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Part 1: Solving the controversy on the genesis of the world’s largest sediment-hosted copper reserves via detailed sulfide Re-Os geochronology: implications for genetic models and mineral exploration programs, and, Part 2: Further development of the (171496)
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  • Open Access English
    Authors: 
    Nicolas Saintilan; Thomas Edward Sheldrake; Robert A. Creaser; David Selby; Jerry Zieg; Adrian J. Boyce; Cyril Chelle-Michou;
    Publisher: ETH Zurich
    Countries: United Kingdom, Switzerland
    Project: SNSF | Development of Re-Os syst... (162075), SNSF | Part 1: Solving the contr... (171496), NSERC

    The ca. 1,500 to 1,325 Ma Mesoproterozoic Belt-Purcell Basin is an exceptionally preserved archive of Mesoproterozoic Earth and its paleoenvironmental conditions. The Belt-Purcell Basin is also host to world-class base metal sediment-hosted mineralization produced in a variety of settings from the rift stage of basin evolution through the subsequent influence of East Kootenay and Grenvillian orogenies. The mineral potential of this basin has not been fully realized yet. New rhenium-osmium (Re-Os) data presented here for chalcopyrite, pyrite, and black shale contribute to refine a robust genetic model for the origin of the Black Butte copper +/- cobalt +/- silver (Cu +/- Co +/- Ag) deposit hosted by the ca. >1,475 Ma Newland Formation in the Helena Embayment of the Belt-Purcell Basin in Montana, USA. Chalcopyrite Re-Os data yield an isochron age (1,488 +/- 34 Ma, unradiogenic initial Os-187/Os-188 composition Osi-ctudcoprite = 0.13 +/- 0.11) that overlaps with the geological age of the Newland Formation. Further, the Re-Os data of synsedimentary to diagenetic massive pyrite yield evidence of resetting with an isochron age (1,358 +/- 42 Ma) coincident with the timing of the East Kootenay orogeny. The unradiogenic Osi-ctudcoprite at ca. 1,488 Ma (0.13 +/- 0.11) argues for derivation of Os from a magmatic source with a Os-18(7)/Os-18(8) isotopic composition inherited from the upper mantle in the Mesoproterozoic (Os-mantle (1,475 Ma) = 0.12 +/- 0.02). The unradiogenic Osi-ctudcoprite also suggests limited contamination from a continental crustal source. This source of Os and our new sulfur isotopic signatures of chalcopyrite (-4.1 to +2.1 parts per thousand-VCDT) implies a dominantly magmatic source for metals. We integrate our new results and previously published geological and geochemical evidence to conceptualize a genetic model in which Cu and metals were largely contributed by moderate-temperature, reduced magmatic-hydrothermal fluids carrying reduced sulfur species with a magmatic origin and flowing as highly metalliferous fluids within the shale sequence. A subsidiary derivation of metals during thermally forced shale diagenesis is possible. Chalcopyrite mineralization replaced locally massive synsedimentary to diagenetic pyrite units close to the sediment-water interface, i.e., an ideal locus where magmatic-hydrothermal fluids could cool and the solubility of chalcopyrite would fall. We suggest that Cu mineralization was coeval with the timing of an enhanced thermal gradient in the Helena Embayment triggered until ca. 1,455 Ma by tholeiitic dike swarm that intruded into Archean basement rocks and intersected the NE-SW-trending Great Falls Tectonic Zone. Lithosphere, 2021 (1) ISSN:1941-8264 ISSN:1947-4253

  • Open Access English
    Authors: 
    Nicolas Saintilan; David Selby; Robert A. Creaser; Stijn Dewaele;
    Publisher: Nature Publishing Group UK
    Countries: United Kingdom, Belgium, Switzerland
    Project: SNSF | Part 1: Solving the contr... (171496)

    The origin of giant, sedimentary rock-hosted copper-cobalt (Cu-Co) provinces remains contentious, in part due to the lack of precise and reliable ages for mineralisation. As such, no consensus has been reached on the genetic model for ore formation, and the relationships between tectonism, palaeo-fluid circulation and mineralisation. Here, we link the timing of Cu-Co mineralisation in the Central African Copperbelt to compressional tectonics during the Lufilian Orogeny by using new ca. 609–473 Ma ages given by rhenium-osmium (Re-Os) isotope data for individual Cu-Co sulphides (carrolite and bornite) from the Cu-Co Kamoto deposit. The initial Os isotope composition of carrolite is compatible with the leaching of Os and Cu(-Co) from Mesoproterozoic Cu sulphide deposits hosted in fertile basement. In contrast, the ca. 473 Ma Cu-Au mineralisation stage, which is coeval with late- to post-compressional deformation, may be a distal expression of fluid flow and heat transfer caused by magmatic intrusions in the core of the collisional orogen. The Re-Os ages support a model for mineralisation driven by evaporite dissolution and percolation of large volumes of dense brines in the Katangan Basin during the Lufilian Orogeny. Scientific Reports, 8 ISSN:2045-2322

