U–Pb geochronology of the southern Brası́lia belt (SE-Brazil): sedimentary provenance, Neoproterozoic orogeny and assembly of West Gondwana

doi:10.1016/j.precamres.2003.10.014

Precambrian Research

Volume 130, Issues 1–4, 20 April 2004, Pages 27-55

https://doi.org/10.1016/j.precamres.2003.10.014 Get rights and content

Abstract

The Brası́lia belt borders the western margin of the São Francisco Craton and records the history of ocean opening and closing related to the formation of West Gondwana. This study reports new U–Pb data from the southern sector of the belt in order to provide temporal limits for the deposition and ages of provenance of sediments accumulated in passive margin successions around the south and southwestern margins of the São Francisco Craton, and date the orogenic events leading to the amalgamation of West Gondwana.

Ages of detrital zircons (by ID–TIMS and LA-MC-ICPMS) were obtained from metasedimentary units of the passive margin of the São Francisco Craton from the main tectonic domains of the belt: the internal allochthons (Araxá Group in the Áraxá and Passos Nappes), the external allochthons (Canastra Group, Serra da Boa Esperança Metasedimentary Sequence and Andrelândia Group) and the autochthonous or Cratonic Domain (Andrelândia Group). The patterns of provenance ages for these units are uniform and are characterised as follows: Archean–Paleoproterozoic ages (3.4–3.3, 3.1–2.7, and 2.5–2.4 Ga); Paleoproterozoic ages attributed to the Transamazonian event (2.3–1.9 Ga, with a peak at ca. 2.15 Ga) and to the ca. 1.75 Ga Espinhaço rifting of the São Francisco Craton; ages between 1.6 and 1.2 Ga, with a peak at 1.3 Ga, revealing an unexpected variety of Mesoproterozoic sources, still undetected in the São Francisco Craton; and ages between 0.9 and 1.0 Ga related to the rifting event that led to the individualisation of the São Francisco paleo-continent and formation of its passive margins. An amphibolite intercalation in the Araxá Group yields a rutile age of ca. 0.9 Ga and documents the occurrence of mafic magmatism coeval with sedimentation in the marginal basin.

Detrital zircons from the autochthonous and parautochthonous Andrelândia Group, deposited on the southern margin of the São Francisco Craton, yielded a provenance pattern similar to that of the allochthonous units. This result implies that 1.6–1.2 Ga source rocks must be present in the São Francisco Craton. They could be located either in the cratonic area, which is mostly covered by the Neoproterozoic epicontinental deposits of the Bambuı́ Group, or in the outer paleo-continental margin, buried under the allochthonous units of the Brası́lia belt.

Crustal melting and generation of syntectonic crustal granites and migmatisation at ca. 630 Ma mark the orogenic event that started with westward subduction of the São Francisco plate and ended with continental collision against the Paraná block (and Goiás terrane). Continuing collision led to the exhumation and cooling of the Araxá and Passos metamorphic nappes, as indicated by monazite ages of ca. 605 Ma and mark the final stages of tectonometamorphic activity in the southern Brası́lia belt.

Whilst continent–continent collision was proceeding on the western margin of the São Francisco Craton along the southern Brası́lia belt, eastward subduction in the East was generating the 634–599 Ma Rio Negro magmatic arc which collided with the eastern São Francisco margin at 595–560 Ma, much later than in the Brası́lia belt. Thus, the tectonic effects of the Ribeira belt reached the southernmost sector of the Brası́lia belt creating a zone of superposition. The thermal front of this event affected the proximal Andrelândia Group at ca. 588 Ma, as indicated by monazite age.

The participation of the Amazonian craton in the assembly of western Gondwana occurred at 545–500 Ma in the Paraguay belt and ca. 500 Ma in the Araguaia belt. This, together with the results presented in this work lead to the conclusion that the collision between the Paraná block and Goiás terrane with the São Francisco Craton along the Brası́lia belt preceded the accretion of the Amazonian craton by 50–100 million years.

