Servico Geologico do Brazil

Belo Horizonte, Brazil

Servico Geologico do Brazil

Belo Horizonte, Brazil

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Adorno R.R.,Servico Geologico do Brazil | Do Carmo D.A.,University of Brasilia | Salas M.J.,National University of Cordoba | Zabini C.,University of Campinas | Assine M.L.,São Paulo State University
Revista Brasileira de Paleontologia | Year: 2016

Two species of Ostracoda are described for the first time from the parastratotype-section of Vila Maria Formation; this section is 30 m thick, located on the northern border of the Paraná Basin. The Vila Maria Formation records the Upper Ordovician-Lower Silurian boundary of the Paraná Basin in Bom Jardim de Goiás, State of Goiás, central Brazil. The new species represents the earliest Ostracoda occurrence from Brazilian strata. Delicate internal and external molds of isolated valves are abundant in the basal portion of the parastratotype-section of Vila Maria Formation. This interval comprises black shales that record post-glacial marine transgression, overlapping the Upper Ordovician glacial sequence of the Iapó Formation. The paleogeographic reconstruction indicates that deposition of the basal portion of the Vila Maria Formation took place in high-latitude, cool water conditions at the margin of Gondwana, under similar environmental conditions to the Djeffara Formation in the Ghadames Basin and the Tichitt Group in the Taoudeni Basin, both in the Northern Africa. © 2016 by the Sociedade Brasileira de Paleontologia.

Pedrosa-Soares A.C.,Federal University of Minas Gerais | de Campos C.P.,LMU Theresienstrasse 41 III | Noce C.,Federal University of Minas Gerais | Silva L.C.,Servico Geologico do Brazil | And 8 more authors.
Geological Society Special Publication | Year: 2011

The Araçuaí orogen extends from the eastern edge of the São Francisco craton to the Atlantic margin, in southeastern Brazil. Orogenic igneous rocks, formed from c. 630 to c. 480 Ma, cover one third of this huge area, building up the Eastern Brazilian Pegmatite Province and the most important dimension stone province of Brazil. G1 supersuite (630-585 Ma) mainly consists of tonalite to granodiorite, with mafic to dioritic facies and enclaves, representing a continental calc-alkaline magmatic arc. G2 supersuite mostly includes S-type granites formed during the syn-collisional stage (585-560 Ma), from relatively shallow two-mica granites and related gem-rich pegmatites to deep garnet-biotite granites that are the site of yellow dimension stone deposits. The typical G3 rocks (545-525 Ma) are non-foliated garnet-cordierite leucogranites, making up autochthonous patches and veins. At the post-collisional stage (530-480 Ma), G4 and G5 supersuites were generated. The S-type G4 supersuite mostly consists of garnet-bearing two-mica leucogranites that are the source of many pegmatites mined for tourmalines and many other gems, lithium (spodumene) ore and industrial feldspar. G5 supersuite, consisting of high-K-Fe calc-alkaline to alkaline granitic and/or charnockitic to dioritic/noritic intrusions, is the source of aquamarine-topaz-rich pegmatites but mainly of a large dimension stone production. © 2011 Geological Society of London.

The Iricoumé group consists of very well preserved pyroclastic and effusive volcanic rocks as a part of an extensive volcano-plutonic event, which marked the central part of the Amazonian craton during the Orosirian. Such rocks occur in the southern part of the southwestern of Erepecuru-Trombetas Domain (NW of the Pará state), south of the Guyana Shield. Petrographic study allows distinction of two volcanic types. A dominant explosive volcanism is characterized by pyroclastic rocks (ignimbrites, rheoignimbrites, lapilli-tuff related to surge deposit, and co-ignimbrite fall tuff) while a subordinated effusive volcanism is represented by coherent lavas flows and hypabissal rocks (andesites, lamprophyres and latites). Most of the pyroclastic rocks exhibit features of deposition under high temperature suggesting formation in a caldera-related environment. Pb-Pb zircon ages of 1888 ± 2.5 and 1889 ± 2 Ma have been obtained for the formation of trachydacitic ignimbrites and confirm that the dominant volcanism is part of the Iricoumé group. The Pb-Pb zircon age of 1992 ± 3 Ma yielded by an andesite points to the occurrence in the area of an older Orosirian magmatic episode, which has been previously recognized locally southward in the Tapajós domain. These new results constitute a further evidence of the wide extent of the Iricoumé group and correlated volcanic rocks in the central part of the Amazonian craton, and reinforce the assumption that this volcanic episode and correlated magmatism may be considered as a silicic large igneous province (SLIP), as previously proposed by some authors.

