Geological controls on the stable tellurium isotope variation in tellurides and native tellurium from epithermal and orogenic gold deposits: Application to the Emperor gold-telluride deposit, Fiji

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2019-10-01
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Fornadel, Andrew
Spry, Paul
Jackson, Simon
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Spry, Paul
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Geological and Atmospheric Sciences

The Department of Geological and Atmospheric Sciences offers majors in three areas: Geology (traditional, environmental, or hydrogeology, for work as a surveyor or in mineral exploration), Meteorology (studies in global atmosphere, weather technology, and modeling for work as a meteorologist), and Earth Sciences (interdisciplinary mixture of geology, meteorology, and other natural sciences, with option of teacher-licensure).

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The Department of Geology and Mining was founded in 1898. In 1902 its name changed to the Department of Geology. In 1965 its name changed to the Department of Earth Science. In 1977 its name changed to the Department of Earth Sciences. In 1989 its name changed to the Department of Geological and Atmospheric Sciences.

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1898-present

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  • Department of Geology and Mining (1898-1902)
  • Department of Geology (1902-1965)
  • Department of Earth Science (1965-1977)
  • Department of Earth Sciences (1977-1989)

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Abstract

Natural variability of stable Te isotope compositions in terrestrial settings, including hydrothermal ore deposits, and the geochemical conditions that control their compositions are poorly understood. Previously published Te isotope data on tellurides, sulfides, and native tellurium are limited in number and derived from samples that were geologically unconstrained with regards to their location within an ore deposit. Here, we have obtained a range of values of δ130/125Te of -0.47 ± 0.13 to 0.66 ± 0.13‰ (n = 13), relative to an in-house, gravimetrically prepared Te standard of 99.9999% Te metal, for located samples of sylvanite ((AuAg)2Te4), krennerite ((Au,Ag)Te2), and native tellurium from the alkaline igneous rock-related Emperor gold telluride deposit, Fiji. Based on similarities in the geologic setting of the alkaline-igneous rock related gold-silver telluride deposits in Colorado (Cripple Creek, Boulder County, and La Plata) with Emperor, and the narrow range of δ130/125Te values for tellurides and native tellurium from Emperor and previously published, unlocated samples from Colorado deposits (Cripple Creek, δ130/125Te = -0.53 to 0.44‰, n = 13; Boulder County, δ130/125Te = -0.25 to 0.16‰, n = 7; La Plata, δ130/125Te = -0.78 to 0.0.17‰, n = 11), it is likely that the main factor controlling the range of isotope values in these epithermal systems is the Te isotope composition of the genetically-related alkaline igneous source rocks. In comparison, previously published unlocated samples of tellurides from the giant orogenic Golden Mile Au deposit, Kalgoorlie, Australia, show an isotopic range of δ130/125Te = -1.00 to 0.51‰ (n= 6) and appear to have been more affected by the metamorphic nature of the ore fluids and/or the higher degree of water-rock interaction during hydrothermal fluid transport. It is speculated that the zonation from isotopically heavy to light Te isotopic compositions with distance from the likely causative intrusion within the Emperor deposit is primarily controlled by Rayleigh fractionation of isotopes within the ore fluid.

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This is a manuscript of an article published as Fornadel, Andrew P., Paul G. Spry, and Simon E. Jackson. "Geological controls on the stable tellurium isotope variation in tellurides and native tellurium from epithermal and orogenic gold deposits: Application to the Emperor gold-telluride deposit, Fiji." Ore Geology Reviews 113 (2019): 103076. doi:10.1016/j.oregeorev.2019.103076. Posted with permission.

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Tue Jan 01 00:00:00 UTC 2019
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