DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

Navegar

Resultados da Pesquisa

Agora exibindo 1 - 10 de 22

Sedimentary provenance and role of tectonic inheritance on the control of the Macaúbas group, eastern margin of São Francisco Craton (SE Brazil).
(2021) Oliveira, Rosana Gonçalves; Martins, Maximiliano de Souza; Queiroga, Gláucia Nascimento; Souza, Maria Eugênia Silva de; Lana, Cristiano de Carvalho; Alkmim, Ana Ramalho; Silva, Marco Antônio Leandro da; Bueno, Cássio; Linhares, Davidson
The Neoproterozoic Macaúbas Group represents the precursor basin system of the Araçuaí–West Congo orogen, located in the southern margin of Sao ̃ Francisco Craton, and records a Tonian volcano-sedimentary succession, at the base, overlain by a Cryogenian sequence related to the Neoproterozoic global glacial event. Detailed strat- igraphic surveys along the Tonian units allowed the identification of two lithofacies associations related to al- luvial fan and braided river environments, while the three Cryogenian lithofacies associations indicate a glaciomarine environment associated with extensive tectonics that has evolved into a marine environment. The results show that the age spectra of the Tonian and Cryogenian units are similar, differing mainly for an increased peak in the Cryogenian sample in ca. 1.0 Ga, where the primary source is probably related to those magmatic rocks associated with the Stenian-Tonian extensional breakup of the Sao ̃ Francisco-Congo paleocontinent. The KS-Test shows that not all the Tonian samples are similar to each other, as in all the Cryogenian samples. The detailed stratigraphic and structural surveys associated with the geochronological U–Pb data allow us to interpret that the Tonian and the basal Cryogenian sequences were deposited in two episodes of an active intracontinental tectonic context related to fault reactivations along the WNW-ESE Pirapora aulacogen structures in superimposed basin-cycles, the middle-to late-Cryogenian sequences extrapolated the WNW-ESE boundaries while the basin local depocenter and its surroundings expanded to a large depocenter during the basin evolution.
Time and isotopic constraints for Early Tonian basaltic magmatism in a large igneous province of the São Francisco – Congo paleocontinent (Macaúbas basin, Southeast Brazil).
(2022) Souza, Maria Eugênia Silva de; Martins, Maximiliano de Souza; Queiroga, Gláucia Nascimento; Soares, Antônio Carlos Pedrosa; Dussin, Ivo Antonio; Castro, Marco Paulo de; Serrano, Paula
The Neoproterozoic Macaúbas basin (southeast Brazil) provides key hints to unravel the history of the São Francisco – Congo paleocontinent before its amalgamation as part of Gondwana. Among the several Proterozoic taphrogenic events and anorogenic igneous episodes documented for the São Francisco – Congo paleocontinent, Early Tonian event has been particularly focused on in the literature owing to the large production of bimodal (felsic-mafic) magmas now found in the Araçuaí (SE Brazil) – West Congo (SW Africa) orogenic system (AWCO) and neighboring cratonic regions. Aiming to examine the stratigraphic relations, timing and isotopic signatures of extensive basaltic magmatism related to the Macaúbas basin, we carried out detailed field, lithochemical, isotope (whole-rock Sm-Nd and Lu-Hf in zircon) geochemistry and zircon U-Pb geochronological studies on the Pedro Lessa suite and Planalto de Minas Formation, located in the central-western Araçuaí orogen. The studied Pedro Lessa suite consists of a series of mafic dikes that crosscut the lowermost units of the Macaúbas Group but not the Planalto de Minas Formation. The Pedro Lessa suite yielded zircon U-Pb ages between 951 ± 54 Ma and 939 ± 7 Ma. The Planalto de Minas Formation comprises volcaniclastic rocks crystallized at 889 ± 10 Ma, and sedimentary rocks with maximum depositional age of 867 ± 10 Ma. The lithochemical and isotopic datasets (Pedro Lessa dikes: εNd(t) = +0.60; εHf(t) = –22.21 to +4.66; Planalto de Minas volcanism: εNd(t) = +0.76 to +0.78; εHf(t) = − 19.27 to +10.03) indicate predominantly continental tholeiite and minor enriched MORB-type mantle magmas with variable amounts of crustal contamination. The (La/Sm)N ratios indicate a theoretical partial melting (1–7%) of the spinel-lherzoite lithospheric zone for the Pedro Lessa suite, and of the spinel-garnet transition zone (3–10%) for the Planalto de Minas metamafic rocks, in accordance with La/Nb and La/Ba ratios. The new and complied isotopic and lithochemical data suggest a time-dependent