The Mesoproterozoic Guapor茅 suture in the SW Amazonian Craton: Geotectonic implications based on field geology, zircon geochronology and Nd-Sr isotope geochemistry

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• 作者：Gilmar Jos茅 Rizzotto ; Jo茫o Orestes S. Santos ; L茅o Afraneo Hartmann ; Eric Tohver ; M谩rcio Martins Pimentel ; Neal J. McNaughton
• 关键词：Suture zone ; Amazonian Craton ; Ophiolite ; Geochronology ; Mesoproterozoic
• 刊名：Journal of South American Earth Sciences
• 出版年：December, 2013
• 年：2013
• 卷：48
• 期：Complete
• 页码：271-295
• 全文大小：9588 K

文摘

A major Mesoproterozoic paleo-plate boundary in the southwestern Amazonian Craton, the Guapor茅 Suture Zone, is investigated by U-Pb zircon geochronology, Sr-Nd isotope geochemistry and aeromagnetic data. This suture zone is constituted dominantly by ophiolitic mafic-ultramafic rocks of the Trincheira Complex, and minor proportion of tonalites of the Rio Galera and S茫o Felipe complexes, Colorado Complex, amphibolites of the Rio Alegre Terrane and syn- to late-kinematic mafic to felsic plutonic rocks. The ophiolitic Trincheira Complex formed during an accretionary phase from 1470 to 1430 Ma and was overprinted by upper amphibolite-granulite facies metamorphism during the collisional phase of the Ectasian followed by syntectonic emplacement of gabbro and granite plutons (1350-1340 Ma). The ophiolites were intruded by syntectonic tonalitic-plagiogranitic plutons ca. 1435 Ma. Mafic-ultramafic rocks of the Trincheira ophiolites show moderate to highly positive initial epsilon Nd (t = 1.46 Ga) values (+2.6 to聽+8.8) and very low initial ⁸⁷Sr/⁸⁶Sr ratio (0.7013-0.7033). It is suggested that these magmas originated from a depleted mantle source in an island-arc-back-arc setting. The identification of a fossil ophiolite in the Guapor茅 Suture Zone early as 1470-1435 Ma and later collisional phase, as late as 1350 Ma, marks the impingement of the proto-Amazonian Craton against the Paragua Block, before the formation of the Rodinia supercontinent. The results provide important insights into the geodynamic history of the SW Amazonian Craton, with evidence for both accretionary orogen and subduction of oceanic lithosphere in the Mesoproterozoic, and provide information that allows other workers to evaluate the configuration of supercontinents.