Rio de Janeiro, Brazil
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Heinonen A.P.,University of Helsinki | Fraga L.M.,CPRM | Ramo O.T.,University of Helsinki | Dall'Agnol R.,Federal University of Pará | And 2 more authors.
Lithos | Year: 2012

The ca. 1525Ma igneous Mucajaí anorthosite-monzonite-granite (AMG) complex in northern Brazil is a rare manifestation of Mesoproterozoic intraplate magmatism in the northern Amazonian Craton. The complex comprises a two-phase rapakivi granite batholith with subordinate quartz-fayalite monzonites and syenites and the closely associated Repartimento anorthosite. Zircon U-Pb (ID-TIMS) geochronology reveals that the anorthosite (1526±2Ma), monzonite (1526±2Ma), and the main-phase biotite-hornblende granite (1527±2Ma) of the complex intruded the Paleoproterozoic (~1.94Ga) country rocks simultaneously at ~1526Ma and that the more evolved biotite granite is marginally younger at 1519±2Ma. Intraplate magmatism in the Mucajaí region was relatively short-lived and lasted 12million years (1529-1517Ma) at maximum. The Nd (whole-rock, ID-TIMS; ε Nd from -1.9 to -2.8), Hf (zircon, LAM-ICP-MS; ε Hf from -2.0 to -3.1), and O (zircon, SIMS; δ 18O from 6.1 to 7.0) isotopic compositions of the studied rocks are fairly uniform but still reveal a small degree of isotopic heterogeneity in the Paleoproterozoic crust enclosing the complex. The small isotopic differences observed in the two types of rapakivi granites (biotite-hornblende granite and biotite granite) may result either from an isotopically heterogeneous lower crustal source or, more likely, from contamination of the granitic magma derived from a lower crustal source during prolonged residence at upper crustal levels. © 2011 Elsevier B.V.

PubMed | CPRM, GeoHyd, Bureau de Recherches Géologiques et Minières, University of Sao Paulo and 2 more.
Type: | Journal: Journal of contaminant hydrology | Year: 2016

In a context of increasing land use pressure (over-exploitation, surface-water contamination) and repeated droughts, identifying the processes affecting groundwater quality in coastal megacities of the tropical and arid countries will condition their long-term social and environmental sustainability. The present study focuses on the Brazilian Recife Metropolitan Region (RMR), which is a highly urbanized area (3,743,854 inhabitants in 2010) on the Atlantic coast located next to an estuarial zone and overlying a multi-layered sedimentary system featured by a variable sediment texture and organic content. It investigates the contamination and redox status patterns conditioning potential attenuation within the shallow aquifers that constitute the interface between the city and the strategic deeper semi-confined aquifers. These latter are increasingly exploited, leading to high drawdown in potenciometric levels of 20-30m and up to 70m in some high well density places, and potentially connected to the surface through leakage. From a multi-tracer approach (major ions, major gases, (11)B, (18)O-SO4, (34)S-SO4) carried out during two field campaigns in September 2012 and March 2013 (sampling of 19 wells and 3 surface waters), it has been possible to assess the contamination sources and the redox processes. The increasing trend for mineralization from inland to coastal and estuarial wells (from 119 to around 10,000S/cm) is at first attributed to water-rock interactions combined with natural and human-induced potentiometric gradients. Secondly, along with this trend, one finds an environmental pressure gradient related to sewage and/or surface-channel network impacts (typically depleted (11)B within the range of 10-15) that are purveyors of chloride, nitrate, ammonium and sulfate. Nitrate, ammonium and sulfate (ranging from 0 to 1.70mmol/L, from 0 to 0,65mmol/L, from 0.03 to 3.91mmol/L respectively are also potentially produced or consumed through various redox processes (pyrite oxidation, denitrification, dissimilatory nitrate reduction to ammonium) within the system, as is apparent within a patchwork of biogeochemical reactors. Furthermore, intensive pumping in the coastal area with its high well density punctually leads to temporary well salinization ([Cl] reaching temporarily 79mmol/L). Our results, summarized as a conceptual scheme based on environmental conditions, is a suitable basis for implementing sustainable management in coastal sedimentary hydrosystems influenced by highly urbanized conditions.

