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Abstract: The basal Paleoproterozoic supracrustal succession of the Churchill Province in northern Canada comprises sedimentary basins overlying the Archean Rae and Hearne domains. The Rae domain supracrustal succession (e.g. Amer, Ketyet River, Chantrey and Montresor groups) comprises four lithotectonic assemblages which include, in ascending stratigraphic position: (1) shallow marine-fluvial quartzarenite with mainly Neoarchean detrital zircons of local provenance; (2) shallow marine quartzarenite with mainly local provenance that locally includes carbonates±mafic volcanic flows; (3) abrupt but conformable transition to basinal dark shales and overlying platformal carbonates that pass upward into siltstones and sandstones that record gradual emergence of the platform. Sandstones within this assemblage display a substantially different detrital zircon provenance signature dominated by early Paleoproterozoic zircons, with grains as young as 1.95Ga; (4) unconformably to conformably overlying immature marine sandstones, including turbidites, with a significant component of 2.0–1.9Ga detritus probably derived from a combination of local and distal sources. The thickness and relative compositional maturity of the basal lithotectonic assemblage 1 records a protracted period of enhanced weathering on a slowly subsiding but stable supercontinent (e.g. Kenorland). This was followed by mafic volcanism and marine transgression, consistent with partial rifting of the Rae domain and crustal extension attending supercontinent break-up (lithotectonic assemblage 2). Strata of lithotectonic assemblage 3 record basin flooding and deepening followed by platformal sedimentation along the margins of extended continental blocks. Assemblage 4 is interpreted to represent deposition in foreland basins during early amalgamation of Laurentia (part of Nuna) at ca. 1.9Ga. The stratigraphy and detrital zircon geochronology of the Hurwitz Group, which overlies the Hearne domain, is broadly similar to the supracrustal sequence of the Rae domain, but differs through the presence of basal diamictites and lack of 2.5Ga detritus, a major local source in the Rae. Our data suggest that the Rae and Hearne domains were assembled together by max. 1.91Ga (i.e. max. age of deposition of the uppermost Hurwitz and Amer groups). The Paleoproterozoic stratigraphic assemblage framework for the Churchill Province compares well with that of other cratons derived from break-up of Kenorland and ultimately amalgamated in Nuna. Examples from Laurentia include supracrustal rocks that overlie the southern margin of the Superior Province (Southern Province, e.g. Huron Supergroup, Animikie Group, Marquette Range Supergroup, Whitewater Group and Mistassini-Otish Group). The Paleoproterozoic assemblages of the Southern and Churchill provinces exhibit first-order stratigraphic similarities that indicate a shared history of stable continental sedimentation followed by rifting, basin opening and basin closure. [Copyright &y& Elsevier]

Abstract: Petrology and in situ SHRIMP monazite geochronology provide new constraints on the polymetamorphic and polydeformational history of the Committee Bay belt, Rae Province, Nunavut, Canada. Rare ca. 2.58Ga monazite inclusions in garnet porphyroblasts in the eastern part of the belt are interpreted to reflect regional contact metamorphism (M1) associated with voluminous 2.61–2.58Ga plutonism. Monazite also occurs as ca. 2.35Ga inclusions in andalusite in the central supracrustal belt, but is absent from the east. These data complement previous studies to the west, and suggest that the Committee Bay belt represents a ca. 2.35Ga tilted crustal section that was tectonically thickened±imbricated during the Arrowsmith orogeny (D1–M2). Penetrative reworking of the belt occurred during a diachronous D2–M3 tectonometamorphic event which involved northwest-vergent thickening to depths of ∼5kbar across most of the belt. Although D2 folds and fabrics across the belt are geometrically correlative, monazite is ∼20Myr older in the western migmatite domain (ca. 1.86Ga) than in the western supracrustal belt (ca. 1.84Ga). This temporal difference is attributed to burial of more radiogenic lithologies in the migmatite domain. Tectonic thickening is attributed to ca. 1.87Ga collision of Meta Incognita microcontinent with the southeastern flank of the Rae Province. The eastern supracrustal belt exposes similar amphibolite-facies (M3) northeast-striking, northwest-vergent D2 structures that are dated at 1.815Ga. This younger reworking may reflect the influence of a major northward projecting promontory of the Superior Province which continued to affect the softened hinterland of the Rae Province during terminal collision at ca. 1.82Ga. The central Committee Bay belt records a younger, ca. 1.79Ga structural overprinting (D3–M4) which involved dextral shearing and differential burial to temperatures above monazite growth in a gentle synformal structure formed during the final stages of amalgamation of Laurentia. [Copyright &y& Elsevier]

Here we present Re-Os geochronological data from two carbonaceous shale units from the Hornby Bay and Amundsen basins that provide important chronological markers for Mesoproterozoic stratigraphic successions within northern Canada. Shale from the basal Escape Rapids Formation yields a robust depositional age of 1067.3 ± 13.5 Ma for the lowermost Shaler Supergroup of Amundsen basin with a remarkably unradiogenic initial 187Os/188Os value (0.15), implying that it derived from weathering of juvenile source material, such as basalt. Sedimentological features, indicative of large basin conditions, suggest deposition within an extensive epeiric sea that was intermittently mixed with waters from an exterior ocean. This age, and the 720 Ma age of the uppermost Shaler Supergroup, constrain deposition of the ∼4 km-thick succession to a period of approximately 350 myr, recording sedimentation through a complete supercontinent cycle - amalgamation through to break-up of Rodinia. Further, it indicates that the Amundsen basin formed at the same time as the Borden, and Fury and Hecla basins on northern Baffin Island, and the Thule basin in northwestern Greenland, and that these basins were perhaps connected as part of a much larger basin situated in the interior of Rodinia. Diagenetic pyrite from sandstone dykelets in carbonaceous shales of the Fort Confidence Formation yielded a Re-Os model age of 1438 ± 8 Ma, providing a minimum age for deposition of the lower Dismal Lakes Group of the Hornby Bay basin. This age strengthens proposed regional correlation of the Hornby Bay basin with the large intracontinental Athabasca and Thelon basins, located on the Rae craton to the southeast, and is evidence for a Laurentia-wide marine flooding episode ca. 1500 Ma. Both new ages place important constraints on newly discovered eukaryotic microfossils from the Shaler Supergroup and Dismal Lakes Group and calibration points for critical chemostratigraphic data. • New Re-Os isotope ages from Mesoproterozoic successions in northern Canada. • Allow calibration of Rodinia supercontinent cycle. • Improve correlation with Mesoproterozoic sedimentary basins across northern Canada. • Ages constrain newly discovered eukaryotic microfossils from these strata. [ABSTRACT FROM AUTHOR]