The Neoproterozoic Sergipano Orogenic Belt, NE Brazil - A Complete Plate Tectonic Cycle in Western Gondwana

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Precambrian Research 181 (2010) 64–84

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he Neoproterozoic Sergipano orogenic belt, NE Brazil: A complete plate tectonicycle in western Gondwana

lson P. Oliveiraa,∗, Brian F. Windleyb, Mario N.C. Araújoc

Institute of Geosciences, P.O. Box 6152, University of Campinas – UNICAMP, Rua João Pandiá Calógeras, 51, 13083-970 Campinas, SP, BrazilDepartment of Geology, University of Leicester, Leicester LE1 7RH, UKCENPES, Petrobrás, 21941-598 Rio de Janeiro, Brazil

r t i c l e i n f o

rticle history:eceived 24 September 2009eceived in revised form 29 April 2010ccepted 11 May 2010

eywords:ergipano Beltestern Gondwana

eoproterozoicectonic evolutioneochronologyrazil

a b s t r a c t

The Neoproterozoic Sergipano Belt formed by the collision of the Pernambuco-Alagoas Block in the northwith the São Francisco Craton in the south, but the timing, duration and mechanics of this amalgamationare poorly understood. The belt is divided into the Canindé, Poco Redondo-Marancó, Macururé, VazaBarris, and Estância lithostratigraphic domains; the first three are composed of plutonic, volcanic andsedimentary rocks and the last three of sedimentary rocks. Our new field, structural, and geochemicaldata, and Sm–Nd, Ar–Ar and U–Pb geochronology provide robust constraints for the following evolution.A Mesoproterozoic (∼980–960 Ma) continental arc (Poco Redondo tonalitic gneisses) developed on themargin of the Palaeoproterozoic Pernambuco-Alagoas Block. Extension of this continental block gaverise to (i) A-type crustal granites and associated sedimentary rocks on the stretched, rifted margin ofthe Poco Redondo-Marancó Domain, (ii) the Canindé rift sequence between the Pernambuco-AlagoasBlock and the Poco Redondo/Marancó domain, (iii) a passive margin on the southern boundary of thePernambuco-Alagoas Block on which sediments were deposited after 900 Ma, (iv) and a second passivemargin on the São Francisco Craton. In the Canindé Domain, rifting continued until ca. 640 Ma and led toemplacement of a bimodal association of A-type granite (715 Ma) and continental mafic volcanic rocks, acontinental-type layered gabbroic complex (ca. 700 Ma), magma-mingled gabbro/quartz–monzodiorite(688 Ma), and rapakivi granites (684 Ma and 641 Ma). Deformed pillow basalts and interleaved marblelenses are likely ocean floor relicts in the Canindé Domain. Closure of the Canindé oceanic basin beganat ca. 630 Ma with the intrusion of arc-type granitic plutons. Convergence of the Pernambuco-AlagoasBlock and the São Francisco Craton led to deformation on the passive margins and granite emplacementin the Macururé (628–625 Ma, and 590–570 Ma), Canindé (ca. 621 Ma) and Poco Redondo-Marancó (ca.
625 Ma) domains. A small oceanic basin was most likely subducted beneath the Poco Redondo-MarancóDomain to account for the presence of 602 Ma arc-type volcanic rocks. Shortly after, exhumation of thePernambuco-Alagoas Block and Canindé, Poco Redondo-Marancó and Macururé domains in the northled to deposition of uppermost clastic sediments in the Estância and Vaza Barris domains in the south,possibly in a foreland basin, and to final thrusting of the continental margin sedimentary rocks onto theSão Francisco Craton. Our results indicate that the construction of western Gondwana involved a ca. 300
of pl
million years long history
. Introduction

Following the breakup of Rodinia, continental blocks re-malgamated to form western Gondwana (West Africa–NE South
merica) and eastern Gondwana (India–Australia–Antarctica)efore final construction of the Gondwanan supercontinent in theeoproterozoic (McWilliams, 1981). Whereas the history of amal-amation of eastern Gondwana is increasingly well constrained
∗ Corresponding author. Tel.: +55 19 35215158.E-mail address: [email protected] (E.P. Oliveira).

301-9268/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.precamres.2010.05.014

ate breakup and collision.© 2010 Elsevier B.V. All rights reserved.

(Collins and Pisarevsky, 2005) that of western Gondwana is stillpoorly understood. In order to construct a viable geodynamic modelfor the evolution of western Gondwana, it is important to under-stand the detailed evolution of key individual orogenic belts, such asthe Aracuai, Ribeira, Sergipano, Dahomeyide, Rokelide, and Ouban-guide (Boullier, 1991; Culver et al., 1991; Trompette, 1997; Neveset al., 2000; Brito Neves et al., 2002). Post-collisional indentation
and extrusion between the West African, Amazonian and São Fran-cisco/Congo cratons at ca. 630–580 Ma (Caby et al., 1995) gaverise to a major dextral transcurrent fault system in the BorboremaProvince of NE Brazil and the Transaharan belt of NE Africa thattransects the orogenic belts (Fig. 1). In order to improve under-
dx.doi.org/10.1016/j.precamres.2010.05.014

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E.P. Oliveira et al. / Precamb

tanding of the mode of construction of western Gondwana, we
ere provide new multidisciplinary data and a new plate tectonicodel for the Sergipano orogenic belt.The Neoproterozoic Sergipano Belt, located on the northern
argin of the São Francisco-Congo craton, was first interpreted

ig. 1. Palaeogeographic reconstruction showing the connection between the Borboremhe main gneissic blocks and shear zones are indicated. Arrow shows the Sergipano Belt

esearch 181 (2010) 64–84 65

as a geosyncline (Humprey and Allard, 1969; Santos and Silva
Filho, 1975), later as a collage of tectono-stratigraphic terranes ormicroplates (Davison and Santos, 1989), and more recently as afold-and-thrust belt, the southern part of which was produced byinversion of a passive continental margin (D’el-Rey Silva, 1999).
a Province (in Brazil) and Trans-Saharan belt (in NW Africa) in the Neoproterozoic.of Fig. 2.

66 E.P. Oliveira et al. / Precambrian Research 181 (2010) 64–84

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ig. 2. The Sergipano Belt and its division into domains (modified after D’el-Rey SilMJSZ, SMASZ and ISZ stand, respectively, for Macururé, Belo Monte-Jeremoabo, Some; JPD – Jirau do Ponciano dome. Towns cited in text: (1) Gararu, (2) Porto da F

owever, the absence of constraining data on the geochronologicalvolution, isotope geochemistry, absolute timing of amalgamationvents, and the bulk kinematics involved has led to major contro-ersial interpretations of the geodynamic evolution. Our new dataill help to resolve some of these arguments.

First, we will evaluate current knowledge of the Sergipano Belt;econd, we will present new information on its geochronology,hole-rock geochemistry, isotope geochemistry, and structural

eology.

. The Sergipano Belt

The Sergipano Belt represents the western segment of the majorubanguide orogen that extends into NW Africa (Trompette, 1997,000). It consists of a triangular-shaped, E-SE- to W-NW-trendingelt located between the São Francisco-Congo Craton to the south,nd the Pernambuco-Alagoas Block to the north (Fig. 2).

In spite of controversy about its tectonic evolution, there isgeneral consensus about the subdivision of the Sergipano Belt

nto five lithotectonic domains, namely from N to S: Canindé, Pocoedondo-Marancó, Macururé, Vaza Barris and Estância, which areutually separated by the Neoproterozoic shear zones of Macu-

uré, Belo Monte-Jeremoabo, São Miguel do Aleixo, and ItaporangaFig. 2) (Davison and Santos, 1989; Silva Filho, 1998). Located in theorth of the belt are allochthonous domains/terranes (Marancó-oco Redondo and Canindé) accreted during the Neoproterozoic.
he three domains to the south (Estância, Vaza Barris and Macu-uré) largely consist of metasedimentary rocks, the provenance ofhich is constrained by Nd model ages and detrital zircon U–Pb
ges. Our description of the domains will be from S to N. We do notnclude the Rio Coruripe and Vicosa domains (cf. Silva Filho and

99). The Poco Redondo-Marancó Domain is separated into two sub-domains. MSZ,guel do Aleixo and Itaporanga shear zones. ID – Itabaiana dome; SD – Simão Dias3) Gracho Cardoso, (4) Lagarto, and (5) Macururé.

Torres, 2002) in this account because the former is a continuationof the Macururé Domain to the north, and the latter is still poorlymapped and age-dated.

2.1. Lithology and age of different domains

2.1.1. Estância DomainThis domain consists of a 1–3.5-km thick blanket of sub-

horizontal, undeformed to weakly deformed platform sedimentsof the Estância Group (Silva Filho et al., 1978; Saes and Vilas Boas,1983; Davison and Santos, 1989). The base of the group is rep-resented by 20–30 m-thick autochthonous unit of conglomerates,argillites, sandstones and diamictites (Juetê Formation), succeededby ca. 40–200 m-thick limestones and dolomites, sometimes withstromatolites (Acauã Formation), overlain by feldspathic sand-stones, siltstones, and argillites that contain well-preserved ripplemarks, mudcracks and dewatering structures (Lagarto Formation).These platform sediments are overlain by 3-km thick, molasse-type, clastic conglomerates, sandstones, siltstones and argillites ofthe Palmares Formation (Fig. 3) (Silva Filho et al., 1978; Saes andVilas Boas, 1989).

