The Nolan-Zemlak domain boundary in the southwestern Rae Province separates ca. 2.6 Ga granodioritic to granitic rocks (Nolan suite) of the Nolan lithotectonic domain to the north from an assemblage of ca. 2.52 Ga ultramafic-intermediate plutonic rocks (Zemlak suite) and ca. 2.3 Ga granitoids, and derived gneisses, of the Zemlak domain to the south, the latter representing part of the Taltson basement complex (TBC). The restriction of the Zemlak suite to south of the domain boundary suggests that its emplacement was structurally controlled, an inference supported by recognition of pre-2.52 Ga deformation in Nolan domain. This paper reports the results of U-Pb and Lu-Hf isotopic analysis of zircon, coupled with multi-element whole-rock geochemical analysis, for the Nolan and Zemlak suites, plus a younger suite of leucogranites that stitch the domain boundary. Both the Nolan and Zemlak suites have geochemical-isotopic signatures consistent with subduction-related magmatism, but the ca. 2.52 Ga Zemlak suite is distinguished by anomalously low Th concentrations, attributed to minimal sediment flux into the mantle wedge. Zircon rims from Nolan granites record ca. 2.52 Ga metamorphism ascribed to intrusion of the Zemlak suite. Regionally, these observations are best explained by the subduction-related accretion of the Zemlak terrane, part of a larger Paleo-Mesoarchean crustal block now embedded within the TBC, to a 'proto-Rae' cratonic core. A model is presented wherein circa 2.64-2.58 Ga (Nolan age) continental arc magmatism was generated via north-dipping subduction below the proto-Rae craton leading to eventual collision/accretion of the outboard Paleo-Mesoarchean block. Collisional suturing occurred by ca. 2.57 Ga, as recorded by both local and regional metamorphic ages. Following collision, subduction is inferred to have stepped outward, directed beneath the now amalgamated Nolan and Paleo-Mesoarchean (Zemlak/TBC) terrane with further arc magmatism represented by the ca. 2.52 Ga Zemlak suite. Thereafter, arc magmatism continued along the west-southwest margin of Rae craton from ca. 2.47 Ga to 2.4 Ga, likely the expression of Arrowsmith orogeny. Terminal collision ending the Arrowsmith orogenic cycle resulted in reactivation of the boundary zone and formation of the South Tazin Lake shear zone coeval with 2.37 Ga metamorphism and leucogranite emplacement.

The Murmac Bay group is one of several early supracrustal successions that were deposited on the southern Rae craton, Churchill Province, western Canadian Shield, and subsequently affected by Paleoproterozoic tectono-metamorphism. Where best understood, the succession comprises basal quartzite and/or psammite with intercalated dolostone, patchy iron formation, mafic volcanic flows, and overlying psammopelite-pelite. Previous attempts to date the Murmac Bay group have resulted in both Archean and Paleoproterozoic estimates. Re-interpretation of critical field relationships together with acquisition of new geochronological data have greatly improved estimates for its age of deposition, which in turn yield new constraints on the tectonic evolution of the region. Circa 2.33-2.32 Ga detrital zircon from three of four dated samples, including a rare basal conglomerate, establishes a maximum age for the initiation of deposition. A 2322 +/- 5 Ma quartz-feldspar porphyry dyke intruding mafic volcanic rocks near the base of the succession indicates that deposition of the Murmac Bay group was initiated ca. 2.33 Ga, coeval with the earliest members of a 2.33-2.29 Ga granitic suite. These post-collisional granites were emplaced following a 2.37 Ga thermal culmination attributed to the Arrowsmith orogeny. Deposition of the Murmac Bay group continued until at least 2.17 Ga, the youngest detrital zircon age analyzed from the upper part of the succession. Deposition was over by ca. 1.93 Ga, when the Murmac Bay group underwent regional metamorphism and was intruded by the Donaldson Lake pluton, for which a revised ca. 1.93 Ga crystallization age has been obtained. According to our new age constraints, the upper Murmac Bay group may be temporally correlative with the Waugh Lake group, exposed about 100 km to the west-northwest at the eastern margin of the Taltson Magmatic Zone, and with rocks of the Rutledge River Basin, located 150 km to the northwest. A stronger case can be made for lithostratigraphic correlation of the Murmac Bay group with the lower three of four assemblages in the Amer and Ketyet River groups, 750 km to the northeast. The abundance of ca. 2.17 Ga detrital zircon in the Murmac Bay group, together with the presence of 2.2-2.07 Ga detritus in the Amer and Ketyet River groups, Rutledge River Basin, and in younger sedimentary successions in the region are thought to record an early accretionary event on the western margin of the Rae craton. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.

