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TitleNeoarchean convergent margin-related Ni-Cu mineralization? Axis Lake and Nickel King Ni-Cu deposits in the south Rae craton of the Canadian Shield
AuthorAcosta-Góngora, P; Pehrsson, S J; Knox, B; Regis, D; Hulbert, L J; Creaser, R; Ashton, K
SourcePrecambrian Research 2018 p. 305-323,
Alt SeriesNatural Resources Canada, Contribution Series 20180090
Mediapaper; on-line; digital
File formatpdf
AreaAxis Lake; Nickel King
Lat/Long WENS -96.0000 -72.0000 67.6667 66.3333
Subjectsgeneral geology; mineralogy; Nature and Environment; Science and Technology; structural geology; nickel; copper; mineral deposits; intrusions; mafic intrusive rocks; ultramafic rocks; Churchill Province; Rae Craton; Neoarchean; Canadian Shield; Precambrian
Illustrationslocation maps; cross-sections; photographs; tables; plots; AFM diagrams
ProgramGEM2: Geo-mapping for Energy and Minerals, South Rae Province Bedrock/Surficial geology
Released2018 10 01
AbstractThe southern portion of the Rae craton in the Canadian Shield is host to multiple ca. 2.63 Ga Ni-Cu-rich metamorphosed mafic intrusions with noritic, noritic-anorthositic and pyroxenitic compositions, including those hosting the undeveloped Axis Lake and Nickel King deposits found in northern Saskatchewan and southeast Northwest Territories. In order to understand the setting of these intrusions, and their concomitant mineralization, we investigated their geochemical and isotopic characteristics. Mineralized intrusions at Axis Lake and Nickel King are metamorphosed up to granulite facies, with local partial melting. The intrusions preserve whole-rock major element geochemistry consistent with a sub-alkaline basaltic composition (e.g., SiO2=46-54 wt%; TiO2 < 0.5 wt%). In terms of their trace elements, these intrusions have: LREE to HREE enrichments (La/YbPM=2-16), low HREE fractionation (Gd/YbPM=1.0-2.6), well defined negative Nb (Nb/Nb?=0.06-0.31) and Zr (Zr/ Zr?=0.24-0.41) and variable negative to positive Ti anomalies (Ti/Ti?=0.25-1.38), and Th/Yb versus Nb/Yb distributions consistent with formation in an arc-like setting. The Nd isotope values of the Axis Lake intrusion (?Ndt2630=+0.3 to +2.1) are more juvenile and closer to the depleted mantle value, relative to those of the Nickel King deposit (?Ndt2630=?2.4 to ?0.4). This agrees with their also distinctive Th/Yb and Nb/Yb distributions suggesting oceanic and continental arc-like settings, respectively. The Axis Lake and Nickel King Nd isotope compositions are indistinguishable from other arc-like 2.61 to 2.58 Ga mafic to felsic intrusions and volcanic rocks recognized in the Rae craton and the neighboring Chesterfield block. The age, spatial distribution and geochemistry of the studied intrusions coincide with the initial stages of a recently defined 2.63-2.60 Ga continental arc, the roots of which are found in the south Rae craton. Our data indicate that Neoarchean intrusions with an arc-like geochemistry may be a significant exploration target in the Rae craton. This broadens possible host suites beyond the established Paleoproterozoic rift-related rocks most commonly considered as the prime target for Ni-Cu-PGE mineralization.
Summary(Plain Language Summary, not published)
The South Rae craton of the southeastern Northwest Territories and northern Saskatchewan is host to multiple Neoarchean Ni-Cu-rich prospects and undeveloped deposits contained in magmatic intrusions emplaced along the the Snowbird Tectonic Zone. In general, magmatic derived Ni-Cu deposits are constrain to crustal boundaries where the continental crust is rifted apart, but less often, this type of ore is found in convergent boundaries somewhat equivalent to that hosting the Andean volcanic range in South America. In this study we characterize the geochemistry of mafic intrusions hosting the South Rae's Nickel King and Axis Lake deposits, and suggest that these were formed in a convergent margin, distinct from previous rift-related exploration models commonly used in the Canadian shield. This has important implications for future mineral exploration in the area, and also provides new insights on the Neoarchean tectonic history of the south Rae craton.

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