Brito Neves et al. (1977), Silva Filho et al. (1978), and Dominguez(1993) suggested that the uppermost Estância Group sediments,mainly the Palmares Formation, were deposited in a foreland basinfills produced by erosion of the Sergipano Belt during the Neo-proterozoic orogeny. This would imply a syn- to late-collisional
sedimentary influx towards the São Francisco Craton. On the otherhand, D’el-Rey Silva (1999) suggested that the sediments werederived by erosion of mountains in the São Francisco craton tothe south; this model implies that all sediments in the Estân-cia Domain should yield depleted-mantle Nd model ages (TDM),

E.P. Oliveira et al. / Precambrian Research 181 (2010) 64–84 67

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ig. 3. Stratigraphy of the Estância Domain. Contacts between formations arenconformities. Thicknesses are not drawn to scale.

r detrital zircon grains no younger than the Palaeoproterozoic,ecause the relevant rocks from the São Francisco Craton are olderhan 2.0 Ga. Fig. 4 shows Nd model ages for the three sedimentaryomains of the Sergipano Belt and their potential sources. Sam-les from the two uppermost formations of the Estância Domain
how TDM ages in the time range 1.7–1.4 Ga, whereas three samplesrom the basal Juetê Formation indicate ages between 2.9 Ga and.1 Ga. These ages suggest that the São Francisco craton may haveupplied clasts to the Juetê Formation, but that younger sources
ig. 4. Depleted-mantle Nd-model ages for clastic sedimentary domains of theergipano Belt and their potential sources – SFC – São Francisco craton, PEAL –ernambuco-Alagoas Block, Itabaiana dome and Poco Redondo migmatites (modi-ed after Oliveira et al., 2005, 2006).

Fig. 5. Detrital zircon histogram for sandstone of the Lagarto Formation (afterOliveira et al., 2006).

are required to explain the TDM ages of the Lagarto and PalmaresFormations. U–Pb SHRIMP detrital zircon ages of sandstone fromthe Lagarto Formation yield age clusters at 570 Ma, 634 Ma, and958 Ma with a few Palaeoproterozoic and Archaean grains (Fig. 5),this implying deposition after 570 Ma, which is more consistentwith the foreland basin model, at least for the two younger for-mations. On the other hand, detrital zircons from the basal JuetêFormation are not younger than 2073 Ma (Oliveira, 2008), poorlyconstraining sediment deposition to anytime between 2.0 Ga and0.6 Ga.

2.1.2. Vaza Barris DomainThe Vaza Barris Domain is more deformed than the Estância

Domain and for this reason its stratigraphy is more contentious. Thedomain contains several formations that were previously groupedinto the Miaba and Vaza Barris Groups (Allard, 1969; Humprey andAllard, 1969) with modifications by Silva Filho et al. (1978), or intothe Miaba, Simão Dias and Vaza Barris Groups (D’el-Rey Silva andMcClay, 1995; Santos et al., 1998). From our field observations,we adopt the stratigraphy suggested by D’el-Rey Silva and McClay(1995) for the Vaza Barris Domain with the following modifica-tions: (i) the former Lagarto–Palmares Formation is not includedin the Vaza Barris Domain, because its rocks are now recognizedas two separate formations (Lagarto and Palmares) of the EstânciaDomain, and there do not appear to be any stratigraphic equivalentsin the Vaza Barris Domain, (ii) rocks of the former Jacaré Formationare now included in the Frei Paulo Formation, and (iii) the SimãoDias Group is no longer a group because, after the modificationsabove, it now contains only one formation (Frei Paulo Formation).Our proposed stratigraphy is shown in Fig. 6.

At the Fazenda Capitão type locality, the lower Miaba Groupcomprises a 130–600 m-thick basal unit of quartzite with minorphyllite and conglomerate (Itabaiana Formation), overlain bypoorly sorted, up to 150 m-thick meta-conglomerate and pebblymeta-greywacke with pebbles of gneiss and quartzite (RibeirópolisFormation, ex-Jacarecica Formation of Humprey and Allard, 1969)and then by intercalated stromatolite-bearing dolomite and lime-stone (Jacoca Formation) up to 200 m thick. Basal quartzites ofthe Miaba Group rest unconformably on basement gneisses andmigmatites of the Itabaiana dome (ID in Fig. 2); in places the uncon-formity has been transposed into a thrust.

The overlying Vaza Barris Group was thrust southwards over
rocks of the Miaba Group. It starts with siltstones, phyllites,and meta-sandstones (Frei Paulo Formation) over the Ribeirópo-lis Formation or over the Jacoca Formation, succeeded upwards byphyllites and diamictites of the Palestina Formation, and then bygrey to black limestones and dolomites, occasionally with phyl-

68 E.P. Oliveira et al. / Precambrian R

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ig. 6. Stratigraphy of the Vaza Barris Domain, modified after D’el-Rey Silva andcClay (1995). Contacts between formations are tectonic or unconformities. Thick-

esses are not to scale.

ite intercalations (Olhos D’Água Formation). Jardim de Sá et al.1986) described clasts of detrital micas and embayed blue quartzithin greywackes of the Ribeirópolis Formation, which they inter-reted as meta-turbidites (“flysch”) associated with the beginningf exhumation and erosion of volcanic and metamorphic rocks inhe interior of the orogenic belt

A detrital zircon study of the Vaza Barris units (Oliveira, 2008)ndicates the following ages for the youngest zircon grains withinach clastic formation: 2000 Ma (quartzite – Itabaiana Forma-ion), 780 Ma (metagreywacke – Ribeirópolis Formation), 657 Mameta-sandstone – Frei Paulo Formation), and 653 Ma (diamictite –alestina Formation). These results support a model of sedimentaryrovenance from the São Francisco Craton for the basal Itabaianaormation, which rests upon basement gneisses, but not for thether formations. It is more likely that the sedimentary provenancef the uppermost formations of this domain was largely controlledy uplift of sources farther north, probably in other domains of theergipano Belt or in other parts of the Borborema Province.

.1.3. Macururé DomainThe Macururé Domain contains amphibolite facies, garnet-

earing meta-turbidites, feldspathic-aluminous mica schists withinor intercalations of quartzite, marble and meta-volcanic rocks,

nd lenses up to 200 m across of amphibolite, garnet–amphibolitend chlorite schist. In the northeast of this domain, a 200–300 m-hick quartzite (Santa Cruz formation) rests unconformably on theasement (Jirau do Ponciano dome – JPD in Fig. 2) and is consideredo be the base of the Macururé Domain. Gneisses and migmatites ofhis dome yield a 2000 Ma Rb–Sr isochron (Brito Neves et al., 1978).etrital zircon ages of quartzite and mica schist in the Macururé
omain indicate dominantly Mesoproterozoic (∼1000 Ma) sources
n the west, and Mesoproterozoic and Palaeoproterozoic (∼950 Mand 2100 Ma) sources in the east (Oliveira, 2008), indicating that theorborema Province was the main provenance of the Macururé sed-

ments. No zircons younger than 856 Ma were found, implying also

esearch 181 (2010) 64–84

that clast contribution was from areas older than Brasiliano/Pan-African in age.

A significant number of granites intrude the Macururé Domain.On the basis of Rb–Sr isochron ages between 623 ± 21 Ma and595 ± 10 Ma, Guimarães et al. (1997) suggested that the graniteswere emplaced by successive magmatic pulses during late stagesof the Brasiliano orogeny. Recent U–Pb age dating of these granites(Long et al., 2005; Bueno et al., 2009) constrains their emplacementbetween 628 Ma and 570 Ma. Bueno (2008) suggested that the oldergranites of this domain (ca. 628–625 Ma) formed in a continentalarc.

In the Macururé Domain minor conglomerates and greywackesof the Juá Formation (Fig. 2) have undergone minor deformationand metamorphism, but are not intruded by granites. MenezesFilho et al. (1988) interpreted these clastic sediments as an alluvialfan deposit that is possibly correlative in time with the PalmaresFormation of the Estância Domain farther south.

2.1.4. The Poco Redondo-Marancó DomainThis domain is separated from the Macururé Domain by the

major Belo Monte Jeremoabo shear zone (Fig. 2). It is divisible intotwo major sub-domains, namely Marancó and Poco Redondo.

The Poco Redondo sub-domain is a migmatitic gneiss com-plex dominated by granodioritic–tonalitic rocks that represents thebasement to the Marancó sub-domain. Santos et al. (1998) consid-ered this sub-domain to be a lithotectonic terrane, separated fromunits to the north and south by shear zones. We have studied thestructural trends of the entire Sergipano Belt with Landsat ETM+imagery, followed by systematic field investigations along threeNS-trending transects. During this survey we did not observe anyimportant shear zones separating the Poco Redondo and Marancósub-domains. Migmatitic gneisses from the Poco Redondo sub-domain have two U–Pb SHRIMP ages of 980 Ma and 961 Ma (cf.Carvalho et al., 2005).

The Marancó sub-domain comprises greenschist to amphibo-lite facies, pelitic to psammitic metasedimentary rocks, rhythmitesinterleaved with calc-alkaline andesite to dacite, intercalations ofbasalt, andesite, gabbro and serpentinites. Owing to deformation,no estimates of unit thickness are feasible. Peridotites and gabbroswith variable degrees of serpentinization mainly occur as lensesin metasedimentary rocks or as intrusions in the south of the sub-domain; they may be slices of lithospheric mantle from beneaththe orogen, or ophiolite fragments (Silva Filho, 2006). Calc-alkalinevolcanic rocks most likely belong to an Andean-type magmatic arc.Several granite bodies occur in the Marancó sub-domain, the largestof which (the Serra Negra batholith) is deformed and has a geo-chemical signature similar to that of A-type granites (Carvalho etal., 2005). The Serra Negra granite and the Poco Redondo gneissesare the basement to metasedimentary rocks of the Marancó sub-domain.

