Abstract Alkaline granitic dikes intruding the metasedimentary mantle and orthogneiss cores of the Aston and Hospitalet domes of the Axial Zone of the Pyrenees are subjects of a laser ablation ICP-MS U-Pb zircon geochronology study. The age spectra recorded by detrital, magmatic xenocrystic and inherited zircons reveal a more complex, nearly continuous Paleozoic magmatic history of the Variscan basement of the Pyrenees than previously known. Inherited and detrital zircons of Mesoarchean, Paleoproterozoic to Ediacaran ages attest to the Peri-Gondwana location of the Cambrian sediments that later form the metamorphic core of the Variscan Pyrenees. The youngest magmatic zircon ages fall into the late Carboniferous and earliest Permian, ranging from ca. 306–297 Ma, and represent the emplacement ages of the dikes and small granite intrusions. The age spectra of magmatic xenocrystic zircons contain several maxima, middle (475–465 Ma) and late Ordovician (455–445 Ma), early (415–402 Ma) and late Devonian (385–383 Ma), early (356–351 Ma) and middle Carboniferous (ca. 328 Ma). Middle Ordovician and middle Carboniferous ages are obtained from xenocrystic zircons that were assimilated from the rocks the dikes intruded, the Aston and Hospitalet orthogneisses and the Soulcem granite. The presence of early-mid Carboniferous magmatic zircons in several samples lends further support to a wide-spread early Variscan magmatic activity in the central Pyrenees. The other age peaks do not have equivalent igneous or metaigneous rocks in the central Axial Zone, but are thought to be present in the Pyrenean crust, not exposed and yet to be identified. The diversity of Ordovician, Devonian and Carboniferous up to Permian magmatic ages indicates polyphase emplacement of intrusive bodies during pre-Variscan and Variscan orogenies. The source of the heat for the Devonian to early-mid Carboniferous magmatic activity remains elusive and may involve intracontinental subduction zone, lithospheric-scale shearing or a mantle plume (TUZO).

中文翻译：

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冈瓦纳大陆北部边缘的多相岩浆脉冲：来自比利牛斯山脉片麻岩穹顶的 U-Pb 锆石年代学

摘要 侵入比利牛斯山脉轴向区 Aston 和 Hospitalet 穹窿的变沉积地幔和正方麻岩核的碱性花岗岩脉是激光烧蚀 ICP-MS U-Pb 锆石年代学研究的对象。由碎屑、岩浆异晶和遗传锆石记录的年龄光谱揭示了比利牛斯山脉瓦利斯坎基底的古生代岩浆历史比以前已知的更复杂、近乎连续。中太古代、古元古代到埃迪卡拉纪的继承和碎屑锆石证明了寒武纪沉积物位于冈瓦纳半岛附近，后来形成了瓦里斯坎比利牛斯山脉的变质核心。最年轻的岩浆锆石年龄落入晚石炭纪和最早的二叠纪，范围从约 306-297 Ma，代表岩脉和小型花岗岩侵入体的侵位年龄。岩浆异晶锆石的年龄谱包含几个极大值、中（475-465 Ma）和晚奥陶世（455-445 Ma）、早（415-402 Ma）和晚泥盆世（385-383 Ma）、早（356-351） Ma）和中石炭纪（约 328 Ma）。中奥陶世和中石炭纪年代是从外晶锆石中获得的，这些锆石是从岩脉侵入的岩石、Aston 和 Hospitalet 正片麻岩以及 Soulcem 花岗岩中同化的。几个样品中早中期石炭纪岩浆锆石的存在进一步支持了比利牛斯山脉中部广泛分布的早期瓦利斯坎岩浆活动。其他年龄峰在中轴带没有等效的火成岩或变火成岩，但被认为存在于比利牛斯地壳中，未出露，尚待鉴定。奥陶纪的多样性，泥盆纪和石炭纪到二叠纪岩浆时代表明在前瓦里斯坎和瓦里坎造山运动期间侵入体的多相侵位。泥盆纪到早中石炭纪岩浆活动的热源仍然难以捉摸，可能涉及大陆内俯冲带、岩石圈尺度剪切或地幔柱 (TUZO)。