The Ribeira Belt

Abstract

The generation of the NW-verging Ribeira belt that fringes the São Francisco craton to the south resulted from collisional episodes dated at 620-605, 605-565, and 535-510 Ma.

Evolução Da Rede De Drenagem E Evidências De Antigas Conexões Entre as Bacias Dos Rios Grande E São Francisco No Sudeste Brasileiro

“…A alta/média bacia do Rio Grande e as áreas adjacentes da alta bacia do Rio São Francisco estão localizadas no contato entre a borda sul do Cráton do São Francisco e a zona de interferência entre os orógenos Brasília (NNW-SSE) e Ribeira (NE-SW), ambos desenvolvidos durante a Orogenia Brasiliana, ocorrida no Neoproterozoico (TROUW et al, 2013;HEILBRON et al, 2017a). A região inclui rochas cristalinas do embasamento paleoproterozoico-arqueano, metassedimentos proterozoicos dos grupos São João del Rei, Carandaí, Andrelândia, Araxá e Canastra, além das unidades granulítica, diatexítica e migmatítica da Nappe Socorro-Guaxupé, também neoproterozoicas (CAMPOS NETO et al, 2004;HEILBRON et al, 2017a).…”

“…A região inclui rochas cristalinas do embasamento paleoproterozoico-arqueano, metassedimentos proterozoicos dos grupos São João del Rei, Carandaí, Andrelândia, Araxá e Canastra, além das unidades granulítica, diatexítica e migmatítica da Nappe Socorro-Guaxupé, também neoproterozoicas (CAMPOS NETO et al, 2004;HEILBRON et al, 2017a). Ao norte ocorre cobertura neoproterozoica composta pela alternância entre rochas sedimentares siliciclásticas e carbonáticas pertencentes ao Grupo Bambuí (ALKMIM & MARTINS-NETO, 2012).…”

Comment on “Tectono Metamorphic Evolution of the Central Ribeira Belt, Brazil: A Case of Late Neoproterozoic Intracontinental Orogeny and Flow of Partially Molten Deep Crust During the Assembly of West by Meira et al.

“…Another critical point that was not assessed by the authors is the record of three metamorphic episodes in the Ribeira belt (Heilbron et al, 2017 and references therein): 620-595 Ma-accretion of the inner continental magmatic arc; 595-565 Ma-accretion of intraoceanic magmatic arcs; and 535-510 Ma-collision of the Cabo Frio Terrane (continuation of Angola craton), completing the amalgamation of West Gondwana (Machado et al, 1996;Bento dos Santos et al, 2015;Degler et al, 2017;Duffles et al, 2016;Heilbron & Machado, 2003;Lobato et al, 2015;Machado et al, 1996;Schmitt et al, 2004;Vinagre et al, 2014). As summarized by Heilbron et al (2017, and references therein), the ages of these three metamorphic episodes are constrained by: lower intercepts of zircon U-Pb discordia of Paleoproterozoic basement rocks; U-Pb ages of metamorphic rims of zircons from basement and precollisional rocks; U-Pb and U-Pb-Th Electron Microprobe analysis of monazite, titanite, and rutile in orthogneisses and paragneisses; and U-Pb zircon ages of sin-collisional sensu stricto granites (Alves et al, 2013;Heilbron et al, 2017;Heilbron & Machado, 2003;Janasi et al, 2016;Lobato et al, 2015;Valladares et al, 2017, and references therein).…”

“…In the Socorro and Embu-Paraíba do Sul terranes of southern Ribeira belt, the study area of the commented article, many plutonic rock bodies display expanded calcalkaline signatures with U-Pb zircon ages of ca. 780 Ma and 660 to 620 Ma, with mixed Mesoproterozoic T DM Nd model ages and slightly negative ε Nd and Hf values typical for continental arc signatures (Alves et al, 2013(Alves et al, , 2016Campanha et al, 2019;Cordani et al, 1973;Ebert et al, 1996;Figueiredo & Campos Neto, 1993;Hackspacher et al, 2003;Heilbron et al, 2017;Vinagre et al, 2014). In Central Ribeira belt (Rio de Janeiro and adjacent Minas Gerais states), available data point to a more complex pre-collisional scenario, where two magmatic arcs have been described: an inner continental arc system (Serra da Bolívia, Marceleza, Muriaé, Valentim batholiths) developed between ca.…”

“…The article contributes with new metamorphic petrology and U-Pb geochronology data concerning the sin-collisional stage of two terranes (Embu and Costeiro) belonging to the southern Ribeira orogen (not Central Ribeira belt, as the title suggests), in order to propose an intracontinental evolution for the whole Neoproterozoic Ribeira-Araçuaí orogenic system. Several issues regarding their review of the literature and interpretation of data should be carefully considered in face of the proposition for an intracontinental evolution of such an orogenic system that has long been considered by numerous authors as having developed through a Wilsonian sequence of events, involving continental rifting and opening of oceanic domain, subduction of oceanic lithosphere and magmatic arc development, terrane accretion, and final continental collision in the context of the amalgamation of Gondwana supercontinent (Alkmim et al, 2006(Alkmim et al, , 2017Basei et al, 2009;Campos Neto, 2000;Heilbron et al, 2008Heilbron et al, , 2017Pedrosa-Soares et al, 1998. In order to contribute to a comprehensive discussion of the tectonic evolution of the Ribeira-Araçuaí orogenic system, we bring forward the following points that have not been properly acknowledged by the authors in their proposed tectonic scheme.…”