Henrique-Pinto Et Al., 2012

7/29/2019 Henrique-Pinto Et Al., 2012

1/12

121

Revista do Instituto de Geocincias - USP

Geol. USP, Sr. cient., So Paulo, v. 12, n. 3, p. 21-32, Dezembro 2012

Disponvel on-line no endereo www.igc.usp.br/geologiausp - 21 -

Abstract

The So Roque Group is characterized by volcano-sedimentary sequences, in which deposition probably started in the latePaleoproterozoic. U-Pb dating by LA-MC-ICPMS of zircons extracted from predominantly equigranular monzogranitesclasts from Morro Doce and Morro do Polvilho regions, yield paleoproterozoic ages of 2199 8.5 Ma and 2247 13 Ma,respectively. These represent the ages for the main source of granite for the metaconglomerates from the Boturuna For-mation (basal unit of So Roque Group). Its polycyclic history is reinforced by the presence of inherited Archean zircons(2694 29 Ma) found within the clasts. Moreover, these clasts have also been affected by the Neoproterozoic overprintingevent as indicated by their lower intercept Concordia ages. Sm-Nd isotope data for the main clast varieties from the MorroDoce metaconglomerates yield T

DMages of 2.6 to 2.7 Ga, demonstrating that these granites are the recycling products of an

Archean crustal component. The metaconglomerate arkosean framework yields slightly lower Nd(t)

values than those for theclasts, indicating that a younger and/or more primitive source also contributed to the Boturuna Formation.

Keywords: So Roque Group; Metaconglomerates; U-Pb dating; Sm-Nd data; Provenance.

Resumo

O Grupo So Roque caracterizado por uma sequncia vulcanossedimentar com deposio provavelmente iniciada noPaleoproterozoico tardio. Dataes U-Pb obtidas por LA-MC-ICPMS de zirces extrados das variedades predominantesdos clastos de monzogranitos equigranulares, das regies do Morro Doce e Morro do Polvilho, mostram idades paleoprote-rozoicas de 2199 8,5 Ma e 2247 13 Ma, respectivamente. Estas representam as idades da principal fonte de granito da

Formao Boturuna (unidade basal do Grupo So Roque). A histria policclica deste domnio reforada pela presena dezirces arqueanos herdados (2694 29 Ma), encontrados nos clastos. Alm disso, tais clastos tambm foram afetados peloevento Neoproterozoico, conforme indicado pelo intercepto inferior das idades concrdia. Dados isotpicos Sm-Nd para osprincipais clastos do metaconglomerado do Morro Doce tm idades T

DMentre 2,6 a 2,7 Ga, demonstrando que estes granitos

so produtos da reciclagem de um componente crustal arqueano. O arcabouo dos metaconglomerados, quando comparadocom os clastos, mostra valores mais baixos de

Nd(t), indicando contribuies de fontes mais jovens e/ou primitivas para a

Formao Boturuna.

Palavras-chave: Grupo So Roque; Metaconglomerados; Datao U-Pb; Dados Sm-Nd; Provenincia.

Paleoproterozoic source contributions to the So Roque Group

sedimentation: LA-MC-ICPMS U-Pb dating and Sm-Nd systematics

of clasts from metaconglomerates of the Boturuna FormationContribuies de fontes Paleoproterozoicas para a sedimentao do Grupo So Roque:

datao U-Pb LA-MC-ICPMS e sistemtica Sm-Nd dos clastos dos metaconglomerados da

Formao Boturuna

Renato Henrique-Pinto1, Valdecir de Assis Janasi1, Antonio Simonetti2, Colombo Celso Gaeta Tassinari1,

Larry Michael Heaman31Departamento de Mineralogia e Geotectnica, Instituto de Geocincias, Universidade de So Paulo - USP, Rua do Lago 562,

CEP 05508-080, So Paulo, SP, BR ([email protected]; [email protected]; [email protected])2

Department of Civil Engineering and Geological Sciences, University of Notre Dame, South Bend, US ([email protected])

3Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, CA ([email protected])

Received 14 March 2012; accepted 26 July 2012

DOI: 10.5327/Z1519-874X2012000300002


2/12

Henrique-Pinto, R. et al.

- 22 -Geol. USP, Sr. cient., So Paulo, v. 12, n. 3, p. 21-32, Dezembro 2012

INTRODUCTION

The depositional age and geological signicance of theSo Roque Group (SRG) (Mantiqueira Tectonic Province,in Southeast Brazil) remain the focus of considerable de-

bate in the geological literature. Several meta volcano-sed-imentary sequences have been recognized in the so-calledSo Roque Domain. This includes the Serra do ItaberabaGroup, which has been recognized as a medium-grademetamorphic sequence with a depositional age of ~1.5 Ga(Juliani et al., 2000), and is distinct relative to the lower-grade sequences that are commonly grouped into the SRG.The SRG itself is considered by some authors (Juliani,1993; Martin, 2000) as a younger sequence, in view ofits lower-grade metamorphism and proposed erosionalcontact marked by the presence, in metaconglomeratesfrom its basal sequence (Boturuna Formation), of clasts

and volcanic fragments, which are correlated to the Serrado Itaberaba Group (SIG). However, U-Pb zircon datingof acid and basic metavolcanic rocks from the BoturunaFormation has yielded consistently older ages (1790 14Ma; van Schmus et al., 1986; 1750 40 Ma; Oliveira et al.,2008), strongly suggesting that SRG in fact corresponds,at least in part, to an older sequence (Henrique-Pinto andJanasi, 2010).

The metaconglomerates study from the SRG basal se-quence has a long history, with the pioneering study byDerby (1882), who rst documented the occurrence ofsuch rocks in Brazil. A subsequent study by Coutinho(1955) reported a detailed description of the metacon-

glomerates, which are characterized by pebbles and boul-ders largely granitic in nature within an arkosean frame-work. These occur as meter to hectometre-sized lenseswithin a dominantly psammitic sequence. The intercalat-ed bimodal suite of metavolcanic rocks that was used todetermine the age of deposition occurs as thin layers andis characterized by a within-plate geochemical signature(Henrique-Pinto, 2008).

