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首页> 外文期刊>Geodinamica Acta >The crust beneath the Polish Sudetes: evidence from a gneiss xenolith in Tertiary basanite from Paszowice
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The crust beneath the Polish Sudetes: evidence from a gneiss xenolith in Tertiary basanite from Paszowice

机译：波兰苏德特人以下的地壳：帕索维采第三纪玄武岩中片麻岩片状石的证据

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Xenoliths found in basaltic lavas provide useful information about the materials of the Earth crust and mantle sampled by the lava oil its way to the Surface, and they help to extend our interpretations based on geophysical data. A garnet-biotite-hornblende-gneiss xenolith (min. ca. 40 cm across) was drilled at it depth of ca. 18 m in a Tertiary basanite flow at Paszowice village near Jawor, in the easternmost part of the Kaczawa Mountains, central Sudetes (SW Poland). Based on petrography, geochemistry and thermobarometry. the xenolith is interpreted to have been formed at deep crustal levels from a metasedimentary rock. The maximum PT conditions recorded in the gneiss (T 700-740 degrees C, P ca. 10 kbar) indicate that the main metamorphic event took place at a depth of 25-30 km. thus corresponding to the present-day lower crustal level defined on geophysical constraints. The gneiss xenolith contains four zircon populations. as revealed by U-Pb SHRIMP analyses: (I) 1.7 - 2.1 Ga (2) 547 - 623 Ma, (3) 473 - 494 Ma. and (4) 354 - 437 Ma. The zircons of the youngest group (4) are interpreted to have originated during a metamorphic episode, at ca. 374 +/- 13 Ma, corresponding well with (lie HT-MP major metamorphic event in the neighboring Gory Sowie gneisses and migmatites. A range Of features (e.g. the good preservation of the xenolith. lack of signiticant chemical and thermal interaction with the lava) suggest that the gneiss was sampled by the rising lava on the final path of the magma to file Surface, probably from it depth of less than ca. 10 kin. That means that the upper Crust below this region (underlying the low-grade metamorphic Kaczawa Complex) contains gneisses originally derived front deep-crustal levels. and similar to those locally exposed in the neighborhood (e.g. in the Gory Sowie Massif to the south-east). This interpretation extends our knowledge about the structure and composition of the crust in the eastern part of the European Variscides. which otherwise is inferred only from geophysical data.
机译：在玄武岩熔岩中发现的Xenoliths提供了有用的信息，有关熔岩油进入地表的地壳和地幔物质的信息，它们有助于扩展基于地球物理数据的解释。在其深度约0.1毫米处钻出石榴石-黑云母-角闪石-片麻岩异岩。位于苏克特中部（波兰南部）Kaczawa山脉最东部的Jawor附近的Paszowice村庄，在第三纪玄武岩流中流18 m。基于岩石学，地球化学和热压法。异种岩被解释为是由变质沉积岩在深地壳水平形成的。在片麻岩中记录的最大PT条件（T 700-740摄氏度，P约为10 kbar）表明主要的变质事件发生在25-30 km的深度。因此，它对应于当今在地球物理约束条件下定义的较低地壳高度。片麻岩片岩包含四个锆石种群。如U-Pb SHRIMP分析所揭示：（I）1.7-2.1 Ga（2）547-623 Ma，（3）473-494 Ma。和（4）354-437 Ma。年龄最小的一组锆石（4）被解释为起源于约20年前的变质事件。 374 +/- 13 Ma，与（邻近的Gory Sowie片麻岩和辉锰矿中的HT-MP主要变质事件很好。）一系列特征（例如，对异种岩的良好保存。缺乏与熔岩的重要化学和热相互作用）表明，片麻岩是在岩浆到达地表的最终路径上被上升的熔岩采样的，可能是从它的深度小于约10 kin开始的。这意味着该区域下方的上地壳（在低品位变质作用之下） Kaczawa Complex）包含最初源自前深壳地层的片麻岩，并且类似于在附近（例如东南部的Gory Sowie地块中）暴露的片麻岩，这种解释扩展了我们对地壳结构和成分的认识。欧洲Variscides的东部，否则只能根据地球物理数据来推断。

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