Felsic rocks of the Erzgebirge in the Central European Variscides experienced ultra-high pressure metamorphism at ∼340 Ma, followed by nearly isothermal decompression during channel like rapid exhumation within ∼10 Ma. Despite the general time frame of exhumation and emplacement within mid-crustal levels is known, available geochronological data do not provide a detailed timescale of individual stages of the entire process. Addressing this problem we combined white mica ⁴⁰Ar/³⁹Ar ages obtained from multi-grain step heating and multiple single grain total fusion experiments with mineral chemical, structural and tectono-metamorphic constraints. Gneisses of the channel center are characterized by E-W elongated white mica exclusively aligned in the continuous foliation. The rocks of the channel contact zone and in the hanging and footwall contain NW-SE stretched white mica parallel to the foliation, but also components of ductile to brittle-ductile shear bands truncating the main foliation. Well defined weighted plateau ages of all samples range between 340.0 ± 1.1 Ma and 327.9 ± 1.3 Ma, confirming previously published data, but represent presumably mixed ages due to multi-phase deformation. Single grain age distributions, in contrast, exhibit two statistically significant age peaks at 338.6 ± 0.2 Ma and at 332.8 ± 0.3 Ma. Rocks without shear bands exclusively contain white mica belonging to the older age fraction, whereas rocks with shear bands show a broad age scatter including both age fractions. We interpret these age distributions as being independent of closure temperature, but reflecting different dynamic recrystallization events. The older age fraction reflects the formation of the main foliation during west-directed emplacement of the ultra-high pressure rocks in mid-crustal levels at ∼339 Ma, whereas the shear band related neo- or recrystallization is responsible for the younger age fraction dating the final transport in the upper crust at ∼333 Ma.

中欧 Variscides 的 Erzgebirge 长英质岩经历了约 340 Ma 的超高压变质作用，随后在约 10 Ma 内在通道期间近等温减压，如快速折返。尽管已知中地壳水平的挖掘和就位的一般时间框架，但可用的地质年代学数据并没有提供整个过程各个阶段的详细时间尺度。为了解决这个问题，我们结合了白云母⁴⁰ Ar/ ³⁹从具有矿物化学、结构和构造变质约束的多晶粒步进加热和多个单晶粒全聚变实验中获得的 Ar 年龄。通道中心的片麻岩的特征是 EW 细长的白色云母，完全排列在连续的叶理中。河道接触带的岩石以及悬垂和下盘中的岩石包含平行于叶理的 NW-SE 拉伸白色云母，但也包含截断主要叶理的韧性到脆性-韧性剪切带的成分。所有样品的定义明确的加权平台年龄范围在 340.0 ± 1.1 Ma 和 327.9 ± 1.3 Ma 之间，证实了先前公布的数据，但由于多相变形，可能代表混合年龄。相比之下，单粒年龄分布在 338.6 ± 0.2 Ma 和 332.8 ± 0.3 Ma 处表现出两个统计上显着的年龄峰值。没有剪切带的岩石只含有属于较老年龄部分的白色云母，而有剪切带的岩石显示出广泛的年龄分布，包括两个年龄部分。我们将这些年龄分布解释为与闭合温度无关，但反映了不同的动态再结晶事件。年龄较大的部分反映了中地壳水平超高压岩石西向侵位过程中主要叶理的形成，约 339 Ma，而与剪切带相关的新结晶或再结晶是较年轻年龄部分定年的原因上地壳的最终输运时间约为 333 Ma。我们将这些年龄分布解释为与闭合温度无关，但反映了不同的动态再结晶事件。年龄较大的部分反映了中地壳水平超高压岩石西向侵位过程中主要叶理的形成，约 339 Ma，而与剪切带相关的新结晶或再结晶是较年轻年龄部分定年的原因上地壳的最终输运时间约为 333 Ma。我们将这些年龄分布解释为与闭合温度无关，但反映了不同的动态再结晶事件。年龄较大的部分反映了中地壳水平超高压岩石西向侵位过程中主要叶理的形成，约 339 Ma，而与剪切带相关的新结晶或再结晶是较年轻年龄部分定年的原因上地壳的最终输运时间约为 333 Ma。