Accepted Manuscript Provenance and sedimentary environments of the Proterozoic São Roque Group, SEBrazil: contributions from petrography, geochemistry and Sm-Nd isotopic systematics of metasedimentary rocks R. Henrique-Pinto, V.A. Janasi, C.C.G. Tassinari, B.B. Carvalho, C.R. Cioffi, N.M. Stríkis PII:
S0895-9811(15)30032-8
DOI:
10.1016/j.jsames.2015.07.015
Reference:
SAMES 1432
To appear in:
Journal of South American Earth Sciences
Received Date: 17 January 2015 Revised Date:
21 July 2015
Accepted Date: 22 July 2015
Please cite this article as: Henrique-Pinto, R., Janasi, V.A., Tassinari, C.C.G., Carvalho, B.B., Cioffi, C.R., Stríkis, N.M., Provenance and sedimentary environments of the Proterozoic São Roque Group, SE-Brazil: contributions from petrography, geochemistry and Sm-Nd isotopic systematics of metasedimentary rocks, Journal of South American Earth Sciences (2015), doi: 10.1016/ j.jsames.2015.07.015. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Provenance and sedimentary environments of the Proterozoic São Roque Group, SE-
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Brazil: contributions from petrography, geochemistry and Sm-Nd isotopic
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systematics of metasedimentary rocks
4 Henrique-Pinto, R.a; Janasi, V.A.a; Tassinari, C.C.G.a; Carvalho, B.B.b; Cioffi, C.R.a;
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Stríkis, N.M.a a
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b
Instituto de Geociências, Universidade de São Paulo, São Paulo, Brazil.
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Département des Sciences Appliquées, Université du Québec à Chicoutimi, Québec, Canada. *Corresponding author:
[email protected]
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Abstract
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The Proterozoic metasedimentary sequences exposed in the São Roque Domain (Apiaí
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Terrane, Ribeira Belt, southeast Brazil) consist of metasandstones and meta-felspathic wackes with
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some volcanic layers of within-plate geochemical signature (Boturuna Formation), a passive
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margin turbidite sequence of metawackes and metamudstones (Piragibu Formation), and volcano-
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sedimentary sequences with MORB-like basalts (Serra do Itaberaba Group; Pirapora do Bom Jesus
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Formation). A combination of zircon provenance studies in metasandstones, whole-rock
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geochemistry and Sm-Nd isotopic systematics in metamudstones was used to understand the
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provenance and tectonic significance of these sequences, and their implications to the evolution of
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the Precambrian crust in the region.
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Whole-rock geochemistry of metamudstones, dominantly from the Piragibu Formation,
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points to largely granitic sources (as indicated for instance by LREE-rich moderately fractionated
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REE patterns and subtle negative Eu anomalies) with some mafic contribution (responding for
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higher contents of Fe2O3, MgO, V, and Cr) and were subject to moderate weathering (CIA - 51 to
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85). Sm-Nd isotope data show three main peaks of Nd TDM ages at ca. 1.9, 2.1 and 2.4 Ga; the
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younger ages define an upper limit for the deposition of the unit, and reflect greater contributions
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from sources younger than the >2.1 Ga basement.
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The coincident age peaks of Nd TDM and U-Pb detrital zircons at 2.1-2.2 Ga and 2.4-2.5
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Ga, combined with the possible presence of a small amount of zircons derived from mafic
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(gabbroid) sources with the same ages, as indicated by a parallel LA-ICPMS U-Pb dating study in
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metapsammites, are suggestive that these were major periods of crustal growth in the sources
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involving not only crust recycling but also some juvenile addition.
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A derivation from similar older Proterozoic sources deposited in a passive margin basin is
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consistent with the main sedimentary sequences in the São Roque Domain being broadly coeval
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and in part laterally continuous. The coincident age, Sm-Nd isotope signature and geographic
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proximity make the exposures of basement orthogneisses in the Apiaí Terrane candidates for
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source material to the São Roque Domain. Additional sources with younger Nd TDM could be
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juvenile 2.2 Ga basement from the southern portion of the São Francisco Craton and its marginal
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belts (e.g., Mineiro Belt and Juiz de Fora Complex).
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Key words: Ribeira Fold Belt; São Roque Group; provenance; Sm-Nd isotope signature; paleo-
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environmental reconstruction.
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1. Introduction
Provenance studies of shales and mudstones are especially appealing, since they are
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the most abundant sedimentary rocks in the geological record; however, they are
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particularly difficult to study because the very small size of their components restricts the
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use of standard petrographic tools. Thus, trace-element geochemistry, combined with
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isotope data (Sm-Nd, but also Rb-Sr, Pb-Pb and Lu-Hf), has proven as an important
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instrument to determine the relative contributions of felsic and mafic sources, as well as
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the tectonic settings and secular trends in crustal evolution of these rocks (McLennan et al.,
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1990; McLennan and Hemming, 1991; McLennan et al., 1995). Additionally, Th/Sc,
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La/Sc, La/Lu ratios are higher in felsic rocks, while elements as Cr, Ni, Sc are more
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concentrated in mafic igneous rocks (Cullers et al., 1987; Cullers and Berendsen, 1988;
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Cullers and Podkovyrov, 2002). The size of the negative Eu anomalies in the source
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appears to be preserved in fine-grained sediments, and thus can be used in studies of
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provenance; for instance, mafic igneous rocks contribute slight positive or no Eu anomalies
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(Eu/Eu*).
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Weathering of biotite, amphibole, pyroxene, olivine and opaque minerals produces
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clay minerals such as smectite-vermiculite, whereas feldspars typically weather to kaolinite
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and illite. The intensity of the weathering process can be measured by the ratio between the
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“immobile” element Al and “mobile” elements such as Ca, Na and K. The effects of
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chemical weathering can be measured by the Chemical Index of Alteration (CIA) (Nesbitt
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and Young, 1982, 1984 and 1989; Nesbitt et al., 1996; Nesbitt and Markovics, 1997).
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Taking into account these properties, many authors have attempted paleoenvironmental
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reconstruction in geological sequences with ages ranging from Precambrian to Recent
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(Nesbitt and Young, 1982; Sawyer, 1986; Harnois, 1988; McLennan et al., 1993; Fedo et
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al., 1995; Nesbitt et al., 1996; Cullers, 2000; Bauluz et al., 2000; Bahlburg and Dobrzinski,
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2009).
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This work presents the results of a provenance study of low- to medium-grade
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metasedimentary rocks exposed in the São Roque Domain (SRD) in the Proterozoic
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Ribeira Belt, SE Brazil. Our previous works (Henrique-Pinto and Janasi, 2010; Henrique-
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Pinto
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metaconglomerates and associated metarkoses from exposures of the lower stratigraphic
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unit (Boturuna Formation) in a restricted area at the NW of the city of São Paulo. Here we
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use petrography, geochemistry and Sm-Nd isotope geochemistry as main instruments to
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extend that study to a broader area that encompasses a large portion of the SRD exposures,
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including samples of meta-sandstones. Our results are integrated with those from a
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provenance study based on detrital zircon chemistry and U-Pb dating (Henrique-Pinto,
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2012; Henrique-Pinto et al., 2015).
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2. Geological Setting
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2.1. The Ribeira Belt
al.,
2012)
investigated
the
paleoenvironment
and
provenance
of
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The term “Ribeira Fold Belt” was originally defined to refer to the whole orogenic
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system running parallel to the coastline of southeast and south Brazil (Hasui et al. 1975).
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Current usage restricts the term to the central segment of this system, corresponding to a
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~N60E trending, 100-200 km wide domain that was strongly affected by Neoproterozoic
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(~800-500 Ma) deformation, metamorphism and granitic magmatism (e.g. Campanha and
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Sadowski, 1999; Campos Neto, 2000; Heilbron et al., 2004 and 2008; Trouw et al., 2013).
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Defined as such, it corresponds to a southern continuation of the Araçuaí Belt (developed
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at the eastern margin of São Francisco craton), and is located to the north of the Luis Alves
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“cratonic fragment” (Fig. 1).
