Accepted Manuscript

From extension to shortening: dating the onset of the Brasiliano Orogeny in easternBorborema Province (NE Brazil)

Sérgio P. Neves, Olivier Bruguier, José Maurício Rangel da Silva, Gorki Mariano,Adejardo F. da Silva Filho, Cristiane M.L. Teixeira

PII: S0895-9811(14)00068-6

DOI: 10.1016/j.jsames.2014.06.004

Reference: SAMES 1280

To appear in: Journal of South American Earth Sciences

Received Date: 20 February 2014

Revised Date: 7 June 2014

Accepted Date: 9 June 2014

Please cite this article as: Neves, S.P., Bruguier, O., da Silva, J.M.R., Mariano, G., da Silva Filho, A.F.,Teixeira, C.M.L., From extension to shortening: dating the onset of the Brasiliano Orogeny in easternBorborema Province (NE Brazil), Journal of South American Earth Sciences (2014), doi: 10.1016/j.jsames.2014.06.004.

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ACCEPTED MANUSCRIPTFirst report of a late Tonian (869 Ma) intrusion in the Borborema Province

The maximum deposition age of supracrustal sequences in the Pernambuco-Alagoas Domain is

younger than 650 Ma

Orthogneisses with geochemical intraplate affinity suggest extensional conditions until 646-

636 Ma

Change of extensional to contractional deformation, marking the beginning of the Brasiliano

Orogeny, bracketed between ca. 640 and 630 Ma

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ACCEPTED MANUSCRIPTFrom extension to shortening: dating the onset of the Brasiliano Orogeny in

eastern Borborema Province (NE Brazil)

Sérgio P. Neves1, Olivier Bruguier2, José Maurício Rangel da Silva1, Gorki Mariano1,

Adejardo F. da Silva Filho1, Cristiane M. L. Teixeira3

1 Departamento de Geologia, Universidade Federal de Pernambuco, 50740-530,

Recife, Brazil

2 Géoscience Montpellier, Université de Montpellier II, Montpellier, France

3Pós-graduação em Geociências, Universidade Federal de Pernambuco, 50740-530,

Recife, Brazil

Abstract

In pre-drift reconstructions, the central and southern parts of the Borborema

Province, northeastern Brazil, belong to a large Brasiliano-Pan-African orogenic realm

situated to the north of the São Francisco-Congo Craton. In order to better understand

the timing and geodynamic setting under which this orogenic system developed, a

structural, geochemical and geochronological study was conducted across the east

Pernambuco shear zone (EPSZ) system, which separates the Pernambuco-Alagoas

Domain (PEAL) from the Central Domain. A sample of the Pinhões orthogneiss (GE-

1), in the Central Domain, one sample of a syenitic orthogneiss (CA-34) wrapped by the

EPSZ, and one sample of orthogneiss named Altinho (CA-40), in the northern portion

of the PEAL, were dated by LA-ICP-MS. . The Pinhões orthogneiss yielded an age of

869 ± 9 Ma, interpreted as the emplacement age of the protolith during a late Tonian

magmatic episode. Samples CA-40 and CA-34 yielded 206Pb/238U weighted mean ages

of 652 ± 6 Ma and 636 ± 3 Ma, respectively, which are interpreted as dating

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that these rocks were formed during the same magmatic event in view of the identical

ages of 646 ± 13 Ma and 646 ± 11 Ma, respectively, given by the less precise upper

intercept of the discordia lines. The metaluminous and magnesian nature of the Altinho

orthogneiss is akin to the calc-alkalic suite. However, some samples plot in the

intraplate field in tectonic discrimination diagrams and the Nd TDM model age of 1.36

Ga is unlike that of juvenile magmas in convergent settings. The Altinho orthogneiss is

quite similar in terms of trace elements geochemistry to the syenitic orthogneiss, which

has a clearer intraplate affinity, and the dated samples have identical initial Sr isotope

ratios (0.7047). Therefore, emplacement in an extensional setting is preferred over a

convergent one. Two samples of paragneisses (SB-1 and BB-9) from the PEAL were

also dated. The ages of the youngest zircon grains in sample BB-9 (655 to 642 Ma)

overlap the crystallization age of the Altinho orthogneiss, implying that sedimentation is

younger than or, at best, synchronous with magmatism. The age of low Th/U grains in

samples CA-34 (615 ± 8 Ma) and SB-1 (587 ± 12 Ma) are related to a subsequent

metamorphic overprint, which is loosely constrained between 580-620 Ma. These

observations, combined with evidence provided by previous studies, suggest that the

change from an extensional to a contracional setting occurred at ca. 640-630 Ma. In

contrast with most collisional orogens, where a long period of oceanic subduction

precedes collision, the inferred tectonic evolution suggests that the Brasiliano Orogeny

resulted from inversion of continental and/or proto oceanic rifts.

Keywords: Brasiliano-Pan-African Orogeny; LA-ICP-MS; geochemistry; provenance

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ACCEPTED MANUSCRIPT1. Introduction

Since the pioneering work of Kennedy (1964), it has been increasingly

recognized that large areas in Africa and South America were the loci of orogenic

activity during the Neoproterozoic. Generally known as the Pan-African (Kennedy,

1964; Black and Liégeois, 1993) or Brasiliano (Almeida et al., 1981; Brito Neves and

Cordani, 1991) Orogeny, the age of this thermal and tectonic event has been loosely

defined as spanning the period of 700-500 Ma. However, in some areas, a much longer

duration has been proposed: e.g., 900-550 Ma in the Brasília Belt of Central Brazil

(Valeriano et al., 2004; Pimentel et al., 2011) and the Pharusian belt of Hoggar (Caby,

2003); 800-580 Ma in the Gourma belt of Mali (Berger et al., 2011); and 800-550 Ma in

the Arabian-Nubian Shield (Johnson et al., 2011). In other areas, the main period of

orogenic activity occurred well within the Paleozoic (540-480 Ma), as is the case for the

Búzios Orogeny in SE Brazil (Schmidt et al., 2004) and in the West Congo belt of NW

Angola (Monié et al., 2012). It seems to be appropriate to continue with the use of

Brasiliano/Pan-African designation to encompass all orogenic events of

Neoproterozoic/early Paleozoic age that occurred in Africa and South America.

However, in order to understand the assembly of the Gondwana supercontinent it is

essential to characterize the tectonic setting and the precise onset and duration of

orogenic events in geographically separated regions. Acquisition of structural and age

data along with geochemical characterization of pre- to early-orogenic rocks should

make it possible to distinguish relative contributions of crustal reworking and juvenile

crustal addition in these belts and thus to discuss their accretionary, collisional or

intracontinental nature.

After its final stage of growth, Gondwanaland consisted of several

Brasiliano/Pan-African orogenic belts encircling older cratonic nuclei (Fig. 1a). The

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Gondwana (Fig. 1a). As such, unravelling its tectonic history is crucial to place better

constraints on the build-up of this paleocontinent. The geographic location of the BP is

to the north of the São Francisco Craton and it is covered by the Phanerozoic Parnaíba

Basin in the west (Fig. 1b). Although there is a consensus that Brasiliano deformation

and metamorphism were caused by convergence of the São Francisco/Congo,

Amazonian and West African cratons, there is continuing debate whether these cratons

were previously separated by large oceans (e.g., Santos et al., 2008; Oliveira et al.,

2010; Araújo et al., 2013) or, instead, if the orogeny was mainly intracontinental

(Neves, 2003, 2011; Neves et al., 2009). Furthermore, the onset of the Brasiliano

Orogeny is not well-characterized and it is not clear if deformation was synchronous or

diachronous in the different domains of the BP. In this paper, we tackle these issues by

studying supracrustal rocks and Neoproterozoic orthogneisses that crop out in its eastern

portion (Fig. 1c). The main focus is in the Pernambuco-Alagoas Domain, for which

available data are scarcer than in the Central Domain and in the Sergipano Belt, to the

north and south, respectively (Fig. 1b). Zircon U-Pb ages, whole-rock major and trace

elements and Sr and Nd isotopic compositions are reported and discussed aiming to

provide constraints on the ages of deposition and metamorphism of supracrustal rocks,

on the ages of emplacement and metamorphism and on the petrogenesis of the

orthogneisses, and on the geodynamic processes in the area.

2. Geological setting and previous studies

2.1.Regional geology and geochronology

The central and southern parts of the Borborema Province comprise several

metamorphosed belts of supracrustal rocks, orthogneiss units and voluminous plutonic

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dioritic to granitic compositions constitute most of the exposed basement (Brito Neves

et al., 2000; Neves et al., 2006; Van Schmus et al., 1995, 2011; Neves et al., this issue,

and references cited in these works). Most orthogneiss occurrences in the Pernambuco-

Alagoas Domain are as yet undated but the few available zircon ages (Silva et al., 2002;

Neves et al., 2004) and Nd isotope data (Da Silva Filho et al., 2002, 2007) require large

parts of this domain to be also of middle Paleoproterozoic age. Late Paleoproterozoic to

Mesoproterozoic (1.7-1.5 Ga) orthogneisses, metagabbros and meta-anorthosites are

locally important (Pessoa et al. 1978; Van Schmus et al. 1995; Sá et al., 2002; Accioly

et al., 2000; Miranda, 2010). Mesoproterozoic orthogneisses younger than 1.5 Ga are

conspicuously lacking.

The early Tonian is represented by an ENE-trending belt of metavolcanic rocks

and augen gneisses in the median portion of the Central Domain (Fig. 1c). The event

responsible for formation of these rock assemblages was called Cariris Velhos (Brito

Neves et al., 1995). Metavolcanic rocks in the Cariris Velhos belt are bimodal (but

largely dominated by the felsic component) and gave U-Pb zircon ages mainly of 1000-

960 Ma whereas augen gneisses yielded ages as young as 920 Ma (Van Schmus et al.,

1995, 2011; Santos et al., 2010; Guimarães et al., 2012). Similar ages were also found in

a belt of metavolcanic rocks east of the Cariris Velhos belt (Accioly et al., 2010) and in

one augen gneiss of the Pernambuco-Alagoas Domain (Brito et al., 2008). The Cariris

Velhos event is also documented by migmatitic gneisses and a large augen gneiss body

in the northwestern part of the Sergipano Belt (Poço Redondo subdomain and Serra

Negra “granite”; Fig. 1c). Paleosome of two migmatitic gneiss samples of the Poço

Redondo subdomain gave ages of 980 Ma and 961 Ma and a sample of the Serra Negra

“granite” an age of 951 Ma (Carvalho, 2005; Oliveira et al., 2010).

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ACCEPTED MANUSCRIPTIt is expected that the Cariris Velhos event also included deposition of

sedimentary sequences. In fact, Van Schmus et al. (2011) found no detrital zircon

younger than 930 Ma in a sample of metasedimentary rock considered coeval with the

metavolcanics. However, the more extensive work of Guimarães et al. (2012) showed

the presence of a significant fraction of young zircons in other metasedimentary samples

credited to the Cariris Velhos event. This suggests that either early Tonian sedimentary

sequences were largely eroded or a small volume of sediments were deposited during

this period. In effect, the majority of metasedimentary samples dated so far in the

Central and Pernambuco-Alagoas domains and in the Sergipano Belt points to post-

Tonian deposition (Neves et al., 2006a, 2009; Van Schmus et al., 2011; Oliveira et al.,

2006, 2010; Guimarães et al., 2012). The youngest zircons in these belts have ages

overlapping those of metaigneous rocks of the Canindé subdomain of the Sergipano

Belt, which occurs between the Poço Redondo subdomain and the Pernambuco-Alagoas

domain (Fig. 1c). These rocks include mafic (amphibolites, metagabbros) and felsic

representatives (rapakivi-textured metagranites) and have ages ranging from 690 to 640

Ma (Nascimento, 2005; Oliveira et al., 2010). The Canindé subdomain is interpreted as

an inverted continental rift based on the bimodal nature of the magmatism, and on the

affinity of the granitic and gabbroic rocks with, respectively, A-type granites and

continental flood basalts (Oliveira and Tarney, 1990; Nascimento, 2005; Oliveira et al.,

2010), which is consistent with concomitant extensional conditions favoring sediment

deposition.

2.2.Study area

The study area straddles the boundary between the Central and Pernambuco-

Alagoas domains, which is defined by the East Pernambuco shear zone (EPSZ) system

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dominated by micaschists and pelitic to psamitic pagneisses, and numerous Brasiliano

plutons. Most orthogneissic complexes are middle Paleoproterozoic, with ages

comprised between 2.16 and 1.97 Ga (Sá et al., 2002; Neves et al., 2004, 2006b; Brito

Neves et al., 2013; Neves et al., this issue). Exceptions are 1.7-1.5 Ga-old augen

gneisses and metagabbroic-anorthositic complexes (Accioly et al., 2000; Sá et al.,

2002).

