The thermal and chemical evolution of hydrothermal vent fluids in shale hosted massive sulphide (SHMS) systems from the MacMillan Pass district (Yukon, Canada)

Magnall, Joseph M.; Gleeson, Sarah A.; Blamey, Nigel; Paradis, Suzanne; Luo, Yan

doi:10.1016/j.gca.2016.07.020

Cited by 36 publications

(25 citation statements)

References 83 publications

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“…(1) the depositional environment and seawater paleoredox (Magnall et al, 2015(Magnall et al, , 2018; (2) pathways of sulfate reduction during diagenesis (Magnall et al, 2016a); (3) vent fluid chemistry and base metal solubility (Magnall et al, 2016b); (4) and the paragenesis and mineralogical evolution of the layered mineralization (Magnall et al, 2020). In this contribution, we review the key aspects of these recent studies and propose a new, internally consistent subseafloor replacement model for CD-type mineralization at Macmillan Pass.…”

Section: Introductionmentioning

confidence: 99%

A NEW SUBSEAFLOOR REPLACEMENT MODEL FOR THE MACMILLAN PASS CLASTIC-DOMINANT Zn-Pb ± Ba DEPOSITS (YUKON, CANADA)

2020

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Sedimentary exhalative (SEDEX) deposits are a subset of sediment-hosted massive sulfide deposits and provide our dominant resource of Zn. In the SEDEX model, base metals (Zn, Pb, Fe) are hydrothermally vented into sulfidic (euxinic) seawater and deposited coevally with the organic-rich mudstone host rock, resulting in laterally extensive layered mineralization. In the Selwyn Basin (Canada) at Macmillan Pass, two deposits (Tom, Jason) are well preserved in a succession of Upper Devonian mudstones and are considered type-characteristic examples of the SEDEX deposit model. As with a number of SEDEX deposits, at Macmillan Pass barite is abundant in the succession hosting hydrothermal mineralization. Early work presented a hydrothermal model for barite formation, in which barite coprecipitated with base metal sulfides in a redox-stratified water column. Recently, however, studies have both proposed an alternative diagenetic model for barite formation and provided more precise constraints on the chemistry of the hydrothermal fluid that entered the vent complexes. Here, we present a new model for Macmillan Pass in which sulfide mineralization occurred entirely within the subsurface. The introduction of hot (300°C) hydrothermal fluids into the shallow subsurface (<1-km depth) resulted in the thermal degradation of organic matter and generated CO2; this promoted barite dissolution, which both provided a source of sulfate for thermochemical sulfate reduction and increased the porosity and permeability within the system. Importantly, there was clear potential for the development of positive feedbacks and self-organization between diagenetic and hydrothermal processes, resulting in highly efficient ore-forming systems. In contrast to the SEDEX model, alteration footprints will be controlled by the mass transfer involved in (barite) replacement reactions rather than hydrothermal venting, and exploration criteria at a district scale should strongly favor highly productive continental margins.

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Section: Introductionmentioning

confidence: 99%

A NEW SUBSEAFLOOR REPLACEMENT MODEL FOR THE MACMILLAN PASS CLASTIC-DOMINANT Zn-Pb ± Ba DEPOSITS (YUKON, CANADA)

2020

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“…Divalent Eu, however, is not readily incorporated into the carbonate crystal lattice, which is why positive Eu/Eu * can only develop in carbonate mineral phases that formed from hot fluids that cooled below 200-250°C in order to stabilize Eu 3+ (Bau and Möller 1992). Many hydrothermal carbonates also preserve LREE depletion relative to PAAS (e.g., Roberts et al 2009;Debruyne et al 2013;Magnall et al 2016). Such LREE-depleted REE+Y signatures in hydrothermal precipitates have been interpreted to result from co-precipitation with LREE-enriched phases (Roberts et al 2009), LREE scavenging by fluid-mineral interaction along the fluid pathway (e.g., by monazite; Debruyne et al 2016), inherited REE+Y signatures from fluid-rock interaction (Lüders et al 1993;Hecht et al 1999), or LREE retention in the fluid by Cl --complexes (Craddock et al 2010;Magnall et al 2016;Perry and Gysi 2018).…”

Section: Rare-earth Elements and Yttrium (Ree+y)mentioning

confidence: 99%

“…10a, b) are consistent with LREE-retention in such Cl --rich saline hydrothermal fluids. Furthermore, there is evidence that LREE-depletion is a common feature of carbonate mineral phases from a number of mineral deposits that formed from saline fluids (Roberts et al 2009;Debruyne et al 2013;Genna et al 2014;Magnall et al 2016), whereas LREE depletion is not evident from carbonates that precipitated from low-salinity fluids that were dominated by HS --or CO 3 2--complexes (Maskenskaya et al 2015;Vaughan et al 2016). As a consequence, LREE depletion in calcites or dolomites relative to background REE+Y profiles may be an effective tracer for fluid-rock interaction involving saline hydrothermal fluids.…”