Section snippets

Introduction and objectives

The West Gondwana supercontinent was formed by the aggregation of Archean–Paleoproterozoic continental blocks along Neoproterozoic mobile belts (Unrug, 1996). To unravel the diachronic history of this major event in the Earth history, addressing the detailed timing of ocean formation and closure is required for each orogenic belt. The Brası́lia belt occupies a key position in West Gondwana because of its central location (Fig. 1), and thus records the interaction between the Paraná, Goiás and

The Tocantins Structural Province

The Tocantins Structural Province resulted from the interaction of three major paleocontinental blocks, whose present remnants are identified as the Amazonian, São Francisco and Paraná cratons (Strieder and Suita, 1999, Pimentel et al., 2000). The latter is completely covered by the Paraná basin, with rather speculative outlines, and may be connected to the Rio de la Plata craton (Almeida et al., 2000).

The Tocantins Structural Province comprises three main branches: the Araguaia, the Paraguay

Analytical procedures

Samples were crushed and pulverized with standard equipment under clean conditions and the heavy minerals concentrated by panning at LOPAG (Universidade Federal de Ouro Preto, Brazil) and at LGPA (Universidade do Estado do Rio de Janeiro, Brazil). Manual panning dispenses the use of a Wilfley table and minimises contamination. The heavy mineral concentrate was passed through a Frantz magnetic separator to extract monazite, titanite, rutile and zircon which was further separated into four

Results

The results are presented in tectonic organisation from the Internal to the Cratonic Domain, following their geographical distribution from north to south. Each analysed sample and pertaining results are described separately, with TIMS data preceding those obtained by LA-MC-ICPMS.

Serra Velha Granite

The Serra Velha Granite (sample 486, Table 2) is one of a series of syn-tectonic granitoids emplaced into metasedimentary rocks and intercalated ortho-amphibolites of the Araxá Group. They are typical biotite–muscovite-bearing collisional granites with geochemical characteristics indicating derivation from crustal melting (Seer, 1999). Quartz, orthoclase, microcline, plagioclase, white mica (phengite) and biotite are the main constituents, with accessory garnet, tourmaline, monazite, apatite

Northern segment

The area east of the Araxá Nappe is in the classical region where the Canastra Group was originally defined by Barbosa (1954). A fine-grained orthoquartzite with millimetric dark layers of heavy minerals, metamorphosed under greenschist facies conditions, was collected from the upper portion of the Canastra Group (sample HS41). Colourless to dark pink-purple zircons are sub-rounded to well rounded, pitted and devoid of metamorphic overgrowth.

The ages of 20 grains analysed by LA-MC-ICPMS (Table 3

Provenance ages and implications

The Araxá, Canastra and Andrelândia groups are consensually interpreted as part of the sedimentary succession of the Neoproterozoic passive margin bordering the western and southern São Francisco Craton (Dardenne, 2000, Trouw et al., 2000). Because of the lack of constraints on the age of sedimentation and reasonable stratigraphic correlation, the Serra da Boa Esperança Sequence was individualised (Valeriano et al., 2000). A common feature of the clastic rocks from these units is the similarity

Acknowledgements

C. Valeriano acknowledges financial support from CNPq (proc. 471931/01-2) and UERJ/SR-1 and a postdoctoral grant from CAPES (BEX-1032/99-2). The Micromass Isoprobe instrument and the LambdaPhysik-Merchantek-New Wave laser system installed at the UQAM were financed through Natural Sciences and Engineering Research Council of Canada (NSERC) and contributions from FCAR (Québec) and Fondation UQAM. The laboratory is maintained in part with a NSERC MFA grant. A NSERC grant to N. Machado partly

References (54)

