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Making Mountains

The Alpine – Himalayan mountain ranges formed during the closing of the Tethys Ocean that once separated the southern Gondwana continents from the northern Asian continental masses. Various stages in the mountain building process are beautifully exposed along the ranges. The earliest stage of orogeny is exemplified by the obduction of the giant Oman ophiolite complex onto the passive continental margin of Arabia. The earliest stage of the continent – continent collision process is exemplified by the Zagros Ranges of SW Iran with large-scale, but simple folding of the entire Phanerozoic sedimentary sequence. The Arabian Gulf foreland region of Zagros and Oman form the richest oil and gas province on Earth, with many giant oil fields formed by fold and fault-related traps. The more mature stages of continental collision are seen along the India – Asia collision belt. 

Along the Indian plate margin the Himalayan Ranges of India, Nepal and Bhutan show regional metamorphism, granite melting and large-scale thrust and normal faulting. Ductile extrusion of the partially molten middle crust has occurred along the Greater Himalaya during the Late Oligocene – Early Miocene, a process known as Channel Flow. Along the Asian plate margin, the Karakoram Ranges of north Pakistan show the thickest continental crust on Earth, up to 85 km thick, with widespread and long-lasting metamorphism, and massive lower crustal melting in the Miocene to form the Baltoro granite batholith, and deep, active subduction of the continental margin in the Hindu Kush. 

Whereas the Karakoram Ranges have suffered extreme rates of crustal thickening, erosion and exhumation, the Tibetan Plateau shows only upper crustal levels with large-scale strike-slip faults and extensional graben cutting through sedimentary rocks. The role of crustal thickening and thrusting along the Himalaya is of considerably greater importance than the role of lateral continental extrusion along strike-slip faults (Altyn Tagh, KunLun, Karakoram, Red River faults). Highly potassic volcanism, characteristic products of the hot upper mantle beneath thick crust, is present scattered all over the Tibetan Plateau and Yunnan. Processes determined from studying the geology of these Tethyan mountain ranges can be used to compare with the geology of older orogenic belts that may also have suffered continental collision, belts such as the Trans-Hudson orogen of northern Canada, the Limpopo belt of southern Africa, and the Scottish Highlands.


Mike Searle


Mike Searle is a Lecturer in the Department of Earth Sciences, Oxford University and a Senior Research Fellow of Worcester College, Oxford. He obtained his PhD in 1980 working on structures and metamorphism of rocks beneath the Oman Ophiolite. He has continued working in Oman and the United Arab Emirates since then, as well as in Syria and Jordan. He has also worked over 25 years along the Himalayan ranges of India, Nepal, Sikkim and Bhutan, as well as along the Karakoram and Hindu Kush Ranges of northern Pakistan and Afghanistan. More recently he has extended his studies of the Himalaya and Tibet into Burma, Thailand and Vietnam. His research integrates extensive field mapping and structural geology with geochronology and thermobarometry, with the aim of unraveling the large-scale evolution of mountain belts.