Precambrian Research 175 (2009) 187–205

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Precambrian Research

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The age distributions of detrital zircons in metasedimentary sequences in eastern Borborema Province (NE Brazil): Evidence for intracontinental sedimentation and orogenesis?

Sérgio P. Neves a,∗, Olivier Bruguier b, José Maurício Rangel da Silva a, Delphine Bosch b, Vanja Coelho Alcantara a, Cristiane Marques Lima a a Departamento de Geologia, Universidade Federal de Pernambuco, 50740-530 Recife, Brazil b Géosciences Montpellier, Université de Montpellier II, 34095 Montpellier, France article info abstract

Article history: Detrital zircons in metasedimentary rocks attributed to three different complexes in the Central and Received 14 April 2009 Pernambuco-Alagoas domains of the Borborema Province, northeastern Brazil, were dated by LA-ICP- Received in revised form 4 September 2009 MS. Two samples from each of the following complexes were analyzed: Sertânia and Surubim, in the Accepted 20 September 2009 Central Domain, and Rio Una, in the Pernambuco-Alagoas Domain. One sample of the Sertânia Complex yielded only Paleoproterozoic zircons, whereas Neoproterozoic zircons predominate in the other, with the Keywords: youngest zircon indicating deposition after 642 Ma. One of the samples of the Surubim Complex yielded, Laser ablation ICP-MS again, only Paleoproterozoic concordant zircon ages. In the other sample, although Paleoproterozoic Detrital zircon geochronology Metasedimentary belts zircons predominate, ages vary from the Mesoarchean to the Neoproterozoic. The age of the youngest Provenance zircon in this latter sample indicates deposition after 850 Ma and an overgrowth on an Archean grain Brasiliano orogeny yielded an age of 623 ± 6Ma(2), interpreted as the age of peak metamorphism. The two samples of the Continental reconstructions Rio Una Complex yielded predominantly detrital zircons with ages in the ranges 2.2–2.1 Ga and 1.7–1.6 Ga. In this complex, the youngest detrital zircon suggests deposition after 917 Ma and metamorphic zircons indicate peak metamorphic conditions between 600 Ma and 617 Ma. The results of this study, together with available data from the literature, allow the following conclu- sions: (a) The Sertânia Complex is a Neoproterozoic sequence, and not Paleoproterozoic, as previously thought; (b) The similarity in lithological associations, detrital zircon populations and C isotope signature between the Sertânia and Surubim complexes suggest that they belong to the same lithostratigraphic unit; (c) Although the Rio Una Complex can be older than the Sertânia/Surubim Complex, the lack of zir- cons younger than 900 Ma can also result from insufficient sampling or absence of young rocks alongside the drainage system that collected detritus to this complex; (d) The regional metamorphism related to the Brasiliano Orogeny attained its climax at 630–600 Ma; (e) The age spectra of detrital zircons require their derivation from erosion of rocks formed not only during known geological events in the Borborema Province and in the nearby São Francisco/Congo Craton, but also from the Amazonian Craton, suggest- ing accumulation in an intracratonic setting within a preexisting large continent; (f) The short timespan between deposition and orogenic deformation may explain the overall medium- to high-temperature metamorphism due to maintenance, in the subsequent compressional event, of the elevated geothermal gradients produced during broad-scale lithosphere extension. © 2009 Elsevier B.V. All rights reserved.

1. Introduction age(s), provenance and metamorphism of its diverse supracrustal belts. These data will allow comparisons and correlations to be The Borborema Province, northeastern Brazil, occupies a cen- made both across the province and with other Neoproterozoic tral place in western Gondwana (Fig. 1). Therefore, understanding provinces and cratons in western Gondwana, and will place more its tectonic evolution is crucial to place constraints on conti- robust constraints on geodynamic models of tectonic evolution. nental reconstructions, which requires knowledge of deposition For instance, did western Gondwana grow by amalgamation of several disparate crustal fragments or did it result from rework- ing of a previous continent? In the latter case, was this continent ∗ Corresponding author. Tel.: +55 81 21268240; fax: +55 81 212618234. part of the Columbia and/or Rodinia supercontinents? Answers to E-mail address: [email protected] (S.P. Neves). these questions require consideration of the large tracts of Archean

0301-9268/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.precamres.2009.09.009 188 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205

Fig. 1. (a) Sketch map of western Gondwana showing the distribution of the main cratons and Brasiliano/Pan-African belts. (b and c) Contrasting views on the late Neopro- terozoic paleogeography of western Gondwana. (b) Interpretation according to which extension within a preexisting continent (Atlantica) was followed by convergence and intracontinental reworking with minor or no consumption of oceanic lithosphere (Neves, 2003). (c) Interpretation according to which large oceans with intraoceanic volcanic arcs separating cratons and microcontinental fragments closed around 600 Ma (Cordani et al., 2003). Abbreviations: A, Amazonia; BNC, Borborema-Nigeria-Cameroon; CG, Central Goiás; K, Kalahari; LA, Luís Alves; PA, Paraná; RP, Rio de La Plata; SA, Sahara Metacraton; SCC, São Francisco/Congo; WA, West Africa. and Paleoproterozoic crust, and their supracrustal cover, present in mentary successions deposited in an extended continental domain, northeastern Brazil (Borborema Province) and central and northern perhaps with small intervening ocean basins (Neves, 2003; Neves Africa (Nigeria, Cameroon and Hoggar provinces). This is generally et al., 2004, 2006a; Van Schmus et al., 2008). In this latter case, not contemplated in the most recent paleogeographical reconstruc- a (para)autochthonous setting is implied. Until the nineties, ages tions for the Neoproterozoic (e.g., Meert and Torsvik, 2003; Pesonen of supracrustal belts in the Borborma Province were unknown, et al., 2003; Tohver et al., 2006; Rino et al., 2008). Where it is, rather although some of them were attributed, somewhat arbitrarily, to contrasting models are presented (Fig. 1). On one extreme, these the Paleoproterozoic, Mesoproterozoic or Neoproterozoic. Since provinces are shown as continental fragments in a large ocean sep- then, several geochronological works (reviewed below) were car- arating the São Francisco and Amazonian cratons (Cordani et al., ried out, but the amount of data is still meagre. In order to 2003), which was not yet completely closed by 550 Ma (Trindade et improve knowledge, we present in this contribution U–Pb ages of al., 2003, 2006). On the other extreme, an early assembly of western detrital zircons from metasedimentary rocks ascribed to three dif- Gondwana within a long-lived continent is envisaged (Castaing et ferent complexes in the eastern portion of the Borborema Province al., 1994; Rogers, 1996; Piper, 2000, 2007), with the Brasiliano/Pan- (Figs. 2 and 3). African orogen regarded as mainly intracontinental (Neves, 2003). In between these two models, Van Schmus et al. (2008) recently 2. Previous U–Pb studies suggested that separation of the Amazonian/West African craton from the São Francisco/Congo craton formed a large Neoprotero- The basement of the Borborema Province mainly consists of zoic ocean and that the Borborema Province and its counterparts Paleoproterozoic orthogneisses with U–Pb zircon ages comprised in central and northern Africa are extended portions of a larger con- between 2.2 Ga and 2.0 Ga (see reviews by Brito Neves et al., 2000; tinent from which the São Francisco/Congo Craton is the relatively Neves, 2003; Van Schmus et al., 2008), although exposures of undeformed remnant. Archean (Fetter et al., 2000; Dantas et al., 2004; Arthaud et al., 2008) The Borborema Province is frequently referred, by a group of and early Paleoproterozoic (ca. 2.3 Ga; Fetter et al., 2000; Melo workers, as a branched system of orogens (Brito Neves et al., et al., 2002; Santos et al., 2008a) crust are found in the northern 2000; Fuck et al., 2008), with the underlying assumption that and central domains. In the northern domain, the oldest exten- different metasedimentary units (and their gneissic basement) sive supracrustal units, with U–Pb ages of 1.75–1.80 Ga, are the are allochthonous and were amalgamated during Neoproterozoic Orós and Jaguaribe belts (Sá et al., 1995)(Fig. 2). They consist of accretionary orogenic events (Santos et al., 1999). Others, how- an association of metasedimentary and metavolcanic rocks domi- ever, infer that most supracrustal belts resulted from deformation nated by Al-rich schists and metarhyolites, interpreted as formed and metamorphism of Neoproterozoic sedimentary or volcanosedi- in a continental rift setting. The Saquinho Volcanic Sequence, in S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 189

Fig. 2. Schematic map of the Borborema Province showing the main shear zones, plutons and supracrustal belts. Where available, ages of deposition, as inferred from the U–Pb age of the youngest detrital zircon grain (italics) or from interlayered metavolcanic rocks (normal type), are also shown. See text for sources of data. Abbreviations for main transcurrent shear zones: CGSZ, Campina Grande; EPSZ, East Pernambuco; PaSZ, Patos; SPSZ, Senador Pompeu; WPSZ, West Pernambuco. the northwestern sector of the Borborema Province (Fig. 2), has metamorphic grade is higher (upper greenschist to amphibolite the same age of the Orós and Jaguaribe belts (Santos et al., 2008a). facies) and the metavolcanic rocks gave U–Pb crystallization zir- Except these ones, other supracrustal sequences dated so far in the con ages comprised between 990 Ma and 960 Ma (Van Schmus et northern domain gave Neoproterozoic ages: SHRIMP U–Pb dating al., 1995; Kozuch, 2003; Medeiros, 2004; Santos et al., in press). of detrital zircons from metasedimentary samples of the Seridó belt The name Cariris Velhos was coined to refer to the event that (Fig. 2) shows that its maximum deposition age is younger than produced this supracrustal sequence and associated metaplutonic 650 Ma (Van Schmus et al., 2003), whereas conventional U–Pb zir- rocks (Brito Neves et al., 1995; Santos et al., in press). Although con dating of metavolcanics in the Ceará and Médio Coreaú belts originally proposed as an orogeny, there is so far no evidence (Fetter et al., 2003) and of detrital zircons in the Ceará belt (Arthaud, for metamorphism associated with the Cariris Velhos event. This, 2007) imply deposition after 770–750 Ma (Fig. 2). together with consideration of rock type association, and the The central domain of the Borborema Province includes, from petrology and geochemistry of metavolcanic and metaplutonic west to east, the Cachoeirinha, Alto Pajeú, Alto Moxotó and East Per- rocks favor deposition during extension associated with continen- nambuco belts (Fig. 2). The Cachoeirinha Belt consists of greenschist tal rifting (Neves, 2003). Supracrustal sequences in the Alto Moxotó facies metapelites, metagreywackes and bimodal metavolcanics. and East Pernambuco belts comprise dominantly metasedimen- Samples of metarhyolites yielded crystallization ages comprised tary rocks with very minor amounts of metavolcanics. It has been between 625 Ma and 660 Ma (Van Schmus et al., 1995; Kozuch, proposed (Santos et al., 2004a) that an older sequence (Sertânia 2003; Medeiros, 2004). The Alto Pajeú Belt also comprises a Complex), restricted to the Alto Moxotó Belt, is either covered or sequence of metasediments and bimodal metavolcanics (Riacho in tectonic contact with a younger sequence (Surubim Complex). Gravatá Complex), but, in contrast with the Cachoeirinha Belt, the Detrital zircon grains from two samples of the Sertânia Complex 190 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205

