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Fluid inclusion and stable isotope constraints on the origin of Wernecke Breccia and associated iron oxide-copper-gold mineralization, Yukon


Hunt, JA and Baker, T and Cleverley, J and Davidson, GJ and Fallick, AE and Thorkelson, DJ, Fluid inclusion and stable isotope constraints on the origin of Wernecke Breccia and associated iron oxide-copper-gold mineralization, Yukon, Canadian Journal of Earth Sciences, 48, (10) pp. 1425-1445. ISSN 0008-4077 (2011) [Refereed Article]

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Copyright Statement

Copyright 2011 NRC Research Press

DOI: doi:10.1139/E11-044


Iron oxide – Cu ± Au ± U ± Co (IOCG) mineralization is associated with numerous Proterozoic breccia bodies, collectively known as Wernecke Breccia, in Yukon Territory, Canada. Multiphase breccia zones occur in areas underlain by Paleoproterozoic Wernecke Supergroup metasedimentary rocks and are associated with widespread sodic, potassic, and carbonate alteration assemblages. Fluid inclusion data indicate syn-breccia fluids were hot (185–350 °C) saline (24–42 wt.% NaCl equivalent) NaCl–CaCl2–H2O brines. Estimates of fluid pressure vary from 0.4 to 2.4 kbar (1 kbar = 100 MPa). Carbon and oxygen isotopic compositions of breccia-related carbonates range from ~–11‰ to +1.5‰ (Pee Dee belemnite (PDB)) and –2‰ to 20‰ (Vienna standard mean ocean water (V-SMOW); d18Owater ~–8‰ to +15‰), respectively. d13C and d18O values for host Wernecke Supergroup limestone/dolostone vary from ~–2‰ to 1.6‰ and 12‰ to 25‰, respectively. Sulfur isotopic compositions of hydrothermal sulfides and sulfate vary from ~–12‰ to +13‰ and +8‰to +17‰ (Caρon Diablo Troilite (CDT)), respectively. Syn-breccia biotite, muscovite, and actinolite have dD and d18O values of ~–141‰ to –18‰and +7‰ to +12‰ (V-SMOW; d18Owater ~7‰to 11‰), respectively. The Wernecke Breccias and the associated IOCG mineralization appear to have formed from largely nonmagmatic fluids — based on isotopic, fluid inclusion, and geological data. The emerging hypothesis is that periodic overpressuring of dominantly formational/metamorphic water led to repeated brecciation and mineral precipitation. The weight of overlying sedimentary rocks led to elevated fluid temperatures and pressures; fluid flow may have been driven by tectonics and (or) gravity with metals scavenged from host strata.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Resource geoscience
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Other mineral resources (excl. energy resources)
Objective Field:Other mineral resources (excl. energy resources) not elsewhere classified
UTAS Author:Davidson, GJ (Dr Garry Davidson)
ID Code:77841
Year Published:2011
Web of Science® Times Cited:11
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2012-06-01
Last Modified:2012-08-30

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