The Beaverlodge domain is a polydeformed Precambrian terrane in the southwestern Rae craton whose rocks variably record the effects of Archean tectonism and four major Paleoproterozoic tectonic events: the 2.5-2.3 Ga Arrowsmith orogeny, the 1.99-1.93 Ga Taltson orogeny, the ca. 1.90 Ga Snowbird orogeny and the ca. 1.87-1.80 Ga Hudsonian orogeny. Structural-metamorphic analysis and in situ U-Pb SHRIMP zircon and monazite geochronology reported herein demonstrate that this domain consists of two main structural levels variably exposed due to complex interference folding: a lower level comprising mainly high-grade Archean (ca. 3.0 and 2.7-2.6 Ga) metaplutonic and metasedimentary gneisses and a higher level comprising mainly ca. 2.33 to <2.17 Ga supracrustal rocks of the Murmac Bay Group at more variable metamorphic grade. Whereas the older package underwent thermal and/or metamorphic events in the Archean (ca. 2.57 Ga) and early Paleoproterozoic (ca. 2.34 Ga; Arrowsmith orogeny), rocks at higher structural levels bear no record of these events, recording only younger (1.94-1.90 Ga) metamorphism interpreted to reflect two further stages of orogenesis. The first stage, correlated with Taltson orogeny, involved tight to isoclinal folding (D-1/2) that led to development of the composite ESE-trending (S-0/S-1/S-2) transposition foliation followed by more open folding (D-3). The absence of Taltson-age plutonic rocks, except for low-volume crustal melts, suggests that this cycle was driven by crustal thickening, consistent with a clockwise P-T-t path derived for one sample. The high degree of strain along the contact between Archean rocks and the Murmac Bay Group, along with local structural discordance, indicates some degree of translation of cover rocks over basement during this stage. Pelitic rocks at higher structural levels (low- to medium-grade zone) underwent prograde metamorphism to middle amphibolite facies whereas rocks at deeper structural levels (high-grade zone) attained upper amphibolite facies conditions. Monazite data bracket prograde metamorphism (and related garnet growth) between 1939 +/- 6 Ma and 1934 +/- 5 Ma. The second stage, dated most precisely at 1906 +/- 7 Ma, involved refolding of D-1 to D-3 structures about NE-trending axes (F-4) and coeval dextral shearing and is correlated with Snowbird orogenesis. Rocks of the low- to medium-grade zone were held at roughly the same crustal level whereas rocks in the high-grade zone were uplifted via dextral-oblique displacement along domain-bounding shear zones, instigating decompression (garnet to cordierite) reactions. This study demonstrates that after <2.17 Ga deposition of the upper Murmac Bay Group, rocks along the entire west-southwestern Rae margin, from the Northwest Territories/northern Alberta to the Snowbird tectonic zone, were affected by Taltson (1940-1930 Ma) orogenesis. The Taltson tectono-metamorphic cycle then appears to have transitioned, as rocks underwent further shortening and uplift in a dextral transpressive regime, into Snowbird tectonism at ca. 1910-1900 Ma. Snowbird orogenesis is therefore best viewed as part of a semi-continuous 1940-1900 Ma cycle of tectonic burial and exhumation, with its inception at ca. 1910 Ma triggered by a change in boundary conditions, as yet not fully understood, but consistent with arrival of the Hearne craton proposed by others.While the Beaverlodge domain has many features in common with the Tantato domain, future work needs to explore why rocks in the Tantato domain lack evidence for Arrowsmith orogeny and failed to record the cycle of 1.94-1.93 Ga tectonic burial. (C) 2013 Elsevier B.V. All rights reserved.

