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Tournaisian volcanism associated with transtensional basin development in western Newfoundland during the amalgamation of Pangea
Gondwana Research ( IF 6.1 ) Pub Date : 2022-07-01 , DOI: 10.1016/j.gr.2022.06.013
A.M. Hinchey , I. Knight , H.A. Sandeman , J.G. Hinchey

During the Carboniferous, the assembly of the supercontinent Pangea periodically reactivated strike-slip faults and shear zones that transect the northern Appalachian Orogen. These strike-slip deformation zones represent crustal-scale zones of structural weakness that have long-lived and complex kinematic histories. Their periodic reactivation controlled the evolution of the transtensional sedimentary basins of the region. The continuous interplay between the lithospheric plates, their subcontinental lithospheric mantle, and surficial processes (i.e. oceanic/riverine, biological, atmospheric, gravitational, erosional) controlled the development of the Deer Lake Basin in western Newfoundland. The Saltwater Cove Formation of the Deer Lake Basin is a late Tournaisian lacustrian-deltaic succession interrupted by minor eruption of basalt flows and pyroclastic deposits. The basalts have E-MORB (enriched-mid ocean ridge basalt) to OIB (ocean island basalt) chemical affinities with LREE enriched profiles, lack negative Nb and Ti anomalies and εNd(t=350 Ma) values between +2.8 to +6.4. Pyroclastic deposits include mafic lapilli tuff and intermediate tuff, and have compositions similar to CAB (continental arc basalt), having steep LREE relative to HREE patterns, negative Nb and Ti anomalies, and εNd(t=350 Ma) ranging from −6.1 to −1.0. Geochemical variation within the mafic rocks is explained by an E-MORB source variably influenced by crustal contamination processes. Lithofacies analysis coupled with geochemical and isotopic data support their eruption in a transtensional, intra-orogenic basin setting that formed during the assembly of Pangea. Their moderately primitive chemistry supports the interpretation that faulting, associated with transtensional basin development, facilitated asthenosphere upwelling via edge-driven convection.



中文翻译:

图尔奈火山活动与纽芬兰西部跨张盆地发育相关,在盘古大陆合并期间

在石炭纪,超大陆盘古大陆的组合周期性地重新激活了横穿阿巴拉契亚造山带北部的走滑断层和剪切带。这些走滑变形区代表地壳尺度的结构薄弱区,具有长期和复杂的运动历史。它们的周期性重新激活控制了该地区跨张拉沉积盆地的演化。岩石圈板块、它们的次大陆岩石圈地幔和地表过程(即海洋/河流、生物、大气、引力、侵蚀)之间的持续相互作用控制了纽芬兰西部鹿湖盆地的发展。鹿湖盆地的咸水湾组是图尔奈纪晚期的湖泊-三角洲序列,被玄武岩流和火山碎屑沉积物的小规模喷发打断。玄武岩具有 E-MORB(富集中洋脊玄武岩)与 OIB(海岛玄武岩)化学亲和力,具有 LREE 富集剖面,缺乏负 Nb 和 Ti 异常以及 εNd(t=350 Ma)值在 +2.8 到 +6.4 之间。火山碎屑沉积物包括镁铁质青金石凝灰岩和中间凝灰岩,其成分类似于 CAB(大陆弧玄武岩),相对于 HREE 模式具有陡峭的 LREE,负 Nb 和 Ti 异常,εNd (t=350 Ma)范围为 -6.1 至 - 1.0。基性岩内的地球化学变化可以通过受地壳污染过程影响的 E-MORB 源来解释。岩相分析与地球化学和同位素数据相结合,支持它们在盘古大陆组装过程中形成的跨张、造山带内盆地环境中喷发。它们中等原始的化学性质支持这样的解释,即与横贯盆地发育相关的断层通过边缘驱动的对流促进了软流圈上涌。

更新日期:2022-07-01
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