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dc.contributor.authorSaalmann, Kerstinpt_BR
dc.contributor.authorRemus, Marcus Vinicius Dornelespt_BR
dc.contributor.authorHartmann, Leo Afraneopt_BR
dc.date.accessioned2011-01-19T05:58:46Zpt_BR
dc.date.issued2006pt_BR
dc.identifier.issn0016-7568pt_BR
dc.identifier.urihttp://hdl.handle.net/10183/27446pt_BR
dc.description.abstractThe SW–NE-striking Porongos belt, located between juvenile Neoproterozoic rocks in the west and the Dom Feliciano belt, characterized by intense reworking of older crust, in the east, comprises a greenschist to amphibolite-facies metavolcano-metasedimentary succession (Porongos sequence) of unknown age with some exposures of Palaeoproterozoic gneisses (Encantadas gneisses). High-temperature ductile deformation of the basement gneisses comprises at least two magmatic events followed by three deformational phases including folding and shearing (DT1–DT3) and can be attributed to the Palaeoproterozoic Trans-Amazonian orogeny. The deformation of the Porongos sequence occurred during the Neoproterozoic Brasiliano orogeny and comprises four ductile deformation phases (DB1–DB4), including two phases of isoclinal folding associated with shearing recorded in mylonitic layers, followed by closed NW-vergent folding and thrusting leading to formation of a thrust stack. Uplift of the basement and formation of late tectonic sedimentary basins occurred as a result of semi-ductile to brittle block faulting in a sinistral strike-slip regime. The Porongos sequence can be subdivided into a southeastern and a northwestern part. Trace element analyses as well as Sm–Nd and Rb–Sr geochemical data indicate partial melting and significant contamination by old continental crust for the metavolcanic rocks. The metavolcanic rocks show εNd(t=780 Ma) values of −20.64 and −21.72 (northwestern units) and −6.87 (southeastern sequence). The metasedimentary rocks were derived from late Palaeoproterozoic to Archaean sources, and the data indicate different sources for the northwestern and southeastern rock units of the Porongos sequence. εNd(t=780 Ma) are −6.25 and −6.85 in the southeastern units, with TDM model ages between 1734 and 1954 Ma, and vary between −14.72 and −17.96 in the northwestern parts, which have TDM model ages between 2346 and 2710 Ma. High 87Sr/86Sr(t) values between 0.7064 and 0.7286 confirm reworking of older crust. Isotopic signatures of the Porongos sequence do not show indications for a significant contribution from a Neoproterozoic juvenile source. A passive margin or continental rift environment is suggested for the tectonic setting of the Porongos belt, which is compatible with both deposition of shallow marine to deep marine sediments and stretching of continental crust leading to volcanism which is characterized by significant contamination by old continental crust.en
dc.format.mimetypeapplication/pdfpt_BR
dc.language.isoengpt_BR
dc.relation.ispartofGeological magazine. Vol.143, n. 1 (Jan. 2006), p.59-88pt_BR
dc.rightsOpen Accessen
dc.subjectWest Gondwanaen
dc.subjectEvolução estruturalpt_BR
dc.subjectCinturão Porongospt_BR
dc.subjectNeoproterozoicen
dc.subjectBrasiliano orogenyen
dc.subjectNd model ageen
dc.subjectTectonicsen
dc.titleStructural evolution and tectonic setting of the Porongos belt, southern Brazilpt_BR
dc.typeArtigo de periódicopt_BR
dc.identifier.nrb000586611pt_BR
dc.type.originEstrangeiropt_BR


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