U-Pb geochronology of Archean magmatism and basement reactivation in the Carajás area, Amazon shield, Brazil

Machado, Nuno; Lindenmayer, Zara Gerhardt; Krogh, T. E.; Lindenmayer, D.

doi:10.1016/0301-9268(91)90040-h

Cited by 291 publications

(326 citation statements)

References 22 publications

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“…According to Macambira (2003), the maximum deposition interval of this unit is 29 M.y., with maximum age 2759 ± 2 M.y. equals to Parauapebas Formation (Machado et al, 1991), and minimal age 2740 ± 8 M.y. (Trendall et al, 1998) corresponding to a sill that cuts Carajás Formation.…”

Section: Alternative Methods For Differentiation Of Banded Iron Formamentioning

confidence: 99%

“…They also occur associated to lower basaltic flows with layers of basic to intermediate pyroclastic rocks and volcanoclastics, felsic flows and tuffs described as rhyolites (Meirelles & Dardenne 1991, Zucchetti & Lobato 2004. The Parauapebas Formation is dated 2759 ± 2 and 2760 ± 11 M.y., obtained through U-Pb zircon (Machado et al, 1991;Trendall et al, 1998).…”

Section: Alternative Methods For Differentiation Of Banded Iron Formamentioning

confidence: 99%

“…Data available in the literature show that the metamorphism of these rocks has occurred at around 2.8 Ga. (Machado et al, 1991;Roberts et al, 1992;Pimentel & Machado 1994;Pidgeon et al, 2000).…”

Section: Geological Settingmentioning

confidence: 99%

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The Use of Alternative Methods for Differentiation of Banded Iron Formations and Iron Ore in the Body N4ws, Serra Norte – Caraj´as Mineral Province

Nascimento¹,

Silva²,

Toledo³

et al. 2016

Rev. Bras. Geof.

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ABSTRACT. The use of non-traditional geophysical methods is becoming increasingly common in activities involving iron ore, as the increasing ore demand intensified the competition in the international market. This motivated us to integrate the physical properties of the rocks to better understand the relations of the iron ore with the proto-ore and host rocks. The work was conducted in N4WS body, Serra Norte, Carajás Mineral Province (CMP), located in the state of Pará, Brazil. The Carajás Mineral Province hosts some of the largest world-class iron ore deposits operated by Vale S.A. The results of airborne magnetic data showed that the mineralized bodies previously mapped are not directly linked to the high gradients observed in the amplitude of the analytic signal. This response is related to the proto-ore, constituted by jaspilites with low values of K, eU and eTh. Measurements of the magnetic susceptibility and gamma radiation emission in drill holes were satisfactory. There was a clear differentiation between iron ore, jaspilites and mafic rocks, mainly in the magnetic susceptibility parameter. The gamma-ray results from radioelements separated iron formations and associated mineralization from the adjacent mafic rocks. The use of the non-supervised classification k-means was useful for distinguishing between jaspilites within the same package and to show anomalous areas not previously mapped. The integration of rock physical properties, geological data and airborne geophysical data produced excellent results. There was a direct correlation between what was measured and what was observed in situ at the surface. Thus, it was possible to individualize the lithotypes in the N4WS using the physical properties. This confirms the feasibility of using these methods as an alternative to the currently used tools for iron ore exploration, with the potential to increase the efficient use of human and financial resources investments.Keywords: multisource data integration, jaspilites, gamma-ray spectrometry, rock physical properties. RESUMO.A utilização de métodos geofísicos não tradicionais está se tornando cada vez mais comum em atividades que envolvem o minério de ferro, uma vez que a alta demanda impulsiona o mercado internacional. Este avanço nos leva a integrar a assinatura das propriedades físicas de rocha para melhor entendimento do minério de ferro com o protominério e suas rochas adjacentes. O trabalho foi realizado no corpo N4WS, Serra Norte, Província Mineral de Carajás (CMP), localizado no estado do Pará. A Província Mineral de Carajás abriga alguns dos maiores depósitos de minério de ferro de classe mundial, todos explorados pela Vale S.A. Os resultados dos dados aeromagnéticos mostraram que os corpos mineralizados previamente mapeados não possuem uma ligação direta com os gradientes elevados observados na amplitude do sinal analítico. Esta respostaé relacionada ao protominério, constituído por jaspilitos de assinatura gamaespectrométrica relacionados aos baixos valores de K, eU e eTh. As respostas das medi...