We have reported here the results of LA-MC-ICPMSU-Pb zircon dating of granitic clasts and Sm-Nd isotopedeterminations for granitic and amphibolite clasts, and forthe framework of the metaconglomerates. Together with

the previously reported geochemical data, these new re-sults are used to aid in elucidating the provenance of theSRG and therefore contribute for understanding its tecton-ic signicance.

TECTONIC SETTING

The So Roque Domain is a tectonic block that is locatedbetween the high-metamorphic grade Socorro-GuaxupNappe to the north (currently interpreted as related to the

evolution of the southern branch of the Braslia Fold Belt),and the Embu Domain to the south (related to the RibeiraFold Belt), as observed in Figure 1. In the tectonic modelof Campos Neto (2000), the So Roque Domain is partof a larger block dominated by meta-volcano-sedimentary

sequences metamorphosed to low-to-medium-grade con-ditions (the Apia-So Roque Domain). When togetherwith the Socorro-Guaxup Nappe, these correspond to amagmatic arc domain developed at the border of an oldercratonic nucleus, which is mostly concealed beneath thePhanerozoic Paran sedimentary basin, the ParanapanemaCraton (Mantovani and Brito Neves, 2005).

The rst stratigraphic division of the SRG was pro-posed by Hasui (1976). Subsequently, a two-fold one wasproposed, with the basal Boturuna Formation consisting ofphyllites with quartzite and metacarbonate intercalations,whereas the upper Piragibu Formation is composed of

rhythmic metapsammites succeeded by phyllites that areinterbedded with quartzite. This sequence is interpreted topossibly represent turbidity current deposits in a marineenvironment (Carneiro, 1983; Campos Neto et al., 1983;Dantas, 1990).

Later studies recognized a distinctive volcano-sedimen-tary sequence in the Serra do Itaberaba region (Coutinhoet al., 1982), composed of basic to intermediate tuffs, vol-canic and subvolcanic rocks interbedded with chert, band-ed iron formation (BIF), and detrital sediments. This se-quence was later dened as SIG (Juliani et al., 1986), anddistinguished from the SRG, based on its higher (amphib-olite-facies) metamorphic grade, and the presumed exis-

tence of an erosional contact. The latter is delineated bythe presence of clasts and volcanic fragments from the SIGin metaconglomerates located at SRG base (Juliani, 1993;Martin, 2000). SIG was dated, by Juliani et al. (2000), byU-Pb zircon in metavolcanic rocks at 1395 10 Ma.

A different metavolcano-sedimentary sequence was de-scribed in the Pirapora region (Bistrichi, 1982; Bergmann,1988; Tassinari et al., 2001), which is composed of tholei-itic metabasalts with pillow-lavas (Figueiredo et al., 1982)chemically similar to MORB (Lazzari, 1987; Henrique-Pinto and Janasi, 2010) and associated with pyroclasticsand meta-limestones, showing stromatolite structures

(Bergmann and Fairchild, 1985). Bergmann (1988) inter-preted the Pirapora Formation as the representation of pas-sive margin volcanic centers surrounded by stromatolites.U-Pb zircon (608 7 Ma) and monazite (628 9 Ma) dates(Hackspacker et al., 1999; 2000) suggest a Neoproterozoicage for this sequence; however, recent U-Pb zircon datingfor possible correlative metavolcanic rocks in the Cajamarregion indicate an age of 1750 40 Ma (Oliveira et al.,2008).

The possibility that the SRG base is older than the over-lying layers was stated by Van Schmus et al. (1986), based


3/12

U-Pb dating of clasts from the So Roque Group metaconglomerates


on U-Pb zircon age of 1790 14 Ma obtained for acidmetavolcanic rocks, which are characterized by a within-

plate geochemical signature from the Morro do Polvilho

region (Henrique-Pinto and Janasi, 2010).

LOCAL GEOLOGY

A simplied geological map of the study area is presentedin Figure 2, where most of the metaconglomerate occur-rences from the Boturuna Formation are indicated. The

basal unit of the SRG identied by Coutinho (1955) wasreferred as Morro Doce Formation (Juliani et al., 1999);

part of this sequence was also positioned as lower byCordani et al. (1961) and classied as impure metapsam-

mitic unit (Carneiro, 1983), or basal siliciclastic associa-tion (Fernandes da Silva, 2004). However, these studieswere conducted in different geographical locations.

The Boturuna Formation crops out predominantlynorthwest of the city of So Paulo (Figure 2). It is char-acterized by the predominance of interngered metar-koses and polymictic metaconglomerates with pebblesand cobbles encased by hard-recrystallized framework. Intopographically higher regions (the Jaragu Peak), occur-rences of metasandstones and feldspathic metasandstonesones are present. Small bodies of metavolcanic rocks are

intercalated with metarkoses; those are represented by ba-sic metavolcanic rocks (e.g. small lenses of basaltic tra-chyandesite within the metarkoses), and porphyritic me-

ta-trachydacite (in the Morro do Polvilho region). Themeta-trachydacites dene a chemical signature typical ofwithin-plate magmatism, with low mg#, high Zr, Y, Nb,and low Sr (Henrique-Pinto and Janasi, 2010).

The Jaragu amphibolite, with an approximate ex-posure area of 1.5 x 2.5 km, occurs in apparent discor-dance in relation to detrital metasediments (Gomes, 1962).It shares the MORB-like signature of the volcanics fromthe Pirapora Formation, like low concentrations of incom-

patible elements such as Rb, Nb and Th (Henrique-Pintoand Janasi, 2010). Small occurrences of impure metalime-stones surrounding the main body further suggest a corre-

lation with the Pirapora Formation.The occurrences of calc-silicate rocks appearing in thenorth-central portion of the studied area (Cordani et al.,1963) belong to SIG, as probably do the scattered occur-rences of staurolite-mica schist that appear as windowswithin the area consisting predominantly of metarkosesfrom the Boturuna Formation.

