Elsevier

Precambrian Research

Volume 275, April 2016, Pages 471-495
Precambrian Research

Age and geological setting of the Rankin Inlet greenstone belt and its relationship to the gold endowment of the Meliadine gold district, Nunavut, Canada

https://doi.org/10.1016/j.precamres.2016.01.008Get rights and content

Highlights

  • Calc-alkaline to tholeiitic and lesser MORB-like basaltic volcanism at 2.66 Ga.

  • Mesoarchean basement underlying the 2.66 Ga Rankin Inlet greenstone belt.

  • Intercalated 2.66 Ga and ≤2.50 Ga volcano-sedimentary panels.

  • Gold linked to 1.9 Ga reworking at cratonic margin and favourable lithostratigraphy.

Abstract

Archean greenstone belts host a significant proportion of the world's gold, typically in deposits that formed late during greenstone belt formation and cratonization. However, this is not always the case and, in the multiply reworked western Churchill Province (wCP), orogenic lode gold deposition post-dates greenstone belt formation by nearly one billion years. The spatial link between Proterozoic gold and Archean greenstone belts in the wCP is thus particularly striking although its significance is still not fully understood. The Meliadine gold district (2.8 Moz contained Au in reserves, plus an indicated and inferred resources of 5.8 Moz Au) represents an important example of this deposit style and is hosted within the Rankin Inlet greenstone belt (RIGB), which occupies a critical, but controversial position along the largely inferred boundary between the Hearne craton and the Chesterfield block.

RIGB felsic volcanic rocks (ca. 2.66 Ga) are structurally intercalated, and broadly coeval, with mafic volcanic and volcaniclastic rocks (2.66–2.64 Ga), turbidite (≤2.66–2.64 Ga), argillite, auriferous banded iron formation successions and syn-volcanic granodioritic to tonalitic intrusions (2.67–2.64 Ga). Neoarchean basaltic to andesitic volcanic rocks possess calc-alkaline to primitive arc-like tholeiitic magmatic affinities along with lesser MORB-like basaltic compositions. Geochemically evolved lavas yield depleted 144Nd/143Nd ratios (ɛNd2.66 Ga = −1.1 to +1.6) that reflect variable interaction with an evolved and hitherto undocumented Meso- to Neoarchean basement underlying the RIGB, whereas transitional, arc-like primitive tholeiitic and MORB-like basaltic samples overlap with the Nd isotopic composition of depleted mantle at ca. 2.66 Ga (ɛNd2.66 Ga = +1.6 to +2.7). These Neoarchean volcano-sedimentary panels represent the main auriferous rock package within the Meliadine gold district and are intercalated with deformed Paleoproterozoic conglomerate (≤2.50 and ≤2.155 Ga). The latter are, in turn, unconformably overlain by a geochemically distinct pillowed-basalt sequence and a unique carbonate-siliciclastic package that presumably represent the remnants of Paleoproterozoic basins and are not known to host gold. The geological setting of gold deposits thus likely reflects this favourable Neoarchean lithostratigraphy in addition to metamorphism and fluid focusing along the reactivated faults during the collision of the Hearne and combined Chesterfield block-Rae craton at 1.90–1.85 Ga.

Introduction

The western Churchill Province (wCP) represents a vast and gold-rich region of Canada's North (Fig. 1). The largest gold deposits, including the world-class Meadowbank mine (e.g., Sherlock et al., 2004, Janvier et al., 2015), are hosted by Archean greenstone belts and associated meta-sedimentary successions that include turbidite and banded iron formation (BIF; Fig. 1). Deposit host rocks are metamorphosed from greenschist (e.g., Meadowbank; e.g., Pehrsson et al., 2013a) to upper amphibolite facies (e.g., Three Bluffs; Davies et al., 2010) and deformed during at least four temporally-distinct Paleoproterozoic orogenic episodes (e.g., Berman, 2010). Each episode was coupled with the development and/or reactivation of lithospheric-scale faults and smaller-scale, subsidiary structures (Jones et al., 2002, Spratt et al., 2014). Gold is linked to this Paleoproterozoic metamorphic and reworking history and, at the scale of the wCP, occurs where regional faults cut favourable Archean greenstone belts (Fig. 1).

