A paleoproterozoic intra-arc basin associated with a juvenile source in the Southern Brasilia Orogen: Application of U–Pb and Hf–Nd isotopic analyses to provenance studies of complex areas

Abstract

Early Proterozoic sedimentary basins are an important record of crust generation processes and consequently a fundamental key to unravelling Earth's evolution through geological time.Sediments within the basins are typically deformed and metamorphosed by subsequent tectonothermal events, which can obliterate their links to source terranes. Nd-whole-rock and A c c e p t e d M a n u s c r i p t 2136  17 and 2143  14 Ma, suggesting syn-sedimentary magmatism. Thus, the maximum age of deposition at around 2130 Ma represents the best estimate of the depositional age of the complex. The dominance of detrital zircons ages close to the age of deposition, along with synsedimentary magmatism, imply a convergent margin basin tectonic environment for the São Vicente Complex, with similarities to fore arc basin and trench deposits. Amphibolite and metasedimentary rocks point to important juvenile magmatism around 2.14 Ga. Juvenile Rhyacian (ca.2.1 Ga) granite-granodiorite-tonalite orthogneisses with arc-related geochemical signatures (Pouso Alegre Complex) that override the São Vicente Complex, are the probable main source of detritus within the complex. Both basin and source were part of the southern edge of the São Francisco plate during the assembly of West Gondwana, and served as sources for early Neoproterozoic passive margin related basins. The age of intrusive anorogenic A-type Taguar granite indicates that by 1.7 Ga the São Vicente Complex was in a stable tectonic environment.

Metamorphic modeling and petrochronology of metapelitic rocks from the Luminárias Nappe, southern Brasília belt (SE Brazil)

“…The circles (white and black) show the localization of the studied metapelite samples. The arrows in the legend of the biotite gneiss interlayered with schists and quartzite is due the different interpretations presented in the literature of the age of this unit, according Ribeiro et al (1995) and Paciullo et al (2000) this unit is Neoproterozoic (A1 and A2), however according Westin et al (2016) this is a Paleoproterozoic unit (São Vicente Complex). Geographical coordinates of analyzed samples are present in Table 1.…”

“…An alternative interpretation for the provenance of the basal lithofacies (A1 and A2 -biotite gneiss interlayered with schist and quartzite; Fig. 1, from Andrelândia Megasequence) is that these rocks belong to the Paleoproterozoic and have affinity with fore arc basin and trench deposits (Westin et al 2016(Westin et al , 2019. According to Westin et al (2016Westin et al ( , 2019, the A1 and A2 lithofacies are called São Vicente Complex and are not related neither to the Carrancas Group nor Andrelândia Mega-sequence.…”

“…1, from Andrelândia Megasequence) is that these rocks belong to the Paleoproterozoic and have affinity with fore arc basin and trench deposits (Westin et al 2016(Westin et al , 2019. According to Westin et al (2016Westin et al ( , 2019, the A1 and A2 lithofacies are called São Vicente Complex and are not related neither to the Carrancas Group nor Andrelândia Mega-sequence. The metasedimentary rocks from the southern Brasília belt are organized in a stack of syn-metamorphic thick-skinned nappes (Campos Neto et al 2010).…”

“…• the Socorro-Guaxupé Nappe, which represents the middle and lower crust and is interpreted as the root of an intracontinental magmatic arc; • the Andrelândia Nappe System that is composed of the Três Pontas-Varginha Nappe and associated klippen, as well as the Liberdade and Andrelândia nappes (Campos Neto et al 2010); • the Carrancas Nappe System and the Lima Duarte Nappe (Campos , Westin & Campos Neto 2013, Westin et al 2016, also known as Lower Nappe System (Fig. 1).…”

“…This passive margin was metamorphosed during the Ediacaran-Cambrian orogenesis, which led to the agglutination of West Gondwana (Dardenne 2000, Fuck et al 2017, Heilbron et al 2017. There are controversial interpretations regarding the tectonic evolution of the Luminárias Nappe, that is, either in a single tectonic episode related to the formation of the southern Brasília belt (Campos Neto 2000, Westin et al 2016 or as part of the interference zone between the southern Brasília and Central Ribeira belts (Peternel et al 2005, 2013b, Heilbron et al 2008, Coelho et al 2017.…”