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Bedrock Geology and Economic Potential of the Archean Mary River Group, Northern Baffin Island, Nunavut

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Bedrock Geology and Economic Potential of the Archean Mary River Group, Northern Baffin Island, Nunavut Geological Survey of Canada CURRENT RESEARCH 2006-C5 Bedrock geology and economic potential of the Archean Mary River group, northern Baffin Island, Nunavut S.M. Johns and M.D. Young 2006 CURRENT RESEARCH Natural Resources Ressources naturelles Canada Canada ©Her Majesty the Queen in Right of Canada 2006 ISSN 1701-4387 Catalogue No. M44-2006/C5E-PDF ISBN 0-662-44295-4 A copy of this publication is also available for reference by depository libraries across Canada through access to the Depository Services Program's Web site at http://dsp-psd.pwgsc.gc.ca A free digital download of this publication is available from GeoPub: http://geopub.nrcan.gc.ca/index_e.php Toll-free (Canada and U.S.A.): 1-888-252-4301 Critical reviewer(s) Sally Pehrsson James Donald Author(s) Shannon M. Johns Michael D. Young ([email protected]) ([email protected]) 51 Beurling Crescent, 2233 E 12th Avenue, Saskatoon, Saskatchewan Vancouver, British Columbia S7H 4V6 V5N 2B2 Publication approved by Canada-Nunavut Geoscience Office Correction date: All requests for permission to reproduce this work, in whole or in part, for purposes of commercial use, resale, or redistribution shall be addressed to: Earth Sciences Sector Information Division, Room 402, 601 Booth Street, Ottawa, Ontario K1A 0E8. Bedrock geology and economic potential of the Archean Mary River group, northern Baffin Island, Nunavut S.M. Johns and M.D. Young Johns, S.M. and Young, M.D., 2006: Bedrock geology and economic potential of the Archean Mary River group, northern Baffin Island, Nunavut; Geological Survey of Canada, Current Research 2006-C5, 13 p. Abstract: Bedrock mapping and prospecting in northern Baffin Island, including parts of NTS map areas 37 E, F, G, and H, has redefined interpretations of the stratigraphy and structure of the Archean Mary River group, surrounding gneiss, and intrusions. In the study area, the Mary River group includes psammite and sedimentary migmatite, amphibolite, ±psammite and sedimentary migmatite, Algoma-type silicate- and oxide-facies iron-formation, ±dacite, ±psammite, and quartzite, intruded by late ultramafic and gabbroic sills and dykes. Three episodes of penetrative deformation are recognized and Archean and Proterozoic rocks underwent amphibolite- to granulite-facies regional metamorphism during the ca. 1.8 Ga Hudsonian Orogeny. The youngest regional event, defined as D3, folded metamorphic isograds and pre-D3 fabrics. New economic mineral prospects include 20 m thick magnetite beds within iron-formation, and vis- ible gold and molybdenum in quartz veins. The area also has potential for Ni-Cu-PGE magmatic sulphide mineralization in mafic and ultramafic sills. Résumé : La cartographie du substratum rocheux et les travaux de prospection dans le nord de l’île de Baffin, notamment dans les régions couvertes par des parties des cartes 37 E, F, G et H du SNRC, ont permis d’élaborer de nouvelles interprétations de la stratigraphie et de la structure du groupe de Mary River de l’Archéen, ainsi que des gneiss et des intrusions avoisinants. Dans la région d’étude, le groupe de Mary River se présente comme suit : psammite et migmatite sédimentaire, amphibolite, ± psammite et migmatite sédimentaire, formation de fer de type Algoma à faciès silicaté et oxydé, ± dacite, ± psammite et quartzite. Toutes les unités précédentes sont recoupées par des filons-couches et des dykes ultramafiques et gabbroïques de formation tardive. Trois épisodes de déformation pénétrative sont distingués et les roches de l’Archéen et du Protérozoïque ont subi un métamorphisme régional allant du faciès des amphibolites au faciès des granulites pendant l’orogenèse hudsonienne, à 1,8 Ga environ. L’événement régional le plus récent, attribué à D3, a plissé les isogrades du métamorphisme et les fabriques antérieures à D3. De nou- veaux prospects de minéralisations d’intérêt comprennent des lits de magnétite de 20 m d’épaisseur dans la formation de fer, ainsi que de l’or visible et du molybdène dans des filons de quartz. La région recèle en outre un certain potentiel quant aux minéralisations de sulfures magmatiques de Ni-Cu-ÉGP dans des filons-couches mafiques et ultramafiques. Current Research 2006-C5 1 S.M. Johns and M.D. Young INTRODUCTION Melville Peninsula (Penrhyn Group) across Baffin Island (Piling Group) to west Greenland (Karrat Group) (Fig. 1) (Jackson and Taylor 1972; Henderson and Tippett, 1980; This report outlines preliminary field results from the Hoffman, 1988, 1990; Henderson et al., 1989; Jackson and 2005 season for the bedrock component of the three-year Berman 2000). North Baffin Project, a collaborative effort of the Canada- Nunavut Geoscience Office and the Geological Survey of The Mary River group, exposed on northern Baffin Canada. The primary objective of this project is surficial Island, comprises two greenstone belts in the Eqe Bay area mapping and till sampling of NTS map areas 37 E, F, G, and (Fig. 1), the Isortoq and Eqe Bay belts (Bethune