Fig. 3. Simplified geological map of the study area showing location of samples analyzed in this study (bold type) and in previous studies (italics: Santos et al., 2004a; underlined: Neves et al., 2006a). yielded U–Pb SHRIMP ages around 2.0 Ga (Santos et al., 2004a), but sor basin have ages of ca. 650 Ma, 750 Ma, 950–1000 Ma, 1800 Ma the age of sedimentation is still unconstrained. For the Surubim and 2200 Ma, with a smaller contribution of Archean rocks (Van Complex, LA-ICP-MS U–Pb ages of detrital zircons indicate that its Schmus et al., 2003). In the Surubim Complex, populations of detri- deposition is younger than 665 Ma (Neves et al., 2006a). tial zircons cluster at 870–760 Ma, 1200–1150 Ma, 2060–1940 Ma, The southern portion of the Borborema Province is subdivided and ca. 2200 Ma (Neves et al., 2006a). Finally, in the Sergipano Belt, in a northern sector made up of high-grade, often migmatitic, most detrital zircons display U–Pb SHRIMP ages in the intervals orthogneisses and metasedimentary rocks (Pernambuco-Alagoas 900–1100 Ma and 1900–2100 Ma (Oliveira et al., 2006). These data Domain), and two southernmost, predominantly metasedimentary point to a preponderance of sources formed during the Paleopro- units (Riacho do Pontal and Sergipano belts) (Fig. 2). U–Pb data terozoic Transamazonian event and in the early Neoproterozoic are not available for supracrustal rocks in the Pernambuco-Alagoas Cariris Velhos event, also including, in the Seridó and Surubim Domain and Riacho do Pontal Belt. In the northern, higher grade, cases, mid- to late Neoproterozoic sources. portion of the Sergipano Belt, available SHRIMP U–Pb ages of detri- tal zircons are older than 900 Ma (Oliveira et al., 2006). The presence 3. Geological setting of analyzed samples of associated ca. 950 Ma-old augen gneisses (Carvalho et al., 2005) suggests that this portion of the Sergipano Belt may be equivalent Samples for the present study were collected from clastic to the Alto Pajeú Belt. The youngest zircon grain in the domi- metasedimentary units attributed to three different complexes nant medium-grade metasedimentary unit of the Sergipano Belt (Fig. 3): Sertânia (Alto Moxotó Belt) and Surubim (East Pernambuco yielded an age of 850 Ma (Oliveira et al., 2006) but a younger depo- Belt), in the central domain, and Rio Una, in the Pernambuco- sition age cannot be dismissed. Low-grade to unmetamorphosed Alagoas Domain. (meta)sedimentary rocks in the southern part of the Sergipano Belt The boundary between the Sertânia and Surubim complexes yielded detrital zircons with SHRIMP U–Pb ages as young as 570 Ma, strikes WSW-ENE (Fig. 3). On the east, it is marked by the sinis- indicating that they are synorogenic deposits formed through ero- tral Aroeiras shear zone; on the west, it is more arbitrarily defined, sion of the Brasiliano orogenic edifice (Oliveira et al., 2006). as no clear structural or lithologic difference was observed during Of the above-mentioned works, only those by Van Schmus et detailed field work conducted in the region. Both complexes are al. (2003), Neves et al. (2006a) and Oliveira et al. (2006) provide dominated by pelitic schists/gneisses and psammitic gneisses, with enough age data to allow assessments of provenance. For the Seridó intercalated lenses of quartzite, marble and calc-silicate rocks. The Group, the major sources that contributed detritus to the precur- assemblage quartz-plagioclase-biotite-garnet-sillimanite is ubiq- S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 191 uitous and temperature conditions were high enough to locally 4 points per peaks and a 20% mass window. The laser was oper- promote anatexis. Both complexes display gentle to moderately ated at an energy density of 15 J cm−2 at a frequency of 3 Hz or 4 Hz dipping schistosity, unless otherwise disturbed by later folds and using a spot size of 26 ␮m. A single analysis consisted of the and transcurrent shear zones. Lineations defined by alignment of acquisition of 15 s of gas blank and 45 s of ablation signal. Measured fibrous sillimanite and/or elongated quartz and feldspar grains have isotopic ratios were monitored with reference to the G91500 zir- gentle plunges dominantly to E/ESE, and kinematic indicators point con standard with a 206Pb/238U ratio of 0.17917 and a 207Pb/206Pb to non-coaxial deformation with top-to the-west-northwest sense ratio of 0.07488 equivalent to ages of 1062 Ma and 1065 Ma, respec- of shear (Neves et al., 2005). tively. The standard was measured four times each five unknowns The Pernambuco-Alagoas Domain occurs to the south of the in a sequence of 2 standards, 5 unknowns and 2 standards. Pb/Pb dextral East Pernambuco shear zone (Fig. 3). Supracrustal rocks in ratios in the unknown zircons were mass-bias corrected using a this domain are usually assigned to the Cabrobó Complex (Gomes, power law whose parameters were determined by repetitive anal- 2001). In the study area, this unit comprises garnet and sillimante- ysis of the reference material measured during the whole analytical bearing micaschists and pelitic gneisses, felsic paragneisses, and session. This mass-bias factor was used to correct the 207Pb/206Pb quartzites ascribed to the Rio Una Complex, for which a Paleopro- ratios measured on the unknown zircons and its associated error terozoic deposition age was proposed (Osako et al., 2006; Da Silva was added in quadrature to the 207Pb/206Pb ratios measured on Filho et al., 2007). The foliation usually dips gently to moderately each unknowns following the procedure described in Horstwood to the southeast. et al. (2003). Inter-element fractionation for U and Pb is more sen- Two samples from each one of the above-mentioned complexes sitive to analytical conditions and the Pb/U ratios of each batch of were collected for U–Pb geochronology (Fig. 3): VAN-2 and SE- five unknowns were calibrated against the bias factor calculated 1 (Sertânia Complex); SU-1 and CIV-54 (Surubim Complex); and using the four standards bracketing the five unknowns. The mean RU-1 and RU-2 (Rio Una Complex). Sample VAN-2 (7◦3039S, Pb/U ratio of the four measured standards was used to calculate 35◦4917W) consists of a relatively coarse-grained, feldspathic the inter-element fractionation and its error was then added in paragneiss bearing a flat-lying foliation dipping to the southwest. quadrature to the individual error measured on each 206Pb/238U It was collected in a roadcut close to the site of one of the sam- unknown. Accurate common lead correction is difficult to achieve, ples (SPP-PER) analyzed by Santos et al. (2004a), but a precise mainly because of the isobaric interference of 204Hg on 204Pb. The correspondence is not possible because these authors did not give contribution of 204Hg on 204Pb was estimated by measuring the geographic coordinates. Sample SE-1 (7◦3135S, 35◦3939W) is 202Hg and assuming a 204Hg/202Hg natural isotopic composition of from a decimeter-thick band of fine-grained pelitic micaschist 0.2298. This allows monitoring the common lead content of the with submilimetric garnet crystals intercalated within medium- analysed grain, but corrections often result in spurious ages. Anal- to coarse-grained garnet biotite gneiss. The rock shows a steep yses yielding 204Pb were thus rejected and Table 1 reports only foliation due to proximity of the Aroeiras shear zone (Fig. 3), but analyses for which no 204Pb was detected. Quoted ratios correspond strike-slip-related deformation was not strong enough to promote to measured ratios corrected from background and mass discrimi- recrystallization. Sample SU-1 (7◦3851S, 35◦4241W) consists of nation (+ elemental fractionation for the 206Pb/238U ratios). All ages a medium-grained muscovite-garnet-bearing feldspathic quartzite have been calculated using the U and Th decay constants recom- with a gentle northwestward dipping foliation and a strong min- mended by Steiger and Jaeger (1977). Analytical data were plotted eral stretching lineation (285◦,15◦). Sample CIV-54 (7◦3757S, and ages calculated using the IsoplotEx program (Ludwig, 2000). 35◦3710W) is from a fine-grained ultramylonite derived from a Individual analyses in the data table and in concordia plots are ±1 metapelitic protolith. Because the age and provenance of the Suru- errors and uncertainties in ages are quoted at the 2 level. bim Complex had been the subject of a previous study (Neves et al., 2006a), the additional objective of dating this sample was to 5. Detrital zircon analysis constrain the age of shear zone development. The two samples of the Rio Una Complex display flat-lying foliation. RU-1 (8◦2208S, A total of 329 analyses were obtained from the six samples, 36◦2659W) consists of a feldspathic quartzite whereas RU-2 of which 280 show less than 5% discordance (Table 1). Unless (8◦2435S, 36◦2917W) is an almost pure well-recrystallized otherwise stated, only these will be considered in the following quartzite. discussion. Ages of zircons are expressed in terms of either their 207Pb/206Pb ratios (grains older than 1 Ga) or their 206Pb/238U ratios (Neoproterozoic grains). The results are presented in corcordia and 4. Analytical techniques cumulative-probability plots in Figs. 4–6. Samples selected for laser ablation U–Th–Pb geochronology were processed by crushing, heavy liquid and magnetic separation 5.1. Sertânia Complex following conventional techniques (e.g., Bosch et al., 1996). Zircons from the non-magnetic fractions were hand-picked and mounted Detrital zircon grains from sample VAN-2 range from 100 ␮m along with chips of the G91500 zircon standard (Wiedenbeck et to 350 ␮m and have length to width ratios from 1:1 to 3:1. al., 1995) onto adhesive tape. Zircon grains and the standard were Only Paleoproterozoic ages were obtained (Fig. 4a and b). Three then enclosed in epoxy resin and carefully polished to about half main populations can be distinguished, with ages clustering in their thickness to expose internal structures. After carbon coating, the intervals 2.06–2.02 Ga, 1.99–1.97 Ga and 1.94–1.93 Ga (Fig. 4b). back-scattered electron (BSE) imaging of the zircon grains was car- A fourth population consists of five grains with discordance ried out using a JEOL 1200 EXII microscope at the University of smaller than ±5% that yielded ages older than 2.10 Ga, and Montpellier II. The mounts were then cleaned to remove the carbon up to 2.49 Ga (#13-1; Fig. 4a). The latter indicates the occur- coating, prior to laser ablation analyses conducted using a Geo- rence of late Archean/early Paleoproterozoic rocks in the source las automated platform housing a 193 nm CompEx 102 laser from regions. The youngest concordant grains have ages of 1871 ± 20 Ma, LambdaPhysik. For U–Th–Pb analyses, the laser was connected to a 1879 ± 24 Ma and 1910 ± 20 Ma, which requires deposition to post- Element XR sector field, single collector ICP-MS. Data were per- date the Transamazonian event. U/Pb ages ranging between 2.20 Ga formed at low resolution (M/M = 300) in the fast electrostatic and 1.97 Ga match those found in orthogneisses in the study region scan mode. Signals were acquired in pulse counting mode using (Sá et al., 2002; Neves et al., 2006a), suggesting provenance from 192 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 ) (1 ± Pb 206 Pb/ 207 ) (1 ± U 238 Pb/ 206 ) Rho Apparent ages (Ma) Conc. (%) (1 ± U 238 Pb/ 206 ) (1 ± U 235 Pb/ 207 ) (1 ± Pb 206 Pb/ 207 Pb 206 Pb/ 208 124 19 389 0.050 0.015 0.1179 0.0007 5.140 0.102 0.316 0.006 0.95 1771 29 1925 11 92.0 #1-1#2-1 52#3-1 130#4-1 75#5-1 94#6-1 75#7-1 89 11 97#8-1 45#8-2 50 121#9-1 47 118 146 470#10-1 91 60 114#11-1 82 242 1246 100#12-1 44 83 0.759#13-1 183 12 0.024 80#14-1 0.222 252 21 0.205 0.007 117#15-1 66 17 114 0.037 359#16-1 24 0.061 62 0.498 0.039 395#17-1 83 13 0.1253 0.324 103#18-1 0.148 153 0.1189 348 29 0.389 100#19-1 85 0.100 0.230 426 0.1132#20-1 0.117 0.1202 39 0.204 48 0.0007 0.069 137#21-1 24 0.0007 30 259 0.1301 0.434 0.060 220 0.048#22-1 38 330 6.607 0.1254 0.0007 114 0.057#23-1 65 0.123 4.770 0.0009 0.014 0.1238 164#24-1 0.1149 74 0.031 32 123 4.588 0.548 0.0011 245#25-1 227 4.289 93 0.1224 0.159 117 0.762 0.0008 0.259#26-1 0.147 0.158 91 260 6.673 0.1225 0.0008 0.1218#26-2 61 0.382 0.215 58 0.290 0.0008 0.078 0.093 0.291 6.275 140 0.1247#27-1 327 0.160 89 0.122 0.0007 1.143 6.393 0.084 143#28-1 4 555 0.294 5.098 0.159 48 0.259 0.1548 0.0009 0.035#29-1 0.250 0.0008 0.186 0.009 6.098 63 297 0.102 46 0.009 0.1632 0.1194#30-1 0.0008 0.372 59 0.075 0.376 0.083 69 6.243 0.97 0.364 5.768 171#31-1 0.062 0.363 0.006 211 0.1218 0.98 0.211 7 0.009 0.0012 259 4.508#32-1 0.118 0.073 75 0.375 2087 0.105 0.1214 94 0.1284 0.322 0.95 0.0011 1647 231 101 0.206#33-1 0.0007 0.061 0.008 0.98 0.117 40 0.099 0.361 9.532 124 131 0.1297#34-1 0.005 1662 10.798 0.0008 0.060 98 0.164 109 0.93 0.020 1484 5.791 442 107#35-1 0.369 0.343 0.004 0.186 0.0007 376 0.1285 0.0008 41 0.003 0.1344 0.92 172#36-1 0.262 44 2038 0.013 6.212 0.200 0.1279 0.162 66 0.004 0.87 0.055 174 100#37-1 0.0010 0.170 61 1996 5.860 0.82 0.556 7.120 0.099 28 0.057 155 146 0.1249#38-1 459 65 0.447 48 0.006 2034 2051 0.006 0.88 0.015 0.0010 413 0.480 1939 0.0015 1798 0.158 6.619 0.201#39-1 0.100 0.352 0.009 65 0.0007 39 0.92 0.1215 1988 0.004 267 0.93#40-1 0.093 95 0.079 1851 0.1176 83 0.228 0.059 6.815 295 0.370 26 7.774 1959 0.99 100#41-1 0.0009 60 0.007 2027 0.1272 0.637 1903 7.001 326 0.237 10 0.157 0.350 20 0.402 0.007 0.074#42-1 230 98 11 15 2100 0.006 0.1361 84 1501 0.89 0.0008 0.169 6.525 169#43-1 0.069 0.071 0.370 18 2035 0.91 0.1218 0.247 0.0007 433 0.236 57 12 0.005 0.1246 144 0.93 0.207#44-1 13 0.139 2012 2380 0.0008 270 44 102.6 30 0.385 26 0.005 5.879 1879 2526 0.072 0.004 137 0.201#44-2 62 0.420 5.713 0.1217 0.91 0.0008 1942 0.061 447 1.792 15 0.128 84.9 0.397 48 1992 138#45-1 6.867 0.008 0.1363 0.93 0.0007 0.060 0.82 0.1209 49 11 2029 182 116 0.219#46-1 0.0007 0.298 89.8 99 0.379 1994 7.801 1983 0.047 11 75.8 30 1936 0.003 232 0.94#47-1 0.222 2179 0.060 76 12 30 0.012 5.452 0.1184 85 2025 0.0008 0.063 275 27 0.008 6.438 0.1170 0.220#48-1 0.093 97.1 75 10 0.351 67 0.0010 2030 0.068 0.63 0.0007 0.352 0.93 244 123 0.1266#49-1 0.088 98.1 77 26 2400 0.007 5.820 0.316 0.065 473 0.1321 0.96 13 101.9 11 0.391 2489 2098 0.059 12 25 17 2259 6.246 98 0.188 1948 0.0007 378 5.925 0.070 95.7 11 0.416 0.143 0.1270 0.94 0.225 2155 0.0006 0.002 336 12 99.8 0.325 39 0.003 1983 0.056 0.1207 0.0007 0.140 0.375 5.493 0.201 2071 0.066 347 0.0007 13 35 101.7 0.005 0.62 1976 