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Meliatic blueschists and their detritus in Cretaceous sediments: new data constraining tectonic evolution of the West Carpathians
Swiss Journal of Geosciences ( IF 1.8 ) Pub Date : 2018-11-22 , DOI: 10.1007/s00015-018-0330-7
Dušan Plašienka , Štefan Méres , Peter Ivan , Milan Sýkora , Ján Soták , Alexander Lačný , Roman Aubrecht , Simona Bellová , Tomáš Potočný

The Western Carpathian Meliata Superunit (Meliaticum) includes a heterogeneous group of units—the blueschist-facies Bôrka Nappe and the very low-grade chaotic complexes—polygenous mélange containing material derived from various tectonic settings (Jaklovce Unit) and Jurassic oceanic sediments with olistostrome bodies (Meliata Unit s.s.). The high pressure/low temperature (HP/LT) metamorphism, development of tectonic mélanges and synorogenic sediments took place simultaneously during the Middle–Late Jurassic in connection with closing of the Meliata Ocean. We present some new data concerning composition of variegated mélanges related to the subduction–accretion processes of the Meliata Ocean and its continental margins. The polygenous mélange contains a mixture of fragments of HP/LT up to unmetamorphosed sedimentary and volcanic rocks, including blueschist-facies radiolarites. New electron microprobe chemical age data of monazites from metasediments of the Bôrka Nappe cluster in two peaks—earliest Cretaceous ages are interpreted in terms of post-exhumation, renewed burial during formation of the Meliatic accretionary wedge. The mid-Cretaceous ages might record the thermal relaxation during the thick-skinned nappe stacking and exhumation of the neighbouring Veporic metamorphic dome. In addition, we describe two distinct types of tourmalines and epidotes occurring in the Bôrka blueschists that document the prograde HP and retrograde LP metamorphic events. Detritus of the blueschist-facies rocks appears for the first time in the heavy mineral spectra of the Barremian–Aptian platform limestones. These limestones occur as clasts, together with glaucophanite pebbles, in the Albian–Cenomanian flysch formations of the Pieniny Klippen Belt (Klape Unit). We also review occurrences of other blueschist and ophiolitic erosional products in Cretaceous clastic formations and suggest that all have a Meliatic provenance.

中文翻译:

白垩纪沉积物中的ia虫蓝粉岩及其碎屑:新数据限制了西喀尔巴阡山脉的构造演化

西喀尔巴阡山脉的Meliata超级单元(Meliaticum)包括一组异质单元-蓝片岩相博尔卡纳普和极低品位的混沌复合体-多源混杂岩,包含源自各种构造环境的物质(Jaklovce单元)和侏罗纪海洋沉积物,并具有卵泡造口。 (Meliata Unit ss)。在中晚侏罗世时期,随着Meliata海洋的关闭,高压/低温(HP / LT)变质作用,构造混杂岩的发育和成因沉积物同时发生。我们提供了一些新数据,这些数据涉及与Meliata海洋及其大陆边缘的俯冲-增生过程相关的杂色混杂物的组成。混杂的混杂物包含HP / LT碎片的混合物,直至未变质的沉积岩和火山岩,包括蓝片岩相放射虫。来自博尔卡纳普团簇中沉积物的独居石在两个峰中的新电子探针化学年龄数据是最早的白垩纪时代,其解释为回火后,在Mel状增生楔形成过程中重新埋葬。白垩纪中期可能记录了厚皮的尿布堆积和邻近的Veporic变质穹顶发掘期间的热弛豫。此外,我们描述了发生在博尔卡blueschists中的两种不同类型的电气石和epi石,它们记录了正向的HP和逆向的LP变质事件。蓝片岩相碎屑首次出现在Barremian-Aptian平台石灰岩的重矿物光谱中。这些石灰石与青石卵石一起作为碎屑出现,Pieniny Klippen带(克拉佩单元)的阿尔比亚-西诺曼尼亚复理岩层。我们还回顾了在白垩纪碎屑岩地层中出现的其他blueschist和脂石质侵蚀产物,并暗示它们均具有Meliatic物源。
更新日期:2018-11-22
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