F.F.M Almeida et al.
The origin and evolution of the South American Platform
Earth Sci. Rev.
(2000)
M.C Campos Neto et al.
Tectonic constraint on Neoproterozoic high-pressure metamorphism and nappe system south of the São Francisco Craton, southeast Brazil
Precambrian Res.
(1999)
C.F Ferreira Filho et al.
Zircon and rutile U–Pb geochronology of the Niquelândia layered mafic and ultramafic intrusion, Brazil: constraints for the timing of magmatism and high grade metamorphism
Precambrian Res.
(1994)
I Horn et al.
Precise elemental and isotope ratio determination by simultaneous solution nebulization and laser ablation-ICP-MS: application to U-Pb geochronology
Chemical Geology
(2000)
K.R Ludwig
On the treatment of concordant uranium-lead ages
Geochim. Cosmochim. Acta
(1998)
N Machado et al.
Determination of $^{207} Pb /^{206} Pb$ ages on zircon and monazite by laser-ablation ICPMS and application to a study of sedimentary provenance and metamorphism in southeastern Brazil
Geochim. Cosmochim. Acta
(1996)
N Machado et al.
Ages of detrital zircon from Archean–Paleoproterozoic sequences: implications for greenstone belt setting and evolution of a Transamazonian foreland basin in Quadrilátero Ferrı́fero, SE Brazil
Earth Planet. Sci. Lett.
(1996)
N Machado et al.
U–Pb Geochronology of Central Ribeira belt
Precambrian Res.
(1996)
H Martin et al.
Crustal evolution in the early Archaean of South America: example of the Sete Voltas Massif, Bahia State, Brazil
Precambrian Res.
(1997)
A.P Nutman et al.
SHRIMP U–Pb zircon geochronology of Archaean granitoids from the Contendas-Mirante area of the São Francisco Craton, Bahia, Brazil
Precambrian Res.
(1993)

Barbosa, O., 1954. Évolution du geosynclinal Espinhaço. In: Congres Geologique Intern. 19, Alger, 1952. Comptes...

Braun, O.P., Martins, M., Oliveira, W.J. 1993. Continuidade das seqüências rifeanas sob a Bacia do São Francisco...

M.C Campos Neto et al.

Terrane accretion and upward extrusion of high-pressure granulites in the Neoproterozoic nappes of southeast Brazil: petrologic and structural constraints

Tectonics

(2000)

Chaves, A.O., Teixeira, W., Gonzalez, C., Correia Neves, J.M., 1997. K–Ar, Rb–Sr and Sm–Nd geochronology of the...

I.W.D Dalziel

Neoproterozoic-Paleozoic geography and tectonics: Review, hypothesis, environmental speculation

Geol. Soc. Am. Bull.

(1997)

Dardenne, M.A., 2000. The Brası́lia fold belt. In: Cordani, U.G., Milani, E.J., Thomaz Filho, A., Campos, D.A. (Eds.),...

M.A Fonseca et al.

Faixa Brası́lia Setor Setentrional: estilos estruturais e arcabouço tectônico

Revista Brasileira de Geociências

(1995)

