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Geological Investigations of the Cat Creek Area

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Geological Investigations of the Cat Creek Area GS-3 Geological investigations of the Cat Creek area in the Neoarchean Bird River greenstone belt, southeastern Manitoba (part of NTS 52L12): new insights into PGE-Ni-Cu-Cr mineralization by X.M. Yang, H.P. Gilbert and M.G. Houlé1 Yang, X.M., Gilbert, H.P. and Houlé, M.G. 2012: Geological investigations of the Cat Creek area in the Neoarchean Bird River greenstone belt, southeastern Manitoba (part of NTS 52L12): new insights into PGE-Ni-Cu-Cr mineralization; in Report of Activities 2012, Manitoba Innovation, Energy and Mines, Manitoba Geological Survey, p. 32–53. Summary upper anorthosite to leucogabbro The Cat Creek area in the northern arm of the Bird zone. The geochemical signature River greenstone belt is situated approximately 145 km of the Mayville intrusion suggests northeast of Winnipeg in southeastern Manitoba. The the parental magma(s) was an alumina-enriched tholeiitic study area is underlain by a suite of typical greenstone type that may have been derived from a high degree of assemblages within a continental-margin setting adjacent partial melting of the subcontinental lithospheric mantle; to the Mesoarchean Maskwa Lake Batholith. The rock it may have experienced assimilation and fractional crys- assemblages consist of a tonalite-trondhjemite-granodio- tallization during its emplacement within the supracrustal rite suite; supracrustal rocks that include mafic to felsic rock succession. An early sulphide saturation event trig- volcanic and synvolcanic intrusive rocks, and epiclastic gered by crustal contamination and/or introduced external and minor volcaniclastic rocks; the Mayville mafic–ultra- sulphur is likely to have generated magmatic sulphide Ni- mafic layered intrusion; and late peraluminous granitoid Cu-PGE mineralization at the base of the intrusion. The rocks and related pegmatites. The Mayville intrusion injection of a new batch(s) of a mafic–ultramafic melt consists of an east-trending lopolith approximately may have resulted in PGE and chromite mineralization 10.5 km in length and up to 1.5 km in width. The intru- at transitional zones between various phases within the sion is emplaced in a mid-ocean-ridge basalt (MORB) intrusion. In addition, calcic anorthosite in the Mayville sequence to the south and west and is in structural contact intrusion may represent a potential source for the manu- with granitoid rocks to the east. To the north, the May- facture of aluminum-bearing chemicals. ville intrusion is emplaced in metasedimentary and inter- calated volcaniclastic rocks, and is locally structurally Introduction juxtaposed against granitoid rocks. Although the May- In 2011, the Manitoba Geological Survey (MGS) ville intrusion has recently been the focus of ongoing initiated a multiyear bedrock geological mapping proj- mineral exploration because it hosts a significant amount ect focusing on the Cat Creek and Cat Lake–Euclid Lake of platinum group element (PGE)–Ni–Cu–Cr mineral- areas in the northern arm of the Bird River greenstone ization, some key metallogenic questions remain to be belt (BRGB), within the western Superior Province. This answered. project is conducted in collaboration with the Geological This report presents the preliminary results of geo- Survey of Canada (GSC) through the Targeted Geosci- logical mapping conducted at a scale of 1:12 500 by the ence Initiative Phase IV (TGI-4) program, and supported Manitoba Geological Survey in 2012, together with new by mining companies including Mustang Minerals Corp. petrological, lithogeochemical and geochronological data The main objectives of the project are to 1) update the acquired within the last year. Twelve map units have been regional geological mapping in the Cat Creek and Cat identified in the Cat Creek area. The mapping and geo- Lake–Euclid Lake areas, 2) address the geological evolu- chemical study suggest that the MORB-type basalts and tion and the geodynamic environment, and 3) assess the related intrusive rocks, as well as the Mayville intrusion, metallogeny of magmatic sulphide Ni-Cu-PGE-Cr miner- may have been emplaced in an extensional back-arc envi- alization within the BRGB. ronment characterized by a relatively thin crust (~21 km) This report presents the preliminary results of geo- and a continental-margin setting. The present geological logical mapping at a scale of 1:12 500 conducted by the map data indicate that the Neoarchean Mayville intru- MGS this past summer, together with new petrological, sion (U-Pb zircon age of 2743 Ma) consists dominantly lithogeochemical and geochronological data acquired of anorthositic gabbro, gabbroic anorthosite and anortho- over the last year. Furthermore, a more detailed and mod- site, with subordinate melagabbro and pyroxenite at the ern geological map covering the Cat Lake–Euclid Lake base and gabbro at the top. This intrusion is similar to areas, including a detailed geological map of the Cat Archean anorthosite complexes elsewhere, and can be Creek area, is designed to aid mineral exploration, in par- subdivided into a lower heterolithic breccia zone and an ticular for magmatic Ni-Cu-PGE-Cr mineralization. 