Sodic(-calcic) alteration in Fe-oxide-Cu-Au districts: an origin via unmixing of magmatic H 2 O-CO 2 -NaCl ± CaCl 2 -KCl fluids

Pollard, P. J.

doi:10.1007/s001260050289

Cited by 119 publications

(44 citation statements)

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“…Alternatively, a number of investigators suggest that the alteration and ore minerals in IOCG systems have a magmatic, or dominantly magmatic source, derived from calc-alkaline to moderately alkaline suites similar to the ones responsible for Cu-Au porphyry deposits (Pollard, 2000(Pollard, , 2006Mumin et al, 2010;Richards and Mumin, 2013a,b). Pollard (2001) further suggests that high levels of CO 2 promote the separation of ore fluids from the crystallizing magma at a wide range of pressures that are compatible with the depths inferred for these systems. Furthermore, CO 2 may also influence the Ca-Na partitioning between silicate melts and fluids, potentially generating brines with high Na/K ratios that might be responsible for the widespread sodic alteration present in many IOCG settings.…”

Section: Iocg and Ioa Depositsmentioning

confidence: 56%

A Paleoproterozoic Andean-type iron oxide copper-gold environment, the Great Bear magmatic zone, Northwest Canada

Ootes

Snyder

Davis

et al. 2017

Ore Geology Reviews

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Iron oxide copper-gold (IOCG) and associated iron-oxide apatite (IOA) styles of metallic mineralization are recognized throughout the Paleoproterozoic Great Bear magmatic zone of the northwest Canadian Shield. The Great Bear magmatic zone was constructed between ca. 1876 and 1855 Ma on top of the older Hottah terrane, which preserves continental arc magmatism that began around ca. 2.0 to 1.97 Ga and continued between ca. 1.93 and 1.89 Ga. The Great Bear represents the final stages of ca. 150 million years of intermittent and pulsed magmatism related to an evolving continental orogenic belt. The preserved geology supports a dramatic geodynamic change in the subduction zone process at ca. 1875 Ma, a key driving mechanism for magma and metal mobilization, and was rapidly followed by a large-scale introduction of felsic-intermediate plutons. The overall tectonic setting is partially constrained from new and previously published geochemical data that show that the volcanic and plutonic rocks are high-K calc-alkaline to shoshonitic in nature (e.g., high K 2 O, Th/Yb, and Ce/P 2 0 5 ). They also have suprasubduction-zone geochemical signatures, including primitive mantle normalized positive Th and negative Nb, P, and Ti anomalies. The data support the primary melts were derived from a GLOSS-modified mantle wedge. Three-dimensional rendering of geophysical datasets suggest that two (of four) preserved surfaces within the upper mantle lithosphere, at 70 to 120 km depths, represent frozen, subducted oceanic slabs, and likely were the drivers for the bulk of Hottah and Great Bear arc magmatism. The older slab is northwest-striking and dips 12⁰ to 15⁰ northeast, whereas the younger is deeper and north-striking, dipping 13⁰ east. The geometry of the surfaces are comparable with 4D modeling, where a subduction zone is temporarily shut down due to plateau collision, and then steps oceanward and re-initiates; there is no need for polarity reversal of the subduction system. This new geometry and the related inferences about process should be the focus of future research in the region, but for the time-being it can be stated that these subduction and collisional processes were the first order control on lithospheric evolution, and therefore metallic mineralization. Overall, the Great Bear magmatic zone IOCG and related mineralization is not comparable to other Proterozoic IOCG belts, such as those in Australia. However, the complexity of mineralization styles, the spatial-temporal relationship between IOA and IOCG mineralization, the suprasubduction zone environment, and a major change in tectonic regime are features similar to Andean-type IOCG mineralization, as well as Cordilleran alkali porphyry Cu-A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT3 Au deposits. This further establishes the linkages between subduction zone processes and IOCG formation, as well as relationships in the IOCG-porphyry deposit continuum model.

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Section: Iocg and Ioa Depositsmentioning

confidence: 56%

A Paleoproterozoic Andean-type iron oxide copper-gold environment, the Great Bear magmatic zone, Northwest Canada

Ootes

Snyder

Davis

et al. 2017

Ore Geology Reviews

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“…The origin of the mineralizing fluids in Fe oxideCu-Au deposits is controversial, and hydrothermal models for this deposit type propose magmatic (Rotherham et al, 1998;Mark et al, 2000;Pollard, 2001;Williams and Skirrow, 2000), and/or nonmagmatic sources (Haynes et al, 1995;Johnson, 1996, 2000;Haynes, 2000) for the origin of the ligand-forming complexes and metals. This controversy is in part due to the temporal (and commonly spatial) association between intrusive activity and fluids that produced Cu-Au mineralisation and the surrounding regional alteration (Hitzman et al, 1992;Barton and Johnson, 1996;Oliver et al, 2004).…”

Section: Introductionmentioning

confidence: 96%

“…However, our understanding of the relations of Fe oxide mineralization to the genesis and evolution of regional hydrothermal systems, magmatism, and tectonism has become more complicated and controversial (cf. Barton and Johnson, 1996;Rotherham et al, 1998;Hitzman, 2000;Mark et al, 2000;Pollard, 2001;Williams et al, 2001;Baker et al, 2001;Marschik and Fontboté, 2001;Skirrow and Walshe, 2002). Most of the ore systems in question are hosted within terranes of Precambrian age (Cloncurry district, Gawler Craton, Curnamona Province, and Tennant Creek district, Australia; SE Missouri, USA; Norrbotten, Sweden; Wernecke Mountains and Great Bear Batholith, Canada), although the deposits formed in the Precambrian predominate (cf.…”

Section: Introductionmentioning

confidence: 96%

Modeling outflow from the Ernest Henry Fe oxide Cu–Au deposit: implications for ore genesis and exploration

Mark

Wilde

Oliver

et al. 2005

Journal of Geochemical Exploration

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“…Furthermore, scapolite phenocrysts are widespread in the dolomitic Huang et al (2013) marble of the Zhongtiao Group and scapolite-biotite schist occurs at the bottom of the Bizigou Formation (Sun and Hu, 1993;Sun et al, 1995). The occurrence of scapolite is usually believed to be closely associated with the migration of high salinity fluids (Oliver et al, 1994;Pollard, 2001;Moore, 2010). This indicates that the carbonate rocks of the Bizigou Formation may have been affected by chlorine-rich fluids in the early stages of formation.…”

Section: Carbon and Oxygen Isotopesmentioning

confidence: 99%

Fluid evolution of the Paleoproterozoic Hujiayu copper deposit in the Zhongtiaoshan region: Evidence from fluid inclusions and carbon–oxygen isotopes

Jiang

Niu

Bao

et al. 2014

Precambrian Research

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Sodic(-calcic) alteration in Fe-oxide-Cu-Au districts: an origin via unmixing of magmatic H 2 O-CO 2 -NaCl ± CaCl 2 -KCl fluids

Cited by 119 publications

References 0 publications

A Paleoproterozoic Andean-type iron oxide copper-gold environment, the Great Bear magmatic zone, Northwest Canada

A Paleoproterozoic Andean-type iron oxide copper-gold environment, the Great Bear magmatic zone, Northwest Canada

Modeling outflow from the Ernest Henry Fe oxide Cu–Au deposit: implications for ore genesis and exploration

Fluid evolution of the Paleoproterozoic Hujiayu copper deposit in the Zhongtiaoshan region: Evidence from fluid inclusions and carbon–oxygen isotopes

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