Geochronological data from the Marancó sub-domain are as fol-lows. Van Schmus et al. (1995) reported U–Pb ages of 1007 Ma onzircon grains from a meta-rhyolite and 1045 Ma from a sub-volcanicgranitic sheet. However, from a more thorough U–Pb SHRIMP study,Carvalho et al. (2005) demonstrated that the Marancó volcanicrocks are much younger (602 Ma) and contain ca. 1000 Ma inheritedzircons. Nd isotope data and whole-rock geochemistry of Carvalhoet al. (2005) (TDM ages of 1.12–1.74 Ga; εNd(t) = −1.1 and −8.62) indi-cate that the calc-alkaline meta-volcanic rocks most likely belongto a continental arc. The A-type Serra Negra batholith has a U–PbSHRIMP age of 952 Ma (Carvalho et al., 2005). Additional detri-
tal zircon SHRIMP data show that metasedimentary rocks of theMarancó sub-domain were mainly derived from a provenance withages between 980 Ma and 1100 Ma and less often from Palaeopro-terozoic and Archaean sources (Carvalho et al., 2005). The formerage group is found in gneisses and migmatites of the Cariris Velhos

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rogenic belt to the north (Brito Neves et al., 1995) and from theoco Redondo sub-domain.

.1.5. Canindé DomainThe Canindé Domain contains the following lithodemic units:

1) the Novo Gosto-Mulungu unit made up of fine-grained amphi-olites intercalated with metamorphosed pelites, siltstones, cherts,raphite schists, calc-silicate rocks and marbles, cross-cut by maficnd felsic dykes, granites and Fe–Ti-rich gabbros (Nascimento etl., 2005). (2) The Garrote unit is a continuous, up to 2 km-wideranite sheet that has intruded the Novo Gosto-Mulungu unit andas been strongly deformed with rocks of that unit. (3) The Gen-ileza unit is made up of amphibolites and diorites intercalatedith porphyritic quartz–monzonite, and minor dolerite and gab-

roic bodies. (4) The Canindé gabbroic complex comprises massivend layered olivine–gabbronorite, leucogabbro, anorthosite, troc-olite, and minor pegmatitic gabbro, norite and peridotite. Thesenits are crosscut by granites, granodiorites, and rapakivi granites.

The tectonic setting of the Canindé Domain is controversial since976, when Silva Filho (1976) interpreted the domain as an ophi-lite. Later, Jardim de Sá et al. (1986) suggested an island arc,nd Oliveira and Tarney (1990) an intracontinental magmatism.ocks of this domain have the following U–Pb ages: Garrote unit –15 Ma (Van Schmus in Santos et al., 1998); Canindé gabbroic com-lex – 701 ± 8 Ma, Gentileza quartz–monzodiorite – 688 ± 6 Ma,urralinho rapakivi granite – 684 ± 7 Ma, Boa Esperanca rapakivi-extured granite – 641 ± 5 Ma, Lajedinho granodiorite – 621 ± 9 MaNascimento et al., 2005, in preparation, and our unpublishedHRIMP data). These ages, coupled with whole-rock geochemistrynd mineral chemistry supporting a continental signature of theocks (Oliveira and Tarney, 1990), lead us to interpret the Canindéomain as a rift sequence that was later deformed and accreted

o the Poco Redondo-Marancó Domain. The rift is likely to havevolved into an ocean basin because of amphibolite occurrences inhe Novo Gosto-Mulungu unit with interleaved marble lenses andelics of pillowed basalts (Fig. 7).

.2. Structural relationships and timing of deformation phases

Our understanding of the structural evolution of the Sergipanoelt is based on a study of Landsat ETM+ imagery and on field rela-ionships along three transects indicated in Fig. 8. The correlationf deformation phases within a domain or between two domains isomplicated because it is likely that deformation was diachronouslong the orogenic belt and because deformation events in oneomain may not be recognized in another. Four deformationvents (D1–D4) affected the supracrustal rocks in the Macururénd Vaza Barris domains probably in the period 628–570 Ma,he emplacement age of syn-collisional granites (Bueno et al.,009). Deformation also reworked earlier structures in the domesnd/or inliers of basement throughout the Belt. We begin withhe deformation events in the Macururé, Vaza Barris and Estânciaedimentary domains and follow with those in the Marancó/Pocoedondo and Canindé domains and basement domes. Ar–Ar, U–Pbnd Sm–Nd age determinations are used to correlate the timing ofeformation in all domains.

.2.1. Deformation of metasedimentary rocks – Macururé, Vazaarris and Estância domains

Deformation that affected the metasedimentary rocks of theergipano Belt was heterogeneous in both style and intensity,
eveloping in a progressive sequence of four events, hereaftereferred to as D1, D2, D3, and D4.
.2.1.1. D1 event. The S1 schistosity has been strongly transposedy D2 and for this reason its structural elements are recognized only

esearch 181 (2010) 64–84 69

as cleavage in phyllites and meta-greywackes in the Vaza BarrisDomain and as schistosity in garnet–mica schists in the MacururéDomain. F1 folds may be inclined, horizontal, tight or asymmetricwith their axial plane foliation parallel or oblique to bedding S0.D1 structures are particularly well displayed in a superb outcrop atthe Gracho Cardoso dam (number 3 in Fig. 2) in the centre of theMacururé Domain. Chaotic clasts of mica schist, phyllite, graphitephyllite, meta-rhythmite and rare granites are embedded in amatrix of meta-sandstone; the whole package was subsequentlydeformed by D2 (Fig. 9). Taking account of the fact that the clastsare metamorphic (e.g. phyllites and mica schists with S1 schistos-ity, Fig. 9a) we suggest that the Gracho Cardoso rocks are remnantsof an ancient alluvial fan. This interpretation implies a significanttime gap between the D1 and D2 events during which some gran-ites were intruded into the D1-related schists. Indeed, farther northBueno et al. (2009) described a post-D1, pre-D2 tonalite (CamaráTonalite) with xenoliths of garnet mica schist; the tonalite yielda U–Pb SHRIMP zircon age of 628 ± 12 Ma. This date and that ofthe Coronel João Sá granodiorite (625 ± 2 Ma, zircon U–Pb age afterLong et al., 2005), which is intrusive into the Macururé mica schistsand which was affected by D2, set a minimum age limit for the D1event.

2.2.1.2. D2 event. The D2 event is the most penetrative in theSergipano Belt and was associated with the main phase ofcollision between the São Francisco Craton and the Pernambuco-Alagoas Block. It gave rise to pervasive south-verging thrusts andnappes throughout most of the metasedimentary domains in theorogen.

Structures associated with this event formed under differ-ent strain magnitudes from the margins to the centre of theorogen. Anchizonal sandstones of the Estância Domain containwell-preserved sedimentary structures weakly affected by open togentle, asymmetric, F2 folds (Fig. 10a). South-verging fault bendsand thrusts (Fig. 10b) confirm the south-directed shear senseof D2. In the western part of the Belt meta-carbonates of theVaza Barris Domain are thrust-stacked onto meta-siltstones of theEstância Domain. Tight to isoclinal recumbent folds and low-Tultramylonites affecting such meta-carbonates demonstrate local-ized strain partitioning during the D2 event. These ultramyloniteswere preferentially nucleated in the hanging wall of south-vergingimbricate fans (Fig. 10c) coeval with the D2 compressive shear zonethat marks the limit between the Vaza Barris and Estância domains(the Itaporanga shear zone – ISZ, Fig. 2).

Sedimentary rocks in the upper part of the Estância Domain(Lagarto Formation) contain distinctive, asymmetric tails aroundpseudo-nodules and south-verging folds, suggestive of syntectonicdeposition. Their shear sense is in agreement with the kinematicsshown in ductile deformed rocks from other domains to the north.This implies that the upper Estância sediments were deformedwhile they were still unconsolidated and partially liquefied.

The D2 deformation is most pronounced in the high-grade cen-tre of the orogen in the Macururé Domain sandwiched betweenthe Itaporanga and Belo Monte-Jeremoabo shear zones, in whichthe highest shear strain magnitudes are recorded. It may be com-parable to the foreland-verging imbricate fan of Huiqui et al. (1990),in which the largest displacements are accommodated.

The L2x lineation coeval with D2 is defined by quartz rods and

stretched feldspars. Its degree of pervasive development, how-ever, depends on rock type and heterogeneity of D2 strain. In theMacururé Domain, for example, the fine-grain size of the rocks
hinders the immediate identification of L2
x, which is therefore com-monly restricted to coarse, quartz-rich layers. On the other hand,this lineation is very pronounced in quartzites intercalated withmetasedimentary rocks of the Vaza Barris and Macururé domains,in which L2

x evolved to form L > S tectonites. The kinematics related


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Fig. 7. Field photos of amphibolites of the Novo Gosto-Mulungu unit.

o the D2 event are demonstrated by, asymmetric tails around peb-
les in meta-diamictites of the Vaza Barris Domain, asymmetricoudinage affecting quartz veins in quartzites, and recumbent folds
n quartzose mica schist (Fig. 10d) of the Macururé Domain, allndicating a dominant top-to-south sense of shear.

ig. 8. Main structural features of the Sergipano Belt. Shear zone acronyms as in Fig. 2eological Survey – CPRM (Sheets Aracajú NE and NW, and the geological map of Sergipedondo-Marancó Domain, MRD – Macururé Domain, VBD – Vaza Barris Domain, ED – Es

arble lenses in amphibolite (arrow) and (B) possible pillowed basalt.

The main structural features of the Sergipano Belt are shown
in Figs. 11 and 12. Refolded isoclines (type II fold interference pat-tern) (Fig. 12a–c) are diagnostic in the east of the Belt, where F2folds have a distinctive behaviour, and contrast with F2 styles inother regions of the Belt. In the east the F2 folds verge W-SW. A
. This map is an integration of LANDSAT ETM + images and maps of the Braziliane State). PEAL – Pernambuco-Alagoas Block, CD – Canindé Domain, PRMD – Pocotância Domain, shear zones as in Fig. 2.


Fig. 9. Field relationships of Macururé mica schists at the Gracho Cardoso dam. (A) Chaotic clasts of granite (1), phyllite (2), and meta-rhythmite (3) in a foliated sandstonematrix (4); (B) D2 foliation surface is highlighted.

