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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 intervals: cessation of arc magmatism, early deformation, synorogenic sedimentation, sanukitoid magmatism, bulk shortening, regional metamorphism, late transpression, orogenic gold localization, emplacement of crust-derived granites, and postorogenic cooling. The Northern Superior superterrane recorded 3.7-2.75 Ga events prior to 2.72 Ga collision with the 3.0 Ga North Caribou superterrane. Following 2.98 Ga rifting, the Uchi margin of the North Caribou superterrane evolved in an upper plate setting before 2.72-2.70 Ga collision of the <3.4 Ga Winnipeg River terrane, which trapped synorogenic English River turbidites in the collision zone. The Winnipeg River terrane was reworked in 2.75-2.68 Ga magmatic and tectonic events, including the central Superior orogeny (2.71-2.70 Ga) that marks accretion of the juvenile western Wabigoon terrane. In the south, the Wawa-Abitibi terrane evolved in a mainly oceanic setting until Shebandowanian collision with the composite Superior superterrane at 2.695 Ga. Synorogenic Quetico turbidites were trapped in the collision zone. The final accretionary event involved addition of the Minnesota River Valley terrane (MRVT) from the south, and deposition and metamorphism of synorogenic turbidites of the Pontiac terrane during the ∼2.68 Ga Minnesotan orogeny. Seismic reflection and refraction images indicate north-dipping structures, interpreted as a stack of discrete 10-15 km thick terranes. A slab of high-velocity material, possibly representing subcreted oceanic lithosphere, as well as Moho offsets, support a model of progressive accretion through plate-tectonic-like processes.

Time slices and schematic cross-sections that attempt to show the spatial and temporal relationship between geological entities within the Manitoba-Saskatchewan segment of the Trans-Hudson Orogen and that are consistent with the available geological, geophysical, geochemical, isotopic, and geochronological data are presented. The Trans-Hudson orogenic belt developed as a result of closure of the Manikewan Ocean, which initially opened at about 2.1 Ga by rifting of a possible Neoarchean supercontinent. The oldest oceanic arc rocks indicate that subduction was ongoing by 1.92 Ga, with the development of a complex Manikewan \"Ring of Fire\" that lasted for the next 100 Ma. Intraoceanic accretion of arc, ocean-floor, and ocean-island rocks within the Manikewan Ocean at 1.87 Ga formed the Flin Flon-Glennie complex, which then subsequently collided with the accreted terranes along the Hearne craton margin at ca. 1.85 Ga. These rocks were then deformed and metamorphosed over the next 75 Ma during collisions with the Sask craton and the Superior craton, both of which are interpreted to have been drifting generally northwards towards the Hearne craton. The generation of arc magmas in the orogen ceased at 1.83 Ga, an indication that continental collisions were well advanced at that stage. The present arrangement and erosion level of geological entities is related to structural reorganization after the peak of regional metamorphism at ca. 1.81. The schematic time slices and sections form part of ongoing efforts to better understand the geological evolution of the Paleoproterozoic of Canada.