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A southward change in structural trend and dominant tectonic flow (from orogen-
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transverse to orogen-normal) in the transition from the Araçuaí to the Ribeira Belt is
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related by some authors to contrasted responses of collision against a rigid lithospheric
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block (the São Francisco Craton) versus a least stiff (and thinner) lithosphere (Vauchez et
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al., 1994). Campanha and Brito Neves (2004) emphasizing the orogen-parallel tectonics
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have interpreted the Ribeira Belt as the product of oblique collisional events. Alternative
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models admit that the Ribeira orogen developed after the collage of the São Francisco
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craton with another cratonic block now hidden beneath the Phanerozoic Paraná Basin; the
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suture zone would correspond to a regional NNW-trending gravity limit (Mantovani and
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Brito Neves, 2005). In these models, components of the Ribeira Belt are interpreted as the
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reworked borders of one or the other of these cratonic blocks (e.g., Campos Neto and
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Caby, 2000; Trouw et al., 2013) A major source of uncertainty on the tectonic meaning of the Ribeira Belt within
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the framework of the whole orogenic system is therefore the lack of obvious connections
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with a stable cratonic area. This is aggravated by its involvement in a major dextral shear
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zone that sliced the belt in elongated fault-bounded blocks in such a way that much of the
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original information on vergence, lateral correlation and paleogeography of the
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metasedimentary units may have been obscured (e.g., Campanha and Sadowski, 1999;
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Campanha and Brito Neves, 2004; Heilbron et al., 2008).
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Although there is some controversy in the literature about the number of blocks and
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their limits, and even about the inclusion of some of them in the Ribeira Belt, we follow
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subdivisions by Campos Neto (2000) and Heilbron et al. (2004, 2008), who distinguish
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three major lithotectonic units in the Southern Ribeira Belt (Apiaí, Embu and Curitiba
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Terranes), and another four in the Central Ribeira Belt (Occidental, Paraíba do Sul,
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Oriental and Cabo Frio Terranes). In this conception, the northwest limit of the Southern
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Ribeira Belt is defined by the Jundiuvira Shear Zone (Fig. 2A), which separates it (where
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not covered by Phanerozoic sediments) from the Socorro-Guaxupé Nappe, a
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Neoproterozoic high-grade Terrane accreted to the southern border of the São Francisco
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Craton. Its southeast limit is defined by the Lancinha-Cubatão Shear Zone, which separates
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it from the Oriental Terrane. In its southernmost portion, the Ribeira Belt is bound to the
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south by Paleoproterozoic granulites unaffected by the Neoproterozoic thermal event and
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thus described as a “cratonic fragment” (the Luiz Alves Microplate; Basei et al., 2009).
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The Apiaí Terrane (Fig. 1), used here as geographic connotation, lies to the north
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of the Curitiba Terrane, and is divided into the north-eastern São Roque Domain and the
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south-western Açungui Domain.
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The Açungui Domain comprises different metasedimentary successions of distinct
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ages and lithological content. Some of the most expressive groups (Água Clara,
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Votuverava and Perau) have Mesoproterozoic minimum ages, as indicated by the ~1.5-1.4
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Ga U-Pb zircon ages of interlayered metabasic rocks (Basei et al., 2008; Campanha et al.,
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2010; Siga Jr et al., 2011a). The Votuverava Group is admitted by some authors as a back-
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arc sequence on the basis of the geochemical signature of the metabasic rocks (Faleiros et
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al., 2011) while others interpret it as a passive margin sequence (Siga Jr et al., 2011a; Siga
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Jr et al., 2011b). A Statherian (~1.75-1.8 Ga) rifting process is suggested by frequent 4
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intruding Paleoproterozoic orthogneisses in small basement windows of the Votuverava
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and Perau Groups (Cury et al., 2002; Siga Jr et al., 2007; Siga Jr et al., 2011b). No
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Statherian metasedimentary sequences were recognized so far; however, as 1.5-1.4 Ga are
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minimum depositional ages for both the Votuverava and Perau Groups, these successions
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could potentially be connected to that rifting episode.
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A carbonatic open-sea shelf characterized by interlayered terrigenous and clast-
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chemical sediments (Lajeado Group; Campanha and Sadowski, 1999) located to the north
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of the Votuverava Group is interpreted as a passive-margin sequence that could correspond
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to a more proximal sequence of the same basin. S-SE-directed paleocurrents (Campanha
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and Sadowski, 1999) are consistent with this interpretation. The depositional age of the
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Lajeado Group is constrained between 1.4 Ga and 0.88 Ga (Campanha et al., 2010).
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At least two volcano-sedimentary successions admitted as of Neoproterozoic age
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occur in the Açungui Domain: the Itaiacoca carbonate platform sequence (minimum age
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~1.0-0.9 Ga based on intrusive metabasic rocks) and Ediacaran volcanic-clastic sequences
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filling small basins that are broadly contemporaneous with the granitic plutonism, either
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“syn-orogenic” (Itaiacoca II sequence, ~0.65-0.63 Ga; Siga Junior et al., 2009), or “post-
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orogenic” (the ~0.58 Ga Iporanga pull-apart basin; Campanha et al., 2008).
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The Embu Terrane, located between the Caucaia/Paraíba do Sul and
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Lancinha/Cubatão Fault Systems (Fig. 1), is made up of low- to high grade
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metasedimentary sequences with a few windows of Paleoproterozoic basement, the most
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expressive of which corresponds to the Rio Capivari migmatites, dated at ~2.1 Ga and
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showing Archaean (~2.9-2.7 Ga) crust residence, as evidenced by inherited zircon crystals
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and Nd TDM model ages (Babinski et al., 2001). The metamorphic grade of the
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metasedimentary sequences increases eastward, reaching high amphibolite to granulite
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facies.
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The depositional age(s) of the Embu Terrane metavolcano-sedimentary sequence(s)
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are poorly constrained; upper and lower limits are given respectively by the age of
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metamorphism and intrusive orthogneisses at ~0.8 Ga (Vlach, 2001; Cordani et al., 2002)
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and by Nd TDM model ages of metasedimentary rocks at ~1.8 Ga (Dantas et al., 2000).. An
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constraint on the maximum depositional age was proposed by Trouw et al. (2013) from a
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zircon provenance study of two quartzite samples (eastern portion), both showing identical
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patterns with SRD (Henrique-Pinto et al., 2015), with strong peak at ca. 2.2 Ga and smaller
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peaks spreading to ages as old as 3.5 Ga; 0.8-0.6 Ga ages are associated with metamorphic
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overgrowths.
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2.2. The São Roque Domain The northernmost fault-bounded block of the Apiaí Terrane (Fig. 2A) is composed
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of medium- to low-grade metavolcano-sedimentary Proterozoic sequences intruded by
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large volumes of Ediacaran granites. The stratigraphy of the metavolcano-sedimentary
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sequences, originally grouped into a single unit (São Roque Group) is currently subject of
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some controversy (e.g. Juliani and Beljavskis, 1995; Henrique-Pinto and Janasi, 2014).
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A two-fold stratigraphic division was initially proposed by Hasui et al. (1976), who
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distinguished in the western portion of the domain: the Boturuna (sericitic phyllites with
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lens of quartzite at the bottom and carbonatic rocks at the top) and Piragibu (rhytmic
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turbidites with alternating phyllites and quartzites) formations. A low-grade metavolcano-
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sedimentary sequence locally underlies the Piragibu Formation in this region, and is
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dominated by MORB-like tholeiitic metabasalts with pillow-lava structures (Figueiredo et
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al., 1982; Tassinari et al., 2001) associated with pyroclastic rocks and meta-limestones
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showing well-preserved stromatolite structures (1700 to 850 Ma; Bergmann and Fairchild,
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1985). This sequence was named Pirapora do Bom Jesus Formation and interpreted as
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passive margin volcanic centers forming atoll-like structures by Bergmann (1988). An
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Ediacaran (628 ± 9 Ma) U-Pb monazite age from a metabasalt from the Pirapora sequence
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led some authors (e.g., Hackspacher et al., 2000; Juliani et al. 2000) to interpret it as part of
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a Neoproterozoic back-arc basin. Tassinari et al. (2001) interpreted the Pirapora sequence
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as an ophiolite slice, in view of the important volume of mafic magmatic rocks with pillow
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lavas, MORB-type chemistry and association with magnetite/chromite-talc schists. An
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Ediacaran depositional age seems unlikely for the Pirapora sequence in view of its
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stratigraphic position and dating of the other sequences as described below.
