India-Asia collision: A further discussion of N-S- and E-W-trending detachments and the orogenic mechanism of the modern Himalayas.
India-Asia collision: A further discussion of N-S- and E-W-trending detachments and the orogenic mechanism of the modern Himalayas.
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发表时间：
2006
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通讯作者：
Cheng Fang-yuan
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作者：
Cheng Fang-yuan
印度-亚洲碰撞形成了喜马拉雅增生带，由北向南由特提斯-喜马拉雅（THM）、大喜马拉雅（GHM）、小喜马拉雅（LHM）和次喜马拉雅（SHM）亚带组成。成分、变质作用和演化的比较，喜马拉雅增生带变质基底和盖层的变形机制和形成时代表明，位于喜马拉雅增生带北方边缘的藏南拆离体（STD）向北延伸至喜马拉雅增生带之下，并与形成于650℃的康玛-拉盖岗日拆离体（KLD）相连，具有北向构造变形的性质。地壳部分熔融和物质上涌导致花岗岩侵位，KLD隆升，形成Kangmar-Lhagoi Kangri片麻岩穹隆。在北方变质基底与盖层之间存在近东西向的近水平韧性拆离构造（普兰-吉隆-聂拉木-亚东地区），以东西向伸展线理和缓倾糜棱岩面理为特征，表现为东向水平滑动剪切方向;而在GHM次级构造南部的主中央冲断带（MCT）北侧附近，发育有韧性走滑-逆冲型压扭断层。从南到北，GHM次陆壳具有逆冲→斜冲→东西向伸展→斜向伸展→南北向伸展的连续变形和过渡特征，是垂直挤压与侧向挤压耦合造山机制下复合变形的响应。喜马拉雅造山带东西向和南北向断裂的存在，为进一步探讨喜马拉雅现代造山机制提供了依据。
India-Asia collision formed the Himalaya accretionary terrane, which is composed from north to south of the Tethys-Himalaya (THM), Greater Himalaya (GHM), Lesser Himalaya (LHM) and Subhimalaya (SHM) subterranes. Comparison of the compositions, metamorphisms and evolutions, deformation mechanisms and formation ages of metamorphic basements and covers in the Himalaya accretionary terrane indicates that the southern Tibet detachment (STD) on the northern margin of the GHM subterrane extends northward beneath the THM subterrane and is connected with the Kangmar-Lhagoi Kangri detachment (KLD) that formed at 650℃ and has the nature of north-directed shear slip motion, and that partial melting of the crust and material upwelling resulted in granite emplacement and uplift of the KLD, forming the Kangmar-Lhagoi Kangri gneiss domes. An E-W-trending subhorizontal ductile detachment (GHD) is found between the metamorphic basement and cover in the northern part (Burang-Gyirong-Nyalam-Yadong area) of the GHM subterrane, which is characterized by E-W stretching lineation and gently dipping mylonitic foliation and shows the east-directed horizontal slip shear sense; whereas near the north side of the Main Central Thrust (MCT) in the southern part of the GHM subterrane there occur ductile strike slip-thrust faults of transpressional nature. From south to north the GHM subterrane has the features of continuous deformation and transition from Thrust→oblique thrust→E-W trending extention→oblique extention→S-N trending extention, which are the response to the composite deformation under the orogenic mechanism of coupling of vertical and lateral extrusions. The existence of the E-W- and N-S-trending detachments in the Himalaya terrane provide a basis for a further discussion of the modern orogenic mechanism of the Himalayas.