Stratigraphy, tectonics and detrital zircon U-Pb (LA-ICP-MS) geochronology of the Rio Preto Belt and northern Paramirim corridor, NE, Brazil

Davi Da Costa Bezerra Gobira De Alcântara Alcântara,Alexandre Uhlein,Fabrício De Andrade Caxito,Ivo Dussin,Antônio Carlos Pedrosa-Soares

doi:10.1590/2317-4889201720160102

Davi Da Costa Bezerra Gobira De Alcântara Alcântara, Alexandre Uhlein + Show 3 more

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https://doi.org/10.1590/2317-4889201720160102

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Abstract

ABSTRACT: Two important Proterozoic metasedimentary sequences, the Rio Preto and Santo Onofre Groups, crop out along the northwestern margin of the São Francisco craton and in northern Paramirim corridor, respectively. The Rio Preto Group, involved in the eponymous fold-thrust belt along the northwestern cratonic boundary, comprises the Formosa (garnet schist, quartz-mica schist, quartzite, chlorite-sericite schist and ferriferous quartz schist) and Canabravinha (quartzite, micaceous quartzite, metarhytmite, phylite, schist and metaturbidite) formations. The Santo Onofre Group occurs exclusively in the Paramirim corridor, and is composed of quartzite and minor carbonaceous or Mn-rich phylite. These units record sedimentation in shallow to deep-water marine settings related to rift basins, and were deformed and metamorphosed under greenschist facies conditions during the Brasiliano orogeny. Here we present 427 new detrital zircon U-Pb ages, which constrain the maximum depositional ages of ca. 971 Ma for the Santo Onofre Group, ca. 912 Ma for the Canabravinha Formation, and ca. 965 Ma for the Formosa Formation of the Rio Preto Group. Our data suggests that the Santo Onofre and the Rio Preto Groups accumulated in two distinct basin settings. The latter, composed mostly of sandy rocks, would represent a relatively stable, shallow-marine shelf environment. The Rio Preto Group, with metadiamictite, quartzite, pelitic and rhythmitic rocks, represents a shallow to deep marine environment influenced by gravity flows. Both groups were probably deposited in the Late Tonian, and are potential correlatives of the lower (pre-glacial) units of the Macaúbas Group of the Araçuaí belt.

Highlights

GEOLOGICAL CONTEXTThe late Precambrian geotectonic panorama of the South American platform was established during the diachronic Brasiliano orogenies, when cratonic blocks were amalgam‐ ated along Neoproterozoic orogenic belts
We focus on São Francisco Craton and its northwestern margin, occupied by the marginal Rio Preto Belt (Almeida et al 2000)
This paper presents new geologic, statigraphic and struc‐ tural data, as well as U‐Pb ages obtained on detrital zircon grains from Santo Onofre and Rio Preto Groups

Summary

Introduction

The late Precambrian geotectonic panorama of the South American platform was established during the diachronic Brasiliano orogenies, when cratonic blocks were amalgam‐ ated along Neoproterozoic orogenic belts In this scenario, we focus on São Francisco Craton and its northwestern margin, occupied by the marginal Rio Preto Belt (Almeida et al 2000). 870 Ma, as indicated by U‐Pb zircon ages of anorogenic igneous rocks (Pedrosa Soares & Alkmim 2011) This event led to the development of an extensive rift system exposed in Rio Preto Belt (Caxito et al 2014a), Paramirim corridor of São Francisco Craton (Schobbenhaus 1996, Danderfer & Dardenne 2002), Araçuaí Belt (Pedrosa‐Soares et al 2008, Kuchenbecker et al 2015), and Riacho do Pontal Belt (Caxito et al 2016, 2017). This event led to the development of an extensive rift system exposed in Rio Preto Belt (Caxito et al 2014a), Paramirim corridor of São Francisco Craton (Schobbenhaus 1996, Danderfer & Dardenne 2002), Araçuaí Belt (Pedrosa‐Soares et al 2008, Kuchenbecker et al 2015), and Riacho do Pontal Belt (Caxito et al 2016, 2017). Schobbenhaus (1996) suggests the name Araçuaí‐Paramirim‐Rio Preto System to correlate all these basins, which characterize a triple junction of rift arms formed during the early Neoproterozoic

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