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首页> 外文期刊>Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften: ZDGG >Coeval subduction and collision at the end of the Variscan Orogeny (Odenwald, Mid-German Crystalline Zone, Germany)
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Coeval subduction and collision at the end of the Variscan Orogeny (Odenwald, Mid-German Crystalline Zone, Germany)

机译：瓦里斯坎造山运动末期的共产俯冲和碰撞（德国中德结晶带奥登瓦尔德）

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摘要

The Mid-German Crystalline Zone (MGCZ) is an integral part of the European Variscides. It is a heterogeneous Carboniferous boundary the Frankenstein Gabbro (Unit I) from the northern Odenwald (MGCZ; with low 87Sr/86Sri value of 0.7035, positive epsilon Nd value of +3.8) intruded at 362 +/- 9 Ma at shallow level (4 km depth) into the Upper Devonian (375 +/- 5 Ma, Frasnian) olivine-gabbro and wehrlite of an island arc or into thin continental crust. Ar-Ar plagioclase cooling ages at 359 +/- 3 Ma prove an exhumation of the gabbro to near-surface level by the end of the Devonian (Kirsch et al. 1988). The calc-alkaline gabbro, diorite, and granodiorite to tonalite of the central part of the West Odenwald (Unit II) with low values of 87Sr/86Sri (0.7047) and positive epsilon Nd values (+0.8 to -0.3) form part of an Early Carboniferous (354 +/- 4 Ma to 337 +/- 2 Ma) subduction-related complex of plutonic rocks. Granodiorite and quartz monzonite to granite (346 +/- 1 Ma to 337 +/- 2 Ma) of a high-K calc-alkaline to shoshonitic series with higher values of 87Sr/86Sri (0.7076 to 0.708) and lower values of epsilon Nd (-2 to -4) of the southern part of the West Odenwald (Unit III) are coeval with the subduction-related plutons of Unit II and could be explained by a higher amount of crustal contamination of the melt during continent collision. The southern part of the Odenwald collided first with Laurussia. During the coeval subduction and collision the tectonic units of the Odenwald occupied different positions in the NW active continental plate margin of Armorica. The final tectonic contact between the units of the West Odenwald occurred at 323 Ma (cooling below 300 degrees C) at the end of the Variscan collision but before the Upper Carboniferous (Bashkirian, 320 Ma) extension formed the coal-bearing Saar-Nahe Basin which rests on top of the In comparison to other plutonic complexes of the Variscan chain most of the Carboniferous plutons of the West Odenwald contain a high amount of inherited zircons. These were incorporated during the magma generation from a lower crust which is similar to the Silurian to Lower Devonian gneiss of the East Odenwald (Unit IV, Bollstein Odenwald) or an equivalent of it. Since the Lower Tournaisian, a Silurian to Emsian basement has formed the lower crust of the West Odenwald.
机译：中德结晶带 （MGCZ） 是欧洲水痘的一个组成部分。它是一个异质的石炭纪边界，弗兰肯斯坦辉长岩（单元I）来自奥登瓦尔德北部（MGCZ;低87Sr/86Sri值为0.7035，正εNd值为+3.8）以362 +/- 9 马在浅层（4公里深度）侵入上泥盆统（375 +/- 5 马，弗拉斯尼）橄榄石辉长岩和岛弧的斜长岩或薄大陆壳。Ar-Ar斜长石冷却年龄为359 +/- 3 马，证明到泥盆纪末，辉长岩被挖掘到近地表水平（Kirsch等人，1988）。西奥登瓦尔德中部（第二单元）中部的钙碱辉长岩、闪长岩和花岗闪长岩至辉长岩，低值为87Sr/86Sri （0.7047）和正εNd值（+0.8至-0.3），是早石炭世（354 +/- 4 马至 337 +/- 2 马）俯冲相关深成岩复合体的一部分。高钾钙碱性至高钾钙质系列的花岗闪长岩和石英二长岩到花岗岩（346 +/- 1 马至 337 +/- 2 马），较高值为 87Sr/86Sri （0.7076 至 0.708），西奥登瓦尔德南部（单元 III）的 εNd（-2 至 -4）值较低，与单元 II 的俯冲相关钚一致，可以解释为大陆碰撞期间熔体的地壳污染量较高。奥登瓦尔德河的南部首先与劳鲁西亚相撞。在同源俯冲和碰撞过程中，奥登瓦尔德构造单元在阿莫里卡西北活跃大陆板块边缘占据了不同的位置。西奥登瓦尔德单元之间的最后一次构造接触发生在瓦里斯坎碰撞结束时的323 马（冷却温度低于300摄氏度），但在上石炭纪（巴什基尔，320 马）延伸形成含煤萨尔-纳赫盆地之前，该盆地位于瓦里斯坎链的其他深成复合体之上，西奥登瓦尔德的大多数石炭纪钚都含有大量遗传的锆石。这些是在下地壳的岩浆生成过程中形成的，该地壳类似于东奥登瓦尔德的志留纪至下泥盆世片麻岩（IV单元，Bollstein Odenwald）或与之相当的片麻岩。自下图尔奈纪以来，志留纪到埃姆西亚的基底形成了西奥登瓦尔德的下地壳。

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