The broad association between gold, greenstone belts, faults and metamorphism is typical of the orogenic gold deposit type and characterizes most Archean gold districts globally (Groves et al., 1998, Groves et al., 2003, Goldfarb et al., 2005, Robert et al., 2005, Dubé and Gosselin, 2007, Robert et al., 2007, references therein). However, gold deposits within the wCP are atypical as gold post-dates the timing of mafic volcanism and cratonization by up to one billion years (Miller et al., 1995, Sherlock et al., 2004, Carpenter et al., 2005, Davies et al., 2010, Lawley et al., 2015a). This age gap contrasts with classic Neoarchean orogenic gold districts, such as the Abitibi, which share a close spatial and temporal relationship between gold, basin development, basin inversion along basin-bounding faults and attendant metamorphism during orogenesis (e.g., Bleeker, 2012, Bleeker, 2015). The spatial link between Proterozoic gold and Archean greenstone belts may reflect an extremely effective gold depositional mechanism(s) that operates exclusively in these settings (e.g., Groves et al., 1998) and/or may suggest that greenstone belts and associated supracrustal successions represent the ultimate source for gold (e.g., Pitcairn et al., 2006, Large et al., 2009).

The Meliadine gold district (MGD) represents a large (2.8 Moz contained Au in reserves and total resources of 5.8 Moz Au, www.agniecoeagle.com) and important example of BIF- and greenstone-hosted mineralization within the wCP (Fig. 1; Miller et al., 1994, Miller et al., 1995, Carpenter et al., 2005, Lawley et al., 2015a, Lawley et al., 2015b). The largest deposits occur north and along the Pyke Fault, which cuts Neoarchean mafic to felsic volcanic rocks, turbidite and BIF successions comprising the Rankin Inlet greenstone belt (RIGB; Fig. 2). The Pyke Fault also represents the approximate surficial trace of one segment of a lithospheric-scale fault network that cuts the wCP and potentially demarcates the inferred cratonic boundary between the Hearne craton and combined Rae craton and Chesterfield block (Fig. 1; e.g., Jones et al., 2002, Berman et al., 2007, Spratt et al., 2014, Pehrsson et al., 2015). The RIGB thus occupies a critical position within the wCP, but its age and relationship to nearby greenstone belts are undocumented.

In this contribution we report new U–Pb detrital and igneous zircon ages that confirm Neoarchean RIGB volcanic and siliciclastic rocks (2.67–2.66 Ga) are structurally imbricated with multiple Paleoproterozoic (≤2.50 Ga, this study; ≤2.155 Ga, Davis et al., 2008) conglomerate units and dismembered volcano-sedimentary basins. New field data are also synthesized with lithogeochemistry and Nd-isotopic data in order to explore tectonic links between the RIGB and neighbouring greenstone belts. The significance of these findings and particularly their relationship to the gold endowment of the MGD are discussed.

Section snippets

Western Churchill Province geology

The wCP extends along the western Hudson Bay coast (Fig. 1; Hoffman, 1988) and is subdivided into at least three distinct crustal domains (Berman et al., 2007). From north to south, these include the Rae craton, Chesterfield block and Hearne craton (Pehrsson et al., 2013a). Each domain is briefly discussed below, whereas a more complete, time-space comparison is provided in Eglington et al. (2013).

The Rae craton is the largest, but least understood of these three domains and comprises, in part,

Rankin Inlet greenstone belt lithostratigraphy

Rocks near the community of Rankin Inlet were originally defined as the Rankin Inlet Group (Bannatyne, 1958) and later referred to as the RIGB (Fig. 2; Aspler and Chiarenzelli, 1996). The region is the focus of sustained mineral exploration interest because of the past-producing Rankin Nickel Mine (Bannatyne, 1958) and on-going gold (Carpenter et al., 2005, this study) and diamond mineral exploration efforts (Seller, 1999). However, the geological setting of the RIGB and, particularly its

Gold deposit geology

Gold deposits within the MGD share similarities with typical orogenic greenstone- and BIF-hosted mineralization (Miller et al., 1995, Carpenter and Duke, 2004). High-grade gold intervals occur as a series of sub-parallel and semi-continuous ore zones that are known locally as lodes (Fig. 6). Most of these lodes correspond to folded, hydrothermally altered and veined BIF intervals (Fig. 6, Fig. 7, Fig. 8, Fig. 9), which are intercalated and folded with turbidite (e.g., Discovery) and volcanic

Geochemistry

Lithogeochemical data from the RIGB were compiled from Carpenter (2003; n = 60), Tella et al. (2005; n = 19), Lawley et al. (2015c; n = 344) and unpublished data from Sandeman (n = 45). Details on the analytical method, detection limits, quality control and estimates on the precision and accuracy of the results can all be found in those publications. The petrogenetic significance of these datasets to the RIGB has not previously been discussed. Samples with unpublished data were analyzed for major and

