The migration and composition of magmatism over time can provide important insights into the tectonic evolution of an orogen like the Variscan Belt. To identify Large Igneous Provinces (LIPs), key criteria include large magmatic volume, intraplate-origin volcanic geochemistry, and significant plumbing systems. Based on such criteria, we present evidence of ca. 347–330 Ma LIP “fragments” in the South-Western Branch of the Variscan Belt (Morocco), exemplified by the Variscan Central Jebilet Massif. The interpretations are based on four new zircon U–Pb ages obtained by sensitive high-resolution ion microprobe (SHRIMP), a geochemical database of Carboniferous mafic sills, dykes, and gabbroic intrusions together, with subordinate layered ultramafic intrusions, silicic intrusive and volcanic rocks of Central Jebilet Massif, combined with previously published and unpublished data including Sr–Nd isotope analyses. Geochemistry data indicate that the early Carboniferous magmatism of the Jebilet Massif is plume-related. Furthermore, primary magmas of the mafic rocks were generated in an intraplate setting and derived by partial melting of complex sources involving asthenosphere, lithospheric mantle, and subducting slab components (dead subduction slabs), and were modified by crustal contamination during ascent. Magmatic rocks in the same stratigraphic position also occur in other Carboniferous basins including Western Meseta (Rehamna and Moroccan Central Massif). The newly obtained and compiled zircon U–Pb ages from Western Meseta rocks, encompassing an area of ∼400,000 km2, indicate that magmatism occurred between ca. 347–330 Ma, coeval with volcanic activity in the Eastern Meseta in northeastern Morocco. The similar emplacement ages, in combination with the tectonic reconstruction of northwestern Gondwana at ca. 330 Ma, suggest that the igneous subprovinces of the Jebilet, Rehamna, and Moroccan Central Massif in Western Meseta, along with Tazekka, Debdou, and Mekkam in Eastern Meseta, the igneous rocks of the Maritimes (Magdalen) Basin, the St. Jean du Doigt bimodal layered intrusion (Brittany, France), and other equivalents such as the Iberian Pyrite Belt and the Southern Vosges magmatism, may represent the eroded and/or deformed remnants of a Large Igneous Province (LIP), which we name here the North Gondwana–Avalonia (NGA) LIP. We argue that this newly identified LIP was formed by a mantle plume that may have played a role in the breakup along the northwestern margin of the precursor megacontinent Gondwana and the assembly of Pangea. The plume was likely centered under the thick lithosphere of Avalonia. The large-scale sublithospheric plume-flow channeling from the plume head led to the development of widespread tholeiitic/alkaline magmatism in the thinned lithosphere of Western Meseta, interpreted here as a large thin-spot domain, and calc-alkaline/alkaline magmatism in the thickened lithosphere of the Eastern Meseta. The mantle plume may have been most active during the periods of ca. 390–330 Ma (Maritimes Event), ca. 370–338 Ma (Iberia Event), ca. 347–330 Ma (Meseta Event), and the multipulsed ca. 300 Ma, 290–275 Ma, and 250 Ma European North West African Magmatic Province (EUNWA or EUNWAMP), which were the periods when most of the Variscan mafic rocks were produced in these areas.

中文翻译：

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沿冈瓦纳北部边缘约 347-330 马 的大型火成岩省份的证据与盘古大陆的组装有关：来自瓦里斯坎带西南分支（摩洛哥）的 U-Pb 锆石地质年代学和地球化学的见解


岩浆作用随时间的迁移和组成可以为像瓦里斯坎带这样的造山带的构造演化提供重要的见解。要识别大型火成岩省 （LIP），关键标准包括大岩浆体积、板内起源火山地球化学和重要的管道系统。基于这些标准，我们提出了瓦里斯坎带（摩洛哥）西南分支约 347-330 马 LIP“碎片”的证据，以瓦里斯坎中央杰比莱特地块为例。这些解释基于通过敏感的高分辨率离子微探针 （SHRIMP） 获得的四个新的锆石 U-Pb 年龄，SHRIMP 是一个石炭纪镁铁质基岩、岩脉和辉长岩侵入体的地球化学数据库，以及中部 Jebilet 地块的次级层状超镁铁质侵入体、硅质侵入岩和火山岩，结合以前发表和未发表的数据，包括 Sr-Nd 同位素分析。地球化学数据表明，Jebilet Massif 的早期石炭纪岩浆作用与羽流有关。此外，镁铁质岩石的原生岩浆是在板块内环境中产生的，由涉及软流圈、岩石圈地幔和俯冲板块成分（死俯冲板）的复杂来源部分熔融而得，并在上升过程中受到地壳污染的改变。具有相同地层位置的岩浆岩也出现在其他石炭纪盆地，包括西梅塞塔（Rehamna 和摩洛哥中央地块）。从西部梅塞塔岩石中新获得和汇编的锆石 U-Pb 年龄，包括大约 400,000 平方公里的面积，表明岩浆作用发生在约 347-330 马 之间，与摩洛哥东北部东部梅塞塔的火山活动同时代。 相似的埋葬年龄，结合约 330 马 冈瓦纳西北部的构造重建，表明梅塞塔西部的 Jebilet、Rehamna 和摩洛哥中央地块的火成亚省，以及梅塞塔东部的 Tazekka、Debdou 和 Mekkam，滨海省（马格达伦）盆地的火成岩，St. Jean du Doigt 双峰分层侵入体（布列塔尼， France）和其他等价物，如伊比利亚黄铁矿带和南孚日岩浆作用，可能代表一个大型火成岩省 （LIP） 的侵蚀和/或变形残余物，我们在这里将其命名为北冈瓦纳-阿瓦隆 （NGA） LIP。我们认为，这种新发现的 LIP 是由地幔羽流形成的，该羽流可能在前体巨型大陆冈瓦纳西北边缘的分裂和盘古大陆的组装中发挥了作用。羽流可能集中在 Avalonia 厚厚的岩石圈下方。从羽流头部流出的大规模岩下层羽流通道导致在西梅塞塔的薄岩石圈中发展了广泛的钙质/碱性岩浆作用，在这里解释为一个大的薄点域，以及东梅塞塔增厚的岩石圈中的钙碱性/碱性岩浆作用。地幔羽流可能在约 390-330 马（滨海事件）、约 370-338 马（伊比利亚事件）、约 347-330 马（梅塞塔事件）和多脉冲约 300 马、290-275 马 和 250 马 欧洲西北非洲岩浆省（EUNWA 或 EUNWAMP）期间最为活跃，这是大多数瓦里斯坎镁铁质岩石在这些地区生产的时期。