Previous studies (Neves and Vauchez, 1995; Neves and Mariano, 1999; Neves et

al., 2000, 2004) have shown that the EPSZ consists of several branches comprising

high-temperature (HT) and low-temperature (LT) dextral mylonitic belts. The HT

mylonites are characterized by stability of hornblende, recrystallization of feldspars,

abundant myrmekite, and grain boundary migration recrystallization of quartz in

granitic protoliths. They are mainly confined to the southern border of the large

Caruaru-Arcoverde batholith (CAB in Fig. 2) and connected with synchronous HT,

intra-batholithic sinistral mylonitic zones, indicating that their development post-dated

emplacement. The U-Pb and Pb-Pb ages of the Caruaru-Arcoverde batholith (591-587

Ma; Guimarães et al., 2004; Neves et al., 2004) thus place an upper age limit on the

beginning of shear zone development. The LT mylonites present microstructural

features and mineral assemblages typical of rocks deformed under greenschist facies

conditions, including retrogression of hornblende to actinolite, titanite and epidote,

ductile and brittle behavior of feldspars, and subgrain rotation and bulging

recrystallization of quartz. Their protoliths are mainly granitic rocks of plutons younger

than the Caruaru-Arcoverde batholith (Neves et al., 2008), but also include dike

swarms, orthogneisses and metasedimentary rocks. Dextral and sinistral shear zones

with similar orientations to those associated with the Caruaru-Arcoverde batholith are

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comparable deformation regime in the Central and Pernambuco-Alagoas domains

during development of the transcurrent shear zones.

The steep mylonitic foliation related to the transcurrent shear zones clearly

cross-cuts a previous shallowly to moderately dipping regional foliation present in

orthogneisses and metasedimentary rocks (Neves et al., 2000, 2006a). Neves et al.

(2005, 2006b, 2012) showed that stretching lineations in these two groups of rocks have

distinct orientations. Although there is considerable dispersion due to later folding

and/or wrench shearing, lineations dominantly plunge gently to the northeast or

southwest in orthogneisses and east-southeast or west-northwest in metasedimentary

rocks (Fig. 2). In the latter, several kinematic criteria indicate top-to-the-WNW tectonic

transport (Neves et al., 2005). In contrast, kinematic indicators are rarely seen in

orthogneisses, suggesting predominantly coaxial deformation. Where present, they

indicate top-to-the-northeast displacement. These differences in kinematic behavior

were interpreted as resulting from vertical strain partitioning (Neves et al., 2005; 2006b,

2012). The mass transport direction towards WNW in metasedimentary rocks was

attributed to thrusting, whereas the underlying orthogneisses would have flowed in the

NE direction in order to compensate the resultant crustal thickening.

U-Pb dating of metamorphic zircons, zircon overgrowths, magmatic zircons in

leucosomes of paragneisses and orthogneisses, as well as lower intercept ages in

concordia diagrams, show that metamorphism associated with the development of an

early regional foliation started 632-623 Ma ago (Neves et al., 2006b, 2009, 2012).

These ages place an upper bound on the beginning of the Brasiliano Orogeny in this

area. Plutons extensively converted to orthogneisses and showing a flat-lying foliation

concordant with the country rocks yielded U-Pb crystallization ages between 618 and

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thrusting continued to at least this time.

2.3. Field relations and petrography of the studied metasedimentary rocks

Detrital zircons of metasedimentary rocks from samples of the northern portion

of the study area yielded a large number of Neoproterozoic ages, the youngest of which

range from 665 to 642 Ma (Neves et al., 2006a, 2009). These data are similar to those

found in other areas of the Central Domain (Van Schmus et al., 2011; Guimarães et al.,

2012) and indicate that deposition of the sedimentary material is younger than 642 Ma.

Two samples of quartzite from the Pernambuco-Alagoas Domain dated by Neves et al.

(2009) yielded predominantly detrital zircons with ages in the ranges 2.2-2.0 Ga and

1.7-1.6 Ga. The youngest zircon dated has an age of 917 Ma, which is much older than

the ages of the youngest zircons in the Central Domain. Therefore, aiming to allow an

improved comparison of the supracrustal sequences across the EPSZ system, two

samples of pelitic gneiss from the Pernambuco-Alagoas Domain were chosen for U-Pb

dating.

The first sample (BB-9) was collected from an outcrop located 8 km

northeastward of the city of Lajedo at coordinates 08º36'33.4"S and 36º16'49.8"W (Fig.

2). It is part of a monotonous sequence of pelitic gneisses intruded in the northwest side

by a syenitic pluton, dated at 587 ± 8 Ma (Neves et al., 2008), and completely

surrounded by orthogneisses on the other sides. This unit is close to the Neoproterozoic

Altinho orthogneiss described in the next section. The foliation of the rock dips 30º-50º

to 050º. The dated sample contains the assemblage garnet, biotite, plagioclase and

quartz.

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ACCEPTED MANUSCRIPTThe second sample (SB-1) is located in the southernmost part of the study area,

where stripes of metasedimentary rocks and orthogneiss alternate at map scale (Fig. 2).

The foliation in these rocks has moderate to steep dips due to proximity of an ENE-

trending dextral shear zone and the presence of normal folds with similar orientation.

Biotite gneisses dominate in the metasedimentary sequence, with frequent intercalations

of quartzite. The sample was collected at the riverbed of the Una River, at the town of

São Benedito do Sul (8º49'0.24"S, 35º55'52.47"W). At this locality, migmatization is

ubiquitous and milimetric to metric veins and dikes of leucogranite that truncates the

schistosity show continuity with the leucosome. The mesosome is a pelitic paragneiss

characterized by garnet porphyroclasts up to 1 cm in diameter.

2.4.Field relations and petrography of the studied orthogneisses

Field work conducted in the study area (Fig. 2) allowed the individualization of

a small orthogneiss unit in the Central Domain (Pinhões orthogneiss) and of a large

orthogneiss unit in the Pernambuco-Alagoas Domain (Altinho orthogneiss).

The Pinhões orthogneiss is an EW-striking elongate unit that occurs intercalated

with Paleoproterozoic banded gneisses (Fig. 3a), located in the northernmost part of the

study area (see star with label GE-1 in Fig. 2 for location). It is an equigranular,

medium-grained, grey gneiss, locally with leucocratic layers that confer an irregular

banding to the rock. In thin section, it shows a simple mineralogy consisting of quartz,

plagioclase and potassium feldspar and 5% to 10% biotite. The predominance of

plagioclase over microcline gives a granodioritic composition to the rock. The

microstructure is typically gneissic with alternating lenticular levels rich in quartz and

feldspar following the foliation defined by biotite flakes (Fig. 3b). The shape preferred

orientation of quartz, feldspars and biotite occurs through regular contacts, indicating

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occurrence of myrmekite between the contact of microcline and plagioclase crystals is

common. Garnet porphyroblasts were observed in one sample. The sample chosen for

U-Pb dating (GE-01) was collected at geographical coordinates 07º30'39.4"S and

35º50'26.2"W.

The Altinho orthogneiss was recognized as distinct from basement orthogneisses

by Mariano et al. (2007) and Da Silva Filho et al. (2007), which assumed a

Paleoproterozoic age of crystallization. The Altinho orthogneiss is a coarse-grained

augen gneiss locally displaying a layered facies (Figs. 3c and 3d). The augen gneiss is

characterized by K-feldspar porphyroclasts up to a few centimeters long. The banded

facies is medium-grained, equigranular and consists of alternate layers enriched in mafic

(biotite and/or amphibole) and felsic (quartz and feldspars) minerals. In both cases,

enclaves of amphibolite are common. In thin section, the medium-grained facies

displays two microstructural types. In the first case, the rock shows microporphyroclasts

of feldspar with irregular outlines in a fine-grained foliated matrix of quartz, plagioclase

and biotite (Fig. 3e). These features suggest that the protolith was a shallow level

intrusion containing resorbed phenocrysts. The other microstructural type has a typical

gneissic fabric consisting of semi-continuous biotite and/or amphibole layers and

granoblastic quartz-feldspar layers (Fig. 3f). This microstructure is similar to the one

observed in the augen gneiss, except for the presence of porphyroclasts in the latter. One

sample from the equigranular facies (CA-40) collected in a road cut of highway BR-104

(geographical coordinates 08º25'14.7"S, 35º57'50.3"W) was chosen for U-Pb dating

(Fig.2).

In addition to the above mapped units, a porphyroclast-rich, pinkish green rock

in contact with an equigranular, fine-grained deep gray rock was observed inside the

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location of the outcrop is marked by the star labelled CA-34 in Fig. 2 and has

geographical coordinates 08º18'02.7"S, 35º59'22.9"W. In spite of strike-slip shearing

that promoted development of a faint subvertical foliation and a strong sub-horizontal

stretching lineation, an original flat-lying orientation is preserved (Fig. 3g). The

porphyroclast-rich band has a syenitic to quartz syenitic composition and consists of K-

feldspar megacrysts up to 1 centimeter in a medium-grained deep green matrix resulting

from retrogression of mafic minerals to a greenschist facies mineralogy comprising

titanite, epidote, actinolite, quartz and minor chlorite (Fig. 3h). The equigranular dark

band has a similar mafic mineralogy but plagioclase is the dominant feldspar, such that

the rock has a quartz dioritic to quartz monzodioritic composition. In the following,

these rocks will be referred as syenitic orthogneiss and dioritic orthogneiss,

respectively. One sample of the first (CA-34) was chosen for U-Pb dating.

2.5.Kinematics

Previous studies (Neves et al., 2005, Neves, 2012) showed that stretching

lineations in Paleoproterozoic orthogneisses dominantly plunge gently to the northeast

or southwest and that, although rare, kinematic show indicate top-to-the-northeast

displacement. The foliation in the Pinhões orthogneiss is concordant with that of the

regional Paleoproterozoic orthogneisses (Figs. 2 and 3a) and carries a southwest-

plunging stretching lineation that sometimes is better developed than the foliation (Fig.

4a). Local shear criteria suggest top-to-the-northeast tectonic transport (Fig. 4b). The

foliation in the Altinho orthogneiss is steep in many places owing to a modification by

transcurrent deformation. The original attitude has low to moderate dip and may contain

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occasional shear criteria suggest top-to-the-northeast tectonic transport (Fig. 4d).

3. Methods

U-Pb zircon ages of the selected samples were obtained by laser ablation

inductively coupled plasma-mass spectrometry (LA-ICP-MS) at the Université de

Montpellier II, France. Zircons were separated using conventional techniques (e.g.

Bosch et al., 1996). After crushing and sieving of the powdered samples, heavy

minerals were concentrated by panning and then by heavy liquids. The heavy mineral

concentrates were subsequently processed by magnetic separation on a Frantz separator.

Zircon grains were hand-picked from the non-magnetic fraction at 1.5 A intensity and

2° side tilt. The grains were then mounted on adhesive tape, enclosed in epoxy resin

with chips of a standard material (G91500; Wiedenbeck et al., 1995), and polished to

about half of their thickness. Laser ablation was conducted using a Geolas automated

platform housing a 193 nm CompEx 102 laser from LambdaPhysik. Samples were

analyzed using an Element XR sector field, single collector ICP-MS (see Bosch et al.,

2011 for more details).

Sm-Nd and Rb-Sr data were obtained at the Geochronological Research Center

(São Paulo, Brazil) by thermal ionization mass-spectrometry (TIMS). Sr and Nd

isotopic compositions were determined according to the analytical procedures described

by Kawashita (1972) and Sato et al. (1995), using a Finnigan MAT 262 mass

spectrometry. The Sr isotopic ratios were normalized to 86Sr/88Sr = 0.1194 and replicate

analyses of 87Sr/86Sr for the NBS987 standard gave a mean value of 0.71028 ± 0.00006

(2σ); analytical blanks were less than 0.3 ng. The Nd isotopic compositions were

normalized to 146Nd/144Nd = 0.72190. The averages of 143Nd/144Nd for La Jolla and

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respectively; the blanks were 54 pg.

Chemical analyses were performed at Acme Analytical Laboratories Ltd. in

Canada. Major elements were determined using inductively coupled plasma-emission

spectrometry with a detection limit of 0.01% and precision of ±0.1%. Trace and rare

earth elements were analyzed using inductively coupled plasma-mass spectrometry

(ICP-MS) with detection limits between 0.01 and 0.5 ppm and precision of ±5%.

Diagrams displaying the geochemical variability of the studied rocks were constructed

using PetroGraph (Petrelli et al, 2005) and GCDkit (Janousek et al, 2006).

4. U-Pb geochronology

Table 1 shows the results of U-Pb analyses for the studied samples. Errors in the

table are quoted at the 1σ level, while ages and their associated errors reported in the

text below are quoted at the 2σ level.