5.263 0.1151 0.210 2076 0.162 11 21 0.154 96.0 12 0.84 533 11 0.347 53 0.004 0.058 6.612 0.202 0.0007 159 74.1 35 1939 0.1418 0.89 2094 0.060 6.555 0.332 0.356 0.003 1946 281 0.224 0.0007 0.118 12 0.003 0.1191 0.84 0.059 0.096 32 2130 6.409 203 0.1190 0.223 2077 0.0006 99.2 10 101.5 11 2156 0.84 0.065 394 0.086 0.336 0.008 2241 5.824 0.85 0.022 2069 0.095 99.7 0.326 0.1187 0.0022 0.065 237 14 0.008 1812 0.009 4.925 0.1241 8 102.3 0.379 15 0.96 0.041 2028 0.0007 2051 0.014 0.073 0.360 0.1255 0.0007 14 22 105.0 6.672 0.96 0.174 0.97 20 0.078 97.9 0.007 1920 0.014 0.1291 0.054 10 0.366 18 5.707 0.006 0.0007 0.071 1979 1920 1850 0.054 5.727 0.1267 0.670 1961 0.0008 96.9 0.350 14 0.004 0.96 0.028 12 16 2060 0.005 0.1090 0.96 0.0007 0.303 0.310 101.0 5.563 0.170 104.8 2179 1870 5.916 0.90 0.0007 0.122 38 104.2 0.004 0.1166 1821 0.93 0.117 0.341 1983 6.467 0.0007 11 10 40 43 0.004 0.1145 2024 2070 0.348 102.1 7.038 0.1236 0.88 1981 0.0007 0.125 11 0.349 0.004 0.131 1981 6.880 0.1347 0.91 11 34 0.0007 2010 0.063 0.340 28 0.015 2180 3.485 0.93 1969 10 101.4 0.346 0.0006 1935 98.0 0.068 10 21 0.007 0.0007 103.4 0.374 23 4.939 0.007 0.94 1742 0.091 1932 0.0007 12 102.8 0.395 5.296 0.96 1910 0.070 17 0.007 1893 6.088 0.96 12 11 0.394 0.007 2052 91.4 101.4 20 1923 6.705 2126 0.060 0.232 0.003 0.96 1930 20 0.96 0.064 10 0.003 2057 0.225 96.9 10 0.307 1886 0.83 70 0.005 1966 1914 0.117 84.9 10 0.336 99.6 0.83 0.357 34 0.004 1882 2047 9 33 0.90 0.361 2148 96.7 0.003 2249 0.95 9 95.3 35 2141 10 100.9 35 0.004 1943 0.013 0.88 1941 1344 10 14 93.2 0.006 0.89 15 1937 1727 0.99 27 2017 97.7 22 1865 0.95 10 98.4 2036 1970 10 23 92.6 2086 1987 11 16 2052 84.2 11 17 1784 99.0 10 62 99.4 10 28 1904 97.4 10 1871 94.9 2008 12 100.6 2160 103.0 10 104.3 10 10 75.3 9 90.7 99.7 98.1 92.0 Sample VAN-2 Sample Pb* (ppm)Sertania Complex Th (ppm) U (ppm) Th/U Table 1 LA–ICP–MS U–Th–Pb results for detrital zircons from metasedimentary rocks of the Borborema Province (Brazil). S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 193 #50-1#51-1#52-1 80#53-1 85#54-1 77#55-1 38 82#56-1 43 79 41 68 214 111 41#1-1 251 39#2-1 213 12#3-1 216 0.176 220#4-1 24 0.170 203#4-2 21 0.192 192 250 0.051#5-1 28 0.187 105 0.051#5-2 39 0.193 0.058 83#6-1 48 0.064 0.861 117 0.1216 0.054 216#7-1 14 133 0.1181 0.057#8-1 15 191 194 0.1213 0.026 158 0.259#9-1 86 0.0007 0.1220 0.485 296 44#10-1 30 0.0007 0.1254 360 53#11-1 25 0.434 0.0006 375 0.1212 0.1251 0.742#12-1 18 0.0008 6.219 0.147 252 88 0.451 97#13-1 0.0007 108 5.567 228 13 0.540 0.129 399#14-1 0.0008 0.0007 5.660 0.221 228 93#15-1 101 0.059 4 0.0611 169 5.797 0.134 0.455 194#16-1 0.063 0.492 6.206 0.157 58 0.0613 32 0.940#17-1 0.083 0.0718 131 152 5.711 219 6.044 167 0.371 1.105 0.0003#17-2 0.107 0.0655 108 0.140 8 0.342 1.174 0.145#18-1 0.094 0.0651 0.0002 94 0.263 34 175 18 0.338 0.0003 296#19-1 0.102 0.096 0.611 0.460 0.003 0.341 14 0.345 0.0003 0.934#20-1 0.0659 66 33 0.003 0.363 1043 0.0662 19 0.359 0.0003 310#21-1 0.0795 0.613 0.926 0.005 71 53 0.342 0.350 0.563 0.187 1.601 0.134#22-1 0.83 0.0618 0.006 334 44 57 0.011 0.0003 1.148#23-1 162 0.87 0.249 0.0632 124 0.0003 0.005 0.168 0.111 0.0004 0.177 120 1.138#24-1 0.012 0.94 0.006 66 0.005 0.157 0.0626 19 0.019 0.1271 2033 0.0002#25-1 221 0.94 0.111 0.196 92 104 199 37 0.017 1896 0.078 0.0004 1.221#26-1 0.93 0.049 1.178 0.034 0.0668 22 0.015 0.109 0.586 1879 138 2.065#27-1 0.92 0.94 0.1770 0.0004 0.162 0.0004 316 69 14 1910 0.982 0.001 0.082 215#28-1 189 4 0.475 0.127 1.555 0.0638 0.015 10 16 1977 0.0660 0.913#29-1 131 0.013 0.0632 0.0004 0.127 0.001 0.174 16 0.036 22 0.477 1896 1937 134 0.0009 0.002#30-1 0.700 0.906 211 6.772 1981 39 0.020 29 0.91 0.1082 0.924 0.142 17 0.002 0.454#31-1 0.0006 0.134 171 0.0003 40 1927 0.012 24 0.129 0.0003 0.002#32-1 115 9 0.95 0.0666 0.188 1.246 0.133 1976 11.534 10 27 0.94 25 0.519 10 0.208#33-1 131 0.010 0.075 0.115 0.895 0.0004 1985 0.255 0.0664 33 0.96 0.0669 30 678 0.002 10#34-1 1.019 0.105 0.762 75 0.001 2034 1.222 56 0.94 0.0003 75 38 1.025 0.003#35-1 0.024 0.1262 670 0.117 9 0.153 287 38 1973 2030 72 0.0722 0.105 102.6 967 0.386 11 0.002 0.338#36-1 0.1610 0.0003 0.0003 50 4.525 0.91 33 0.570 771 10 0.025 0.001 0.235#37-1 7 0.90 0.536 98.4 0.018 83 23 0.021 0.96 0.135 1.525 58 769 0.0008 12 1.301 0.473#38-1 10 475 0.0656 0.457 69 0.0003 0.001 0.004 8 18 10 95.1 0.0719 0.98 199 0.0007#39-1 0.038 96.2 0.178 1.295 81 1.341 24 0.116 10 0.88 0.0619 813 0.167 103 0.134#40-1 235 97.2 782 0.118 1112 643 0.002 0.458 558 22 0.017 0.004 0.653 0.0003 6.170 0.134#41-1 143 9 0.83 0.561 96.1 0.95 95.4 0.0006 1.663 10.317 38 0.253 703 0.303 651 293 980 0.0679 158 0.015 0.020 0.003 0.0003 174 0.0695 46 0.002 0.799 642 10 790 0.002 9 107 0.95 0.0696 17 0.142 0.850 0.86 0.198 138 7 52 0.109 0.0661 0.169 2106 1.211 129 0.024 643 0.094 777 0.080 204 1.466 0.002 13 0.0006 9 0.141 0.277 8 0.145 0.93 176 0.0005 1.345 0.96 0.223 190 0.986 0.98 105.4 0.0004 8 0.002 0.222 2495 0.0658 216 1185 7 817 0.355 1.037 804 0.0003 346 0.0654 0.011 19 10 0.167 813 0.465 0.0718 0.023 0.90 0.774 0.002 0.081 450 0.002 6 102.9 1.313 667 0.394 0.1610 706 98.6 0.016 0.565 1.177 490 812 0.92 0.0668 0.0005 11 717 18 1.502 9 0.006 0.322 14 97.6 0.0003 10 0.134 0.374 715 1.204 0.002 2059 0.004 0.0003 0.148 1708 0.249 0.92 0.0654 99.0 0.96 0.390 0.022 0.0607 0.0008 8 0.115 695 0.171 15 0.027 0.441 11 0.0006 101.1 0.031 14 0.93 0.0629 2625 854 1.238 13 0.001 0.112 0.017 0.96 93.9 0.87 1.264 833 6 0.002 96.2 0.0607 11 0.0003 1.605 0.110 0.140 853 13 875 0.0003 10.064 0.002 0.0619 105.4 0.123 0.131 0.157 736 1956 0.0003 1.168 0.021 8 807 0.90 0.0637 13 0.132 715 2460 0.027 9 89.9 0.87 996 0.0003 102.3 0.021 1769 0.0612 0.002 1.124 0.215 12 0.96 0.0003 0.003 0.929 9 92.5 0.0623 19 0.003 0.058 0.136 28 0.0003 0.966 8 0.002 0.140 810 9 16 95.0 98.1 13 0.162 889 0.0002 827 0.877 7 0.87 0.035 0.453 0.94 0.017 704 0.0003 0.947 835 0.95 0.127 819 0.002 96.0 2046 0.014 0.96 100.6 0.003 0.979 100.3 2467 10 0.002 6 0.019 12 0.125 0.921 990 0.009 847 96.6 0.111 0.011 10 747 10 9 12 0.889 0.006 0.88 938 0.111 0.97 0.022 800 7 0.96 103.3 0.105 0.004 0.019 0.97 9 794 982 0.002 11 0.111 15 104.1 0.011 0.99 104.7 671 0.001 17 824 95.6 0.111 10 845 0.002 0.99 968 0.109 99.7 2410 16 0.97 100.6 8 0.001 0.103 865 0.94 770 9 915 0.002 11 915 16 0.97 809 0.002 11 42 758 102.0 0.89 90.6 17 679 0.001 16 35 0.97 105.0 681 13 800 0.98 642 8 789 2466 22 981 12 0.93 679 97.9 81.6 102.4 16 681 831 9 11 13 668 8 99.0 7 786 635 627 7 18 103.0 14 107.2 703 13 10 629 97.7 98.7 9 7 670 92.6 11 731 12 646 96.4 108.2 11 11 684 96.9 102.1 8 101.4 10 93.2 103.4 92.7 Sample SE-1 194 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 ) (1 ± Pb 206 Pb/ 207 ) (1 ± U 238 Pb/ 206 ) Rho Apparent ages (Ma) Conc. (%) (1 ± U 238 Pb/ 206 ) (1 ± U 235 Pb/ 207 ) (1 ± Pb 206 Pb/ 207 Pb 206 Pb/ 208 ) Continued #42-1#43-1 61#44-1 21#45-1 44 134#46-1#47-1 121 14#48-1 12 50#49-1 299 42 118#50-1 62 459#51-1 28 95 167#52-1 89 204 35#53-1 296 121 31 0.264#54-1 126 14#55-1 126 91 17 0.301 0.081 130 1.463#56-1 116 24 234 0.400 0.114#57-1 150 24 0.434 159#58-1 0.124 12 222 42 1.047 0.0665#59-1 118 64 0.273 278 0.516#60-1 108 0.314 0.0658 54 190 0.053 0.0721 0.793#61-1 75 0.154 0.1563 35 115 0.565#62-1 0.0003 29 0.218 117 31 0.419#63-1 13 0.0004 0.174 180 79 0.0662 1.267 0.790#64-1 0.0003 0.0664 27 0.149 0.0008 60 161 0.0725#65-1 1.190 23 0.223 74 119 1.460 1.726 0.1199 1.007#66-1 69 14 9.615 0.015 0.0003 155 0.0676 0.598#67-1 0.409 16 0.0005 0.558 60 104 0.1409#68-1 0.0003 0.034 0.138 0.219 0.187 75 0.027 1.163 5 131 0.0698#69-1 0.0004 339 0.217 1.329 18 61 0.131 0.445 0.070 1.721 0.0005 0.174 91 0.508 36 0.446 0.1211 5.799 0.0715 0.0021 0.136 0.002 62 0.574 0.018 55 0.141 1.074 243 0.0652 0.0005 0.142 0.560 0.351 0.023 0.004 0.161 6.245 183 0.93 0.127 0.003 0.0715 9 79 0.097 0.145 0.0006 0.158 0.010 1.408 101 0.0004 0.100 127 0.172 0.97 0.021 0.0718 0.976 834 135 0.96 0.0003 0.351 0.1301 0.309 0.97 0.217 6.150 1.538 0.115 0.002 794 0.271 0.1600 0.333 1032 0.0003 0.037 0.015 0.091 1.113 2378 0.321 44 0.002 96 0.1969 0.360 243 0.1158 0.95 0.0003 0.106 0.146 0.006 1.475 1.00 0.408 0.0004 0.103 0.038 9 0.171 0.96 0.002 0.0005 0.022 21 14 774 1.761 0.0736 0.123 0.98 0.368 0.156 44 874 0.010 6.866 0.0624 1025 0.0006 0.0003 0.209 0.815 0.92 0.521 0.044 0.124 0.004 9.663 0.0652 1939 822 13.498 0.91 0.085 0.245 0.0715 0.147 5.214 0.039 0.150 802 989 0.0005 704 0.96 2416 0.127 10 0.006 0.004 0.0638 1796 0.0003 87 12 0.134 0.178 0.002 0.0003 0.258 0.383 27 1.814 0.96 881 0.97 0.070 0.977 9 0.0005 0.438 0.0652 0.004 0.0714 0.1204 0.97 13 0.497 812 12 2022 1.124 0.0003 8 9 0.327 49 820 999 934 0.004 1.446 0.99 1954 0.028 0.007 753 0.015 21 1.072 101.5 0.0008 0.006 0.98 0.0003 0.0004 0.013 0.179 855 899 0.009 0.98 2239 10 99.1 104.4 0.114 28 0.004 16 0.051 98.5 21 1055 0.97 7 0.125 1.069 1.696 2089 5.874 0.99 0.022 6 14 921 0.97 0.147 2341 0.002 1972 2602 16 25 0.122 25 0.002 95.3 1822 106.6 972 0.043 0.030 0.099 102.6 21 0.001 0.88 32 781 0.96 15 99.2 0.005 0.119 0.172 0.354 26 1061 0.94 973 40 0.002 9 82.3 80.2 21 693 0.98 12 982 2100 760 0.98 10 2456 95.6 0.005 0.003 883 0.006 2800 13 1892 102.5 742 9 10 0.96 0.97 0.98 10 96.1 6 96.4 8 1029 1025 1953 6 28 725 5 5 14 688 92.3 107.4 99.5 779 15 16 28 970 26 95.3 92.9 734 96.3 9 1962 103.0 968 9 14 780 8 100.7 6 24 97.5 8 91.0 101.1 105.9 99.5 92.9 #1-1#2-1 58#3-1 11#4-1 30#5-1 43#6-1 177 22#7-1 11#8-1 24 29#9-1 52 18 139#10-1 24 16#11-1 48 87 22#12-1 19 26 77#13-1 33 285 59 1.280#14-1 43 13 58 0.360#15-1 32 1.082 41 41 30#16-1 0.673 20 71 0.317 80 0.084#17-1 22 73 0.187 38#18-1 0.833 0.060 0.1249 27 38 9 864#19-1 0.637 26 65 0.258#20-1 0.1268 0.417 53 61 42 0.239 149#21-1 0.1238 1.124 27 0.0006 19 0.128 0.0941 0.864 30 16 0.048 0.315 112 18 0.1235 0.0010 5.379 57 0.233 1.338 0.051 0.1240 0.0007 45 0.489 59 0.0010 6.549 0.1265 0.388 66 76 0.919 0.137 0.042 5.697 0.1260 0.0006 0.583 35 1.863 20 0.1229 0.0007 0.277 75 0.0769 0.312 0.940 0.197 166 0.067 5.466 0.0006 0.1249 0.290 0.048 5.192 0.0007 0.279 67 0.1234 0.027 0.375 5.929 0.940 0.0007 0.103 35 0.0007 0.334 0.002 0.1257 0.760 0.043 0.144 6.506 0.1250 0.359 0.282 0.0009 0.078 6.148 0.275 1.062 0.77 0.0005 0.321 0.003 0.1271 1.149 0.100 0.052 0.304 0.002 6.302 0.1123 0.988 1752 0.0006 0.095 0.001 0.67 0.331 6.084 0.0007 0.340 0.060 0.038 0.78 0.1252 0.284 0.374 0.002 2052 6.199 0.1245 0.66 0.0006 6.250 0.1239 0.055 0.363 0.100 0.004 1857 0.0012 0.029 0.77 9 0.002 865 6.345 0.1269 0.366 0.92 0.0005 0.105 0.358 0.005 1795 4.913 0.1254 0.0007 0.100 12 0.83 0.0005 0.003 1710 0.003 0.358 10 6.124 0.93 2027 0.114 0.363 1887 5.094 0.0007 0.002 0.79 5.937 0.96 0.132 8 2053 2050 0.001 0.0006 0.362 10 2011 1995 5.532 0.61 0.055 0.317 21 0.006 615 0.38 0.067 6.177 0.005 9 0.037 12 1509 2010 0.355 2007 0.95 1971 13 0.297 24 0.006 0.94 0.100 0.348 2014 13 0.008 1972 9 0.049 20 2050 0.96 1995 0.316 21 86.4 0.003 2043 0.92 0.357 9 0.004 1991 9 99.9 3 1999 0.002 10 0.90 1776 1119 27 0.90 92.3 26 0.005 0.72 9 2028 1957 57.3 0.002 2006 1676 9 29 0.95 1923 89.4 11 2038 84.9 19 38 0.80 2028 1771 92.0 12 14 2059 1969 100.3 18 8 1838 99.8 7 9 10 55.0 26 2032 2021 99.1 11 9 2013 19 98.3 2055 96.7 98.4 2035 7 10 96.7 8 96.7 10 96.3 8 82.9 95.6 86.2 96.8 Sample CIV-54 Sample Pb* (ppm) Th (ppm) U (ppm) Th/U Surubim Complex Table 1 ( S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 195 #22-1#23-1#24-1 40#25-1 14#26-1 27#27-1 39 15#28-1 10 14#29-1 75 74 103#30-1 26 19 124#31-1 36 74#32-1 105 55 18 0.376#33-1 39 53 56 0.078#34-1 113 40 245 51#35-1 1.371 0.112 29 34#36-1 0.682 46 0.094 232 35 18#37-1 140 0.904 0.430 20 0.402#38-1 0.1258 44 85 21 0.233 159#39-1 0.0875 1.142 0.486 204 37 60 0.285 0.127#40-1 28 0.1250 40 0.0006 160 0.658 44 0.1232 12 0.221 0.0005 0.325 0.147 0.687 53 99 0.1264#1-1 31 0.1163 0.0007 67 54#2-1 0.531 0.215 6.325 0.0006 71 0.072 23 0.1256#3-1 0.1177 195 1.321 0.271 130 0.705 0.0009 0.0008 62#4-1 157 0.425 6.447 0.253 0.1249#5-1 0.054 66 0.1242 0.623 0.0008 36 0.0006 6.245#6-1 122 0.025 51 0.1137 0.508 0.268 139 4.847 4.446#7-1 30 0.347 0.194 133 0.173 0.1106 0.0007 0.365#8-1 25 0.0005 0.250 325 0.142 0.645 0.110 0.0006 6.246 0.172 5.439 90 0.1250#9-1 17 0.445 0.155 0.087 0.129 154 0.1200#9-2 30 0.374 0.0008 8 0.003 6.108 33 0.1280#10-1 51 0.367 0.285 0.376 184 6.081 0.002 0.138 0.1226 0.070 0.0009 0.198 3.261 79#11-1 21 0.278 0.277 0.1171 0.0006 0.865 0.010 50#12-1 44 0.82 43 3.006 0.060 16 0.0007 55 0.008 39 0.1196 0.109#13-1 0.105 0.95 0.361 0.487 0.0006 0.335 0.1107 0.064 24 92 6.077 0.009 22 0.005#14-1 0.0006 120 0.255 0.98 69 2003 4.406#15-1 0.049 0.194 0.355 6 21 0.98 78 0.606 0.0008 0.1288 0.355 90 4.896 0.008 0.200 0.004#16-1 670 0.0009 0.208 4.612 51 0.060 0.97 53 0.94 0.858 29#17-1 0.1254 0.417 2049 3.741 70 0.031 53 12 0.197 0.048 462 0.003#18-1 2018 0.171 64 0.0005 0.006 99 0.191 0.95 0.1080 34 0.92 0.434 5.843 0.004#19-1 108 0.057 11 0.352 1582 1578 0.260 53 2.878 11 0.751 0.0006 0.122 176#20-1 0.044 46 0.266 0.003 0.2451 63 2041 0.83 0.012 193#21-1 0.1306 8 38 0.97 0.277 0.335 1985 0.0010 1864 0.125 133 27 0.174 6.532 70 0.96 0.273 0.002 1371#22-1 0.0708 0.070 43 26 0.957 0.204 26 0.0862 0.232 0.397 0.001 120 6.116 2028#23-1 9 0.89 0.0026 1957 0.009 8 57 0.0008 0.515 1960 0.011 0.105 34 2004#24-1 0.1763 36 0.354 0.119 19 0.812 1218 68 11 3.519 0.003 56 0.71 26 0.0004 0.189 0.282 2048#25-1 0.2211 1900 0.0004 29 0.002 0.125 0.69 17 0.130 0.524 1160 9 21.410 33#26-1 0.0624 14 0.147 39 0.99 0.0866 33 28 98.2 0.0009 25 9 7.132 0.010 0.368 181 2038 0.239#27-1 1921 0.081 0.92 21 0.397 1946 13 0.004 12 47 0.1218 10 48.9 0.0011 1.610#28-1 0.90 0.1269 0.922 1522 0.354 2.844 0.152 17 0.437 22 15 101.0 0.0004 23 2027#29-1 0.1292 1578 0.0005 93 12 12.349 32 2017 0.140 0.98 0.007 24 1.404 100.7 0.1196 0.236 0.311 1555 0.114 9#30-1 1859 12 0.95 0.0007 53 17.920 24 0.021 32 77.2 1343 83.0 0.0008 0.259 0.007#31-1 0.023 0.1337 0.634 48 10 32 1809 7 39 1.418 0.0006 0.874 254#32-1 0.117 54 0.396 0.414 1955 0.98 0.428 0.0006 8 2.895 0.005 0.091 10 20 0.1533 19 16 97.4 1113 2029#33-1 0.204 0.165 0.892 97.0 27 6.306 64 0.1062 15 13 0.98 0.239 0.0006 0.011 102 14 6.261#34-1 0.345 0.419 1957 94 0.007 37 96.6 0.508 0.125 0.007 0.117 2019 6.468 2071 0.1023 0.052 49 0.92 0.1278 0.0007 50 12 18 5.821 1995 69 24 97.2 0.588 65.5 0.002 0.268 133 0.112 0.911 0.0007 1953 0.002 42 1912 0.86 24 0.064 0.313 0.147 7.513 0.1009 0.102 64.1 9 80 10 0.004 0.048 33 0.95 0.2062 0.048 0.0030 0.242 31 1368 0.0005 1950 0.117 0.402 25 8 9.917 0.006 40 1811 0.1275 0.89 95.9 0.375 0.482 0.266 0.79 35 3164 0.358 43 9 4.753 0.095 41 