Metamorphic evolution of a subduction complex, South Shetland Islands, Antarctica

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dc.contributor.authorTrouw, RAJ
dc.contributor.authorSimoes, LSA
dc.contributor.authorValladares, C. S.
dc.contributor.institutionUniversidade Federal do Rio de Janeiro (UFRJ)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2014-05-20T15:21:24Z
dc.date.available2014-05-20T15:21:24Z
dc.date.issued1998-07-01
dc.description.abstractA subduction complex composed of ocean floor material mixed with arc-derived metasediments crops out in the Elephant Island group and at Smith Island, South Shetland Islands, Antarctica, with metamorphic ages of 120-80 Ma and 58-47 Ma? respectively. Seven metamorphic zones (I-VII) mapped on Elephant Island delineate a gradual increase in metamorphic grade from the pumpellyite-actinolite facies, through the crossite-epidote blueschist facies, to the lower amphibolite facies. Geothermometry in garnet-amphibole and garnet-biotite pairs yields temperatures of about 350 degrees C in zone III to about 525 degrees C in zone VII. Pressures were estimated on the basis of Si content in white mica, Al2O3 content in alkali amphibole, Na-M4/Al-IV in sodic-calcic and calcic amphibole, Al-VI/Si in calcic amphibole, and jadeite content in clinopyroxene. Mean values vary from about 6-7.5 kbar in zone II to about 5 kbar in zone VII. Results from the other islands of the Elephant Island group are comparable to those from the main island; Smith Island yielded slightly higher pressures, up to 8 kbar, with temperatures estimated between 300 and 350 degrees C. Zoned minerals and other textural indications locally enable inference of P-T-t trajectories, all with a clockwise evolution. A reconstruction in space and time of these P-T-t paths allows an estimate of the thermal structure in the upper crust during the two ductile deformation phases (D-1 & D-2) that affected the area. This thermal structure is in good agreement with the one expected for a subduction zone. The arrival and collision of thickened oceanic crust may have caused the accretion and preservation of the subduction complex. In this model, D-1 represents the subduction movements expressed by the first vector of the clockwise P-T-t path, D-2 reflects the collision corresponding to the second vector with increasing temperature and decreasing pressure, and D-3 corresponds to isostatic uplift accompanied by erosion, under circumstances of decreasing temperature and pressure.en
dc.description.affiliationUniv Fed Rio de Janeiro, Inst Geociencias, BR-21910900 Rio de Janeiro, Brazil
dc.description.affiliationUniv Estadual Paulista, Inst Geociencias & Ciências Exatas, BR-13500230 Rio Claro, SP, Brazil
dc.description.affiliationUniv Estado Rio de Janeiro, DGEL, BR-20559900 Rio de Janeiro, Brazil
dc.description.affiliationUnespUniv Estadual Paulista, Inst Geociencias & Ciências Exatas, BR-13500230 Rio Claro, SP, Brazil
dc.format.extent475-490
dc.identifierhttp://dx.doi.org/10.1111/j.1525-1314.1998.00151.x
dc.identifier.citationJournal of Metamorphic Geology. Malden: Blackwell Science Inc., v. 16, n. 4, p. 475-490, 1998.
dc.identifier.doi10.1111/j.1525-1314.1998.00151.x
dc.identifier.issn0263-4929
dc.identifier.urihttp://hdl.handle.net/11449/32548
dc.identifier.wosWOS:000074326800001
dc.language.isoeng
dc.publisherBlackwell Science
dc.relation.ispartofJournal of Metamorphic Geology
dc.relation.ispartofjcr4.418
dc.relation.ispartofsjr2,847
dc.rights.accessRightsAcesso restrito
dc.sourceWeb of Science
dc.subjectaccretionary wedgept
dc.subjectgeothermobarometrypt
dc.subjectP-T-t pathspt
dc.subjectSanbagawa type metamorphismpt
dc.titleMetamorphic evolution of a subduction complex, South Shetland Islands, Antarcticaen
dc.typeArtigo
dcterms.licensehttp://olabout.wiley.com/WileyCDA/Section/id-406071.html
dcterms.rightsHolderBlackwell Science Inc

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