Microscale dating of distinct domains in minerals that contain relics of multiple metamorphic events is a key tool to characterize the polyphase evolution of complex metamorphic terranes. Zircon and allanite from five metasediments and five metaintrusive high-pressure (HP) rocks from the Eclogite Micaschist Complex of the Sesia Zone were dated by SIMS and LA-ICP-MS. In the metasediments, zircon systematically preserves detrital cores and one or two metamorphic overgrowths. An early Permian age is obtained for the first zircon rim in metasediments from the localities of Malone Valley, Chiusella Valley and Monte Mucrone (292 ± 11, 278.8 ± 3.6 and 285.9 ± 2.9 Ma, respectively). In the Malone Valley and Monte Mucrone samples, the early Permian ages are attributed to high-temperature metamorphism and coincide with the crystallization ages of associated mafic and felsic intrusions. This implies that magmatism and metamorphism were coeval and associated to the same tectono-metamorphic extensional event. In the Malone Valley, allanite from a metasediment is dated at 241.1 ± 6.1 Ma and this age is tentatively attributed to a metasomatic/metamorphic event during Permo-Triassic extension. Outer zircon rims with a late Cretaceous age (67.4 ± 1.9 Ma) are found only in the micaschist from Monte Mucrone. In metagabbro of the Ivozio Complex, zircon cores yield an intrusive age for the protolith of 340.7 ± 6.8 Ma, whereas Alpine allanite are dated at 62.9 ± 4.2 and 55.3 ± 7.3 Ma. The Cretaceous ages constrain the timing of the HP metamorphic stage. The presence of zircon overgrowth only in the central area of the Eclogite Micaschist Complex is attributed to local factors such as (1) multiple fluid pulses at HP that locally enhanced zircon dissolution and recrystallization, and (2) slightly higher temperatures reached in this area during HP metamorphism.

中文翻译：

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西亚地区（西阿尔卑斯山）从石炭纪到白垩纪的演化：锆石和尿囊石年代学的见解

包含多个变质事件遗迹的矿物中不同域的微尺度测年是表征复杂变质地层多相演化特征的关键工具。来自SIMAS和LA-ICP-MS的5个沉积物和5个亚位侵入高压云母云母复合岩的超侵入高压（HP）岩石中的锆石和尿囊石。在变质沉积物中，锆石系统地保留了碎屑核和一个或两个变质的过度生长。在马龙河谷，丘塞拉河谷和蒙特穆克龙河地区的变质沉积物中，第一个锆石边缘获得了二叠纪早期（分别为292±11、278.8±3.6和285.9±2.9 Ma）。在Malone Valley和Monte Mucrone的样本中，二叠纪早期属于高温变质作用，与镁铁质和长英质侵入相伴的结晶年龄相吻合。这意味着岩浆作用和变质作用是同时期的，并且与同一构造-变质伸展事件有关。在马龙谷，变质沉积中的尿囊石的日期为241.1±6.1 Ma，该年龄暂定归因于Permo-Triassic扩展期间的变质/变质事件。白垩纪晚期（67.4±1.9 Ma）的锆石外缘仅在蒙特·穆克龙山的云母中发现。在伊沃齐奥复合体的异辉石中，锆石岩芯的原生质侵入年龄为340.7±6.8 Ma，而高山艾拉石的年龄为62.9±4.2和55.3±7.3 Ma。白垩纪年龄限制了HP变质阶段的时间。