Fig. 10. Field relationships in sedimentary domains. (A) Gentle to open F2 folds affecting So bedding of anchizonal meta-pelites of the Lagarto Formation, Estância Domain.(B) Fault-bends and thrust faults affecting the bedding of low-grade sandstones of the Lagarto Formation, Estância Domain. (C) South-directed thrusts in an imbricate fanaffecting meta-carbonates of the Vaza Barris Domain. Ultramylonites have nucleated at the interface between each horse. (D) F2 recumbent folds affecting the S0 bedding ofmeta-pelites from the western segment of the Macururé Domain. Note the nucleation of D2 shear zones in the attenuated folds limbs.


F tor ofc -area)(

mf

enorrtDagiflsibpatsa

2tfs

ig. 11. Map showing the main structural trends and kinematics of the western sechronological relationships and kinematics of this sector. The stereographic (equalL2

x and L3x) formed during the D2 and D3 events.

ovement from E-NE to W-SW could account for such a structuralramework.

Age constraints for D2 are provided by U–Pb dates of granitesmplaced along the S2 fabric of mica schists (Bueno et al., 2009), ourew 40Ar–39Ar ages of muscovite in quartzite and mica schist, andur new Sm–Nd isochron date of garnet mica schist in the Macu-uré Domain. Bueno et al. (2009) carried out a detailed study of theelationships between granites and deformation, and concludedhat most granites in the Macururé Domain were emplaced during2, the field evidence for which is: granite sheets were emplacedlong the axial plane foliation of small- and large-scale folds; theranite sheets commonly show Z- and S-mini-folds associated withnclined to recumbent F2 anticlines and synclines; local igneousow in granites parallel to the regional S2; and, larger plutonshow D2 foliation at their margins. Titanites (zircons are inherited)n two plutons of the eastern sector of the Belt have U–Pb agesetween 584 ± 10 Ma and 571 ± 9 Ma (Bueno et al., 2009); a twooint Sm–Nd isochron of a garnet mica schist yields a 573 ± 1 Mage of metamorphism (Fig. 13a); and, muscovites oriented alonghe D2 foliation have an 40Ar–39Ar age of 591 ± 4 Ma (Fig. 13b). Inummary, we suggest that D2 lasted at least 30 million years, frompproximately 600 Ma to 570 Ma.

.2.1.3. D3 event. The D3 event occurs in kinematic continuity withhe D2 thrust tectonics by activation of lateral displacement alongrontal thrusts ramps. Structures formed prior to this event weretrongly transposed and refolded coevally with the development

the Sergipano Belt. The block diagram in the left corner of the figure illustrates theprojection shows the attitudes of fold axes (L2

b and L3b) and stretching lineations

of steeply dipping strike-slip shear zones. A kinematic change fromdextral to sinistral, as observed respectively along the NW and NEsegments of the main regional shear zones, led to an importantpartition of strain, with the simple shear component of deforma-tion more important at the eastern and western edges of the Beltthan in its centre (Figs. 11 and 12), where a pure shear componentprevailed.

The nucleation of D3 shear zones occurred at the expense of theearly-formed structures. This is demonstrated at outcrop scale bythe development of localized shearing on the attenuated limbs of F3folds (Fig. 14a and b) that affected originally flat-lying S2 foliationthat carries a down-dip L2

x lineation at a high angle to L3x. Type II

and III fold interference patterns may occur parallel to fold axes L2b

and L3b.

Folds formed during D3 range from open to tight and vergeto the SE, S and SW, depending on their location in the north-western, central and northeastern sectors of the Belt respectively(Figs. 11 and 12). The strain increase during D3 is recognizedby the progressive tightening of F3 folds that become isoclinalin proximity to flanking shear zones, being locally transposedalong the Sm3 mylonitic foliation. In a section normal to the foli-ation and containing the L3

x lineation this kinematic pattern is
indicated by asymmetric, rotated boudins, rotated garnet porphy-roblasts, S–C and C′ structures, shear bands and syn-myloniticfolds (Fig. 14c and d). These kinematic criteria indicate dextraland sinistral movements on the northwestern and northeasternboundaries respectively of all the shear zones that bound the Estân-

rian R

cd

p

Fat


ia, Vaza Barris, Macururé, Marancó-Poco Redondo and Canindéomains.

In the western extension of the Macururé shear zone, we sam-led muscovite plates oriented along the S3 mylonitic foliation,

ig. 12. (A) Main structural trends and kinematics in the central and eastern sectors of thend kinematics of these sectors. Stereographic (equal-area) projections show the attitudehe superposition of D2 and D3 structures.

esearch 181 (2010) 64–84 73

which yield an 40Ar–39Ar age of 581 ± 2 Ma (Fig. 15). This age issomewhat older than the Sm–Nd age for the metamorphism in theeastern sector of the Belt, and probably indicates that the deforma-tion events varied across the Belt.

Sergipano Belt. (B and C) The block diagrams illustrate the chronologic relationshipss of the fold axes (L2

b and L3b) and stretching lineations (L2

x and L3x) formed during


Fig. 13. Age data from the Macururé Domain. (A) Sm–Nd isochron of the metamorphic age of garnet–mica schist FS-68 near Gararú town (longitude 709438, latitude 8898422).(B) 40Ar–39Ar age of muscovite in quartzite SBE-95 near Porto da Folha town (longitude 693888, latitude 8901524). Sm–Nd and 40Ar–39Ar data are in Tables A1 and A2respectively.

Fig. 14. (A and B) Nucleation of the S3 foliation along attenuated limbs of F3 folds that have deformed the S2 foliation of mica schists in the western Macururé Domain; (C)asymmetric boudins, S–C and C′ fabrics defining dextral shear movement in the western segment of the Macururé shear zone; (D) asymmetric trails of boudins showingsinistral shear sense in the eastern segment of the Macururé Shear Zone. Kinematic criterion defined by a quartz vein within marble of the Canindé Domain.

E.P. Oliveira et al. / Precambrian R

F8o

aBSiBd

Fp

ig. 15. 40Ar–39Ar age of syn-D3 muscovite SBE-122 (longitude 493265, latitude980900) from a mylonitic quartzite south of Macururé town, in the western sectorf the Macururé Domain. 40Ar–39Ar data in Table A2.

The kinematic incompatibility of the D3 structures results inn important partition of strain in the centre of the Sergipano
elt, especially along the centres of the Belo Monte Jeremoabo,ão Miguel do Aleixo and Itaporanga shear zones, where theres a prominent component of shortening perpendicular to theelt. This relationship has caused a localized kinematic ambiguity,emonstrated by the coexistence of sinistral and dextral kinematic
ig. 16. Main deformation features of migmatites in the Marancó/Poco Redondo Domainlanes and vertical axes. (C) Syn-D1 conformable apophysis of the Queimada Grande gran

esearch 181 (2010) 64–84 75

indicators, combined with the development of down-dip, late-D3L3

x lineations that crosscut all previous stretching lineations. In theinnermost part of the Belo Monte Jeremoabo shear zone this phe-nomenon is readily recognized by the coexistence of syn-myloniticfolds and kinks with vertical fold axes that show both sinistral anddextral shear sense. Similar structures are also seen along othershear zones of the Belt, where they mimic the major structuralframework. These structures were probably associated with thelater stages of collision between the Pernambuco-Alagoas Blockand the São Francisco Craton.

Comparing the magnitudes of strain of the D2 and D3 eventsacross the northern and southern segments of the Belt it is certainthat D2 fabrics are better developed in the south than in the northwhere D3 strike-slip tectonics prevail. Such a contrast illustratesimportant strain partitioning across the Belt that can, in part, beattributed to the rheological contrast between the sedimentary-dominated domains in the south and the more magmatic domainsin the north. Such a difference of behaviour can explain the forma-tion of the Belo Monte-Jeremoabo shear zone as a terrane boundarydeveloped during accretion of the Poco Redondo-Marancó andCanindé domains to the northernmost wedge of the SergipanoBelt.

2.2.1.4. D4 event. This event marks the end of Neoproterozoicdeformation in the Sergipano orogenic belt. Continued shear-
ing during uplift and cooling of the belt either developed newductile–brittle to brittle structures or reactivated the D2 and D3ductile fabrics. The main D4 structures are kink folds, shear andextension fractures, faults and en echelon tension gashes, all show-ing a shear sense that is compatible with that indicated by the
. (A) Fn−1 fold transposed along Sn foliation. (B) Isoclinal Fn folds with steep Sn axialite. (D) Earlier structures (Fn−2) preserved in mafic enclaves in migmatites.

7 rian Research 181 (2010) 64–84

diDd

2

tatobee

(tfotfooedaDa2

isb(

ircpmawSdstrlDestJakDBf

itbmwDi

6 E.P. Oliveira et al. / Precamb

uctile fabrics. In the Estância Domain several strike-slip faultsndicate southward displacement of the whole sedimentary pile.

4 is also prominent in the Poco Redondo-Marancó and Canindéomains and will be described in the corresponding sections.

.2.2. Deformation in the Poco Redondo/Marancó domainThis domain comprises a late Mesoproterozoic/early Neopro-

erozoic basement (migmatites and gneisses), a supracrustal covernd igneous bodies. Because the timing of deformation and migma-ization in the basement is not yet well constrained, the sequencef structural events is numbered with the youngest recorded in theasement rocks as Dn. Hence, all structures developed prior to thisvent will be referred to in alphanumeric indexes, such as Dn, Dn−1,tc.

This domain preserves relicts of a complex deformation historyDn−1) that was coeval with a period of anatexis that generatedhe migmatitic gneisses of the Poco Redondo region. Fn isoclinalolds subsequently affected the migmatitic banding Sn−1 duringverprinting of the Dn structures (Fig. 16a) that were variablyransposed and refolded by younger structures. The axial planar Sn

oliation mostly dips steeply and trends E-W (Fig. 16b). The timingf this event can be constrained by the syntectonic emplacementf the Queimada Grande granite, which shows flow structures (ori-nted mafic enclaves), pre-terminal crystallization features (ductileeformed feldspar, but weakly deformed or undeformed quartz)nd granodiorite apophyses parallel to the migmatite bandingn (Fig. 16c). This granite has a U–Pb age of 624 Ma (Brito etl., 2006) and a continental arc geochemical signature (Bueno,008).