4.1.Supracrustal rocks

Most detrital zircons from sample SB-1 (migmatized paragneiss) are slightly to

strongly discordant and broadly fall within a fan-like domain defined by discordia lines

with a lower intercept of about 590 Ma and upper intercepts of about 2000 and 2200 Ma

(Fig. 5a). The intercepts are well constrained by concordant to near-concordant analyses

at 2003 ± 36 Ma (#1-23), 2214 ± 22 Ma (#1-60) and 587 ± 12 Ma (#1-28). The latter

displays a low Th/U ratio of 0.02 (see Table 1), which is consistent with a solid state

metamorphic growth after deposition of the detritus. Other analyses with low Th/U

ratios (less than 0.1, see Table 1) are discordant (> 5%), and the distribution of the data

points within the fan-like domain is thus interpreted as resulting from lead losses during

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detrital zircons. A single analysis gave a 207Pb/206Pb age 2669 ± 14 Ma (#1-8),

suggesting a minor contribution of an Archean source. Considering only grains with

discordance < 5%, a strong peak around 2100 Ma is observed in the cumulative

probability plot (inset, Fig. 5a), which reflects the main age population in the source

area.

In contrast with sample SB-1, detrital zircons from sample BB-9 are exclusively

of Neoproterozoic to late Mesoproterozoic age. No Paleoproterozoic or Archean grains

were detected in the analyzed zircons. 52 out of the 58 analyses are concordant (Fig. 5b)

among which 29 define a large peak around 1000 Ma. Other analyses define smaller age

peaks at around 900 Ma (11 grains), 850 Ma (3 grains), 680 Ma (3 grains) and 650 Ma

(6 grains). Five grains of the last group have high Th/U ratios (ranging from 0.25 to

0.44) and detrital morphologies (analyses 2-2, 2-6, 2-25, 2-46, and 2-50), with ages

ranging from 642 ± 12 Ma to 654 ± 12 Ma. Although these grains are likely to be

derived from different source rocks, they have undistinguishable ages and have been

combined to provide a 206Pb/238U weighted mean age of 651 ± 6 Ma, which is taken as a

maximum age for deposition. In view of these results, it is unlikely that the ages of two

grains (analyses 2-1 and 2-34) with Th/U ratios of 0.08 and 0.04 and ages of 670 ± 17

Ma and 684 ± 16 Ma, respectively, which could be attributed to a metamorphic growth,

represent the minimum age of the deposition.

4.2.Orthogneisses

Twenty-seven zircons from the Pinhões orthogneiss (GE-1) were analyzed. In

the concordia diagram, the data scatter along the concordia curve with 206Pb/238U

apparent ages ranging from 774 to 900 Ma (see Table 1 and Figure 6a), thus suggesting

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an upper intercept of 869 ± 9 Ma (MSWD = 0.8), and a lower intercept close to zero (-

37±280 Ma). The upper intercept is identical to the 207Pb/206Pb weighted mean age of all

grains (870 ± 8 Ma; MSWD = 0.7) and is taken as the age of crystallization of the

protolith of the orthogneiss during the Tonian.

Thirteen zircon grains were analyzed from the Altinho orthogneiss (CA-40), but

most of them proved to contain significant amounts of common lead, probably due to

inclusions. Only seven analyses were devoid of common Pb (see Table 1). Among

these, six have consistent apparent ages and define a discordia line (MSWD = 0.9) with

an upper intercept at 646 ± 13 Ma and a near zero lower intercept (63 ± 630 Ma). The

206Pb/238U weighted mean age of the five most concordant analyses (see Fig. 6b) is

652±6 Ma. This age is taken as our best estimate for emplacement of the protolith. An

older age of 680 ± 15 Ma obtained in one grain (#4-4) is attributed to inheritance.

Zircons from the syenitic orthogneiss CA-34 (Figs. 2 and 3g-h) display a

complex distribution in the concordia diagram (see Figure 6c). Of the 21 grains

analyzed, 19 define a discordia line with an upper intercept of 646 ± 11 Ma and a near

zero lower intercept of -166 ± 330 Ma (MSWD = 0.7). Some of these grains are

discordant and, since the lower intercept is zero within errors, it is justified to calculate

a weighted mean age based on the most concordant analyses (concordance > 95%). On

this ground, the 206Pb/238U weighted mean age of 636 ± 3 Ma (MSWD = 0.3) given by

the eleven concordant analyses is taken as our best estimate for emplacement and

crystallization of the syenitic magma. One analysis from a low Th/U (0.08) grain

yielded a 206Pb/238U age of 615 ± 8 Ma, which we relate to metamorphism concomitant

with acquisition of the flat-lying gneissic fabric.

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A reconnaissance geochemical and isotopic survey of the orthogneisses was

conducted in order to place constraints on their petrogenesis. Major and trace elements

were determined for ten samples of the Altinho orthogneiss and one for the Pinhões

orthogneisses, one for the syenitic orthogneiss and one for the dioritic orthogneiss

(Table 2). Although the Altinho orthogneiss comprises an equigranular and an augen

gneiss facies, both are geochemically similar and their analyses are treated together in

the following. Nd and Sr isotope data were obtained for samples of the Pinhões and

Altinho orthogneisses and Sr isotope data for the syenitic and the dioritic orthogneisses.

The Pinhões orthogneiss is peraluminous, with aluminium saturation index

(ASI) of 1.1 (Fig. 7a), and has relatively low values of CaO (2.08 wt.%) and MgO (1.08

wt.%) (Table 2). The other orthogneisses are metaluminous or slightly peraluminous

(Fig. 7a) and relatively rich in CaO (1.9-4.4 wt.%), Fe2O3 (3-6 wt.%) and MgO (0.7-2.4

wt.%). Based on the classification of Frost et al. (2001), all samples plot in the field of

magnesian granitoids (Fig. 7b). In the modified alkali-lime index, the dioritic

orthogneiss plots in the alkalic field and the Pinhões orthogneiss at the boundary

between the latter and the alkali-calcic field; the other samples plot in the alkali-calcic

and calc-alkalic fields, except one sample of the Altinho orthogneiss that plots in the

calcic field (Fig. 7c).

The chondrite-normalized rare earth element (REE) patterns of all samples are

characterized by light REE (LREE) enrichment (Fig. 8a). The sample of the Pinhões

orthogneiss shows the highest ratio of LREE to heavy REE (HREE) (LaN/YbN = 54),

with only a discrete positive Eu-anomaly. The samples of the Altinho orthogneiss and

those of the syenitic orthogneiss and the dioritic orthogneiss are quite similar, and are

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8.6 to 17.4. The dioritic orthogneiss has the highest LREE.

The Pinhões orthogneiss is characterized by large positive anomalies of Ba, K

and Sr, negative anomalies of Ta, Nb and Ti, and low relative concentrations of Y, Yb

and Lu in primitive mantle normalized multi-element diagrams (Fig. 8b). The other

samples also have negative Nb, P and Ti anomalies but differ from typical calc-alkaline

granites by the absence of Ta and Sr negative anomalies in several samples.

The diagrams aiming at discriminate the tectonic setting yielded inconclusive

results for the study samples. In the classification of Whalen et al. (1987), they plot

either in the field of unfractionated I, S and M granites (but very close to the boundary

with the A-type field) or in the latter (Fig. 9a). In the Nb versus Y tectonic

discrimination diagram (Pearce, 1986), the samples plot near the boundary line between

the fields for arc- and collision-related granitoids and in the within plate-related

granitoids field (Fig. 9b).

Initial Sr and Nd isotopic compositions of the dated samples (Table 3) were

calculated to their respective U-Pb ages: 869 Ma for the Pinhões orthogneiss, 652 Ma

for the Altinho orthogneiss, and 636 Ma for the syenitic and dioritic orthogneiss. All

samples show relatively low Sr initial ratios (0.7040-0.7047). The Pinhões and Altinho

orthogneisses have slightly positive and negative εNd(t) values (+1.8 and -0.8,

respectively) and Mesoproterozoic Nd TDM (2-stage) model ages (1.31 Ga and 1.36 Ga,

respectively). These data indicate that the investigated granitoids have been produced by

a mixing between a juvenile component and an older, crustal, component.

6. Discussion

6.1.Supracrustal rocks: age and provenance

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constraints for the deposition of pre-orogenic sedimentary rocks in the Pernambuco-

Alagoas Domain. In a previous study (Neves et al., 2009), the youngest ages obtained in

one of two analyzed samples were 917 ± 8 Ma and 951 ± 20 Ma. Although zircons with

Tonian age predominate in sample BB-9, seven analyses of grains with high Th/U ratio

have ages comprised between 642 Ma and 684 Ma. These ages are considered to

represent the ages of the detrital zircons crystallization. The youngest analysis provides

a maximum age for deposition of 642 ± 12 Ma, which is consistent with the more

precise 651 ± 6 Ma weighted mean age of the 5 youngest concordant analyses (Fig. 5b).

These data indicate that deposition of at least part of the supracrustal sequence in the

Pernambuco-Alagoas Domain occurred in the late Neoproterozoic.

The age pattern of sample BB-9 reveals provenance of its protolith mainly from

early Neoproterozoic sources (Fig. 5b). 1000-900 Ma-old detrital zircons may have

been sourced from the Cariris Velhos belt of the Central Domain (Van Schmus et al.,

1995, 2011; Santos et al., 2010; Guimarães et al., 2012) and/or from the Poço Redondo

subdomain of the Sergipano Belt (Carvalho, 2005; Oliveira et al., 2010). The discovery

that the Pinhões orthogneiss has an age of 869 Ma opens up the possibility that at least

part of the 900-800 Ma-old zircons were derived from material eroded from a source

formed during late Tonian magmatic event(s). For zircons in the 700-640 m.y age

interval, likely sources are A-type metagranites and associated rocks present in the

Canindé subdomain of the Sergipano Belt (Nascimento, 2005; Oliveira et al., 2010).

Finally, for the youngest zircon fraction (c. 650 Ma), a source formed during the same

magmatic event responsible for intrusion of the protolith of the Altinho orthogneiss is

the most likely option. This assumption is strengthened by the close proximity of

sample BB-09 from the Altinho orthogneiss (see Fig. 2).

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two analyses yielded Paleoproterozoic ages (Fig. 5a), can have several explanations.

First, SB-1 could be part of an older sequence, and thus Neoproterozoic sources did not

exist yet during deposition. Second, the two samples could have been deposited in a

temporally evolving basin and sourced from the same geographic area, but with a

vertical layering of the crustal segment subjected to erosion. Finally, the differences

could be explained by the samples being located in small drainage systems with local

sources, such that only sources of Paleoproterozoic age were available for erosion in

case of sample SB-1 and of late Mesoproterozoic to Neoproterozoic age in case of

sample BB-9.

6.2.Orthogneisses: petrogenesis

The sample of the Pinhões orthogneiss has the highest ASI (1.1) of the studied

rocks and garnet was found in one sample. These characteristics are usually ascribed to

S-type granites. The HREE depletion (Fig. 8a) suggests that garnet was residual in the

source region of the magmas. This hypothesis is consistent with the absence of a

negative Eu anomaly, which indicates that plagioclase was not retained in the source or

fractionated during ascent, suggesting magma generation deep (> 1GPa) in the crust.

The relatively low initial 87Sr/86Sr ratio (0.7040) and the TDM of 1.3 Ga of the Pinhões

orthogneiss (Table 3) suggest that the parental magma resulted from mixing between

partial melts derived from preexisting Paleoproterozoic crust and early Neoproterozoic

juvenile mantle magmas or from partial melting of a source of intermediate composition

formed by interaction of these materials.

The syenitic orthogneiss and the dioritic orthogneiss are more alkalic than the

other samples (Fig. 7), have higher Y and Nb (Table 2; Fig. 8b), and plot either near or

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dioritic orthogneiss has not been dated, its geochemical similarity with the syenitic

orthogneiss (Figs. 7-8), almost identical initial 87Sr/86Sr ratios (0.7045 and 0.7047,

respectively; Table 3), and their occurrence together in the same outcrop suggest that

they are genetically related and thus that they were formed during the same magmatic

event. The relatively low initial 87Sr/86Sr ratios suggest derivation from the lithospheric

mantle or lower crust. The absence of inherited zircons in the syenitic sample CA-34

indicates that the temperature of 769ºC calculated by zircon saturation thermometry

(Table 2) probably underestimates the temperature of the parental magma (Miller et al.,

2003). Higher temperatures estimates of 939ºC and 944ºC were obtained from apatite

solubility in mafic rocks (Harrison and Watson, 1984) and the Al2O3/TiO2 ratio (Jung

and Pfänder, 2007), respectively (Table 2). For the dioritic orthogneiss, still higher

temperature estimates of 1042ºC and 1036ºC were obtained by these two latter methods

(Table 2). These high temperatures are consistent with a mantle origin. The negative

Eu anomaly observed in the RRE diagrams (Fig. 8a) is suggestive of plagioclase

involvement in the genesis of these rocks. If the RRE pattern resulted from retention of

plagioclase in the source, partial melting at relatively shallow depths is implied. Based

on these observations and inferences, we anticipate that the genesis of the parental

magmas of the syenitic and dioritic orthogneisses involved differentiation of magmas

produced by partial melting of enriched lithospheric mantle during extensional

deformation.