De Souza Marinho M.,Servico Geologico Do Brazil | De Souza Marinho M.,Federal University of Ouro Preto | De Souza Gomes C.J.,Federal University of Ouro Preto
Brazilian Journal of Geology | Year: 2013

Structural and microstructural studies have been carried out to assess the structural evolution of Au, Ag and Pb lode occurrences that spread among Serrita and Parnamirim municipalities, Pernambuco, Brazil. These occurrences are hosted in metassediments, correlated to the Salgueiro Group, and granodiorites from Serrita Suite, in the Piancó-Alto Brígida Domain, southwestern Zona Transversal, Borborema Province. The metassediments underwent four deformation phases that switched from compressional to strike-slip tectonics. The first two phases developed a low-angle fabric and the third and fourth ones produced folds with NE-SW/ENE-WSW plane-axial crenulation cleavages and regional shear zones, respectively. In the metassediments, the veins grew by E-W and N-S/NNW-SSE branched fractures, associated with rapid propagation and dilatation. These veins underwent new mineral crystallization phases concomitant with deformation and mineralization, which mark the transition from the ruptile-ductile to the ruptile regime. The granodiorite hosted-veins show incipient deformation, as do theirs hosts. We conclude that the veins, in both host-rocks, formed by the same stress field attributed to the end of fourth phase, under a NW-SE maximum compressive tensor. The differences between the veins resulted from a fracture refraction in function of rheological contrasts in the host-rocks. This refraction induced the development of E-W/ESE-WNW and N-S/NNW-SSE shear fractures in the less competent lithology, the metassediments, and NW-SE tensile fractures in the more competent one, the granodiorite.

Moreira D.M.,Servico Geologico do Brazil | Moreira D.M.,Federal University of Rio de Janeiro | Moreira D.M.,University Paul Sabatier | Calmant S.,Institute Of Recherche Pour Le Developpement | And 5 more authors.
Geophysical Research Letters | Year: 2016

In large hydrological basins, water mass loading can produce significant crustal deformation. We compare the monthly vertical component of 18 GPS sites located in the Amazon basin, with the deflection models derived from Gravity Recovery and Climate Experiment (GRACE) observations on the one hand and derived from HYDL, a global hydrological model, on the other hand. The GPS data set includes the largest deflections by hydrological loading ever recorded at two stations located in the center of the basin. The main result of the study is that the GRACE solution produced by GRGS (Groupe de Recherche en Géodesie Spatiale, Toulouse, France) produces the best agreement with the Global Navigation Satellite Systems series with a correlation coefficient up to 0.9 in the center of the basin, although 70% at best of the RMS variation in the GPS series is accounted for. ©2016. American Geophysical Union. All Rights Reserved.

