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Integrated mapping, structural analysis, and U-Pb geochronology of the Committee Bay area, Nunavut, establish a record of Neoarchean crustal growth followed by penetrative Paleoproterozoic deformation. Supracrustal rocks include a lower ca. 2.73 Ga mafic-ultramafic volcanic-dominated sequence, a middle, economically significant 2.71 Ga intermediate volcanic-bearing sequence with intercalated sulphidized, gold-bearing iron formation, and an upper Une cartographie integree, une analyse structurale et de la geochronologie U-Pb de la region de la baie Committee, au Nunavut, ont permis de determiner la croissance de la croute au Neoarcheen, laquelle a ete suivie d'une deformation penetrante au Paleoproterozoique. Les roches supracrustales comprennent une sequence inferieure, vers 2,73 Ga, mafiqueultramafique dominee par des volcaniques, une sequence mediane, d'interet economique, vers 2,71 Ga, de roches volcaniques intermediaires avec interstratification d'une formation sulfurisee de fer aurifere et une sequence superieure clastique ± komatiite-quartzique,, Introduction Archean supracrustal belts are the most significant hosts of mineral resources within the Precambrian Canadian Shield. As such, their stratigraphic, structural, and chronological characteristics elucidate the context for interpreting [...]

Ophiolitic rocks emplaced following closure of the Ordovician Iapetus Ocean outcrop around the western margins of Notre Dame Bay in western Newfoundland. Previous geological and geophysical models have interpreted the Betts Cove Ophiolite Complex (BCO) as a series of imbricate thrust slices. A new three-dimensional (3-D) model indicates that locally the BCO has the form of a northeast-trending doubly plunging syncline that was later segmented by a series of normal and high-angle reverse faults. This segmentation is interpreted in terms of a Carboniferous graben structure that is responsible for the current morphology of the Notre Dame Bay. The 3-D model incorporates new high-resolution aeromagnetic, marine magnetic, and topographic imagery. In addition, newly available structural information is used to both constrain the geometry of the geological contacts in the near surface and to map contacts in the subsurface. Calibration of the computed geophysical models was achieved using newly acquired magnetic susceptibility data. The resulting 3-D model, which is compatible with all aspects of the geological and geophysical data, provides an explanation for the distribution of Ordovician ophiolites around Notre Dame Bay. Les roches ophiolitiques mises en place apres la fermeture de l'ocean Iapetus (Ordovicien) affleurent autour des bordures occidentales de la baie Notre Dame dans l'ouest de Terre-Neuve. Des modeles geologiques et geophysiques anteerieurs ont interprete le complexe ophiolitique de Betts Cove comme une seerie d'eecailles imbriquees. Un nouveau modele 3-D indique que localement le complexe ophiolitique de Betts Cove a la forme d'un synclinal de direction nord-est, a double plongement, qui a ete par la suite recoupe par une seerie de failles normales et de failles inverses a fort pendage. Cette segmentation est interpretee en tant qu'une structure de graben, produite au Carbonifere, et responsable de la morphologie actuelle de la baie Notre Dame. Le modele 3-D incorpore une nouvelle imagerie aeromagneetique, magnetique marine et topographique a haute resolution. De plus, de l'information structurale nouvellement disponible est utiliseea la fois pour encadrer la geometrie des contacts geologiques pres de la surface et pour cartographier les contacts plus en profondeur. Les modeles geophysiques calculees ont ete etalonnees au moyen de donnees de susceptibilite magnetique nouvellement acquises. Le modele 3-D qui en decoule, lequel est compatible avec tous les aspects des donnees geologiques et geophysiques, explique la distribution des ophiolites ordoviciennes autour de la baie Notre Dame. [Traduit par la Redaction], Introduction The Betts Cove Ophiolite Complex (BCO), located on the eastern shore of the Baie Verte Peninsula (BVP) in northwestern Newfoundland, is one of several ophiolite bodies that are found [...]

Abstract: Five discrete accretionary events assembled fragments of continental and oceanic crust into a coherent Superior craton by 2.60 Ga. They exhibit similar sequences of events at ~10 million year [...]

Abstract: The western Superior Province sustained rapid crustal growth in the interval 2.72-2.68 Ga through amalgamation of microcontinental crustal blocks and juvenile oceanic terranes. Recent field, isotopic, and geophysical surveys [...]

Abstract: Recent advances in the use of Geographic Information Systems (GIS) software and analysis can be used in conjunction with traditional geoscience data sets to determine effective predictors for gold [...]

Abstract: New field work, U-Pb ages, geochemical data, and Sm-Nd isotopic analyses have established the timing and determined the nature of volcanism, deformation, and tectonic assembly of the Pickle Lake [...]