The Altinho orthogneiss has many characteristics similar to granites emplaced in

continental magmatic arcs. In common with the so-called Cordilleran granites (e.g.,

Brown, 1977; Barbarin, 1999; Frost et al., 2001), it contains biotite±amphibole and

titanite as mafic phases, encloses mafic enclaves (possibly metamorphosed dioritic

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magnesian (Fig. 7), and display negative Nb, Ta and Ti anomalies (Fig. 8b). However,

the Nb content (10-18 ppm) is higher than in typical calc-alkaline granites, and the

relatively low LREE/HREE ratios (LaN/YbN = 8-17), negative Eu-anomalies (Eu/Eu* =

0.57-0.85), and flat HREE patterns (Fig. 8a) resemble the characteristics of some A-type

granites (Jung et al., 1998; Li et al., 2003; Yuan et al., 2010). These features make some

samples plot in the within-plate field in tectonic discrimination diagrams (Fig. 9).

Considering that the samples of the Altinho orthogneiss are quite similar to that of the

syenitic orthogneiss, it is suggested similar sources and/or petrogenetic processes in

their genesis, which also favors an intraplate setting.

As it is the case of the Pinhões orthogneiss, the relatively low initial 87Sr/86Sr

ratio and the TDM Nd model age of 1.36 Ga of the Altinho orthogneiss (Table 3) indicate

that its protolith was derived from a mixed source. Given the geochemical constraints,

which require a relatively mafic source, it is proposed that two components were

involved: (a) basaltic magmas formed by decompression partial melting of the mantle in

the late Neoproterozoic and; (b) a Paleoproterozoic component, either basement rocks

or sediments derived from it. Paleoproterozoic orthogneisses in the study area have a

clear subduction zone signature (Neves and Alcantara, 2010; Neves et al., this issue),

which may have been inherited by the protolith of the Altinho orthogneiss.

6.3.From extension to shortening: onset of the Brasiliano Orogeny

The geochemical characteristics of the Altinho orthogneiss are dubious, and

could be interpreted either as indicating a convergent setting or an intraplate one,

whereas those of the syenitic and dioritic orthogneisses are more consistent with

emplacement in an extensional environment (Fig. 9). The Altinho orthogneiss and the

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and the dated samples have identical initial Sr isotope ratios (0.7047). It should also be

noted that their ages given by the upper intercept of the discordia lines are equally

identical: 646 ± 13 Ma for Altinho and 646 ± 11 Ma for the syenitic orthogneiss (Fig.

6b-c). Although our preferred interpretation for the crystallization ages are 652 ± 6 Ma

and 636 ± 3 Ma, respectively, based on the more precise 206Pb/238U weighted means of

the most concordant grains, it cannot be excluded that these rocks were formed during

the same magmatic event. Therefore, we favor intrusion of the Altinho orthogneiss in an

extensional setting. Although calc-alkaline rocks are typical of convergent margins, they

are not restricted to this setting and have been described in extensional environments as

well (Hooper et al., 1995; El Aouli et al., 2010).

The ages of the youngest zircon grains in the metasedimentary sample BB-9

(655 to 642 Ma; Table 1) overlap with the crystallization age of the Altinho orthogneiss,

implying that sedimentation is younger than or, at best, synchronous with magmatism.

This finding may also be interpreted in two ways. If intrusion of the protolith of the

Altinho orthogneiss is related to orogenic activity, this implies that the final stages of

sedimentation would have occurred in a convergent setting. The other possibility is that

sedimentation and magmatism were syn-extensional. A volcanic component is common

in supracrustal sequences deposited at convergent margins, which is not the case here,

and there is no evidence in the study area or its vicinity for suture zones or for other

features typical of a subduction setting, such as high-pressure rocks. Extension-related

magmatism is recorded between 714 and 640 Ma in the Sergipano Belt (Oliveira et al.,

2010) and a similar setting may have prevailed further north. Therefore, the second

option is considered more likely.

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widespread extension of the continental crust, starting around 690 Ma (Fig. 10a), that

succeeded previous, more localized episodes of intraplate extension. At the advanced

stages of extension, around 650 Ma (Fig. 10b), decompression allowed partial melting

of the asthenosphere and production of basaltic magmas. These magmas underplated the

thinned continental crust, where they induced partial melting and mixed with the

resultant crustal magmas to produce the source of the Altinho orthogneiss. With

continued extension, temperature conditions sufficient to melt enriched portions of the

lithospheric mantle were reached, given rise to magmas that differentiated to form the

protoliths of the syenitic and dioritic orthogneisses. It is possible that a proto-oceanic

stage was attained, but formation of a large ocean basin is unlikely.

The fact that the top-to-the-NE tectonic transport in the Pinhões and Altinho

orthogneisses (Figs. 4b and 4d) is similar to that observed in Paleoproterozoic and

Mesoproterozoic orthogneisses (Fig. 2; see also Neves et al., 2006, 2012) demonstrates

that the regional flat-lying foliation was produced during the Brasiliano Orogeny. The

age of 615 ± 8 Ma obtained in a low Th/U grain in the syenitic orthogneiss, interpreted

as the age of metamorphism, offers an estimate to the age of this event. This age is

considered to date the acquisition of the flat-lying fabric in the syenitic orthogneiss, and

not the subvertical mylonitic fabric, because the greenschist facies mineralogy of the

strike-slip-related deformation (Fig. 3h) is incompatible with the temperature conditions

required for zircon (re)crystallization, The age of 615 Ma falls within the age range of

632-606 Ma estimated for the peak of metamorphism contemporaneous with thrusting

in the Central and Pernambuco-Alagoas domains (Neves et al., 2006, 2008, 2009,

2012). It is also similar within errors to the ages of intrusion of syn-orogenic calc-

alkaline granitoids in the Pernambuco-Alagoas and Central domains (624-616 Ma;

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Sergipano Belt (628-625 Ma; Long et al., 2005; Bueno et al., 2009). It seems therefore

that in the whole eastern portion of the Borborema Province a change from an

extensional to a compressional setting took place in the 640-630 m.y. time interval (Fig.

10b-c). With the onset of convergence, it is expected that contractional deformation

localized in sites where the continental crust was the most extended or where young

oceanic crust was present, since the lithosphere is warmer and thus weaker in these

places. Maintenance of high geothermal gradients during crustal thickening allowed

attainment of pressure and temperature conditions adequate to induce partial melting

and high-grade metamorphism (Fig. 10c).

The age of 587 ± 12 Ma provided by a low Th/U grain from sample SB-1 is

similar to the age of the voluminous syn-transcurrent magmatism that intruded the study

area between 590 and 580 Ma (Guimarães et al., 2004; Neves et al., 2004, 2008, 2012).

It probably records regional heating associated with this event. This finding supports the

conclusion of previous studies (Neves et al., 2006b, 2012) that strike-slip-related

deformation post-dates development of the regional gneissic fabrics by 10-20 m.y.

6.4.Geodynamic implications

In pre-drift reconstructions, the central and southern domains of the Borborema

Province are part of a large orogenic realm to the north of the São Francisco-Congo

Craton that continues eastward in Cameroon and Central Africa Republic (Fig. 1a).

Geochronological and thermobarometric data from Cameroon point out to high-grade

metamorphism and calc-alkaline magmatism occurring synchronously with similar

events in the eastern Borborema Province (Toteu et al., 2001, 2006; Njiosseu et al.,

2005; Njiekak et al., 2008; Owona et al., 2011). These correlations strengthen earlier

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in this part of West Gondwana differs from most collisional orogens, where a long

period of oceanic subduction precedes collision. Instead, a dominantly intracontinental

model for the origin of the foldbelt is favored, with orogenesis resulting from inversion

of continental and/or proto oceanic rifts. As recently pointed out by Mohn et al. (2014),

inversion of hyper-extended continental domains may have been underestimated as a

possible mechanism capable of explaining the evolution of orogenic belts.

The forces responsible for the inferred extensional tectonics are not yet resolved.

Neves (2003) suggested that outwardly dipping subduction zones transmitted

extensional stresses to the Borborema Province, which would be located in the interior

of a large continent. Other possibility is mantle plume-activated extension. Indirect

evidence for this mechanism is provided by the continental flood basalt affinity of the

690 Ma-old Canindé Gabbroic Suite of the Sergipano Belt (Oliveira and Tarney, 1990;

Nascimento, 2005; Oliveira et al., 2006). Yet another possibility is that the Central and

Southern domains were located in an extending continental back-arc region. The

Tamboril-Santa Quitéria Complex in the northwestern part of the Borborema Province

has ages which overlap with those of the Altinho and syenitic orthogneisses and has

been interpreted by some authors as a continental magmatic arc (Fetter et al., 2003;

Santos et al., 2008; Amaral et al., 2012, Araújo et al., 2012, 2014). Assuming eastward

subduction, this would place the Rio Grande do Norte, Central and Southern domains in

a back-arc setting. However, unambiguous evidence for a long period of subduction is

still missing (Neves, 2011, this issue) and we do not favor this alternative. Clearly,

further work is needed to fully constrain the geodynamic evolution of the Borborema

Province during the Neoproterozoic.

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The results from this study provide new data that allow placing better constraints

on the Neoproterozoic tectonic evolution of the eastern Borborema Province. The age of

869 ± 9 Ma of the Pinhões orthogneiss is about 50 m.y. younger than the youngest

orthogneisses associated with the Cariris Velhos event. On the other hand, the ages of

the Altinho orthogneiss (652 ± 6 Ma) and of the syenitic orthogneiss (636 ± 3 Ma) are

older than the oldest ages obtained on metamorphic rocks and syn-orogenic Brasiliano

plutons so far described in this region, which vary from 632 to 606 Ma. Interpretation of

the geochemical characteristics of these orthogneisses in terms of tectonic environment

of intrusion is no unique but favors an extensional setting. The presence of detrital

zircons as young as 642 ± 12 Ma in the paragneiss sample BB-09 indicates syn-

extensional sedimentation until close to the age of emplacement of the syenitic

orthogneiss. Combined with evidence provided by previous studies, these observations

narrowly place the beginning of the Brasiliano orogeny in the study area within the time

interval 640-630 Ma.

Acknowledgments

This work was supported through funding from the Brazilian agencies Conselho

Nacional de Desenvolvimento Científico e Tecnológico (CNPq; grant 472582/2011-9)

and Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE;

grant APQ-0479-1.07/06). Roberto Weinberg is thanked for constructive and detailed

review that helped to improve the manuscript.