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The eastern continuation of the basal Boturuna Formation is characterized by the
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predominance of meta-feldspathic wackes interlayered with polymictic metaconglomerates
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(which have pebbles and cobbles encased in a metarkose framework and local meta-
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quartzarenites), local meta-quartzarenites (Pico do Jaraguá) and small bodies of
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metavolcanic rocks (basaltic trachyandesites and porphyritic meta-trachydacites; Carneiro,
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1983; Carneiro et al., 1984; Henrique-Pinto and Janasi, 2010). The volcanism is bimodal
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and has a within-plate geochemical signature (low mg#, high Zr, Y, Nb, and low Sr;
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Henrique-Pinto and Janasi, 2010). A ~1.75-1.80 Ga depositional age seems well
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established from U-Pb zircon dating of these meta-trachydacites (1790 ± 14 Ma; van
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Schums et al., 1986) and metabasic rocks (1750 ± 40 Ma metamicrogabbro with relics of
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clinopyroxene and preserving an intergranular texture; Oliveira et al., 2008). In the eastern portion of the São Roque Domain, Coutinho et al. (1982) recognized
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a distinctive metavolcano-sedimentary sequence (basic volcanics, sub-volcanics and tuffs
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interlayered with pelites, marls and chemical sediments) and an upper metasedimentary
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sequence (clay-silt rhytmites and carbonatic sediments). Initially correlated to the Boturuna
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Formation, the lower metavolcano-sedimentary sequence was renamed the Serra do
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Itaberaba Group by Juliani et al. (1986), on the basis of its higher metamorphic grade
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(amphibolite-facies) and the proposed existence of an erosive contact marked by the
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presence of clasts and volcanic fragments derived from it, in metaconglomerates from the
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Boturuna Formation. However, a meta-andesite unit, interpreted as a small intrusion
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related to the beginning of sedimentation in the Serra do Itaberaba Group and located
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stratigraphically above a MORB-like metamafic unit containing amphibolites and
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metatuffs, yielded a U-Pb zircon age of 1395 ± 10 Ma, which would provide the minimum
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age of deposition (Juliani et al., 2000). Considering the above constraints for the São
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Roque Group, this age suggests that the Serra do Itaberaba Group could be younger than
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the Boturuna Formation.
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The uppermost unit in the São Roque Group is the Piragibu Formation, a rhythmic
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sequence with a predominance of meta-mudstones interbedded with metawackes, which
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may correspond to turbidity current deposits in a marine environment (e.g., Juliani and
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Beljaviskis, 1995, and references therein). In summary, lithostratigraphic and
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geochronological information suggests that up to three main (metavolcano)-sedimentary
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sequences are present in the São Roque Domain: (1) a lower Statherian (~1.75 Ga) rift
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sequence (Boturuna Formation); (2) an intermediate Calymmian (~1.4 Ga?) metavolcano-
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sedimentary sequence with MORB-like magmatism and variously interpreted as back-arc
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or passive margin (the Serra do Itaberaba Group and possibly the lower-grade Pirapora do
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Bom Jesus Formation); and (3) an upper unit of platform turbidites (the Piragibu
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Formation).
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3. Sampling and analytical procedures The rock samples chosen for this study were collected to assemble a representative
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set of the São Roque metasedimentary succession in terms of grain size and mineralogical
236
and textural maturity, and targeting the best available exposures, in order to avoid, as far as
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possible, the effects of weathering, which are widespread in the region. A total of 30
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samples were selected for whole-rock geochemistry. Four of these samples were collected
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from units very similar to Piragibu and Boturuna Formations, but outcropping just north of
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the Jundiuvira Shear Zone and therefore outside the São Roque Domain. The chemical
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analyses were preceded by petrographic studies and modal counting, for which 500 points
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were counted per thin section (Table 1).
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3.1. Whole-rock chemistry
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Chemical analyses were carried out at the Geoanalitica Core Research Center,
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Instituto de Geociências, Universidade de São Paulo, Brazil. Samples were crushed in a
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steel jaw-crusher and subsequently in an agate disk mill. Whole-rock major and trace
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element compositions were obtained by XRF spectrometry, respectively from pressed
249
pellets and fused discs, following the analytical protocol described in Mori et al. (1999). Rare earth elements (REE) and other trace-elements present in low contents
251
(typically < 100 ppm) were measured by inductively coupled plasma mass spectroscopy
252
(ICP-MS) in a Perkin Elmer Plasma Quadrupole MS ELAN 6100DRC, following the
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analytical protocols described in Navarro et al. (2002). Aliquots of 100 mg powder were
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mixed with 5 ml HNO3 and 15 ml HF in Parr type bombs and then heated at ~200° C for
255
five days, to ensure complete dissolution of ultra-stable minerals such as zircon.
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3.2. Sm-Nd analyses
Whole-rock Sm-Nd isotope analyses (n=20) were performed on the same powders
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used for elemental geochemistry at the Centro de Pesquisas Geocronológicas (CPGeo),
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Instituto de Geociências, Universidade de São Paulo, Brazil. Samples were dissolved by
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acid attack (5 ml HNO3 and 15 ml HF) in Parr-type bombs at T~160° C for ten days. For
262
isotope separation, conventional cation exchange columns filled with resin AG 50 (200-
263
400 mesh) using HCl and water in varying concentration were employed.
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The Nd isotopic ratios were obtained using a Finnigan MAT-262 multi-collector
265
mass spectrometer, whereas the Sm isotopic ratios were obtained in a VG-354 single
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collector mass spectrometer. The average 143Nd/144Nd values measured for the La Jolla and
267
BCR-1 Nd standards during the period of this study were 0.511849 ± 0.000025 and
268
0.512662 ± 0.000027, respectively. The maximum measured errors were 0.09% for the
269
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270
assume present CHUR ratios of
271
decay constant used was 6.54 x 10-12 years-1. Nd TDM ages were calculated according to
272
DePaolo (1988). Details of the analytical protocol are given in Sato et al. (1995).
Sm/144Nd ratio and ± 0.00002 for
Nd/144Nd (2σ precision level). εNd calculations
Nd/144Nd= 0.512638 and
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Sm/144Nd= 0.1967. The
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4. Petrography
Using the compositional maturity, based on the proportion of quartz, feldspar
276
and lithic fragments, and the textural maturity, based on the proportion between framework
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and matrix (McBride, 1963; Dott, 1964), modal counting for some the studied samples
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allowed the classification of the metasedimentary rocks into six subtypes (Fig. 3).
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The samples with greater sedimentary maturity (< 10% matrix and > 75% quartz)
280
are classified as meta-quartzarenites and meta-subarkoses (inset X in Fig. 3). In some cases
281
these rocks lost the original sedimentary petrofabrics due to metamorphic overprint,
282
reflecting the low competence of quartz during deformation and increase of temperature
283
(Figs. 4A and B).
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The lowest compositional maturity (>25% feldspar content) and sedimentary
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petrofabrics (angular feldspar crystals) of metarkoses (Fig. 4C) and meta-feldspathic
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wackes (Fig. 4D) suggest short transport distances. The similar proportions of plagioclase
287
and alkali-feldspar indicate that their main sources were of granitic composition.
288
Additional sources are preserved as lithic fragments of metabasic rocks and quartzarenites,
289
both always present in small modal proportions (less than 1%).
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The metamudstones and meta-quartz wackes (Figs. 4E an F) are characterized by
291
low textural and high compositional maturities (respectively more than 40% matrix and
292
over 70% quartz, inset Y in Fig. 3). These rocks are mostly composed of very fine to fine-
293
grained particles, with sub-angular to rounded grains, and their original sedimentary
294
structures are often preserved, e.g., as plane-parallel layering with clay-rich and quartz-rich
295
bands in metamudstones (Fig. 4F).
