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Granitos estaníferos da região de Santa Comba de Rossas, norte de Portugal
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Abstract(s)
RESUMO: Na região de Santa Comba de Rossas aflora um complexo granítico (G1-G3) que se instalou durante os estágios sin-cinemáticos da Orogenia Varisca, há 317,9 ± 8,7 Ma (datação Rb-Sr de rocha total). Os granitos são intrusivos em metassedimentos de idade silúrica, do Domínio Parautóctone da Zona da Galiza – Trás-os-Montes, instalando-se no núcleo de uma antiforma NW-SE, resultante das fases de deformação D1 e D3, apresentando evidências de uma deformação em regime dúctil e frágil. Os dados geoquímicos e isotópicos sugerem que o granito G1, com biotite > moscovite e o granito G3, com biotite ≈ moscovite, correspondem a pulsos magmáticos distintos, que terão resultado da fusão parcial de materiais metassedimentares e sofrido uma diferenciação por cristalização fraccionada. Este processo foi responsável pelo aumento do teor de Sn naqueles granitos e, muito provavelmente, pela ocorrência do granito moscovítico G2, o mais rico em Sn (77 ppm), no exocontacto do plutão granítico G1.
ABSTRACT: In the Santa Comba de Rossas area, a granitic complex (G1-G3) was emplaced during the syn-kinematic stages of the Variscan Orogeny, at 317.9 ± 8.7 Ma, as determined by whole rock Rb-Sr dating. The complex is intrusive on Silurian metasediments, from the Parauthocthonous Domain of Galicia – Trás-os-Montes Zone, in a NW-SE trending antiform formed during the D1 and D3 deformation phases and was itself affected by ductile and brittle deformation. Geochemical and isotopic characteristics suggest that the biotite > muscovite granite G1 and the biotite ≈ muscovite granite G3 correspond to distinct pulses of magma formed by partial melting of metasedimentary materials that subsequently evolved by fractional crystallization. This process was responsible for the increase in Sn content in those granites and, most probably, for the occurrence of the G2 muscovite granite, the richest in Sn (77 ppm), in the exocontact of the G1 granite pluton.
ABSTRACT: In the Santa Comba de Rossas area, a granitic complex (G1-G3) was emplaced during the syn-kinematic stages of the Variscan Orogeny, at 317.9 ± 8.7 Ma, as determined by whole rock Rb-Sr dating. The complex is intrusive on Silurian metasediments, from the Parauthocthonous Domain of Galicia – Trás-os-Montes Zone, in a NW-SE trending antiform formed during the D1 and D3 deformation phases and was itself affected by ductile and brittle deformation. Geochemical and isotopic characteristics suggest that the biotite > muscovite granite G1 and the biotite ≈ muscovite granite G3 correspond to distinct pulses of magma formed by partial melting of metasedimentary materials that subsequently evolved by fractional crystallization. This process was responsible for the increase in Sn content in those granites and, most probably, for the occurrence of the G2 muscovite granite, the richest in Sn (77 ppm), in the exocontact of the G1 granite pluton.
Description
Keywords
Datação Rb-Sr Cristalização fraccionada Estanho Portugal (Norte) Granitos do tipo S S-type granites Rb-Sr dating Fractional crystallization Tin
Citation
Teixeira, R. J. S., Gomes, M. E. P., Silva, P. B. & Meireles, C. A. P. (2025). Granitos estaníferos da região de Santa Comba de Rossas, norte de Portugal. In: Comunicações Geológicas, 2025, vol.112, Fascículo Especial I, pp. 41-45. https://doi.org/10.34637/a8yx-w359
Publisher
LNEG - Laboratório Nacional de Energia e Geologia