De Brito Neves B.B.,University of Sao Paulo | Van Schmus W.R.,University of Kansas | Angelim L.A.A.,Servico Geologico do Brazil
Geologia USP - Serie Cientifica | Year: 2015

The Riacho do Pontal System (RPS) is just the central part of a long Neoproterozoic orogenic development placed at the northern periphery of the São Francisco Craton (SFC), from northeast (Sergipano belt) to southwest (Rio Preto belt). The basement of the foreland (SFC) and the backland ("Morro do Estreito-Icaiçara") is mostly formed by Archean rocks, with some insertions of supracrustal and orthogneisses of Tonian age (Cariris Velhos cycle?). RPS exhibits a remarkable tectonic-metamorphic zoning from north to the south: the backland; the internal zone (supracrustal terrigenous assemblages); the central zone (ocean floor rock assemblages); the external zone (supracrustal terrigenous assemblages); and the cratonic domain (SFC), remarked by the presence of a wide (> 200 km) foreland thrust and fold belt (to the south), formed by the Neoproterozoic pelitic-carbonatic cratonic cover. The processes of deformation were intense, presenting vergence towards south and southwest, resulting in reclined and overturned folds, reverse and thrust faults, nappes, and specially the occurrences of some klippen over the basement of the northern part of the CSF. The regional metamorphism was undertaken under amphibolite conditions, with some local retrogression to the greenschists facies. This paper presents a series of new geochronological determinations (Rb-Sr, Sm-Nd and U-Pb methods) of practically all rock types of the basement, supracrustals, and of the associated syncollisional granites. It was possible to discriminate some Archean nuclei (2740 - 2624 Ma), as basement (backland), and two different set of Neoproterozoic volcano-sedimentary rock units associated with granites, the first one of Eotonian age (980 - 940 Ma) and the second one positioned in the Cryogenian-Ediacaran boundary (ca. 635 Ma). A preliminary essay of "wilsonian" tectonic evolution is here introduced for this south-western portion of the Borborema Province (the regional branching system of orogens). © 2015, Universidade de Sao Paulo. All rights reserved.

Barreto C.J.S.,Federal University of Pará | Lafon J.M.,Federal University of Pará | Da Rosa Costa L.T.,Servico Geologico Do Brazil | Lima E.F.,Federal University of Rio Grande do Sul
International Geology Review | Year: 2014

Hypabyssal and explosive volcanic rocks of the Iricoumé Group crop out in the Western Erepecuru-Trombetas Domain, in the Central Amazonian Province, south of the Guyana Shield. They are part of an extensive volcano-plutonic event, which marked the central part of the Amazonian Craton during the Orosirian. These volcanic rocks, formed at approximately 1.89 Ga, consist of pyroclastic rocks (ignimbrites, rheoignimbrites, surge-related lapilli-tuff, co-ignimbrite fall tuff) and subordinate felsic hypabyssal rocks. An older episode, with an age of approximately 1.99 Ga, occurs locally and is represented by latitic lava flows and spessartitic lamprophyres. The geochemical characteristics of the Iricoumé volcanic rocks suggest that they formed in a post-orogenic tectonic setting, while those of the older Orosirian magmatism suggest a subduction-related geodynamic setting. TDM model ages ranging from 2.18 to 2.39 Ga and slightly negative εNd(T) values for most of the Iricoumé volcanic rocks indicate dominant Rhyacian crustal sources for the parental magmas. The positive εNd(T) values exhibited by some Iricoumé rhyolites (TDM: 1.98 and 2.06 Ga) and by the 1.99 Ga lava flows and lamprophyre (TDM: 2.13 and 2.21 Ga) suggest a juvenile mantle source, although a minor contribution of Palaeoproterozoic crust cannot be ruled out. These new results furnish further evidence of the wide extent of the Iricoumé Group and coeval volcano-plutonic associations in the central part of the Amazonian Craton. © 2014 © 2014 Taylor & Francis.