0.1431 0.112 0.0014 0.000 0.86 0.0674 1.176 2150 0.0015 0.363 86 11 0.004 77.8 2082 26 76.2 3.617 0.353 0.111 173 14 6.450 0.157 0.89 0.726 0.0006 0.006 0.150 0.1107 78.0 984 1382 0.003 0.084 2034 44 0.0818 0.957 0.0012 0.408 58 0.56 70.3 2648 0.0003 4.000 0.340 15.165 0.002 34 0.94 0.381 100.3 7 0.132 1766 0.007 0.1526 0.083 0.469 0.230 2980 0.204 0.94 0.0844 61.5 0.0010 6.931 11 0.82 0.325 0.0004 0.282 8 3153 0.006 8 0.699 6.254 0.112 0.1270 0.297 18 0.82 623 1399 0.114 1.310 17 2107 0.256 0.97 0.0010 0.366 0.007 0.069 0.2227 24 2055 97.0 0.0005 0.066 1972 17 4.951 0.005 0.1012 0.96 953 0.208 2.471 1344 0.130 0.288 96.0 0.0006 0.533 1996 11 2618 0.1300 0.040 21 0.006 1949 0.004 3 0.95 0.1260 77.4 0.0012 9.300 2989 29 0.394 2.639 0.097 0.93 14 100.3 0.0009 12 2204 10 0.1148 0.044 0.317 0.007 0.010 10 102.1 0.0006 0.141 8 6.657 1352 0.59 0.95 33 2479 0.0005 18.184 0.240 689 8 0.003 1983 0.046 0.324 1813 2056 103.3 27 0.0006 102.9 0.219 4.082 0.006 0.86 0.93 12 0.004 0.058 2087 1472 101.1 2011 7.012 0.309 1950 31 15 0.442 11 6.732 0.85 0.227 0.006 10 26 99.7 0.004 0.094 2147 0.92 1630 2755 5.632 0.99 0.380 103.5 7 0.081 29 21 0.592 0.011 8 2383 0.079 2142 103.7 0.004 90.5 0.89 1735 0.95 0.292 1775 95.9 7 0.051 35 41 0.003 0.391 850 1666 0.010 2068 0.97 95.6 0.388 100.0 8 15 0.95 1811 12 1277 0.006 30 0.356 102.7 1640 2876 0.85 53 0.004 24 0.95 2360 7 0.004 104.0 1318 2064 27 104.5 0.92 20 26 0.003 12 2265 2077 0.92 2999 49 0.93 88.3 850 20 97.2 9 1811 1654 14 1240 0.85 13 99.4 95.8 2129 38 2111 11 2375 16 1302 103.8 11 31 1962 78.3 2057 19 11 3000 20 100.0 11 100.0 103.0 1647 13 8 2098 9 2043 99.4 101.2 16 1877 101.0 8 8 99.9 100.4 9 101.5 103.4 104.5 Sample SU-1 196 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 ) (1 ± Pb 206 Pb/ 207 ) (1 ± U 238 Pb/ 206 ) Rho Apparent ages (Ma) Conc. (%) (1 ± U 238 Pb/ 206 ) (1 ± U 235 Pb/ 207 ) (1 ± Pb 206 Pb/ 207 Pb 206 Pb/ 208 ) Continued #35-1#36-1 20#37-1 88#38-1 10#39-1 15#40-1 98 18#41-1 185 79#42-1 85 44#43-1 31 10#44-1 44 36 194 37#45-1 103 15#46-1 111 58 46#47-1 30 56 82 0.406 257 0.951#48-1 94 169 45#48-2 0.123 66 0.282 121 18 0.754#49-1 50 80 0.320#50-1 0.230 86 13 0.142 74 0.612#51-1 106 0.090 82 0.1352 6 0.040 0.1278 0.917#52-1 114 35 12 0.177 106#53-1 0.255 64 0.0707 3 0.952 123#54-1 49 182 26 0.1529 0.553 0.0008#55-1 0.0006 0.279 0.1250 73 146 0.499 0.1318 111#56-1 0.161 0.751 1 13 7.749 0.0005 6.513 119 0.2045#57-1 0.143 53 0.602 0.0010 0.219 0.583#58-1 60 16 7 0.0006 56 1.522 0.1009 0.178 0.780 0.0006 134 70 0.171 0.065 0.099 131 9.654 0.1352 0.0010 38 6.468 25 0.540 0.224 0.1336 7.290 0.416 0.370 0.1213 15.471 0.025 18 0.427 0.0006 0.151 111 13 0.1341 144 0.123 20 0.0007 0.1564 277 0.085 288 0.156 0.140 0.076 0.014 4.168 0.497 0.0009 0.1287 0.458 0.210 0.002 0.005 0.0006 0.375 7.508 152 0.401 0.003 0.155 0.1280 0.504 0.0007 0.492 0.549 7.473 0.70 0.95 0.929 0.0006 0.002 6.130 36 106 0.474 0.065 0.0816 0.145 0.0006 0.145 0.005 2241 7.364 2028 0.271 0.182 0.005 0.90 9.482 0.139 0.300 0.004 0.118 0.0006 0.135 0.0738 0.1356 0.85 0.007 6.783 0.086 0.403 0.94 935 0.576 0.0006 0.038 0.91 2.719 0.104 0.406 2431 6.699 0.1354 0.94 0.108 0.366 11 0.0831 25 2054 0.1309 0.004 0.159 2174 0.788 0.1258 0.105 0.398 0.0006 2.288 0.0014 2820 0.440 0.010 0.94 0.106 13 0.382 0.007 2167 0.1209 2067 0.0007 22 1.795 0.0012 7.610 0.005 0.98 0.0006 22 1690 0.036 0.0005 0.380 17 0.005 0.93 0.1322 0.1282 29 2181 0.005 7.213 0.94 2.517 7.262 0.203 949 2378 2195 0.006 0.94 0.033 0.0006 6.157 0.149 10 2029 2013 0.93 8 2123 22 0.006 2161 0.0009 0.95 2862 0.0006 0.177 0.118 0.407 5.626 0.058 2349 0.074 44 0.060 0.003 0.96 2087 14 12 103.4 0.387 31 7.314 6.886 0.220 0.402 23 1640 8 98.1 0.355 0.88 2074 0.046 8 0.003 24 0.007 2167 8 21 2146 1193 0.099 0.083 102.2 0.338 0.90 26 0.006 0.85 1976 98.5 0.004 0.004 10 101.2 2152 0.003 0.401 102.4 0.389 27 1048 2201 0.95 2417 0.77 0.90 8 98.5 2080 0.90 12 15 0.002 2107 1279 2180 8 103.0 2071 1958 0.005 0.004 0.81 8 16 31 100.7 7 1237 102.3 0.87 1875 0.92 8 28 20 101.9 17 1035 2172 15 2175 2120 8 100.4 15 97.2 2169 100.4 1273 11 2110 2040 16 18 100.1 22 20 1969 96.5 28 9 8 2127 2074 101.2 101.3 7 100.5 9 97.1 103.3 12 9 96.0 95.2 102.2 102.2 #1-1#1-2 29#2-1 24#3-1 23#4-1 10#5-1 11#6-1 78 15#7-1 68 101 35#8-1#9-1 32 4 77 23#10-1 25 65 26#11-1 40 59 31#12-1 78 12 25#13-1 1.005 18 31 0#14-1 61 1.046 27 0.285 42 1.712#15-1 45 108 13 37 0.294#16-1 1.269 0.526 38 27#17-1 0.792 13 55 40 0.356 61#18-1 0.1054 0.955 18 83 0.226 63 0.719#19-1 0.1056 75 10 21 0.275 0.1000#20-1 0.211 33 14 26#21-1 0.010 0.1061 1.008 0.0004 45 11 34#22-1 0.1067 0.708 0.0005 68 13 41 0.004 0.280 0.486 0.0005#23-1 4.547 0.1049 45 13 35 0.200 0.1050 0.813#24-1 4.622 0.0006 0.136 96 22 61 4.114 1.219 0.0006 0.225 37 12 34 1.209 0.076 0.0601 4.549 0.1052 0.0005 0.343 54 38 0.465 0.0005 0.072 4.356 0.1313 0.346 29 0.077 43 0.313 0.1306 0.272 4.502 0.148 33 64 0.317 4.201 0.1051 0.936 0.093 0.298 0.0005 0.0005 0.075 27 41 0.1054 0.756 0.093 0.0008 0.266 34 0.311 0.005 0.1055 1.234 0.0005 0.105 0.808 4.575 0.216 34 0.075 0.296 0.005 0.1045 1.871 0.0006 0.005 6.904 0.97 0.342 59 0.311 7.186 0.1302 1.279 0.0006 0.290 0.96 0.530 34 0.006 1755 4.615 0.1055 0.97 1.109 0.0005 0.017 0.087 0.363 0.006 1777 4.618 0.1010 1.248 0.0009 0.235 0.96 1683 0.312 0.097 0.157 0.315 0.007 4.552 0.1052 1.084 0.0005 0.005 0.97 0.340 0.099 0.381 1745 3.763 0.1026 1.207 0.0005 0.399 25 0.98 0.290 0.101 1672 6.963 0.1051 0.96 0.0005 0.319 23 0.336 0.100 0.002 27 0.006 1746 4.564 0.1052 0.0007 0.318 1642 0.068 0.013 1721 4.208 0.1045 0.0005 0.313 30 0.90 0.009 0.96 0.162 1725 4.224 0.1053 0.0011 0.261 30 0.007 0.98 1624 0.075 1767 4.323 0.0996 0.98 0.0009 0.388 35 600 0.007 0.092 25 1734 2082 4.578 0.97 0.0006 0.314 0.007 2165 8 0.104 1744 4.497 0.97 0.0005 0.302 0.004 1783 8 0.097 1713 4.318 0.98 0.0010 8 0.291 28 0.009 1714 1779 11 0.077 4.634 0.87 10 0.305 59 0.005 1755 0.104 102.0 39 3.911 0.98 0.316 0.006 1495 9 0.099 103.0 32 1718 0.96 103.6 0.310 0.007 2113 9 0.112 608 33 2116 0.97 9 100.7 0.300 0.007 2106 1759 0.132 33 0.96 0.319 0.004 1716 1702 21 0.97 95.9 0.285 0.007 1721 1647 9 101.9 41 19 0.80 10 0.007 1723 1718 95.8 24 0.93 7 0.008 1706 1770 10 32 0.97 0.009 2101 1741 10 102.9 34 0.98 1723 1690 98.7 98.4 33 0.96 8 102.8 1643 1786 17 103.9 21 1718 1615 103.3 33 7 1673 33 9 101.9 1716 37 9 87.6 1717 12 46 100.6 1706 9 102.1 1720 18 103.6 1617 15 95.9 10 102.7 103.1 9 18 101.4 99.1 103.8 99.9 Sample RU-1 Sample Pb* (ppm) Th (ppm) U (ppm) Th/U Rio Una Complex Table 1 ( S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 197 #25-1#26-1#27-1 12#28-1 15#28-2#29-1 4 41 14#30-1 51 17#31-1 13#31-2 34 1 23#32-1 7 37 15#33-1 8 32#34-1 6 1.207 55 34 48 19#35-1 1.387 43 13 36#36-1 34 41 0.336 22#37-1 0.025 0.672 87 21 0.385#38-1 5 0.350 35 23 20#39-1 100 0.922 0.0996 10 0.018 14 0.164 105#40-1 0.1048 0.945 0.096 12#41-1 8 36 111 58 1.856 0.265#42-1 8 0.0010 0.0637 0.1339 15 1.559 0.827 8#43-1 0.0006 0.257 0.1338 44 13 23#44-1 0.977 0.908 0.520 65 0.1060 17 22#45-1 0.0014 0.0006 0.420 3.933 0.235 14 23 26#46-1 0.1054 140 0.0006 4.451 18 0.934 24 0.278 0.256#47-1 0.1027 0.894 0.0009 27 12 26#48-1 0.1016 0.132 0.1338 0.726 35 7.318 122 55 0.314 0.0011#49-1 8 0.101 0.258 7.142 58 0.1011 37 0.966 0.1054 0.0006 0.262#50-1 82 4.542 29 20 0.835 0.0008 0.286 0.0005 0.021#51-1 0.151 0.405 1.151 0.085 60 35 0.308 4.313#52-1 0.1020 0.149 0.0006 0.275 45 0.0004 1 77 0.1050 10 4.335#53-1 0.103 0.330 0.309 75 0.009 48 14 0.083 0.396 4.179 0.114 7.000 0.327#53-2 0.1315 0.921 0.007 41 0.116 0.0008 0.387 100 110#54-1 0.0998 4 1.290 0.0004 4.210 4.539 0.074 30 0.311 0.153 7#55-1 0.1025 0.96 0.381 0.001 57 0.008 29 0.067 0.1350 57 0.119 0.1003 0.0008 0.259#56-1 0.96 0.297 82 0.008 0.013 0.0009 0.701 4.266 0.360 108 6 0.092 0.085 0.306 8 4.447 0.007 0.0874 19 0.0009 24 1623 0.245 0.62 0.98 0.298 0.858 0.0007 0.379 41 0.0006 0.1052#1-1 26 1731 7.189 0.007 4 0.98 0.497 0.003 0.207 0.084 0.1050#2-1 0.302 3.959 0.313 0.005 83 19 0.071 0.93 28 0.0005 61 0.0853#3-1 0.308 46 2152 4.703 0.004 0.240 0.006 512 0.710 0.0005 627 7.630 24 4.009 0.142 0.92#4-1 91 33 2109 0.137 0.0609 0.1040 0.303 0.0005 0.006 0.097 0.006 0.94#5-1 13 0.307 1.311 17 1744 0.275 0.0018 0.087 51 2.410 0.116 1617 0.88 0.1053#6-1 78 37 0.98 0.197 137 0.148 0.091 0.397 0.007 1676 63 4.528 9 1711 0.1316#7-1 44 36 0.0012 0.0005 0.006 0.97 0.288 0.98 1721 4.424 0.005 0.379 40#8-1 19 1.086 32 0.182 18 0.1319 111 0.068 0.333 1.202 1682 0.0006 2074 2.003 223 2150 0.1045#9-1 36 0.410 0.290 0.007 0.002 11 0.083 36 0.384 0.0005 68 2148 0.92#10-1 24 732 1701 0.721 0.007 1753 4.360 0.099 24 0.97 0.1037 0.333 33 0.0880 194 63 1732#11-1 48 0.0007 0.200 100.4 0.008 0.354 0.177 21 29 0.0006 0.615 8 4.507 0.008 47 0.006 0.95 0.0591#12-1 22 0.312 101.2 0.103 191 1721 47 65 1708 7.133 8 69 0.024 0.93#13-1 0.125 31 0.306 28 1727 0.0004 111 15 1674 0.1039 141 0.0030 49 1.208 0.573 0.005 0.93 0.1049 0.170 138 7.120 1654 0.180 0.110 2148 0.97 0.97 2153 100.1 0.0002 81 19 4.434 0.006 22 0.1304 215 0.358 0.142 27 21 0.086 1630 0.304 77 11 0.007 103 70.0 1645 1720 23 98.2 0.0008 0.569 100.7 0.361 4.201 0.183 37 0.98 357 1851 0.0005 1.539 14 0.015 0.172 0.1258 0.311 2214 1641 7 160 0.166 34 0.97 0.585 0.0005 49 0.819 0.106 97.4 0.393 0.002 10 1661 0.009 16 33 0.98 0.898 102.8 1.367 0.169 179 7 1714 285 0.1005 0.075 0.1293 1175 4.343 0.060 37 0.97 0.391 101.7 4.361 0.0004 0.007 35 0.308 32 1751 1.339 0.168 2118 0.013 0.0829 0.455 96.5 6.953 14 0.008 0.82 0.98 1720 103.4 0.273 49 1621 0.382 0.0702 0.0005 0.294 0.209 101.9 0.0005 7 1.251 0.081 0.127 29 1014 0.009 1670 0.080 0.98 11 0.011 6.230 2164 0.386 0.1306 1630 27 0.101 0.0003 0.131 0.153 0.98 102.8 1711 17 0.0986 33 0.1283 532 0.335 0.0004 0.005 0.063 0.376 0.303 100.8 0.003 16 4.144 6.132 1369 0.98 80 0.302 1743 11 0.99 0.148 101.7 0.1108 0.0005 9 0.002 1718 0.1329 0.387 2138 2.532 42 100.6 0.0006 0.0005 0.097 1714 14 0.98 0.0960 0.1273 0.005 11 1.537 0.51 0.052 0.044 2129 110.8 0.005 1322 36 1729 0.359 100.7 0.0004 0.98 102.3 0.0006 9 6.923 0.008 0.029 36 1697 0.1328 1660 9 0.0003 3.737 0.0004 6.406 0.90 0.020 0.299 635 0.344 40 43 0.96 770 85.8 1719 0.008 56 4.899 0.051 0.98 101.9 617 0.221 7.269 2119 0.0007 9 0.109 0.132 26 1707 100.4 40 0.159 0.003 3.462 0.002 6.298 1699 10 2124 15 76.7 0.99 1706 0.084 0.384 2108 0.002 0.083 6 9 0.275 100.8 0.362 7.310 0.002 1692 25 0.93 0.067 0.86 0.069 83.7 26 101.4 9 1383 1978 10 0.321 0.002 39 0.95 0.397 100.9 0.008 0.007 0.113 0.90 1686 572 0.262 1905 7 1695 0.359 63 1712 100.2 40 101.3 0.005 0.86 1290 0.004 2103 0.98 0.98 0.399 15 0.005 0.004 17 7 10 951 10 98.1 55.7 2040 0.98 2097 0.92 13 7 1566 1992 0.006 100.7 0.98 0.95 1634 108.0 2089 10 99.2 1793 6 11 2154 1267 100.2 39 0.95 35 1498 1977 9 6 933 26 2107 19 97.0 7 2165 1598 2075 26 18 103.2 11 91.2 1812 7 2136 101.7 12 27 7 1547 2061 101.9 6 8 99.5 2136 98.0 6 6 96.0 100.9 99.0 9 96.8 95.9 101.4 Sample RU-2 198 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 ) (1 ± Pb 206 Pb/ 207 ) (1 ± U 238 Pb/ 206 ) Rho Apparent ages (Ma) Conc. (%) (1 ± U 238 Pb/ 206 ) (1 ± U 235 Pb/ 207 ) (1 ± Pb 206 Pb/ 207 Pb 206 Pb/ 208 ) Continued #14-1#15-1 48#16-1 49#17-1 14#18-1 16#19-1 71 76#20-1 49 87#21-1 17 16#22-1 39 138#23-1 8 73 81 115#24-1 52 50#25-1 31 64 37#26-1 46 0.547 69 92 227 119#27-1 0.754 64 0.170#28-1 129 71 70 0.494 0.215#29-1 152 52 93#30-1 112 0.087 0.147 90 31 0.357 122#31-1 71 0.1207 28 119 0.090 0.700 0.108#32-1 101 0.1273 19 150 0.707 106#33-1 0.200 105 88 0.1320 0.771#34-1 0.219 20 0.524 0.0005 307 1.087#35-1 1 0.1031 0.226 0.1001 17 0.0004 216 34 0.145 1.014#36-1 5.030 67 0.337 47 141 0.2184 0.0007 225 1.068#37-1 6.492 79 0.287 0.1052 0.231#38-1 0.0013 249 46 0.0004 0.308 61 7.173 0.1286 233 0.468#39-1 0.041 0.2023 17 0.066 22 0.0009 0.1267#40-1 154 0.112 237 2.360 4.033 57 51 0.392 0.138 0.302 0.0006 0.1147#41-1 16.365 33 0.099 87 0.370 0.004 0.0007 0.114 0.1207#42-1 43 14 0.145 0.0011 18 4.585 0.1266#43-1 0.038 0.0005 0.052 0.394 0.017 40 47 140 0.915 60 6.707 0.002 0.831 0.084 14.704 0.1238#44-1 0.0003 0.139 116 30 0.166 0.292 0.006 6.197 150#45-1 0.0005 0.254 0.244 0.1290 39 0.86 0.115 26 0.543 1.411 5.666 369#46-1 0.0005 0.005 0.98 41 0.107 47 0.261 0.0743 0.553 1702 5.868 1.692#47-1 0.0005 0.316 0.402 50 0.0719 64 317 56 0.148 0.002 0.004 0.92 2028 6.294#48-1 0.378 0.527 0.156 82 0.577 0.0004 0.562 0.2002 63 0.058 0.004 0.1006 5.147 303#49-1 0.355 0.64 2142 11 0.96 0.048 50 0.056 0.0011 0.165#50-1 0.358 10 0.008 6.849 40 38 0.87 0.0004 69 0.035 0.1214 1.194 1653 0.044 0.365 0.353 30 990 0.006 0.009 90 29 0.0008 49 0.074 1.319 0.1337 0.97 0.0004 2798 0.1247 180 0.361 0.347 0.008 1.172 70 0.085 0.119 23 0.94 1967 0.95 14.601 0.082 0.302 1771 0.003 97 0.1604 35 4.001 1.179 2062 0.0006 0.057 0.99 18 2068 0.003 91 0.0975 2729 0.025 35 10 0.385 0.616 0.0006 125 0.96 0.0005 0.012 17 2125 0.338 0.002 1958 231 77 0.114 5.835 0.0999 0.910 0.0698 0.92 0.129 0.179 0.004 1974 0.0006 0.070 7 0.118 38 7.036 0.518 1626 5.773 0.76 1681 0.529 0.259 31 0.0716 1947 0.0006 6 27 37 0.004 0.761 2969 0.96 0.289 0.154 9.894 83 0.394 1985 0.073 40 0.1012 0.0005 0.782 0.0003 9 0.001 1718 0.225 1.749 60 0.97 1699 0.142 0.068 17 0.001 0.1530 0.105 86.5 0.348 2079 2845 0.0028 23 0.236 0.003 7 15 3.535 0.1275 0.58 1.106 2100 1.472 0.083 98.4 0.382 0.336 0.005 0.88 2052 7 0.1219 0.422 0.0004 0.85 0.034 100.8 7 0.331 1.049 1875 10 0.447 21 781 0.1291 0.97 1.270 0.0008 0.004 720 0.124 0.1766 1966 0.070 2737 0.009 101.7 0.130 4.057 0.0005 0.1046 58.9 9 9 21 0.008 1634 0.362 0.004 9.393 0.93 2051 0.0005 0.042 7 94.2 0.256 0.153 2011 103.1 0.003 6.476 0.1005 0.97 0.0005 0.93 5 1927 0.0009 0.057 8 0.106 6.001 0.002 0.1344 2085 15 0.0007 7 6 2084 0.88 1866 0.121 99.5 95.9 24 6.750 0.1217 11.028 0.291 0.005 0.001 0.95 0.092 6 95.4 2384 0.0005 4.343 7 0.445 105.3 1049 2828 0.040 19 0.001 0.96 0.0009 0.72 0.368 983 1634 789 0.088 5 0.074 99.0 35 18 4.073 0.0006 0.357 0.004 1472 0.30 0.065 7.622 917 96.8 0.379 0.453 15 0.005 1978 31 84.5 6.090 0.96 7 0.301 0.005 2147 650 2025 10 0.039 100.7 14 0.92 7 0.002 1645 0.064 25 0.96 2460 0.294 0.005 2374 0.002 0.047 4 0.74 8 74.4 0.411 1576 2021 0.004 96.8 0.96 0.60 8 73.3 8 100.0 0.363 7 1623 1969 20 0.89 0.002 2073 2408 7 23 922 0.002 1696 97.5 12 24 0.86 975 0.002 1646 97.0 10 92.1 0.60 8 2380 1662 22 0.77 96.9 8 2064 2221 9 20 50.1 1997 76 1984 8 90.7 2085 12 2622 9 1708 99.5 7 9 10 66.7 1633 8 99.9 7 99.8 9 13 2156 1981 97.9 99.2 9 99.4 12 91.8 99.3 9 101.8 103.0 100.8 Sample Pb* (ppm) Th (ppm) U (ppm) Th/U Table 1 ( S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 199

