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|Type:||Artigo de periódico|
|Title:||Microstructural Evolution Of The Seridó Belt, Ne-brazil: The Effect Of Two Tectonic Events On Development Of C-axis Preferred Orientation In Quartz|
|Author:||Cavalcanti de Araujo M.N.|
Alves da Silva F.C.
Jardim de Sa E.F.
de Vasconcelos P.M.
|Abstract:||The polyphase evolution of the Seridó Belt (NE-Brazil) includes D1 crust formation at 2.3-2.1 Ga, D2 thrust tectonics at 1.9 Ga and crustal reworking by D3 strike-slip shear zones at 600 Ma. Microstructural investigations within mylonites associated with D2 and D3 events were used to constrain the tectono-thermal evolution of the belt. D2 shear zones commenced at deeper crustal levels and high amphibolite facies conditions (600-650 °C) through grain boundary migration, subgrain rotation and operation of quartz 〈c〉-prism slip. Continued shearing and exhumation of the terrain forced the re-equilibration of high-T fabrics and the switching of slip systems from 〈c〉-prism to positive and negative 〈a〉-rhombs. During D3, enhancement of ductility by dissipation of heat that came from syn-D3 granites developed wide belts of amphibolite facies mylonites. Continued shearing, uplift and cooling of the region induced D3 shear zones to act in ductile-brittle regimes, marked by fracturing and development of thinner belts of greenschist facies mylonites. During this event, switching from 〈a〉-prism to 〈a〉-basal slip indicates a thermal path from 600 to 350 °C. Therefore, microstructures and quartz c-axis fabrics in polydeformed rocks from the Seridó Belt preserve the record of two major events, which includes contrasting deformation mechanisms and thermal paths. © 2003 Elsevier Ltd. All rights reserved.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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