evolution of magma sources, with lithospheric mantle sources for the Early Tonian dike swarms (Pedro Lessa and correlatives) evolving to predominantly asthenospheric mantle sources for the late basaltic volcanism recorded in the Planalto de Minas Formation. Such an extensive and long-lasting anorogenic magmatism of Early Tonian age (c. 965 – 870 Ma) found in the AWCO and São Francisco – Congo craton likely records more than one extensional event and related aborted continental rifts, altogether driven by the same mantle plume. Although long-lived, this mantle plume acted beneath a strong continental lithosphere so that it was unable to break up the São Francisco – Congo paleocontinent into two completely separated landmasses. Highlighting the main stages of anorogenic magmatism, we also present an updated barcode for the São Francisco – Congo paleocontinent.
Depositional setting and U-Pb detrital record of rift‐related deposits in the Moeda Formation (Minas Supergroup) at the Gandarela and Ouro Fino synclines, Quadrilátero Ferrífero, Brazil.
(2021) Madureira, Rafael da Silva; Martins, Maximiliano de Souza; Queiroga, Gláucia Nascimento; Lana, Cristiano de Carvalho; Dutra, Luiz Fernandes; Alkmim, Ana Ramalho
The Moeda Formation (Caraça Group, base of Minas Supergroup) registers the initial rift stages of the Minas Basin in the Quadrilátero Fer- rífero, Southern São Francisco craton, SE-Brazil. We present stratigraphic and U-Pb detrital zircon dating analyses of the Moeda Formation that contribute to the comprehension of its sedimentary evolution in the southernmost Gandarela and Ouro Fino synclines (Central-Eastern Quadrilátero Ferrifero). The Moeda Formation sequence consists of a basal proximal alluvial fan with clast-supported conglomerates, grading upward into an alluvial floodplain with quartz arenites, and upper massive sandstones from distal fluvial fans. Because the Moeda Formation is normally limited by similar lithologies at both its base (Nova Lima Group, Rio das Velhas Supergroup) and top (Batatal Formation, upper- most Caraça Group) and stratigraphic inversion has occurred in the study area, U-Pb detrital zircon dating was also extended to these units to differentiate them stratigraphically. The youngest clusters of detrital zircon ages in the Nova Lima Group and Moeda and Batatal formations were 2716, 2777 and 2786 Ma, respectively. Based on our data and relevant literature, the depositional age of the Moeda Formation was interpreted as between 2716 and 2520 Ma with the Mesoarchean continental crust, the Rio das Velhas Supergroup and the Archean TTG complexes as its main source areas.
Detrital zircon records of the Paleo-Mesoproterozoic rift-sag Tamanduá group in its type-section, Northern Quadrilátero Ferrífero, Minas Gerais, Brazil.
(2020) Dutra, Luiz Fernandes; Dias, Sérgio Patusco; Martins, Maximiliano de Souza; Lana, Cristiano de Carvalho; Batista, Ana Carolina; Tavares, Túlio Delôgo
The Quadrilátero Ferrífero metallogenetic province is located in the southernmost portion of the São Francisco craton, SE Brazil. The Tamanduá and Cambotas ridges stand out topographically in the northeastern portion of Quadrilátero Ferrífero and show NE-SW and N-S directions, respectively. Those ridges involve metasedimentary rocks of the Tamanduá Group bounded by a fault system. Due to stratigraphic and structural complexities, there is little consensus about the maximum sedimentation age and the stratigraphic position in which Tamanduá Group sediments were deposited. In this work, we took advantage of the excellent exposures in the Tamanduá and Cambotas ridges to present detailed stratigraphic observations combined with U-Pb zircon geochronological data from samples of different stratigraphic levels of Tamanduá Group. Furthermore, we provide U-Pb data from samples of the intrusive Pedra Formosa Suite that cut the whole Tamanduá sequence in the study area. Our observations showed that the Tamanduá Group represents a rift-sag basin-fill succession developed along the eastern border of the São Francisco paleoplate. The basal metaconglomerate and metasandstone package grades upward into marine metasandstone and phyllite. Detrital zircon obtained from the basal unit, Antônio dos Santos Formation, reveals maximum depositional ages between ca. 1981 and 1770 Ma. The upper succession, Cambotas Formation, shows a maximum depositional age from 1769 to 1740 Ma. The Pedra Formosa Suite shows zircons that crystallized at ca. 1740 Ma. The stratigraphic framework and the Orosirian-Statherian ages suggest a correlation with the first rifting event within the São Francisco paleoplate, the precursor of Paleo- to Mesoproterozoic Espinhaço basin.
