The timing of metamorphism in the Odenwald–Spessart basement, Mid-German Crystalline Zone
The timing of metamorphism in the Odenwald–Spessart basement, Mid-German Crystalline Zone
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DOI：
10.1007/s00531-016-1375-3
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发表时间：
2017-07
影响因子：
2.3
通讯作者：
T. Will;B. Schulz;E. Schmädicke
中科院分区：
文献类型：
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作者：
T. Will;B. Schulz;E. Schmädicke
新的原位电子探针独居石和白色云母40ar /39Ar阶梯加热年龄支持了这样的主张，即德国中部结晶带Odenwald-Spessart基底至少由两个不同的地壳地体组成，它们在并置于一起之前经历了不同的地质历史。独居石年龄限制构造热事件在430±43 Ma， 349±14 Ma， 331±16 Ma和317±12 Ma/316±4 Ma， 40ar /39Ar分析提供白色云母年龄为322±3 Ma和324±3 Ma。奥登瓦尔德西部在约430 ~ 349 Ma发生麻粒岩相变质作用，奥登瓦尔德东部和Spessart中部在约324 ~ 316 Ma发生角闪岩相变质作用。我们对这些数据的解释表明，将东奥登瓦尔德- spessart基底与西奥登瓦尔德基底分开的Otzberg-Michelbach断裂带是Rheic缝合线的一部分，该缝合线标志着分离Gondwana-和avalonia -派生地壳地体的主要Variscan板块边界的位置。奥登瓦尔德西部石炭系麻粒岩相事件的年龄与邻近的奥登瓦尔德东部榴辉岩相变质作用的最小年龄重叠。麻粒岩和榴辉岩相岩石经历了截然不同的压力-温度路径，但在空间上接近，被Rheic缝合线隔开。由于高压变质作用和高温变质作用的年代相近，我们将Odenwald-Spessart基底解释为一对变质带，并提出相邻的高压和高温岩石是在同一俯冲带体系中变质的。这些岩石的并置发生在瓦里斯坎造山运动的最后阶段，沿着Rheic缝合线。
New in situ electron microprobe monazite and white mica40Ar/39Ar step heating ages support the proposition that the Odenwald–Spessart basement, Mid-German Crystalline Zone, consists of at least two distinct crustal terranes that experienced different geological histories prior to their juxtaposition. The monazite ages constrain tectonothermal events at 430 ± 43 Ma, 349 ± 14 Ma, 331 ± 16 Ma and 317 ± 12 Ma/316 ± 4 Ma, and the40Ar/39Ar analyses provide white mica ages of 322 ± 3 Ma and 324 ± 3 Ma. Granulite-facies metamorphism occurred in the western Odenwald at c. 430 and 349 Ma, and amphibolite-facies metamorphism affected the eastern Odenwald and the central Spessart basements between c. 324 and 316 Ma. We interpret these data to indicate that the Otzberg–Michelbach Fault Zone, which separates the eastern Odenwald–Spessart basement from the Western Odenwald basement, is part of the Rheic Suture, which marks the position of a major Variscan plate boundary separating Gondwana- and Avalonia-derived crustal terranes. The age of the Carboniferous granulite-facies event in the western Odenwald overlaps with the minimum age of eclogite-facies metamorphism in the adjacent eastern Odenwald. The granulite- and eclogite-facies rocks experienced contrasting pressure–temperature paths but occur in close spatial proximity, being separated by the Rheic Suture. As high-pressure and high-temperature metamorphisms are of similar age, we interpret the Odenwald–Spessart basement as a paired metamorphic belt and propose that the adjacent high-pressure and high-temperature rocks were metamorphosed in the same subduction zone system. Juxtaposition of these rocks occurred during the final stages of the Variscan orogeny along the Rheic Suture.