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Table 1 LA-ICP-MS U-Th-Pb results for zircons of study samples in the eastern Borborema Province

Sample Pb* Th U Th/ 208Pb/ 207Pb/ ± 207Pb/ ± 206Pb/ ± Rho Apparent ages (Ma) Conc. (ppm) (ppm) (ppm) U 206Pb 206Pb (1s) 235U (1s) 238U (1s) 206Pb/ ± 207Pb/ ± (%)

238U (1s) 206Pb (1s)

Migmatized pelitic paragneiss SB1 #1-1 57.7 30.2 189.2 0.16 0.052 0.1258 0.0006 5.435 0.089 0.313 0.005 0.96 1757 24 2040 8 86.1 #1-2 63.5 91.1 164.2 0.55 0.158 0.1306 0.0006 6.422 0.074 0.357 0.004 0.92 1966 18 2107 8 93.3 #1-3 79.4 134.3 237.1 0.57 0.187 0.1280 0.0007 5.444 0.106 0.308 0.006 0.96 1733 28 2071 9 83.7 #1-4 113.5 270.4 276.8 0.98 0.262 0.1516 0.0009 7.344 0.229 0.351 0.011 0.98 1941 51 2364 10 82.1 #1-5 94.0 111.0 263.7 0.42 0.125 0.1282 0.0005 5.941 0.066 0.336 0.003 0.92 1868 17 2073 8 90.1 #1-6 111.0 94.6 913.6 0.10 0.033 0.1127 0.0006 1.957 0.029 0.126 0.002 0.94 765 10 1843 9 41.5 #1-7 71.0 94.2 189.8 0.50 0.128 0.1299 0.0006 6.530 0.052 0.365 0.002 0.79 2004 11 2096 8 95.6 #1-8 158.6 155.2 330.3 0.47 0.122 0.1818 0.0008 10.877 0.148 0.434 0.006 0.95 2323 25 2669 7 87.0 #1-9 129.8 4.9 446.3 0.01 0.002 0.1234 0.0013 5.393 0.108 0.317 0.005 0.85 1775 26 2006 19 88.5 #1-10 89.2 56.1 342.7 0.16 0.065 0.1172 0.0017 4.094 0.136 0.253 0.008 0.90 1456 39 1914 26 76.1 #1-11 9.2 0.5 54.5 0.01 0.007 0.0997 0.0014 2.298 0.125 0.167 0.009 0.97 996 48 1619 26 61.6 #1-12 41.0 47.3 102.0 0.46 0.136 0.1339 0.0014 6.625 0.112 0.359 0.005 0.80 1976 23 2150 18 91.9 #1-13 66.7 97.8 153.9 0.64 0.181 0.1337 0.0017 6.958 0.150 0.377 0.007 0.81 2064 31 2147 22 96.1 #1-14 71.4 94.1 204.1 0.46 0.150 0.1233 0.0015 6.092 0.196 0.358 0.011 0.92 1975 50 2004 22 98.5 #1-15 82.0 108.5 247.0 0.44 0.125 0.1269 0.0011 5.423 0.097 0.310 0.005 0.88 1741 24 2055 15 84.7 #1-16 62.4 109.5 174.3 0.63 0.193 0.1302 0.0016 5.668 0.172 0.316 0.009 0.92 1769 43 2101 21 84.2 #1-17 62.2 10.8 781.6 0.01 0.004 0.0607 0.0007 0.735 0.016 0.088 0.002 0.86 543 10 630 24 86.2 #1-18 23.6 43.1 59.3 0.73 0.209 0.1267 0.0015 6.289 0.127 0.360 0.006 0.80 1982 28 2053 21 96.6 #1-19 80.6 18.1 283.4 0.06 0.022 0.1203 0.0008 4.746 0.052 0.286 0.002 0.79 1623 12 1960 12 82.8 #1-20 104.1 87.5 371.2 0.24 0.075 0.1245 0.0008 4.717 0.082 0.275 0.004 0.94 1565 22 2022 11 77.4 #1-21 127.9 3.0 453.6 0.01 0.002 0.1193 0.0008 4.770 0.051 0.290 0.002 0.78 1642 12 1945 12 84.4 #1-22 73.2 31.1 251.0 0.12 0.040 0.1230 0.0009 4.932 0.075 0.291 0.004 0.89 1646 20 2000 12 82.3 #1-23 49.0 30.0 178.0 0.17 0.089 0.1232 0.0013 6.002 0.136 0.353 0.007 0.89 1951 34 2003 18 97.4 #1-24 113.5 208.1 299.5 0.69 0.202 0.1312 0.0008 5.932 0.106 0.328 0.006 0.94 1828 27 2114 11 86.5 #1-25 81.0 5.7 305.2 0.02 0.005 0.1217 0.0008 5.037 0.093 0.300 0.005 0.93 1692 25 1981 12 85.4

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#1-26 119.9 10.3 429.0 0.02 0.010 0.1193 0.0008 4.613 0.087 0.280 0.005 0.93 1593 25 1946 12 81.9 #1-27 43.9 46.4 140.8 0.33 0.107 0.1240 0.0009 5.035 0.063 0.294 0.003 0.83 1664 15 2015 12 82.6 #1-28 52.0 10.3 596.0 0.02 0.006 0.0602 0.0004 0.790 0.010 0.095 0.001 0.85 587 6 610 14 96.1 #1-29 51.0 34.3 147.4 0.23 0.082 0.1265 0.0009 6.310 0.141 0.362 0.008 0.95 1990 36 2051 12 97.0 #1-30 22.3 19.4 62.5 0.31 0.089 0.1295 0.0012 6.770 0.168 0.379 0.009 0.92 2073 41 2091 17 99.2 #1-31 64.8 30.0 210.0 0.14 0.048 0.1243 0.0008 5.271 0.057 0.308 0.003 0.80 1729 13 2018 12 85.7 #1-32 77.2 87.0 247.4 0.35 0.124 0.1246 0.0009 5.040 0.048 0.293 0.002 0.67 1658 9 2023 12 82.0 #1-33 66.6 67.3 176.6 0.38 0.121 0.1278 0.0008 6.430 0.085 0.365 0.004 0.88 2005 20 2069 11 96.9 #1-34 135.0 133.8 430.0 0.31 0.099 0.1232 0.0008 5.205 0.109 0.306 0.006 0.95 1722 30 2004 12 86.0 #1-35 98.8 52.9 447.8 0.12 0.044 0.1176 0.0008 3.591 0.029 0.221 0.001 0.59 1290 6 1920 11 67.2 #1-36 161.3 378.5 473.9 0.80 0.240 0.1218 0.0010 4.858 0.069 0.289 0.003 0.82 1638 17 1983 15 82.6 #1-37 43.1 37.7 119.3 0.32 0.104 0.1279 0.0009 6.288 0.100 0.357 0.005 0.90 1966 24 2069 12 95.0 #1-38 38.8 30.2 124.2 0.24 0.079 0.1249 0.0011 5.229 0.076 0.304 0.004 0.80 1709 17 2028 15 84.3 #1-39 91.9 121.6 225.9 0.54 0.166 0.1296 0.0009 6.464 0.053 0.362 0.002 0.53 1991 7 2092 12 95.1 #1-40 60.9 93.9 146.6 0.64 0.197 0.1292 0.0008 6.591 0.070 0.370 0.003 0.81 2029 15 2087 11 97.2 #1-41 84.0 3.8 260.4 0.01 0.004 0.1233 0.0008 5.743 0.109 0.338 0.006 0.93 1875 29 2005 12 93.5 #1-42 73.9 100.1 189.2 0.53 0.159 0.1284 0.0008 6.378 0.131 0.360 0.007 0.95 1984 33 2076 11 95.6 #1-43 37.5 35.6 97.7 0.36 0.110 0.1309 0.0009 7.008 0.096 0.388 0.005 0.86 2115 21 2110 12 100.2 #1-44 89.6 121.0 211.3 0.57 0.164 0.1319 0.0008 6.866 0.079 0.378 0.004 0.86 2065 17 2123 10 97.2 #1-45 189.8 280.6 404.7 0.69 0.207 0.1657 0.0011 9.031 0.106 0.395 0.004 0.83 2148 18 2514 11 85.4 #1-46 92.7 93.5 266.4 0.35 0.137 0.1254 0.0009 6.478 0.120 0.375 0.006 0.93 2051 30 2035 12 100.8 #1-47 72.3 121.1 179.3 0.68 0.186 0.1325 0.0008 6.380 0.056 0.349 0.002 0.74 1931 11 2131 10 90.6 #1-48 126.8 89.5 369.9 0.24 0.071 0.1278 0.0008 5.855 0.088 0.332 0.005 0.91 1850 22 2067 11 89.5 #1-49 110.5 111.1 368.4 0.30 0.086 0.1244 0.0008 4.819 0.071 0.281 0.004 0.90 1597 19 2020 11 79.1 #1-50 74.0 28.1 288.7 0.10 0.057 0.1186 0.0007 4.186 0.078 0.256 0.005 0.94 1469 23 1936 11 75.9 #1-51 65.6 71.1 159.0 0.45 0.129 0.1304 0.0008 6.687 0.058 0.372 0.002 0.72 2038 11 2104 10 96.9 #1-52 106.9 166.3 323.7 0.51 0.170 0.1250 0.0009 5.035 0.068 0.292 0.003 0.84 1652 17 2029 13 81.4 #1-53 158.7 182.9 556.8 0.33 0.101 0.1214 0.0007 4.460 0.076 0.266 0.004 0.94 1523 22 1977 10 77.0 #1-54 74.4 111.5 178.0 0.63 0.183 0.1309 0.0008 6.653 0.048 0.369 0.002 0.59 2024 7 2109 10 95.9 #1-55 40.3 76.1 94.5 0.81 0.236 0.1346 0.0009 7.040 0.089 0.379 0.004 0.84 2073 19 2159 12 96.0 #1-56 45.1 51.8 119.6 0.43 0.131 0.1305 0.0008 6.247 0.068 0.347 0.003 0.81 1922 15 2104 11 91.3 #1-57 101.3 98.5 269.7 0.37 0.136 0.1327 0.0009 7.006 0.104 0.383 0.005 0.90 2090 24 2134 11 98.0 #1-58 93.2 129.8 244.2 0.53 0.147 0.1306 0.0008 6.057 0.039 0.336 0.001 0.42 1868 4 2107 10 88.7

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#1-59 84.3 120.9 205.9 0.59 0.170 0.1318 0.0008 6.680 0.046 0.367 0.001 0.44 2018 5 2122 11 95.1 #1-60 60.8 71.0 133.1 0.53 0.152 0.1389 0.0009 7.706 0.082 0.402 0.003 0.80 2179 16 2214 11 98.4 #1-61 75.2 115.6 196.2 0.59 0.174 0.1298 0.0008 6.071 0.077 0.339 0.004 0.89 1883 18 2095 10 89.9 #1-62 112.3 118.2 293.2 0.40 0.135 0.1261 0.0008 6.193 0.076 0.356 0.004 0.84 1964 18 2044 12 96.1 #1-63 75.9 133.1 179.6 0.74 0.225 0.1308 0.0008 6.725 0.084 0.373 0.004 0.88 2043 19 2109 10 96.9 #1-64 143.8 290.1 360.5 0.80 0.242 0.1267 0.0007 6.440 0.103 0.369 0.005 0.93 2023 26 2052 10 98.6 #1-65 87.0 95.3 251.2 0.38 0.109 0.1297 0.0008 5.733 0.078 0.320 0.004 0.89 1792 19 2094 11 85.6 #1-66 84.4 75.7 224.8 0.34 0.098 0.1283 0.0008 6.505 0.053 0.368 0.002 0.68 2019 10 2075 11 97.3 #1-67 90.8 94.4 251.1 0.38 0.109 0.1287 0.0007 6.381 0.061 0.360 0.003 0.80 1980 13 2080 10 95.2 #1-68 33.0 36.9 79.8 0.46 0.139 0.1312 0.0012 6.717 0.091 0.371 0.004 0.73 2035 17 2115 16 96.2 #1-69 0.7 0.5 6.9 0.08 0.063 0.0792 0.0038 1.102 0.060 0.101 0.003 0.47 620 15 1176 92 52.7 #1-70 85.6 135.1 257.4 0.52 0.148 0.1262 0.0010 5.084 0.060 0.292 0.003 0.73 1653 13 2045 14 80.8 #1-71 149.5 118.0 399.1 0.30 0.094 0.1315 0.0011 6.364 0.134 0.351 0.007 0.92 1940 32 2117 15 91.6 #1-72 149.7 238.2 484.4 0.49 0.151 0.1215 0.0010 4.504 0.046 0.269 0.002 0.59 1535 8 1978 15 77.6 #1-73 128.3 168.5 426.5 0.40 0.119 0.1226 0.0010 4.589 0.068 0.272 0.003 0.83 1548 17 1994 15 77.6 #1-74 104.2 122.7 263.9 0.46 0.135 0.1309 0.0011 6.642 0.064 0.368 0.002 0.49 2020 8 2110 15 95.8 #1-75 26.4 28.4 70.9 0.40 0.120 0.1310 0.0013 6.393 0.149 0.354 0.007 0.91 1953 36 2111 17 92.5 #1-76 28.9 35.3 74.2 0.48 0.147 0.1318 0.0011 6.527 0.097 0.359 0.004 0.81 1978 21 2122 15 93.2 #1-77 78.1 59.5 206.0 0.29 0.090 0.1313 0.0011 6.931 0.110 0.383 0.005 0.85 2090 24 2115 15 98.8 #1-78 91.9 95.1 248.5 0.38 0.144 0.1314 0.0015 6.820 0.253 0.377 0.013 0.95 2060 62 2116 20 97.3 #1-79 31.5 69.5 66.9 1.04 0.302 0.1308 0.0011 7.031 0.094 0.390 0.004 0.77 2123 19 2108 15 100.7 #1-80 45.4 129.7 109.6 1.18 0.380 0.1263 0.0013 5.684 0.098 0.326 0.005 0.82 1821 22 2047 17 88.9

