The Paleoproterozoic Hurwitz Group of the western Churchill Province is an erosional remnant of an areally extensive, predominantly shallow-water intracratonic basin comprised of four major sequences. Sequence 2, forming the central part of the stratigraphy, contains the Ameto Formation, a sequence of pillowed and massive basaltic rocks and associated gabbro sills termed the Happotiyik Member that are interlayered with subordinate deep-water mudstones, siltstones, and diamictites. Whole-rock geochemical data for the mafic rocks reveals a suite of homogeneous tholeiitic basalts with affinities to both continental and volcanic-arc tholeiites. Compatible trace elements and large-ion lithophile elements exhibit scattered behavior, whereas all high field strength elements show a systematic increase with Zr. The rocks are large-ion lithophile and light rare-earth element enriched, and have parallel primitive mantle normalized extended trace element patterns with prominent negative Nb, Ta, and Ti anomalies. ε Nd(t=2200 Ma) values for the rocks range from 0.0 to +0.8. The data indicate that the parental magmas were derived from a heterogeneous, predominantly depleted mantle source that included a minor metasomatically enriched component. Contamination by Neoarchean, juvenile silicic upper crust during ascent was minimal. We envisage that the rocks of the Happotiyik Member were generated from sub-continental lithospheric mantle that was stabilized immediately after formation of the ca. 2680 Ma, Neoarchean Central Hearne sub-domain. This enrichment occurred via metasomatic infiltration of subduction-derived fluids and melts into the overlying lithosphere. A wide range of Paleoproterozoic intra-continental mafic rocks in the western Churchill Province exhibit comparable geochemical and isotopic signatures that suggest an origin in the lithospheric mantle. These observations imply that the Hearne sub-continental lithospheric mantle has endured since the Neoarchean and likely persists today. 1237Résumé : Le Groupe de Hurwitz (Paléoprotérozoïque) de la Province de Churchill occidentale est un lambeau d'érosion d'un bassin intracratonique, de grande étendue et principalement d'eau peu profonde comprenant quatre grandes séquences. La séquence 2, formant la partie centrale de la stratigraphie, comprend la Formation d'Ameto, une séquence de roches basaltiques de laves massives et à coussins ainsi que des filons-couches associés de gabbro, formant le membre de Happotiyik, qui sont interlités avec des mudstones, des microgrès et des diamictites secondaires d'eau profonde. Des données géochimiques des roches mafiques, pour la roche entière, révèlent une suite de basaltes homogènes tholéiitiques avec des affinités à des tholéiites, et continentales et d'arc volcanique. Des éléments traces compatibles et des éléments lithophiles à grand rayon ionique (LILE, large-ion lithophile elements) ont un comportement erratique, alors que les éléments à champ électrostatique élevé (HFSE, high field strength elements) augmentent systématiquement a...

Basaltic and gabbroic rocks of the Ameto Formation comprise part of the Paleoproterozoic Hurwitz Group and are considered to be 2111 Ma, based on their correlation with Hurwitz Group gabbros southwest of the study area. Volcanic rocks are locally pillowed and are interlayered with mudstone, siltstone, and diamictite, all cut by gabbroic sills. Igneous rocks preserve variably developed foliations and a low-grade metamorphic mineral assemblage implying deformation and metamorphism at greenschist facies. Major-, trace-, and rare-earth-element geochemical data demonstrate a homogeneous suite of tholeiitic basalts with affinities to both continental and volcanic-arc tholeiites. The gabbroic rocks are intrusive equivalents of the basalts. Values of eNd(2.111 Ga) range from -0.54 to +0.25 and yield TDM ages of 2598 to 2508 Ma. The combined data suggest that parental magmas were at least in part derived from a metasomatically enriched mantle source and that metasomatism occurred immediately after accretion of the Neoarchean Kaminak greenstone belt.