Plate-tectonic models of the Superior province are rooted in the granite-greenstone and metasedimentary belts of the southern part of the craton. North-striking domains of the Minto block in the northeastern part of the province evolved at similar times, in 3.1-2.8, 2.725, and 2.69 Ga events, requiring expansion of models of late Archean assembly to accommodate Minto geology. Western and eastern protocratons ([approximately] 3.1-2.8 Ga) rifted at [approximately] 2.79 Ga to produce an ocean basin that was mostly consumed by subduction at 2.725 Ga. The LeafRiver plutonic suite of calc-alkalic hornblende + biotite [+ or -] orthopyroxene [+ or -] clinopyroxene granodiorite represents magmatic arcs built on the protocratons, whereas the intervening Goudalie domain - containing fault-bounded fragments of rifted continental crust, rift volcanics, primitive oceanic crust, 2724 Ma island-arc rocks, and a < 2718 Ma back-arc assemblage - marks the suture. Terminal collision at [approximately] 2.7 Ga led to thickening and crustally derived granitoid magmatism. The southern Superior province also experienced vigorous activity between 2.725 and 2.69 Ga as island arcs, oceanic plateaus, continental fragments, and accretionary prisms were amalgamated progressively from north to south in a regime of dextral transpression then stitched by granites. A northern proto-Superior craton had continental magmatic arcs built on its eastern and southern flanks in response to west-northwest-directed subduction; orthogonal convergence in the east produced wide plutonic arcs, in contrast to terrane-accretion tectonics in the more oblique regime along the southern margin.

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The Goldcorp High-Grade zone at the Red Lake mine has reserves (proven and probable) established at 1.775 million tons (Mt) at an average grade of 80.6 g/t Au. New U-Pb geochronologic data combined with detailed mapping and crosscutting relationships provide timing constraints and new insights into the formation of the exceptionally rich Goldcorp High-Grade zone. The results show that the main stage of the high-grade mineralization in the High-Grade zone formed before 2712 Ma and that a second stage of gold mineralization, much smaller in terms of total gold content but spectacular in terms of grade, formed after 2702 Ma. This second stage is attributed to gold remobilization caused by the enhanced thermal gradient and deformation associated with the emplacement of the Cat Island pluton (2699 Ma), approximately 7 km east of the deposit, or by the ca. 2.63 to 2.66 Ga postorogenic regional thermal event indicated by hornblende, muscovite, and biotite Ar-Ar cooling ages from the Uchi subprovince. It is proposed that the main stage of high-grade mineralization formed between ca. 2723 to 2712 Ma, possibly synchronous with emplacement of the Dome and McKenzie Island stocks, the Abino granodiorite, and Hammell Lake batholith, as well as with penetrative D2 main-stage regional deformation. Lamprophyre dikes spatially associated with the deposit postdate main-stage mineralization by at least 10 m.y. A postore granodiorite dike from the Madsen mine, the second largest deposit in the district, was dated at 2698 ± 1 Ma. This age is similar to a postalteration and late-deformation diorite dike at the Creek zone showing near the former Starratt-Olsen mine, which was dated at 2696 ± 2 Ma. The crosscutting relationships confirm that the main stage of mineralization at the Madsen mine is pre-2698 Ma. A folded and metamorphosed polymictic conglomerate located stratigraphically above the Campbell-Red Lake deposit, and deposited after ca. 2747 but before... [ABSTRACT FROM AUTHOR]

Integrated mapping, structural analysis, and U-Pb geochronology of the Committee Bay area, Nunavut, establish a record of Neoarchean crustal growth followed by penetrative Paleoproterozoic deformation. Supracrustal rocks include a lower ca. 2.73 Ga mafic-ultramafic volcanic-dominated sequence, a middle, economically significant 2.71 Ga intermediate volcanic-bearing sequence with intercalated sulphidized, gold-bearing iron formation, and an upper <2.69 Ga clastic ± komatiite-quartzite sequence. Following an 80 million year hiatus, this succession was intruded by voluminous ca. 2.61-2.57 Ga granodiorite-tonalite-granite ± diorite, which do not appear to have thermally or tectonically affected the supracrustal belt. Instead, three generations of structures record polyphase Paleoproterozoic deformation of the region. D1 structures are consistent with a doubly vergent structural fan developed at ca. 2.35 Ga in response to the Arrowsmith orogeny that affected the western Rae margin. Penetrative D2 structures dominate the map pattern and include northeast-trending, southeast-dipping folds and fabrics within which gold is localized. The general southeast dips of S2 and inclined, northwest-vergent attitude of F2 reflect northwest-directed shortening at 1.84-1.82 Ga. The absence of syn-D2 plutonic rocks in the west and central Committee Bay belt support amphibolite-facies metamorphism as a response to crustal thickening, which, in turn, led to syn-D2 crustal melting in the east. Regionally extensive upright to northwest-vergent D2 structures and associated ca. 1.85-1.82 Ga tectonometamorphism across the Rae craton are attributed to an early stage of the Hudsonian orogeny involving microcontinent collision(s) with its southeastern margin. D3 folds and dextral shearing at ca. 1780 Ma accommodated localized, late-stage compressional strain during final amalgamation of Laurentia. [ABSTRACT FROM AUTHOR]