U–Pb zircon geochronology methodologies

All U–Pb zircon geochronology was completed at the Geological Survey of Canada, Ottawa. Zircon was concentrated from crushed and milled samples following a combination of Wilfley table, density (Methyl Iodide) and magnetic (Frantz™ isodynamic separator) techniques. Non-magnetic zircon grains were hand-picked under ethanol using a transmitted light microscope from the resulting mineral concentrate for further analysis. Zircon grains from four metasedimentary samples (CL1210, CL1211, CL1315, and

Rankin Inlet greenstone belt petrogenesis

In this section, lithogeochemistry of lavas and inferred lavas (mafic, fine-grained amphibolite to greenschist facies rocks) are used to reconstruct volcanic source(s) and setting(s). For simplicity, gabbroic and ultramafic dykes and sills are excluded as many cannot be demonstrably linked to the primary construction of the greenstone belt. The compositions of volcanic rocks are predominately basaltic with rare intermediate to felsic rocks that extend to dacitic compositions (Fig. 11b). All LVA

Conclusions

The RIGB comprises intercalated ca. 2.66 Ga predominately mafic volcanic and turbiditic successions deposited on an unexposed Meso- to Neoarchean substrate. Neoarchean volcano-sedimentary panels are structurally bound by Paleoproterozoic conglomerate and basalt that are, in turn, unconformably overlain by pillowed-basalt and a distinct carbonate-siliciclastic sequence that presumably represents the remnants of Proterozoic basins. Detrital zircon ages at ca. 2.50 Ga, together with the timing of

Acknowledgements

The MGD study was conducted under the auspices of Natural Resource Canada's Targeted Geoscience Initiative (TGI)-4. The authors would like to thank the cooperation and input from Agnico-Eagle Mines Ltd. throughout the study period. In particular, Robert Fraser, Jérôme Lavoie, Jean-Claude Blais, and Francine Fallara are thanked for facilitating field-work logistics, assisting on site and providing borehole logs, and geologic plans/sections for the deposits. We thank Robert Carpenter for his

References (107)

  • S. Hanmer et al.

    Geology and Neoarchean tectonic setting of the Central Hearne supracrustal belt, Western Churchill Province, Nunavut, Canada

    Precambrian Res.

    (2004)
  • S. Hanmer et al.

    Late Neoarchean thick-skinned thrusting and Paleoproterozoic reworking in the MacQuoid supracrustal belt and Cross Bay plutonic complex, western Churchill Province, Nunavut, Canada

    Precambrian Res.

    (2006)
  • K. Hron et al.

    Imputation of missing values for compositional data using classical and robust methods

    Comput. Stat. Data Anal.

    (2010)
  • C.J.M. Lawley et al.

    Defining and mapping hydrothermal footprints at the BIF-hosted Meliadine Gold District, Nunavut, Canada

    J. Geochem. Explor.

    (2015)
  • J.M. Mattinson

    Zircon U–Pb chemical abrasion (“CA-TIMS”) method: combined annealing and multi-step partial dissolution analysis for improved precision and accuracy of zircon ages

    Chem. Geol.

    (2005)
  • J.A. Pearce

    Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust

    Lithos

    (2008)
  • S.J. Pehrsson et al.

    Paleoproterozoic orogenesis during Nuna aggregation: a case study of reworking of the Rae craton, Woodburn Lake, Nunavut

    Precambrian Res.

    (2013)
  • S.J. Pehrsson et al.

    Two Neoarchean supercontinents revisited: the case for a Rae family of cratons

    Precambrian Res.

    (2013)
  • T.D. Peterson et al.

    The Kivalliq igneous suite: anorogenic bimodal magmatism at 1.75 Ga in the western Churchill Province

    Precambrian Res.

    (2015)
  • D.C. Petts et al.

    Age and evolution of the lower crust beneath the western Churchill Province: U–Pb zircon geochronology of kimberlite-hosted granulite xenoliths, Nunavut, Canada

    Precambrian Res.

    (2014)
  • R.H. Rainbird et al.

    Early Paleoproterozoic supracrustal assemblages of the Rae domain, Nunavut, Canada: intracratonic basin development during supercontinent break-up and assembly

    Precambrian Res.

    (2010)
  • J.C. Roddick

    Generalized numerical error analysis with application to geochronology and thermodynamics

    Geochim. Cosmochim. Acta

    (1987)
  • H.A. Sandeman et al.

