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The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost 1 km below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation, which is only observed in shallow samples from the Triple R deposit (Tur 1), contain the heaviest isotopic signature (δ 11B ≈ 19–26‰), whereas subsequent generations (Tur 2 and Tur 3) yield lighter and more homogeneous isotopic signatures (δ 11B ≈ 17.5–19.9‰). These results are consistent with precipitation from low-temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ 11B values). The lower δ 11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time, whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ 11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact. Supplementary material: Complete analytical dataset including reference materials are available at https://doi.org/10.6084/m9.figshare.c.5727555 Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways [ABSTRACT FROM AUTHOR]

U-Pb ages of zircon from bentonites within the upper Cretaceous Bastion Ridge and Kanguk formations, Sverdrup Basin, provide constraints on sedimentation rates, biostratigraphic correlations, timing of Oceanic Anoxic Event 2 (OAE2) in the High Arctic, and the late magmatic history of the High Arctic Large Igneous Province (HALIP). A late Cenomanian to early Turonian age for the base of the Kanguk Formation is confirmed that supports correlations of the global OAE2 in the High Arctic. Sedimentation rates varied from 19 m Ma-1 between 93 and 91 Ma to 26 m Ma-1 between 91 and 83 Ma at Axel Heiberg Island. At Ellef Ringnes Island, the lower Kanguk Formation records high rates of ~70 mMa-1 between 94 and 93 Ma, which decrease to rates comparable to those of the upper Axel Heiberg section. Differences in sedimentation rates may reflect differences in setting prior to the major transgression in the latest Cenomanian to early Turonian. The timing of Arctic occurrences of the Scaphites nigricollensis and Scaphites depressus ammonite zones is shown to be broadly comparable to that of lower-latitude occurrences within the Western Interior Seaway. An eruption frequency of 0.5-2.5 Ma characterizes the late alkaline phase of HALIP magmatism. Volcanic bed thicknesses of 10-50 cm suggest ash transport distances of less than 1000 km. Long-lived volcanic centres, in the area of the Alpha Ridge, northern Ellesmere Island or northern Greenland, were the likely source of volcanic ash over a period of 10-15 Ma. [ABSTRACT FROM AUTHOR]

Paleoproterozoic metasedimentary successions of the northwestern Canadian Shield provide records of tectonic events, but the definition of depositional ages has proved elusive. Although previously poorly understood, the Montresor belt of western Nunavut yields new insight into the 2.2-1.8 Ga time window. On the basis of U-Pb analyses of detrital zircon in sedimentary rocks and igneous zircon in sills, we conclude that arenite of the lower Montresor group was deposited between 2.194 and 2.045 Ga, and arkose of the upper Montresor group after 1.924 Ga, adding constraints on the Rae cover sequence. The lower Montresor arenite yielded an older group (3.05-2.58 Ga) and a younger, more tightly constrained group (2.194 ± 0.014 Ga). Four of six zircon grains analyzed from a gabbro sill within the lower Montresor have discordant 207Pb/206Pb ages (2.71, 2.66, 2.53, and 2.39 Ga) and are considered to be inherited, whereas two grains provide an age of 2045 ± 13 Ma, interpreted to date crystallization and providing a minimum age for the lower Montresor package. Upper Montresor arkose contains detrital zircon with probability density peaks at 2.55-2.25 and 2.1-1.92 Ga, together with scattered older grains (3.8-2.65 Ga). The youngest grain yields an age of 1924 ± 6 Ma, establishing a maximum age for sandstone deposition. Provenance is inferred to have been from the west, where igneous sources of 2.5-2.3 Ga (Queen Maud block) and 2.03-1.89 Ga (Thelon orogen) are known. Collectively, the new ages suggest a minimum 120 million year gap between deposition of the pre-2045 ± 13 Ma lower and post-1924 ± 6 Ma upper parts of the Montresor group. Similar age constraints may apply to other parts of the Rae cover sequence. [ABSTRACT FROM AUTHOR]