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Magmatic cycles in Santos Basin (S.E. Brazil): Tectonic control in the temporal-spatial distribution and geophysical signature
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The Santos Basin, in the offshore southeastern Brazilian margin, evolved from a continental rift system to a passive divergent margin during the Cretaceous as a onsequence of the Gondwana breakup and the formation of the proto-Atlantic Ocean. The basin exhibits several cycles of magmatism from Valanginian to Eocene times, with a regionalized distribution of igneous rocks. Using seismic, gravity, magnetic, and wellbore data, the magmatic cycles were investigated and connected with the basin's tectonic activity. Our study includes a regional analysis of the various magmatic cycles, with a focus on identifying the temporal variations and spatial differences observed in the basin's many tectonic compartments. The first magmatic cycle, named rift-onset, is observed in both coastal and offshore regions and includes magmatic rocks from ca.135 to ca. 132/130 Ma. Onshore, the rift-onset magmatic rocks are observed in the coastal dike swarm province and in the coastal alkaline province. Offshore, the riftonset is observed as a prolongation of the coastal dike swarms into the proximal basin and as flood basalts in the distal basin. The second cycle includes the synrift (ca.132-130 to 123 Ma) and postrift (ca.123 to 113-112 Ma) magmatic rocks. The separation of intrusive synrift and postrift rocks is challenging in the onshore fieldwork and in the seismic analyses offshore, which is aggravated by the basin's scarcity of geochronological dating. Therefore, these two events have been treated together when the separation is not clear. The third cycle comprises the drift (or post breakup) magmatic rocks, spanning from the Lower Cretaceous to the Tertiary (from ca. 110 to ca. 40 Ma), and is well documented in coastal and offshore domains. Drift magmatism seems to be controlled by tectonics, since magmatic bodies tend to concentrate along lines of crustal discontinuities. Magmatic cycles (rift-onset, syn/postrift, and drift) also display spatial differences, exhibiting variation in the magmatic volume and in the morphology of igneous rocks from the southern to the central/northern Santos Basin. The study of magmatism in the, Santos Basin offers an excellent opportunity to investigate the processes that occurredduring the evolution of a volcanic rifted margin.
Subduction and continental collision in the Neoproterozoic: Sanukitoid-like magmatism and paired metamorphism in SE Brazil
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Collisional orogens are a periodic manifestation of plate tectonics on Earth. They form by the amalgamation of continental blocks, and they take place along both active and passive continental margins. The Neoproterozoic Southern Brasília Orogen is a collisional orogen related to the formation of West Gondwana, broadly composed of two tectonometamorphic domains, the Upper Tectonostratigraphic Domain (UTD), intruded by subduction-related magmas, and the Lower Tectonostratigraphic Domain (LTD) of passive margin affinity. New metamorphic zircon SHRIMP and LA-ICP-MS U-Pb ages are presented for rocks from both domains, a high-grade mylonitic orthogneiss (∼623 Ma) and a granulitic garnet-sillimanite-K-felspar metapelite (∼621 Ma) from the Upper Tectonostratigraphic Domain, and medium T retro-eclogites (∼616–610 Ma) and a garnet-kyanite-K-feldspar granulitic metapelite (∼615 Ma) from the Lower Tectonostratigraphic Domain. New and compiled U-Pb metamorphic ages, together with published P-T data, indicate the existence of Neoproterozoic coeval metamorphic belts in the Southern Brasília Orogen: an intermediate T/P region (LTD) and a high T/P domain (UTD). This is a characteristic of modern and ancient accretionary and subduction-to-collision orogens. The high T/P domain is dominated by Neoproterozoic sanukitoid-like magmatic rocks emplaced at the pre- to late-collsional stages (∼750–610 Ma) and the most primitive members of these suites (49–53 SiO₂ wt.%; #Mg 40–60) are enriched in both compatible and incompatible elements (i.e., Th, Ba, Sr, etc), a characteristic inherited from their subduction-metasomatized garnet-bearing mantle source. Relatively high heat-flux from the mantle to the crust, associated with magmatic activity, combined with heating by radioactive decay in response to crustal thickening, are responsible for ultra-high temperature metamorphism (UHT) in the UTD. Barrovian-style intermediate T/P metamorphism was attained in the Lower Tectonostratigraphic Domain at the same time, in response to crustal thickening.
