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首页> 外文OA文献 >Small-scale polygenetic mélanges in the Ligurian accretionary complex, Northern Apennines, Italy, and the role of shale diapirism in superposed mélange evolution in orogenic belts
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Small-scale polygenetic mélanges in the Ligurian accretionary complex, Northern Apennines, Italy, and the role of shale diapirism in superposed mélange evolution in orogenic belts

机译：意大利北部亚平宁山脉利古里亚增生复合体中的小型多基因混杂岩以及页岩成岩作用在造山带混杂混杂岩演化中的作用

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The Argille varicolori (Varicolored scaly clays) of the External Ligurian Units of the Northern Apennines have been widely described as a typical unmetamorphosed broken formation (i.e., a chaotic unit without exotic blocks), produced by offscraping and tectonic imbrication during the evolution of the Ligurian accretionary wedge. Geological mapping and integrated structural and stratigraphic observations show that the Argille varicolori consist of diverse types of small-scale mélanges (non-mappable at a 1:25,000 scale) forming a composite chaotic unit, in which the superposition of tectonic, sedimentary and diapiric processes resulted in the occurrence of polygenetic chaotic bodies at different scales. These mélange units record the evolution of the Ligurian accretionary wedge from subduction to collision and intracontinental deformation. Tectonically Disrupted Body 1 (TDB1) comprises boudinage and pinch-and-swell structures formed by layer-parallel extension/contraction at the wedge front of the Ligurian accretionary complex during the late Cretaceous–middle Eocene. It is interleaved with non-mappable Gravity-driven Chaotic Bodies (GCB) developed during alternating episodes of accretion and removal of material at the wedge front. The late Oligocene–early Miocene out-of-sequence thrusting related to the collisional episodes in the Apennines overprinted the previously formed chaotic bodies and formed a polygenetic tectonic mélange (Tectonically Disrupted Body 2, TDB2). This unit is characterized by a structurally ordered block-in-matrix fabric and by the gradual decrease of stratal disruption away from the regional thrust. Overpressurized fluids concentrated along the shear surfaces, and the scaly cleavage planes facilitated the diapiric upward movement of unconsolidated sediments in the early Miocene. This process produced non-mappable shale dike injections (DDB1) and mappable Diapirically Disrupted Bodies (DDB2), which show an internal zonation of deformation. This deformation reworked the previously formed chaotic bodies. Although some of these polygenetic mélanges cannot be mapped at a 1:25,000 scale, their careful documentation provides a better understanding of time-progressive, scale-independent mélange-forming processes.
机译：北亚平宁山脉外部利古里亚单元的Argille varicolori（杂色鳞状粘土）已被广泛描述为典型的未变质的破碎构造（即，没有外来块的混沌单元），是由利古里亚演化过程中的上覆和构造成岩作用产生的增生楔形。地质填图和综合的结构和地层观测结果表明，变色阿尔吉山脉由各种类型的小混杂岩（不可映射的比例为1：25,000）组成一个复合混沌单元，其中构造，沉积和二叠纪过程叠加导致了不同规模的多基因混沌体的出现。这些混杂单元记录了利古里亚增生楔从俯冲到碰撞和洲内变形的演变。构造扰动体1（TDB1）包括白垩纪至中新世晚期，在利古里亚增生复合体楔前的层平行伸展/收缩形成的脉状构造和夹挤结构。它与在楔形前部积聚和移除材料的交替过程中开发的不可映射的重力驱动混沌体（GCB）交错。与亚平宁山脉碰撞事件有关的渐新世-中新世晚期逆冲推覆作用覆盖了先前形成的混沌体，形成了多基因构造混杂体（Tectonically Disrupted Body 2，TDB2）。该单元的特征是结构有序的矩阵中的块状结构，以及远离区域推力的地层破坏逐渐减少。超压流体沿剪切面集中，并且鳞片状的开裂面促进了中新世早期未固结沉积物的底基向上运动。此过程产生了不可映射的页岩堤防注入（DDB1）和可映射的二叠纪扰动体（DDB2），显示出内部变形带。这种变形重新加工了先前形成的混沌体。尽管其中一些多基因混杂体无法以1：25,000的比例进行映射，但它们仔细的文档可以更好地理解时间渐进的，与比例无关的混杂体形成过程。

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