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5. Geochemistry Chemical classification based on major elements shows a good correlation with the
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petrographic classification, except for meta-feldspathic wackes containing less than 40%
300
matrix, which are chemically indistinguishable from metarkoses, despite their different
301
proportions of matrix (Fig. 5). Given the post-depositional processes that affected these
302
rocks during diagenesis and metamorphism, it is necessary to take into account that some
303
uncertainty is associated with the estimative of the matrix proportion (more than 10% -
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wackes), due to the potential generation of pseudo-matrix.
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5.1. Potential source-areas and weathering
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The granitic clasts of polymictic metaconglomerates from the Boturuna Formation,
308
which correspond to a broadly comagmatic suite of Paleoproterozoic (~2.2 Ga) age
309
(Henrique-Pinto and Janasi, 2010; Henrique-Pinto, 2012), bear important direct evidence
310
on the nature of the source areas of basal Formations of the São Roque Group. Pebbles of
311
other rock types (although much less abundant), include amphibolite and quartzite of
312
mature polycyclic quartzose detritus, revealing contributions from different sources.
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In order to infer processes affecting the sources of the studied metasedimentary
314
rocks, we used some of the indices that allow to evaluate the effects of processes as
315
weathering and metasomatism such as CIW (Chemical Index of Weathering; Harnois,
316
1988), CIA (Chemical Index of Alteration; Nesbitt and Young, 1982), PIA (Plagioclase
317
Index of Alteration; Fedo et al., 1995) and ICV (Index of Compositional Variability; Cox
318
et al., 1995) (Fig. 6). A few of our samples were not used in this evaluation: samples JP-20,
319
PJ-01 and JP-01 (Table 2) with high K2O contents, possibly due to late diagenetic and/or
320
metamorphic processes, and samples JP-04, MD-03a and MD-38, with secondary calcite
321
(the parameters used to quantify the weathering require that the sources of CaO are
322
exclusively silicate minerals).
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The CIW indicates that the particles derived or weathered from the source suffered
324
sedimentary sorting (Fig. 6A) and were deposited as sands and clays after moderate
325
degrees of weathering with CIA values between 51 and 85, while the ICV, used to evaluate
326
the original composition of the sources of shales and siltstones (Fig. 6B), illustrates the
327
chemical effects of weathering of the potential source. These values would correspond to
328
transformation of feldspar to illite, indicating that the highest degree of weathering with
329
kaolinite formation was not attained (Fig. 7).
10
ACCEPTED MANUSCRIPT The CIW values for most of the feldspatic wackes from the Boturuna Formation
331
(samples MD-03a, MD-04a, MD-26b, MD-36 and MD-01b) are similar to the granitic
332
clasts from the associated metaconglomerates (averages respectively 67 and 63), indicating
333
weak weathering (cf. Henrique-Pinto and Janasi, 2010). The PIA index excludes the
334
influence of K, which is much less mobile than Ca and Na, and shows a slightly larger
335
difference (averages respectively 57 and 49). The CIW and PIA of the Piragibu
336
metamudstones and of the other metapsmmites (metarenites, subarkoses, etc) are close to
337
100, reflecting near complete removal of Ca and Na from the sources.
339
5.2. Inferences on source areas from geochemistry
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The strong linear correlation of SiO2 with the main oxides Al2O3 (r= -0.99), Fe2O3
341
(r= -0.86), K2O (r= -0.92), TiO2 (r= -0.95) (Supplementary I, Fig. 8) is mainly related to
342
sedimentary sorting responsible for the concentration of these elements in the Al-rich clay
343
fraction. The largest scattering of MgO with small negative linear correlation relative to
344
SiO2 (r= -0.38) could reflect the presence of microlithic fragments of metabasic rocks,
345
found in small proportions in some metawacke samples; this could also be responsible for
346
the increase of CaO (up to 0.05 wt%). These increases might also in part reflect the
347
presence of dolomite/calcite as authigenic cement (not identified in thin section) or derived
348
from secondary hydrothermal processes.
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Many trace elements such as Cr (r= 0.87), Rb (r= 0.91), Ba (r= 0.82), V (r= 0.90),
350
Sc (r= 0.93) and Ga (r= 0.95) show very strong to strong positive correlation with Al2O3
351
(Supplementary I, Fig. 9), which reflects the preference of these elements for the clay
352
fraction in Al-rich sediments, and their depletion in quartz-rich fractions. The increasing
353
amounts of feldspar in the compositionally immature deposits (e.g., meta-feldspathic
354
wackes and metarkoses) could be responsible for the shifting of Sr, and the low contents of
355
V and Rb, compared to metamudstones and metaquartzarenites.
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The presence of metamafic clasts in metaconglomerates from the Boturuna
357
Formation (Henrique-Pinto and Janasi, 2010) is a clear physical evidence of the
358
contribution from basic sources. These clasts have trace element ratios typical of basic
359
magmatic rocks (e.g., Sc/Th Sc/La, Cr/, Cr/Sc, U/Th and Co/Th - Fig. 10B). Furthermore,
360
elements that are abundant in basic magmatic rocks and tend to accumulate in clay-rich
361
sediments (e.g., Ti, Ni, Cr, Co, Sc and V) are typically enriched in mudstones (e.g.,
362
Sawyer, 1986), compared with high-textural maturity rocks (Figs. 8 and 9).
11
ACCEPTED MANUSCRIPT 363
Compared with the compositions of sediments derived from different magmatic
364
sources presented by Cullers (2000), key trace-element ratios of our samples are clearly
365
within the range of siliciclastic sources [e.g., high La/Sc (1.9 to 26), Th/Sc (0.6 to 2.9),
366
La/Co (7.7 to 102), Th/Co (0.4 to 4.7) and Th/Cr (0.09 to 0.6) ratios]. Metamudstones from the Piragibu Formation are enriched in REE (Fig. 10 A; Table
368
3) and display more fractionated REE patterns (LaN/YbN= 15-40; GdN/YbN= 2.2-3.0;
369
∑HREE= 10-64 ppm) when
370
metasedimentary rocks from the Boturuna Formation. Well-defined negative Ce (Ce/Ce*=
371
0.34-0.51) and Eu (Eu/Eu*= 0.64-0.71) anomalies are common in the metamudstones, with
372
the exception of one sample (ND-08, which has no Ce anomaly and is less fractioned, as a
373
result of lower LREE contents).
to other (coarser-grained) siliciclastic
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compared
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The compositional more immature metasedimentary rocks (metarkoses and meta-
375
feldspathic wackes, Fig. 3) show REE behaviour broadly similar to the granitic clasts from
376
the metaconglomerates, with moderately fractionated REE patterns (LaN/YbN= 10-13),
377
high LREE contents (∑LREE= 111-183 ppm), and incipient negative Eu anomalies
378
(Eu/Eu*= 0.69-0.96). An Eu increase in some cases results in positive anomalies (Eu/Eu*=
379
1.08; sample JP-01), which may reflect feldspar concentration as a result of sedimentary
380
sorting (cf. Singh and Rajamani, 2001) or alternatively result from contributions of Eu-rich
381
sources (e.g., igneous rocks of intermediate composition with Eu/Eu* = 0.72-1.03; Fig.
382
10A).
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The nearest potential source areas with similar ages are found in basement nuclei of
384
the Açungui Domain (Kaulfuss, 2001; Ribeiro, 2006; Siga Jr. et al., 2007, 2011a). The
385
chemical composition of these rocks is similar to the granitic clasts of metaconglomerates
386
(Boturuna Formation) at a given silica content (65-78 wt.%) (Group 1 in Figs. 8 and 9).
387
Intermediate plutonic rocks (Group 2 in Figs. 8 and 9) are common in these basement
388
nuclei but have not been found as clasts in the metaconglomerates studied by Henrique-
389
Pinto and Janasi (2010). Small contributions from additional sources as well as igneous
390
rocks of intermediate composition (e.g., andesitic) are suggested by the presence of TiO2-
391
Ba-V-rich mudstones, which could not be explained only by mafic sources or simple
392
sedimentary sorting effect.