The southern portion of the study area (Figure 2) isdominated by Neoproterozoic granitic rocks from Itaquiand Cantareira plutons; the small Fazenda Ithay Granite,intruding the metarkose unit in the center of the area is

Figure 1.Simplied geotectonic map of the region near the city of So Paulo (modied from Campos Neto, 2000). 1: Phanerozoic

cover and intrusive rocks; 2: late and post-tectonic granites; 3: (garnet)-(muscovite)-biotite granites; 4: porphyritic biotite

granites; 5: porphyritic (hornblende)-biotite granites; 6: Socorro-Guaxup domain; 7: Paleoproterozoic gneisses (basement

to Embu Domain metasupracrustals); 8: Embu Domain metasupracrustal sequences; 9: So Roque Group and Votuverava

Formation; 10: Serra do Itaberaba Group; 11: Costeiro complex. The small box shows the location of Figure 2.

1

48 W

23 S

Brazil51 45

20

25

State of So Paulo

So Paulo

Atlantic Ocean 20 km

N

So Roque Domain

Paran

Basin

24 S

47 W 46 W 45 W

7 8 9 10 11

2 3 4 5 6


4/12



petrographically similar, being dominated by porphyriticbiotite ( hornblende) granites. In contrast, the Tico-TicoGranite, part of which appears in the extreme north of thestudy area, is intrusive in SIG, and consists of two micaleucogranites. Tourmaline-bearing pegmatite and aplitedikes are scattered over most of the area.

Tassinari et al. (1985) obtained a Rb-Sr isochron age of1200 75 Ma for granitic pebbles from a metaconglom-erate of Boturuna Formation. The evolution of the Sr iso-topic ratio was used to suggest that the source of pebblesformed at ~2.4 Ga K-Ar ages for groundmass biotite range

between 800 to 750 Ma, and they were interpreted as rep-resenting the last metamorphic event that affected theserocks (Tassinari, 1988).

It is possible that the basal unit (sensu Coutinho, 1955)was deposited in a deep-sea environment (Odman, 1955),which was affected by proximal arkosean terrigenous oreven conglomeratic sediments. Petrographic study of gran-ites clasts for SRG metaconglomerates (Henrique-Pinto,2008; Henrique-Pinto and Janasi, 2010) allowed the iden-tication of four petrographic varieties: porphyritic biotitemonzogranite, inequigranular monzogranite, equigranular

Figure 2. Geological map of So Roque Domain NW of the city of So Paulo (modied from IPT, 1983).

4650'0''W 4648'0''W 4646'0''W

Brazil So Paulo State51 45

20

25

Pico do Jaragu

Cantareira

Fazenda Ithay

MD - 01C

MD - 10B

Morro Doce

Itaqui Pluton

2328'0''S

2326'0''S

Morro do Polvilho

Kilometers

Jaragu Amphibolite

N

W

L

E

4644'0''W

Sn

Synclines

Anticlines

Faults and LineamentsProterozoic Units

Late proterozoic Units

Serra do Itaberaba GroupSo Roque Group

8

7

5

4 3 2 1

6

? ?9 10 11Pirapora do BomJesus Formation

Piragibu Formation

Boturuna Formation

Morro da Pedra Petraand Nhanguu

Formation

120

1 - Acid Metavolcanics2 - Basic Metavolcanics

3 - Metaconglomerates4 - Metarkoses5 - Quartzites6 - Phyllites7 - Metasandstones8 - Metalimestones and Metadolomites9 - Amphibolites10 - Cianite-estaurolite schists11 - Banded Calcic-Silicates

1 2 3 4


5/12



monzogranite, and inequigranular leucogranite. The clastsappear to be broadly comagmatic, as suggested by theirdenition of a single geochemical evolution trend consis-tent with normal differentiation in granitic magmas.

The metarkoses show clear chemical afnities with the

granitic pebbles from the metaconglomerate; their REEpatterns, although similar to the clasts, are characterizedby a smaller negative Eu anomaly suggestive of an addi-tional source. This possibly corresponds to a mac igneoussource as indicated by their higher Cr/Th, Ti/Zr, and Co/Thratios (Henrique-Pinto and Janasi, 2010).

ANALYTICAL METHODS

Zircon separation

Zircon crystals for U-Pb geochronological dating were ex-tracted from two clasts of equigranular muscovite-biotitemonzogranite, which represent the most typical variety foundin the metaconglomerate at the Morro Doce (MD-01C) andMorro do Polvilho (MD-10B) localities.

The samples were crushed in a steel jaw-crusher andsubsequently in a disk mill. The concentrates were ob-tained in the Mineral Separation Laboratory of Institutode Geocincias, Universidade de So Paulo, in Brazil, bystandard procedures involving a vibrating table (Wiley)and heavy liquids (bromoform and methylene iodide).

Microscopic studies of the heavy mineral concentrateswere conducted in transmitted light using aZeiss Axioplan

microscope. The concentrates were then submitted to mag-netic separation procedures using a FrantzTM type isody-namic magnetic separator, initially with +10 side and 15forward dip. Zircons were concentrated in the nonmag-netic fraction at 1.5 A. The different magnetic fractions ofzircons were then split by varying the inclination angle ofthe separator from +6 to lower values, until the last size-able fraction was obtained. Handpicking involved the se-lection of the least magnetic crystals with well-preserved

prismatic faces, vitreous luster, and least amount of inclu-sions as possible.

LA-ICPMS U-Pb dating

Isotopic determinations were conducted at the Departmentof Earth and Atmospheric Sciences, University of Alberta(Edmonton, Canada), by LA-MC-ICPMS using a NuPlasma mass spectrometer equipped with three ion coun-ters and 12 Faraday detectors; this instrument was coupledto a Nd:YAG UP213 nm New Wave laser ablation system.The accuracy and precision of analyses were validated

by analysing zircon standards BR266 and 91500. A spotsize of 20 m was used for the laser ablation runs given

in general the high total Pb contents of the zircons. Thisresulted in adequate U and Pb ion signal intensities and al-lowed spots to be located in areas free of fractures and in-clusions. Details of the analytical protocol employed hereare given in Simonetti et al. (2005).