Garnet-bearing pelitic paragneiss BB9 #2-1 46.2 34.1 442.0 0.08 0.025 0.0617 0.0003 0.932 0.014 0.109 0.001 0.93 670 9 665 12 100.7 #2-2 28.1 100.9 251.9 0.40 0.125 0.0608 0.0004 0.895 0.012 0.107 0.001 0.89 654 8 632 13 103.5 #2-3 65.6 260.8 347.2 0.75 0.229 0.0723 0.0004 1.659 0.030 0.167 0.003 0.94 993 16 993 12 100.0 #2-4 47.5 169.7 382.9 0.44 0.176 0.0703 0.0004 1.099 0.016 0.113 0.002 0.92 693 9 936 12 74.0 #2-5 20.7 144.1 94.6 1.52 0.451 0.0714 0.0006 1.632 0.031 0.166 0.003 0.89 989 15 969 17 102.0 #2-6 16.8 43.8 160.2 0.27 0.083 0.0610 0.0005 0.899 0.012 0.107 0.001 0.77 654 6 640 18 102.3 #2-7 90.7 520.2 462.2 1.13 0.344 0.0719 0.0004 1.640 0.024 0.166 0.002 0.94 988 13 982 10 100.6 #2-8 63.9 252.0 355.5 0.71 0.205 0.0721 0.0004 1.613 0.028 0.162 0.003 0.95 968 15 990 11 97.8 #2-9 80.2 365.7 414.7 0.88 0.266 0.0733 0.0006 1.735 0.025 0.172 0.002 0.81 1021 11 1023 17 99.8

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#2-10 10.7 74.3 55.0 1.35 0.412 0.0708 0.0006 1.518 0.021 0.156 0.002 0.82 932 10 951 16 98.0 #2-11 47.7 122.1 317.0 0.39 0.128 0.0704 0.0004 1.502 0.040 0.155 0.004 0.97 927 22 940 13 98.7 #2-12 59.7 224.8 330.3 0.68 0.216 0.0721 0.0004 1.623 0.029 0.163 0.003 0.94 975 15 988 12 98.7 #2-13 108.4 747.9 499.0 1.50 0.435 0.0729 0.0004 1.693 0.028 0.168 0.003 0.93 1004 14 1011 12 99.2 #2-14 8.8 39.2 49.4 0.79 0.248 0.0709 0.0007 1.545 0.029 0.158 0.002 0.83 946 14 954 21 99.2 #2-15 12.3 62.8 64.3 0.98 0.300 0.0720 0.0005 1.648 0.028 0.166 0.003 0.89 991 14 985 15 100.6 #2-16 38.1 176.8 189.4 0.93 0.286 0.0732 0.0005 1.745 0.025 0.173 0.002 0.85 1028 12 1020 15 100.8 #2-17 8.1 51.8 40.5 1.28 0.387 0.0706 0.0008 1.579 0.029 0.162 0.002 0.79 969 13 947 23 102.3 #2-18 18.3 76.5 170.1 0.45 0.145 0.0637 0.0006 0.909 0.015 0.103 0.001 0.80 635 8 732 21 86.7 #2-19 31.8 97.2 201.4 0.48 0.163 0.0691 0.0005 1.422 0.020 0.149 0.002 0.87 897 10 902 15 99.4 #2-20 24.0 236.9 116.5 2.03 0.667 0.0675 0.0005 1.307 0.022 0.140 0.002 0.89 847 12 853 16 99.3 #2-21 10.1 62.6 53.5 1.17 0.348 0.0714 0.0006 1.546 0.025 0.157 0.002 0.84 941 12 968 18 97.2 #2-22 27.8 90.9 249.0 0.37 0.116 0.0622 0.0006 0.957 0.017 0.112 0.002 0.83 682 9 680 21 100.3 #2-23 47.3 169.7 300.0 0.57 0.187 0.0696 0.0005 1.414 0.024 0.147 0.002 0.91 886 13 916 14 96.7 #2-24 10.9 46.9 64.4 0.73 0.251 0.0703 0.0005 1.519 0.033 0.157 0.003 0.95 939 18 936 14 100.3 #2-25 20.0 80.1 182.1 0.44 0.139 0.0607 0.0005 0.893 0.014 0.107 0.001 0.84 653 8 630 18 103.7 #2-26 101.1 383.9 566.2 0.68 0.200 0.0723 0.0004 1.669 0.026 0.167 0.002 0.94 998 13 996 11 100.2 #2-27 47.8 243.5 235.3 1.03 0.385 0.0719 0.0004 1.655 0.026 0.167 0.002 0.92 995 13 983 13 101.3 #2-28 33.4 253.8 164.2 1.55 0.431 0.0724 0.0006 1.585 0.020 0.159 0.002 0.77 950 9 997 17 95.4 #2-29 5.9 28.4 32.1 0.88 0.297 0.0706 0.0006 1.596 0.027 0.164 0.002 0.88 979 14 945 16 103.6 #2-30 8.9 37.4 47.8 0.78 0.256 0.0708 0.0007 1.585 0.025 0.162 0.002 0.76 969 11 952 21 101.8 #2-31 9.5 39.8 55.7 0.71 0.252 0.0706 0.0008 1.500 0.042 0.154 0.004 0.92 924 22 946 22 97.7 #2-32 8.2 41.8 42.6 0.98 0.292 0.0709 0.0008 1.592 0.027 0.163 0.002 0.74 973 11 954 23 102.0 #2-33 14.6 101.8 81.3 1.25 0.423 0.0677 0.0007 1.329 0.022 0.142 0.002 0.81 858 11 859 20 100.0 #2-34 53.3 19.2 516.8 0.04 0.011 0.0616 0.0004 0.951 0.013 0.112 0.001 0.90 684 8 660 12 103.6 #2-35 9.5 42.3 50.8 0.83 0.255 0.0697 0.0008 1.536 0.028 0.160 0.002 0.78 955 13 921 24 103.7 #2-36 11.8 75.7 61.6 1.23 0.402 0.0710 0.0006 1.490 0.023 0.152 0.002 0.84 913 11 958 17 95.3 #2-37 55.2 220.0 294.0 0.75 0.232 0.0722 0.0004 1.643 0.029 0.165 0.003 0.96 985 16 991 11 99.4 #2-38 23.6 146.5 130.0 1.13 0.354 0.0702 0.0006 1.435 0.039 0.148 0.004 0.94 891 21 935 18 95.3 #2-39 14.9 56.3 88.8 0.63 0.331 0.0681 0.0010 1.302 0.026 0.139 0.002 0.72 837 11 871 29 96.1 #2-40 21.1 118.8 100.7 1.18 0.362 0.0716 0.0005 1.644 0.024 0.167 0.002 0.85 993 11 974 15 101.9 #2-41 8.6 29.6 75.5 0.39 0.123 0.0618 0.0007 0.951 0.015 0.112 0.001 0.71 682 7 666 23 102.4 #2-42 12.3 39.2 69.8 0.56 0.186 0.0679 0.0006 1.378 0.029 0.147 0.003 0.90 886 16 864 18 102.5

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#2-43 58.9 458.0 254.4 1.80 0.529 0.0716 0.0004 1.610 0.026 0.163 0.002 0.95 974 14 974 11 100.0 #2-44 14.8 83.3 82.5 1.01 0.332 0.0716 0.0006 1.445 0.024 0.146 0.002 0.85 881 12 974 18 90.4 #2-45 27.8 108.4 233.1 0.46 0.151 0.0641 0.0009 1.014 0.022 0.115 0.002 0.74 701 11 744 31 94.2 #2-46 14.5 49.0 131.1 0.37 0.114 0.0607 0.0005 0.885 0.014 0.106 0.001 0.84 648 8 627 19 103.4 #2-47 75.1 531.9 318.4 1.67 0.530 0.0739 0.0009 1.710 0.026 0.168 0.002 0.65 1001 9 1038 23 96.4 #2-48 8.3 36.0 42.2 0.85 0.256 0.0723 0.0007 1.691 0.027 0.170 0.002 0.78 1010 12 994 20 101.7 #2-49 57.3 316.3 297.7 1.06 0.328 0.0701 0.0004 1.535 0.028 0.159 0.003 0.96 950 15 931 11 102.0 #2-50 9.4 23.1 91.0 0.25 0.077 0.0612 0.0006 0.884 0.012 0.105 0.001 0.71 642 6 648 21 99.1 #2-51 23.5 64.1 218.2 0.29 0.099 0.0631 0.0004 0.931 0.011 0.107 0.001 0.85 655 6 713 13 91.9 #2-52 84.5 742.8 504.0 1.47 0.318 0.0794 0.0006 1.516 0.032 0.138 0.003 0.93 836 15 1182 15 70.7 #2-53 80.2 330.5 423.2 0.78 0.238 0.0725 0.0004 1.670 0.022 0.167 0.002 0.93 996 11 1001 10 99.4 #2-54 25.5 112.6 132.1 0.85 0.256 0.0721 0.0005 1.671 0.021 0.168 0.002 0.82 1001 10 990 15 101.1 #2-55 110.5 533.2 594.5 0.90 0.246 0.0734 0.0003 1.667 0.030 0.165 0.003 0.97 983 16 1025 9 96.0 #2-56 48.6 268.6 266.5 1.01 0.295 0.0710 0.0004 1.558 0.024 0.159 0.002 0.93 952 13 957 12 99.4 #2-57 7.7 34.6 40.6 0.85 0.261 0.0709 0.0007 1.565 0.027 0.160 0.002 0.83 958 13 954 20 100.4 #2-58 4.7 18.3 26.7 0.68 0.235 0.0701 0.0011 1.494 0.031 0.155 0.002 0.66 927 12 930 32 99.7

Pinhoes Orthogneiss GE1 #3-1 39.0 80.0 268.1 0.30 0.110 0.0691 0.0007 1.348 0.027 0.142 0.002 0.87 854 14 901 20 94.8 #3-2 30.3 89.3 204.3 0.44 0.140 0.0685 0.0007 1.364 0.022 0.144 0.002 0.77 870 10 883 21 98.5 #3-3 41.4 129.0 259.5 0.50 0.169 0.0685 0.0006 1.397 0.018 0.148 0.001 0.72 889 8 883 18 100.7 #3-4 38.5 144.0 255.7 0.56 0.173 0.0678 0.0006 1.319 0.015 0.141 0.001 0.66 850 6 864 18 98.4 #3-5 40.4 180.9 257.9 0.70 0.216 0.0678 0.0006 1.338 0.017 0.143 0.001 0.72 863 7 861 18 100.1 #3-6 47.5 267.3 334.1 0.80 0.224 0.0672 0.0006 1.182 0.018 0.128 0.002 0.81 774 9 844 19 91.6 #3-7 40.0 128.3 274.6 0.47 0.146 0.0689 0.0007 1.311 0.017 0.138 0.001 0.68 834 7 895 20 93.2 #3-8 37.1 163.4 249.1 0.66 0.197 0.0689 0.0007 1.308 0.021 0.138 0.002 0.74 832 9 896 22 92.8 #3-9 30.4 99.4 205.1 0.48 0.152 0.0677 0.0007 1.344 0.025 0.144 0.002 0.81 868 12 859 23 101.0 #3-10 34.6 95.9 248.3 0.39 0.125 0.0685 0.0006 1.292 0.016 0.137 0.001 0.66 827 6 884 19 93.5 #3-11 168.3 657.1 1155.0 0.57 0.179 0.0682 0.0006 1.274 0.013 0.135 0.001 0.51 819 4 875 18 93.7 #3-12 46.6 137.4 321.8 0.43 0.134 0.0682 0.0007 1.307 0.017 0.139 0.001 0.63 839 6 876 20 95.8 #3-13 36.3 121.6 251.3 0.48 0.161 0.0676 0.0007 1.296 0.025 0.139 0.002 0.85 840 13 856 21 98.1 #3-14 28.4 122.6 180.4 0.68 0.209 0.0678 0.0007 1.348 0.018 0.144 0.001 0.71 868 8 863 20 100.6 #3-15 27.6 96.6 186.5 0.52 0.162 0.0669 0.0007 1.303 0.022 0.141 0.002 0.80 852 10 836 21 101.9

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#3-16 44.6 144.6 310.3 0.47 0.151 0.0690 0.0007 1.295 0.017 0.136 0.001 0.59 822 6 900 22 91.4 #3-17 33.6 202.8 220.3 0.92 0.260 0.0682 0.0007 1.252 0.017 0.133 0.001 0.69 806 7 873 20 92.3 #3-18 20.5 83.6 123.7 0.68 0.222 0.0689 0.0009 1.421 0.022 0.150 0.001 0.52 899 7 894 28 100.5 #3-19 16.2 64.2 101.1 0.63 0.189 0.0681 0.0007 1.385 0.021 0.148 0.001 0.68 887 8 871 23 101.9 #3-20 16.0 56.0 104.2 0.54 0.163 0.0681 0.0008 1.374 0.021 0.146 0.001 0.62 880 8 873 25 100.8 #3-21 15.0 53.4 102.2 0.52 0.162 0.0677 0.0008 1.290 0.018 0.138 0.001 0.52 834 6 859 25 97.1 #3-22 25.5 95.5 175.3 0.54 0.168 0.0685 0.0007 1.318 0.028 0.139 0.003 0.86 842 14 884 22 95.2 #3-23 14.1 50.5 94.0 0.54 0.163 0.0673 0.0008 1.308 0.019 0.141 0.001 0.61 851 7 846 24 100.6 #3-24 15.7 49.1 100.8 0.49 0.159 0.0667 0.0008 1.371 0.023 0.149 0.002 0.65 896 9 828 26 108.2 #3-25 17.7 73.2 116.2 0.63 0.193 0.0677 0.0009 1.315 0.024 0.141 0.002 0.69 849 10 860 27 98.7 #3-26 21.3 80.8 134.4 0.60 0.184 0.0672 0.0007 1.387 0.023 0.150 0.002 0.80 899 11 845 21 106.4 #3-27 11.0 26.3 74.2 0.35 0.106 0.0680 0.0007 1.391 0.023 0.148 0.002 0.77 892 11 869 22 102.6