Rodrigues M.C.N.D.L.,Federal University of Paraná | Trzaskos B.,Federal University of Paraná | Lopes A.P.,CPRM
Journal of Structural Geology | Year: 2015

This study presents a qualitative and quantitative analysis of porosity in deformation bands by applying X-ray micro-computed tomography in conjunction with microstructural analysis. Samples of compactional cataclastic bands and shear compactional bands identified in Early Cretaceous aeolian sandstones of the Paraná Basin were analyzed. The application of X-ray micro-computed tomography expanded the view of features in the porous framework of each type of deformation band studied and provided information that are not clear or was not observable with optical microscopy. The compactional cataclastic bands and shear compactional bands differ in geometry, thickness, microstructures and, mainly, in the distribution, shape and orientation of the remaining pores. Porosity analysis was also performed by comparing values of porosity (total, open and closed pores) of the parental rock and the deformation band in each sample. Results of these analyses show a reduction of total porosity and open pores and therefore an increase in the amount of closed pores in all types of deformation bands in relation to parental rock. In addition, it is observed that changes in porosity characteristics are related to the effect of different deformation mechanisms that operated in each type of deformation band. © 2015 Elsevier Ltd.

Jacques P.D.,CPRM | Jacques P.D.,University of Sao Paulo | Machado R.,University of Sao Paulo | Nummer A.R.,Federal Rural University of Rio de Janeiro
Pesquisas em Geociencias | Year: 2010

This paper presents the study of structural lineaments in part of the state of Santa Catarina, Brazil. The study area comprises Paleoproterozoic and Neoproterozoic rocks, as well as different stratigraphic units of the Paraná Basin (Paleozoic and Mesozoic). The lineaments were interpreted from the digital analysis of LANDSAT satellite images and shaded relief images generated from the SRTM project, with the use of geoprocessing technologies. The data obtained from the LANDSAT and SRTM project were effective in the identification of brittle lineaments for the scales 1:100,000 and 1:500,000. The application of this methodology shows that the trends of these structural lineaments, grouped in domain lithologies, depend on the kind of remote sensor images. The results of rose diagrams obtained from the images of the Project SRTM do not follow the same pattern according to the scale adopted. For the final analysis, the two sets of obtained lineaments (LANDSAT and SRTM) were merged. The main patterns of orientations observed are distributed in three main systems: NW-SE, NS ± 5 and NE-SW. The lineament analysis according the lithologic domains shows that main direction do not vary, taking into account different scale products. An exception is the Serra Geral Formation, in the 1:100,000 scale, that highlights the NE-SW direction. The analysis of lineaments on the 1:500,000 scale, for the area corresponding to the Catarinense Shield, shows preferential NS ± 5° directions. The Paleozoic and Mesozoic structures are preferentially oriented in NW-SE direction and secondary NS ± 5° direction. In the region of the Lages Dome, a few lineaments were identified on the lithologic sedimentary units of Itararé and Guatá groups. In general, the intensity and density of the lineaments on the 1:100,000 scale are present in lithologic groups. This demonstrates that, for the identification of shallow structures, this scale is more appropriate.

Pinto V.M.,Federal University of Rio Grande do Sul | Hartmann L.A.,Federal University of Rio Grande do Sul | Wildner W.,CPRM
International Geology Review | Year: 2011

Native copper is widespread in the Lower Cretaceous Parana basaltic province, southern Brazil, both as films in fractures and as massive balls in amygdules. The focus of this investigation is on the large concentration of occurrences (n = 85) that forms the Vista Alegre district in the border region of Rio Grande do Sul and Santa Catarina states. The high average of 220 ppm Cu content of the basalts resulted in ore of native copper, Cu oxides, abundant chrysocolla in the top of mineralizations, and minor malachite and azurite. Native copper is associated with dioctahedral and trioctahedral smectites, zeolites (heulandite and clinoptilonite), quartz, and calcite, typical of a low-T (100-150C) hydrothermal alteration assembly. The PGE distribution shows enrichment in Pd in relation to Pt both in basalts and in native copper, supporting the hypothesis of hydrothermal origin of the mineralization. No evidence was found of direct precipitation of copper from the lava; based on field and petrographic evidence, integrated with BSE images, EPMA analyses, EGP contents of native copper, and bulk rock analyses, this is an epigenetic hydrothermal copper mineralization, followed by supergene enrichment. © 2011 Taylor & Francis.

