Recent work has revealed that the Montagne Noire dome, located in the foreland of the Variscan belt (French Massif Central), contains a record of nearly coeval, late Variscan eclogitization and migmatization. Given these new results, it is important to understand the chronology of events that produced high-grade metamorphism and exhumation. Using U-Th-Pb dating of monazite, this study confirms ages of ~315–300 Ma for high-T metamorphism in the augen gneiss that makes up a large fraction of the Montagne Noire dome, and documents for the first time ~295 Ma monazite ages in compositionally varied fine-grained gneisses that form folded continuous layers within the core of the dome. The fine-grained gneiss layers are intensely sheared and are interpreted to have localized late, high-T deformation in the core of the dome. These sheared fine-grained gneisses form a network of shear zones that were kinematically linked to the extensional and strike-slip deformation zones that exhumed the Montagne Noire dome in a pull-apart (s.l.) domain. Continued deformation-recrystallization and fluid flow within these shear zones likely drove rejuvenation of monazite for ~5 million years after much of the melt had crystallized in the Montagne Noire dome.

中文翻译：

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Montagne Noire圆顶（法国中央地块）的变质和变形时代：利用独居石U-Th-Pb年代学挖掘细粒片麻岩的记忆

最近的工作表明，位于 Variscan 带（法国地块中部）前陆的 Montagne Noire 圆顶包含几乎同时代的、晚期 Variscan 榴辉岩化和混杂化的记录。鉴于这些新结果，重要的是了解产生高级变质作用和挖掘的事件的时间顺序。使用独居石的 U-Th-Pb 测年，该研究证实了构成 Montagne Noire 圆顶的很大一部分的 augen 片麻岩中高温变质作用的年龄约为 315-300 Ma，并首次记录了约 295 Ma独居石在成分不同的细粒片麻岩中老化，在圆顶的核心内形成折叠的连续层。细粒片麻岩层受到强烈剪切，并被解释为在穹顶核心具有局部晚期高温变形。这些剪切的细粒片麻岩形成了一个剪切带网络，这些剪切带在运动学上与在拉开 (sl) 域中挖掘出 Montagne Noire 圆顶的伸展和走滑变形带相关联。在 Montagne Noire 圆顶中大部分熔体结晶后，这些剪切带内的持续变形-再结晶和流体流动可能推动了独居石的再生约 500 万年。