    Neoarchean volcanic rocks, Central Hearne supracrustal belt, Western Churchill Province, Canada: geochemical and isotopic evidence supporting intra-oceanic, supra-subduction zone extension

    Precambrian Res.

    (2004)
  • H.A. Sandeman et al.

    Petrogenesis of Neoarchean volcanic rocks of the MacQuoid supracrustal belt: a back-arc setting for the northwestern Hearne subdomain, western Churchill Province, Canada

    Precambrian Res.

    (2006)
  • H.A. Sandeman et al.

    The Paleoproterozoic Kaminak dykes, Hearne Craton, western Churchill Province, Nunavut, Canada: preliminary constraints on their age and petrogenesis

    Precambrian Res.

    (2013)
  • R.H. Smithies

    Archean boninite-like rocks in an intracratonic setting

    Earth Planet. Sci. Lett.

    (2002)
  • M.J. Bannatyne

    The Geology of the Rankin Inlet Area and North Rankin Nickel Mines Limited, Northwest Territories

    (1958)
  • R.G. Berman et al.

    In situ SHRIMP U–Pb geochronology of Barrovian facies-series metasedimentary rocks in the Happy Lake and Josephine River supracrustal belts: implications for the Paleoproterozoic architecture of the northern Hearne Domain, Nunavut: Radiogenic Age and Isotopic Studies: Report 15

    (2002)
  • R.G. Berman et al.

    The collisional Snowbird tectonic zone resurrected: growth of Laurentia during the 1.9 Ga accretionary phase of the Trans-Hudson orogeny

    Geology

    (2007)
  • R.G. Berman

    Metamorphic Map of the Western Churchill Province, Canada

    (2010)
  • M.J. Bickle et al.

    Archean greenstone belts are not oceanic crust

    J. Geol.

    (1994)
  • W. Bleeker

    Targeted Geoscience Initiative 4. Lode Gold Deposits in Ancient Deformed and Metamorphosed Terranes: The Role of Extension in the Formation of Timiskaming Basins and Large Gold Deposits, Abitibi Greenstone Belt — A Discussion

    (2012)
  • W. Bleeker

    Synorogenic gold mineralization in granite-greenstone terranes: the deep connection between extension, major faults, synorogenic clastic basins, magmatism, thrust inversion, and long-term preservation

    Targeted Geoscience Initiative 4: Contributions to the Understanding of Precambrian Lode Gold Deposits and Implications for Exploration

    Geological Survey of Canada

    (2015)
  • W. Bleeker et al.

    Short-lived mantle generated magmatic events and their dyke swarms: the key unlocking Earth's paleogeographic record back to 2.6 Ga

  • K.L. Buchan et al.

    Diabase Dyke Swarms and Related Units in Canada and Adjacent Regions

    (2004)
  • R.L. Carpenter

    Relative and Absolute Timing of Supracrustal Deposition, Tectonothermal Activity and Gold Mineralization, West Meliadine region, Rankin Inlet Greenstone Belt, Nunavut, Canada

    (2003)
  • R.L. Carpenter et al.

    Geological setting of the West Meliadine Gold Deposits, Western Churchill Province, Nunavut, Canada

    Explor. Min. Geol.

    (2004)
  • R.L. Carpenter et al.

    Relative and absolute timing of gold mineralization along the Meliadine Trend, Nunavut, Canada: evidence for Paleoproterozoic gold hosted in an Archean greenstone belt

    Econ. Geol.

    (2005)
  • P.A. Cavell et al.

    Archean magmatism in the Kaminak Lake area, district of Keewatin, Northwest Territories: ages of the carbonatitie-bearing alkaline complex and some host granitoid rocks

    Can. J. Earth Sci.

    (1992)
  • D. Corrigan et al.

    The Palaeoproterozoic Trans-Hudson Orogen: a prototype of modern accretionary processes

    Geol. Soc. Lond. Spec. Publ.

    (2009)
  • B.L. Cousens et al.

    Enriched Archean lithospheric mantle beneath western Churchill Province tapped during Paleoproterozoic orogenesis

    Geology

    (2001)
  • A.J. Crawford et al.

    Classification, petrogenesis and tectonic setting of boninites

  • R. Creaser et al.

    Tectonic affinity of Nisutlin and Anvil assemblage strata from the Teslin tectonic zone, northern Canadian Cordillera: constraints from neodymium isotope and geochemical evidence

    Tectonics

    (1997)
  • T. Davies et al.