Altinho orthogneiss CA40 #4-1 29.6 237.4 251.7 0.94 0.284 0.0609 0.0004 0.882 0.014 0.105 0.001 0.90 644 9 635 15 101.4 #4-2 43.1 269.9 390.0 0.69 0.211 0.0612 0.0004 0.851 0.012 0.101 0.001 0.91 619 7 647 13 95.8 #4-3 28.7 161.4 236.3 0.68 0.219 0.0612 0.0005 0.905 0.012 0.107 0.001 0.82 657 7 647 16 101.5 #4-4 18.7 115.1 146.4 0.79 0.247 0.0629 0.0005 0.966 0.014 0.111 0.001 0.84 680 8 705 16 96.5 #4-5 39.8 67.4 387.7 0.17 0.053 0.0612 0.0004 0.896 0.012 0.106 0.001 0.90 651 7 645 12 100.9 #4-6 17.9 118.2 146.6 0.81 0.259 0.0614 0.0005 0.899 0.013 0.106 0.001 0.82 650 7 654 17 99.5 #4-7 24.3 193.2 185.8 1.04 0.331 0.0615 0.0006 0.910 0.013 0.107 0.001 0.74 657 7 658 21 99.8

Syenitic orthogneiss CA34 #5-1 59.3 518.2 523.8 0.99 0.303 0.0619 0.0005 0.822 0.012 0.096 0.001 0.80 592 7 672 19 88.1 #5-2 37.6 279.8 365.8 0.77 0.230 0.0610 0.0006 0.763 0.010 0.091 0.001 0.72 560 5 638 20 87.9 #5-3 62.8 505.6 546.1 0.93 0.287 0.0617 0.0005 0.841 0.013 0.099 0.001 0.84 608 8 665 18 91.3 #5-4 62.7 435.1 551.9 0.79 0.239 0.0615 0.0005 0.855 0.012 0.101 0.001 0.80 619 7 657 18 94.3 #5-5 40.9 225.6 366.6 0.62 0.190 0.0615 0.0005 0.877 0.011 0.103 0.001 0.71 634 5 657 19 96.5 #5-6 17.5 93.9 156.0 0.60 0.184 0.0602 0.0005 0.860 0.011 0.104 0.001 0.69 636 5 611 19 104.0 #5-7 29.5 189.8 259.9 0.73 0.235 0.0611 0.0006 0.874 0.013 0.104 0.001 0.77 636 7 644 20 98.8 #5-8 29.0 186.6 264.0 0.71 0.216 0.0614 0.0006 0.844 0.011 0.100 0.001 0.68 612 5 654 21 93.7 #5-9 25.3 196.6 189.7 1.04 0.346 0.0624 0.0008 0.977 0.019 0.114 0.002 0.75 693 9 689 27 100.6 #5-10 52.6 331.3 452.1 0.73 0.229 0.0614 0.0005 0.879 0.009 0.104 0.000 0.48 637 3 652 18 97.8

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#5-11 50.7 81.7 506.1 0.16 0.055 0.0612 0.0006 0.877 0.012 0.104 0.001 0.73 637 6 648 20 98.3 #5-12 58.6 278.5 540.4 0.52 0.159 0.0616 0.0005 0.862 0.011 0.102 0.001 0.70 623 5 661 18 94.3 #5-13 23.3 236.6 202.1 1.17 0.346 0.0611 0.0006 0.828 0.013 0.098 0.001 0.77 604 7 643 21 93.9 #5-14 56.7 116.4 554.7 0.21 0.069 0.0611 0.0005 0.874 0.012 0.104 0.001 0.80 636 7 644 18 98.7 #5-15 75.1 58.3 761.2 0.08 0.043 0.0599 0.0006 0.827 0.010 0.100 0.001 0.57 615 4 600 21 102.5 #5-16 29.0 131.1 266.7 0.49 0.138 0.0611 0.0005 0.869 0.010 0.103 0.001 0.63 633 4 644 18 98.3 #5-17 15.8 146.7 121.4 1.21 0.382 0.0609 0.0006 0.864 0.016 0.103 0.002 0.85 632 10 635 22 99.4 #5-18 25.6 173.3 216.0 0.80 0.246 0.0610 0.0006 0.866 0.012 0.103 0.001 0.72 632 6 638 21 99.1 #5-19 28.8 193.8 238.1 0.81 0.250 0.0612 0.0006 0.885 0.013 0.105 0.001 0.71 643 6 645 21 99.8 #5-20 39.1 259.7 326.3 0.80 0.247 0.0617 0.0005 0.884 0.010 0.104 0.001 0.67 638 5 662 18 96.3 #5-21 51.5 199.7 503.9 0.40 0.126 0.0624 0.0005 0.837 0.009 0.097 0.001 0.54 598 3 688 19 87.0

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Table 2

Major and trace element analyses of orthogneisses and temperature estimates from zircon (TZr) and apatite (TAp) saturation thermometry and Al2O3/TiO2 ratio (TAl/Ti).

Sample AA-15A AA-15B AA-19A AA-21 AA-22 GUS-112 GUS-21 CA-40 CA-160 CA-162 VAN-15 CA-34SI CA-34DI Altinho orthogneiss Pinhões Syenite Diorite

Major elements (wt.%)

SiO2 69.17 67.09 66.35 68.00 68.91 66.62 66.53 66.95 61.71 65.0 65.31 64.7 63.43

TiO 2 0.48 0.55 0.64 0.56 0.43 0.56 0.64 0.55 0.74 0.6 0.47 0.63 1.09

Al 2O3 15.48 16.03 15.18 14.58 15.14 15.41 15.05 13.55 16.77 16.11 16.77 15.76 15.82

Fe2O3 3.26 3.09 4.01 3.29 2.56 3.49 3.65 4.85 5.99 4.98 3.65 5.12 4.01 MnO 0.08 0.08 0.07 0.06 0.05 0.06 0.06 0.09 0.14 0.1 0.07 0.1 0.07 MgO 0.71 1.00 1.75 1.40 1.13 1.63 1.65 2.45 2.0 1.51 1.08 1.67 1.44 CaO 2.72 1.87 2.89 2.60 2.49 2.87 3.00 4.37 4.18 3.3 2.08 3.31 2.81

Na2O 4.39 4.46 4.06 3.63 3.98 3.77 3.52 4.07 4.49 4.02 4.27 3.84 3.25

K 2O 2.59 4.12 3.64 4.6 4.33 4.28 4.53 2.02 2.62 3.48 4.23 3.49 6.29

P2O5 0.16 0.28 0.22 0.18 0.16 0.25 0.21 0.17 0.23 0.18 0.171 0.23 0.56 LOI 0.7 1.0 0.8 0.9 0.5 0.7 0.7 0.7 0.8 0.4 0.8 0.9 0.9 Total 99.74 99.57 99.61 99.8 99.68 99.64 99.54 99.77 99.72 99.7 98.90 99.75 99.63 Trace elements (ppm) Ni 5 8 25 18 10 18 17.7 52 <20 <20 <20 <20 <20 Co 47 52.1 43.2 42.9 33.7 45.6 0 28.7 29.5 19.8 97.1 22.8 17.8 Sc 7 5 9 8 5 7 10 11 13 10 9 7 2 V 41 46 69 54 44 61 72 91 89 69 40 73 65 Pb 0 0 0 0 0 2.9 0 2.6 3.2 3.5 9.5 6.8 4.3 W 405.6 410.5 316.5 328.7 277.3 324.7 0 181.7 222.7 117.4 981.3 119.7 85.8 Rb 104.7 182.5 117 156.9 143 190 145.4 34.9 92.3 99.4 128.0 140.9 202.9 Cs 5.9 7.5 3.6 3.8 5.6 9 0 0.8 3.6 2.7 3.0 9.6 6.6 Ba 941.9 1768.3 1350.1 1118.6 1177.3 1223.1 1105.1 737 770 1189 5763 754 1317 Sr 283.3 611.5 708.5 468.2 555.8 682.6 528.1 417.3 414.6 435.4 2706.0 423.2 561.4 Ga 16.8 23.7 18.8 20.3 19.0 21.9 19.4 11.4 18.4 16.8 21.5 16.6 16.5 Ta 1 2.2 1.7 2.0 1.3 1.1 2.6 0.6 0.9 0.7 0.9 1.5 3.8 Nb 12.3 16.9 14 15.4 10.7 11.8 18.3 10.1 15.4 17.4 14.1 35.1 31.3 Hf 5.4 5.7 7.9 7.3 5.8 5.2 8.7 4.7 7.6 6.7 7.4 4.8 9.6

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Zr 186.9 246.7 294.1 262.5 211.1 211.9 275.9 169.2 264.4 237.0 270.7 166.1 400.1 Y 26.5 16.9 22.3 31.5 17.3 15.0 36.8 16.6 28.0 26.0 15.9 23.5 31.8 Th 17.0 12.2 14.1 20.6 17.5 31.5 19.1 4.5 8.6 11.3 18.7 22.3 18.5 U 2.0 2.3 1.8 3.4 3.4 4.6 4.5 0.7 1.4 0.9 2.2 5.5 5.7 La 47.1 35.7 38.3 43.7 39.8 44.8 41.1 23.3 31.2 41.7 91.0 43.6 70.8 Ce 85.7 81.1 88.4 97.3 79.1 87.4 94.4 47.3 63.0 83.2 161.4 90.2 171.5 Pr 9.62 7.50 9.83 11.69 8.49 9.57 11.34 5.51 7.5 9.09 17.74 9.44 21.2 Nd 35.8 28.6 37.9 46.2 29.9 34.6 47.6 21.5 30.5 35.8 62.4 36.5 88.7 Sm 6.2 4.6 6.7 8.8 4.9 6.3 9.8 4.05 6.21 6.37 8.97 5.66 14.0 Eu 1.21 0.93 1.40 1.43 0.99 1.18 1.42 1.07 1.32 1.35 2.30 1.07 2.66 Gd 4.66 3.54 4.82 6.62 3.90 3.43 6.89 3.64 5.4 5.39 4.86 5.01 9.49 Tb 0.91 0.57 0.79 1.03 0.50 0.49 1.11 0.53 0.84 0.88 0.67 0.75 1.28 Dy 4.44 2.97 3.83 5.85 2.89 2.40 6.44 2.91 4.95 5.07 3.24 4.02 6.12 Ho 0.89 0.58 0.74 1.09 0.57 0.44 1.24 0.57 1.0 0.89 0.50 0.89 1.14 Er 2.41 1.43 2.12 2.87 1.58 1.28 3.48 1.85 3.07 2.74 1.38 2.65 3.09 Tm 0.39 0.23 0.30 0.47 0.23 0.22 0.48 0.27 0.41 0.38 0.18 0.39 0.46 Yb 2.35 1.38 1.98 2.73 1.56 1.29 3.23 1.78 2.89 2.23 1.13 2.37 2.96 Lu 0.36 0.22 0.32 0.37 0.24 0.20 0.49 0.29 0.44 0.34 0.15 0.38 0.43 Be 1 4 4 3 2 1 Sn 1 2 2 3 Cr2O3 0.003 0.002 0.002 0.004 Mo 0.5 0.5 0.5 0.3 43.5 2.1 Cu 2.9 71.4 12.4 4.5 9.7 55.7 Zn 27 72 60 77 69 62 Ni 28.2 9.0 6.1 14.1 7.2 13.1 As 0.8 <0.5 0.6 <0.5 <0.5 0.6 Cd <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Sb <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Bi <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Ag <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Au 1.3 1.5 1.5 0.7 <0.5 1.1 Hg 0.01 0.02 <0.01 0.02, <0.01 0.02 Tl 0.1 0.4 0.3 0.6 0.7 0.7

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Se <0.5 <0.5 <0.5 <0.5 <0.5 <0.5

TZr (°C) 793 817 819 809 794 791 811 750 798 800 826 769 836

TAp (°C) 945 989 952 946 942 970 948 929 904 914 912 939 1042 TAl/Ti (°C) 904 920 953 938 891 929 954 947 960 933 889 944 1036

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Table 3.