Sm-Nd analyses

Sm-Nd isotope analyses were performed at the Centrode Pesquisas Geocronolgicas (CPGeo), Instituto deGeocincias, Universidade de So Paulo, Brazil, followingthe procedures described by Sato et al. (1995). The Nd iso-topic ratios were obtained using a multicollector FinniganMAT-262 mass spectrometer, whereas the Sm ones wereobtained using a single collector VG-354 mass spectrom-eter. The average 143Nd/144Nd values measured for the LaJolla and BCR-1 Nd standards during the period of this

study are 0.511849 0.000025 and 0.512662 0.000027(yearly 1 variation), respectively. The maximum measurederrors were 0.09% for the 147Sm/144Nd ratio and 0.00002for 143Nd/144Nd (2 precision level).

Ndcalculations as-

sume present CHUR ratios of143Nd/144Nd = 0.512638 and147Sm/144Nd = 0.1967. The constant used decay was 6.54 x10-12 years-1. T

DMcalculations are made using the method

of DePaolo (1988). Details of the analytical protocol em-ployed here are given in Sato et al. (1995).

RESULTS OF LA-ICPMS U-PB DATING

Sample MD-01C

Thirty-nine analyses were conducted for sample MD-01C(Table 1). Eight points are essentially concordant (discor-dance < 3%) and yield an average date of 2199 9 Ma.This is interpreted as the age of magmatic crystallizationfor this granitic clast. Two analyses from crystal 6b, al-though discordant, are clearly inherited and dene discor-dia with an upper intercept age of 2694 29 Ma (lowerintercept ~zero), which is indicative of an Archean inheri-tance (Figure 3). The remaining analyses dene a singlediscordia and yield an upper intercept age of 2209 14

Ma, which is within uncertainty to the average age (2199 9 Ma), dened by the concordant crystals. The lower in-tercept age at 527 72 Ma reects the overprint associatedwith the Neoproterozoic thermal event (Figure 3).

Sample MD-10B

Thirty-two analyses were conducted for sample MD-10B(Morro do Polvilho region), of which six were excludedfrom regression because of for their complex zoning andmultiple age domains (Table 2). The remaining 26 points


6/12


7/12



indicate variable degrees of discordance, between 4 and22%, and dene a discordia with an upper intercept age at2247 13 Ma; which is interpreted as the magmatic crys-tallization age for this granite clast. The lower interceptage at 637 84 Ma once again reects the overprint as-sociated with the Neoproterozoic thermal event (Figure 4).

Sm-Nd Data

Sm-Nd isotope data were obtained from six representa-tive samples of the main clast varieties of the Morro Doce

metaconglomerate, all from outcrop MD-01. Results arelisted in Table 3 and illustrated in Figure 5. Given a 2.2Ga magmatic crystallization age, Nd(t) values are all neg-ative and appear to cluster between values from -3.1 to-4.3; an exception is the inequigranular granite sampleMD-01D that is characterized by a more negative valueof -6.7. The metarkose framework is slightly less nega-tive (

Nd(t)= -2.3), suggesting contribution from a distinct

source, perhaps of mac character, a feature also suggest-ed by whole-rock chemistry (Henrique-Pinto and Janasi,2010). Interestingly, the amphibolite clast does not seem

to equate to this same source since its Nd(t)

(-3.6) at t = 2.2Ga is within the same range for most of the granite clasts.

The Sm-Nd TDM

ages of the granitic clasts and themetarkose framework cluster at 2.6 to 2.7 Ga (Figure 5),combined with the inherited age (2694 29 Ma) reportedin sample MD-01C, reinforces the idea that these granitesare products of remelting a ~2.7 Ga crustal component.The older TDM age (3.2 Ga, Table 3) dened by the in -equigranular leucogranite MD-01D can be a reection ofits higher 147Sm/144Nd ratio (0.135), and may result fromLREE fractionation during magma evolution (Henrique-

Pinto and Janasi, 2010). Hence, this older TDM age mostprobably does not have any geological signicance. The147Sm/144Nd ratio of the metabasic clast (0.126) is typicalfor this rock type, its T

DMage (2.8 Ga) is slightly older than

those of the typical granite clasts.

DISCUSSION

The metaconglomerates from the Boturuna Formation(basal unit of SRG) are part of the detrital sedimentary

Figure 3. Concordia plot for LA-MC-ICPMS U-Pb zircon dating of sample MD-01C, a biotite monzogranite clast from the

Morro Doce region. Backscattering images obtained by scanning electron microscopy with numbers linked to Table 1.

Concordia Age = 2199.8 8.5 Ma

(2, decay-const. errs included)

MSWD (of concordance) = 0.13,

Probability (of concordance) = 0.71

n = 8 analyses

Grain 6B

Intercepts at

238 270 and 2694 29 Ma

Sample MD-01C Intercepts at

52772 and 2209 14 MAMSWD = 3.8

1400

2200

0.1

0.2

0.3

0.4

0 2 4 6 8 10 12 14

207Pb/235U

206P

b/238U

data-point error ellipses are 2

CP

10

9

64 5

14

50 um

100 um

200 um100 um 200 um

100 um

12

100 umCP

CP

3

100 umCP

CP

CP CP CP


8/12



Table

2.

U-P

bz

ircon

LA-M

C-IC

PMSda

tafrom

biotitemonzogran

ite

clas

tMD-1

0B(Bo

turuna

Forma

tion,

So

Roque

Group

).

SampleMD-10B

207Pb/206Pb

206Pb/238U

Anal#

206Pb/204Pb

207Pb/206P

b

2

error

207Pb/235U

2

error

206Pb/238U

2

error

rho

age(Ma)

2

error

age(Ma)