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393
The quartz-rich metasandstones are REE-poor (∑REE= 59-65 ppm) and have
394
relatively high LaN/SmN ratios (3.9-5.7), weakly fractionated patterns (LaN/YbN= 6-8), with
395
the exception of sample JP-19, which is depleted in HREE, resulting in a more fractionated
396
pattern with LaN/YbN= 21 (Fig. 10A). Strong positive linear correlations between ∑HREE 12
ACCEPTED MANUSCRIPT 397
and ∑LREE with Th (r= 0.86 and 0.85, respectively; Supplementary I) and between Y and
398
REE suggest an important control by heavy minerals such as monazite and xenotime. Ce-depleted REE patterns such as those shown by some metamudstone samples
400
(Fig. 11B) are commonly observed in seawater sediments (e.g., Shimizu and Masuda,
401
1977; Elderfield and Greaves, 1982). Furthermore, HREE-depleted metawackes and
402
metamudstones (Figs. 11 A and C) with positive Eu anomalies relative to post-Archean
403
Australian shales (Figs.11 C and D) could be an indication that additional volcanogenic
404
sources were present during sedimentation, which is also suggested by less negative ƐNd(t)
405
of two metamudstone samples.
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All samples have chemical compositions consistent with those expected from
407
sediments deposited in a passive margin basin, as shown by their REE patterns and by their
408
position in discrimination diagrams that identify the provenance signature (Fig. 12). This is
409
confirmed by the Sm-Nd isotope data that suggest predominantly older felsic Proterozoic
410
sources, with subordinate contributions from mafic crust (Figs. 13A and B).
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411 412
6. Sm-Nd isotope data from metamudstones
Previously available Sm-Nd isotope data for the São Roque Group rocks are
414
restricted to results presented by Dantas et al. (2000) for some metapelites and a single
415
amphibolite, which yielded Paleoproterozoic to Archaean (1.86-2.86 Ga) Nd TDM model
416
ages, and to a systematic study of ~2.2 Ga old granitic clasts and the framework of a
417
metaconglomerate from the Boturuna Formation (Henrique-Pinto et al., 2012) whose Nd
418
TDM model ages cluster at 2.6- 2.8 Ga.
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Our Sm-Nd isotope data (Table 4) were obtained in 17 representative samples of
420
metamudstones of the São Roque Group, most from the Piragibu Formation. The results
421
span approximately the same range of Nd TDM indicated by previous works (1.9-3.0 Ga),
422
but show a well-defined clustering in the 2.1-2.6 Ga interval, where two peaks can be
423
identified at ~2.2 and 2.4-2.5 Ga. Another small peak is defined at ~1.9 Ga by four samples
424
(Fig. 14B); older (>2.9 Ga) Nd TDM is associated with a few samples with
425
0.13 and is possibly slightly exaggerated by REE fractionation.
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147
Sm/144Nd>
426
The Sm-Nd isotope signatures of the metaconglomerate clasts from the Boturuna
427
Formation (Henrique-Pinto et al., 2012) and from the basement nuclei from the Açungui
428
Domain (Kaulfuss, 2001; Siga Jr. et al., 2011a) were used to calculate their ƐNd at the age
429
inferred for the deposition of the basal metasedimentary rocks of the SRS (~1.75 Ga). The
13
ACCEPTED MANUSCRIPT 430
ƐNd(1.75) values of the clasts (-7 to -10) and basement nuclei (-7 to -13) are more negative
431
compared to all metamudstones (+2 to -7), with the exception of sample ND-08 which has
432
ƐNd(1.75) = -9. The meta-feldspathic wacke from the Boturuna Formation has ƐNd(1.75)= -7, closer
434
to the values shown by the clasts, in agreement with its direct association with the
435
metaconglomerates (Fig. 14A). The least negative values of the metamudstones indicate
436
that other sources, younger and/or with less negative ƐNd at the age of deposition, also
437
contributed to the SRS metamudstones.
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A few samples with slightly positive ƐNd(1.75) (+1.4 to +2.4) were identified among
439
the metamudstones (Fig. 14A). These are located either to the north of the Jundiuvira Fault
440
(therefore outside the São Roque Domain, but corresponding to low-grade metamorphic
441
rocks not consistent with the metamorphic grade typical of the Socorro-Guaxupé Nappe),
442
or in the northeasternmost portion of the studied sector of the SRD (Fig. 1). Their positive
443
ƐNd(1.75)
444
contribution from younger sources, possibly including rocks such as the metabasalts dated
445
by Oliveira et al. (2008) at ~1.75 Ga, which have positive ƐNd(1.75).
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and corresponding youngest Nd TDM ages (1.88-1.93 Ga) must reflect a
The study of detrital zircons from metapsammitic rocks yields some important
447
clues to the identification of the sources of the São Roque Domain (Henrique-Pinto et al.,
448
2015). Granitic sources seem to be largely predominant for these sediments, which show
449
main peaks of zircon U-Pb ages in the same range as the Nd TDM, in some cases with a
450
bimodal distribution (2.2 and 2.4 Ga) (Fig. 14C). One explanation for this coincidence
451
could be the existence of sources with juvenile signature at this age range, therefore with
452
less negative ƐNd(1.75) than the metaconglomerate clasts studied by Henrique-Pinto et al.
453
(2012). To our knowledge, such rocks have not yet been documented in the literature so far
454
in the small paleoproterozoic basement nuclei described in the Apiaí Terrane (e.g., the
455
Tigre, Setuva and Betara nuclei in Açungui Domain). We note, however, that recent
456
studies have identified rocks with these characteristics in other parts of southeast Brazil,
457
such as the orthogneisses found as allocthonous basement fragments in the Andrelândia
458
Nappe System (Campos Neto et al., 2011) or the Serrinha Arc, part of the Mineiro Belt in
459
the southeastern tip of the São Francisco Craton (Teixeira et al., 1996; Ávila et al., 2010).
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460
14
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7. Discussion The classification based on modal allowed the division of clastic lithotypes from
463
the São Roque Domain into six subtypes. Samples with greater sedimentary maturity were
464
classified as meta-quartzarenites and meta-subarkoses; samples with lowest compositional
465
maturity as metarkoses and meta-feldspathic wackes; and those with low textural maturity
466
but high compositional maturity as metamudstones and meta-quartz wackes.
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The presence of plagioclase and alkali-feldspar in similar proportions in metarkoses
468
and meta-feldspathic wackes from the Boturuna Formation (in the Morro Doce region)
469
indicates that the main sources of these rocks are of granitic composition, and the
470
preservation of sedimentary petrofabrics with sub-euhedral feldspar in the framework
471
suggests that they are proximal, i.e., implies short transport distances. Additional sources
472
are indicated by the presence of lithic fragments of metabasic rocks and intraclasts of
473
quartzarenite, but these are always of minor modal proportions (less than 1%).
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The chemical classification using major elements shows great parallelism with the
475
modal classification, except for the metarkoses and meta-feldspathic wackes, which have
476
similar chemical behaviour notwithstanding their different proportions of matrix. The very
477
strong to strong negative linear correlation of SiO2 with the main major (Al2O3, Fe2O3,
478
K2O, TiO2) and trace elements (Cr, Rb, Ba, V, Ga) is attributed to sedimentary sorting and
479
concentration of these elements in the clay fraction in Al-rich sediments, which are
480
depleted in quartz.
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Evidence of the basic sources are suggested by the increase of Fe2O3, MnO, MgO
482
and high ratios of Sc/Th, Sc/La, Cr/Sc, U/Th and Co/Th. Furthermore, the accumulation of
483
elements derived from basic rocks into clay-rich sediments is reflected in Ti, Ni, Cr, Co, Sc
484
and V enrichments in mudstones, compared with the high-textural maturity rocks. The SRD metasediments are inferred to have been deposited in a passive margin
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481
486
environment having older Proterozoic to Archean basement sequences as main sources, as
487
indicated by the geochemical signatures of both the proximal deposits of the Boturuna Fm.
488
and the distal deposits of the Piragibu Fm, suggesting that the deposition of these two units
489
may have been at least in part contemporaneous.
