Timing of metamorphism in the Tauern Window, Eastern Alps: Rb‐Sr ages and fabric formation
Timing of metamorphism in the Tauern Window, Eastern Alps: Rb‐Sr ages and fabric formation
复制标题
东阿尔卑斯山 Tauern Window 变质作用的时间：Rb-Sr 年龄和织物形成
DOI：
10.1111/j.1525-1314.1994.tb00052.x
复制
发表时间：
1994
影响因子：
3.4
通讯作者：
R. Cliff
中科院分区：
文献类型：
--
作者：
S. Inger;R. Cliff
东阿尔卑斯山陶恩窗的外围Schieferhulle代表了后海西Penninic盖层序列，并保留了阿尔卑斯山造山带的变质作用记录，而没有保留在基底岩石中的海西事件的继承残余。这些盖层序列较低层次的岩石的温度-时间-变形历史已经通过对P-T演化和构造背景已经很好理解的单元的年代学和岩相学研究进行了研究。
中陶恩的榴辉岩带由具有Penninic盖层亲和性的原岩形成，在基底和盖层之间的构造插入之前，经历了早期阿尔卑斯榴辉岩相变质作用。然后，它与这些单位共享一个共同的变质历史，在阿尔卑斯山造山带经历蓝片岩相和随后的绿片岩相条件。绿片岩相相，与渗透变形在盖层和水流体的涌入，重置Sr同位素在整个榴辉岩带和盖片岩的变质沉积物，记录变形和峰变质作用在28-30马。
Tauern窗东南部的外围Schieferhulle产生Rb-Sr白色云母年龄，这可以与变质堆的构造演化联系起来。早期的褶皱组构早于31 Ma，并在28 Ma时被大型东北部聚散Sonnblick褶皱结构的形成所改造。峰变质后期的这种变形，但相比之下，相当于在中央陶恩水平，峰变质条件并没有导致广泛的Sr同位素的均匀化。局部变形持续到冷却路径，直到至少23马，部分或全部重置锶白色云母年龄在一些样品。
这些同位素年龄可以与区域构造模型中的构造数据相结合，并可以约束地壳变形和板块相互作用方式的变化。然而，这样的解释必须适应在小距离的热历史的可证明的变化。
The Peripheral Schieferhulle of the Tauern Window of the Eastern Alps represents post-Hercynian Penninic cover sequences and preserves a record of metamorphism in the Alpine orogeny, without the inherited remnants of Hercynian events that are retained in basement rocks. The temperature-time-deformation history of rocks at the lower levels of these cover sequences have been investigated by geochronological and petrographic study of units whose P-T evolution and structural setting are already well understood.
The Eclogite Zone of the central Tauern formed from protoliths with Penninic cover affinities, and suffered early Alpine eclogite facies metamorphism before tectonic interposition between basement and cover. It then shared a common metamorphic history with these units, experiencing blueschist facies and subsequent greenschist facies conditions in the Alpine orogeny. The greenschist facies phase, associated with penetrative deformation in the cover and the influx of aqueous fluids, reset Sr isotopes in metasediments throughout the eclogite zone and cover schists, recording deformation and peak metamorphism at 28-30 Ma.
The Peripheral Schieferhulle of the south-east Tauern Window yields Rb-Sr white mica ages which can be tied to the structural evolution of the metamorphic pile. Early prograde fabrics pre-date 31 Ma, and were reworked by the formation of the large north-east vergent Sonnblick fold structure at 28 Ma. Peak metamorphism post-dated this deformation, but by contrast to the equivalent levels in the central Tauern, peak metamorphic conditions did not lead to widespread homogenization of the Sr isotopes. Localized deformation continued into the cooling path until at least 23 Ma, partially or wholly resetting Sr white mica ages in some samples.
These isotopic ages may be integrated with structural data in regional tectonic models, and may constrain changes in the style of crustal deformation and plate interaction. However, such interpretations must accommodate the demonstrable variation in thermal histories over small distances.