2e

rror

discord.%

3

24120

0.1

3008

0.0

0177

5.2

712

0.2

636

0.2

935

0.0

144

0.9

62

2

099

24

1659

82

21.0

4

12041

0.1

3708

0.0

0144

7.0

345

0.3

261

0.3

741

0.0

173

0.9

74

2

191

18

2049

95

6.5

6

12997

0.1

3764

0.0

0148

7.3

443

0.3

198

0.3

864

0.0

168

0.9

69

2

198

19

2106

91

4.2

6B

49618

0.1

3581

0.0

0140

6.2

804

0.2

902

0.3

349

0.0

155

0.9

75

2

174

18

1862

86

14.4

8A

8757

0.1

3791

0.0

0156

7.4

940

0.4

118

0.3

938

0.0

215

0.9

79

2

201

20

2140

11

7

2.8

9A-2

11234

0.1

2422

0.0

0159

4.9

706

0.4

040

0.2

892

0.0

234

0.9

88

2

018

23

1638

13

2

18.8

10A

33907

0.1

3681

0.0

0140

6.1

561

0.3

406

0.3

257

0.0

180

0.9

83

2

187

18

1817

10

0

16.9

15A

90378

0.1

2408

0.0

0186

4.8

212

0.3

155

0.2

778

0.0

179

0.9

73

2

016

27

1580

10

2

21.6

17A

29097

0.1

3812

0.0

0143

6.8

434

0.2

853

0.3

588

0.0

149

0.9

69

2

204

18

1977

82

10.3

19A

76219

0.1

3600

0.0

0139

6.4

418

0.3

206

0.3

432

0.0

171

0.9

79

2

177

18

1902

95

12.6

20A

31920

0.1

2699

0.0

0226

5.0

017

0.1

976

0.2

826

0.0

104

0.8

93

2

057

31

1605

59

22.0

22A

91423

0.1

3785

0.0

0145

7.0

068

0.3

098

0.3

681

0.0

162

0.9

72

2

200

18

2021

89

8.2

22A-2

11290

0.1

3652

0.0

0144

6.4

139

0.2

916

0.3

402

0.0

154

0.9

73

2

184

18

1888

86

13.5

23A

48192

0.1

3711

0.0

0139

6.7

619

0.3

531

0.3

572

0.0

186

0.9

81

2

191

18

1969

10

3

10.1

24A

51309

0.1

3784

0.0

0142

7.0

756

0.4

576

0.3

716

0.0

240

0.9

87

2

200

18

2037

13

2

7.4

24A-2

26436

0.1

3576

0.0

0141

6.6

292

0.3

532

0.3

536

0.0

188

0.9

81

2

174

18

1952

10

4

10.2

26A

19428

0.1

3683

0.0

0151

6.8

769

0.3

205

0.3

644

0.0

169

0.9

72

2

187

19

2003

93

8.4

26A-2

32982

0.1

3744

0.0

0142

6.9

506

0.4

326

0.3

661

0.0

228

0.9

86

2

195

18

2011

12

5

8.4

28A

254449

0.1

3941

0.0

0143

7.4

495

0.3

629

0.3

872

0.0

188

0.9

78

2

220

18

2110

10

3

5.0

32A

27717

0.1

3916

0.0

0151

7.3

358

0.3

564

0.3

824

0.0

185

0.9

75

2

217

19

2087

10

1

5.8

32A-2

28824

0.1

3895

0.0

0147

7.0

713

0.3

296

0.3

686

0.0

171

0.9

74

2

214

18

2023

94

8.6

35A

20853

0.1

3344

0.0

0203

5.4

737

0.2

190

0.3

005

0.0

115

0.9

25

2

144

27

1694

65

21.0

35A-2

18720

0.1

3596

0.0

0145

6.6

634

0.3

702

0.3

550

0.0

197

0.9

82

2

176

19

1958

10

9

10.0

35A-3

37686

0.1

3807

0.0

0141

7.0

347

0.3

286

0.3

692

0.0

172

0.9

76

2

203

18

2026

95

8.1

36A

105117

0.1

3705

0.0

0140

6.9

537

0.4

052

0.3

671

0.0

214

0.9

85

2

190

18

2016

11

7

8.0

40A

68565

0.1

3927

0.0

0147

7.2

558

0.2

903

0.3

774

0.0

150

0.9

65

2

218

18

2064

82

6.9

c

omplexlyzoned-multi-age

9A

32582

0.1

1969

0.0

0123

4.4

337

0.1

966

0.2

684

0.0

119

0.9

73

1

952

18

1532

68

21.5

13A

infnite

0.1

2898

0.0

0146

5.8

125

0.2

413

0.3

259

0.0

134

0.9

62

2

084

20

1818

75

12.7

14A

21059

0.1

3365

0.0

0149

5.9

082

0.3

829

0.3

230

0.0

209

0.9

85

2

146

19

1804

11

7

15.9

15A-2

75382

0.1

3169

0.0

0157

5.9

112

0.4

176

0.3

233

0.0

227

0.9

86

2

121

21

1806

12

7

14.8

23A-2

97993

0.1

3203

0.0

0141

5.8

427

0.2

823

0.3

234

0.0

156

0.9

76

2

125

19

1806

87

15.0

38A

8532

0.1

3761

0.0

0174

6.6

580

0.3

398

0.3

509

0.0

177

0.9

69

2

197

22

1939

98

11.8


9/12



Figure 4. Concordia plot for LA-MC-ICPMS U-Pb zircon dating of sample MD-10B, a biotite monzogranite clast from the

Morro do Polvilho region. Backscattering images obtained by scanning electron microscopy with numbers linked to Table 2.

Sample MD10B Intercepts at

data-point error ellipses are 2

637 84 and 2247 13 MaMSWD = 1.08 n = 26 analyses

1700

1900

2300

0.223.5 4.5 5.5 6.5 7.5 8.5

0.26

0.30

0.34

0.38

0.42

0.46

207 Pb/235U

206

Pb/238U

50 um

100 um

50 um 50 um 50 um

50 um

50 um

CP

CP

CP

CP CP CP

13

6

CP

CP

9

38

26

22 40 30

Samples ClastsSm Nd 147Sm/

Error143Nd/

ErrorT

DM

(0)

(t)(ppm) (ppm) 144Nd 144Nd (Ga)

MD-01B Metarkose framework 5.856 34.745 0.1019 0.0006 0.511160 0.000011 2.6 -28.84 -2.25

MD-01C Equigranular granite 5.752 42.047 0.027 0.0005 0.510779 0.000008 2.7 -36.27 -4.30

MD-01D Inequigranular leucogranite 1.900 8.514 0.1349 0.0008 0.511409 0.000012 3.2 -23.98 -6.66

MD-01E Inequigranular granite 6.005 39.859 0.0911 0.0005 0.510961 0.000012 2.6 -32.71 -3.09

MD-01M Metabasic rock 1.261 6.063 0.1257 0.0007 0.511431 0.000014 2.8 -23.55 -3.64

MD-01N Porphyritic granite 7.629 46.601 0.0990 0.0006 0.511068 0.000010 2.6 -30.62 -3.22

t = 2.2 Ga, the crystallization age of the granite clasts;TDM

according to DePaolo (1988).

