Baltica, Amazonia and the SAMBA connection—1000 million years of neighbourhood during the Proterozoic?

Abstract Based on available tectonostratigraphic, geochronological, and structural data for northeastern Canada and western Greenland, we propose that the early, upper plate history of the Trans-Hudson orogen was characterized by a number of accretionary–tectonic events, which led to the nucleation and growth of a northern composite continent (the Churchill domain), prior to terminal collision with and indentation by the lower plate Superior craton. Between 1.96 and 1.91 Ga Palaeoproterozoic deformation and magmatism along the northern margin of the Rae craton is documented both in northeastern Canada (Ellesmere–Devon terrane) and in northern West Greenland (Etah Group–metaigneous complex). The southern margin of the craton was dominated by the accumulation of a thick continental margin sequence between c. 2.16 and 1.89 Ga, whose correlative components are recognized on Baffin Island (Piling and Hoare Bay groups) and in West Greenland (Karrat and Anap nunâ groups). Initiation of north–south convergence led to accretion of the Meta Incognita microcontinent to the southern margin of the Rae craton at c. 1.88–1.865 Ga on Baffin Island. Accretion of the Aasiaat domain (microcontinental fragment?) in West Greenland to the Rae craton resulted in formation of the Rinkian fold belt at c. 1.88 Ga. Subsequent accretion–collision of the North Atlantic craton with the southern margin of the composite Rae craton and Aasiaat domain is bracketed between c. 1.86 and 1.84 Ga (Nagssugtoqidian orogen), whereas collision of the North Atlantic craton with the eastern margin of Meta Incognita microcontinent in Labrador is constrained at c. 1.87–1.85 Ga (Torngat orogen). Accretion of the intra-oceanic Narsajuaq arc terrane of northern Quebec (no correlative in Greenland) to the southern margin of the composite Churchill domain at 1.845 Ga was followed by terminal collision between the lower plate Superior craton (no correlative in Greenland) and the composite, upper plate Churchill domain in northern and eastern Quebec at c. 1.82–1.795 Ga. Taken as a set, the accretionary–tectonic events documented in Canada and Greenland prior to collision of the lower plate Superior craton constrain the key processes of crustal accretion during the growth of northeastern Laurentia and specifically those in the upper plate Churchill domain of the Trans-Hudson orogen during the Palaeoproterozoic Era. This period of crustal amalgamation can be compared directly with that of the upper plate Asian continent prior to its collision with the lower plate Indian subcontinent in the early Eocene. In both cases, terminal continental collision was preceded by several important episodes of upper plate crustal accretion and collision, which may therefore be considered as a harbinger of collisional orogenesis and a signature of the formation of supercontinents, such as Nuna (Palaeoproterozoic Era) and Amasia (Cenozoic Era).

Correlation of Archaean and Palaeoproterozoic units between northeastern Canada and western Greenland: constraining the pre-collisional upper plate accretionary history of the Trans-Hudson orogen

Geochronological, geochemical and isotopic study of detrital zircon suites from late Neoproterozoic clastic strata along the NE margin of the East European Craton : implications for plate tectonic models

Rare earth element distribution and mineralization in Sweden: An application of principal component analysis to FOREGS soil geochemistry

Single-grain zircon U–Pb age constraints of the western and eastern sanukitoid zones in the Finnish part of the Karelian Province

The North Atlantic craton in southern West Greenland mainly consists of a tectonic collage of Mesoarchean continental crustal terranes, which were amalgamated at c. 2.7 Ga and are currently exposed at mid-crustal amphibolite to granulite facies levels. Tonalitic orthogneisses predominate, intercalated with slightly older tholeiitic to andesitic metavolcanic rocks and associated gabbro-anorthosite intrusive complexes. The North Atlantic craton also contains enclaves of Eoarchean, c. 3.86-3.6 Ga orthogneisses and supracrustal rocks including the Isua greenstone (or supracrustal) belt. This is the oldest known assemblage of rocks deposited at the surface of the Earth, comprising mafic pillow lavas, banded iron formations and metasedimentary schists with local disseminated graphite of possible biogenic origin. Eoarchean rocks have not been found in Kola and Karelia in Fennoscandia where most rocks are 2.9-2.7 Ga tonalitic-trondhjemitic- granodioritic orthogneisses with intercalated coeval greenstone belts and amphibolites. Mesoarchean 3.0-3.2 Ga rocks are found in the eastern and western parts of the Karelian province. Subduction-related rocks like the Iringora supra-subduction type ophiolite and basalt-andesite-dacite-rhyolite series volcanic rocks in many greenstone belts, as well as eclogites are found in the Archean of Fennoscandia. A clear distinction between Greenland and Fennoscandia is the abundance of 2.75-2.65 Ga igneous rocks in Fennoscandia which indicates that these two cratons had a separate evolution during the Neoarchean.

Alexander

Papers

Archean of Greenland and Fennoscandia