Provenance shift through time in superposed basins : from early cryogenian glaciomarine to late ediacaran orogenic sedimentations (Araçuaí Orogen, SE Brazil).
(2020) Castro, Marco Paulo de; Queiroga, Gláucia Nascimento; Martins, Maximiliano de Souza; Soares, Antônio Carlos Pedrosa; Oliveira, Leon Dias; Lana, Cristiano de Carvalho; Babinski, Marly; Alkmim, Ana Ramalho; Silva, Marco Antônio da
Records of Precambrian glaciation have been reported from southeastern Brazil for over a century. We present sedimentological, stratigraphic and isotopic (U-Pb and Lu-Hf on detrital zircons, C and O on carbonates) studies on diamictite-rich to diamictite-free successions of the Araçuaí Orogen, the Brazilian counterpart of the Araçuaí – West Congo Orogenic System (AWCO). From base to top, the Chapada Acauã Formation (Macaúbas Group) includes a diamictite-rich unit, with lenses of graded sandstone and clast-supported conglomerate, that gradually passes to graded sandstone, pelite with sparse oversized clasts and rare carbonate lenses on top, representing mass flow and turbidity current deposits of submarine fan, followed by finer-grained turbiditic sedimentation with iceberg discharges along fan fringes, from glaciomarine to post-glacial scenarios. The Salinas Formation comprises a deep-sea sand-mud sequence composed of pelites and pelitic wackes. The Chapada Acauã Formation was deposited in-between 750 and 667 Ma. It shows wide spectra of zircon ages (typical of continental rift to passive margin settings) that start around 3.2 Ga and display main age peaks indicating sediment provenance from the Rhyacian-Orosirian basement (εHf(t) = +14.6 to −18.5) and Early Tonian anorogenic rocks (950–880 Ma; εHf(t) = −3.2 to −23.2) for the diamictite-rich lower unit and, for the upper unit, also in Early Cryogenian anorogenic rocks (ca. 715 Ma, εHf(t) = −9.6). In contrast, the Salinas Formation shows most ages in-between 676 and 620 Ma and a maximum sedimentation age around 551 Ma, with εHf(t) from +6.9 to −18.2, unravelling an important shifting of sediment provenance to sources located in magmatic arcs and collisional granites of the Araçuaí and Ribeira orogens. The Early Cryogenian age and negative Hf signature for the glaciomarine Chapada Acauã Formation point to sediment sources in the 720–670 Ma anorogenic igneous rocks found in AWCO and adjacent Congo – São Francisco Craton, and suggest correlation with the Sturtian global glaciation.
Caracterização faciológica e evolução sedimentar da Formação Moeda (Supergrupo Minas) na porção noroeste do Quadrilátero Ferrífero, Minas Gerais.
(2019) Madeira, Mariana de Resende; Martins, Maximiliano de Souza; Martins, Gustavo Pereira; Alkmim, Fernando Flecha de
A Formação Moeda, ao longo da região noroeste do Quadrilátero Ferrífero, registra os primeiros estágios da Bacia Minas, desenvolvida no limite Neoarqueano/Paleoproterozoico no sul do Cráton do São Francisco (CSF). Este trabalho analisa essa unidade a partir de seis perfis estratigráficos de detalhe nos quais foram identificadas nove fácies sedimentares: quatro conglomeráticas (Gms, Gm, Gt e Gp), três essencialmente areníticas (St, Sp e Sh) e duas predominantemente pelíticas (Fl e Fsc). As seções estratigráficas foram correlacionadas, possibilitando o agrupamento das fácies em cinco associações geneticamente relacionadas. As associações de fácies AF1 e AF2 representam sistemas de leques aluviais que evoluíram para planícies fluviais entrelaçadas. AF3 está relacionada a um sistema lacustre associado a marinho raso nas porções distais. Por fim, as associações de fácies AF4 e AF5 representam planícies fluviais entrelaçadas encerradas por uma transgressão marinha no estágio final de evolução da bacia. Com o auxílio do mapeamento geológico-estrutural de detalhe dessas associações e da confecção de uma seção restaurada foi possível interpretar que as AF1, AF2, AF3 e a porção basal da AF4 foram depositadas durante os estágios iniciais do rifteamento continental, e as demais associações materializam a transição rifte-margem passiva.
An Early Tonian rifting event affecting the São Francisco-Congo paleocontinent recorded by the Lower Macaúbas Group, Araçuaí Orogen, SE Brazil.
(2019) Castro, Marco Paulo de; Queiroga, Gláucia Nascimento; Martins, Maximiliano de Souza; Alkmim, Fernando Flecha de; Soares, Antônio Carlos Pedrosa; Dussin, Ivo Antonio; Souza, Maria Eugênia Silva de
