A magmatic copper and fluid source for the sediment-hosted Mount Isa deposit

Sanislav, I.V., Mathur, R., Rea, P., Dirks, P.H.G.M., Mahan, B., Godfrey, L., and Degeling, H. (2023) A magmatic copper and fluid source for the sediment-hosted Mount Isa deposit. Geochemical Perspectives Letters, 27. pp. 26-31.

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Abstract

The world class Mount Isa deposit is a unique, sediment-hosted, copper deposit with no known equivalent around the world and a controversial origin. We report δ65Cu values (n = 90) from chalcopyrite grains collected systematically across the entire deposit. The δ65Cu shows a unimodal distribution with limited variability (min = −0.87 ‰; max = 0.88 ‰) and an average value (+0.13 ‰) comparable to average igneous rocks. In general, the δ65Cu values in chalcopyrite are lower near major structures and heavier further away, consistent with equilibrium fractionation with distance from the fluid source. The range in δ65Cu of chalcopyrite from the Mount Isa deposit is less variable compared to sedimentary copper, VMS and porphyry/epithermal deposits, but similar to Michigan deposits; meanwhile, average δ65Cu at Mt. Isa is distinctly higher than sedimentary copper deposits, but similar to VMS, porphyry/epithermal and Michigan deposits. These data suggest that, from a copper isotope perspective, the Mount Isa deposit is clearly different from sedimentary copper deposits and more like VMS, porphyry copper/epithermal and Michigan style deposits. The average δ65Cu (+0.13 ‰) is almost identical to the average δ65Cu (+0.14 ‰) from Proterozoic basalts and suggests that copper was sourced from the underlying mafic rocks; the limited fractionation and the normal distribution of the δ65Cu indicate a very effective leaching mechanism and transport by a hot fluid from which chalcopyrite precipitated without significant fractionation of copper isotopes.

Item ID: 80569
Item Type: Article (Research - C1)
ISSN: 2410-3403
Copyright Information: © 2023 The Authors. This work is distributed under the Creative Commons Attribution NonCommercial No-Derivatives 4.0 License, which permits unrestricted distribution provided the original author and source are credited. The material may not be adapted (remixed, transformed or built upon) or used for commercial purposes without written permission from the author. Additional information is available at https://www.geochemicalperspectivesletters.org/copyright-and-permissions.
Date Deposited: 25 Sep 2023 23:33
FoR Codes: 37 EARTH SCIENCES > 3703 Geochemistry > 370303 Isotope geochemistry @ 30%
37 EARTH SCIENCES > 3703 Geochemistry > 370301 Exploration geochemistry @ 30%
37 EARTH SCIENCES > 3705 Geology > 370508 Resource geoscience @ 40%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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