Fuck R.A.,University of Brasilia | Dantas E.L.,University of Brasilia | Pimentel M.M.,University of Brasilia | Botelho N.F.,University of Brasilia | And 5 more authors.
Precambrian Research | Year: 2014

The Natividade-Cavalcanti crustal block is a Paleoproterozoic sialic terrain which forms the basement of sedimentary sequences belonging to the Neoproterozoic Brasília Belt in central Brazil. Two main domains were recognized in this crustal block, the limits of which are not well constrained due to the lack of geological maps at an appropriate scale. The northeastern domain is characterized by narrow supracrustal belts which wrap around gneiss domes. At least three rock-forming events are recorded in the calc-alkaline, metaluminous basement gneisses of this domain: (i) in the Almas-Dianópolis area, granitoids were dated at c. 2.2Ga, (ii) early Paleoproterozoic magmatism was dated at c. 2.3-2.4Ga in the Natividade-Conceição do Tocantins area, and (iii) younger additions were dated at 2144±21Ma. TDM model ages range between 2.24 and 3.11Ga, and e{open}Nd(t) values range from +2 to close to zero, suggesting juvenile sources. Bordering this domain west- and southwards, extending from Cavalcante to Arraias, Paranã and Pindorama do Tocantins, mostly peraluminous granitoids of the Aurumina Suite are exposed. Geochronological data for Aurumina granitoid rocks of this sector point to magmatic events between 2.13 and 2.18Ga, whereas TDM model ages range between 2.21 and 2.92Ga with generally negative e{open}Nd(t) values. An exception is a largely undeformed tonalite sample from close to Arraias, dated at 2042±12Ma. © 2014 Elsevier B.V.

De Sousa Gorayeb P.S.,Federal University of Pará | Chaves C.L.,CPRM | Moura C.A.V.,Federal University of Pará | Da Silva Lobo L.R.,ANP Agencia Nacional do Petroleo
Journal of South American Earth Sciences | Year: 2013

In north-central Brazil, a number of granite plutons, which intrude Paleoproterozoic gneiss-granulite terrains of the Goiás Massif, crop out along a thermal axis parallel to the Transbrasiliano Lineament. Single zircon lead evaporation ages from three granitic bodies span between 552 and 545Ma. Sm-Nd model ages (TDM) vary between 2.1 and 1.7Ga and negative εNd(0.55 Ga) values between -10 and -13 show that Paleoproterozoic crust was involved in the genesis of these granites. These plutons, which form the Lajeado Intrusive Suite are part of an important Ediacaran magmatic event in central-northern of the Tocantins Tectonic Province, composed of metaluminous to slightly peraluminous granites with geochemical characteristics similar to A-type granites, whose crystallization occurred under low water activity during magmatic emplacement. The granitic intrusive bodies are related to a crustal extensional/transtensional tectonic event at the end of the Neoproterozoic. They may have connection with the granitic plutons of similar age (0.56-0.52Ga) in northwestern Ceará state, on the other side of the Paleozoic Parnaíba Basin in northwest of Borborema Province, along the Transbrasiliano Lineament. © 2013 Elsevier Ltd.

PubMed | Federal University of Fluminense and CPRM
Type: Journal Article | Journal: Environmental monitoring and assessment | Year: 2016

The mangrove crab Ucides cordatus is widespread in the Brazilian coast, which has an important role in nutrient cycling. This species reproduces in summer and females carry eggs about a month, when they maintain contact with water and sediments. It remains unclear if trace metals can be absorbed or adsorbed by the eggs during development. The present study aims to investigate, for the first time, trace metal concentrations in ovigerous female tissues and eggs of U. cordatus in two areas with different metal pollution levels in the Southeastern Brazil. Samples were collected in two different mangroves, Guanabara Bay (GB) highly polluted environment and Paraba do Sul River (PSR). In both populations, we observed significant increase of V, Cr, and Mn concentrations along eggs maturation. The higher metals averages were found in PSR population. This trend was reported since the 1990s and lower concentrations in GB marine organisms were attributed to reducing conditions, high organic load, and the presence of sulfide ions. These conditions restrict the bioavailability of metals in the bay, with exception of Mn. No significant differences were observed in gills and muscles. In both populations of the present study, V, Zn, As, and Pb were higher in eggs of initial stage, whereas Mn, Ni, Cu, and Cd were higher in hepatopancreas. Beside this, V, Cr, Mn, As, and Pb showed an increase concerning egg development. Thus, V, As, and Pb in eggs come from two sources previous discussed: females and environment. Zinc came mainly from females due to essential function. Those new information should be considered as one of the mechanisms of trace metal transfer to the trophic chain, between benthonic and pelagic environment.