Table 3. Sm-Nd isotope data for clasts and framework of metaconglomerate MD-01 (Boturuna Formation, So Roque Group).

sequences indicating proximal sources, as identied by thepresence of pebbles and boulders supported by an arkoseanframework. Thus, these rocks have an excellent potential forcharacterizing the main source for the SRG.

U-Pb dating by LA-MC-ICP-MS of zircons extractedfrom predominantly equigranular monzogranites clasts with-in the Morro Doce and Morro do Polvilho regions indicatePaleoproterozoic ages for magmatic crystallization (2199 9Ma and 2247 13 Ma, respectively). Even taking into accountthe ~10 Ma uncertainties associated with each date, the ca. 50

Ma difference between the two ages is suggestive that theseclasts, although very similar in petrography and chemistry, arenot strictly comagmatic, i.e., do not derive from exactly thesame source.

The polycyclic history of the zircons is reinforced by thepresence of inherited grains found in the clast MD-01B in theMorro Doce occurrence (2694 29 Ma). Furthermore, bothdated clasts were also affected by a neoproterozoic event, asindicated by lower intercept dates in the 530 to 640 Ma range.Although imprecise, the latter dates can be attributed to the


10/12



important thermal event of metamorphism and intrusion oflarge amounts of granitic plutons that affected the Apia-SoRoque Domain and the Socorro-Guaxup Nappe, which to-gether correspond to the reworked border of the ParanapanemaCraton (Campos Neto, 2000).

The ages of the granite clasts are not documented in base-ment granitic rocks that occur at the southwestern margin ofSo Francisco craton, which are typically slightly younger

and range between 2020 and 2140 Ma (Campos Neto et al.,2004). Similar ages are found in the basement of EspinhaoSupergroup in eastern So Francisco Craton (Mineiro Belt;Teixeira et al., 2008). However, correlation with some parts ofthe So Francisco Craton seems improbable, since the Apia-So Roque Domain is thought to belong to a different paleo-continent (Paranapanema). It seems more probable, therefore,that equivalents are present in the basement of the AunguiSupergroup as exposed in the Tigre, Setuva and Betari nuclei,where orthogneisses of similar age are described (Kaulfuss,2001; Cury et al., 2002; Siga Jr. et al., 2007). Remarkably, thelatter are intruded by younger (~1.75 Ga) syenogranitic orthog-

neisses, which are considered to represent an extensional tec-tonic event (Kaulfuss, 2001; Siga Jr. et al., 2011) that is possiblyequivalent to the one that generated the bimodal metavolcanicsequence of within-plate geochemical signature described inthe SRG (Henrique-Pinto and Janasi, 2010).

Sm-Nd isotope data from the main clast varieties fromthe Morro Doce metaconglomerates yield T

DMages of 2.6 to

2.7 Ga, indicating that these granites are the recycling prod-ucts of an Archean crust; an interpretation that is corroborat-ed with the presence of an inherited zircon dated at ~2.7 Ga.The metaconglomerate arkosean framework yields slightly

Figure 5.Nd

versus t(Ga) diagram of main granite clasts of Boturuna Formation.

DM

t (Ga)

15

10

5

0

-50.5 1 1.5 2 2.5 3

Framework of metaconglomerate (MD-01B)

Pebbles:

Equigranular monzogranite (MD-01C)

Inequigranular monzogranite (MD-01D)

Metabasic rock (MD-01M)

Porphyrytic monzogranite (MD-01N)

Inequigranular leucogranite (MD-01D)

3.5 4

-10

-15

-20

-25

-30

-35

-40

Nd

lower Nd(t)

values compared to the clasts, therefore young-er and/or more mac source may contribute to the BoturunaFormation. This is in agreement with the geochemical sig-nature of the associated metarkoses since a mac igneousinput was identied based on the whole-rock geochemistry(Henrique-Pinto and Janasi, 2010).

REFERENCES

BERGMANN, M. Caracterizao Estratigrfca e Estruturalda Seqncia Vulcano-Sedimentar do Grupo So Roque na

Regio de Pirapora do Bom Jesus - Estado de So Paulo.

1988. Dissertao de Mestrado - Instituto de Geocincias,Universidade de So Paulo, So Paulo.

BERGMANN, M.; FAIRCHILD, T.R. Estromatlitos doGrupo So Roque, Proterozico Superior, Regio de Piraporade Bom Jesus, Estado de So Paulo. Anais da Academia

Brasileira de Cincias, v. 57, n. 1, p. 116-117, 1985.

BISTRICHI, C.A. Geologia do Sinclinrio de Pirapora, SP.1982. Dissertao de Mestrado - Instituto de Geocincias,Universidade de So Paulo, So Paulo.

CAMPOS NETO, M.C.; BASEI, M.A.S; ARTUR, A.C.;SILVA, M.E.; MACHADO, R.; DIAS NETO, C.M.;FRAGOSO CESAR, A.R.; SOUZA, A.P. Geologia dasFolhas Piracaia e Igarat. IPT Pr-Minrio, 1 JornadaSobre a Carta Geolgica do Estado de So Paulo em 1:50,000. 1983, p. 55-76.

DM: evolution line of the depleted mantle (De Paolo, 1988).


11/12



CAMPOS NETO, M.C. Orogenic Systems From SouthwesternGondwana: an Approach to Brasiliano-Pan African Cycleand Orognic Collage in Southeastern Brazil. In: XXXIINTERNATIONAL GEOLOGICAL CONGRESS, 2000.Extended Abstracts, Rio de Janeiro, Brazil, 2000, p. 335-365.

CAMPOS NETO, M.C.; BASEI, M.A.S.; VLACH, S.R.F.;CABY, R.; SZABO, G.A.J.; VASCONCELOS, P. Migrao deOrgenos e Superposio de Orogneses: Um Esboo da ColagemBrasiliana no Sul do Crton do So Francisco, SE-Brasil. GeologiaUSP: Srie Cientca, So Paulo, v. 4, p. 13-40, 2004.