Fig. 4. U–Pb concordia diagrams (a and c) and probability plots (b and d) for zircons from samples of the Sertânia Complex. (a and b) Sample VAN-2. (c and d) Sample SE-1.

local sources. In contrast, rocks with U/Pb ages in the interval 5.2. Surubim Complex 1.97–1.87 Ga have not been described anywhere in the Borborema Province, suggesting distal sources for detrital zircons with these Similarly to sample VAN-2 of the Sertânia Complex, only zir- ages. con grains with Paleoproterozoic ages were obtained from sample In contrast with sample VAN-2, sample SE-1 is dominated by a CIV-54 (Fig. 5a and b). Of the 21 analysis within ±5% of con- large population of latest Mesoproterozoic to Neoproterozoic zir- cordia, seventeen have ages ranging from 2004 Ma to 2071 Ma. con grains (Fig. 4c and d). The youngest analysis (#37-1) provides The four other grains yielded ages of 1999 ± 22 Ma, 1950 ± 22 Ma, a maximum age of deposition of 642 ± 26 Ma, implying a rather 1921 ± 18 Ma and 1838 ± 38 Ma, the latter constraining the max- short time interval between sedimentation and metamorphism, imum possible age of deposition. Discordant zircons (Fig. 5a) which peaked between 630 Ma and 610 Ma in the study region indicate lead loss, which is attributed to disturbance due to the (Neves et al., 2006a). The five grains with ages younger than 700 Ma strong mylonitization underwent by the rock during the Brasiliano are equant, subhedral crystals whereas older grains tend to be event. However, overgrowths present in some grains were too thin elongated (length to width ratio up to 4:1) with rounded termi- to be analyzed in order to better constrain the age of mylonitization. nations. Age clusters are observed at 700–775 Ma, 810–875 Ma and Zircon grains from sample SU-1 show a large spread of U–Pb 930–970 Ma (Fig. 4d). A minor population is represented by Paleo- ages, ranging from the Archean to the Neoproterozoic (Fig. 5c and proterozoic zircon grains showing a spread of ages between 1.77 Ga d). The dominant population consists of grains with ages ranging and 2.47 Ga. A late Archean grain with an age of 2625 ± 16 Ma from 1950 Ma to 2170 Ma, with age peaks at ≈1.98 Ga, 2.08 Ga and (analysis #13-1 in Table 1) was also found, which, together 2.15 Ga (Fig. 5d). Of the four Archean grains, analysis #9-1, with with analysis #60-1 (207Pb/206Pb minimum age of 2800 ± 10 Ma; an age of 2989 ± 16 Ma, has an overgrowth that yielded an age of Table 1), indicates a weak contribution from an Archean 623 ± 6Ma (Fig. 5d). The low Th/U (0.012) of this overgrowth is source. consistent with a metamorphic growth, and since the analysis over- 200 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205