490
The Nd TDM ages of the SRD metamudstones (1.9-2.5 Ga) are characteristically
491
slightly younger than those of the granite clasts that are an important source of the
492
metaconglomerates and associated metarkoses of the Boturuna Fm. and correspond to 2.2
493
Ga products of reworking of older Archean (2.7 Ga) crust (Henrique-Pinto et al., 2012).
494
Exposures of basement rocks are unknown in the SRD, but are found in basement nuclei in
15
ACCEPTED MANUSCRIPT the Açungui Domain (orthogneisses from the Tigre, Setuva and Betara nuclei; Siga Jr et
496
al., 2007). These rocks have similar Paleoproterozoic (2.2 Ga) ages and Archean Nd TDM,
497
but are compositionally different from the São Roque metaconglomerate clasts (which are
498
typically more leucocratic). Migmatites from a basement exposure in the Embu Terrane
499
(Rio Capivari Complex) are also ~2.1 Ga old and have Archean (2.9-3.2 Ga) Nd TDM
500
(Babinski et al., 2001). These data imply that the compositions of typical SRD
501
metamudstones require involvement of additional sources to explain their lower Nd TDM
502
relative to the basement granite clasts and basement exposures in the Ribeira Belt.
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A potential way to lower the εNd(t) and consequently the Nd TDM of the
504
metamudstones would be the contribution from mantle-derived basic volcanic rocks
505
broadly coeval with deposition. Indeed, basic volcanic rocks are inferred from whole-rock
506
geochemistry as a contributing source to the SRD metamudstones, and possibly also to the
507
meta-sandstones (from the trace-element geochemistry of detrital zircons; Henrique-Pinto
508
et al., 2015). We consider it improbable, however, that such contribution is strong enough
509
to explain the observed shift in Nd TDM, given the rarity of mafic-derived detrital zircons in
510
the meta-sandstones and the low (0.09-0.13)
511
(since higher Sm/Nd ratios are more characteristic of basic rocks).
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503
147
Sm/144Nd ratios of the metamudstones
U-Pb dating and geochemistry of detrital zircons from SRD metasandstones
513
indicated that their sources are similar to those of the marginal belts of the São Francisco
514
Craton, and therefore the São Francisco Paleoplate might extend southwestward and
515
constitute the basement of the Ribeira Belt (Henrique-Pinto et al., 2015). The Sm-Nd
516
isotope signature of the oldest (pre-1.4 Ga) passive-margin sequences of the Andrelândia
517
Group (e.g., Campestre Formation; Westin and Campos Neto, 2013) is indeed very similar
518
to that of the SRD metasediments, suggesting that they might be correlative. In this
519
context, it is possible that at least part of the lowering in the Nd TDM of the SRD
520
metamudstones could reflect contributions from ~2.2 Ga juvenile arc terranes such as those
521
exposed in the southern portion of the São Francisco Craton (e.g., the Mineiro Belt; Ávila
522
et al., 2010, 2014; Teixeira et al., 2015) which may continue southwestward as part of the
523
basement of the Andrelândia Group (cf. Fetter et al., 2001; Campos Neto et al., 2011).
524
8. Conclusions
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525
Petrography, geochemistry and Sm-Nd isotopic systematics of metasedimentary
526
rocks were used as provenance tools to estimate the sedimentary environments of the
16
ACCEPTED MANUSCRIPT 527
Proterozoic São Roque Domain. The main conclusions that can be addressed from our
528
study are:
529
(i) The sedimentary particles were subject to moderate degrees of weathering as indicated
531
by CIA values between 51 and 85. These values correspond to transformation of feldspar
532
to illite, indicating that the highest degree of weathering with kaolinite formation was not
533
attained.
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530
534
(ii) Strong negative linear correlation of SiO2 with the main major (Al2O3, Fe2O3, K2O,
536
TiO2) and trace elements (Cr, Rb, Ba, V, Ga) is attributed to sedimentary sorting and
537
concentration of these elements in the clay fraction. Evidences of basic magmatic sources
538
in some samples are the increase of Fe2O3, MnO, MgO and higher ratios of Sc/Th, Sc/La,
539
Cr/Sc, U/Th and Co/Th.
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540
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535
(iii) The sediments are inferred to have been deposited in a passive margin environment
542
having older Proterozoic to Archean basement sequences as main sources. The Nd TDM
543
ages (1.9-2.5 Ga) are slightly younger than those of the granite clasts of the Boturuna Fm.,
544
which correspond to 2.2 Ga products of reworking of older Archean (2.7 Ga) crust.
545
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541
(iv) Similar petrography, geochemistry and isotope characteristics among metasedimentary
547
rocks in both sides of Jundiuvira Shear Zone suggest that the first-order limits and
548
discontinuities traditionally established for the Ribeira Belt are not defined by the strike-
549
slip fault systems to separate distinct domains (Socorro-Guaxupé and Apiaí).
550
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546
(v) Geochemistry, U-Pb zircon dating and Sm-Nd isotopes similarities with SRD, are
552
found in southeast part of basement nuclei in the Apiaí Domain (Tigre, Setuva and Betara
553
nuclei) and lowering in the Nd TDM could reflect contributions from ~2.2 Ga juvenile arc
554
terranes such as those exposed in the southern portion of the São Francisco Craton (e.g.,
555
the Mineiro Belt) which may continue southwestward as part of the basement of the
556
Andrelândia and Itapira Groups.
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557
17
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8. Acknowledgements The authors acknowledge financial support by CNPq (Proc. 143521/2008-0) and
560
Fapesp (Proc. 2012/04148-0). Comments by Edward W. Sawyer and Antonio Carlos B.C.
561
Vasconcellos in preliminary version of this manuscript are much appreciated. Careful
562
reviews and suggestions by two anonymous reviewers and by Reinhardt A. Fuck helped
563
improve the final version.
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9. References
566
Ávila, C.A., Teixeira, W., Cordani, U.G., Moura, C.A.V., Pereira, R.M., 2010. Rhyacian (2.23-2.20
567
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568
isotopic evidence from the Serrinha magmatic suíte, Mineiro belt. Journal of South
569
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Ávila, C.A., Teixeira, W., Bongiolo, E.M., Dussin, I.A., Vieira, T.A.T., 2014. Rhyacian evolution of
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subvolcanic and metasedimentary rocks of the southern segment of the Mineiro belt, Sao
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Francisco Craton, Brazil. Precambrian Research, 243, 221-251.
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Babinski, M., Tassinari, C.C.G., Nutman, A.P., Sato, K., Iyer, S.S., 2001. U/Pb SHRIMP zircon
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ages of migmatites from the basement of the Embu Complex, Ribeira fold belt, Brazil:
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Indications for ~1.4-1.3 Ga Pb-Pb and Rb-Sr" isochron" ages of no geological meaning, III
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South American Simposium on Isotope Geology. Extended Abstracts, Pucón, Chile, 91-
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Basei, M.A.S., Frimmel, H.E., Nutman, A.P., Preciozzi, F., 2008. West Gondwana amalgamation
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Basei, M.A.S., Nutman, A.P., Siga Jr, O., Passarelli, C.R., Drukas, C.O., 2009. The evolution and
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Bahlburg, H., Dobrzinski, N., 2009. A review of the Chemical Index of Alteration (CIA) and its
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Geological Record of Neoproterozoic Glaciations. Geological Society, London, 1-31.
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Bauluz, B., Mayayo, M.J., Fernandez-Nieto, C., Lopez, J.M.G., 2000. Geochemistry of Precambrian
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Bergmann, M., Fairchild, T.R., 1985. Estromatólitos do Grupo São Roque. Proterozóico Superior.
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Campanha, G.A.C., Brito Neves, B.B., 2004. Frontal and oblique tectonics in the Brazilian Shield. Episodes, 27(4), 255-259.
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Campanha, G.A.C., Sadowski, G.R., 1999. Tectonics of the southern portion of the Ribeira Belt (Apiaí Domain). Precambrian Research, 98(1-2), 31-51.
Campanha, G.A.C., Basei, M.S., Tassinari, C.C.G., Nutman, A.P., Faleiros, F.M., 2008.