Structures older than Dn−1 occur within amphibolitic xenolithsn migmatites of the Poco Redondo/Marancó domain. These aremall, gentle to open, asymmetric Fn−2 folds in a differentiatedanding Sn−3, that is truncated by the Sn foliation of the migmatitesFig. 16d).

Investigating deformation in metasedimentary and meta-gneous rocks of the Marancó sub-domain, Carvalho (2005)ecorded two ductile deformation events Dn+1 and Dn+2, that suc-eeded the Dn event observed in the migmatites. Dn+1 developed aenetrative, NW-trending axial plane foliation marked by orientedicas, garnet and sillimanite in aluminous schists and quartzites,

nd by amphibole in meta-basalts; the Serra Negra batholithas partially converted into augen gneiss. This event developed

SW-verging, asymmetric folds associated with shallow to steeplyipping, SW-directed oblique thrusts; in the northern part of theub-domain the fold vergence is opposite, possibly a result of back-hrusting. Dn+2 is a continuum of Dn+1. Fn+1 folds were coaxiallyefolded and transposed along left-lateral, strike-slip shear zonesinked to further displacements of Dn+1 thrust sheets. Apparently,

n+2 did not significantly deform felsic volcanic rocks in the south-rnmost part of this domain, suggesting that the volcanics areyn- to late Dn+2. A third deformation event affected this domain,hough its effects were restricted to areas close to the Belo Monte-eremoabo shear zone that delimits the Poco Redondo-Marancónd Macururé domains to the south. Small-scale chevron folds andink bands are the main structures associated with Dn+3. A fourthn+4 event, correlative with D4 in the sedimentary domains of theelt, is distinguished by a set of left-lateral NE-trending strike-slip

aults.Geochronological constraints for Dn+1 come from 40Ar–39Ar dat-

ng of amphiboles extracted from a meta-basalt close to a Dn+1hrust shear zone. Three 40Ar–39Ar plateau steps yielded a com-
ined age of 625 ± 3 Ma (Fig. 17a). Muscovite plates from a garnetica schist give a younger 40Ar–39Ar age of 612 ± 7 Ma (Fig. 17b),hich we ascribe to exhumation of the Poco Redondo-Marancóomain during Dn+2 that may have lasted until at least ca. 603 Ma,
.e. the U–Pb SHRIMP age of andesite and dacite (Carvalho, 2005),

Fig. 17. 40Ar–39Ar age of (A) Dn+1 amphibolite SBE-38A (longitude 602073, latitude8913274) and (B) garnet muscovite-schist SBE-33M (longitude 626936, latitude8907792) of the Marancó sub-domain, Poco Redodo-Marancó domain. 40Ar–39Ardata in Table A2.

if we take into account the fact that the felsic volcanic rocks wereweakly deformed during Dn+2.

2.2.3. Deformation in the Canindé DomainThe Canindé Domain is separated from the Poco Redondo-

Maranco Domain by the Mulungu-Alto Bonito shear zone (cf. Seixasand Moraes, 2000), which is the eastern extension of the Macururéshear zone in the centre of the Sergipano Belt.

Deformation in this domain was similar to that in supracrustalrocks of the Poco Redondo-Marancó Domain, and is well preservedin metasedimentary rocks and amphibolites of the Novo Gosto unitthat were affected by two ductile deformation phases, D2 and D3.Because the Canindé gabbroic complex entrains deformed amphi-bolites from an unknown source, we refer to this early deformationevent as Dn. D1 is commonly transposed by D2, but is recognizedin metasedimentary rocks by minor folds parallel or oblique to S0(Fig. 18a). Increase in deformation intensity produced a metamor-phic banding S1 that is usually folded by D2 structures (Fig. 18b). D2,the main deformation event in the Canindé Domain, can be moreaccurately described by two progressive deformation increments.The first is characterized by open to tight folds, sometimes asso-

x
ciated with N-NW-dipping, low angle thrusts and a L2 lineationthat mostly dips NNW. In the second increment of D2, the S2 folia-tion (higher angle dip to the N) evolved to a near-upright myloniticfoliation as the Mulungu-Alto Bonito shear zone is approached;associated upright-to-inclined, tight folds verge south with an axial


o Gost

pdc

osaosstc

m((smtfaNgeN(Ustiiits

2

Rtaprr

nw

Fig. 18. Field relationships in metasedimentary rocks of the Mulungú-Nov

lane foliation that dips NE. During D2 metre-thick sheets of pinkeformed leucogranite were emplaced parallel to S2; they are syn-ollisional/accretion crustal melt granites.

A third D3 event, correlative with D4 in the sedimentary domainsf the Belt, is distinguished by NE- and NW-trending conjugatehear fractures and by a set of NE-trending faults; the latter showdominant sinistral shear sense and offset the mylonite fabric S2mf the Mulungu-Alto Bonito shear zone. The orientation of bothets of structures enabled us to estimate a maximum compres-ion �1, oriented N-NE, which is compatible with the indentation ofhe Pernambuco-Alagoas massif southwards into the São Franciscoraton.

We suggest the following constraints for the timing of defor-ation in the Canindé Domain: (a) the Canindé gabbroic complex

701 ± 8 Ma) and the Gentileza porphyritic quartz–monzodiorite688 ± 6 Ma) are not as intensively deformed as the Canindéupracrustal rocks; they behaved more competently during defor-ation and were affected by D1 and D2 close to their contact with

he Mulungu-Novo Gosto unit and by the D3-related faults – there-ore D1 and D2 are younger than the ages referred to above; (b)mphiboles from D1-, D2-deformed amphibolite of the Mulungu-ovo Gosto unit have an 40Ar–39Ar age of 636 ± 7 Ma; the Lajedinhoranodiorite (cf. Seixas and Moraes, 2000) entrains elongate maficnclaves that parallel S1–S2 of the host Gentileza amphibolite –ascimento (in preparation) dated this granodiorite at 621 ± 9.5 Ma

U–Pb SHRIMP); (c) the Curituba monzogranite (617 ± 7 Ma, zircon–Pb – Silva Filho et al., 2005) crosscuts the Mulungu-Alto Bonito

hear zone and thus sets an upper age limit for D2. No age informa-ion is available for D3. However, given that D3 correlates with Dn+4n the Poco Redondo-Marancó Domain and with D4 in the metased-mentary domains, we suggest it might be younger than 581 ± 2 Ma,.e. the 40Ar–39Ar age of muscovite plates (Fig. 15) oriented alonghe D3 mylonitic foliation in the western extension of the Macururéhear zone in the Macururé Domain.

.2.4. Pre-Brasiliano deformation in basement domesCorrelation between deformation events observed in the Poco

edondo/Marancó domain and those in the two basement domeso the south is difficult, because they are distant and have differentges (Archaean palaeosome in the basement domes vs. early Neo-roterozoic in the Poco Redondo domain). The deformation events
ecorded in rocks from the Simão Dias and Itabaiana domes areeferred to as D′
n, D′1, S′

n and S′1.

In the gneiss domes a S′n banding was affected by tight to isocli-

al F′1 folds, and developed an E-W-trending gneissic foliation S′

1ith a steep dip to the north. The parallelism between S′

n and S′1

o unit of the Canindé Domain showing D1 affecting S0 (A) and D2 folds (B).

supports the interpretation that S′n was originally sub-horizontal,

and that its current position was caused by overprinting of theNeoproterozoic events (D2–D3). The intense recrystallization ofplagioclase and hornblende along the S′

1 foliation demonstratesthat the D′

1 event developed under amphibolite facies condi-tions. A SHRIMP U–Pb age of 2868 ± 25 Ma was obtained onzircons from a grey gneiss palaeosome of the Simão Dias dome(Oliveira, 2008). However, the significance of this age is open tointerpretation, because no zircon grains have U/Th ratios lowerthan 0.2, thus favouring a high-grade metamorphic or protolithage.

2.3. Geochemistry of igneous rocks and tectonic setting

The geochemistry of igneous rocks of the Poco Redondo-Marancó and Canindé domains is important in order to understandthe pre-collision history of the orogenic belt. We focus firstly on thegeochemistry of the migmatitic paleosome (980–960 Ma), the SerraNegra batholith (952 Ma), and the andesite–dacite (ca. 603 Ma) ofthe Poco Redondo-Marancó Domain, and secondly on the Gar-rote unit granite (ca. 715 Ma), the Gentileza unit rapakivi granite(684 Ma), the Boa Esperanca granite (ca. 641 Ma) and the Lajed-inho granodiorite (621 Ma) of the Canindé Domain. Representativechemical analyses of these rocks are in Table A3.

The migmatitic paleosome samples from the Poco Redondo-Marancó Domain have a major element calc-alkaline to calcicsignature and trace element contents similar to those of volcanicarc granites (Fig. 19a and b). These geochemical characteristics,combined with the slightly negative to positive εNd values of twosamples (εNd(960 Ma) = 0.87 and −1.64; Table A3), suggest that theigneous protoliths could have originated in an Early Neoproterozoiccontinental arc.

The Serra Negra batholith has anorogenic geochemical charac-teristics (Fig. 19c and d). We interpret it as a granitic batholith thatformed at 952 Ma in an Early Neoproterozoic rift (initial breakup ofRodinia?).