Fig. 5. U–Pb concordia diagrams (a and c) and probability plots (b and d) for zircons from samples of the Surubim Complex. (a and b) Sample CIV-54. (c and d) Sample SU-1. laps concordia at the 2 level, it is interpreted as constraining the tion is reinforced by the 617 ± 18 Ma age of an overgrowth around a age of peak metamorphism. The three other Neoproterozoic ages 1692 ± 14 Ma Paleoproterozoic grain (#53-1 and #53-2 in Table 1). are from elongated grains (length to width ratio around 3) with This age is also similar to the crystallization age (606 ± 8 Ma) of the subhedral outlines and high Th/U ratios, indicating provenance protolith of the Jupi orthogneiss, which is inferred to have been from (meta)igneous sources and an age of deposition younger intruded and deformed during development of the regional flat- than 850 Ma (Fig. 5d). These data confirm the Neoproterozoic age lying foliation (Neves et al., 2008). of the Surubim Complex, which, according to a previous study Sample RU-2 shows a spread of zircon ages from the early Neo- (Neves et al., 2006a), must be younger than 665 Ma. Several other proterozoic to the Neoarchean (Fig. 6c and d). Grains within the small age groups are observed, including distinctive clusters of age intervals 1626–1646 Ma, 1966–1984 Ma, 2050–2085 Ma and late Paleoproterozoic (1640–1735 Ma) and mid-Mesoproterozoic 2100–2160 Ma are dominant (Fig. 6d). The ages of the youngest (1240–1350 Ma) ages. analyzed grains (917 ± 8 Ma and 951 ± 20 Ma; Fig. 6c) provide a maximum age for deposition of the sediments. 5.3. Rio Una Complex 6. Discussion Concordant grains from sample RU-1 fall within two narrowly defined time intervals (Fig. 6a and b): 1.62–1.74 Ga (41 analyses) 6.1. Are the Sertânia and Surubim complexes different and 2.10–2.16 Ga (11 analyses). The first population clearly shows lithostratigraphic units? that deposition of the detritus occurred well after the Transama- zonian event. Both groups are dominated by elongated grains with Differences on deposition ages of supracrustal units in the Cen- rounded corners and high Th/U ratios. One concordant grain (#7- tral Domain was one of the main arguments in support of the 1) with a low Th/U ratio yielded an age of 600 ± 22 Ma (Fig. 6a), terrane accretion hypothesis proposed for the Borborema Province which is interpreted as the age of metamorphism. This interpreta- (Santos et al., 1999, 2004a; Brito Neves et al., 2000). Santos et al. S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 201

