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|Type:||Artigo de periódico|
|Title:||The Neoproterozoic Sergipano orogenic belt, NE Brazil: A complete plate tectonic cycle in western Gondwana|
|Abstract:||The Neoproterozoic Sergipano Belt formed by the collision of the Pernambuco-Alagoas Block in the north with the Sao Francisco Craton in the south, but the timing, duration and mechanics of this amalgamation are poorly understood. The belt is divided into the Caninde, Pogo Redondo-Maranco, Macurure, Vaza Barris, and Estancia lithostratigraphic domains; the first three are composed of plutonic, volcanic and sedimentary rocks and the last three of sedimentary rocks. Our new field, structural, and geochemical data. and Sm-Nd, Ar-Ar and U-Pb geochronology provide robust constraints for the following evolution. A Mesoproterozoic (similar to 980-960 Ma) continental arc (Pogo Redondo tonalitic gneisses) developed on the margin of the Palaeoproterozoic Pernambuco-Alagoas Block. Extension of this continental block gave rise to (i) A-type crustal granites and associated sedimentary rocks on the stretched, rifted margin of the Poco Redondo-Maranco Domain, (ii) the Caninde rift sequence between the Pernambuco-Alagoas Block and the Pogo Redondo/Maranco domain, (iii) a passive margin on the southern boundary of the Pernambuco-Alagoas Block on which sediments were deposited after 900 Ma, (iv) and a second passive margin on the Sao Francisco Craton. In the Caninde Domain, rifting continued until ca. 640 Ma and led to emplacement of a bimodal association of A-type granite (715 Ma) and continental mafic volcanic rocks, a continental-type layered gabbroic complex (ca. 700 Ma), magma-mingled gabbro/quartz-monzodiorite (688 Ma), and rapakivi granites (684 Ma and 641 Ma). Deformed pillow basalts and interleaved marble lenses are likely ocean floor relicts in the Caninde Domain. Closure of the Caninde oceanic basin began at ca. 630 Ma with the intrusion of arc-type granitic plutons. Convergence of the Pernambuco-Alagoas Block and the Sao Francisco Craton led to deformation on the passive margins and granite emplacement in the Macurure (628-625 Ma, and 590-570 Ma), Caninde (ca. 621 Ma) and Poco Redondo-Maranco (ca. 625 Ma) domains. A small oceanic basin was most likely subducted beneath the Pogo Redondo-Maranco Domain to account for the presence of 602 Ma arc-type volcanic rocks. Shortly after, exhumation of the Pernambuco-Alagoas Block and Caninde, Pogo Redondo-Maranco and Macurure domains in the north led to deposition of uppermost clastic sediments in the Estancia and Vaza Barris domains in the south, possibly in a foreland basin, and to final thrusting of the continental margin sedimentary rocks onto the Sao Francisco Craton. Our results indicate that the construction of western Gondwana involved a ca. 300 million years long history of plate breakup and collision. (C) 2010 Elsevier B.V. All rights reserved.|
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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