Abstract We compare and contrast the structural evolution of two successive internal thrusts, the Main Central thrust (MCT) and the Pelling-Munsiari thrust (PT), from the crystalline core of the Sikkim Himalaya in the context of progressive deformation involving a footwall Lesser Himalayan duplex; the PT is its roof thrust. The mylonitic foliations in both the shear zones are overprinted by successive cleavages. The youngest cleavage from the PT zone continues within the hangingwall MCT sheet that records one additional cleavage possibly indicating time-transgressive cleavage development. The cleavages become steeper while their intensity decreases structurally higher up within individual thrust sheets. The Rs-values and angular shear strain decrease from the mylonite zones to structurally higher up within the sheets. Both the shear zones are Type II with decelerating strain paths. Rs-θ′ relationships and microstructures indicate thrust-parallel stretch is greater than thrust-perpendicular component. Both the shear zones record strain partitioning with lesser competent mylonite domains recording higher Rxz, and a greater proportion of simple-shear than the protomylonite domains. The shear zones recorded the growth of the duplex during progressive deformation that contributed to pure-shear dominated general-shear, higher flattening strain and greater translation on its roof thrust, the PT, than the overlying MCT.

中文翻译：

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通过两个连续的内部逆冲推力跟踪造山楔的渐进变形：从结构、变形剖面、应变和涡度的主要中央逆冲断层 (MCT) 和 Pelling-Munsiari 逆冲断层 (PT)、锡金喜马拉雅褶皱逆冲带的洞察

摘要 我们在涉及下盘小喜马拉雅山脉的渐进变形背景下，比较和对比了来自锡金喜马拉雅结晶核的两个连续内部逆冲推力（MCT）和 Pelling-Munsiari 逆冲推力（PT）的结构演化。双工；PT 是它的顶推力。两个剪切带中的糜棱叶理被连续的劈裂叠印。来自 PT 区的最年轻的解理在上壁 MCT 表内继续，记录了一个额外的解理，可能表明时间越界解理的发展。劈理变得更陡峭，而它们的强度在单个推力片内的结构更高处降低。Rs 值和角剪切应变从糜棱岩带向结构上更高的薄片内减小。两个剪切区都是具有减速应变路径的 II 型。Rs-θ' 关系和微观结构表明推力平行拉伸大于推力垂直分量。两个剪切带都记录了应变分配，其中较弱的糜棱岩域记录了更高的 Rxz，并且比原糜棱岩域的简单剪切比例更大。剪切带记录了双相在渐进变形过程中的增长，与上覆的 MCT 相比，这有助于纯剪切主导的一般剪切、更高的压扁应变和更大的顶推力 PT 平移。两个剪切带都记录了应变分配，其中较弱的糜棱岩域记录了更高的 Rxz，并且比原糜棱岩域的简单剪切比例更大。剪切带记录了双相在渐进变形过程中的增长，与上覆的 MCT 相比，这有助于纯剪切主导的一般剪切、更高的压扁应变和更大的顶推力 PT 平移。两个剪切带都记录了应变分配，其中较弱的糜棱岩域记录了更高的 Rxz，并且比原糜棱岩域的简单剪切比例更大。剪切带记录了双相在渐进变形过程中的增长，与上覆的 MCT 相比，这有助于纯剪切主导的一般剪切、更高的压扁应变和更大的顶推力 PT 平移。