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首页> 外文期刊>Journal of South American earth sciences >Tectonic implications of U-Pb ages of detrital zircon grains in metasedimentary rocks of the northwestern sector of the Passos Nappe, southern Brasilia Belt, Brazil
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Tectonic implications of U-Pb ages of detrital zircon grains in metasedimentary rocks of the northwestern sector of the Passos Nappe, southern Brasilia Belt, Brazil

机译：巴西巴西利亚南部南部Passos Nappe西北扇沉积岩中碎屑锆石U-Pb年龄的构造意义

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摘要

The Estreito Anticline is the main structure in the northwestern sector of Passos Nappe, formed in the Late Neoproterozoic during West Gondwana amalgamation. It is characterized by folding of the thrust surface that separates the Passos Nappe from the Canastra Group. The hanging wall of the thrust includes lower units of the Passos Nappe (A, B and C units) and in the core of the fold (footwall) occur metasedimentary rocks of the Canastra Group and Metasiltite Unit. U-Pb dating of detrital zircon grains by LA-ICPMS from metasedimentary units of the Canastra Group shows contribution from a Neoarchean source (ca. 2.54-2.76 Ga) with minor contribution from Rhyacian source (similar to 2.10-2.30 Ga) with the youngest grain at 1.57 Ga. Results from the Passos Nappe samples show an important Rhyacian source (2.1 Ga), and a minor cluster with ages ranging from ca. 1.60 to 1.76 Ga (Statherian). Mesoarchean-Statherian terranes of the southwest margin of the Sao Francisco Craton represent the main sources of detrital sediments of the Passos Nappe and Canastra Group of a passive margin developed along the western margin of the continent. The U-Pb ages obtained for metasiltite show a broad distribution, with peaks between similar to 0.54-0.70 Ga, and minor age groups ranging within 0.82-1.08 Ga, 1.60-1.97 Ga, 2.02-2.22 Ga and similar to 2.60-2.85 Ga. The younger ages are compatible with the Bambuf Group exposed in the Sao Francisco Craton interior. An Ediacaran age for metasiltite in the fold interior suggests termination of deformation within the Passos Nappe at least the Early Cambrian.
机译：Estreito背斜是Passos Nappe西北部的主要构造，形成于西刚德瓦纳合并期间的新元古代晚期。它的特点是折叠了推力表面，使Passos Nappe与Canastra集团分开。推力的悬挂壁包括Passos Nappe的下部单元（A，B和C单元），并且在褶皱的核心（底盘）中出现Canastra群和Metasiltite单元的准沉积岩。来自Canastra组沉积沉积单元的LA-ICPMS对碎屑锆石颗粒进行U-Pb测年显示，新古生界来源（约2.54-2.76 Ga）贡献最大，而Rhyacian来源（约2.10-2.30 Ga）贡献最小，年龄最小。 Passos Nappe样品的结果表明，其重要的Rhyacian来源（2.1 Ga）和次要簇簇的年龄在1.57 Ga。 1.60至1.76 Ga（施塔特式）。圣弗朗西斯科·克拉顿西南边缘的Mesoarchean-Statherian地层代表了该大陆西边缘发展的被动边缘的Passos Nappe和Canastra群碎屑沉积物的主要来源。获得的变质白云母的U-Pb年龄分布宽广，峰值介于0.54-0.70 Ga之间，较小年龄组介于0.82-1.08 Ga，1.60-1.97 Ga，2.02-2.22 Ga和2.60-2.85 Ga之间年轻的年龄与暴露在圣弗朗西斯科·克拉顿内部的Bambuf集团兼容。褶皱内部的变白云母的埃迪卡拉年龄表明，至少在早寒武世时期，Passos Nappe内部的变形终止。

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