After it had been assembled in the very early Orosirian, the western São Francisco–Congo Paleocontinent experienced several rifting events since the Statherian (ca. 1750 Ma) to Cryogenian (ca. 700 Ma). Records of anorogenic magmatism and/or associated sedimentation from those events have been found in the Neoproterozoic Araçuaí–West Congo orogenic system (AWCO), located between the São Francisco (eastern Brazil) and Congo (central Africa) cratons. Based on detailed field studies and data from lithochemistry, zircon and titanite U-Pb dating, whole-rock Nd and Hf-in-zircon isotopic analyses, we characterize a previously poorly described Early Tonian, rift-related, volcano-sedimentary succession in order to decipher the evolution of the AWCO precursor basins. That volcano-sedimentary succession, found in the Capelinha Formation type-area, now assigned to the Lower Macaúbas Group, includes quartzites with lenses of ortho-amphibolite (metabasalt) covered by pelitic schists. Zircon grains from ortho-amphibolite samples yielded ages of 957 ± 14 Ma and 576 ± 13 Ma, constraining their magmatic crystallization and regional metamorphism, respectively. These mafic rock show ƐNd(t) from −3.64 to +0.21 and Nd TDM ages from ca. 1.4 to ca. 1.7 Ga. Positive covariation of FeOtot/MgO + FeOtot, TiO2, P2O5, V and Zr, enrichment in light rare earth elements, slightly positive Eu/Eu* anomaly and depletion of high field-strenght elements, suggest tholeiitic protolith related to a continental rifting setting. The metasedimentary rocks show broad spectra of detrital zircon ages from the Early Tonian (ca. 940 Ma) to Paleoarchean, with wide-ranging ƐHf values from predominantly negative (as low as −10.76) to positive (+9.94), evoking well-known sediment sources in the São Francisco–Congo Paleocontinent. The youngest age peak (949 ± 12 Ma) constrains a maximum sedimentation age coeval with the basaltic volcanism represented by the ortho-amphibolite. The Capelinha volcano-sedimentary succession nearly correlates in age and origin with other anorogenic units (e.g., Ilhéus and Pedro Lessa dike swarms, Salto da Divisa granitic suite, Gangila basaltic and Mayumbian felsic volcanisms) found in a large region covered by the AWCO and neighbouring cratonic region. However, the Capelinha magmatism seems to preceed by some 20–30 m.y. the main peak (930–900 Ma) of this Early Tonian anorogenic magmatism, suggesting a long-lived and complex rift system.
Paleoenvironment, sediment provenance and tectonic setting of Tonian basal deposits of the Macaúbas basin system, Araçuaí orogen, southeast Brazil.
(2019) Souza, Maria Eugênia Silva de; Martins, Maximiliano de Souza; Queiroga, Gláucia Nascimento; Leite, Mariana; Oliveira, Rosana Gonçalves; Dussin, Ivo Antonio; Soares, Antônio Carlos Pedrosa
The Neoproterozoic Macaúbas Group represents the main precursor basin system of the Araçuaí orogen, including a Tonian volcano-sedimentary succession, at the base, overlain by a Cryogenian sequence. Belonging to the Tonian succession, the Matão – Duas Barras Formation, exposed at the southern border of the Porteirinha basement block in the proximal (western) Araçuaí orogen, represents the very first stage of rifting ever recorded in the Macaúbas basin system. Sedimentological analysis on that formation has revealed two distinct and consecutive facies associations, both indicating half-graben sedimentary filling: i) fault-sourced alluvial fans; and ii) fluvial deposits associated with braided rivers. U-Pb ages of detrital zircon grains from the Matão – Duas Barras Formation and its underlain unit (ascribed to the Espinhaço Supergroup) uniformly show a dominant Rhyacian to Orosirian peak at ca. 2182 Ma – 1863 Ma, as well as several minor Archean age peaks from ca. 3186 Ma to ca. 2655 Ma. The Matão – Duas Barras fluvial deposits also show two Mesoproterozoic age clusters at ca. 1520 Ma and ca. 1156 Ma. Together with sedimentological features, the Archean and Paleoproterozoic zircon ages indicate sediment provenance from the granite-gneiss sources located in the neighboring Porteirinha block, which would have acted as a basement high (a large horst) at least during the initial filling of the Early Tonian Macaúbas rift. The ca. 1520 Ma and ca. 1156 Ma peaks are in good agreement with the Calymmian and Stenian development stages (II and III) of the Espinhaço Supergroup, which acted as an important secondary sediment sources for the basal Macaúbas Group. This also suggests that the Mesoproterozoic sources were exposed by the Porteirinha block uplift coeval with the Matão – Duas Barras basin filling. The maximum sedimentary ages given by the youngest zircon grains, together with a thorough literature compilation, bracket a depositional interval for the basal Macaúbas deposits from 1000 Ma to 933 Ma. Changes in sedimentary style and geochronological spectra suggest variations in the tectonic activity and subsidence rates of the Early Tonian Macaúbas basin, marking its first stage as an entirely siliciclastic sedimentation.