Rodrigues J.B.,CPRM | Rodrigues J.B.,University of Brasilia | Pimentel M.M.,University of Brasilia | Dardenne M.A.,University of Brasilia | Armstrong R.A.,Australian National University
Journal of South American Earth Sciences | Year: 2010

The Brasília Belt is one of the best preserved Neoproterozoic orogens in Brazil. It comprises a thick Meso-Neoproterozoic sedimentary/metasedimentary pile including the Canastra and Ibiá Groups, which are the object of this study. The Canastra Group constitutes a regressive sedimentary sequence made mainly of greenschist-facies metapelitic and metapsammitic rocks, including phyllite, sandy metarhythmite and quartzite, with minor intercalations of limestone, as well as carbonaceous and carbonatic phyllite. The Ibiá Group is formed of a basal diamictite followed upwards by phyllites and calc-schists. It rests on an erosional unconformity on top of the Canastra Group. A provenance study based on U-Pb zircon geochronology on a selection of seven samples helped to establish the various source areas and maximum depositional ages of the original sediments. In addition, seven new Sm-Nd analyses are presented and discussed together with previously published data. LAM-ICP-MS U-Pb dating of detrital zircon grains indicates a maximum depositional age of the Canastra and Ibiá Groups of ca. 1030 and 640 Ma, respectively. The provenance signature of the Canastra Group comprises a wide range of detrital zircon ages with a significant Paleoproterozoic component (∼1.8 and ∼2.1 Ga) and an important Mesoproterozoic source (1.1-1.2 Ga), especially for the Paracatu Formation, indicating the São Francisco-Congo Craton as main source. These provenance data, in particular the absence of Neoproterozoic zircon grains, typical of the active margin of the Brasília Belt, allied with the homogeneous Paleoproterozoic TDM values are consistent with the previous interpretation that the Canastra Group represents a sedimentary sequence deposited on a passive margin setting. Zircon grains from the diamictite of the Ibiá Group yielded ages ranging from 936 to 2500 Ma. In contrast, the overlying calc-phyllite of the Rio Verde Formation reveals a dominant Neoproterozoic provenance pattern with important peaks at 665, 740 and 850 Ma. The São Francisco-Congo Craton and Goiás Magmatic Arc are, most probably, the two main source regions for the Ibiá Group which may represent, therefore, a former fore- or back-arc sedimentary sequence. Tectonically, therefore, the Ibiá Group is equivalent to the Araxá Group exposed in central Goiás and both represent syn-orogenic sedimentary sequences formed with important detrital contributions derived from the Neoproterozoic Goiás Arc. The provenance data presented here indicate that the Cubatão Formation is most possibly representative of a Marinoan or younger glacial event. © 2009 Elsevier Ltd. All rights reserved.

In the central portion of the Transversal Zone (Borborema Province, northeastern Brazil), feld geological mapping combined with interpretation o airborne gammaspectrometric, magnetic and satellite imagery (Landsat 7 ETM+) data were performed in order to evaluate the importance (especially, continuation a depth) of shear zones as potential candidates to represent terrain boundaries and sutures. This integrated analysis emphasized three deeper structures which separat crustal blocks, including as such the Serra do Caboclo and the Congo-Cruzeiro do Nordeste shear zones. A deep anomaly, located between those two structures, ma represent the continuation, horizontally displaced, of one of them, or a third, non outcropping but interconnected shear zone. The favored interpretation considers thi sector of the Transversal Zone as formed by deep-rooted, northeast-southwest trending shear zones (with tops of anomalies reaching 6 to 16 km depths), cut by shallowe structures (tops of the anomalies reaching, at maximum, 2 to 6 km depth), with east-west trends. In this context, the importance and continuity at depth of the Serra d Caboclo shear zone is highlighted, and as such inferred to be the suture between Piancó-Alto Brígida and Alto Pajeú terranes, in accordance with feld geological data. © 2011 Sociedade Brasileira de Geofísica.

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