Timing of eclogite-facies metamorphism of mafic and ultramafic rocks from the Pohorje Mountains (Eastern Alps, Slovenia) based on Lu–Hf garnet geochronometry
Timing of eclogite-facies metamorphism of mafic and ultramafic rocks from the Pohorje Mountains (Eastern Alps, Slovenia) based on Lu–Hf garnet geochronometry
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DOI：
10.1016/j.lithos.2016.08.002
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发表时间：
2016-10
期刊：
影响因子：
3.5
通讯作者：
Sascha Sandmann;D. Herwartz;F. Kirst;N. Froitzheim;T. Nagel;R. Fonseca;C. Münker;M. Janák
中科院分区：
文献类型：
--
作者：
Sascha Sandmann;D. Herwartz;F. Kirst;N. Froitzheim;T. Nagel;R. Fonseca;C. Münker;M. Janák
Pohorje山脉的变质系列代表了在白垩纪始新世-阿尔卑斯造山旋回期间遭受超高压条件的东部阿尔卑斯领域的一部分。斯洛文尼亚比斯特里察超镁铁质杂岩体位于波霍尔杰山脉东南部，是一个宽8 km的蛇纹岩体，含有含石榴子石的超镁铁质岩和榴辉岩透镜体。它是一个混合的大陆单位的变质片麻岩，正片麻岩和榴辉岩嵌入和一部分。我们目前的Lu-Hf石榴石测年加上地球化学和岩石学数据从三个样品：一个石榴石二辉橄榄岩，一个榴辉岩从超镁铁质复杂的，和一个榴辉岩从周围的混合单元。两种榴辉岩和石榴二辉橄榄岩的年龄分别为96.6 ± 1.2Ma和94.8 ± 5.1Ma，石榴二辉橄榄岩的年龄分别为91.6 ± 4.1Ma。由于高温再平衡，所有样品的石榴石显示主要二价元素的均匀浓度。它，但是，保存增长相关的分区相对于卢在所有三个样品意味着Lu-Hf年龄仍然记录石榴石的生长。超镁铁杂岩与周围的大陆混合单元具有相同的俯冲历史，即在石榴子石生长阶段和之后，超镁铁杂岩都是俯冲板块的一部分。
The metamorphic series of the Pohorje Mountains represents a part of the Eastern Alpine realm that was subjected to ultrahigh-pressure conditions during the Cretaceous Eo-Alpine orogenic cycle. The Slovenska Bistrica Ultramafic Complex located in the south-eastern Pohorje Mountains is an 8 km wide serpentinite body that contains lenses of garnet-bearing ultramafites and eclogites. It is embedded in and part of a mixed continental unit of metapelitic gneisses, orthogneisses, and eclogites. We present Lu–Hf garnet chronometry coupled with geochemical and petrological data from three samples: one garnet lherzolite, one eclogite from within the ultramafic complex, and one eclogite from the surrounding mixed unit. All obtained ages are identical within error, i.e. 96.6 ± 1.2 Ma and 94.8 ± 5.1 Ma, respectively, for the two eclogites and 91.6 ± 4.1 Ma for the garnet lherzolite. Garnet of all samples shows homogeneous concentrations of major bivalent elements due to high temperature re-equilibration. It does, however, preserve growth-related zoning with respect to Lu in all three samples implying that Lu–Hf ages still record garnet growth. The coincidence of ages suggests that the ultramafic complex and the surrounding continental mixed unit share the same subduction history, i.e. the complex was part of the subducting plate during and after the garnet growth stages.