Detrital zircons from the Upper Três Marias Formation, São Francisco basin, SE Brazil : record of foreland deposition during the Cambrian?
(2020) Tavares, Túlio Delôgo; Martins, Maximiliano de Souza; Alkmim, Fernando Flecha de; Lana, Cristiano de Carvalho
The Bambuí Group, a succession of mixed carbonate and siliciclastic rocks, accumulated in the intracratonic and poly-historic São Francisco successor basin by the end of the Neoproterozoic. The São Francisco basin, which occupies a substantial portion of the eponymous craton in southeastern Brazil, was converted into a major foreland depocenter in response to orogenic loads generated along the craton margins during the assembly of West Gondwana in the Ediacaran Period. Various studies carried out in recent years have led to a better understanding of many aspects of the evolution of the São Francisco basin during the Neoproterozoic. However, the age of the Bambuí Group, critical for a better understanding of the basin history and establishment of regional and global correlations, remains poorly constrained and matter of a long-standing debate in the literature. In order to contribute to this debate, we performed U-Pb LA-ICPMS age determinations on detrital zircons extracted from the Três Marias Formation, the youngest unit of the group. Our study, based on a stratigraphic survey, was conducted in an occurrence of the formation located near to the eastern border of the basin, i.e., in a proximal position in relation to its potential source, the Brasiliano Araçuaí orogen. The detrital zircon age spectra (involving 432 concordant ages) of the lower alluvial and upper marine units of the Três Marias Formation are characterized by a unimodal distribution with c.83% of the grains dated between 735 and 522 Ma. These results indicated that lithostratigraphic assemblages of the Araçuaí orogen, namely the 630-580 Ma granitoids of Rio Doce magmatic arc and 585-540 Ma syn-collisional granites were the most important sources of the Três Marias sediments. Moreover, post-collisional granite suites younger than 530 Ma also contribute with sediments to the formation. Using four different metrics, we obtained 527 ± 4 Ma as the most accurate and reliable estimation for maximum depositional age of the Upper Três Marias Formation, an age that has major implications for the developmental history of both the São Francisco basin and Araçuaí orogen
Sedimentary and U-Pb detrital zircons provenance of the Paleoproterozoic Piracicaba and Sabará groups, Quadrilátero Ferrífero, Southern São Francisco craton, Brazil.
(2019) Dutra, Luiz Fernandes; Martins, Maximiliano de Souza; Lana, Cristiano de Carvalho
The Quadrilátero Ferrífero is an important mineral province located in Southern São Francisco craton, SE Brazil. Its prominent feature is the Gandarela syncline that was formed as part of the regional deformation event in the southernmost part of the craton at ca. 2,000 Ma. The syncline exposes several economically important units of Rio das Velhas and Minas supergroups, widely known for their gold and iron ore mineral deposits. This work focused on the upper Minas Supergroup — Cercadinho Formation and Sabará Group in the Gandarela syncline. We showed detail stratigraphic surveys combined with U-Pb detrital zircon analysis. Data reveal the development of high- to low-density turbidity systems. The first one is related to the deposition of Cercadinho Formation that marks the siliciclastic infilling of the Minas basin. For the Sabará Group, a fine turbidite system of foredeep depocenter is inferred. The detrital zircon analysis indicates that their sediments were derived from Archean, Rhyacian, and Orosirian exhumed terrains, besides granitoids positioned to the south and east of Quadrilátero Ferrífero. We proposed the age of 2,036 ± 25 Ma as the maximum age of deposition of Sabará Group, whose sedimentation occurs in the first stages of Minas accretionary orogeny

DEGEO - Departamento de Geologia

Navegar

Filtros

Configurações

Ordenar por

Resultados por página

Resultados da Pesquisa