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Geochemistry and provenance of the Carboniferous Baixo Alentejo Flysch Group, South Portuguese Zone

2013-02-15Journal article Restricted access
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dc.contributor.authorJorge, R. C. G. S.
dc.contributor.authorFernandes, Paulo
dc.contributor.authorRodrigues, B.
dc.contributor.authorPereira, Zélia
dc.contributor.authorOliveira, José Tomás
dc.date.accessioned2014-09-24T10:12:38Z
dc.date.available2014-09-24T10:12:38Z
dc.date.issued2013-02-15
dc.date.updated2014-09-23T10:43:36Z
dc.description.abstractThis work is focused on the turbiditic sediments from the Carboniferous Baixo Alentejo Flysch Group (BAFG) in the South Portuguese Zone, an external zone of the Iberian Variscides. The aim of this work is to constrain the provenance and tectonic setting of these sediments in a context of a complex evolution of SW Iberian Variscides. For this purpose, we performed a systematic study of petrographical and geochemical signatures of greywackes and shales from the three BAFG formations: Mértola, Mira and Brejeira. Major and trace element composition and ratios suggest heterogeneous source area composition for BAFG shales and greywackes. For the oldest Mértola Formation greywackes, source area is dominated by granitoid rocks with minor mafic input. The latter becomes residual in the Mira Formation. The youngest Brejeira Formation greywackes show clear felsic affiliation associated with an increase in recycled components. The shales of all three BAFG formations denote a granodioritic affiliation. Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration (PIA) values suggest moderate weathering in the source areas of Mértola and Mira formations. These indices, together with A–CN–K relations, point out to steady-state weathering conditions in the source areas of both formations. In contrast, both CIA and PIA values for the Brejeira Formation indicate variable conditions of palaeoweathering, from moderate to intense, as a consequence of non-steady-state conditions probably triggered by tectonic instability in the provenance area. Compared to the greywackes, the shales of all three BAFG formations exhibit higher CIA and PIA values, as well as low K2O/Al2O3 (~0.2) and index of compositional variability (b1), reflecting the cumulative effect of multiple cycles of sedimentary recycling and prolonged chemical weathering history. Major and trace element distribution and upper continental crust-normalized multi-element plots suggest that the sediments of BAFG were derived mainly from a continental arc/active margin with minor contribution from old continental crust. Together, our geochemical data are compatible with BAFG sediments derived mainly from SW border of the Ossa Morena Zone (Gondwanan affinity), with possible contribution from an external (Avalonian) source.por
dc.identifier.citationJorge, R.C.G.S.; Fernandes, P.; Rodrigues, B.; Pereira, Z.; Oliveira, J.T.Geochemistry and provenance of the Carboniferous Baixo Alentejo Flysch Group, South Portuguese Zone, Sedimentary Geology, 284-285, 1, 133-148, 2013.por
dc.identifier.doihttp://dx.doi.org/10.1016/j.sedgeo.2012.12.005
dc.identifier.issn0037-0738
dc.identifier.otherAUT: PFE01874;
dc.identifier.urihttp://hdl.handle.net/10400.1/5087
dc.language.isoengpor
dc.peerreviewedyespor
dc.publisherElsevierpor
dc.subjectBaixo Alentejo Flysch Grouppor
dc.subjectSouth Portuguese Zonepor
dc.subjectCarboniferouspor
dc.subjectWhole-rock geochemistrypor
dc.subjectProvenance analysispor
dc.titleGeochemistry and provenance of the Carboniferous Baixo Alentejo Flysch Group, South Portuguese Zonepor
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage148por
oaire.citation.issue1por
oaire.citation.startPage133por
oaire.citation.titleSedimentary Geologypor
oaire.citation.volume284-285por
person.familyNameFernandes
person.familyNameRodrigues
person.givenNamePaulo
person.givenNameBrígida
person.identifier422469
person.identifier.ciencia-id051D-A133-65D9
person.identifier.ciencia-id631C-A162-3F1E
person.identifier.orcid0000-0003-4888-0230
person.identifier.orcid0000-0001-9495-0813
person.identifier.ridJ-6577-2014
person.identifier.scopus-author-id57197129025
rcaap.rightsrestrictedAccesspor
rcaap.typearticlepor
relation.isAuthorOfPublicationa2d98df3-a9c2-4364-a737-25b4e89df80b
relation.isAuthorOfPublication99ea34cc-7325-4ae7-b288-31d7e43ab28f
relation.isAuthorOfPublication.latestForDiscoverya2d98df3-a9c2-4364-a737-25b4e89df80b

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