Section: Implications For the Application Of In Situ Ree+y Carbonate Datamentioning

confidence: 99%

“…Altogether, there is potential for the REE+Y systematics of diagenetic and hydrothermal carbonates in constraining key aspects of fluid chemistry. Nevertheless, the direct application of in situ REE+Y analysis of carbonate minerals has remained relatively untested for hydrothermal mineral systems (e.g., Magnall et al 2016;Vaughan et al 2016), despite the wealth of information that is available from these types of analyses (Debruyne et al 2016;Smrzka et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Differentiating between hydrothermal and diagenetic carbonate using rare earth element and yttrium (REE+Y) geochemistry: a case study from the Paleoproterozoic George Fisher massive sulfide Zn deposit, Mount Isa, Australia

et al. 2021

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Carbonate minerals are ubiquitous in most sediment-hosted mineral deposits. These deposits can contain a variety of carbonate types with complex paragenetic relationships. When normalized to chondritic values (CN), rare-earth elements and yttrium (REE+YCN) can be used to constrain fluid chemistry and fluid-rock interaction processes in both low- and high-temperature settings. Unlike other phases (e.g., pyrite), the application of in situ laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) data to the differentiation of pre-ore and hydrothermal carbonates remains relatively untested. To assess the potential applicability of carbonate in situ REE+Y data, we combined transmitted light and cathodoluminescence (CL) petrography with LA-ICP-MS analysis of carbonate mineral phases from (1) the Proterozoic George Fisher clastic dominated (CD-type) massive sulfide deposit and from (2) correlative, barren host rock lithologies (Urquhart Shale Formation). The REE+YCN composition of pre-ore calcite suggests it formed during diagenesis from diagenetic pore fluids derived from ferruginous, anoxic seawater. Hydrothermal and hydrothermally altered calcite and dolomite from George Fisher is generally more LREE depleted than the pre-ore calcite, whole-rock REE concentrations, and shale reference values. We suggest this is the result of hydrothermal alteration by saline Cl--rich mineralizing fluids. Furthermore, the presence of both positive and negative Eu/Eu* values in calcite and dolomite indicates that the mineralizing fluids were relatively hot (>250°C) and cooled below 200–250°C during ore formation. This study confirms the hypothesis that in situ REE+Y data can be used to differentiate between pre-ore and hydrothermal carbonate and provide important constraints on the conditions of ore formation.

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“…As a result, CD‐type deposits have been sub‐divided into vent‐proximal and vent‐distal systems, with the latter considered to form after the migration of hydrothermal fluids away from the site of active venting onto the seafloor (Sangster, 2018). The fine‐grained nature of the mineralization and the paucity of vent or feeder complexes also means there are limited localities where fluid inclusions have been preserved (Magnall et al., 2016; Rajabi et al., 2014) and so the composition of ore‐forming fluids is relatively unconstrained in many systems. Nevertheless, a broad framework has been proposed, which follows the use of this limited input data for thermodynamic modeling and involves sub‐division of deposits into two groups (Cooke et al., 2000): McArthur‐type , which formed from oxidising, low‐temperature (<150°C), high‐salinity (>18 wt.% NaCl equiv.)…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Constraints on Ore Formation by Basin‐Scale Fluid Flow at Continental Margins: Modelling Zn Metallogenesis in the Devonian Selwyn Basin

Aguilar

Weis

Magnall

et al. 2021

Geochem Geophys Geosyst

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 Modelling of basin-scale fluid flow shows that tapping hot fluids from deep confined aquifers by faults can produce large Zn deposits  Heat anomaly that drives the hydrothermal system can form at magma-poor hyperextended continental margins as inferred for the Selwyn Basin  Modelled metal enrichment agrees with observations from the deposits, but the timescale is much shorter than assumed in classical models Accepted ArticleThis article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

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The thermal and chemical evolution of hydrothermal vent fluids in shale hosted massive sulphide (SHMS) systems from the MacMillan Pass district (Yukon, Canada)

Cited by 36 publications

References 83 publications

A NEW SUBSEAFLOOR REPLACEMENT MODEL FOR THE MACMILLAN PASS CLASTIC-DOMINANT Zn-Pb ± Ba DEPOSITS (YUKON, CANADA)

A NEW SUBSEAFLOOR REPLACEMENT MODEL FOR THE MACMILLAN PASS CLASTIC-DOMINANT Zn-Pb ± Ba DEPOSITS (YUKON, CANADA)

Differentiating between hydrothermal and diagenetic carbonate using rare earth element and yttrium (REE+Y) geochemistry: a case study from the Paleoproterozoic George Fisher massive sulfide Zn deposit, Mount Isa, Australia

Hydrodynamic Constraints on Ore Formation by Basin‐Scale Fluid Flow at Continental Margins: Modelling Zn Metallogenesis in the Devonian Selwyn Basin

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