In the Cree Lake Zone of northern Saskatchewan, reworked Archean orthogneisses are overlain by a highly deformed supracrustal sequence, the Paleoproterozoic Wollaston Group. This package of rocks was deformed and metamorphosed during the ca. 1.8 Ga continent-continent collision of the Trans-Hudson Orogen (THO), forming the Wollaston fold-thrust belt that underlies the eastern Athabasca Basin. The Hudsonian structural, metamorphic, and magmatic evolution of the Wollaston fold-thrust belt in the eastern Athabasca area involved six major stages. (1) Early collisional stage, DP1 at 1860-1835 Ma, involved burial of Wollaston Group metasediments from surface to depths equivalent to 3-5 kbar (1 kbar = 100 MPa) by thrust-pile stacking or imbrication tectonics, prograde metamorphism with garnet growth and development of early leucosomes, and emplacement of ca. 1840 Ma grey granite suite. (2) Collisional stage, DP2a at 1835-1820 Ma, involved continued deeper burial of Wollaston Group metasediments along a prograde P-T-t (pressure-temperature-time) path at depths equivalent to peak pressures of 6-9 kbar and approaching peak temperatures (750-825°C), mafic magma underplating in the lower crust, initiation of large-scale crustal melting, emplacement of 1835-1820 Ma tholeiitic to calc-alkaline intrusions, and initiation of strike-slip tectonics. (3) Oblique collisional stage, DP2b at 1820-1805 Ma, involved strong transpressional tectonics with NE-SW shearing and NW-SE shortening, partitioned high-strain ductile flow, kilometre-scale fold development, initiation of exhumation, attainment of peak temperatures (750-825°C), and essentially isothermal decompression with decompressional melting and intrusion of the main pulse of leucogranites and granitic pegmatites. (4) Late oblique collisional stage, DP3 at 1805-1775 Ma, caused development of amphibolite-facies dextral strike-slip shear zones and retrograde movement of older shear zones. It included apparent rotation of the main shortening axis and development of accommodation features due to vertical uplift (i.e., extension). (5) Post-collisional stage, DP4 at 1775-1760 Ma, involved continued localized adjustments along an essentially isobaric cooling path and produced NNE-trending, sinistral, oblique-slip reverse faults with reactivation of older shear zones. (6) Late post-collisional stage, DP5, produced north- to northwest-trending sinistral faults, including the Tabbernor fault system. Extension and tectonic extrusion during DP4 and DP5 were significant and resulted in orogenic collapse and formation of the Athabasca Basin at ca. 1750-1680 Ma.

Revised cross sections of the western Grenville Province incorporate new geologic results and reprocessed seismic reflection data. The geology is presented in terms of three tectonic elements: (1) \"pre-Grenvillian Laurentia and its margin\" with ca. 1740 and 1450 Ma continental arc plutons and associated supracrustal rocks; (2) \"Composite Arc Belt\" of allochthonous ∼1300-1250 Ma volcanic arcs and sedimentary rocks; and (3) \"Frontenac-Adirondack Belt\" characterized by supracrustal and granitoid rocks, and anorthosites, of uncertain affinity, that may represent a distinctive part of the Composite Arc Belt or an offshore (micro) continent. Rocks of the Composite Arc and Frontenac-Adirondack belts were amalgamated with each other by ca. 1160 Ma, were then thrust over Laurentia during ca. 1080-1035 Ma and ca. 1010-980 Ma phases of convergence, and were dissected and exhumed by <1040 Ma normal faults. Penetrative deformation was restricted to that part of the pre-Grenvillian Laurentian margin that lies to the southeast of the Grenville front and parts of the accreted Composite Arc and Frontenac-Adirondack belts. The Laurentian rocks in the Grenville Province are bounded to the northwest and southeast by southeast-dipping ductile thrust and (or) normal shear zones. The Composite Arc and Frontenac-Adirondack belts to the southeast are bounded by ductile and brittle-ductile thrust and (or) normal faults that separate domains with contrasting cooling histories. Despite a long pre-Grenvillian tectonic and plutonic history, the present crustal architecture and much of the seismic reflectivity were acquired during 1080-980 Ma phases of compression and extension.

Magnetotelluric studies of the Trans-Hudson orogen over the last two decades, prompted by the discovery of a significant conductivity anomaly beneath the North American Central Plains (NACP), from over 300 sites yield an extensive database for interrogation and enable three-dimensional information to be obtained about the geometry of the orogen from southern North Dakota to northern Saskatchewan. The NACP anomaly is remarkable in its continuity along strike, testimony to along-strike similarity of orogenic processes. Where bedrock is exposed, the anomaly can be associated with sulphides that were metamorphosed during subduction and compression and penetratively emplaced deep within the crust of the internides of the orogen to the boundary of the Hearne margin. A new result from this compilation is the discovery of an anomaly within the upper mantle beginning at depths of ∼80-100 km. This lithospheric mantle conductor has electrical properties similar to those for the central Slave craton mantle conductor, which lies directly beneath the major diamond-producing Lac de Gras kimberlite field. While the Saskatchewan mantle conductor does not directly underlie the Fort a la Corne kimberlite, which is associated with the Sask craton, the spatial correspondence is close.

