High-pressure medium-temperature metamorphism of semi-pelitic rocks in the Scotia Metamorphic Complex, Powell Island, South Orkney Islands, Antarctica

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dc.contributor.authorVinagre da Costa, Rodrigo
dc.contributor.authorde Moraes, Renato
dc.contributor.authorJohannes Trouw, Rudolph Allard
dc.contributor.authorAmarante Simões, Luiz Sérgio
dc.contributor.authorMendes, Julio Cezar
dc.contributor.institutionUniversidade Federal do Rio de Janeiro (UFRJ)
dc.contributor.institutionUniversidade de São Paulo (USP)
dc.contributor.institutionDep. de Geologia
dc.date.accessioned2022-04-28T19:26:57Z
dc.date.available2022-04-28T19:26:57Z
dc.date.issued2019-04-01
dc.description.abstractThe Antarctic continent constituted the southwestern margin of Gondwana until its break-up in the early Cretaceous, when new margins were created along the separating fragments of South America and Antarctica, forming the Scotia Arc. In the Jurassic, part of this passive continental margin became active with subduction of oceanic lithosphere, leading to the introduction of ocean floor material into the accretionary wedge accompanied by deformation and metamorphism. One of these margins is preserved in the South Orkney Microcontinent, and crops out at the South Orkney Islands. At Powell Island, situated in the center of the South Orkney Islands, a gradual transition from very low-grade metarenite, interlayered with metasiltite and slate of the Greywacke Shale Formation, in the south, to biotite-garnet schist, in the north, belonging to the Scotia Metamorphic Complex, is present. The metamorphic map presents from south to north a pumpellyite muscovite chlorite zone, a garnet zone, a biotite-garnet zone and an abundant biotite-garnet zone. Thermobarometric calculations yielded for the garnet and garnet-biotite zones temperatures between 498 and 517 °C with pressures of 9–11 kbar and for the abundant biotite-garnet zone temperatures between 522 and 550 °C and pressures between 11.8 and 13 kbar. These results align well with earlier obtained data for the lower grade rocks and confirm the idea of metamorphism in an accretionary wedge. The relatively high-pressure is interpreted to be responsible for the inversion of the biotite and garnet isograds, for the albitic composition of plagioclase and for the relatively Ca-rich garnet. P-T conditions fall in the transitional field between greenschist, amphibolite, blueschist and eclogite facies.en
dc.description.affiliationUniversidade Federal do Rio de Janeiro Dep. de Geologia IGEO
dc.description.affiliationUniversidade de São Paulo Instituto de Geociências Dep. de Mineralogia e Geotectônica
dc.description.affiliationUniversidade do Estado de São Paulo Dep. de Geologia
dc.description.sponsorshipCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
dc.description.sponsorshipConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
dc.format.extent8-26
dc.identifierhttp://dx.doi.org/10.1016/j.jsames.2019.01.002
dc.identifier.citationJournal of South American Earth Sciences, v. 91, p. 8-26.
dc.identifier.doi10.1016/j.jsames.2019.01.002
dc.identifier.issn0895-9811
dc.identifier.scopus2-s2.0-85060214597
dc.identifier.urihttp://hdl.handle.net/11449/221236
dc.language.isoeng
dc.relation.ispartofJournal of South American Earth Sciences
dc.sourceScopus
dc.subjectAccretionary prism
dc.subjectMetamorphic petrology
dc.subjectMineral chemistry
dc.subjectThermobarometry
dc.titleHigh-pressure medium-temperature metamorphism of semi-pelitic rocks in the Scotia Metamorphic Complex, Powell Island, South Orkney Islands, Antarcticaen
dc.typeArtigo
unesp.author.orcid0000-0003-0901-8234[3]

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