Antonietto L.S.,University of Brasilia | do Carmo D.A.,University of Brasilia | Viviers M.C.,Petrobras | Adorno R.R.,Servico Geologico do Brazil
Revista Brasileira de Paleontologia | Year: 2015

A biostratigraphic and paleozoogeographic revision of the upper Aptian-Albian ostracods of Riachuelo Formation, in the Sergipe-Alagoas Basin, Brazil, was conducted. The studied material comprised 336 samples from several outcrops, along with well cores drilled by Petróleo Brasileiro S.A. (PETROBRAS). After taxonomic analysis, including the description of Reticulocosta edrianae n. sp., a new biozonation scheme was obtained for the Albian interval of that formation, and the paleozoogeographic affinities of the Brazil-Central West Africa province were reviewed through comparison with results published in the current literature. Several changes were made to previously established ostracod zones. A new code for the Aracajuia benderi Zone (OSE-1), MSA-0, was created, with impact in all of its subzones. The names of the Pattersoncypris ex. gr. angulata (OSE-1.1), ‘Patellacythere’ sp. GA E 27 (OSE-1.3) and Veenia guianensis (OSE-1.4) subzones were changed to Harbinia sinuata? (MSA-0.1), Praebythoceratina amsittenensis (MSA-0.3) and Reticulocosta edrianae (MSA-0.4), respectively. The Sergipella viviersae Subzone (OSE-1.2) had its code changed for MSA-0.2; also, a stratotype was stablished for it, and the lower limit of the subzone was changed, from lower Albian in previous works to upper Aptian. The Metacytheropteon aff. Metacytheropteron sp. GA C 24 Subzone (OSE-1.5) was renamed MSA-0.5. The uppermost Albian Aracajuia antiqua Latest Occurrence Interval Zone (MSA-1) is herein proposed, following the reclassification Aracajuia benderi specimens of the Aracajuia benderi Subzone (OSE-1.6) to Aracajuia antiqua. Paleozoogeographic analyses showed some faunal interchange with Tethyan provinces, beginning in the latest Aptian, at both specific and generic levels. Limited northward marine influxes across the Walvis ridge were also observed during the Albian, while larger scale southward migrations occurred in the early Cenomanian. The presence of Brachycytherinae species in the Brazil-Central West Africa province as early as the Aptian indicates a new zoogeographic origin for this subfamily, while explaining the occurrence of the group in both the Austral realm and part of the Tethyan realm during the Albian. © 2015 by the Sociedade Brasileira de Paleontologia.

Fabiano K.C.,Brazilian Nuclear Energy Research Institute (IPEN) | Lima A.P.S.,Servico Geologico do Brazil | Vasconcellos M.B.A.,Brazilian Nuclear Energy Research Institute (IPEN) | Moreira E.G.,Brazilian Nuclear Energy Research Institute (IPEN)
Journal of Radioanalytical and Nuclear Chemistry | Year: 2016

Controlling seafood quality is essential to ensure its safety for human consumption. Nevertheless, scarce information is available about seafood contaminant status in complex metropolitan markets in Latin America. Essential and toxic elements were determined in some of the most consumed fish species in São Paulo city, Brazil. Instrumental Neutron Activation Analysis was applied for the determination of As, Br, Co, Cs, Fe, K, Na, Rb, Se and Zn while Cd, Pb and Hg were determined by Atomic Absorption Spectrometry. Mass fraction results were higher than allowed values for some elements in some fish species, especially As. However, it was not possible to affirm that the fish consumed in São Paulo city presents risk to human health. © 2016 Akadémiai Kiadó, Budapest, Hungary

PubMed | Servico Geologico do Brazil, Federal Rural University of Pernambuco and Regional University of Cariri
Type: Journal Article | Journal: Anais da Academia Brasileira de Ciencias | Year: 2016

The Romualdo Member of the Santana Formation, a lithostatigraphic unit attributed to a marine intrusion, is famous for its preserved fossils in calcareous concretions, which stand out for their diversity and excellent preservation levels. This paper aims to record the first occurrence of the Class Insecta in the Romualdo Member of the Santana Formation of the Araripe Basin, as well as to describe and discuss the paleo-ecological implications of such finding. The first occurrence of the order Orthoptera (family Gryllidae) is presented for this unit. This new species is attributed to the genus Araripegryllus, that lasted throughout the deposition of the Crato Member, which is under the Romualdo Member. In reference to its statigraphic origin, the specimens was named Araripegryllus romualdoi sp. nov.

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