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Section: Alternative Methods For Differentiation Of Banded Iron Formamentioning

confidence: 99%

Section: Alternative Methods For Differentiation Of Banded Iron Formamentioning

confidence: 99%

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The Use of Alternative Methods for Differentiation of Banded Iron Formations and Iron Ore in the Body N4ws, Serra Norte – Caraj´as Mineral Province

Nascimento¹,

Silva²,

Toledo³

et al. 2016

Rev. Bras. Geof.

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“…Os metabasaltos do Supergrupo Itacaiúnas sofreram efeitos de metamorfismo de contato e de deformação dúctil em resposta à expansão lateral durante a colocação destes granitos (Barros & Barbey 1998, Barros et al 2001, Sardinha et al 2006. Pequenos corpos de anortositos e de rochas ultramáficas afloram nas proximidades da Serra Pelada e são atribuídos ao Complexo Luanga (DOCEGEO 1988), cuja idade de cristalização seria de 2,763 Ga (Machado et al 1991). Diques e soleiras de gabros hidrotermalizados ocorrem no platô da Serra dos Carajás, a oeste do Granito Central dos Carajás e cortam arenitos da Formação Águas Claras (Soares et al 1994).…”

Section: Geologia Regionalunclassified

“…Cigano e Central dos Carajás) têm formas irregulares, discordantes das estruturas regionais (DOCEGEO 1988). Diversas datações apontam idades de 1,888 Ga para estas rochas (Machado et al 1991). Rochas vulcânicas máficas a félsicas paleoproterozóicas afloram de modo subordinado na região (Rivalenti et al 1998).…”

Section: Geologia Regionalunclassified

Integração De Dados De Radar, Aerogamaespectrométricos E Geológicos Nos Domínios Do Complexo Granítico Estrela, Província Mineral De Carajás

CUNHA¹,

Santos²,

Paradellá³

et al. 2006

RBG

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Resumo Distintos produtos integrados de radar foram avaliados na caracterização geológica do Complexo Granítico Estrela, situado na borda ocidental da Província Mineral de Carajás. O Complexo Granítico Estrela é considerado um dos maiores representantes do evento de granitização sintectônica que ocorreu no Arqueano do Craton Amazônico. A integração digital de dados de radar de abertura sintética (SAREX) com dados aerogeofísicos gamaespectrométricos e geológicos permitiu a visualização da distribuição espacial dos domínios geológicos (Complexo e suas encaixantes), favoreceu a reavaliação de dados prévios e confirmou, de modo geral, a distribuição espacial de fácies magmáticas internas do Complexo Granítico Estrela. Por ser um sensor de excelência na caracterização de relevo topográfico, controlado pela geologia estrutural e por padrões erosivos das litologias, a contribuição do radar no produto integrado esteve ligada às variações de atributos texturais, enquanto que o componente de matiz foi controlado pelas respostas gamaespectrométricas das rochas. As áreas de maiores respostas gamaespectrométricas corresponderam aos domínios de monzogranitos ricos em biotita, distribuídos em áreas de altitudes algo mais elevadas, e que apresentam maiores concentrações de K 2 O, Th, U, Rb e de elementos terras raras. A utilização deste tipo de abordagem em mapeamento geológico e exploração mineral é relevante considerando-se o potencial econômico da Província Mineral de Carajás e a contribuição na redução de custos dos trabalhos de campo.Palavras-chave: radar imageador, SAREX, aerogamaespectrometria, Complexo Granítico Estrela, Carajás. Abstract INTEGRATION OF RADAR, AEROGAMMASPECTROMETRIC AND GEOLOGICAL DATA IN THE DOMAINS OF THE ESTRELA GRANITE COMPLEX, CARAJAS MINERAL PROVINCE.. SAR (Synthetic ApertureRadar) products were evaluated for geological characterization of the Estrela granite complex, Pará State, Brazilian Amazon. The Complex is located on the southeastern border of the Amazonian Craton, and is considered a representative of the Archean syntectonic granitization event within the Carajás Mineral Province. The integration of airborne C-HH SAR (SAREX) with airborne gamma ray (Total Count) and geology (map of internal facies) has provided a powerful tool for terrain visualization, for re-evaluation of previous data and also confirmed information regarding the spatial distribution of internal petrographic facies. In the integrated product, SAR imagery has contributed with valuable textural information related to geological structures and erosion expression of lithologies, while airborne gamma-ray (Total Count) was useful in the discrimination of rock units, closely related to hue variation, allowing the discrimination of distinct domains (granite complex and host rocks, internal magmatic facies). The areas with stronger gammaespectrometric responses are spatially related to biotite monzogranites, which have higher concentrations of potassium, uranium, thorium, rubidium and rare-earth elements. Diabase dikes and brittle...