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]

Laser ablation inductively coupled plasma multi-collector mass spectrometry (LA-MC-ICP-MS) allows rapid, in situ, highly precise measurements of Cu isotope ratios of native Cu and Cu-bearing minerals. However, the National Institute of Standards and Technology Cu-metal isotope standard NIST SRM976 that is commonly used to calibrate LA-MC-ICP-MS Cu isotope measurements of native Cu is no longer available. We have investigated the suitability of four Cu metal materials, SSC-1, SSC-3 and SSC-4 (cathode Cu metal rods) and CUPD-1 (Cu anode sawings), originally developed by the Canada Centre for Mineral and Energy Technology (CANMET) as certified reference materials for trace element analysis, as Cu isotope reference materials for LA-MC-ICP-MS analysis and solution nebulization (SN) of Cu. The Cu isotopic composition and homogeneity of these four materials were characterised by SN- and LA-MC-ICP-MS, and are reported for the first time. The bulk Cu isotopic compositions, expressed as δ 65 Cu SRM976 in per mil (‰) relative to NIST SRM976 with combined uncertainties ( U , k = 2), of SSC-1, SSC-3 and SSC-4, determined utilizing SN-MC-ICP-MS, are identical within analytical uncertainty at 0.03 ± 0.07‰ ( n = 29), 0.04 ± 0.04‰ ( n = 28), and 0.05 ± 0.08‰ ( n = 29), respectively; the composition of CUPD-1 is 2.14 ± 0.08‰ ( n = 28). The compositions are 0.01 ± 0.07‰ ( n = 29), 0.04 ± 0.06‰ ( n = 29), 0.03 ± 0.06‰ ( n = 28) and 2.15 ± 0.06‰ ( n = 28), respectively, relative to the European Reference Material ERM®-AE633 Cu isotope standard. The Cu isotope homogeneity of the four new reference materials was assessed by determining whether multiple individual in situ Cu isotope measurements made by LA-MC-ICP-MS analysis (43 µm spot size), using each of the other three reference materials as a calibrator, approximate a single normal distribution. We also investigate whether there are statistically significant differences between the mean δ 65 Cu values of three independent data sets for each of the Cu isotope reference materials using one-way analysis of variance (ANOVA). Normality tests (graphical assessment of normal distribution quantile-quantile plots, and the Shapiro-Wilk, Jarque-Bera and reduced chi-squared statistic tests) show that: 1) the Cu isotope data acquired on SSC-1, SSC-3, SSC-4 and CUPD-1 do not depart significantly from a normal distribution, 2) the scatter of the Cu isotope data is due to analytical uncertainty with 95% confidence, and 3) there are no other significant sources of scatter; e.g. heterogeneity of the reference materials. The results of one-way ANOVA reveal that the mean difference of the δ 65 Cu value for each of the reference materials SSC-1, SSC-3, SSC-4 and CUPD-1 is statistically not significant at the 0.05 level. The mean δ 65 Cu SRM976 values with combined uncertainties ( U , k = 2) of SSC-1, SSC-3, SSC-4 and CUPD-1, determined by LA-MC-ICP-MS using each of the other three reference materials as a calibration standard, are 0.03 ± 0.09‰ ( n = 132), 0.05 ± 0.09‰ ( n = 154), 0.03 ± 0.09‰ ( n = 144) and 2.14 ± 0.10‰ ( n = 106), respectively. These values are in agreement with those determined by SN-MC-ICP-MS analysis at the 95% confidence level and have excellent precision (2 s.d. ≤ 0.10‰). These results suggest that SSC-1, SSC-3, SSC-4 and CUPD-1 can be considered isotopically homogeneous at a spatial resolution of 43 μm, and they are suitable reference materials for calibration and quality control of in situ and solution nebulization Cu isotope analyses of Cu., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Yang, Jackson and Skulski.)