The swarm of dacite–andesite sills in slates and phyllites of theMarancó sub-domain have a dominant calc-alkaline to alkali-calcicmajor element signature, which is similar to that of volcanic-arcmagmas (Fig. 19e and f); εNd(T) values are negative, mostly inthe range −7.4 to −1.3 (Table A3). We suggest these rocks were
intruded in a 603 Ma continental arc.
Geochemical data of granitic rocks from the Canindé Domainare shown in Fig. 20. The Garrote granite is an elongate sheet inter-calated with amphibolites in the Novo Gosto-Mulungu unit. Thisassociation raises the possibility of rift-related bimodal magma-


F arana t et alG

tspcOs

etiRgtpoosao

ig. 19. Geochemical diagrams for deformed igneous rocks of the Poco Redondo-Mnd F) Intermediate to felsic volcanic/subvolcanic rocks. Fields in A and E after Froseochemical data in Table A3.

ism. Indeed, our geochemical results (Fig. 20) indicate markedimilarities between the Garrote granite and anorogenic within-late granites. This geochemical signature combined with theontinental characteristics of the associated amphibolites (cf.liveira and Tarney, 1990) strongly supports a rift-related tectonic

etting.The Curralinho (684 Ma) and Boa Esperanca (641 Ma) granites,

specially the former, exhibit rapakivi textures. Although the tec-onic settings of rapakivi granites are debatable, their occurrencen extended continental crust is well established (e.g. Calzia andämo, 2005). In Fig. 20c and d, samples of the Curralinho rapakiviranite fall in the field of A-type and within-plate granites, whereashose of the Boa Esperanca granite straddle the fields of within-late and volcanic-arc granites as well as the fields of A-type and
ther granitic types (Fig. 20b–d). Because the Curralinho graniteccurs associated with mingled mafic (amphibolite) and more fel-ic (porphyritic quartz–monzodiorite) rocks of the Gentileza unitnd the mafic rocks of this unit have a geochemical signaturef continental flood basalts (Oliveira and Tarney, 1990) we sug-
có Domain. (A and B) Migmatite palaeosome; (C and D) Serra Negra batholith; (E. (2001), in C after Whalen et al. (1987), and in B, D and F after Pearce et al. (1984).

gest the Curralinho rapakivi granite was emplaced in a continentalrift.

On the other hand, the genesis of the Boa Esperanca graniteremains open to debate. It contains sporadic rapakivi textures andat least in part is geochemically similar to A-type granites else-where; thus it could have originated in an extensional setting. Itis much younger than the Curralinho granite. If we accept that the641 Ma Boa Esperanca rapakivi granite formed in a rift, then exten-sion of the continental crust in the Canindé area must have lastedat least 70 million years, because the Garrote granite was emplacedat ca. 715 Ma.

Finally, the Lajedinho granodiorite (621 Ma) is one of theyoungest granitic rocks in the Canindé Domain. It was probablyemplaced during or shortly after D1 because the elongate mafic
enclaves it entrains (igneous flow structure) are parallel to S1//S2in the host Gentileza amphibolite. This granodiorite has a major ele-ment alkali-calcic signature (Fig. 20a) and in a Pearce et al. (1984)diagram samples fall on the boundary between within-plate gran-ites and arc granites. We suggest it was emplaced in a continental


F aftera le of

ac

3

pgpttaDdaBsect

3

wfcoEttDPs

ig. 20. Geochemical diagrams for granitic rocks of the Canindé Domain. Fields in And in D after Pearce et al. (1984). Data for the Boa Esperanca Granite and one samp

rc, with significant geochemical inheritance from previously riftedrust.

. Discussion

The time relationships between the deformation phases cou-led with the interpretation of our new geochronological andeochemical data reveal that the crustal framework of the Sergi-ano orogenic belt was the result of successive accretion eventshat involved a complex interaction between the São Francisco Cra-on, the Pernambuco-Alagoas Block, and allochthonous terranesnd gneissic blocks during three main deformation episodes (D1,2 and D3), all developed in the time span of 650–540 Ma. Theseeformation events are recognized in the Poco Redondo-Marancónd Canindé domains, and in supracrustal sequences of the Vazaarris and Macururé domains, and less clearly in weakly deformededimentary rocks of the Estância Domain, and in basement rocksxposed in the Itabaiana and Simão Dias domes. These domes alsoontain a record of earlier deformation events that were extensivelyransposed by the Neoproterozoic deformation.

.1. Geotectonic model

We propose that the evolution of the Sergipano Belt beganith the breakup of a Palaeoproterozoic continent (Fig. 21a)

ollowed by development of a Mesoproterozoic (∼980–960 Ma)ontinental arc (Poco Redondo gneisses) possibly on the marginf the Palaeoproterozoic Pernambuco-Alagoas Block (Fig. 21b).xtension of this continental block (Fig. 21c and d) gave rise
o (i) the Serra Negra A-type granites and associated sedimen-ary rocks on the stretched margin of the Poco Redondo-Marancóomain, (ii) between the Pernambuco-Alagoas Block and theoco Redondo/Marancó domain the Canindé volcanic-sedimentaryequence, (iii) and a passive margin on the southern edge of the
Frost et al. (2001), in B and C after Whalen et al. (1987) and Calzia and Rämo (2005),the Lajedinho Granite from Nascimento (2005). See text for discussion.

Pernambuco-Alagoas Block (basal quartzites of the Santa Cruz for-mation, in the Macururé Domain). A second passive margin formedon the São Francisco Craton (basal clastic unit of the Vaza BarrisDomain – Itabaiana Formation). The absence of any ophiolitic rockssuggests that ocean floor basalts, which we presume separated thetwo opposing passive margins, were removed by subduction thatwas necessary for the generation of a continental magmatic arclater between 630 Ma and 620 Ma.

Deposition of sediments on the passive margin of thePernambuco-Alagoas Block began after ca. 900 Ma, i.e. the age ofthe youngest detrital zircons in sedimentary rocks of the Macu-ruré Domain and the Marancó sub-domain. In the Canindé Domainsedimentation probably started at about 715 Ma (U–Pb age of theA-type Garrote granite) and continued to at least 625 Ma – theage of the youngest detrital zircons in the Novo Gosto-Mulunguunit. Deposition of the Juetê and Itabaiana Formations on the SãoFrancisco Craton passive margin could have started any time after1975 Ma (age of youngest zircons in the Itabaiana Formation).

In the Canindé Domain, rifting continued until approximately640 Ma (Fig. 21d) with emplacement of the bimodal igneous associ-ation of the Garrote A-type granite (715 Ma) and continental maficvolcanic rocks of the Novo Gosto-Mulungu unit, emplacement ofthe continental-type Canindé gabbroic complex (ca. 700 Ma), ofthe Gentileza microgabbros and quartz–monzodiorite (688 Ma)and rapakivi granite (684 Ma), and of the rapakivi-textured BoaEsperanca granite (641 Ma). There is no conclusive evidence foropening of an incipient ocean floor in the Canindé Domain, althougha few pillow-bearing amphibolites of the Novo Gosto-Mulungu unitresemble ocean-floor basalts (Fig. 7).

Convergence of the Pernambuco-Alagoas Block and the SãoFrancisco Craton led to deformation in shelf sediments, buildup of a continental arc between 630 Ma and 620 Ma (Fig. 21e)in the Macururé, Poco Redondo-Marancó and Canindé domains(621 Ma Lajedinho granite in the Canindé Domain, 628–625 Ma

8 rian R

gRtg

Fb


ranites in the Macururé Domain, and 624 Ma granite in the Pocoedondo-Marancó Domain), slab-tearing (?) and emplacement ofhe Curituba monozogranite–syenite at 617 Ma, and syn-collisionalranite emplacement in the Macururé (590–570 Ma), Canindé and

ig. 21. Proposed tectonic evolution of the Sergipano Belt from the Mesoproterozoic (cay their acronyms – MSZ (Marancó Shear Zones), BMJSZ (Belo Monte/Jeremoabo Shear Zo

esearch 181 (2010) 64–84

Poco Redondo-Marancó domains (Fig. 21e and f). We infer thata small oceanic plate was subducted beneath the Poco Redondo-Marancó Domain to explain the occurrence of 603 Ma-old, arcvolcanic rocks in the Marancó sub-domain (Fig. 21f). Subsequent

. 1000 Ma) to the Neoproterozoic (ca. 570 Ma). The main shear zones are indicatedne), SMASZ (São Miguel do Aleixo Shear Zone), ISZ (Itaporanga Shear Zone).


Table A1Sm and Nd isotopic data of garnet mica schist from the Macururé Domain.

Nd (pp

0.67341.956

etc6sAmc

3

awjMto9stow8caMctStwgpbfgsuzncidet

TA

Sample Rock Type Sm (ppm)

FS 68 grt Garnet 0.357FS 68 wr Whole-rock 9.143

xhumation and erosion of the Pernambuco-Alagoas Block andhe latter three domains led to deposition of the uppermostlastic sediments in the Estância and Vaza Barris domains with15–570 Ma-old detrital zircon grains, and deposition of the Juáediments (piggy-back basin?) in the Macururé Domain (Fig. 21f).t this time the supracrustal rocks were thrust onto the continentalargin of the São Francisco Craton in the south. The final domain

onfiguration of the Belt is shown in Fig. 21g.

.2. Regional implications

The above tectonic evolution has several implications for themalgamation and breakup of the supercontinents Rodinia andestern Gondwana. Accordingly, the occurrence of 980–960 Ma

uvenile granodiorite (migmatitic gneisses) in the Poco Redondo-arancó Domain suggests closure of a late Mesoproterozoic ocean

o form a continental magmatic arc, possibly related to late stagesf assembly of the supercontinent Rodinia between 1000 Ma and00 Ma (Li et al., 2008). The Canindé rift (715–680 Ma) and shelfediments on both passive margins of the São Francisco Cra-on and Poco Redondo-Marancó Domain may be linked to thenset of breakup in this part of Rodinia, although elsewhereidespread continental rifting of Rodinia occurred between ca.

