The northern and southern sections of the western ca. 1880 Ma Circum-Superior Large Igneous Province, North America: The Pickle Crow dyke connection? Matthew J. Minifie a, ⁎, Andrew C. Kerr a , Richard E. Ernst b, c , Alan R. Hastie d , T. Jake R. Ciborowski a , Guy Desharnais e , Ian L. Millar f a School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK b Ernst Geosciences, 43 Margrave Avenue, Ottawa, Ontario, Canada K1T 3Y2 c Department of Earth Sciences, Carleton University, Ottawa, Ontario, Canada K1S 5B6 d School of Geography, Geology and the Environment, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey KT1 2EE, UK e SGS Geostat, 10 boul. de la Seigneurie Est, Bureau 203, Blainville, Quebec, Canada J7C3V5 f NERC Isotope Geosciences Laboratory, Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG, UK abstract article info Article history: Received 21 January 2012 Accepted 15 March 2012 Available online xxxx Keywords: Circum-Superior Superior Province Mantle plume Proterozoic Geochemistry The ca. 1880 Ma Circum-Superior Large Igneous Province (LIP) consists of a number of discontinuous seg- ments known to cover a significant portion of the margin of the Superior Province craton in North America. New geochemical and isotopic data from western segments of this LIP support a common origin for the these segments and suggest that magmatism in the Lake Superior region may have been fed through the ~ 600 km long Pickle Crow dyke from a source north of the Fox River Belt in northeastern Manitoba. The Fox River Belt, Pickle Crow dyke and sections of the Hemlock Formation in the Lake Superior region possess trace element signatures which are similar to those of more recent oceanic plateaux. The Hemlock Formation displays a het- erogeneous geochemical signature. This chemical heterogeneity can in part be explained by lithospheric con- tamination and possibly by source heterogeneity. The tectonomagmatic setting in which these igneous rocks were formed could have involved a mantle plume. Evidence supporting a plume origin includes high MgO volcanic rocks, high calculated degrees of partial melting and geochemical signatures similar to those of oce- anic plateaux. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The Canadian Shield consists of an amalgamation of Archaean cra- tons and Proterozoic orogens (Hoffman, 1988). The largest craton in the Canadian Shield is the Superior Province which covers an area of up to ~2.4×10 6 km 2 (Card, 1990; Kerrich et al., 1999; Percival and Easton, 2007; Stott, 1997) and is also the largest of the ~35 known cratons worldwide (Bleeker, 2003). The geological assemblage of the Superior Province is comprised of volcano-plutonic, metasedimen- tary, plutonic and high-grade gneiss subprovinces but also includes a number of greenstone belts and mafic dyke swarms (Buchan and Ernst, 2004; Card, 1990) which are of possible mantle plume origin (Ernst and Buchan, 2003). Additionally, a series of igneous rocks are also found around the Superior Province margins over a composite strike length of ~3000 km (Fig. 1). These marginal igneous suites of the Superior Province are mostly ultramafic–mafic volcanic rocks and sills and were grouped together by Baragar and Scoates (1981) into what they called the Circum- Superior Belt because of their lithological, stratigraphical, gravitation- al and magnetic similarities. More recent U–Pb zircon/baddeleyite geochronology has shown that these igneous rocks are essentially co- eval, with the majority of magmatism occurring between 1885 and 1870 Ma (see Ernst and Buchan, 2004; Heaman et al., 2009; Rukhlov and Bell, 2010). The extent and short duration of this magmatism and the recognition of several coeval mafic dykes and carbonatite complexes within the craton interior prompted Ernst and Bleeker (2010) to classify the magmatic rocks as a large igneous province (LIP). This study shall hereafter refer to this LIP as the Circum-Superior LIP. A lack of modern, high-quality whole-rock major and trace ele- ment and isotopic geochemical data from many segments of this Circum-Superior LIP has hitherto hindered attempts to assess if the various segments can be correlated and have a common magmatic origin. Therefore this paper presents new elemental and isotopic data from igneous segments on the western side of the Superior Province, namely the Fox River Belt in northeastern Manitoba, the Pickle Crow dyke stretching across most of Ontario and the Hemlock Formation within the Marquette Range Supergroup in the Lake Superior region (Fig. 1). The main objective of this study is to charac- terise the geochemical and isotopic compositions of the mantle Lithos xxx (2012) xxx–xxx ⁎ Corresponding author. Tel.: + 44 2920 874991. E-mail address: minifiemj@cf.ac.uk (M.J. Minifie). LITHOS-02667; No of Pages 19 0024-4937/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.lithos.2012.03.017 Contents lists available at SciVerse ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Please cite this article as: Minifie, M.J., et al., The northern and southern sections of the western ca. 1880 Ma Circum-Superior Large Igneous Province, North America: The Pickle Crow..., Lithos (2012), doi:10.1016/j.lithos.2012.03.017