Abstract: New geological and geochronological data from the MacQuoid supracrustal belt and the geometrically overlying Cross Bay plutonic complex highlight a distinct tectonothermal evolution for the northwestern part of the Hearne domain (northwestern Hearne subdomain), compared with adjacent areas in the Rae and Hearne, of the western Churchill Province, Canada. The supracrustal and intrusive rocks dominantly formed in the Neoarchean between <2.74 and 2.65Ga, with minor 2.61Ga granite, and experienced a polycyclic Neoarchean and Paleoproterozoic deformational history. The dominant tectonic fabric throughout much of the area formed between 2.56 and 2.50Ga, including the Big Lake shear zone, a granulite-facies mylonite zone that juxtaposed the Cross Bay plutonic complex over the MacQuoid supracrustal belt at 2.50Ga. The fabric transposed earlier fabrics whose age is poorly constrained. Additional tectonic events occurred during the Paleoproterozoic at 1.90Ga, and 1.84–1.81Ga. Differences between the geological histories of the northwestern part of the Hearne domain relative to the immediately adjacent Rae and Hearne areas highlight the tectonically distinct character of the northwestern Hearne subdomain. [Copyright &y& Elsevier]

The origin and nature of fluids responsible for U deposits of the Athabasca Basin have been in debate. This study presents the trace element abundances and stable isotope ratios (D/H and 11 B/ 10 B) of well characterized tourmaline samples determined by in situ analytical techniques, in order to evaluate the nature of fluids during the mineralization of the McArthur River U deposit, the world's largest high-grade U deposit. Magnesio-foitite, an alkali-deficient Mg-rich tourmaline, is abundant along the 13-km long P2 fault, a reverse structure that controls the location of the McArthur River deposit. Magnesio-foitite contains variable concentrations of rare earth elements (REEs, up to 46 ppm in total) and Y (up to 35 ppm). Chondrite normalized patterns indicate low light REEs (LREEs) relative to heavy REEs (HREEs) (Ce N < Y N , Y as a proxy for HREEs) and slight negative Eu anomalies, similar to those of uraninite from the deposit. The data combined with textural evidence suggest that magnesio-foitite and uraninite co-crystallized with LREE-rich aluminum phosphate sulfate minerals. Relatively high REE contents of magnesio-foitite in the ore zone indicates the incursion of a REE-rich basement fluid. Low values of δD (− 98 to − 41‰) for magnesio-foitite suggests that the mineralizing fluid originated from groundwater. Variably high values of δ 11 B (+ 13.1 to + 23.2‰) are explained by the dissolution of B from carbonate or evaporitic rocks and preferential removal of 10 B by the crystallization of illite and kaolinite. The results of this study support the ascent of a REE-rich basement fluid during mineralization and extensive modification of basinal fluids through the crystallization of clay minerals. [ABSTRACT FROM AUTHOR]

The Taltson magmatic and Thelon tectonic zones have historically been considered parts of a single orogen recording collision between the Slave craton and Buffalo Head terrane to the Rae craton between 2.0 and 1.9 Ga. The Taltson–Thelon connection stemmed from recognition that the Taltson magmatic zone coincides with the Taltson aeromagnetic high that extends northward and merges with the Thelon aeromagnetic high. Analysis of geophysical data in this study, however, coupled with recent mapping, indicates that this magnetic high is underlain in large part by rocks of Taltson basement complex. In addition, both basement rocks and Taltson-age plutons can be traced eastward into northern Saskatchewan, below Athabasca Basin cover, and reappear/re-emerge to the south where they are truncated by the Virgin River shear zone (Snowbird tectonic zone). This paper presents new field, geochronological and geochemical data for the Lloyd domain of Saskatchewan bearing on the extent and nature of the Taltson orogen. The Lloyd domain is underlain mainly by magnetic dioritic–granodioritic orthogneisses and subordinate supracrustal rocks. It also hosts the Clearwater anorthosite complex, a ∼300 km 2 , northeast-elongate gabbro-anorthosite intrusion about 15 km northwest of the Virgin River shear zone. While previous geochronology established that some Lloyd domain orthogneisses are of Taltson (i.e., 1.98 Ga) age, geochronology presented herein has identified an appreciably older (ca. 2460 Ma) component. Geochemical study indicates that these older metaplutonic gneisses are distinguishable from younger (Taltson-age) ones based on trace element characteristics, but the true extent of basement rocks is impossible to evaluate. U–Pb geochronological data from the Clearwater anorthosite complex are complicated but allow interpretation that it was emplaced into this older basement complex at ca. 2.1 Ga and was subsequently metamorphosed during Snowbird orogenesis at ca. 1.9 Ga. Geochemical study also indicates that the Taltson-age quartz dioritic to granodiorite suite in Lloyd domain is chemically related but less evolved than the younger dominantly granitic, Taltson magmatic zone plutons of Alberta and N.W.T. The two are interpreted to be related and reflect gradual evolution of a subduction-related continental magmatic arc, challenging previous models invoking intra-plate magmatism. Collectively, these data, along with regional geological relationships, indicate that the Taltson orogen originally trended northwest–southeast and is a unique tectonic entity, distinct from the Thelon tectonic zone. Two alternative models are provided for Taltson orogeny. In the first, the Thelon orogeny develops along the margin of the Slave craton due to accretion of the Buffalo Head terrane between 2.0 and 1.95 Ga. In the meantime, the Taltson arc was built on the southwest margin of the Rae province as the now combined Slave craton and Buffalo Head terrane approached. Terminal collision of the Rae and Slave culminated with high-grade metamorphism between 1.94 and 1.93 Ga. In the second, the Slave craton was attached to the Rae craton far in advance of the Taltson orogeny, perhaps during the ca. 2.5–2.3 Ga Arrowsmith orogeny. In this model, the Taltson orogeny developed on the southwest margin of the amalgamated Rae-Slave craton due to accretion of the Buffalo Head terrane and the Thelon tectonic zone represents an intracontinental zone of reworking. [ABSTRACT FROM AUTHOR]

