Late Jurassic blueschist facies pebbles from the Western Carpathian orogenic wedge and paleostructural implications for Western Tethys evolution
Late Jurassic blueschist facies pebbles from the Western Carpathian orogenic wedge and paleostructural implications for Western Tethys evolution
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DOI：
10.1029/95tc00953
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发表时间：
1995-08
期刊：
影响因子：
4.2
通讯作者：
G. D. Piaz;S. Martin;I. Villa;G. Gosso;R. Marschalko
中科院分区：
文献类型：
--
作者：
G. D. Piaz;S. Martin;I. Villa;G. Gosso;R. Marschalko
尽管表面没有蛇绿岩片，但沿着皮耶尼-克利彭带（PKB）记录了一些失落的特提斯海洋的痕迹，这是一个狭窄的滑脱逆冲系统，缝合在内外喀尔巴阡山脉之间的逆压边界上。西喀尔巴阡山脉神秘的碰撞前演化可以从阿尔别世晚期到坎帕尼亚期的一些复理石质砾岩中得到解释，这些砾岩中有铬尖晶石颗粒、蛇绿质碎屑和蓝片岩相拉斑变质玄武岩的卵石，高原年龄为40Ar/39Ar（155.4±0.6 Ma）。其他碎屑成分以基底外灰岩卵石、弧火山岩和南部火成岩-变质基底岩为代表。我们的研究结果表明，自中侏罗世晚期以来，三叠纪瓦尔达尔（梅利亚塔）洋的亚纵向向北伸展及其俯冲，可能是在亚平宁-西阿尔卑斯特提斯的利古里亚-皮埃蒙特盆地的同期扩张与向西平衡的。这些跨时性的、大致平行的特提斯分支之间的横向运动联系，是由一条从瑞士-奥地利半岛到北喀尔巴阡山脉的左向东西走向的剪切带提供的。这一重建取代了经典的北、南两对洋盆和东部同源洋盆的模式，以及介于两者之间的Brianconnais-Hochstegen和Czorstin微大陆。晚侏罗世—早白垩世喀尔巴阡活动边缘的演化以俯冲变质作用和宽造山带的增生为特征；在这一时期，通过对PKB沉积单元的相分析推断出的浅沉到深沉的盆地很可能是由生长的楔块的个别部分所覆盖的。后来，一些发掘出的楔形蓝片岩蛇绿岩单元被抬升到地表，并在阿尔巴尼亚-坎帕尼亚期起到“外来脊”的作用，为弧前盆地提供碎屑。最后，自白垩纪晚期以来，碰撞楔块消失在内喀尔巴阡造山带盖下，并被并入喀尔巴阡造山带东移的基础设施中，成为一个隐蔽的古构造。
In spite of the absence of ophiolitic slices at the surface, some traces of the lost Tethys ocean are recorded along the Pieniny Klippen Belt (PKB), a narrow decollement thrust system sutured at the transpressive boundary between the Outer and Inner Carpathians. The enigmatic precollisional evolution of Western Carpathians can be deciphered from some late Albian to Campanian flysch conglomerates which display chrome spinel grains, ophiolitic detritus and pebbles of blueschist facies tholeiitic metabasalts yielding a 40Ar/39Ar plateau age of 155.4±0.6 Ma. Other detrital components are represented by extrabasinal pebbles of limestones, arc volcanics, and igneous to metamorphic basement rocks from southern sources. Our results suggest a markedly northward extension of the sublongitudinal Triassic Vardar (Meliata) Ocean and its subduction since the late Middle Jurassic, supposedly balanced westward by coeval spreading in the Ligurian-Piedmont basin of the Apennine-Western Alpine Tethys. A lateral kinematic connection between these diachronous and roughly parallel Tethys branches was provided on the north by a left-lateral east-west trending shear zone running from the Swiss-Austrian Penninic domain to the Northern Carpathians. This reconstruction replaces the classic model of two paired North Penninic and South Penninic oceanic basins and eastern homologues with the Brianconnais-Hochstegen and Czorstin microcontinents in between. The Late Jurassic-Early Cretaceous evolution of the Carpathian active margin was characterized by subduction metamorphism and accretion of a wide orogenic wedge; in this time, the shallowing to deeply subsiding basins inferred from facies analyses on the sedimentary units of the PKB were likely floored by individual sections of the growing wedge. Later, some exhuming blueschist ophiolitic units of the wedge were uplifted to the surface and functioned in the Albian-Campanian as an “exotic ridge” supplying clasts to the forearc basin. Finally, the colliding wedge became a cryptic paleostructure when, since the latest Cretaceous, it disappeared beneath the Inner Carpathian orogenic lid and was incorporated within the eastward moving infrastructure of the Carpathian orocline.