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Origin of sulfur and crustal recycling of copper in polymetallic (Cu-Au-Co-Bi-U ± Ag) iron-oxide-dominated systems of the Great Bear Magmatic Zone, NWT, Canada

Acosta-Góngora, P., Gleeson, S. A., Samson, I. M., Corriveau, L., Ootes, L., Jackson, S. E., Taylor, B. E., Girard, I. (2017 online): Origin of sulfur and crustal recycling of copper in polymetallic (Cu-Au-Co-Bi-U ± Ag) iron-oxide-dominated systems of the Great Bear Magmatic Zone, NWT, Canada. - Mineralium Deposita.
DOI: http://doi.org/10.1007/s00126-017-0736-6



http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:2629891
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Authors

Acosta-Góngora ,  P.

http://gfzpublic.gfz-potsdam.de/cone/persons/resource/sgleeson

Gleeson ,  S. A.
3.1 Inorganic and Isotope Geochemistry, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Samson ,  I. M.

Corriveau ,  L.

Ootes ,  L.

Jackson ,  S. E.

Taylor ,  B. E.

Girard ,  I.

Abstract
The Great Bear Magmatic Zone, in northwest Canada, contains numerous polymetallic mineral occurrences, prospects, and deposits of the iron oxide copper-gold deposit (IOCG) family. The mineralization is hosted by the Treasure Lake Group and igneous rocks of the Great Bear arc and was deposited concomitantly with the arc magmatism (ca. 1.88 to 1.87 Ga). In situ δ34S (n = 48) and δ65Cu (n = 79) analyses were carried out on ore-related sulfides from a number of these systems. The δ34S values mainly vary between 0 and +5‰, consistent with derivation of sulfur from the mantle. Lower δ34S values (−7.7 to +1.4‰) from the Sue-Dianne breccia may indicate SO2 disproportionation of a magmatic hydrothermal fluid. The δ65Cu values vary between −1.2 and −0.3‰, and are lower than the igneous δ65Cu range of values (0.0 ± 0.27‰). The S and Cu isotopic data are decoupled, which suggests that Cu (and possibly some S) was dissolved and remobilized from supracrustal rocks during early stages of alteration (e.g., sodic alteration) and then precipitated by lower temperature, more oxidizing fluids (e.g., Ca-Fe-K alteration). A limited fluid inclusion dataset and δ13C and δ18O values are also presented. The δ18Ofluid values are consistent with a magmatic origin or a host-rock equilibrated meteoric water source, whereas the δ13Cfluid values support a marine carbonate source. Combined, the S and Cu isotopic data indicate that while the emplacement of the Great Bear magmatic bodies may have driven fluid convection and may be the source of fluids and sulfur, metals such as Cu could have been recycled from crustal sources.