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The role of fault reactivation in the development of tropical montane lakes

Souza‐Filho

Pinheiro

Costa

et al. 2020

Earth Surf Processes Landf

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This work details the role of fault reactivation in the development of tropical montane lakes by using basin morpho-structural analysis and seismostratigraphic studies. The upland lakes are severely faulted sinkholes, whose faults penetrate the Quaternary sedimentary units. Four main stages are related to the lake formation: (i) an Early Proterozoic tectonic deformation of the rocks along the southern border of the Carajás Structure, where the lake is placed; (ii) differential erosion byand building ofthe formation of the South Carajás Hill; (iii) Fe-rich crust formation by weathering and gravitational collapse faults following the E-W plateau border and the start of Violão Lake formation during the Pliocene-Pleistocene; and (iv) episodic fault-fracture reactivation by gravitational collapse causing pulses of subsidence in the lake and outlining its faulted borders. Dissolution of the lateritic crust and erosion by runoff drainage under wet climate conditions were coeval with fault activities, which allowed the deposition of relatively thick clastic deposits organized in three main seismostratigraphic units associated with major lake-level fluctuations. Initial fault reactivation under low-level water started lacustrine basin development with deposition of prograding fan deltas related to the main drainage. A second fault reactivation by gravitational collapse increased the lake accommodation space and resulted in the deposition of fine-grained sediments from dilute interflows or overflows until 36000calyear BP. At about 31000calyear BP, rapid decreases in the lake water level under redox conditions at the sediment/water interface allowed widespread siderite formation. A third gravitational collapse episode was responsible for the increase in the lake area and depth and the returning of clastic/organic deposition up to the present. This tropical montane lake can be seen as a representative example for understanding the formation of other upland lakes controlled by fault reactivation.

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U-Pb geochronology of Archean magmatism and basement reactivation in the Carajás area, Amazon shield, Brazil

Cited by 291 publications

References 22 publications

The Use of Alternative Methods for Differentiation of Banded Iron Formations and Iron Ore in the Body N4ws, Serra Norte – Caraj´as Mineral Province

The Use of Alternative Methods for Differentiation of Banded Iron Formations and Iron Ore in the Body N4ws, Serra Norte – Caraj´as Mineral Province

Integração De Dados De Radar, Aerogamaespectrométricos E Geológicos Nos Domínios Do Complexo Granítico Estrela, Província Mineral De Carajás

The role of fault reactivation in the development of tropical montane lakes

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