Alpine, Variscan, eo-Variscan belts: comparison between hot and cold orogens from the examples of French segments

IF 2 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Michel Faure
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Abstract

The Cenozoic Alpine, and Paleozoic Variscan and eo-Variscan collisional belts are compared in the framework of the Wilson cycle considering differences between cold and hot orogens. The W. Alps result of the opening and closure of the Liguro-Piemonte ocean, whereas the Paleozoic Eo-variscan and Variscan orogenies document multiple ocean openings and collisions in space and a polyorogenic history in time. Jurassic or Early Ordovician break-up of Pangea or Pannotia megacontinents led to the formation of passive continental margins, and the opening of Liguro-Piemonte, or Rheic, Tepla-Le Conquet, and Medio-European oceans, respectively. In Paleozoic or Mesozoic, microcontinents such as Apulia and Sesia or Armorica and Saxo-Thuringia were individualized. The oceanic convergence stage was associated with the development of arcs and back-arc basins in the Variscan belt but magmatic arcs are missing in the W. Alps, and inferred in the Eo-variscan one. Though the nappe stack is mainly developed in the subducted European or Gondwana crust in the western Alps and Eo-variscan cases, the Moldanubian nappes formed in the upper plate in the Variscan case. The Alpine and Variscan metamorphic evolutions occurred under ca. 8 °C/km and 30 °C/km gradients, respectively. During the late- to post-orogenic stages, all belts experienced “unthickening” accommodated by extensional tectonics, metamorphic retrogression, and intramontane basin opening. The importance of crustal melting, represented by migmatites, granites, and hydrothermal circulations in the Variscan and Eo-Variscan belts is the major difference with the W. Alpine one. The presence, or absence, of a previous Variscan or Cadomian continental basement might have also influenced the rheological behavior of the crust.
阿尔卑斯山脉、瓦里斯坎山脉、东-瓦里斯坎山脉带:从法国板块的例子比较热造山带和冷造山带
考虑冷造山带和热造山带的差异,在威尔逊旋回的框架下对新生代阿尔卑斯、古生代瓦里斯坎和上古瓦里斯坎碰撞带进行了比较。西阿尔卑斯山脉是liguroo - piemonte洋的开合作用的结果,而古生代- Variscan造山运动和Variscan造山运动在空间上记录了多次海洋的开合和碰撞,在时间上记录了一次多造山历史。侏罗纪或早奥陶世泛古大陆或泛诺古大陆的分裂导致被动大陆边缘的形成,并分别形成了ligur - piemonte洋、Rheic洋、Tepla-Le conquest洋和中欧洋。在古生代或中生代,Apulia和Sesia或Armorica和Saxo-Thuringia等微大陆被个体化。洋辐合阶段与瓦里斯坎构造带的弧和弧后盆地发育有关,但西阿尔卑斯山脉缺少岩浆弧,并在古-瓦里斯坎构造带中推断。虽然推覆体主要发育在西阿尔卑斯和古瓦利斯坎构造的俯冲的欧洲或冈瓦纳地壳中,但在瓦利斯坎构造中,Moldanubian推覆体形成于板块上部。阿尔卑斯和瓦里斯坎变质演化分别发生在约8°C/km和30°C/km梯度下。在造山晚期至后造山阶段,所有带都经历了伸展构造、变质退变和山内盆地张开的“非增厚”。与西阿尔卑斯带的主要区别在于,在瓦里斯坎带和上古瓦里斯坎带中,以混染岩、花岗岩和热液环流为代表的地壳熔融作用的重要性。以前的瓦里斯坎或卡多米亚大陆基底的存在或不存在也可能影响地壳的流变行为。
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来源期刊
Comptes Rendus Geoscience
Comptes Rendus Geoscience 地学-地球科学综合
CiteScore
2.80
自引率
14.30%
发文量
68
审稿时长
5.9 weeks
期刊介绍: Created in 1835 by physicist François Arago, then Permanent Secretary, the journal Comptes Rendus de l''Académie des sciences allows researchers to quickly make their work known to the international scientific community. It is divided into seven titles covering the range of scientific research fields: Mathematics, Mechanics, Chemistry, Biology, Geoscience, Physics and Palevol. Each series is led by an editor-in-chief assisted by an editorial committee. Submitted articles are reviewed by two scientists with recognized competence in the field concerned. They can be notes, announcing significant new results, as well as review articles, allowing for a fine-tuning, or even proceedings of symposia and other thematic issues, under the direction of invited editors, French or foreign.
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