Geochronological and thermobarometric data for two widely spaced and previously unstudied areas of the Rae craton, Canada provide important temporal and spatial links between previously investigated areas in the northern and southern Rae craton that had been interpreted to have been reworked during wthe ca. 2.5-2.3 Ga Arrowsmith orogeny. On southern Boothia Peninsula, upper amphibolite- to granulite-facies metamorphism, dated by in situ SHRIMP U-Pb analysis of monazite, occurred at ca. 2.64-2.60, 2.54, 2.50-2.49, 2.44, and 2.37-2.34 Ga, with retrograde monazite growth at 2.27 Ga. SHRIMP U-Pb ages of zircon in two metasedimentary rocks provide a further indication of metamorphism at ca. 2.54 and 2.50 Ga, which also corresponds to the age determined for a K-feldspar augen granite. Textural relationships indicate that the regional foliation formed between ca. 2.54 Ga and 2.50-2.49 Ga. Peak metamorphic conditions of similar to 700 degrees C and 5-6 kbar are interpreted to have been reached during the 2.37-2.34 Ga event. In the McCann-McArthur Lake region of the southwestern Rae craton, upper amphibolite- to granulite-facies metamorphism is dated by in situ SHRIMP monazite ages of ca. 2.53, 2.47, and 2.37-2.28 Ga. Textural relationships indicate deformation initiated by ca. 2.37 Ga and terminated by ca. 2.30 Ga. Metamorphic conditions of similar to 5 kbar and 700-735 degrees C were quenched at ca. 2.3 Ga following peak conditions of similar to 7 kbar and 800 degrees C.The evidence for regional deformation at 2.54-2.49 Ga on southern Boothia Peninsula supports an Andean-type accretionary margin setting for the Arrowsmith orogeny. A collisional event may have terminated high-grade metamorphism in the northern region by ca. 2.34 Ga while metamorphism associated with continental arc magmatism continued in the south until at least ca. 2.28 Ga. These combined data demonstrate the continuity and broad extent of the Arrowsmith orogen along the western flank of the Rae craton, extending similar to 1500 km from northern Saskatchewan to northern Baffin Island. The broad extent of this globally rare orogenic event provides an important piercing point for supercontinent reconstructions which are discussed in a companion paper. The inferred convergent tectonic activity between ca. 2.54 and 2.28 Ga is interpreted to have occurred on the flank of a growing supercontinent, a setting that could account for an apparent slowdown, but not shutdown in global tectonics. (C) 2012 Elsevier B.V. All rights reserved.

The Pelican Thrust Zone is a 3-7 km-wide recrystallized mylonite zone, along which Paleoproterozoic arc volcano-plutonic and derived sedimentary rocks of the Flin Flon - Glennie Complex were thrust over an Archean package (Jan Lake Complex) consisting of ca. 3.1 Ga calc-alkaline orthogneisses, pelitic migmatites, and a ca. 2.45 Ga tholeiitic charnockite-norite intrusive suite. A regional northeast-plunging stretching lineation and a variety of kinematic indicators imply southwesterly transport, matching that of other coeval shallower crustal-level structures observed throughout the northern Flin Flon Domain and southern flank of the Kisseynew Domain (e.g., Sturgeon-Weir and Annabel Lake shear zones). Subsequent east-side-up displacement on the Tabbernor Fault, together with domal fold interference, has exposed the Pelican Window and mantling mylonite zone, where it has been seismically profiled along Lithoprobe transects. Tectonic windows also expose Archean rocks in the Glennie Domain to the west, where similar southwest-verging, recrystallized mylonite zones have been documented. Together, these zones record collision and underplating of the Flin Flon - Glennie Complex by the Archean Sask Craton during prolonged protocontinent-continent collision over a minimum 1826-1805 Ma interval.