Fig. 6. U–Pb concordia diagrams (a and c) and probability plots (b and d) for zircons from samples of the Rio Una Complex. (a and b) Sample RU-1. (c and d) Sample RU-2.

(2004a) inferred that sedimentation of the Sertânia Complex was preexisting continuous substrate, not into two separate crustal contemporaneous with formation of the orthogneiss basement, a blocks. This latter inference is based on the ages of uncovered contention not supported by the age of the youngest grain present orthogneisses (Santos, 1995; Brito Neves et al., 2001; Melo et al., in sample VAN-02 (1871 ± 20 Ma), indicating post-Transamazonian 2002; Santos et al., 2004a,b; Neves et al., 2004, 2006a), the presence deposition, and by the dominance of Neoproterozoic zircons in of Paleoproterozoic xenocrystic zircons in Brasiliano granitoids sample SE-1 (Fig. 4), The similarity in age distributions of sam- (Neves et al., 2006a), and Paleoproterozoic Sm–Nd model ages of ples VAN-2 and SE-1 of the Sertânia Complex with, respectively, Brasiliano granitic and syenitic plutons (Neves et al., 2000; Mariano samples CIV-54 (this study) and SCC-9 (Neves et al., 2006a)ofthe et al., 2001; Guimarães et al., 2004). Surubim Complex suggests differences in provenance of the clastic material, not in deposition age. Therefore, the most likely hypothe- 6.2. Rio Una Complex sis is that the Sertânia and Surubim complexes are part of the same sedimentary package. Two interpretations can be proposed for the Rio Una Complex. The above conclusion is supported by several other lines of First, the zircon age distribution could be taken as evidence that it is evidence. First, there is no recognizable regional unconformity correlative with the Sertânia and Surubim complexes. In this case, between the two complexes. Second, the overall similarity in rock the lack of zircons younger than 900 Ma would result from their type association, metamorphic grade, and in major and trace ele- absence in the analyzed samples (as it was the case for samples ment geochemistry (Neves and Alcantara, 2009) suggests that they VAN-2 and CIV-54 of the Sertânia and Surubim complexes, respec- are correlated. Third, marbles of the two complexes yielded similar tively), but not in the entire sequence. The second hypothesis is carbon isotope signatures, characterized by a large range in ␦13C that the Rio Una Complex is older than the two other studied com- from0to8‰pdb (Santos et al., 2002). Finally, extensive Paleopro- plexes (but certainly not Paleoproterozoic, as proposed by Osako terozoic crust of ∼2.15–1.97 Ga age, either exposed or underlying et al., 2006 and Da Silva Filho et al., 2007), and a correlation could the Sertânia and Surubim complexes, argues for deposition in a be sought with the early Neoproterozoic Riacho Gravatá Complex 202 S.P. Neves et al. / Precambrian Research 175 (2009) 187–205

regions in the Amazonian and São Francisco/Congo cratons are also considered.

