Rhyacian Paleoproterozoic Mountain Building Before the Columbia Supercontinent

The Paleoproterozoic Campinorte Arc: tectonic evolution of a central Brazil pre-Columbia orogeny

Authors:

de Oliveira Cordeiro et al

Abstract:

The Campinorte Arc is a poorly exposed 2.19 to 2.07 Ga Paleoproterozoic terrane in contact with the Neoproterozoic Goiás Magmatic Arc by the Rio dos Bois Fault in the northern Brasília Belt, Central Brazil. The Campinorte Arc is divided into Pau de Mel Suite metatonalites to metamonzogranites and the Campinorte volcano-sedimentary Sequence. Pau de Mel Suite whole rock geochemistry indicates at least three separate coeval parental magmas compatible with arc signatures. U-Pb geochronology data of paragranulite and mafic granulite exposed in the region as part of the Campinorte Arc provide additional information on this Paleoproterozoic orogenic cycle. The formation and preservation of these granulites was due to tectonic switching of the back arc basin and consequent lithospheric thinning from 2.14 to 2.09 Ga with metamorphic peak from 2.11 to 2.08 Ga. A Pau de Mel Suite granodiorite sample dated at c.a. 2.08 Ga indicates post-peak magmatism. The arc was thereafter rapidly contracted preserving Paleoproterozoic high metamorphic grade mineral assemblages. Additionally, the Campinorte Arc and the neighbouring Crixás/Guarinos/Faina greenstone belts may have shared the same source of sediments as attested by geographic proximity, coeval maximum sedimentation, felsic volcanism and the occurrence of similar rock types. Gravimetric and seismic data also support a common basin hypothesis. The formation of the Campinorte Arc is contemporaneous to other northern Brasília Belt basement terranes and, along with similar arcs within and at the São Francisco Craton edges, indicate a continental crust formation event that eventually led to the assemblage of Columbia.