The middle Paleoproterozoic Thluicho Lake Group comprises coarse-grained continental clastic rocks deposited in fault-controlled alluvial basin(s) in the southwestern Rae Province of the Canadian Shield. The group nonconformably overlies crystalline basement that records late-Taltson high-grade metamorphism, ca. 1.93 Ga, and is folded and metamorphosed to greenschist facies, providing an important window of insight into tectonic activity in this region. This paper reports ∼100 detrital zircon ages for two samples from the lower and upper parts of the Thuicho Lake Group. Four analyses of one of the youngest detrital zircons from the stratigraphically higher member define a weighted mean 207Pb/206Pb age of 1922 ± 6 Ma, establishing a maximum depositional age for the group. This result accords with regional geological relationships indicating that the group is intermediate in age between development of two major tectonic fronts; an older, ca. 1.93 Ga east-southeast-trending front that formed at the height of Thelon-Taltson orogeny, and a younger, ca. 1.91–1.90 Ga northeast-striking front expressed by the Black Bay Fault and related northeast-striking structures affiliated with the Snowbird tectonic zone. The younger age limit of the group may therefore be older (≥1.91–1.90 Ga) than the previously reported minimum age, constrained by cross-cutting dykes dated at ca. 1.82 Ga. In terms of isotopic provenance, the bulk of analyses of the combined dataset lie within two principal age-ranges: 2750–2500 Ma and 2475–2250 Ma. The older of these is dominated by ca. 2600 Ma zircons, whereas the younger contains two statistically distinct subgroups of 2410 and 2310 Ma. This signature is consistent with derivation almost exclusively from immediately surrounding basement rocks of the Nolan, Taltson, Zemlak, Ena and Beaverlodge domains. Abundant 2475–2250 Ma zircons provide indirect evidence for the 2.45–2.3 Ga Arrowsmith orogeny. Despite proximity to the Taltson magmatic zone, 1990–1960 Ma zircons are nearly completely absent, suggesting that Thluicho Lake basins formed in the hinterland of the orogen, possibly separated from the foreland (Taltson arc) by a continental divide. Alternatively, Taltson arc plutons may not have been unroofed at the time of deposition of Thluicho Lake strata. The data presented herein support the previously proposed broad correlation between the Thuicho Lake and Nonacho groups; however, there are apparent differences in detail between respective basin settings and controls, suggesting that this correlation requires further investigation.

The Thluicho Lake Group is a middle-Paleoproterozoic succession of greenschist-facies continental clastic rocks that was deposited on variably mylonitized crystalline basement rocks in the southwestern Rae Province of the Canadian Shield, near the end of 2.02-1.92-Ga Thelon-Taltson orogenesis. Two informal formations are proposed for this fining-upward succession. The Powder Lake formation comprises predominantly coarse-grained rocks including conglomerate (Gulo Lake member), pebbly sandstone (Camel Lake member), and sandstone (Wellington Lake member), whereas the overlying Camsell Portage formation consists of sandstone to siltstone (Falls member), rhythmic sandstone and argillite (Waterloo Lake member), and argillite (Slate Island member). The two informal formations represent two principal facies associations: a lower conglomerate-sandstone facies association representing an alluvial fan to distal braided plain that underwent episodic flash flooding events and an upper sandstone siltstone-mudstone facies association representing a lacustrine environment. The Thluicho Lake basins are interpreted to have been symmetrical and elongate, and are broadly parallel to older, west-to northwest-trending basement structures. Transverse alluvial fans and braided rivers and/or fan deltas developed on elevated basin margins and drained into a large perennial lake. Similarities in lithology, age, and provenance suggest that the Thluicho Lake Group may correlate with the more extensive Nonacho Group to the north. Both groups represent remnants of a strike-slip and intermontane basin system that formed in the hinterland of the Taltson orogen at ca. 1.92 Ga.