    Paleoproterozoic age relationships in the Three Bluffs Archean iron formation-hosted gold deposit, Committee Bay Greenstone Belt, Nunavut, Canada

    Explor. Min. Geol.

    (2010)
  • W.J. Davis et al.

    Geochronological Investigations of the Woodburn Lake Group, Western Churchill Province, Northwest Territories: Preliminary Results, in Radiogenic Age and Isotopic Studies, Report 11

    (1998)
  • W.J. Davis et al.

    Regional differences in the Neoarchean crustal evolution of the Western Churchill Province: Can we make sense of it?

  • W.J. Davis et al.

    Detrital zircon geochronology of the Paleoproterozoic Hurwitz and Kiyuk groups, western Churchill Province, Nunavut

    (2005)
  • W.J. Davis et al.

    A Paleoproterozoic Detrital Zircon Age for a Key Conglomeratic Horizon within the Rankin Inlet Area, Kivalliq Region, Nunavut: Implications for Archean and Proterozoic Evolution of the Area

    (2008)
  • D.J. DePaolo

    Neodymium isotopes in the Colorado front range and crust-mantle evolution in the Proterozoic

    Nature

    (1981)
  • M.J. De Witt

    On Archean granites, greenstones, cratons, and tectonics: does the evidence demand a verdict?

    Precambrian Res.

    (1998)
  • Cited by (8)

    • Structural features and age of gold mineralization in the Troia Massif, Borborema Province, NE Brazil: A Paleoproterozoic (∼2029 Ma)hypozonal orogenic gold deposit overprinted by the late Neoproterozoic Brasiliano/Pan–African orogeny

      2019, Journal of South American Earth Sciences
      Citation Excerpt :

      However, later in the 1990s, researchers clearly demonstrated an epigenetic origin for this type of orogenic deposits (Groves et al., 1998). Therefore, interpreting all these elements together, gold mineralization in the Serra das Pipocas greenstone belt displays the typical stratigraphic and structural characteristics of other greenstone–hosted orogenic gold deposits (e.g. Morey et al., 2007; Oliver et al., 2012; Zhou et al., 2016; Lawley et al., 2016; Groves et al., 2018), such as the connection with a first–order structure and the apparent lithological control of gold deposition, and therefore, supporting its classification as an orogenic gold deposit. The ages of the different deformation events in the Troia Massif are still not well established.

    • Neoarchean convergent margin Ni-Cu mineralization? Axis Lake and Nickel King Ni-Cu deposits in the south Rae craton of the Canadian Shield

      2018, Precambrian Research
      Citation Excerpt :

      The western Churchill Province (wCP) of the Canadian Shield encompasses the Rae and Hearne cratons (Hoffman, 1988; Eglington et al., 2013), and the Chesterfield block (Berman et al., 2007; Fig. 1A). These crustal entities are best known for their world class Au and U districts (Meliadine and Meadowbank Au: Armitage et al., 1996; Lawley et al., 2016; Sherlock et al., 2004; Athabasca and Kiggavik U; Jefferson et al., 2007 and references therein). Several Ni-Cu-PGE deposits/mineral occurrences are known in the wCP, most prominently the past-producing Rankin Inlet mine (Bannatyne, 1958), and the undeveloped Nickel King (Thomas, 1976; Buhlmann, 1989), Ferguson Lake (Martel et al., 2004; Campos-Álvarez et al., 2011; Acosta-Góngora et al., 2018) and Axis Lake (Coombe Geoconsultants Ltd., 1991) deposits.

    • Geology of the world-class Kiaka polyphase gold deposit, West African Craton, Burkina Faso

      2017, Journal of African Earth Sciences
      Citation Excerpt :

      No clear relationship with the stage 1 of mineralization and the diorite intrusion is observed but some small ore bodies appear to cut across or developed at the contact with small dioritic dykes (Fig. 4a). Our data supports close spatial and temporal relationships between deformation (D2, D3 and D4), gold, diorite magmatism and amphibolite facies metamorphism, a feature also described in the Baoulé-Mossi domain (John et al., 1999; Debat et al., 2003; Ganne et al., 2011; McFarlane et al., 2011), in the Trans Hudson orogen (Lawley et al., 2016) and the Lupa goldfield (Lawley et al., 2013). Re-Os dating of syn-SK2 xenomorphic pyrrhotite (possibly mixed with some chalcopyrite and arsenopyrite) yields a weighted average Re-Os age of 2157 ± 24 Ma (MSWD = 0.25; n = 3).

    View all citing articles on Scopus
    View full text