This paper provides a comprehensive synthesis of virtually all units and events of Early and Middle Proterozoic age in the Yukon, spanning ∼1 Ga. Early and Middle Proterozoic time was dominated by a series of extensional-basin-forming events punctuated by orogenesis, magmatism, and hydrothermal activity. Basinal deposits include the Wernecke Supergroup (>1.71 Ga), Pinguicula Group (∼1.38 Ga), and Mackenzie Mountains Supergroup (1.00-0.78 Ga).Igneous rocks include the Bonnet Plume River Intrusions (1.71 Ga), Slab volcanics (≥1.6 Ga), Hart River sills and volcanics (1.38 Ga), and Bear River (Mackenzie) dykes (1.27 Ga). A voluminous hydrothermal event generated the widespread Wernecke breccias at 1.60 Ga. The Racklan orogeny deformed the Wernecke Supergroup prior to emplacement of the Wernecke Breccia. The Corn Creek orogeny deformed Mackenzie Mountains Supergroup and older rocks prior to deposition of the Windermere Supergroup (<0.78 Ga). Long intervals with scanty rock records extended for as much as 300 Ma and appear to represent periods of crustal stability and subaerial conditions. By the time of Windermere rifting (<0.78 Ga), the supracrust of northwestern Laurentia was a mature, largely denuded orogenic belt with a composite sedimentary-metamorphic-igneous character. New isotopic data include Nd depleted mantle model ages for the Wernecke Supergroup (2.28-2.69 Ga) and Wernecke Breccia (2.36-2.96 Ga), a U-Pb zircon age for a Hart River sill 1381.9+5.3-3.7 (Ma), detrital U-Pb zircon ages from the basal Pinguicula Group (1841-3078 Ma), detrital muscovite ages from the Mackenzie Mountains Supergroup (1037-2473 Ma), and muscovite 40Ar/39Ar cooling ages from the Wernecke Supergroup (788±8 and 980±4 Ma).

Analysis of the Lithoprobe Deep Probe and Southern Alberta Refraction Experiment data sets, focusing on the region between Deep Probe shots 43 and 55, has resulted in a continental-scale velocity structural model of the lithosphere of platformal western Laurentia reaching depths of ∼150 km. Three major lithospheric blocks were investigated: (i) the Hearne Province, a typical continental Archean cratonic province lying beneath the Western Canada Sedimentary Basin; (ii) the Wyoming Province, an even older block of Phanerozoic-modified Archean crust with an enigmatic lower lithosphere; and (iii) the Yavapai-Mazatzal Province, Proterozoic terranes underlying the Colorado Plateau and Southern Rocky Mountains. In this study, the northern two of these regions are investigated with a modified ray-theoretical traveltime inversion routine that respects the spherical geometry of the Earth. The resulting crustal velocity structure, combined with supporting geological and geophysical data, reveals that the Medicine Hat block (MHB), lying between the Hearne and Wyoming provinces, is a third independent Archean crustal block. The subcrustal lithosphere along the profile is homogeneous in velocity structure, but two significant northward-dipping reflectors are apparent and interpreted as relic subduction zones associated with sutures between the three Archean blocks. The Hearne crust is typical of an Archean shield or platform both in its thickness of 34-50 km and its seismic velocity structure. The crust of the Archean MHB and Wyoming Province, which ranges in thickness from 49 to 60 km, includes a 10-30 km thick high-velocity layer, interpreted to be Proterozoic in age. Such a feature is unexpected beneath Archean crustal provinces, but if the region is considered to be the remanent marginal portion of a larger Archean continent, then the interpreted Proterozoic underplating and lack of an Archean lithospheric root can be explained. The variable topography along the reflective upper and lower boundaries of this layer, especially, within the MHB, suggests considerable variability in its emplacement and subsequent tectonic history.