This paper documents element mobility patterns from a magnetite-group Iron Oxide Copper–Gold (IOCG) prospect in the Northwest Territories of Canada and explores implications for space–time chemical evolution of metasomatic systems hosting IOCG deposits. The Fab system, located in the Great Bear magmatic zone (GBMZ) of the Northwest Territories, Canada, contains numerous Fe–Cu–U showings associated with high temperature (HT) potassic–iron alteration overprinting extensive zones of sodic to HT calcic–iron alteration. Each hydrothermal alteration assemblage is associated with distinct element mobility patterns that record evolving physico-chemical properties of the hydrothermal fluids. New geochronological data constrain the alteration and IOCG mineralization in the Fab system to a 3 m.y. window between 1870–1867 Ma, which is broadly contemporaneous with extensive high-level intrusive activity across the GBMZ. Regional- to local-scale element mobility patterns characteristic of the sodic and sodic–calcic–iron alteration type record leaching combined with weak to strong mass losses. Pure sodic alteration depleted the rocks in Ca, Co, Cu, Fe, Mg, Th, U and V. Conversely, sodic–calcic–iron alteration records significant depletions of Nb, REE, Ta, Ti, Th and U. These element mobility patterns differ from intense HT calcic–iron alteration that is enriched in Ca, Co, F, Fe, Mg, Mn, Ni and V with modest enrichments to locally significant mineralization in Th, U and REE. HT calcic–iron alteration is also characterized by substantial mass gains that translate into volume gains in stockwork zones and mass/volume gains in zones of intense host rock replacement. HT potassic–iron alteration is characterized by enrichments in Ba, K, Ni, U and V, along with locally Co and Cu. The temporal and spatial association of the Fab system alteration and the emplacement of the porphyritic dacite are indicative of the predominant involvement of magmatic–hydrothermal fluids. The high F- and Cl- contents of the porphyritic dacite and of the HT calcic–iron alteration zones as well as Nb, REE, Ta, Th, and Ti mobility provide strong evidences of high halogen activities (F and Cl) in the hydrothermal fluids. High F- and Cl-activities in the hydrothermal fluid are interpreted to have facilitated the mobilization of normally immobile (Nb, Ta, Ti, Th) or weakly mobile elements as well as some metals (e.g., V, Ni, Co). The formation of REE fluorocarbonates and calcite in the early and incipient HT calcic–iron alteration zones indicates the presence of CO 2 in the hydrothermal fluids. Weaker HFSE, HREE and Ti mobility during later HT potassic–iron alteration is interpreted to reflect decreasing temperatures, pressures, F-activities and increasing f O 2 as the fluids evolved and interacted with the host rocks. [ABSTRACT FROM AUTHOR]