The southern Rae Province of the western Canadian Shield underwent extensive reworking during Paleoproterozoic time. Widespread granitic plutonism and poorly defined metamorphism resulting from the ca. 2.5 to 23 Ga Arrowsmith Orogen was followed by more intense thermotectonic overprints attributed to the 1.99-1.92 Ga Taltson Orogen in the west and ca. 1.91-1.90 Ga tectonic activity associated with the Snowbird Tectonic Zone in the east. The Thluicho Lake Group is a fining-upwards, conglomerate-arkose-argillite succession deposited in an intermontane setting towards the end of the Taltson Orogen. Following deposition, the Thluicho Lake Group underwent two phases of regional folding and greenschist-facies metamorphism marking the latest Taltson and Snowbird overprints, respectively, prior to the emplacement of extensive 1.82 Ga mafic dykes. These depositional constraints support correlation of the Thluicho Lake Group with the lithologically similar Nonacho Group in the Northwest Territories, whereas petrological similarities and coeval emplacement ages indicate that the mafic dykes represent a southeastward extension of the Sparrow dykes.Mafic volcanic rocks geochemically linked to the dykes are intercalated within the Martin Group, a continental redbed succession deposited in trans-tensional basin settings, indicating that deposition was ongoing at 1.82 Ga. Similarities in age, lithological association and depositional setting suggest that the Martin Group is broadly correlative with the Baker Lake Group of the lower Dubawnt Supergroup in Nunavut. Widespread lamprophyre dykes of the type that fed minette volcanic rocks of the Christopher Island Formation in the Baker Lake Group are also spatially associated with the Martin Group. The broadly coeval Hudson granites, which extend over much of the same ground as the lamprophyres in Nunavut, also appear to have analogs in the southern Rae Province.The formation of widespread trans-tensional basins, together with extensive dyke emplacement, implies a period of intense brittle to brittle-ductile deformation throughout the western Churchill Province at about 1.83-1.82 Ga. This deformation is attributed to a broadly east-west stress regime imposed by accretion of the Nahanni-Fort Simpson Terrane to the west, combined with terminal collision in the Trans-Hudson Orogen to the east. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

A new 2941 Ma U-Pb zircon crystallization age for gneissic granite from the southwestern Beaverlodge Domain increases the extent of the known ca. 3.0 Ga suite into more highly metamorphosed gneisses. A 2606 Ma crystallization age from magnetic granitic orthogneiss demonstrates the complexity of the southeastern Zemlak Domain. Detrital zircon study of a pelitic gneiss from the Murmac Bay Group, which has a maximum depositional age of 2.33 Ga, revealed a diverse 3.14 to 2.17 Ga range of ages, most of which are represented in the regionally exposed basement rocks. The largest population, however, is the youngest at about 2.17 Ga, implying that deposition of at least part of the Murmac Bay Group took place after this time. The closest known potential source for detrital zircons of this age is in the Taltson Domain and buried terranes beneath northeastern Alberta and the Northwest Territories to the west. The earliest of two metamorphic overprints recorded in the granitic orthogneiss has an age of 2366 Ma, and is attributed to the Arrowsmith Orogeny. This age demonstrates that emplacement of an extensive 2.33 to 2.29 Ga granitoid suite in the Uranium City area and deposition of the Murmac Bay Group took place in a post-orogenic environment. A younger 1931 Ma metamorphic overprint is consistent with development during the Taltson Orogen.