25 Ma and 740 Ma (Li et al., 2008). Convergence of the São Fran-isco Craton (plate) and the Borborema Province possibly startedt about 630 Ma with emplacement of arc-type granites in theacururé, Canindé and Poco Redondo-Marancó domains, and it

ontinued until ca. 590–570 Ma with intrusion of leucogranites inhe Macururé Domain during the main collisional event (D2) in theergipano Belt (Bueno et al., 2009). Post-assembly extrusion tec-onics affected most of the Borborema Province as indicated byidespread occurrence of large-scale strike-slip shear zones and

ranite emplacement; some of the shear zones have their counter-arts in Africa (Fig. 1). According to Bueno et al. (2009), correlationetween syn-D2 granites in the Sergipano Belt and coeval granitesarther north in the Borborema Province indicates that, whereasranites were emplaced in the Sergipano Belt under compres-ion, in the northern Borborema Province granites were emplacednder extensional conditions related to regional strike-slip shearones. These contrasting emplacement settings for contempora-eous Neoproterozoic granitic rocks are most likely explained by a
ombination of continent–continent collision and extrusion tecton-cs. Finally, its diverse petrotectonic assemblages correlated with aetailed structural history and its well-documented long-lastingvolution make Sergipano a key orogenic belt for understandinghe Neoproterozoic construction of western Gondwana.
able A2r isotopic data of muscovite and amphibole from shear zones in the Sergipano Belt.

Sample Lab# Laser (W) 40/39 38/39 37/39

SBE-38A amphibole 1914-01A 0.2 107.43460 0.01376 0.1371914-01B 0.3 137.49220 0.01458 0.1171914-01C 0.5 136.01470 0.01214 0.0541914-01D 0.6 133.07670 0.01078 0.1961914-01E 0.8 130.97080 0.00136 0.0001914-01F 1.2 133.89580 0.00920 0.1471914-01G 3.2 130.57470 0.01833 1.6121914-02A 0.2 122.66960 0.01085 0.0001914-02B 0.3 136.12750 0.01087 0.000

m) 147Sm/144Nd 143Nd/144Nd ±1�

0.3204 0.51305 60.1317 0.51234 5

Acknowledgments

The authors thank FAPESP for research grants to EPO andMNCA (2002/03085-2, 2002/07536-9 and 2002/02368-0) and atravel grant to BFW (1997/12387-2). EPO is greatly indebted toCNPq for research grants (302703/2002-0, 301025/2005-3 and302590/2008-0). Discussions with Adejardo Silva Filho from theFederal University of Recife greatly improved our understanding ofthe geology of the Pernambuco-Alagoas Block. We benefited fromthe positive comments of two referees. This paper is dedicated tothe memory of Marinho Alves da Silva Filho who spent most of hisprofessional life in understanding the geology of the Sergipano Belt.

Appendix A. Analytical techniques

In addition to field relationships and Landsat ETM+ imageryobservations, in this paper we include new 40Ar/39Ar age dating,a Sm–Nd isochron and whole-rock geochemistry.

40Ar/39Ar geochronology was carried out on mineral sepa-rates (muscovite and hornblende) from regional shear zones. Theselected samples were pulverised on an agate mill, washed withdistilled water to remove rock flour and kept in ultrasonic bath for1 h. After drying, the minerals were separated on a Franz magneticseparator, followed by hand picking under a binocular microscope.Forty to fifty micrograms of each mineral concentrate were used,from which 25–30 grains were selected along with grains of the28.02 Ma Fish Canyon sanidine standard. Each sample was kept inaluminium foil, vacuum sealed in a silica tube and left for irradia-tion for 14 h at the Institute of Energy and Nuclear Research (IPEN),University of São Paulo (Brazil). The Ar isotope data acquisition andage calculations were done at the Geosciences Institute, Universityof São Paulo, and followed the general procedures of Vasconceloset al. (2002). Only 40Ar/39Ar probability density plots were used toshow plateaux ages. The results are shown in Table A1.

Sm–Nd isotope data (Table A2) were acquired on whole-rockand garnet concentrates from a garnet mica schist following thegeneral procedures of cation exchange resins of Patchett and Ruiz(1987) and Gioia and Pimentel (2000). Sm and Nd were analyzedby thermal ionization mass spectrometry at the isotope laboratoryof the University of Brasilia (Brazil).

Whole-rock major and trace element analyses of selected gran-
ites were obtained by X-ray fluorescence spectrometry at thegeochemistry laboratory of the University of Campinas (Brazil),respectively on fusion beads and pressed powder pellets, followingthe procedures of Vendemiatto and Enzweiler (2001). Representa-tive chemical analyses are shown in Table A3.
36/39 40*/39 %Rad Ar40 (mol) Age (Ma) ± (Ma)

84 0.00479 106.03910 98.7 2.14E−14 504.00 4.2869 0.00352 136.47050 99.2 3.46E−14 625.98 2.4919 0.00125 135.65360 99.7 5.48E−14 622.81 2.1040 0.00056 132.94300 99.9 3.07E−14 612.25 2.2400 −0.00330 131.94350 100.7 7.50E−15 608.35 15.6481 0.00384 132.78450 99.2 4.07E−15 611.64 8.1153 0.01325 126.91840 97.1 8.58E−15 588.57 6.6100 0.00021 122.60660 99.9 2.78E−14 571.43 2.7500 0.00058 135.95560 99.9 5.17E−14 623.98 2.42


Table A2 (Continued)

Sample Lab# Laser (W) 40/39 38/39 37/39 36/39 40*/39 %Rad Ar40 (mol) Age (Ma) ± (Ma)

1914-02C 0.4 135.33060 0.01191 0.00000 −0.00022 135.39560 100.0 4.59E−14 621.81 2.511914-02D 0.5 132.65710 0.01364 0.27685 0.00276 131.88640 99.4 2.85E−14 608.12 2.681914-02E 0.6 134.01350 0.00952 0.28359 −0.00029 134.14420 100.1 1.66E−14 616.94 3.421914-02F 1.2 133.84560 0.01005 0.49766 0.00182 133.38930 99.6 1.74E−14 614.00 4.081914-02G 1.8 134.07390 0.04498 0.00000 0.00357 133.02250 99.2 3.93E−15 612.57 11.781914-02H 3.2 118.82370 −0.13305 0.00000 −0.12759 156.51040 131.7 4.65E−16 702.02 53.141914-03A 0.2 130.50070 0.00506 0.00000 −0.00352 131.53840 100.8 1.58E−14 606.76 3.201914-03B 0.3 137.22420 0.01141 0.00000 −0.00067 137.42030 100.1 4.45E−14 629.66 2.231914-03C 0.4 136.87790 0.01106 0.00000 −0.00021 136.94070 100.0 3.94E−14 627.80 2.361914-03D 0.5 135.48780 0.01373 0.00000 0.00175 134.97000 99.6 2.50E−14 620.15 2.801914-03E 0.6 134.55210 0.01402 0.20403 0.00222 133.93030 99.5 1.86E−14 616.11 3.571914-03F 1.2 131.46440 0.01301 0.79741 0.00225 130.93080 99.5 2.65E−14 604.38 2.221914-03G 3.2 126.18270 0.02049 1.48275 0.00772 124.13720 98.3 5.93E−15 577.53 7.99

SBE-95 muscovite 1905-01A 0.3 129.23420 0.01040 0.00000 −0.00044 129.36260 100.1 4.82E−14 598.22 1.801905-01B 0.5 126.61740 0.01008 0.00974 −0.00007 126.64030 100.0 2.27E−14 587.47 3.071905-01C 0.6 127.67570 −0.00984 0.00000 −0.00603 129.45330 101.4 1.32E−15 598.58 33.141905-01D 0.8 134.50080 −0.02660 0.00000 −0.03238 144.06550 107.1 1.62E−15 655.18 21.091905-01E 1.4 75.32806 −0.00238 0.03300 −0.00053 75.48640 100.2 2.15E−15 372.64 7.251905-01F 3.2 62.33438 0.01205 0.00000 0.01570 57.69541 92.6 1.74E−14 291.49 1.351905-02A 0.2 128.74780 0.00925 0.16897 0.00282 127.94180 99.4 1.18E−14 592.62 3.831905-02B 0.3 126.36270 0.01380 0.15101 0.00281 125.55660 99.4 3.00E−14 583.18 2.721905-02C 0.4 127.62780 0.01108 0.03495 0.00247 126.90230 99.4 1.80E−14 588.51 3.321905-02D 0.8 126.90490 0.01249 0.04050 0.00262 126.13780 99.4 2.59E−14 585.48 2.961905-02E 1.6 116.64190 0.03020 1.30520 0.00813 114.44150 98.0 1.92E−15 538.51 13.331905-02F 3.2 125.71480 0.01613 0.57763 0.00418 124.57250 99.1 6.43E−15 579.27 6.241905-03A 0.2 127.89700 0.01151 0.00000 0.00423 126.64500 99.0 1.30E−14 587.49 3.761905-03B 0.3 128.12670 0.01207 0.00000 0.00009 128.09820 100.0 2.80E−14 593.23 4.521905-03C 0.4 126.55930 0.01156 0.00000 −0.00187 127.11250 100.4 1.83E−14 589.34 3.301905-03D 0.8 127.11220 0.01013 0.00000 −0.00248 127.84370 100.6 1.69E−14 592.23 3.081905-03E 1.6 128.25900 0.00266 0.00000 −0.01210 131.83330 102.8 4.37E−15 607.92 9.831905-03F 3.2 126.43700 0.02129 0.00000 0.01622 121.64540 96.2 9.68E−16 567.59 21.50

