Brasiliano crustal extension and emplacement fabrics of the mangerite-charnockite pluton of Umarizal, North-east Brazil

dc.creatorArchanjo, CJ
dc.creatorMacedo, JWP
dc.creatorGalindo, AC
dc.creatorAraujo, MGS
dc.date1998
dc.dateJAN
dc.date2014-12-02T16:31:03Z
dc.date2015-11-26T16:45:43Z
dc.date2014-12-02T16:31:03Z
dc.date2015-11-26T16:45:43Z
dc.date.accessioned2018-03-28T23:31:22Z
dc.date.available2018-03-28T23:31:22Z
dc.identifierPrecambrian Research. Elsevier Science Bv, v. 87, n. 41671, n. 19, n. 32, 1998.
dc.identifier0301-9268
dc.identifierWOS:000072622900002
dc.identifier10.1016/S0301-9268(97)00050-8
dc.identifierhttp://www.repositorio.unicamp.br/jspui/handle/REPOSIP/63210
dc.identifierhttp://www.repositorio.unicamp.br/handle/REPOSIP/63210
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/63210
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1274305
dc.descriptionShear zone kinematics and anisotropy of magnetic susceptibility (AMS) data have been used in a Brasiliano/PanAfrican fayalite-clinopyroxene (+/- orthopyroxene) syenite of Umarizal (NE Brazil) in order to reveal its emplacement mechanisms. The pluton is located at the intersection of two major shear zones: a NE-trending transcurrent Portalegre shear zone (PSZ) and a NW-to E-trending Frutuoso Gomes shear zone (FGSZ). The FGSZ dips gently NE in its NW-trending branch and N in the E-trending branch. Asymmetric porphyroclasts and S/C' shear planes observed in mylonitic gneisses along the FGSZ point to a top to the East (extensional) movement. Hysteresis and low-field susceptibility measurements on mangerites and charnockites indicate that magnetic susceptibility is principally carried by multidomain magnetite. In the core of the pluton, the magnetic anisotropy is weaker (P < 1.05) and characterized by neutral (L = F) to rod-shaped (L > F) AMS ellipsoids. The magnetic anisotropy increases south-westward (P > 1.10) approaching the FGSZ and the AMS ellipsoid becomes dominantly disc shaped (F > L). Magnetic lineations plunge gently to NW in the western part of the pluton and to ENE on the East. The absence of steep lineations, except around a large xenolith in the center of the pluton, exclude the presence of magmatic feeding zones at the actual level of exposure, Foliations are roughly parallel to the pluton contact, but most of them dip moderately towards Northeast. In the SW border the magnetic foliation is parallel to the mylonitic foliation displayed in the FGSZ. Although emplaced within migmatized host rocks, the kinematics of the shear zones and the magmatic fabric pattern rule out a buoyancy-driven diapiric emplacement of the pluton. Syn-magmatic shear deformation associated with E-W crustal stretching accounts for the fabrics of emplacement recorded in the Umarizal pluton. (C) 1998 Elsevier Science B.V.
dc.description87
dc.description41671
dc.description19
dc.description32
dc.languageen
dc.publisherElsevier Science Bv
dc.publisherAmsterdam
dc.publisherHolanda
dc.relationPrecambrian Research
dc.relationPrecambrian Res.
dc.rightsfechado
dc.rightshttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy
dc.sourceWeb of Science
dc.subjectalkaline granite
dc.subjectBrasiliano orogeny
dc.subjectemplacement
dc.subjectmagnetic fabric
dc.subjectshear zones
dc.subjectMagnetic-susceptibility
dc.subjectDistribution Anisotropy
dc.subjectHysteresis Properties
dc.subjectRocks
dc.subjectMagmatism
dc.subjectDeformation
dc.subjectGranites
dc.subjectExample
dc.subjectModels
dc.titleBrasiliano crustal extension and emplacement fabrics of the mangerite-charnockite pluton of Umarizal, North-east Brazil
dc.typeArtículos de revistas


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