The Paleoproterozoic Martin Group, located in the Rae Craton of northwestern Saskatchewan, is a sequence of intercalated siliciclastic deposits and mafic igneous rocks that were deposited in a fault-controlled intracratonic basin. Based on field relationships, mafic volcanic rocks and sills of the Martin Group have historically been viewed as genetically related to a suite of regionally extensive mafic dikes. In this study, the geochemical characteristics of the three mafic suites (volcanic rocks, sills, and dikes) were used to interpret their respective magmatic histories, to assess the possibility of a genetic relationship between the suites, and to deduce the nature of the magma source. Geochemically, these rocks range from subalkaline (tholeiitic) basalts to alkali basalts or trachyandesites and contain trace element compositions consistent with emplacement in an intracontinental setting. All three suites are highly enriched in light rare earth elements but have anomalously low concentrations of high field strength elements (e.g. Nb, Ta, Hf, Zr) relative to other trace elements. The trace element compositions suggest derivation of all three suites from a common subcontinental lithospheric mantle source that had experienced a complex enrichment history, including modification of depleted mantle by ancient subduction-related components and by small degree asthenospheric melts. A common, enriched source for these magmas is confirmed by their identical initial Nd isotopic compositions (ɛNd at the time of emplacement of −3.7 to −5.3), likely indicative of input of isotopically evolved crust to the source region during the subduction-related enrichment. The overall similarity of chemical compositions for the three suites indicates that regional emplacement of the mafic dikes and (localized?) magmatism within the Martin Group was essentially part of the same mafic magmatic event in the area, though slight intersuite compositional variations might reflect differences in magma evolution histories. A U–Pb baddeleyite date from one dike broadly dates this magmatic event at ca. 1818Ma, though it must have occurred as a series of magmatic pulses that alternated with periods of sedimentary deposition within the Martin basin. The dike magmas infiltrated pre-existing fractures, whereas the intrabasinal suites might have utilized major faults associated with basin genesis (e.g. the Black Bay fault) as magma conduits.

The western margin of the Churchill craton records a complex history of Paleoproterozoic tectonism. The most prominent of these tectonic events is recorded within the 2.0 - 1.9- Ga Taltson-Thelon magmatic zone. The widespread magmatism and high-grade metamorphism of this zone, especially in Alberta and Saskatchewan, obscures an older tectonic belt, the ca. 2.4 - 2.3-Ga Arrowsmith Orogeny. In the Uranium City region of northwestern Saskatchewan, a suite of Paleoproterozoic granites represent a magmatic product of this orogen. U-Pb zircon crystallization ages were identified for the Macintosh Bay monzogranite (Ma), the Gunnar monzogranite ( Ma), the 2330 +/- 5 2321 +/- 3 Geebee Lake tonalite ( Ma), the Yahyah Lake granite ( Ma), and the Hayter Bay monzogranite 2320 +/- 44 2287 +/- 14 ( Ma). The petrological and geochemical characteristics, emplacement ages, and Nd isotopic geochemistry 2297 +/- 10 of these plutons are most consistent with a syn- to postcollisional orogenic setting, possibly coeval with a period of orogenic extension and exhumation.

Results of a U-Pb detrital zircon geochronological study of the middle Paleoproterozoic Thluicho Lake Group are reported. The Thluicho Lake Group is a succession of coarse clastic rocks that was deposited in continental alluvial basins in the central Zemlak domain of the southwest Rae Province. Over 100 analyses were performed on detrital zircons from two stratigraphically well controlled samples from the Waterloo-Wellington lakes area, 10 km west of Uranium City – the ‘Camel Lake Member’ pebbly arkose of the ‘Powder Lake Formation’ and the ‘Falls Member’ arkose-argillite of the ‘Camsell Portage Formation’. Four analyses of one of the youngest zircons recovered from the stratigraphically higher Falls Member yielded a weighted mean 207 Pb/ 206 Pb age of 1922 ±6 Ma, establishing a new maximum depositional age for the group. This result, together with regional geological relationships, suggests that the group is intermediate in age between development of two major tectonic fronts in this part of the Rae Province; an older, ca. 1.93 Ga east-southeast–trending front that formed at the tail end of Thelon-Taltson orogeny, and a younger, ca. 1.91 to 1.90 Ga northeast-striking front expressed by the Black Bay Fault and associated northeast-striking structures affiliated with the Snowbird Tectonic Zone. The younger age limit for the group may therefore be significantly older than the previously reported minimum age of ca. 1.82 Ga. The distribution of detrital zircon ages defined by the two samples is remarkably similar, with the majority falling within two age ranges: 2750 to 2500 Ma and 2450 to 2250 Ma. The older age range is dominated by ca. 2600 Ma zircons whereas the younger contains two distinct subgroups of ca. 2420 and ca. 2320 Ma. The principal sources of the Thluicho Lake Group were therefore local basement rocks of the Nolan, Taltson, Zemlak (Ena), Beaverlodge, and possibly Train Lake domains. Abundant 2450 to 2250 Ma zircons indicate that the ca. 2.4 to 2.3 Ga Arrowsmith Orogen of the western Rae Province was also a major source of detritus. A few older (>3100 Ma) and younger (<2250 to 1920 Ma) zircons were likely sourced, locally or regionally, within the Rae Province. All told, the bulk of the Thluicho Lake Group detritus came from rocks that can be inferred to have formed the exhumed hinterland of the Taltson mountain belt. A notable feature of the Thluicho Lake dataset is the near-complete absence of 1990 to 1960 Ma zircons, an age range typical of subduction-related plutons of the Taltson Magmatic Zone. The Taltson arc did not supply detritus to the Thluicho depositional basins, supporting the inference that such basins were located in the hinterland of the orogen, which was possibly separated from the foreland by a continental divide. The data reported herein support correlation of the Thluicho Lake and Nonacho groups.

