Images of a lower-crustal oceanic slab: Direct evidence for tectonic accretion in the Archean western Superior province

Abstract

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...

Formation and Evolution of the Continental Crust

“…Once again there are two schools of thought. One of these holds that the style of deformation in Archean granite-greenstone belts was not significantly different from those of the younger orogenic belts (Bickle et al, 1980;de Wit, 1982;Myers and Watkins, 1985;White et al, 2003;van der Velden et al, 2006). In this interpretation, the domes and basins are interpreted as a fold-interference pattern.…”

The nature of the Moho in Australia from reflection profiling: A review

“…A possible example has been seen in the western Gawler craton on an east-west reflection profile completed in early 2014. In the western Superior province, White et al [31] have interpreted such a band of basal crustal reflections in terms of accreted oceanic crust with seismic P wavespeeds in the range 7.0-7.4 km/s -rather fast for the crust.…”

Thermal and mechanical controls on the evolution of archean crustal deformation: Examples from Western Australia

“…Felsic magmatism was relatively shortlived (<100 My), and mostly predated large-scale dome-andkeel amplification. The resulting map patterns resemble (at least superficially) those of post-Archean orogenic belts, and examples include the Eastern Goldfields Province (Figure 1c) of the Yilgarn Craton, Western Australia [e.g., Griffin, 1990;Swager et al, 1997;Krapez et al, 2000;Blewett et al, 2004a;Goleby et al, 2004], and the western Superior Province of Canada [e.g., Card, 1990;Henry et al, 2000;Thurston, 2002;Tomlinson et al, 2003;White et al, 2003;Percival et al, 2004].…”