6.3.1. Archean sources A few Archean grains have been found amongst the analyzed zir- cons. Archean gneisses are present in the northeastern most part of the Borborema Province (Dantas et al., 2004), in the basement of the Ceará belt (Arthaud et al., 2008) and in two domes wrapped by metasediments of the southern Sergipano Belt (Oliveira, 2008). Sources in the Central Amazonian Province of the Amazonian Cra- ton and in the São Francisco Craton are also possible. Because rocks with Archean ages have not been found in the Central Domain these Archean grains may be derived from erosion of relatively dis- tal sources or second-order zircons recycled from the erosion of preexisting sedimentary rocks.

6.3.2. Paleoproterozoic sources Early Paleoproterozoic (2.5–2.3 Ga) ages have been obtained on zircon grains from samples of the three analyzed complexes (Fig. 7): seven in the Sertânia Complex, four in the Surubim Complex, and two in the Rio Una Complex (Table 1). Until recently, rocks within this age range were unknown in western Gondwana but they are becoming increasingly common. The granulitic basement of the Médio Coreaú domain (Fetter et al., 2000; Santos et al., 2008a) constitutes the most extensive early Paleoproterozoic unit in the Borborema Province, but 2.4 Ga-old tonalitic orthogneisses were also found in the basement of the Alto Moxotó belt (Brito Neves et al., 2001; Melo et al., 2002). In the Amazonian Craton, early Paleo- proterozoic rocks are common in the Bacajá domain (Vasquez et al., 2008) and minor occurrences are found in the Amapá block (Rosa-Costa et al., 2006). Following an apparent gap at 2.30–2.22 Ga, prominent peaks in the relative cumulative-probability plots are observed in the time span 2.20–2.02 Ga in the three complexes (Fig. 7). Rocks with these ages are so widespread in western Gondwana 207 206 Fig. 7. Relative cumulative-probability diagrams for <5% discordant Pb/ Pb (corresponding to the Transamazonian/Eburnean orogeny) that ages of detrital zircons from the Sertânia (a), Surubim (b) and Rio Una (c) complexes. sourcing the detrital zircon grains to any particular geographical region is impossible. However, rocks whose ages are coincident with younger Paleoproterozoic age peaks have more restricted (Kozuch, 2003; Medeiros, 2004) of the Alto Pajeú belt. Data from occurrences: additional samples are required to choose between these possibil- ities. (a) 2.02–1.93 Ga. A few rocks with ages between 2.02 Ga and 1.97 Ga have been dated in the Borborema Province (Sá et al., 6.3. Provenance 2002; Neves et al., 2006a) but they are only widespread in the Tapajós Province of the Amazonian Craton (Santos et al., 2004b; Analyses of detrital zircon ages for samples of the Sertânia, Almeida et al., 2007). Rocks with well-known 1.95–1.93 Ga ages Surubim and Rio Una complexes have been combined to give are only known in this portion of the Amazonian Craton and a pool of zircons with the total relative cumulative-probability correspond to late to post-orogenic charnockitic plutons (Fraga plots shown in Fig. 7. Only <5% discordant detrital zircon ages et al., 2009); were considered and, for the Surubim Complex, the age spectrum (b) ∼1.88 Ga. This period coincides with emplacement of rapakivi of sample SCC-9 (Neves et al., 2006a) was also included. Com- granites and extensive volcanic successions in the Amazonian mon to the three sequences are several prominent age peaks in Craton (Dall’Agnol et al., 1999; Lamarão et al., 2002). No rocks the interval 1.93–2.2 Ga, and smaller peaks at 0.92–0.98, showing of this age are known in the Borborema Province; the important input from mid-Paleoproterozoic and early Neopro- (c) 1.8–1.7 Ga. Late Paleoproteorozoic ages in this time interval terozoic source rocks. Late Paleoproterozoic and Mesoproterozoic match those associated with crustal thinning and rifting events zircons are also common in the samples of the Surubim and in the Borborema Province (Orós and Jaguaribe belts; Sá et al., Rio Una complexes. In addition, the Sertânia and Surubim com- 1995) and in the São Francisco Craton (Espinhac¸ o rift; Martins- plexes are also characterized by the presence of a large number Neto et al., 2001; Pedreira and De Waele, 2008), with intrusion of 0.9–0.7 Ga-old Neoproterozoic zircons. Therefore, the relative of intraplate anorthosites and granites in the central domain of cumulative-probability plots (Fig. 7) indicate a variety of source the Borborema Province (Accioly et al., 2000), and with intru- regions. Some of these can readily be correlated with rocks formed sion of granitoids of uncertain tectonic affinity in the Tapajós during geological events of known age in the Borborema Province, Province (Almeida et al., 2008); but others do not. In this latter case, they may either correspond to (d) 1.7–1.6 Ga. The significant zircon population with these ages sources not yet identified in the Borborema Province, which is pos- found in the two samples of the Rio Una Complex (and, sible but unlikely to explain all the different age peaks observed, or less commonly, in sample SU-1 of the Surubim Complex) is to more distal sources. Therefore, in the following, possible source contemporaneous to the last orogenic event in the Rondônia- S.P. Neves et al. / Precambrian Research 175 (2009) 187–205 203

Juruena Province of the Amazonian Craton (Santos et al., must have been continuous with the Borborema Province during 2008). the Neoproterozoic. This proposition is in stark contrast with the recent suggestion that the Amazonian Craton became part of west- 6.3.3. Mesoproterozoic sources ern Gondwana only ∼525 Ma ago (Trindade et al., 2006). This latter Samples of the Surubim and Rio Una complexes yielded proposition, however, was based on a paleomagnetic pole obtained some zircon grains with ages comprised between 1.4 and 1.1 Ga in cap carbonates from the Paraguay belt (Trindade et al., 2003), not (Figs. 5–7). Mesoproterozoic events within this time range are in the Amazonian Craton itself and, thus, cannot be taken as firm unknown in the Borborema Province and São Francisco Craton. The evidence for its former paleogeographical position. possible provenance of these detrital zircons is limited in western The above observations suggest that the Neoproterozic Gondwana to the Sunsás Province of the Amazonian Craton, where supracrustal successions of the Borborema Province may be rem- four periods of orogenic activity have been identified: 1.46–1.43 Ga, nants of a much larger sedimentary cover deposited in a regionally 1.37–1.32 Ga, ∼1.27 Ga, and 1.18–1.11 Ga (Santos et al., 2008). The extensive intracratonic basin, with deposition ending shortly ages of the three younger events coincide with those obtained in before the Brasiliano orogeny. Broad-scale lithosphere extension, the present study and in a sample of the Surubim Complex dated soon followed by compression, may provide an explanation for the by Neves et al. (2006a). overall medium- to high-temperature metamorphism observed in the Borborema Province, since thermal gradients resulting from 6.3.4. Neoproterozoic sources crustal thinning can be maintained in the subsequent contractional Felsic volcanic rocks and granites related to the Cariris Velhos phase (Thompson, 1989; De Yoreo et al., 1991; Thompson et al., event (now metavolcanics and orthogneisses; Brito Neves et al., 2001). In the light of the present results, the extension–contraction 1995; Kozuch, 2003; Santos et al., in press) constitute likely sources model of continental deformation shown in Fig. 1b is considered for zircons with latest Mesoproterozoic to early Neoproterozoic the most appropriate to explain the late Neoproterozoic evolution ages found in samples of the three complexes (Fig. 7). This period of the Borborema Province. is characterized by widespread rifting in other places of the Bor- borema Province (Sergipano belt; Carvalho et al., 2005) and in the 7. Conclusion São Francisco/Congo Craton (Tack et al., 2001; Silva et al., 2008), which could also constitute potential source regions. Several mid- Detrital zircons in samples of the Sertânia, Surubim and Rio Neoproterozoic sources can also be considered for the youngest Una complexes indicate provenance from diverse source rocks, detrital zircons found in samples SE-1 and SCC-9 of the Sertânia whose ages vary from the Archean to the Neoproterozoic. The sam- and Surubim complexes. These include 730–700 Ma-old syenites ples display a dominant composite peak at 1.95–2.15 Ga, a minor attributed to anorogenic magmatic activity in the São Francisco Cra- peak at ∼1000–930 Ma, and, in samples of the Sertânia and Suru- ton (Rosa et al., 2007), orogenic magmatic rocks from the Brasília bim complexes, another prominent composite peak at 870–680 Ma. belt, in the western margin of the São Francisco Craton (Pimentel Provenance from local sources could explain part of the age peaks et al., 1999; Laux et al., 2005), and magmatic episodes preceding observed in the relative cumulative-probability plots. However, and coeval with basin formation in the Borborema Province. some of these, particularly late Paleoproterozoic and Mesoprotero- zoic peaks, do not have equivalents within the Borborema Province, 6.4. Implications suggesting more distal sources, possibly located in the Amazonian Craton. The youngest detrital zircon grains in the Surubim and The results of this study show that deposition of the Sertânia, Sertânia complexes indicate deposition at most a few tens of mil- Surubim and, possibly, Rio Una complexes occurred in the late Neo- lions of years before the onset of the Brasiliano orogeny, whereas proterozoic. As previously noted by Neves et al. (2006a), there are neoformed zircons and zircon overgrowths in the Surubim and Rio striking similarities between the Surubim Complex and the Seridó Una complexes indicate peak metamorphism at 630–600 Ma. The Group in the northern domain, whose deposition age is younger results of this study do not support the contention that the dated than 650 Ma (Van Schmus et al., 2003). Equally, detrital zircons in complexes belong to distinct tectonostratigraphic terranes. Instead, the Ceará belt imply deposition after 770–750 Ma (Arthaud, 2007), they argue for deposition in a laterally continuous basement which and samples of metarhyolites interlayered within metasediments underwent extension just prior to orogenic deformation. There- of the Cachoeirinha belt yielded ages comprised between 625 Ma fore, deposition and metamorphism in an intracontinental setting and 660 Ma (Van Schmus et al., 1995; Kozuch, 2003; Medeiros, is envisaged as the most likely setting for the studied sequences. 2004). Common to all these Neoproterozoic sequences are: (a) their preponderantly siliciclastic nature; (b) the lack of any contem- poraneous calc-alkaline igneous activity (meta-andesites are not Acknowledgements present whereas calc-alkaline to high-K calc-alkaline plutons were intruded during or well after peak metamorphism; Guimarães et al., This work was supported through funding from the Brazilian 2004; Neves et al., 2006b); (c) synchronous metamorphism, which agency Fundac¸ ão de Amparo à Ciência e Tecnologia do Estado de Per- peaked at 630–600 Ma (Arthaud et al., 2008; Santos et al., 2008b; nambuco (FACEPE; grant APQ-0479-1.07/06). We thank Elson P. Guimarães et al., 2004; Medeiros, 2004; Neves et al., 2004, 2006a). Oliveira and an anonymous reviewer for their constructive com- Also noteworthy is the requirement for involvement of source ments. rocks with ages that are presently unknown in the Borborema Province, which almost certainly implies distal provenance. 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