The Higher Himalayan Crystallines (HHC) in the Siyom river section of eastern Arunachal Himalaya, display top-to- ESE compressional ductile shear from Pene to Menchuka. In this part of the Himalayan Metamorphic Belt (HMB), the base of the Main Central Thrust (MCT) is the southern boundary of the ductile shear fabrics in HHC. Across the MCT, a significant break in the grade of metamorphism is observed between the HHC and the Lesser Himalayan Sequences (LHS). The ductile shear fabrics documented in the HHC are primary S-C and S-C’ fabrics, asymmetric folds, porphyroclasts and porphyrobalsts, brittle-ductile structures and asymmetric boudins. Three phases of folding representing three deformation episodes (D1-D3) in HHC are recorded in the area. The rocks of the HHC in Siyom valley are completely transposed by the D2 deformation into NNW dipping C- plane. Ductile shear represented by grain scale structures include sigmoidal foliation, rotation of the inclusion trails in garnet porphyroblasts, asymmetric folds with consistent top-to-ESE sense of shear. The ductile to brittle-ductile shear fabrics in the area indicate that the thrust sense of shear in the HHC is consistent without any shear sense reversal from Pene to Menchuka. These compressional shear fabrics provide invaluable field evidences for constraining the evolution of this part of the Higher Himalaya.

中文翻译：

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印度阿鲁纳恰尔喜马拉雅东部 Siyom 山谷高喜马拉雅山的推力剪切感和剪切带织物

阿鲁纳恰尔喜马拉雅东部 Siyom 河段的高喜马拉雅结晶 (HHC) 显示从 Pene 到 Menchuka 的顶部到 ESE 压缩韧性剪切。在喜马拉雅变质带 (HMB) 的这一部分，主中央逆冲断层 (MCT) 的底部是 HHC 中韧性剪切织物的南边界。在整个 MCT 中，在 HHC 和小喜马拉雅层序 (LHS) 之间观察到变质作用等级的显着中断。HHC 中记录的韧性剪切织物是主要的 SC 和 S-C' 织物、不对称褶皱、斑岩碎屑和斑状硬质弹、脆性韧性结构和不对称布丁。该区域记录了代表 HHC 中三个变形事件 (D1-D3) 的三个折叠阶段。Siyom 山谷 HHC 的岩石通过 D2 变形完全转置到 NNW 倾斜的 C 平面。以晶粒尺度结构为代表的韧性剪切包括 S 形叶理、石榴石斑状体中包裹体轨迹的旋转、具有一致的顶部到 ESE 剪切感的不对称褶皱。该区域的韧性到脆性-韧性剪切织物表明 HHC 中的剪切推力感是一致的，从 Pene 到 Menchuka 没有任何剪切感反转。这些压缩剪切织物为限制高喜马拉雅山脉这部分的演化提供了宝贵的现场证据。该区域的韧性到脆性-韧性剪切织物表明 HHC 中的剪切推力感是一致的，从 Pene 到 Menchuka 没有任何剪切感反转。这些压缩剪切织物为限制高喜马拉雅山脉这部分的演化提供了宝贵的现场证据。该区域的韧性到脆性-韧性剪切织物表明 HHC 中的剪切推力感是一致的，从 Pene 到 Menchuka 没有任何剪切感反转。这些压缩剪切织物为限制高喜马拉雅山脉这部分的演化提供了宝贵的现场证据。