A geological survey and morphological analysis of quartz grains were performed to investigate the distribution of ductile deformation caused by the Himalayan Main Central Thrust (MCT) around Dhankuta, southeastern Nepal. The MCT was mapped as the lithological boundary between the gneiss of the Higher Himalayan Crystalline (HHC) as the hanging wall and the inverted metamorphic sequence of the Lesser Himalayan Sediments (LHS) as the footwall. The MCT was found to truncate various stratigraphic levels of LHS and cuts a map‐scale gentle fold developed in the LHS. Ductile deformation was quantified by fractal dimension between size and perimeter of dynamically recrystallized quartz grains in bedded metaquartzite intercalated in both HHC and LHS. Serrate and polygonal shapes of quartz indicate large and small strain rates, respectively, when the temperature during ductile deformation was assumed to be uniform. A peak of strain rate was found at the lithological boundary with the peak width of ca. 500 m. Such a thin shear zone is favorable for producing frictional heat to promote the inverted metamorphism in LHS.

中文翻译：

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尼泊尔东南部喜马拉雅山尿布前部主中央冲断带周围韧性变形的分布

进行了石英颗粒的地质调查和形态分析，以调查由尼泊尔东南部Dhankuta周围的喜马拉雅主中心推力（MCT）引起的韧性变形的分布。MCT被映射为高喜马拉雅结晶体（HHC）的片麻岩作为悬壁和小喜马拉雅沉积物（LHS）的倒置变质序列作为底壁之间的岩性边界。发现MCT可以截断LHS的各种地层水平，并切开在LHS中形成的地图级平缓褶皱。通过在HHC和LHS中插层的层状偏石英岩中动态再结晶石英晶粒的尺寸和周长之间的分形维数，可以确定延性变形。石英的锯齿形和多边形分别表示大应变率和小应变率，假设塑性变形过程中的温度均匀。在岩性边界处发现了一个应变率的峰值，峰值宽度为。CA。500米 这样的薄剪切区有利于产生摩擦热以促进LHS中的反向变质。