Rb-Sr and Sm-Nd isotopic compositions of the Altinho (CA-40), Pinhões (Van-15), syenitic (CA-34Si) and dioritic (CA34Di) orthogneisses. Initial compositions recalculated to crystallization ages. Both 1-stage and 2-stage Nd model ages are provided.

Sample Sm (ppm) Nd (ppm) 147Sm/144Nd 143Nd/144Nd erro (2σ) ε(Nd) TDM, 1-s TDM, 2-s Rb (ppm) Sr (ppm) 87Rb/86Sr erro (1s) 87Sr/86Sr erro (2σ) (87Sr/86Sr)i

CA-40 4.226 22.524 0.1135 0.512239 0.000010 -0.84 1.315 1.359 40.0 420.6 0.275 0.007 0.707300 0.000063 0.704743 Van-15 6.133 36.416 0.1018 0.512189 0.000010 1.79 1.25 1.312 121.8 702.1 0.502 0.003 0.710270 0.000011 0.704033

CA-34Si 185.2 481.6 1.114 0.010 0.714834 0.000053 0.704731

CA-34Di 235.2 566.2 1.203 0.002 0.715420 0.000077 0.704504

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Figure 1. (a) Pre-drift reconstruction of South America-Africa showing the Andean belt,

Archean/Proterozoic cratons and Brasiliano/Pan-African provinces of western

Gondwana. BP: Borborema Province. (b) Sketch showing the subdivision of the

Borborema Province in Northern (ND), Central (CD) and Southern (SD) domains.

Shear zone systems: PaSZ, Patos; EPSZ, East Pernambuco; WPSZ, West Pernambuco.

(c) Simplified geological map of the area outlined in (b) highlighting domains and

subdomains referred in the text and location of Figure 2. CSF: São Francisco Craton;

CD: Central Domain; PEAL: Pernambuco-Alagoas Domain; CVB: Cariris Velhos Belt;

SB: Sergipano Belt with subdomains Macururé (MSD), Marancó (MaSD), Poço

Redondo (PRSD) and Canindé (CSD).

Figure 2. Geological map of the study area showing the location of the dated samples.

Figure 3. Field and micropetrographic aspects of studied orthogneisses. (a, b) Pinhões

orthogneiss. (a) Contact with banded orthogneiss (top of photo). (b) Typical

microstructure with foliation defined by semicontinuous biotite foliation and

quartzfeldspathic bands. Crossed nicols. (c-f) Altinho orthogneiss. (c) Banded facies.

(d) Augen gneiss facies. (e) Microstructure with foliation defined by recrystallized

quartz layer (center of photo) separating a layer rich in larger K-feldspar crystals (top)

from a largely recrystallized fine-grained layer (bottom). (f) Equigranular, medium-

grained gneissic fabric with foliation defined by biotite flakes running from bottom left

to top right. (g, h) Syenitic orthogneiss. (g) Folded sub-horizontal contact between dark,

fine-grained dioritic band (bottom) and medium-grained syenitic band (top). The

contact is truncated by a subvertical mylonitic foliation (parallel to hammer; barely

visible in the photo) and granitic sheets. (h) Microstructure of the syenitic band showing

feldspar-rich and actinolite-rich layers with asymmetric porphyroclasts indicating

dextral shear. Section cut parallel to the stretching lineation and normal to the mylonitic

foliation.

Figure 4. (a, c) Stretching lineation (parallel to pen) in the Pinhões (a) and Altinho

orthogneisses (c). (b, d) Shear criteria indicating top-to-the-northeast tectonic

transport.in the Pinhões (b) and Altinho orthgoneisses (d). (b) Asymmetric fold. (d) S-C

fabric.

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ACCEPTED MANUSCRIPTFigure 5. U-Pb concordia diagrams and probability plots for zircons of metasedimentary

samples SB-1 (A) and BB-9 (B). In the density probability plots, the dashed line

combines all analyses, whereas the heavy line represents only concordant (concordance

> 95%) analyses.

Figure 6. U-Pb concordia diagrams for zircons of the Pinhões (A), Altinho (B), and

syenitic (C) orthogneisses.

Figure 7. Major element characteristics of orthogneisses.

Figure 8. (a) Whole-rock rare earth element abundances normalized to chondrite

(Boynton, 1984). (b) Spider diagram for whole-rock element abundances normalized to

primitive mantle (McDonough and Sun, 1995).

Figure 9. (a) Zr+Nb+Ce+Y versus FeO/MgO discrimination diagram of Whalen et al.

(1987). A: A-type granites; FG: fractionated felsic granites; OFG: unfractionated I, M

and S granites. (b) Nb versus Y discrimination diagram of Pearce et al. (1984). WPG:

within-plate granite; ORG: ocean ridge granite; VAG + Syn-COLG: volcanic arc- and

collision-related granites.

Figure 10. Inferred geological evolution of the study area based on data from this study

and previous ones. (a) Beginning of extension. Erosion of uplifted basement blocks

yields sediments with Paleoproterozoic-only zircons (possible protoliths of paragneiss

sample SB-1) whereas blocks that also enclosed Tonian and early syn-extensional

intrusions provide sediments dominated by Neoproterozoic zircons. (b) Advanced

stages of extension. Decompression melting allows partial melting of the lithospheric

mantle and interaction of the resultant magmas with those produced by melting of the

lower crust (possible protoliths of the syenitic orthogneiss and Altinho orthogneiss).

Part of this material was available for erosion, being responsible for the youngest

zircons found on paragneiss sample BB-9. (c) Contractional deformation and

concomitant high-grade metamorphism. The initiation of basin inversion is bracketed by

the upper intercept and weighted mean ages of the syenitic gneiss (646 Ma and 636 Ma,

respectively) and the oldest metamorphic ages (632-623 Ma; Neves et al., 2006, 2009,

2012). High temperatures allowed partial melting of a variety of protoliths, including

syn-extensional mafic rocks, preexisting crust and metamorphosed sediments. Thrusting

continued to at least 606 Ma (Neves et al., 2008). See text for further discussion.

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Recife

200 km

ND

CD

SD

EPSZ

Area of Fig. 1c

N

Phaneroiccover

Shear zones

BP

CratonsBrasiliano-Pan-African beltsand Phanerozoic cover

Andean belt

WPSZ

PaSZ

(a) (b)

8ºS

5ºS

Atlantic Ocean

36ºW

39ºW42ºW

São FranciscoCraton

ParnaíbaBasin

100 km

~

~~

~~

~

~

~~

~~

~~

~~

~ ~

~

Recife

Macéio

Aracaju

JoãoPessoa

SFC

10°

WPSZEPSZ

PEAL

SB

PEAL

~~ São Francisco Craton

Paleoproterozoic andundifferentiated orthogneisses

Supracrustal belts

Tonian orthogneisses

Brasiliano plutons

Phanerozoic cover

Shear zones

(c)

CSD

MSD

PRSDMaSD

Area of Fig. 2

CVB

CDCD

SB

08°

36°38°

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Paleoproterozoic and undifferentiated orthogneiss

Mesoproterozoic orthogneiss

Pinhões orthogneiss

Altinho orthogneiss

Metasedimentary rocks

Plutons and orthogneisses:620-600 Ma

Plutons < 600 Ma

8°50’8°50’

Caruaru

Gravatá

Belo Jardim

Lajedo

Altinho

São Benedito do Sul

Palmares

Bonito

Bom Jardim

Surubim

Toritama

Aroeiras

Trace of foliation

Dextral shear zone

Sinistral shear zone

Town

N

0 10 20 km

8°30’8°30’

7°30’7°30’36°00’

36°00’

8°00’8°00’

BB-9

SB-1

CA-40

CA-34

GE-1

U-Pb samples

Foliation

Lineation30°

10°

20°11° 28°

30°

9°

40°

19°

26°

9°

40°

22°

73°24°

27°61°

27°21°

10°

7°

42°

6°

27°7°

25°

34°10°

50°28°

19°

15°

37°

4°

19° 19°

18°

14°

18°

15°

34°3°

26°

54°20°12°

18°

8°

21°21°24°6°

19°

9°

63°

26°

52°43°

23°

17°

33°

24°

12°

43°

28°

64°

43°

32° 46° 41°

35°

9°6°

56°12°

58°

71°

10° 2°

35°

28°

36° 52°

40°

22°

22°

2°

16°

39°37°

27°

27°

30°

50°

87°

62°

15°

12°10°

10°55°

55°

30°

E P S Z

16°

16°

17°

50°

16° 5°

40°

30°

C A B

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(c)

(d)

(e) (f)

0.5 mm

Banded gneiss

Pinhões orthogneiss

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(g) (h)

(e) (f)

0.5 mm

0.5 mm0.5 mm

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NE

NE

(a) (b)

(c) (d)

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2400

2000

1600

1200

800

0.0

0.1

0.2

0.3

0.4

0.5

0 2 4 6 8 10 12 14

207Pb/235U

Paragneiss SB1

2214 ± 22 Ma

> 2669 ± 14 Ma

Fan like domain

(c. 590 / 2100 / 2200 Ma)

2003 ± 36 Ma

400 900 1400 1900 2400

587 ± 12 Ma(n = 1)

c. 2100 Ma(n = 30)

c. 2200 Ma(n = 1)

Figure 5a

A

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1050

950

850

750

650

550

0.08

0.10

0.12

0.14

0.16

0.18

0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

207Pb/235U

Paragneiss BB9

206P

b/23

8U B

400 600 800 1000 1200

c. 650 Ma(n= 6)

c. 680 Ma(n = 3)

c. 1000 Ma

(n =29)

c. 900 Ma(n = 11)

c. 850 Ma(n = 3)

Figure 5b

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900

860

820

780

0.12

0.13

0.14

0.15

0.16

1.1 1.2 1.3 1.4 1.5

207Pb/235U

206P

b/23

8U

Pinhoes Orthogneiss GE1

Figure 6a

Upper intercept:869 ± 9 Ma

(MSWD = 0.8; n = 27)

to -37 ± 280 Ma

A

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690

670

650

630

610

0.096

0.100

0.104

0.108

0.112

0.116

0.80 0.84 0.88 0.92 0.96 1.00

207Pb/235U

Altinho Orthogneiss CA40

Upper intercept:646 ± 13 Ma

(MSWD = 0.27; n =6)

652 ± 6 Ma(MSWD = 0.5; n = 5)

680 ± 15 Ma(2σ)

to 63 ± 630 Ma

206P

b/23

8U

Figure 6b

B

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650

630

610

590

570

0.086

0.090

0.094

0.098

0.102

0.106

0.110

0.72 0.76 0.80 0.84 0.88 0.92

207Pb/235U

Syenitic Orthogneiss CA34

Low Th/U grain615 ± 8 Ma(2σ)

Upper intercept at:646 ± 11 Ma

(MSWD = 0.7; n = 19)

206 Pb/238 U weighted mean:

636 ± 3 Ma(MSWD = 0.3; n = 11)

206P

b/23

8U

Figure 6c

C

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50 55 60 65 70 75 80

00

.20

.40

.60

.81

ferroan

magnesian

50 55 60 65 70 75 80

-8-4

04

81

2

alkalic

alkali-calcic

calc-alkalic

calcic

0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9

0.6

11

.41

.82

.22

.63

metaluminous peraluminous

peralkaline

ASI

SiO2

SiO2

Fe

Ot/

(Fe

Ot+

Mg

O)

Na

O+

KO

-Ca

O2

2

(a)

(b)

(c )

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

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La Pr Pm Eu Tb Ho Tm Lu

Ce Nd Sm Gd Dy Er Yb

110

100

1000

SpiderplotPrimitivemantleMcDonoughandSun1995

Cs Ba U Ta Ce Pr P Zr Eu Dy Yb

Rb Th Nb La Pb Sr Nd Sm Ti Y Lu

110

100

1000

(a)

(b)

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

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1 10 100 10001

10

10

01

00

0

ORG

VAG+syn-COLG

WPG

Y

Nb

50 500 5000

13

10

30

10

05

00

A

FG

OTG

Zr+Nb+Ce+Y

Fe

Ot/

Mg

O

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

Pinhões orthogneissAltinho orthogneissSyenitic orthogneissDioritic orthogneiss

(a) (b)

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Preexistent crust(mainly 2.2-2.0 Ga-old)

Older Neoproterozoicmagmatism (1.0-0.7 Ga)

Syn-extensional Neoproterozoicmagmatism (0.69-0.64 Ga)

Sediments of localprovenance

Sediments with local/distalprovenance

Sedimentary and metamorphic rocks

Basaltic underplating

Oceanic proto-crust

690-660 Ma

660-636 Ma

Moho

Sea level

Sediments with Paleoproterozoic-only zircons

Sediments with Neoproterozoic zircons

25 km

25 km

Syn-colisional magmatism

636-606 Ma

?

25 km Partial melting zones

(a)

(b)

(c)