and H, northern Baffin Island, Nunavut (Fig. 1), with correspond- Scammell, 1993, 2003a, b; Scammell and Bethune, 1995). ing targeted bedrock mapping and prospecting of selected Primary stratigraphic relationships are well exposed within areas (Young et al., 2004). Surficial geology was discussed the predominantly greenschist-facies Eqe Bay belt. The by Little et al. (2004) and Utting et al. (2006). stratigraphic sequence of the Eqe Bay belt, from base to top, is characterized by mafic to intermediate volcanic rocks, This project builds on previous regional bedrock mapping iron-formation, subordinate quartzite, intermediate to felsic projects throughout the northern Rae Domain of the western volcanic rocks, and overlain by conglomerate and a Churchill Province: the Clyde-Cockburn Land area, greywacke-turbidite sequence (Bethune and Scammell, north-central Baffin Island (Jackson, 2000, 1996; Jackson 2003a). This assemblage is interpreted to represent the for- and Berman, 2000), the Eqe Bay area to the south (Bethune mation of a volcanic arc on thinned continental crust with and Scammell, 1993, 2003a, b; Scammell and Bethune; associated fumarolic activity forming iron-formation deposits 1995), and the Committee Bay region to the southwest (Bethune and Scammell, 2003a). In contrast, the mafic volca- (Frisch, 1982; Sanborn-Barrie et al., 2003; Skulski et al., nic sequences and associated ultramafic volcanic rocks of the 2003; Carson et al., 2004; Berman et al., 2005) (Fig. 1). The Woodburn Lake and Prince Albert groups are interpreted as purposes of the bedrock component of the North Baffin melting products of one or more mantle plumes in a continen- Project are to discover prospective areas of economic mineral tal-rift setting (Zaleski et al., 1999, 2001; Skulski et al., potential, collect rock samples for assay analysis supporting 2003). Schau and Ashton (1988) suggested an additional the drift prospecting component (Utting et al., 2006), and to interpretation for the Prince Albert Group, where the interme- update the stratigraphic, metamorphic, structural, geochemi- diate volcanic rocks formed within an ensialic basin or during cal, and geochronological knowledge for the Mary River crustal rifting above a linear mantle upwelling or plume, group on northern Baffin Island. wherein the mafic volcanic rocks formed at the basin margins and the felsic volcanic rocks formed by partial melting of the lower crust. GEOLOGICAL SETTING The rocks of the Woodburn Lake, Prince Albert, and Mary River groups have been affected by several episodes of The study area occurs in the ca. 3.0–2.5 Ga Committee Archean and Proterozoic deformation and metamorphism. belt of the western Churchill Province (Jackson and Berman, Evidence for three Archean metamorphic events is thought to 2000). The Committee belt is part of the northern Rae be preserved in the Eqe Bay greenstone belt (Bethune and Domain (Hoffman, 1988), and is characterized by felsic Scammell, 2003b). The first event is based on structural and plutonism and greenschist- to upper-amphibolite-facies metamorphic complexity observed in the gneiss complex supracrustal (greenstone) belts (Jackson and Berman, 2000). which is absent from, and likely predates, the ca. 2780–2770 Ma These supracrustal belts are discontinuous, trend northeast orthogneiss and ca. less than 2770 Ma supracrustal Mary (Jackson and Berman, 2000; Skulski et al., 2003), and River group. The second event involved folding of volcanic extend from Baker Lake in southern Nunavut to northwest rocks and iron-formation of the Mary River group, which is Greenland (Fig. 1). Correlative sequences include the inferred to have occurred before the eruption of ca. Woodburn Lake, Prince Albert, and Mary River groups of the 2740–2725 Ma intermediate to felsic volcanic rocks. The Rae domain, and the Inglefield Bredning–Melville Bugt third is represented by low- to medium-pressure metamor- region of northwestern Greenland (Fig. 1) (Frisch, 1982; phism of the entire Eqe Bay belt, which postdates turbidite Schau and Ashton, 1988; Zaleski et al., 1999, 2001; Jackson sedimentation and is coeval with ca. 2700–2690 Ma and Berman, 2000). These ca. 2.74–2.68 Ga Neoarchean peraluminous plutonism. Geochronology from the Commit- supracrustal sequences were deposited on ca. 3.0–2.8 Ga tee Bay belt indicates that the northern Rae Domain experi- Mesoarchean plutonic crust (Jackson et al., 1990; Jackson enced a metamorphic event at ca. 2.35 Ga (Carson et al., and Berman, 2000; Zaleski et al., 2000; Wodicka et al., 2002; 2004; Berman et al., 2005). Structural studies of the Woodburn Bethune and Scammell, 2003a; Pehrsson et al., 2005). The Lake Group also identified evidence for Archean deformation Mary River group is bordered to the southeast by the inferred events (Pehrsson et al., 2004). Paleoproterozoic deformation crustal-scale Isortoq fault zone (Fig. 2) (Jackson, 2000; within the northern Rae Domain was widespread during the Bethune and Scammell, 2003b) and locally overlain by Hudsonian Orogeny at ca. 1.8 Ga, and resulted in the devel- Paleoproterozoic supracrustal sequences, which extend from opment of a strong northeast-southwest structural grain in the Current Research 2006-C5 2 S.M.
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