CARNEIRO, C.D.R.Anlise Estrutural do Grupo So Roquena Faixa entre o Pico do Jaragu e a Serra dos Cristais,SP. 1983. Tese (Doutorado) - Instituto de Geocincias,Universidade de So Paulo, So Paulo.

CORDANI, U.G.; CAMPOS, A.C.R.; DAVINO, A.;BJRNBER, A.J.S. Geologia da Regio do Jaragu.Boletimda Sociedade Brasileira de Geologia, So Paulo, v. 10, n. 20,

p. 73-91, 1961.

CORDANI, U.G.; GOMES, C.B.; GIRARDI, V.A.V. RochasClcio-Silicatadas da Regio de Perus, SP. Anais da AcademiaBrasileira de Cincias, v. 35, n. 3, p. 361-372, 1963.

COUTINHO, J.M.V. Metaconglomerado e rochas associadasno Municpio de So Paulo.Boletim Faculdade de FilosofaCincias e Letras, Universidade de So Paulo, So Paulo, v.

186, Mineralogia 13, p. 5-56, 1955.

COUTINHO, J.M.V.; RODRIGUES, E.P.; SUEMITSU, A.;JULIANI. C.; BELJAVSKIS, P.; PAULO, T.Y.P. Geologia ePetrologia da Seqncia Vulcano-Sedimentar do Grupo SoRoque na Serra de Itaberaba SP. In: XXXII CONGRESSOBRASILEIRO DE GEOLOGIA, Salvador,Anais..., v. 2, 1982,

p. 624-640.

CURY, L.F.; KAULFUSS, G.A.; SIGA JR., O.; BASEI,M.A.S.; HARARA, O.M.; SATO, K. Idades U-Pb (Zirces)de 1.75 Ga em Granitides Alcalinos Deformados dos Ncleos

Betara e Tigre: Evidncias de Regimes Extensionais doEstateriano na Faixa Apia. Geologia USP, Srie Cientfca, v.2, p. 95-108, 2002.

DANTAS, A.S.L. Geologia da Faixa So Roque e IntrusivasAssociadas na Regio entre So Paulo e Mairipor, Norte

de So Paulo. 1990. Dissertao de Mestrado - Instituto deGeocincias, Universidade de So Paulo, So Paulo.

DEPAOLO, D.J. Neodymium Isotope Geochemistry. AnIntroduction. Springer, Berlin, 1988. 187 p.

DERBY, O.A. Relatrio acerca dos estudos geolgicospraticados nos Valles do rio das Velhas e alto S. Francisco.Apresentado ao Conselheiro Manoel de Arajo, 29 de maro,1882. Typographia Nacional, Rio de Janeiro.

FERNANDES DA SILVA, P.C. Litofcies e ProvveisAmbientes de Sedimentao do Grupo So Roque na Regiode Votorantim e Salto de Pirapora, SP. Revista do InstitutoGeolgico, So Paulo, v. 25, n. 1/2, p. 29-48, 2004.

FIGUEIREDO, M.C.H.; BERGMANN, M.; PENALVA, F.;TASSINARI, C.C.G. Ocorrncia de pillow-lavas no GrupoSo Roque, Estado de So Paulo.Revista Cincias da Terra,v. 2, p. 6-8, 1982.

GOMES, C.B. Contribuio ao Conhecimento dos Anbolitosda Regio do Jaragu, SP. Boletim Sociedade Brasileira de

Geologia, So Paulo, v. 11, n. 1, p. 57-73, 1962.HACKSPACHER, P.C.; DANTAS, E.L.; GODOY, A.M.;OLIVEIRA, M.A.F.; FETTER, A.; VAN SCHMUS, W.R.Considerations About the Evolution of the Ribeira Belt inthe So Paulo State Brazil, From U/Pb Geochronology inMetavolcanic Rocks of the So Roque Group. In: II SOUTHAMERICAN SYMPOSIUM ON ISOTOPE GEOLOGY.Cordoba, Argentina,Actas, 1999, p. 310-313.

HACKSPACHER, P.C.; DANTAS, E.L.; SPOLADORE,A.; FETTER, A.H.; OLIVEIRA, M.A.F. Evidence for

Neoproterozoic back-arc basin development in the Central

Ribeira Belt, southeastern Brazil: new geochronological andgeochemical constraints from the So Roque-Aungui Groups.

Revista Brasileira de Geocincias, v. 30, p. 110-114, 2000.

HASUI, Y. Consideraes Sobre a Estratigraa do Pr-Cambriano na Regio de So Paulo. Boletim Instituto deGeocincias, Universidade de So Paulo, So Paulo, v. 7, p.107-112, 1976.

HENRIQUE-PINTO, R. Metaconglomerados e RochasAssociadas do Grupo So Roque a Noroeste da Cidade de

So Paulo: Provenincia e Implicaes para a Idade da

Sedimentao. 2008. Dissertao de Mestrado - Instituto deGeocincias, Universidade de So Paulo, So Paulo.

HENRIQUE-PINTO, R.; JANASI, V.A. metaconglomeradose Rochas Associadas do Grupo So Roque a Norte da Cidadede So Paulo, Brasil.Revista Brasileira de Geocincias, v. 40,n. 3, p. 409-425, 2010.

INSTITUTO DE PESQUISAS TECNOLGICAS IPT. CartaGeolgica do Estado de So Paulo em Escala 1:50.000. Secretariada Indstria, Comrcio, Cincia e Tecnologia, Pr-Minrio, 1983.


12/12



JULIANI, C.; BELJAVSKIS, P.; SCHORSCHER, H.D.Petrognese do Vulcanismo e Aspectos MetalogenticosAssociados: Grupo Serra do Itaberaba na Regio do SoRoque SP. In: XXXIV CONGRESSO BRASILEIRO DEGEOLOGIA, Goinia.Anais 2, 1986. p. 730-745.

