The Alpine Balkanides in Bulgaria are developed over Variscan orogenic fragments, which are variously affected by late-stage thick-skinned thrust tectonics. Often, these fragments hold both Variscan and Alpine structural records. А key area to shed light on important aspects of the tectonic evolution of the external parts of the Alpine Balkanide orogen is the Vezhen Massif in the Central Stara Planina Mountains. Although it is built exclusively of Paleozoic crystalline rocks, its structure was long considered as an example of intense mid Eocene to early Oligocene (Late Alpine) shortening. Detailed fieldwork in the area shows a more complicated tectonic framework and provides evidence of a polyphase structural evolution, involving an important stage of Variscan metamorphism and deformation and two stages of north-vergent Alpine shortening. The Stargel-Boluvanya Tectonic Zone that affects the western Vezhen Massif is one of the most important Variscan structures in the Balkan fold-and-thrust belt. Structural data indicate that the metamorphic basement records initial top-to-north thrusting, followed by further shortening, which led to folding and localized strike-slip deformation. The Variscan syn-metamorphic fabric is cross-cut by several post-kinematic igneous bodies of late Carboniferous to Permian ages. The tectonic history continues with a development of a network of greenschist facies north-vergent mylonitic zones for which an Early Alpine (post-late Permian but pre-Late Cretaceous) age is assumed. Late Alpine north-vergent thrusting is evident only on the eastern and northern flanks of the Vezhen Massif. In a broad structural context, the documented record in the basement rocks of the Vezhen Massif is comparable with those of the external massifs of the Alps and Iberia.

中文翻译：

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巴尔干半岛外侧的 Variscan 基底构造和高山剪切带：来自保加利亚 Central Stara Planina 山 Vezhen 地块的结构数据


保加利亚的阿尔卑斯巴尔干半岛是在 Variscan 造山碎片上发育的，这些碎片受到晚期厚层逆冲构造的不同影响。通常，这些碎片同时保存 Variscan 和 Alpine 的结构记录。阐明阿尔卑斯山巴尔干半岛造山带外部构造演化重要方面的关键区域是位于 Stara Planina 山脉中部的 Vezhen 地块。虽然它完全由古生代结晶岩建造，但其结构长期以来一直被认为是始新世中期至渐新世早期（晚阿尔卑斯山）强烈缩短的例子。该地区的详细田野工作显示了更复杂的构造框架，并提供了多相结构演化的证据，涉及 Variscan 变质和变形的重要阶段以及北向阿尔卑斯山缩短的两个阶段。影响韦任地块西部的 Stargel-Boluvanya 构造带是巴尔干褶皱和逆冲带中最重要的 Variscan 构造之一。结构数据表明，变质基底记录了最初的自上而北的逆冲，然后进一步缩短，这导致了折叠和局部走滑变形。Variscan syn-metamorphic 织物由石炭纪晚期至二叠纪的几个后运动火成岩体横切。构造历史继续发展，形成了一个绿色片岩相网络，即北向糜棱岩带，其推测为早阿尔卑斯山（晚二叠世后但晚白垩纪前）时代。晚期阿尔卑斯山北向冲刺仅在 Vezhen Massif 的东侧和北侧很明显。 在广泛的结构背景下，Vezhen Massif 基岩的记录与阿尔卑斯山和伊比利亚山的外部地块的记录相当。