Geochronology, geochemistry, and geological evolution of the Troiseck-Floning and Rosskogel nappes (Eastern Alps): unraveling parallels between the Eastern Alps and Western Carpathians

IF 1.8 2区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Martin K. Reiser, Ralf Schuster, Christoph Iglseder, Daniela Gallhofer, Josef Nievoll
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Abstract

The Troiseck-Floning and Rosskogel nappes are part of the Austroalpine Unit in the eastern part of the Eastern Alps. The nappes are in tectonic contact and comprise Permian to Mesozoic lower greenschist facies metamorphic metasediments, but only the Troiseck-Floning Nappe consists of a pre-Permian crystalline basement (Troiseck Complex) as well. LA-ICP-MS U–Pb zircon ages, Rb–Sr biotite ages and geochemical data unravel the geological evolution of these tectonic units from Neoproterozoic to Mesozoic times. Detrital U–Pb zircon analyses from siliciclastic metasediments of the Troiseck Complex indicate a late Ediacaran to early Cambrian deposition age of the volcanoclastic sequence. The age distribution correlates with a position along the northeastern Gondwana margin. A late Cambrian crystallization age (502.4 ± 6.8 Ma) of granitic intrusions together with evidence for Late Cambrian/Ordovician magmatism and metamorphism indicate a position at an active plate margin. Polyphase overprinting during the Variscan orogeny is recorded by Late Devonian/early Carboniferous pegmatite dikes (~ 353 Ma) that formed after an early Variscan event, while Pennsylvanian ages of overgrowth rims and inherited grains (~ 320 Ma) are evidence for late Variscan metamorphism. Rhyolitic to andesitic volcanic rocks from the Troiseck-Floning and Rosskogel nappes (271–264 Ma) concomitant with intrusions of porphyric granitoids now transformed to augen gneiss (271 Ma) yield evidence for Permian rift-related magmatism that is widely reported from the Eastern Alps and Western Carpathians. Rb–Sr biotite ages (75–74 Ma) indicate Late Cretaceous cooling below c. 300 °C. This relates to Late Cretaceous exhumation of the Troiseck-Floning Nappe following an Eo-Alpine metamorphic overprint at lower greenschist-facies metamorphic conditions. Based on the similar lithostratigraphy, analogous geological evolution and structure, the Troiseck-Floning Nappe represents the lateral extension of the Seckau Nappe. The new dataset also allows for correlations with other basement complexes that occur in the Western Carpathians.
特罗伊塞克-弗洛宁和罗斯科格尔山系(东阿尔卑斯山脉)的地质年代、地球化学和地质演化:揭示东阿尔卑斯山脉和西喀尔巴阡山脉之间的相似之处
特罗伊塞克-弗洛宁岩层和罗斯科格尔岩层是东阿尔卑斯山东部奥斯特阿尔卑斯单元的一部分。这两个岩层处于构造接触中,由二叠纪至中生代下绿泥石面变质玄武岩组成,但只有特罗伊塞克-弗洛宁岩层还包括二叠纪以前的结晶基底(特罗伊塞克复合体)。LA-ICP-MS U-Pb 锆石年龄、Rb-Sr 生铁年龄和地球化学数据揭示了这些构造单元从新元古代到中生代的地质演化过程。对特罗伊塞克复合体硅质碎屑变质岩进行的非铁质 U-Pb 锆石分析表明,火山碎屑岩序列的沉积年代为晚埃迪卡拉纪至早寒武纪。年龄分布与冈瓦纳东北边缘的位置相关。花岗岩侵入体的晚寒武纪结晶年龄(502.4 ± 6.8 Ma)以及晚寒武纪/奥陶纪岩浆作用和变质作用的证据表明,该地区位于一个活跃的板块边缘。泥盆纪晚期/石炭纪早期的伟晶岩岩钉(约 353 Ma)记录了瓦里斯山造山运动期间的多相叠加,这些岩钉是在瓦里斯山早期事件之后形成的,而宾夕法尼亚时期的叠加边缘和继承颗粒(约 320 Ma)则是瓦里斯山晚期变质作用的证据。Troiseck-Floning 和 Rosskogel 山脉的流纹岩到安山质火山岩(271-264 Ma),以及斑状花岗岩的侵入体(现在已转变为奥长片麻岩(271 Ma)),为二叠纪与裂谷有关的岩浆活动提供了证据,这种岩浆活动在东阿尔卑斯山和西喀尔巴阡山被广泛报道。掺铷锶生物岩年龄(75-74 Ma)表明晚白垩世的冷却温度低于约 300 °C。这与晚白垩世特罗伊塞克-弗洛宁斜长岩在低绿泥石派变质条件下经过东阿尔卑斯山变质叠压后的出露有关。基于相似的岩石地层学、类似的地质演化和构造,特罗伊塞克-弗洛宁断层代表了塞考断层的横向延伸。新的数据集还可以与西喀尔巴阡山脉的其他基底复合体进行关联。
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来源期刊
Swiss Journal of Geosciences
Swiss Journal of Geosciences 地学-地质学
CiteScore
4.50
自引率
12.90%
发文量
21
审稿时长
>12 weeks
期刊介绍: The Swiss Journal of Geosciences publishes original research and review articles, with a particular focus on the evolution of the Tethys realm and the Alpine/Himalayan orogen. By consolidating the former Eclogae Geologicae Helvetiae and Swiss Bulletin of Mineralogy and Petrology, this international journal covers all disciplines of the solid Earth Sciences, including their practical applications. The journal gives preference to articles that are of wide interest to the international research community, while at the same time recognising the importance of documenting high-quality geoscientific data in a regional context, including the occasional publication of maps.
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