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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.

The structure of the Archaean crust of the North America has been studied based on the synthesis of geological and geophysical data, including seismic sections along LITHOPROBE Geotransects, magnetic and gravity anomaly maps, and seismic tomography data. The authors rely on the experience gained in the Russian Program of the deep geological and geophysical studies of the East European Craton. The juvenile Neoarchaean crust, containing the fragments of reworked Meso-and Paleoarchaean rocks, forms an asymmetric round-oval-shaped domain, wherein the geophysical, structural, and metamorphic parameters display a concentric zoning pattern. The Central zone occupies the Hudson Bay basin. The Internal zone (the northeastern and northern Superior Province) is mainly composed of the granulite facies of metaplutonic, metavolcanic and metasedimentary rocks. The External zone encompasses the southern Superior Province together with Hearne and Rae Provinces. This paper presents 3D crustal models of southern Superior Province. The crust development resulted from rifting and a partial disruption of the continental crust, short-term opening of the linear oceans, successive northward subduction and accretion of the ancient continental and juvenile Neoarchaean oceanic and island-arc terranes between ~2.78 and ~2.70 Ga. Subsequent events in the epicontinental environment, including formation of the metasedimentary belts, granulite facies metamorphism and intense ore formation processes, took place within the range from ~2.71 to ~2.63 Ga. The SCLM morphology within the limits of the Archaean North American Craton can be represented as a flattened overturned cone with a vertical axis (down to a depth of ~350 km). The Hudson Bay basin is located right above the lithospheric keel. A number of the main features of the structure and evolution of the Archaean crust of the North American Craton, primarily the ovalconcentric zoning, the important role of high-temperature magmatic and metamorphic processes and mainly intracontinental magmatism and sedimentation, indicates the leading role of the mantle-plume type processes. The Neoarchaean evolution of the North American craton represents the plate-tectonic processes initiated by a superplume. The Neoarchaean North American Craton is one of a series of similar phenomena that occurred ~2.75 Ga ago in a number of continental regions. The most important features, repeated to a certain degree in tectonic units of this type, are: (1) synchronous formation between 2.79 and 2.58 Ga; (2) mainly intracontinental development; (3) the prevalence of oval-shaped synformal tectonic structures of different ranks with some form of concentric zoning; (4) high-temperature magmatism (usually with the participation of enderbite-charnockites and gabbro-anorthosites) and metamorphism of the granulite facies; (5) a frequently repeated combination of high-grade (granulite and hightemperature amphibolites facies) and low-or moderate-grade (greenschist and epidote-amphibolite facies) metamorphic rocks; (6) the lower-c...

Textural evidence, clinopyroxene fabric, and mineral assemblages of eclogite nodules from the kimberlite‐bearing breccia pipes of the east Colorado plateau are consistent with an origin by metamorphic recrystallization of predominantly basic igneous rocks. The eclogites are divided into three fabric groups exhibiting linear, planar, and random fabrics. Clinopyroxenes follow similar orientation rules as amphiboles in metamorphosed crustal tectonites. Partial recrystallization of olivine and extensive postcrystalline strain in the pyroxenes of the lherzolites and the websterites are believed to be due to a modification of the original fabric under crustal conditions. The inferred structural history of the ultramafic nodules puts various constraints on petrologic models attempting to explain their origin.

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