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首页> 外文期刊>Contributions to Mineralogy and Petrology >Protracted fluid-induced melting during Barrovian metamorphism in the Central Alps
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Protracted fluid-induced melting during Barrovian metamorphism in the Central Alps

机译：在中阿尔卑斯山的巴罗夫变质过程中流体诱导的长时间熔化

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The timing and dynamics of fluid-induced melting in the typical Barrovian sequence of the Central Alps has been investigated using zircon chronology and trace element composition. Multiple zircon domains in leucosomes and country rocks yield U–Pb ages spanning from ~32 to 22 Ma. The zircon formed during Alpine melting can be distinguished from the inherited and detrital cores on the basis of their age, Th/U (<0.1) and trace element composition. Ti-in-zircon thermometry indicates crystallization temperatures around 620–700°C. Their composition allows discriminating between (1) zircon formation in the presence of early garnet, (2) zircon in equilibrium with abundant L-MREE-rich accessory phases (allanite, titanite and apatite) typical of metatonalites, and (3) zircon formed during melting of metasediments in feldspar-dominated assemblages. The distribution of zircon overgrowths and ages indicate that repeated melting events occurred within a single Barrovian metamorphic cycle at roughly constant temperature; that in the country rocks zircon formation was limited to the initial stages of melting, whereas further melting concentrated in the segregated leucosomes; that melting occurred at different times in samples a few meters apart because of the local rock composition and localized influx of the fluids; and that leucosomes were repeatedly melted when fluids became available. The geochronological data force a revision of the temperature–time path of the migmatite belt in the Central Alps. Protracted melting over 10 My followed the fast exhumation of Alpine eclogites contained within the same region and preceded fast cooling in the order of 100°C/Ma to upper crustal levels. Communicated by J. Hoefs.
机译：使用锆石年代学和微量元素组成，研究了中阿尔卑斯山典型Barrovian序列中流体诱发的融化的时间和动力学。白质体和乡村岩石中的多个锆石域产生的U–Pb年龄范围从〜32到22 Ma。根据年龄，Th / U（<0.1）和微量元素组成，可以将高山融化过程中形成的锆石与继承和碎屑核区分开。锆石中钛的测温表明结晶温度约为620–700°C。它们的成分可以区分（1）早期石榴石存在下的锆石形成，（2）平衡的，具有丰富的变元石典型的富含L-MREE的辅助相（方铁矿，钛矿和磷灰石）的锆石，以及（3）锆石在形成过程中形成的锆石。长石为主的组合中的沉积物融化。锆石的过度生长和年龄分布表明，在大致恒定的温度下，在单个Barrovian变质周期内发生了重复的熔化事件。在国内，锆石的形成仅限于熔化的初始阶段，而进一步的熔化则集中在分离的白质中；由于局部岩石成分和流体的局部涌入，相距几米的样品在不同时间发生融化；当液体变得可用时，白细胞反复融化。地质年代数据迫使对中阿尔卑斯山的辉石带温度-时间路径进行修订。在同一区域内的高山榴辉岩快速掘出之后，持续熔化超过10 My，然后以100°C / Ma的速度快速冷却至上地壳。由J.Hoefs沟通。

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