SBE-33M muscovite 1908-01A 0.2 117.54300 0.05132 4.41466 0.05908 100.72370 85.4 1.08E−15 481.83 19.201908-01B 0.3 132.76010 0.01075 0.00000 0.00194 132.18700 99.6 1.33E−14 609.30 4.501908-01C 0.4 133.25640 0.01119 0.05573 0.00041 133.14260 99.9 2.20E−14 613.03 3.361908-01D 0.5 136.03340 0.01917 1.26481 −0.00324 137.20350 100.8 1.96E−15 628.82 15.941908-01E 0.6 132.79420 0.01258 2.04412 0.01146 129.74130 97.6 1.46E−15 599.71 31.341908-01F 0.9 135.57700 −0.00219 0.19423 −0.01165 139.05040 102.5 3.44E−15 635.95 9.721908-01G 1.4 131.51480 −0.00654 0.00000 −0.01987 137.38360 104.5 3.82E−15 629.51 9.671908-01H 3.2 −75.67517 1.12480 20.01728 0.86026 – 433.7 4.90E−17 0.00 –1908-02A 0.2 127.41230 0.00776 0.00000 0.02339 120.49850 94.6 8.75E−16 562.99 26.061908-02B 0.3 132.48870 0.01126 0.00000 0.00061 132.30800 99.9 2.04E−14 609.77 2.831908-02C 0.3 130.35210 0.01783 0.55974 0.00494 128.98260 98.9 6.12E−15 596.72 6.271908-02D 0.4 129.10870 0.00013 0.00000 −0.01484 133.49350 103.4 3.48E−15 614.40 10.301908-02E 0.8 133.74000 0.01334 0.66829 0.00245 133.12720 99.5 5.16E−15 612.97 8.051908-02F 1.4 135.87720 0.01150 0.00000 −0.01706 140.91940 103.7 3.36E−15 643.14 10.241908-02G 3.2 134.08570 −0.03087 0.00000 −0.03437 144.23750 107.6 2.30E−15 655.83 12.401908-03A 0.2 131.99940 0.00296 0.00000 −0.01117 135.29930 102.5 5.62E−15 621.43 9.011908-03B 0.3 132.05160 0.00793 0.00000 −0.00080 132.28700 100.2 2.13E−14 609.69 2.961908-03C 0.3 133.66210 0.00098 0.00000 −0.00678 135.66260 101.5 3.44E−15 622.84 11.321908-03D 0.4 134.46640 −0.01688 0.00000 −0.00112 134.79380 100.2 9.20E−16 619.47 28.281908-03E 0.8 133.45240 −0.00287 0.00000 −0.00707 135.53810 101.6 2.59E−15 622.36 13.681908-03F 1.4 135.51230 0.01364 1.10080 −0.00124 136.06180 100.3 2.30E−15 624.39 16.411908-03G 3.2 131.54990 0.01779 1.36174 0.00833 129.31180 98.2 4.65E−15 598.02 8.63

SBE-122 muscovite 1912-01A 0.2 104.59890 0.01471 0.00000 0.00688 102.56450 98.1 9.41E−15 489.54 3.521912-01B 0.2 119.65330 0.01042 0.10958 0.00225 119.00600 99.5 1.49E−14 556.99 3.571912-01C 0.3 126.02760 0.01161 0.00000 0.00103 125.72130 99.8 4.32E−14 583.83 1.961912-01D 0.3 125.22710 0.01464 0.57192 0.00286 124.47410 99.4 3.09E−14 578.87 1.981912-01E 0.4 123.64390 0.01175 0.14795 0.00099 123.37500 99.8 1.85E−14 574.50 3.151912-01F 0.4 125.37020 0.01170 0.00000 0.00065 125.17820 99.8 3.50E−14 581.67 2.151912-01G 0.6 124.49140 0.01416 0.00000 0.00174 123.97630 99.6 1.95E−14 576.89 4.441912-01H 0.8 121.79790 0.02051 0.00000 0.01104 118.53490 97.3 5.30E−15 555.09 7.231912-02A 0.2 114.00830 0.02146 2.26463 0.01089 111.13390 97.3 8.97E−15 525.01 4.261912-02B 0.2 125.95050 0.01594 1.17663 0.00514 124.61970 98.9 2.26E−14 579.45 3.151912-02C 0.3 125.00940 0.01379 0.42811 0.00045 124.94450 99.9 2.78E−14 580.74 2.171912-02D 0.3 125.31220 0.01432 1.37348 0.00292 124.66860 99.4 1.91E−14 579.65 2.621912-02E 0.4 125.89910 0.01265 0.43009 0.00085 125.71570 99.8 4.42E−14 583.81 2.161912-02F 0.5 125.01670 0.01336 2.58297 0.00531 123.85930 98.9 1.14E−14 576.43 3.331912-02G 0.7 122.45100 0.01566 0.00000 −0.00336 123.44360 100.8 3.25E−15 574.77 9.231912-03A 0.2 105.28910 0.01113 0.00000 −0.00013 105.32630 100.0 8.18E−15 501.04 3.741912-03B 0.2 120.79140 0.01201 0.00000 −0.00215 121.42620 100.5 1.77E−14 566.71 3.221912-03C 0.3 125.13840 0.01087 0.00000 −0.00162 125.61520 100.4 3.21E−14 583.41 2.371912-03D 0.3 124.47320 0.01291 0.00000 −0.00034 124.57410 100.1 2.71E−14 579.27 2.101912-03E 0.4 124.14690 0.01150 0.00000 −0.00052 124.30070 100.1 3.88E−14 578.18 1.871912-03F 0.5 125.14920 0.01288 0.00000 −0.00186 125.70000 100.4 2.50E−14 583.74 2.491912-03G 0.7 121.94530 0.00510 0.00000 −0.01213 125.52830 102.9 5.63E−15 583.06 6.66

E.P.Oliveira

etal./Precam

brianR

esearch181 (2010) 64–84

83

Table A3Representative chemical analyses of igneous rocks from the Poco Redondo-Marancó and Canindé domains.

Poco Redondo-Marancó domain Canindé domain

MC-128B MMC-90B FS-181A MMC 11 MMC 41 MMC 199 MMC 315 MMC 317 FS-141-C FS-173 CRN-279 CRN-254b CRN-109A FS-168 JS-18A JS-05Apaleosome paleosome paleosome andesite andesite dacite S.Negra S.Negra Garrote Garrote B.Esperanca B.Esperanca Lajedinho Lajedinho Curralinho Curralinho

SiO2 59.11 71.01 72.27 54.77 61.93 70.3 71.33 68.85 77.32 63.15 72.14 66.3 71.43 58.39 63.15 57.10TiO2 1.15 0.314 0.504 0.939 0.789 0.624 0.363 0.226 0.071 0.938 0.246 0.663 0.121 1.086 0.887 1.557Al2O3 20.27 15.82 13.17 14.8 15.45 13.42 14.15 16.33 12.27 16.44 14.58 15.03 14.03 17.27 14.26 16.17Fe2O3 8.33 2.22 4.2 8.19 7.93 4.81 3.2 2.36 0.61 3.72 1.48 3.87 1.87 7.26 5.53 8.52MnO 0.05 0.047 0.133 0.17 0.102 0.059 0.043 0.027 0.131 0.118 0.019 0.068 0.08 0.118 0.106 0.147MgO 0.83 1.03 1.07 4.13 4.63 2.3 0.41 0.95 0.03 1.04 0.41 1.11 1.1 2.33 2.34 1.98CaO 0.55 3.61 3.03 5.78 0.8 0.28 1.79 0.63 0.39 1.64 1.26 2.18 1.18 4.97 4.44 4.12Na2O 0.97 4.62 3.44 3.14 3.39 3.69 2.67 6.11 3.29 5.78 4.09 3.91 3.91 4.14 3.92 4.15K2O 4.61 1.11 1.32 1.32 1.74 1.57 5.55 3 5.39 5.37 5.25 5.22 5.21 2.92 2.35 3.74P2O5 0.406 0.098 0.11 0.245 0.175 0.141 0.14 0.046 0.016 0.349 0.108 0.31 0.33 0.398 0.194 0.399L.O.I. 3.22 0.38 0.41 7.4 3 2 0.4 1.1 0.22 0.55 0.56 1 0.23 0.52 2.15 1.41Total 99.5 100.2 99.7 100.1 100 99.2 100 99.6 99.7 99.1 100.14 99.66 99.49 99.40 99.33 99.29

Ba 1393 169 504 393 468 339 878 125 14 1133 838 1585 1862 1547 573 1009Ce 118 28 54 57 22 25 122 133 25 185 87 122 142 115 78 127Cr 88 12 16 115 101 78 20 11 25 14 18 17 55 21 65 24Cu 31 8 12 11 51 28 8 6 3 5 5 10 15 14 20 20Ga 25 19 18 18 22 13 20 24 26 25 27 27 24 24 18 25La 59 23 23 27 12 17 56 61 25 112 50 64 68 48 32 55Nb 23 11 15 13 10 6 16 23 85 46 7 33 17 18 21 37Nd 59 <8 29 34 12 10 57 42 12 63 39 58 54 45 39 72Ni 47 12 13 8 74 50 2 6 22 3 6 54 31 32 14Pb 28 14 13 23 6 3 27 31 56 18 53 30 20 16 13 17Rb 202 61 78 53 48 46 193 239 641 117 178 179 79 81 41 48Sn 5 <3 3 7 5 6 3 8 9 10 4 3 4Sr 126 310 126 312 64 118 119 29 11 299 345 474 599 510 211 224Th 22 12 7 9 8 4 16 35 12 12 10 16 24 7 2 3U 2 11 2 3 4 2 3 6 49 3 4 7 3 1 <2 <2V 127 28 53 197 169 99 19 10 <3 30 18 51 82 102 89 134Y 53 8 45 29 31 23 23 72 29 45 4 42 38 42 46 71Zn 64 44 78 103 129 75 51 51 15 70 43 49 78 94 86 121Zr 250 127 226 164 138 122 246 172 46 603 159 563 553 382 310 566εNd(T) 0.87 −1.64 −6.54 −1.80 −2.47 1.68 0.02

8 rian R

R

A

B

B

B

B

B

B

B

B

C

C

C

C

C

C

D

D

D

D

F

G

G

H

H

J

L

L


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