Petrological constraints and PT path of Devonian collapse tectonics within the Scandian mountain belt (Western Gneiss Region, Norway)
Petrological constraints and PT path of Devonian collapse tectonics within the Scandian mountain belt (Western Gneiss Region, Norway)
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斯堪的纳山带内泥盆纪塌陷构造的岩石学约束和PT路径（挪威西部片麻岩地区）
DOI：
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发表时间：
1992
影响因子：
2.7
通讯作者：
M. Brunel
中科院分区：
文献类型：
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作者：
A. Chauvet;J. Kienast;J. Pinardon;M. Brunel
挪威加里东期后伸展控制了中泥盆世沉积盆地的形成和沉积。这些“塌陷盆地”是沿西片麻岩区加里东期高变质岩顶部的低角度伸展滑脱断裂形成的。本文对张拉剪切带内的榴辉岩和高压云母岩进行了岩石学分析。研究这些高压岩石周围的片麻岩和云母岩，可以描述具有该地区特征的完整PT路径。适当的地温计和气压计的应用证实，高压条件下（500-600°C, 1 -15kbar）的逆行演化以近等温减压和角闪岩相变质为特征。将PT路径形状与大陆造山地壳隆升热演化理论模型进行了比较。我们可以观察到，在减压的第一阶段，温度的升高比模型预测的要小。考虑到研究区伸展构造的证据，我们认为伸展的干预加速了加里东期增厚地壳的崩塌过程，减少了晚造山加热，可以解释在减压过程中如此小的温度升高。
In Norway, post-Caledonian extension controlled the formation and sedimentation of Middle Devonian sedimentary basins. These ‘collapse basins’ were deposited along a low-angle extensional detachment fault on top of Caledonian high-grade metamorphic rocks of the Western Gneiss Region. This paper concerns the petrological analysis of eclogite and high-pressure micaschist collected within the extensional shear zone. Study of gneisses and micaschists surrounding these high-pressure rocks allows description of the complete PT path which characterized this area. Application of appropriate geothermometers and geobarometers confirms that the retrograde evolution following high-pressure conditions (ll-15kbar at 500-600°C) was characterized by nearly isothermal decompression followed by amphibolite facies metamorphism. The shape of the PT path is compared with theoretical models of thermal evolution of continental orogenic crust during uplift. We can observe an increase in temperature during the first stages of decompression smaller than predicted by the models. Considering the evidence for extensional tectonic in the study area, we propose to explain such a small increase in temperature during the decompression by the intervention of extension which accelerates the collapse process and reduces the late-orogenic heating of the Caledonian thickened crust.