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Constraining the age of the Iporanga Formation with SHRIMP U-Pb zircon: Implications
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for possible Ediacaran glaciation in the Ribeira Belt, SE Brazil. Gondwana Research,
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Campanha, G.A.C., Basei, M.A.S., Faleiros, F.M., Tassinari, C.C.G., Nutman, A., Vasconcelos, P.,
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Boturuna Formation. Geologia USP, 12(3), 21-32.
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geological map of the São Roque Domain, North of São Paulo City - Brazil. Journal of
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Maps, 1-6. Henrique-Pinto, R., Janasi, V.A., Vasconcellos, A.C.B.C., Sawyer, E.W., Barnes, S.-J., Basei,
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Juliani, C., Beljavskis, P., Schorscher, H.D., 1986. Petrogênese do Vulcanismo e Aspectos
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Juliani, C., Beljavskis, P., 1995. Revisão da litoestratigrafia da faixa São Roque/Serra do Itaberaba SP. Revista do Instituto Geológico, 16, 33-58.
Juliani, C., Hackspaker, P., Dantas, E.L., Fetter, A.H., 2000. The Mesoproterozoic volcano-
719
sedimentary Serra do Itaberaba Group of the central Ribeira Belt, São Paulo, Brazil:
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721
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Kaulfuss, G.A., 2001. Geocronologia dos Núcleos de Embasamento Setuva. Betara e Tigre. Norte de Curitiba-Paraná. Master thesis. Instituto de Geociências – USP. Mantovani, M.S.M., Brito Neves, B.B., 2005. The Paranapanema Lithospheric Block: Its
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Importance for Proterozoic (Rodinia, Gondwana) Supercontinent Theories. Gondwana
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McBride, E.F., 1963. A classification of common sandstones. Journal of Sedimentary Petrology, 33(3), 664-669.
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McLennan, S.M., Hemming, S.R., 1991. Samarium/neodymium elemental and isotopic systematics in sedimentary rocks. Geochimica et Cosmochimica Acta, 56, 887-898.
731
McLennan, S.M., Taylor, S.R., McCulloch, M.T., Maynard, J.B., 1990. Geochemical and Nd-Sr
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isotopic composition of deep-sea turbidites: Crustal evolution and plate tectonic
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associations. Geochimica et Cosmochimica Acta, 54, 2015-2050.
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McLennan, S.M., Hemming, S., McDaniel D.K., Hanson, G.N., 1993. Geochemical approaches to
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sedimentation, provenance, and tectonics. Geological Society of America, Special Paper,
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McLennan, S.M., Hemming, S.R., Taylor, S.R., Eriksson, K.A., 1995. Early Proterozoic crustal
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evolution: Geochemical and N-Pb isotopic evidence from metasedimentary rocks,
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southwestern North America. Geochimica et Cosmochimica Acta, 59(6), 1153-1177.
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Mori, P.E., Reeves, S., Correia, C.T., Haukka, M., 1999. Development of a fused glass disc XRF
741
facility and comparison with the pressed powder pellet technique at Instituto de
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Geociências, Universidade de São Paulo. Revista Brasileira de Geociências, 29, 441-446. Navarro, M.S., Ulbrich, H.H.G.J., Andrade, S., Janasi, V.A., 2002. An adaptation of ICP-OES
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routine determination techniques for the analysis of rare-earth elements by
745
chromatographic separation in geologic materials: tests with reference materials and
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granitic rock. Journal of Alloys and Compounds, Amsterdam, 344, 40-45.
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Nesbitt, H.W., Young, G.M., 1982. Early Proterozoic climates and plate motions inferred from
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major element chemistry of lutites. Nature, 299, 715-717.
Nesbitt, H. W., Young, G.M. 1984. Prediction of some weathering trends of plutonic and volcanic
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rocks based on thermodynamic and kinetic considerations. Geochimica et Cosmochimica
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Nesbitt, H.W., Young, G.M., 1989. Formation and Diagenesis of Weathering Profiles. The Journal of Geology, 97(2), 129-147.
Nesbitt, H.W., Markovics, G., 1997. Weathering of granodioritic crust, long-term storage of
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elements in weathering profiles, and petrogenesis of siliciclastic sediments. Geochimica et
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and Sorting on the Petrogenesis of Siliciclastic Sediments, with Implications for
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Provenance Studies. The Journal of Geology, 104(5), 525-542. Oliveira, M.A.F. de., Melo, R.P., Nardy, A.J.R., Arab, P.B., Trindade, I., 2008. New U/Pb
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Palaeoproterozoic zircon age for the Cajamar metabasite, São Roque Group, Central
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Ribeira Belt, Southeastern Brazil. In: VI South American Symposium on Isotope Geology.
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Metavulcanossedimentares da Região do Betara (PR). Master thesis. Instituto de
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Geociências – USP.
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Roser, B.P., Korsch, R.J., 1988. Provenance signatures of sandstone-mudstone suites determined
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using discriminant function analysis of major-element data. Chemical Geology, 67, 119-
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Sato, K., Tassinari, C.C.G., Kawashita, K., Petronilho, L., 1995. Método geocronológico Sm- Nd no IG-USP e suas aplicações. Anais da Academia Brasileira de Ciência, 67(3), 315-336.
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Sawyer, E.W., 1986. The influence of source rock type, chemical weathering and sorting on the
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geochemistry of clastic sediments from the Quetico mesedimentary belt, Superior
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Province, Canada. Chemical Geology, 55, 77-95.
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Shimizu, H., Masuda, A., 1977. Cerium in chert as an indication of marine environment of its formation. Nature, 266, 346-348. Siga Jr, O., Basei, M.A.S., Passarelli, C.R., Harara, O.M., Sato, K., Cury, L.F., Prazeres Filho, H.J.,
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2007. Geocronologia das Rochas Gnáissico-Migmatíticas e Sienograníticas do Núcleo
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Setuva (PR): implicações tectônicas. Revista Brasileira de Geociências, 37(1), 114-128.
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Siga Jr, O., Basei, M.A.S., Sato, K., Passarelli, C.R., Nutman, A., McReath, I., Prazeres Filho,
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H.J.D., 2011a. Calymmian (1.50-1.45 Ga) magmatic records in Votuverava and Perau
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sequences, south-southeastern Brazil: Zircon ages and Nd-Sr isotopic geochemistry.
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Siga Jr, O., Cury, L.F., McReath, I., Ribeiro, L.M.A.L., Sato, K., Basei, M.A.S. and Passarelli, C.R.,
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2011b. Geology and geochronology of the Betara region in south-southeastern Brazil:
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Evidence for possible Statherian (1.80-1.75 Ga) and Calymmian (1.50-1.45 Ga) extension
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Siga Jr., O., Basei, M.A.S., Passarelli, C.R., Sato, K., Cury, L.F., McReath, I., 2009. Lower and
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Upper Neoproterozoic magmatic records in Itaiacoca Belt (Paraná-Brazil): Zircon ages
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and lithostratigraphy studies. Gondwana Research, 15(2), 197-208. Singh, P., Rajamani, V., 2001. REE geochemistry of recent clastic sediments from the Kaveri
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Tassinari, C.C.G., Munhá, J.M.U., Ribeiro, A., Correia, C.T., 2001. Neoproterozoic oceans in the
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Ribeira Belt (southeastern Brazil): The Pirapora do Bom Jesus ophiolitic complex:
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Episodes, 24, 245-250.
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discussion). Phil. Trans. R. Soc. Lond., 301(1461), 381-399.
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Teixeira, W., Carneiro, M.A., Noce, C.M., Machado, N., Sato, K., Taylor, P.N., 1996. Pb, Sr and Nd
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isotope constraints on the Archaean evolution of gneissic-granitoid complexes in the
804
southern São Francisco Craton, Brazil. Precambrian Research, 78, 151-164.
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Teixeira, W., Ávila, C.A., Dussin, I.A., Neto, A.C., Bongiolo, E.M., Santos, J.O., Barbosa, N.S.