JULIANI, C. Geologia, Petrognese e AspectosMetalogenticos dos Grupos Serra do Itaberaba e So Roque

na Regio das Serras do Itaberaba e Pedra Branca, NE da

Cidade de So Paulo, SP.1993. 2 v. Tese (Doutorado) - Institutode Geocincias, Universidade de So Paulo, So Paulo.

JULIANI, C.; MARTIN, M.A.B.; CLARIMUNDO, S.J.;MCREATH, I.; PERTERSEN Jr. K.J. Geologia dos GruposSerra do Itaberaba e So Roque entre o Pico do Jaragu eAraarigama, So Paulo. In: SIMPSIO DE GEOLOGIADO SUDESTE, SBG/NSP-NRJ/ES guas de So Pedro,

Boletim de Resumos, 1999. v. 6, p. 26.JULIANI, C.; HACKSPAKER, P.; DANTAS, E.L.; FETTER,A.H. The Mesoproterozoic volcano-sedimentary Serra doItaberaba Group of the central Ribeira Belt, So Paulo, Brazil:implications for the age of the overlying So Roque Group.

Revista Brasileira de Geocincias, v. 30, p. 82-86, 2000.

KAULFUSS, G.A. Geocronologia dos Ncleos deEmbasamento Setuva, Betara e Tigre, Norte de Curitiba-

Paran. 2001. Dissertao de Mestrado - Instituto deGeocincias, Universidade de So Paulo, So Paulo.

LAZZARI, M.L. o Metabasito de Pirapora do Bom Jesus.1987. Dissertao de Mestrado - Instituto de Geocincias,Universidade de So Paulo, So Paulo.

MANTOVANI, M.S.M.; BRITO NEVES, B.B. TheParanapanema Lithospheric Block: Its Importance forProterozoic (Rodinia, Gondwana) Supercontinent Theories.Gondwana Research, v. 8, p. 303-315, 2005.

MARTIN, M.A.B. Geologia e Petrografa e Metamorfsmodos Grupos Serra do Itaberaba e So Roque a Noroeste da

Cidade de So Paulo (SP). 2000. Dissertao de Mestrado

- Instituto de Geocincias, Universidade de So Paulo,So Paulo.

ODMAN, O.H. A Pre-Cambrian Conglomerate With Pebblesof Deep-Seated Rocks Near So Paulo, Brazil. Engenharia,

Minerao e Metalurgia, v. 21, n. 121, p. 32, 1955.

OLIVEIRA, M.A.F.; MELO, R.P.; NARDY, A.J.R.;ARAB, P.B.; TRINDADE, I. New U/Pb PalaeoproterozoicZircon Age For The Cajamar Metabasite, So RoqueGroup, Central Ribeira Belt, Southeastern Brazil. In: VISOUTH AMERICAM SYMPOSIUM ON ISOTOPE

GEOLOGY. San Carlos de Bariloche, Argentina, 2008.p. 1-4.

SATO, K.; TASSINARI, C.C.G.; KAWASHITA, K.;PETRONILHO, L. Mtodo geocronolgico Sm- Nd no IG-

USP e suas aplicaes. Anais da Academia Brasileira deCincias, v. 67, n. 3, p. 315-336, 1995.

SIGA Jr O.; BASEI, M.A.S.; PASSARELLI, C.R.; HARARA,O.M.; SATO, K.; CURY, L.F.; PRAZERES FILHO, H.J.Geocronologia das Rochas Gnissico-Migmatticas eSienogranticas do Ncleo Setuva (PR): implicaes tectnicas.

Revista Brasileira de Geocincias, v. 37, n. 1, p. 114-128, 2007.

SIGA Jr O.; CURY, L.F.; McREATH, I.; RIBEIRO, L.M.A.L.;SATO, K.; BASEI, M.A.S.; PASSARELLI, C.R. Geologyand geochronology of the Betara region in south-southeastern

Brazil: Evidence for possible Statherian (1.80-1.75 Ga) andCalymmian (1.50-1.45 Ga) extension events. GondwanaResearch, v. 19, n. 1, p. 260-274, 2011.

SIMONETTI, A.; HEAMAN, L.M.; HARTLAUB, R.P.;CREASER, R.A.; MACHATTIE, T.G. U-Pb Zircon Dating

by Laser Ablation-MC-ICP-MS Using a New Multiple IonCounting Faraday Collector Array. Journal of Analytical

Atomic Spectrometry, v. 20, p. 677-686, 2005.

TASSINARI, C.C.G. As Idades das Rochas e dos EventosMetamrfcos da Poro Sudeste do Estado de So Paulo e

sua Evoluo Crustal. 1988. Tese (Doutorado) - Instituto de

Geocincias, Universidade de So Paulo, So Paulo.

TASSINARI, C.C.G.; KAWASHITA, K.; KIKUCHI, R.K.P.Estudo Geocronolgico nos Metaconglomerados do Grupo SoRoque, Estado de So Paulo. In: X SIMPSIO REGIONALDE GEOLOGIA, So Paulo,Boletim de Resumos, 1985, v. 1,

p. 201-208.

TASSINARI, C.C.G.; MUNH, J.M.U.; CORREIA, C.T.Neoproterozoic Oceans in the Ribeira Belt (southeasternBrazil): The Pirapora do Bom Jesus Ophiolitic Complex.

Episodes, v. 24, n. 4, p. 245-251, 2001.

TEIXEIRA, W.; VILA, A.C.; NUNES, L.C. Nd-SrIsotopic Geochemistry and U-Pb Geocronology of the FGranitic Gneiss and Lajedo Granodiorite: Implications forPaleoproterozoic Evolution of the Mineiro Belt, Southern SoFrancisco Craton, Brazil. Geologia USP: Srie Cientfca, SoPaulo, v. 8, n. 1, p. 53-74, 2008.

VAN SCHMUS, W.R.; TASSINARI, C.C.G.; CORDANI,U.G. Estudo Geocronolgico da Parte Inferior do GrupoSo Roque. In: XXXIV CONGRESSO BRASILEIRO DEGEOLOGIA, 34, Goinia,Anais, 3 v, 1986, p. 1399-1406.

Henrique-Pinto Et Al., 2012

Documents

Transcript of Henrique-Pinto Et Al., 2012