Characterization of the inverted metamorphic gradient of the Passos Nappe (SE-Brazil) based on multiple geothermobarometers
2022, Journal of South American Earth Sciences
Inverted metamorphic gradients are recognized in several Proterozoic to Phanerozoic orogens. However, the mechanisms that are responsible for the formation of these gradients are still a matter of discussion. In the southern Brasília Orogen, an inverted metamorphic gradient is recorded in the Passos Nappe, that comprises a sequence of metasedimentary rocks with minor intercalations of tholeiitic metamafic rocks, metamorphosed under greenschist facies (biotite zone) at the bottom and high-pressure granulite facies at the top. This paper presents a detailed investigation of pressure and temperature conditions along the Passos Nappe by integrating conventional geothermobarometry in metamafic rock and single-trace elements geothermometry (Zr-in-rutile and Ti-in-quartz) in quartzite. Nine lithostratigraphic units are identified in the Passos Nappe, which are informally named A to I, from the bottom to top, adding up to a minimum thickness of 4.56 km. In mafic rocks, the increase of metamorphic conditions is indicated by: (1) chemical variation of amphiboles, from actinolite/edenitic hornblende in Unit C, to pargasitic hornblende in Units E and G, and Fe-pargasite in Units H and I; (2) plagioclase composition varying from An1-13 in Unit C, An15-27 in Unit D to andesine at upper units; and (3) occurrence of clinopyroxene from the top of Unit E upwards. Additional petrographic features in quartzite also corroborate these insights, such as: the increase of grain size of both quartz and rutile, from bottom to top; the morphology of rutile crystals; the mechanism of quartz recrystallization (subgrain rotation dominates in lower units while grain boundary migration dominates in upper units) and the occurrence of rutile needles in quartz in the upper units, which suggest a continuous gradient. Combined application of Zr-in-rutile and Ti-in-quartz geothermometers in quartzite provided the following average temperature and pressure values for each unit: 673 °C and 11.7 kbar for Unit E, 690 °C and 9.5 kbar for Unit G, 747 °C and 11.6 kbar for Unit H and 758 °C and 11.3 kbar for Unit I. Our data indicate that the Zr-in-rutile and Ti-in-quartz systems do not re-equilibrate in metamorphic conditions lower than 600 °C. The extrapolation of these results to the low-grade units indicate: 496 °C and 4.8 kbar at Unit A, 504 °C and 4.8 kbar at Unit B, 502 °C and 4.4 kbar at Unit C. The results obtained with the geothermometer hornblende-plagioclase and the geobarometer garnet-rutile-ilmenite-plagioclase-quartz in metamafic rocks yielded the following average values for each unit: 486 °C and 5.0 kbar at Unit C, 568 °C and 6.0 kbar at Unit D, 622 °C and 8.1 kbar at Unit E, 650 °C and 8.4 kbar at Unit G, 743 °C and 9.4 kbar at Unit H and 723 °C and 11.2 kbar at Unit I. Since the two geothermobarometric approaches are based on independent chemical systems, the results obtained represent robust estimates for the temperature and pressure conditions for the inverted metamorphic gradient of the Passos Nappe. Comparing the inverted metamorphic gradient at the Passos Nappe with classical occurrences at the Himalaya Orogen, it is possible to assume that both origins were similar, which probably involved isotherm inversion due to subduction, channel flow process associated with shear heating and transport of higher pressure rocks over low-pressure rocks by reverse ductile shearing.

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U–Pb geochronology of the southern Brası́lia belt (SE-Brazil): sedimentary provenance, Neoproterozoic orogeny and assembly of West Gondwana

Abstract

Section snippets

Introduction and objectives

The Tocantins Structural Province

Analytical procedures

Results

Serra Velha Granite

Northern segment

Provenance ages and implications

Acknowledgements

Earth Sci. Rev.

Precambrian Res.

Precambrian Res.

Chemical Geology

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Lithos

J. South Am. Earth Sci.

J. South Am. Earth Sci.

J. South Am. Earth Sci.

Geodynamics

Earth Planet. Sci. Lett.

J. South Am. Earth Sci.

Earth Planet. Sci. Lett.

Terrane accretion and upward extrusion of high-pressure granulites in the Neoproterozoic nappes of southeast Brazil: petrologic and structural constraints

Tectonics

Neoproterozoic-Paleozoic geography and tectonics: Review, hypothesis, environmental speculation

Geol. Soc. Am. Bull.

Faixa Brası́lia Setor Setentrional: estilos estruturais e arcabouço tectônico

Revista Brasileira de Geociências