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Minas accretionary orogeny: zircon U-Pb-Hf and geochemical evidences. Precambrian
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Trouw, R.A.J., Peternel, R., Ribeiro, A., Heilbron, M., Vinagre, R., Duffles, P., Trouw, C.C.,
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Fontainha, M., Kussama, H.H., 2013. A new interpretation for the interference zone
811
between the southern Brasília belt and the central Ribeira belt, SE Brazil. Journal of South
812
American Earth Sciences, 48, 43-57. Van Schmus, W.R., Tassinari, C.C.G., Cordani, U.G., 1986. Estudo geocronológico da parte inferior
814
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Vauchez, A., Tommasi, A., Egydio-Silva, M., 1994. Self-indentation of a heterogeneous continental lithosphere. Geology, 22(11), 967-970.
817
Vlach, S.R.F., 2001. Microprobe monazite constraints for an early (ca. 790 Ma) Brasiliano Orogeny:
819
The Embu Terrane, Southeastern Brazil., III South American Symposium on Isotope
820
Geology. Extended Abstracts, Pucón, Chile, 26-268.
Westin, A., Campos Neto, M. C., 2013. Provenance and tectonic setting of the external nappe of the Southern Brasília Orogen. Journal of South American Earth Sciences, 48, 220-239.
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FIGURE CAPTIONS
826
Figure 1: Simplified geological map of a portion of central-eastern Brazil, with emphasis on the
828
São Francisco Craton, its marginal sedimentary successions and the Ribeira Fold Belt (modified
829
from Bizzi, 2003).
830
Figure 2: (A)- Regional geological map modified from Campos Neto (2000). 1- Phanerozoic
831
sedimentary and associated Mesozoic intrusive rocks (Paraná Basin); 2- Neoproterozoic late and
832
post-orogenic granites; 3- (garnet)-(muscovite)-biotite granite; 4- porphyritic biotite granite; 5-
833
porphyritic (hornblende) biotite granite; 6- Socorro Guaxupé Domain (with predominance of
834
garnet-bearing migmatites); 7- Embu Domain: basement Paleoproterozoic gneisses; 8- Embu
835
Domain: cover metasupracrustal rocks; 9- Apiaí Terrane: São Roque and Açungui Groups; 10-
836
Serra do Itaberaba Group; 11- Costeiro Complex. (B)- Geological map of the central part of the
837
São Roque Domain and neighboring southernmost Socorro-Guaxupé Domain based in Henrique-
838
Pinto et al. (2014). 1- São Paulo Basin (Cenozoic); 2- Neoproterozoic shear zones with mylonite
839
and
840
(Neoproterozoic); 5- Socorro-Guaxupé Domain (paragneisses and migmatites); 6- Pirapora do Bom
841
Jesus Formation (metalimestones and metadolomites); 7= amphibolites, metatuffs and banded iron
842
formations (Pirapora do Bom Jesus Formation/Serra do Itaberaba Group (?)) ; 8-9- Serra do
843
Itaberaba Group (8= Kyanite-staurolite schists; 9= calc-silicate rocks and tremolite marbles); 10-
844
15- São Roque Group (10= metawackes; 11= metamudstones; 12= meta-quartzarenites and meta-
AC C
EP
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827
ultramylonite;
3-
Undifferentiated
granites
(Neoproterozoic);
4-
quartz
sienite
25
ACCEPTED MANUSCRIPT subarkoses; 13= meta-feldspathic wackes and meta-quartzwackes; 14= metaconglomerates; 15=
846
acid metavolcanic rocks); 16- Basement (?) orthogneisses.
847
Figure 3: São Roque Domain samples plotted on ternary diagram (QFL) Q=quartz, F=feldspar,
848
L=lithic fragments; fields after McBride (1963) and Dott (1964).
849
Figure 4: Photomicrographs of metasedimentary rocks of São Roque Domain: A- meta-
850
quartzarenite; B- meta-subarkose; C- metarkose; D- meta-feldspathic wacke; E- meta-quartz
851
wacke; F- metamudstone (left, parallel polarizers; right, crossed polarizers).
852
Figure 5: Chemical classification diagram [log (SiO2/Al2O3) versus log(Fe2O3/K2O)] (Herron,
853
1988) for samples of the São Roque Domain.
854
Figure 6: Relationship between weathering intensity and sedimentary sorting: A- CIW=
855
[Al2O3/(Al2O3+CaO+N2O)*100] (Chemical Index Weathering – Harnois, 1988) x Al2O3 and B-
856
ICV= [(Fe2O3+MnO+MgO+CaO+N2O+K2O+TiO2)/Al2O3] (Index of Compositional Variability –
857
Cox et al., 1995) x CIA= [Al2O3/(Al2O3+CaO+N2O+K2O)*100] (Chemical Index of Alteration -
858
Nesbitt and Young, 1982).
859
Figure 7: Chemical composition of São Roque metasedimentary rocks in the A-CN-K diagram
860
(Nesbitt and Young, 1982). 1 – average granitic rocks, 2 – average adamellite, 3 – average
861
granodiorite, 4 – average tonalite, 5 – average gabbro (trends plotted according to Nesbitt and
862
Young, 1989).
863
Figure 8: Variation diagrams for major elements versus SiO2 in metasedimentary rocks of the São
864
Roque Domain. Fields 1 – 2 represent potential sources compiled from Kaulfuss (2001); basic,
865
granitic and sedimentary sources represent clasts of polymictic metaconglomerates of the Boturuna
866
Formation (Henrique-Pinto and Janasi, 2010).
867
Figure 9: Variation diagrams for trace elements versus SiO2 in metasedimentary rocks of the São
868
Roque Domain. 1 – 2 represent potential granitic sources compiled from Kaulfuss (2001); basic,
869
granitic and sedimentary sources represent clasts in polymictic metaconglomerates of the Boturuna
870
Formation (Henrique-Pinto and Janasi, 2010).
871
Figure 10: (A) - Chondrite-normalized (Taylor and McLennan, 1985) rare-earth element patterns
872
for metasedimentary rocks of São Roque Domain. Granitic and intermediate potential sources
873
compiled from Kaulfuss (2001), clasts of metaconglomerates compiled from Henrique-Pinto and
874
Janasi. (2010); (B) - Multi-elementary diagram using to discriminate felsic from mafic sources.
875
Values for La, Eu, Gd and Yb were normalized by chondrite (Taylor and McLennan, 1985).
876
Figure 11: (A) and (B) - Chondrite-normalized (Taylor and McLennan, 1985) rare-earth element
877
patterns, (C) and (D) - PAAS-normalized (Taylor et al., 1981) rare-earth element patterns. Average
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of metawackes and metamudstones from the São Roque Domain. PM= Passive Margin; OIA=
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Oceanic Island Arc; CIA= Continental Island Arc, by Shimizu and Masuda (1977).
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Figure 12: São Roque Domain samples plotted on K2O/Na2O vs. SiO2 and SiO2/Al2O3 vs.
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K2O/Na2O provenance signature discrimination diagram of Roser and Korsch (1988).
AC C
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TE D
M AN U
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RI PT
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ACCEPTED MANUSCRIPT Figure 13: (A) - Plot of ƐNd versus Th/Sc ratio (McLennan et al., 1990) and (B) - Plot of ƒSm/Nd
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versus ƐNd (McLennan and Hemming, 1991) for metamudstones of the Piragibu Formation, São
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Roque Domain.
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Figure 14: (A) ƐNd versus TDM (Ga) diagram for metamudstones of Piragibu Formation (including
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one sample of meta-felspathic wacke from Boturuna Formation; Henrique-Pinto et al., 2012), São
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Roque Domain; DM: evolution line of depleted mantle (De Paolo, 1988); (B) histogram with peaks
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of TDM ages (including samples compiled from Dantas et al., 2000) and (C) population of detrital
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zircons of São Roque Domain from Henrique-Pinto et al. (2015).
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TABLE CAPTIONS
SC
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RI PT
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Table 1: Modal mineralogy of metasedimentary rocks of São Roque Domain (500 points per
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section).
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Table 2: Results of chemical analyses (XRF) of metasedimentary rocks of the São Roque Domain.
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n.a.= not analysed;