Metamorphic Remnants of the Variscan Orogeny across the Alps and Their Tectonic Significance

IF 2.4 Q2 GEOSCIENCES, MULTIDISCIPLINARY Geosciences (Switzerland) Pub Date : 2023-10-06 DOI:10.3390/geosciences13100300
Manuel Roda, Maria Iole Spalla, Marco Filippi, Jean-Marc Lardeaux, Gisella Rebay, Alessandro Regorda, Davide Zanoni, Michele Zucali, Guido Gosso
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引用次数: 1

Abstract

Lithospheric slices preserving pre-Alpine metamorphic imprints are widely described in the Alps. The Variscan parageneses recorded in continental, oceanic, and mantle rocks suggest a heterogeneous metamorphic evolution across the Alpine domains. In this contribution, we collect quantitative metamorphic imprints and ages of samples that document Variscan tectonometamorphic evolution from 420 to 290 Ma. Based on age distribution and metamorphic imprint, three main stages can be identified for the Variscan evolution of the Alpine region: Devonian (early Variscan), late Devonian–late Carboniferous (middle Variscan), and late Carboniferous–early Permian (late Variscan). The dominant metamorphic imprint during Devonian times was recorded under eclogite and HP granulite facies conditions in the Helvetic–Dauphinois–Provençal, Penninic, and eastern Austroalpine domains and under Ep-amphibolite facies conditions in the Southalpine domain. These metamorphic conditions correspond to a mean Franciscan-type metamorphic field gradient. During the late Devonian–late Carboniferous period, in the Helvetic–Dauphinois–Provençal and central Austroalpine domains, the dominant metamorphic imprint developed under eclogite and HP granulite facies conditions with a Franciscan field gradient. Amphibolite facies conditions dominated in the Penninic and Southalpine domains and corresponded to a Barrovian-type metamorphic field gradient. At the Carboniferous–Permian transition, the metamorphic imprints mainly developed under amphibolite-LP granulite facies conditions in all domains of the Alps, corresponding to a mean metamorphic field gradient at the transition between Barrovian and Abukuma (Buchan) types. This distribution of the metamorphic imprints suggests a pre-Alpine burial of oceanic and continental crust underneath a continental upper plate, in a scenario of single or multiple oceanic subductions preceding the continental collision. Both scenarios are discussed and revised considering the consistency of collected data and a comparison with numerical models. Finally, the distribution of Devonian to Triassic geothermal gradients agrees with a sequence of events that starts with subduction, continues with continental collision, and ends with the continental thinning announcing the Jurassic oceanization.
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横跨阿尔卑斯山脉的瓦里斯坎造山带变质残余物及其构造意义
保存前阿尔卑斯变质印记的岩石圈切片在阿尔卑斯山脉得到了广泛的描述。在大陆、海洋和地幔岩石中记录的瓦里斯坎共生岩表明,整个阿尔卑斯地区的变质演化是不均匀的。在这篇文章中,我们收集了定量的变质印记和样品的年龄,记录了Variscan构造变质演化从420到290 Ma。根据时代分布和变质印记,将高寒地区的瓦里斯坎演化划分为泥盆世(瓦里斯坎早期)、晚泥盆世-晚石炭世(瓦里斯坎中期)和晚石炭世-早二叠世(瓦里斯坎晚期)三个主要阶段。泥盆纪的主要变质印记记录在helvei - dauphinois - provenalal、pennini和东澳阿尔卑斯域的榴辉岩和HP麻粒岩相条件下,以及南阿尔卑斯域的ep -角闪岩相条件下。这些变质条件对应于一个平均的方济各型变质场梯度。晚泥盆世-晚石炭世,在helveti - dauphinois - provenal和中奥高山域中,以榴辉岩和HP麻粒岩相条件发育为主的变质印记,具有方济场梯度。闪长岩相条件在奔宁和南阿尔卑斯地区占主导地位,对应于巴罗维亚型变质场梯度。在石炭-二叠纪过渡时期,阿尔卑斯山脉各域的变质印记主要发育于角闪岩- lp麻粒岩相条件下,对应于Barrovian型与Abukuma (Buchan)型过渡时期的平均变质场梯度。这种变质印记的分布表明,在大陆板块碰撞之前的单一或多次海洋俯冲的情况下,在大陆板块上的海洋和大陆地壳的前阿尔卑斯埋藏。考虑到所收集数据的一致性以及与数值模型的比较,对这两种情景进行了讨论和修正。最后,泥盆纪至三叠纪地温梯度的分布符合从俯冲开始、大陆碰撞继续到大陆减薄结束的一系列事件,表明侏罗纪海洋化。
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来源期刊
Geosciences (Switzerland)
Geosciences (Switzerland) Earth and Planetary Sciences-Earth and Planetary Sciences (all)
CiteScore
5.30
自引率
7.40%
发文量
395
审稿时长
11 weeks
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