Abstract: The reconstruction of the paleocontinental configuration involving ancestral North America (Laurentia) at the Paleoproterozoic–Mesoproterozoic boundary has been developed in the last 30 years with different scenarios being proposed and different combinations of landmasses assembled together. However, the lack of information for the northwestern side of the North American craton has so far been an obstacle for the complete paleocontinental reconstruction and its tectonic history. Here we provide new age determinations on rocks of the Wernecke Supergroup and of the Wernecke Breccia of the Wernecke Mountains in Yukon to provide a more complete picture of the entire North American craton and its possible conterminous at 1600Ma. The six youngest U–Pb ages of the detrital zircon from quartz sandstones of the Wernecke Supergroup suggest that the sedimentary succession is as old as 1640Ma. Lu–Hf garnet ages on garnet bearing schists of the Fairchild Lake Group (lower Wernecke Supergroup) give a bimodal population of ages of approximately 1600Ma and 1370Ma: the first age is related to the Racklan Orogeny, and the younger event is likely attributable to a reheating episode (Hart River Sills emplacement). The younger age of the Wernecke Supergroup puts into question the previous model concerning the emplacement of the Bonnet Plume River Intrusions, and requires the development of a new tectonic model for the northwestern margin of Laurentia. This new model involves obduction of an exotic terrane on top of the Wernecke Supergroup during the latest phases of the Racklan Orogeny (ca. 1600Ma). This exotic terrane, herein called Bonnetia, contains rocks of the Bonnet Plume River intrusions and of the Slab volcanics. During the hydrothermal event that led to the emplacement of the Wernecke Breccia, clasts and megaclasts of the overlying Bonnetia foundered down to the breccia pipes to the level of the Wernecke Supergroup, and this dynamic explains the existence of older rocks engulfed within a younger sedimentary succession. The Racklan Orogeny is now interpreted as a northwestern expression of the Mazatzal Orogeny of southwestern United States, and of the Labradorian Orogeny of eastern Canada which was in turn connected with the Gothian Orogeny of Scandinavia. The connection among these orogenic events makes plausible the hypothesis of a circum-Laurentian orogenic belt with possible extensions in other landmasses (Australia, Antarctica, Siberia, or China) where coeval deformation belts are present. [Copyright &y& Elsevier]

Abstract: Cretaceous sediments in the Northern Interior Plains are widespread and their interbasinal lithostratigraphic correlations indicate several regional unconformities that require biostratigraphic confirmation. This study proposes a new zonation based on benthic foraminifera utilising the reference section for the Albian to Turonian Arctic Red and Trevor formations located along the Hume River in the Peel Plateau region (Northwest Territories). A new absolute age date of 107.0±1.9Ma from a bentonite extends the biostratigraphic range of the Early Albian Quadrimorphina albertensis Zone into the Middle Albian. Integration of the new temporal framework with detailed sedimentological observations provides an interpretation of the dynamic depositional history for this northern region of the Western Interior Seaway (WIS). Cretaceous strata in the Peel Plateau record deposition of the initial transgression of the WIS in two pulses of relative sea-level rise (Martin House Formation) and subsequent offshore marine sedimentation in a deep foreland basin (Arctic Red Formation). The global eustatic sea-level minimum at the Albian–Cenomanian boundary and renewed uplift of the Keele Arch impacted palaeogeography in this region with previously unnoticed subaerial exposure and palaeosol development. This unconformity can be correlated to the east into the Mackenzie Plain. Transgression brings anoxic bottom waters during the Early Cenomanian (Slater River Formation) that result in an interval almost barren of foraminifera. During the Turonian, a time of high eustatic sea-level, the study area marks a relatively shallow site where pulses of prograding shorelines are recorded in upward shallowing parasequences bound by pebble lags overlain by flooding surfaces (Trevor Formation). East of the Peel Plateau in the Mackenzie Plain area, an unconformity separates Albian Arctic Red from ?Upper Cenomanian–Turonian strata, there named the Slater River Formation. In order to recognise the significant unconformity associated with the loss of Albian foraminifera and the angular unconformity observed in seismic profile, we propose the use of the Slater River Formation to describe the strata bound by the pisoidal ironstone and the first metre-plus sandstone bed marking the base of the interbedded mudstones and sandstones of the overlying Trevor Formation. The Hume River section is proposed as the type section for the Slater River Formation. [Copyright &y& Elsevier]