A continental-margin magmatic arc is inferred to have existed on the southeastern (present coordinates) margin of Laurentia from Labrador to Texas from ∼1500-1230 Ma, with part of the arc subsequently being incorporated into the 1190-990 Ma collisional Grenville Orogen. Outside the Grenville Province, where the arc is known as the Granite-Rhyolite Belt, it is undeformed, whereas within the Grenville Province it is deformed and metamorphosed. The arc comprises two igneous suites, an inboard, principally quartz monzonitic to granodioritic suite, and an outboard tonalitic to granodioritic suite. The quartz monzonite-granodiorite suite was largely derived from continental crust, whereas the tonalitic-granodiorite suite is calc-alkaline and has a juvenile isotopic signature. Available evidence from the Grenville Province suggests that the arc oscillated between extensional and compressional settings several times during the Mesoproterozoic. Back-arc deposits of several ages, that formed during relatively brief periods of extension, include (1) mafic dyke swarms subparallel to the arc; (2) continental sediments, bimodal volcanics and plateau basalts; (3) marine sediments and volcanics formed on stretched continental crust; and (4) ocean crust in a marginal basin. Closure of the back-arc basins occurred during the accretionary Pinwarian (∼1495-1445 Ma) and Elzevirian (∼1250-1190 Ma) orogenies, as well as during three pulses of crustal shortening associated with the 1190-990 Ma collisional Grenvillian Orogeny. During the Elzevirian Orogeny, closure of the Central Metasedimentary Belt marginal basin in the southeastern Grenville Province was marked by subduction-related magmatism as well as by imbrication of back-arc deposits. The presence of a continental-margin magmatic arc on southeastern Laurentia during the Mesoproterozoic implies that other coeval magmatism inboard from the arc took place in a back-arc setting. Such magmatism was wide-spread and chemically diverse and included large volume \"anorogenic\" anorthosite-mangerite-charnockite-granite (AMCG) complexes as well as small volume alkaline, quartz-saturated and -undersaturated \"within-plate\" granitoids. Recognition of the ∼300 million year duration of the Mesoproterozoic convergent margin of southeastern Laurentia suggests that there may be useful parallels with the evolution of the Andes, which has been a convergent margin since the early Paleozoic.

The Lithoprobe Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) study across northwestern North America, in combination with related crustal studies, has been synthesized into an 1800 km long cross section of the lithosphere that is constrained by high-resolution geophysical data (seismic reflection, refraction, electromagnetic, potential fields) and detailed bedrock geology. The cross section offers one of the longest \"continuous\" profiles of the continental lithosphere anywhere in the world that is constrained by combined geophysical measurements and electromagnetic properties and exposed bedrock geological relationships. The primary conclusion of the study is that, during all major orogenic episodes recorded from Archean to present in that part of Earth's lithosphere, the crust, and perhaps much of the mantle, was reorganized and redistributed rather than being differentiated from the mantle at the time of orogenesis. The observed subsurface geometries of relict subduction zones, accretion boundaries, and magmatic arcs all lead to the inference that the crust includes a dominant proportion of reworked material. A similar conclusion appears applicable for the origin of subcrustal lithosphere in the region, i.e., that much of the lithosphere, whether Archean in the Slave Province or Proterozoic in the Cordillera, is old and thus that the amount of \"new\" lithosphere added to the plate during orogenesis is surprisingly small. A corollary is that many accreted rocks at surface that record orogenic complexity are detached from their originally underlying lithosphere and were emplaced upon unrelated crust and mantle during deformation.

Vertical incidence seismic data were collected along a 300 km-long profile across the northwestern flank of the Trans-Hudson Orogen in Saskatchewan (line S2b). The present study integrates the seismic data with previously published geological maps and recent results from the La Ronge-Lynn Lake Bridge Project that provide new constraints on the lithological, structural, and tectonic framework of this collisional zone. An interpretative section, based on the seismic reflectivity and surface geological constraints, is presented. The integrated data suggest the following key elements. (1) Although an early foreland-vergent accretion history is suggested by surficial geological constraints, the predominant fabric is reflected by penetrative hinterlandward vergence. (2) A zone of more reflective lower crust with hinterland-verging fabric may represent \"fossil\" reflectors from a pre-collisional accretionary phase. (3) The Archean to Paleoproterozoic Sask Craton may extend in the lower middle crust to at least beneath Rottenstone Domain, consistent with what is observed along strike on other Lithoprobe seismic profiles. (4) The Needle Falls and Parker Lake shear zones do not appear to be associated with obvious reflectors, consistent with observations from Reindeer Lake, suggesting that they merely rework the Wathaman Batholith intrusive margin and are not fundamental sutures. (5) The La Ronge and Rottenstone domains show nearly identical seismic properties, consistent with recent mapping results in the Reindeer Lake area that suggest that they are temporally and, at least in part, lithologically related in the area covered by, and to the east of, seismic line S2b.