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An introduction to Himalayan tectonics: a modern synthesis


The Himalaya resulted from collision of the Indian plate with Asia and is well known as the highest, youngest, and one of the best studied continental collision orogenic belts. It is frequently used as the type example of a continental collision orogenic belt in studies of older Phanerozoic orogenic belts. The beauty of the Himalaya is that, on a broad scale they form a relatively simple orogenic belt. The major structural divisions, the Indus-(Yarlung Tsangpo) suture zone, the Tethyan Himalaya sedimentary units, Greater Himalaya Sequence (GHS) metamorphic rocks, the Lesser Himalaya (LH) fold and thrust belt, and the Sub-Himalaya Siwalik molasse basin are present along the entire 2000 km length of the Himalaya (Figs. 1, 2). Likewise, the major structures, the Indus – Yarlung Tsangpo suture with north-vergent backthrusts, the South Tibetan Detachment (STD) low-angle normal fault, locally called the Zanskar Shear zone (ZSZ) in the west, the Main Central Thrust (MCT) zone, and the Main Boundary Thrust (MBT) are all mapped along the entire length of the mountain belt between the western (Nanga Parbat) and eastern (Namche Barwa) syntaxes. Klippen of low-grade or unmetamorphosed sedimentary rocks lie above the GHS high-grade rocks in places (e.g. Chamba klippe in India; Lingshi klippe in Butan), and far-travelled klippen of GHS rocks occur in places south of the main MCT and GHS rocks (e.g. Darjeeling klippe).