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Part 1: Solving the controversy on the genesis of the world’s largest sediment-hosted copper reserves via detailed sulfide Re-Os geochronology: implications for genetic models and mineral exploration programs, and, Part 2: Further development of the (171496)
Include:
The following results are related to Canada. Are you interested to view more results? Visit OpenAIRE - Explore.
2 Research products, page 1 of 1
  • Open Access English
    Authors: 
    Nicolas Saintilan; Thomas Edward Sheldrake; Robert A. Creaser; David Selby; Jerry Zieg; Adrian J. Boyce; Cyril Chelle-Michou;
    Publisher: ETH Zurich
    Countries: United Kingdom, Switzerland
    Project: SNSF | Development of Re-Os syst... (162075), SNSF | Part 1: Solving the contr... (171496), NSERC

    The ca. 1,500 to 1,325 Ma Mesoproterozoic Belt-Purcell Basin is an exceptionally preserved archive of Mesoproterozoic Earth and its paleoenvironmental conditions. The Belt-Purcell Basin is also host to world-class base metal sediment-hosted mineralization produced in a variety of settings from the rift stage of basin evolution through the subsequent influence of East Kootenay and Grenvillian orogenies. The mineral potential of this basin has not been fully realized yet. New rhenium-osmium (Re-Os) data presented here for chalcopyrite, pyrite, and black shale contribute to refine a robust genetic model for the origin of the Black Butte copper +/- cobalt +/- silver (Cu +/- Co +/- Ag) deposit hosted by the ca. >1,475 Ma Newland Formation in the Helena Embayment of the Belt-Purcell Basin in Montana, USA. Chalcopyrite Re-Os data yield an isochron age (1,488 +/- 34 Ma, unradiogenic initial Os-187/Os-188 composition Osi-ctudcoprite = 0.13 +/- 0.11) that overlaps with the geological age of the Newland Formation. Further, the Re-Os data of synsedimentary to diagenetic massive pyrite yield evidence of resetting with an isochron age (1,358 +/- 42 Ma) coincident with the timing of the East Kootenay orogeny. The unradiogenic Osi-ctudcoprite at ca. 1,488 Ma (0.13 +/- 0.11) argues for derivation of Os from a magmatic source with a Os-18(7)/Os-18(8) isotopic composition inherited from the upper mantle in the Mesoproterozoic (Os-mantle (1,475 Ma) = 0.12 +/- 0.02). The unradiogenic Osi-ctudcoprite also suggests limited contamination from a continental crustal source. This source of Os and our new sulfur isotopic signatures of chalcopyrite (-4.1 to +2.1 parts per thousand-VCDT) implies a dominantly magmatic source for metals. We integrate our new results and previously published geological and geochemical evidence to conceptualize a genetic model in which Cu and metals were largely contributed by moderate-temperature, reduced magmatic-hydrothermal fluids carrying reduced sulfur species with a magmatic origin and flowing as highly metalliferous fluids within the shale sequence. A subsidiary derivation of metals during thermally forced shale diagenesis is possible. Chalcopyrite mineralization replaced locally massive synsedimentary to diagenetic pyrite units close to the sediment-water interface, i.e., an ideal locus where magmatic-hydrothermal fluids could cool and the solubility of chalcopyrite would fall. We suggest that Cu mineralization was coeval with the timing of an enhanced thermal gradient in the Helena Embayment triggered until ca. 1,455 Ma by tholeiitic dike swarm that intruded into Archean basement rocks and intersected the NE-SW-trending Great Falls Tectonic Zone. Lithosphere, 2021 (1) ISSN:1941-8264 ISSN:1947-4253

  • Open Access English
    Authors: 
    Nicolas Saintilan; David Selby; Robert A. Creaser; Stijn Dewaele;
    Publisher: Nature Publishing Group UK
    Countries: United Kingdom, Belgium, Switzerland
    Project: SNSF | Part 1: Solving the contr... (171496)

    The origin of giant, sedimentary rock-hosted copper-cobalt (Cu-Co) provinces remains contentious, in part due to the lack of precise and reliable ages for mineralisation. As such, no consensus has been reached on the genetic model for ore formation, and the relationships between tectonism, palaeo-fluid circulation and mineralisation. Here, we link the timing of Cu-Co mineralisation in the Central African Copperbelt to compressional tectonics during the Lufilian Orogeny by using new ca. 609–473 Ma ages given by rhenium-osmium (Re-Os) isotope data for individual Cu-Co sulphides (carrolite and bornite) from the Cu-Co Kamoto deposit. The initial Os isotope composition of carrolite is compatible with the leaching of Os and Cu(-Co) from Mesoproterozoic Cu sulphide deposits hosted in fertile basement. In contrast, the ca. 473 Ma Cu-Au mineralisation stage, which is coeval with late- to post-compressional deformation, may be a distal expression of fluid flow and heat transfer caused by magmatic intrusions in the core of the collisional orogen. The Re-Os ages support a model for mineralisation driven by evaporite dissolution and percolation of large volumes of dense brines in the Katangan Basin during the Lufilian Orogeny. Scientific Reports, 8 ISSN:2045-2322