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Minerais pesados de rochas metapsamíticas de Caminha (Norte de Portugal)
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Abstract(s)
RESUMO: Nas proximidades de Caminha, Noroeste de Portugal, afloram
sobretudo rochas cristalinas de natureza granítica e metavulcanossedimentar.
Contudo, na localidade próxima de Vilar de Mouros, observam-se litologias
de carácter metassedimentar, detrítico, siliciclástico, correspondentes a
unidades de idade Silúrica a Devónica delimitadas por cavalgamentos de
direção, progressivamente variável, de NNE-SSW a NE-SW. Os desloca mentos tangenciais mais importantes, caracterizam-se por sentidos de trans porte para Norte e Nordeste. São atribuídos à 2ª fase de deformação Varisca.
Os extratos de minerais densos, obtidos em bromofórmio, para os
grauvaques de Vilar de Mouros – Argela, mostram zircão, ilmenite,
xenótimo, rútilo e monazite. Os grauvaques representam uma sequência
siliciclástica detrítica com metamorfismo de baixo grau, tectonicamente
interlaminada com a sequência metavulcanossedimentar, e podem ser
equacionados como paleoplaceres com concentrações elevadas de “areias
pesadas” portadoras de Terras Raras, Zr, Y e Ti.
ABSTRACT: Near Caminha, Northwestern Portugal, granitic and metavul canosedimentar rocks are predominant. However, in Vilar de Mouros not far from Caminha, there are metasedimentary, detrital and siliciclastic lithologies, corresponding to units of Silurian to Devonian age, delimited by overthrust structures striking, progressively, from NNE-SSW to NE-SW. The most important tangential displacements are characterized by a tectonic transport to the North and Northeast. They are assigned to the second Variscan deformation phase. The heavy minerals assemblages, obtained by heavy liquid separation, for the greywackes of Vilar de Mouros – Argela, show a set of abundant zircon, ilmenite, xenotime, rutile and monazite. This greywaques represent a detrital siliciclastic sequence with low-grade meta morphism, tectonically interlaminated inside the metavulcanosedimentary sequence, and can be equated as paleoplaceres with high concentrations of "heavy sands" bearing Rare Earths, Zr, Y and Ti.
ABSTRACT: Near Caminha, Northwestern Portugal, granitic and metavul canosedimentar rocks are predominant. However, in Vilar de Mouros not far from Caminha, there are metasedimentary, detrital and siliciclastic lithologies, corresponding to units of Silurian to Devonian age, delimited by overthrust structures striking, progressively, from NNE-SSW to NE-SW. The most important tangential displacements are characterized by a tectonic transport to the North and Northeast. They are assigned to the second Variscan deformation phase. The heavy minerals assemblages, obtained by heavy liquid separation, for the greywackes of Vilar de Mouros – Argela, show a set of abundant zircon, ilmenite, xenotime, rutile and monazite. This greywaques represent a detrital siliciclastic sequence with low-grade meta morphism, tectonically interlaminated inside the metavulcanosedimentary sequence, and can be equated as paleoplaceres with high concentrations of "heavy sands" bearing Rare Earths, Zr, Y and Ti.
Description
Keywords
Minerais densos Formações siliciclásticas Paleoplaceres Tectono-estratigrafia Dense minerals Siliciclastic rocks Paleoplacers Tectono-stratigraphy
Citation
Barros & Gomes 2020, ‘Minerais pesados de rochas metapsamíticas de Caminha (Norte de Portugal)’, Comunicações Geológicas, vol. 107, nº 1 (especial), pp. 105-107. https://doi.org/10.34637/01g7-ct35
Publisher
LNEG - Laboratório Nacional de Energia e Geologia