Placeres marinhos

Silva, Cleverson Guizan

doi:10.1590/s0102-261x2000000300010

Cited by 8 publications

(4 citation statements)

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“…These factors are, therefore, controllers of the mechanical dispersion of the heavy minerals along the continental margin. The mechanical dispersion at the studied area has association with eustatic variations of the sea level throughout the Quaternary period (Silva 2000;Freire and Cavalcanti 1998).…”

Section: Heavy Mineralsmentioning

confidence: 88%

“…It is suggested that the terrigenous part of the pelagic sediments of the studied area is the result of weathering of continental rocks with various compositions, as well as of continental rocks of other states of northeastern Brazil. Fluvial deposits formed at the extensive coastal plain across the continental shelf during low sea level at the end of the Pleistocene were drowned by the Holocenic marine transgression and have partially been reworked and redistributed in the transgressive sands that covered part of the Ceará continental shelf (Silva 2000).…”

Section: Granulometric Analysis and Descriptionmentioning

confidence: 99%

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General aspects of continental margin sediments of the Ceará State, northeast Brazil, from mineralogy and principal component analysis

Marques

Bezerra

Souza³

et al. 2019

JGSB

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mineralogy, portable X-ray fluorescence (XRFp), portable X-ray diffractometry (XRDp), and principal component analysis (PCA) have been made in samples of two deep cores of the continental margin of the Ceará State, northeast Brazil, aiming to detail the general aspects of deep sedimentation, including mechanical dispersion of continental minerals, environmental chemistry, and clay identification. The samples comprised biogenic oozes, clays, coarse silt, and fine sand to a lesser extent. The granulometric composition suggests slow and calm sediment accumulation over time. XRDp analysis pointed out that pelagic clays consist of chlorite, kaolinite, nontronite, and vermiculite. High oxidation levels are suggested for the two core samples, represented by the light brown color 5YR 6/4 of the sediments. Traces of minerals existing at the continental shelf were found, although in the core SIS-454 at 160 to 164 cm depth, there is a total absence of both heavy and light continental minerals. In core SIS-515, the total absence of heavy and light minerals was found at the depth of 87 to 92 cm. The levels with absence of continental minerals are probably associated with the absence of mechanical dispersion due to transgression and regression events in the Ceará continental shelf. The high oxidation levels can probably be linked to shallow waters caused by sea level changes, or to large period of sedimentation in the slope. From the statistical analysis, it is suggested that element contents are related to each other according to the provenance setting, whereas the pelagic sediment has provenance from marine water, resurgence currents, wind transport, cosmic dust, and from slow transportation, originated from the continent. It was deduced that sedimentation in the area was affected by at least two events with absence of mechanical dispersion of continental sediments, associated with geochemical characteristics represented by antagonism between elements of terrigenous and biogenic origin. These events are possibly associated with small-scale regressions occurred during the Flandrian Transgression in the Ceará Basin.

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Section: Heavy Mineralsmentioning

confidence: 88%

Section: Granulometric Analysis and Descriptionmentioning

confidence: 99%

General aspects of continental margin sediments of the Ceará State, northeast Brazil, from mineralogy and principal component analysis

Marques

Bezerra

Souza³

et al. 2019

JGSB

View full text Add to dashboard Cite

show abstract

“…Os pláceres marinhos têm íntima relação com as variações eustáticas do nível do mar durante o Quaternário, oscilando entre exposição das plataformas continentais e afogamento das mesmas (Kudrass, 2000;Silva, 2000;Lalomov & Tabolitch, 2000;Gent et al, 2005;Tomazzoli et al, 2007;Corrêa et al, 2008;Addad, 2010;Cavalcanti, 2011). Como resultado dessas oscilações, uma notável quantidade de pláceres foi formada em períodos de nível de mar baixo, localizando-se em feições como vales fluviais afogados e antigas linhas de praias.…”

Section: Introductionunclassified

Distribuição espacial de minerais pesados nos sedimentos superficiais da Plataforma Continental Oeste do Ceará, Nordeste do Brasil

2016

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Os sedimentos da plataforma continental oeste cearense foram investigados com relação à sua textura, conteúdo de carbonato de cálcio e minerais pesados com a geração do modelo digital de fundo desta plataforma. A estatística multivariada foi aplicada aos dados mineralógicos para auxiliar na interpretação da proveniência dos minerais pesados. A plataforma continental oeste cearense, apesar da predominância da sedimentação carbonática, apresenta concentrações importantes de minerais pesados (4,54 %), originando depósitos do tipo plácer nas areias litoclásticas e litobioclásticas situadas mais a leste da área estudada (Folha Fortaleza). Foram identificadas irregularidades indicativas de paleocanais e antigas linhas de praia que favorecem a concentração de minerais pesados. A assembleia mineral (ilmenita, turmalina, epídoto, hornblenda, monazita, estaurolita, sillimanita, rutilo, magnetita, zircão, andaluzita, cianita, granada, leucoxênio, diopsídio, apatita, espinélio e cassiterita) sugere contribuições regionais do retrabalhamento dos sedimentos da Formação Barreiras e contribuição local das rochas metamórficas do Complexo Ceará. Afloramentos do embasamento cristalino na plataforma continental próximos ao Porto do Pecém (São Gonçalo do Amarante) contribuem diretamente no aporte de sedimentos terrígenos e são nesses locais que os minerais pesados se concentram. A estatística multivariada discriminou os dois tipos de proveniências anteriormente descritos, contudo devem-se levar em consideração outras contribuições como das areias pretas costeiras, aporte fluvial atual (continental) e pretérito (vales fluviais afogados) e sedimentos marinhos de deriva litorânea.

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“…3.5 Uso de minerais pesados (MP) na inferência de transporte de sedimento Consideram-se MP aqueles cuja densidade supera a do Bromofórmio (CHBr 3 , ρ=2,85 kg l -1 ), como monazita, turmalina, zircão, rutilo, epídoto, dentre outros. Quando encontrados em altas concentrações e com possibilidade de exploração econômica são denominados pláceres (Silva, 2000).…”

Section: Aplicações Do Modelo De Sta No Brasil E No Mundounclassified

Deriva litorânea e evolução da linha de costa no sul do Espírito Santo (Brasil)

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Placeres marinhos

Cited by 8 publications

References 0 publications

General aspects of continental margin sediments of the Ceará State, northeast Brazil, from mineralogy and principal component analysis

General aspects of continental margin sediments of the Ceará State, northeast Brazil, from mineralogy and principal component analysis

Distribuição espacial de minerais pesados nos sedimentos superficiais da Plataforma Continental Oeste do Ceará, Nordeste do Brasil

Deriva litorânea e evolução da linha de costa no sul do Espírito Santo (Brasil)

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