New Sm–Nd and U–Pb data indicate that a block of ancient Mesoarchean and Paleoarchean crust (3.0–3.9Ga) is present along the southwestern margin of the Rae Province, Canada. Consequently, the Rae Province can be divided into an ancient (>3.0Ga) southwestern component and a more juvenile (<3.0Ga) northeastern component. Evidence for episodic reworking of the evolved southwestern component is recorded in the Sm–Nd and U–Pb signatures of younger Archean and Paleoproterozoic intrusive rocks and sediments. Nd model ages range from 2.7 to 3.3Ga, with the oldest signatures occurring along the western end of the Beaverlodge Belt, Saskatchewan. Xenocrystic zircons with ages of ca. 2.3, 3.0, 3.2–3.3 and >3.6Ga were discovered in two Paleoproterozoic granites.

A correlation chart showing the evolution of the Manitoba–Saskatchewan segment of the Paleoproterozoic Trans-Hudson Orogen (THO) has been constructed based on available geochronological and isotopic data. Geological, petrological, geochemical, and structural data have also been incorporated into the correlation chart to provide finer detail and to allow comparison of specific tectonic events. The chart also emphasizes that the bounding Archean cratons (Superior, Hearne, Sask) have been significantly affected by Paleoproterozoic events, and it is hoped that this chart will also facilitate comparison with other Paleoproterozoic orogens in North America and beyond.

A three-dimensional model of the regional crustal architecture of the western Trans-Hudson Orogen, based on the interpretation of 590 km of deep-sounding seismic reflection data and a comparable length of existing seismic reflection information, is presented. The seismic images identify the regional geometry of the basal detachment zone (Pelican thrust) that separates juvenile allochthonous terranes from the underlying Archean microcontinent (Sask craton). The Sask Craton is inferred to have a minimum spatial extent of over 100 000 km2 with an associated crustal root that extends for 200 km along strike. During terminal collision, complete convergence of the Rae–Hearne and Superior continental blocks was precluded by the presence of the Sask Craton, resulting in the preservation of anomalous amounts of oceanic and associated sedimentary juvenile material. Along regional tectonic strike, consistency of crustal structure across the Rae–Hearne margin – Reindeer zone boundary is established. Several phases of tectonic development, including multistage subduction and continent–continent collision, are inferred for the western margin of the orogen. A bright, shallow (2–3.5 s two-way traveltime) band of reflectivity (Wollaston Lake reflector) imaged over ~150 000 km2 area is inferred to be a large post-orogenic mafic intrusion. A highly reflective, well-defined and structurally disturbed Moho discontinuity is mapped throughout the western Trans-Hudson Orogen. The present-day crustal architecture of the western Trans-Hudson Orogen is described in terms of the tectonic evolution within the region.