Tellurium is also used in cadmium telluride (CdTe) in solar panels and research is underway to investigate whether (Cd,Zn)Te can be used as an alternate. Its use in solar panels is critical to the thrust on alternative sources of energy in the United States, and elsewhere. The project will also enhance infrastructure for research education by involving collaborations among personnel in government agencies (United States Geological Survey, Geological Survey of Canada) and academia (Iowa State University, University of California - Los Angeles). It will also provide multidisciplinary research opportunities for two Ph.D. students and an undergraduate student who are interested in developing careers in the government, minerals industry, and academia.
