The pre-Alpine history of the Venaco-Ghisoni Unit, a continental unit belonging to the Alpine Corsica (France), was reconstructed on the basis of U–Pb dating of zircon and allanite. Zircon was separated from a metagranitoid and an epidote-bearing metagabbro and analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Magmatic ages ranging from 291 to 265 Ma were obtained for the metagranitoid samples and 276.9 ± 1.1 Ma for the epidote-bearing metagabbro. This geochronological dataset, combined with field observations, microstructural and cathodoluminescence analysis demonstrate that in the Early Permian, the Variscan basement of the Venaco-Ghisoni Unit was intruded first by the granitoid and then by the gabbro. Allanite was identified in the metagranitoid and exhibit an U–Pb age of 225 ± 8 Ma. We interpret this age as reflecting metamorphism associated to the Late Triassic rifting predating the opening of the Piemonte-Liguria Ocean. The absence of middle Eocene—Oligocene zircon and allanite overgrowths is compatible with the low metamorphic conditions (< 350–400 °C) recorded by the Venaco-Ghisoni Unit during Alpine metamorphism.

中文翻译：

---

法国科西嘉岛（Alpine Corsica）大陆壳中记录的阿尔卑斯前热史：锆石和尿囊石LA-ICP-MS的证据

Venaco-Ghisoni单元是属于法国科西嘉岛的一个大陆单元，其阿尔卑斯山前的历史是根据锆石和尿囊石的U–Pb年代重建的。锆石与偏子纹石和带有附子的代谢物分离，并通过激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）进行分析。偏岩质样品的岩浆年龄范围为291至265 Ma，而带有附睾的附生代谢物的岩浆年龄为276.9±1.1 Ma。该地质年代数据集，结合现场观察，微观结构和阴极发光分析表明，在二叠纪早期，Venaco-Ghisoni单元的瓦里斯坎地下室首先侵入了花岗岩，然后被辉长岩侵入。尿囊石在后格纹系中被发现，其U–Pb年龄为225±8 Ma。我们将此年龄解释为反映了皮埃蒙特－利古里亚海洋开放之前晚三叠世裂谷相关的变质作用。缺少中新世—渐新世锆石和长石的过度生长与Venaco-Ghisoni单元在高山变质期记录的低变质条件（<350–400°C）相兼容。