1 Geological Survey of Canada, 490 rue de la Couronne, Québec, Quebec G1K 9A9 32 Manitoba Geological Survey Previous work Regional geological mapping at a scale of 1 inch to The BRGB has long been the subject of geological 1 mile (1:63 360) in the area between Maskwa Lake and investigations, primarily because it contains magmatic Cat Lake, as well as in the Bird River area to the south, Ni-Cu-PGE-Cr minerals, a world-class Cs–Ta–Nb–Li– was carried out by Springer (1949, 1950). He concluded rare earth element (REE) deposit at the TANCO mine, that the dominant structure in the region is anticlinal, with and numerous other mineral occurrences, such as Au and the Bird River Sill (BRS; Figure GS-3-2) in the south limb Cu-Zn (Springer, 1949, 1950; Trueman and Macek, 1971; dipping steeply to the south, and the north limb (includ- Trueman, 1980; Scoates, 1983; Macek, 1985a, b; Theyer, ing the Mayville intrusion) being partly overturned and 1986, 2003; Scoates et al., 1989; Peck et al., 1999, 2000, also dipping to the south. Springer (1949, 1950) implied 2002; Hulbert and Scoates, 2000; Gilbert, 2006, 2007; that the configuration of the mafic–ultramafic BRS, the Kremer and Lin, 2006; Gilbert et al., 2008; Mealin, 2008; Mayville intrusion and analogous rocks at Euclid Lake Duguet et al., 2009; Good et al., 2009; Kremer, 2010; reflect the closure of an east-plunging anticlinal fold. Stott et al., 2010). Its tectonic location between two con- This interpretation was supported by Trueman and Macek tinental cratonic blocks, the English River and Winnipeg (1971), Trueman (1980), Černý et al. (1981) and Macek River subprovinces (Figure GS-3-1), guides the general (1985a, b). The regional bedrock geology, including the understanding of the BRGB, corroborated by system- BRGB, was compiled by the MGS at a scale of 1:250 000 atic geological and multidisciplinary investigations (e.g., (Manitoba Energy and Mines, 1987), as well as by subse- Beaumont-Smith et al., 2003; Percival et al., 2006a, b; quent collaborative mapping projects involving the MGS, Anderson, 2007, 2008; Percival, 2007; Corkery et al., GSC and Ontario Geological Survey (Bailes et al., 2003; 2010), as well as larger scale studies on geodynamic pro- Lemkow et al., 2006). cesses involving the assembly of different terranes within Macek (1985b) published a preliminary 1:10 000 the Archean craton (e.g., Hoffman, 1988; Böhm et al., scale geological map of the western part of the Mayville 2000; Burke, 2011). intrusion and surrounding rocks, and tentatively sug- gested that the intrusion is part of the BRB. Subsequently, 0 0 NORTHERN 94 W 86 W detailed geological mapping was carried out by various SUPERIOR mineral-exploration companies (e.g., Exploratus Ltd., SUPERTERRANE Falconbridge Ltd., Tantalum Mining Corporation of Can- Manitoba Ontario ada Ltd.) on their respective properties. Most recently, PHANEROZOIC Mustang Minerals Corp. completed 1:1 000 scale geolog- COVER ical mapping of the western part of the Mayville intrusion, NNORTHORTH where diamond-drilling targeted rocks hosting PGE-Cu- Ni-Cr mineralization (Mustang Minerals Corp., 2011; CCARIBOUARIBOU Galeschuk, pers. comm., 2012). 520N In 2005, MGS initiated a four-year mapping project SSUPERTERRANEUPERTERRANE Lake focusing on the main, southern part of the BRGB, in col- Winnipeg laboration with several universities and mineral-explora- UUCHICHI TERRANETERRANE EENGLISHNGLISH tion companies (Gilbert, 2008; Gilbert and Kremer, 2008; BIRD RRIVERIVER RIVER SSUBPROVINCEUBPROVINCE Gilbert et al., 2008). The northern limb of the BRGB (Cat SUB- PROVINCE WINNIPEG RIVER Creek–Euclid Lake area; Figure GS-3-2) has, however, SUBPROVINCE received less attention. 480N WESTERN Canada WABIGOON United States Regional geology TERRANE Lake The Neoarchean BRGB is situated between the Superior English River and Winnipeg River subprovinces of the Northern Superior Superterrane (3.9–2.8 Ga) western Superior Province (Figure GS-3-1; Peck et al., North Caribou Superterrane (3.0–2.87 Ga) 2002; Gilbert et al., 2008). It is part of an approximately Winnipeg River Subprovince (3.4–2.8 Ga) 150 km long, east-trending supracrustal belt that extends Bird River greenstone belt (2.80–2.70 Ga): arc volcanic, sedimentary and plutonic rocks from Lac du Bonnet in the west to Separation Lake Volcanic rocks, continental arc 200 km (Ontario) in the east, where it is termed the ‘Separation Metasedimentary rocks Lake
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