Abstract Reconstruction of the Western Himalaya requires three subduction systems operating beneath the Spong arc, Dras–Kohistan arc and the Asian continent during the Late Cretaceous–Paleocene. The timing of the closure of the Neo-Tethys Ocean along the Indus Suture Zone (ISZ) in Ladakh and south Tibet has been proposed to be as old as c. 65 Ma and as young as c. 37 Ma. The definition of the India–Asia collision can span >15 myr from the first touching of Indian continental crust with Asian crust to the final marine sedimentation between the two plates. There is good geological evidence for a Late Cretaceous–Early Paleocene phase of folding, thrusting and crustal thickening of Indian Plate shelf carbonates associated with obduction of ophiolites. There is no geological evidence of any oceanic ‘Greater Indian Basin’ separating the northern Tethyan and Greater Himalaya from India. There is clear evidence to support final ending of marine sedimentation along the ISZ at 50 Ma (planktonic foraminifera zone P7–P8). There is no evidence for diachroneity of collision along the Pakistan–Ladakh–South Tibet Himalaya. The timing of ultrahigh-pressure metamorphism cannot be used to constrain India–Asia collision, and the timing of high-grade kyanite- and sillimanite-grade metamorphism along the Greater Himalaya can only give a minimum age of collision.

Abstract The Pakistan part of the Himalaya has major differences in tectonic evolution compared with the main Himalayan range to the east of the Nanga Parbat syntaxis. There is no equivalent of the Tethyan Himalaya sedimentary sequence south of the Indus–Tsangpo suture zone, no equivalent of the Main Central Thrust, and no Miocene metamorphism and leucogranite emplacement. The Kohistan Arc was thrust southward onto the leading edge of continental India. All rocks exposed to the south of the arc in the footwall of the Main Mantle Thrust preserve metamorphic histories. However, these do not all record Cenozoic metamorphism. Basement rocks record Paleo-Proterozoic metamorphism with no Cenozoic heating; Neo-Proterozoic through Cambrian sediments record Ordovician ages for peak kyanite and sillimanite grade metamorphism, although Ar–Ar data indicate a Cenozoic thermal imprint which did not reset the peak metamorphic assemblages. The only rocks that clearly record Cenozoic metamorphism are Upper Paleozoic through Mesozoic cover sediments. Thermobarometric data suggest burial of these rocks along a clockwise pressure–temperature path to pressure–temperature conditions of c. 10–11 kbar and c. 700°C. Resolving this enigma is challenging but implies downward heating into the Indian plate, coupled with later development of unconformity parallel shear zones that detach Upper Paleozoic–Cenozoic cover rocks from Neoproterozoic to Paleozoic basement rocks and also detach those rocks from the Paleoproterozoic basement.

Abstract Reconstruction of the protolith lithostratigraphy of amphibolite-facies metasedimentary rocks of the Greater Himalayan Series (GHS) in Nepal documents a single, long-lived passive-margin succession that was deposited along the northern margin of the Indian Craton. In the Langtang area, Paleoproterozoic gneisses are unconformably overlain by a succession of upper Neoproterozoic–Ordovician fluvio-deltaic quartzite, basinal pelite and psammitic beds that grade upsection into micaceous semipelite and pelite. U–Pb zircon geochronology yields maximum depositional ages between c. 815 and 460 Ma for the GHS in Langtang. Regional variations in the composition and thickness of the GHS along the length of the Himalaya are attributed to siliciclastic depocentres centred on Zanskar in northern India, Langtang and Everest in central to western Nepal, which contrast with coeval marine carbonate shelf deposition in the Annapurna region. The protolith lithostratigraphy documented for Langtang provides a coherent framework for interpreting subsequent Cenozoic Himalayan deformation, specifically the homogeneously distributed layer-normal shortening (i.e. flattening) and layer-parallel stretching (i.e. transport-parallel stretching) that characterizes the GHS. Within the context of a single protracted northern Indian marginal sedimentary succession, the distinction between the Lesser, Greater and Tethyan Himalaya is structural rather than lithostratigraphic in origin.

Abstract Microstructural and petrological data from >60 samples, collected by L.R. Wager in 1933, have been used alongside existing data to investigate temperature gradients and deformational style in four profiles across the South Tibetan Detachment shear zone, over a north–south distance of 35 km in the Mt Everest area, east-central Himalaya. The ductile shear zone, defined on petrographic criteria, extends for c. 900 m beneath the brittle Qomolangma Detachment (QD). New thermobarometry from the north flank of Mt Everest reveals a gradient from 440°C at the QD down to samples recording peak conditions around 650°C, 5.5 kbar. The upper limit of leucogranite sheets forms an approximately isothermal surface at 600–650°C within the developing shear zone. The recrystallized grain size of quartz shows a systematic increase down-section in four transects. Profiles of deformation temperature reveal gradients of up to 200°C km −1 whose formation and preservation required a combination of processes: a shear zone active for a short period (≤18–15.5 Ma) at high strain rates, with a component of vertical shortening, and a contribution of latent heat from emplacement of sheeted granites. The likely horizontal displacement was >40 km, with up to 10 km of vertical exhumation.

Abstract The genesis of mineral deposits has been widely linked to specific tectonic settings, but has less frequently been linked to tectonic processes. Understanding processes of oceanic and continental collision tectonics is crucial to understanding key factors leading to the genesis of magmatic-, metamorphic-, hydrothermal-, and sedimentary-related mineral deposits. Geologic studies of most ore deposits typically focus on the final stages of concentration and emplacement. The ultimate source (mantle, lower crust, upper crust) of mineral deposits in many cases remains more cryptic. Uniquely, along the Tethyan collision zones of Asia, every stage of the convergence process can be studied from the initial oceanic settings where ophiolite complexes were formed, through subduction zone and island-arc settings with ultrahigh- to high-pressure metamorphism, to the continental collision settings of the Himalaya, and advanced, long-lived collisional settings such as Afghanistan, the Karakoram Ranges, and the Tibetan plateau. The India-Asia collision closed the intervening Neotethys ocean at ~50 Ma and resulted in the formation of the Himalayan mountain ranges, and increased crustal thickening, metamorphism, deformation, and uplift of the Karakoram-Hindu Kush ranges, Tibetan plateau, and older collision zones across central Asia. Metallogenesis in oceanic crust (hydrothermal Cu-Au; Fe, Mn nodules) and mantle (Cr, Ni, Pt) can be deduced from ophiolite complexes preserved around the Arabia/India-Asia collision (Oman, Ladakh, South Tibet, Myanmar, Andaman Islands). Tectonic-metallogenic processes in island arcs and ancient subduction complexes (VMS Cu-Zn-Pb) can be deduced from studies in the Dras-Kohistan arc (Pakistan) and the various arc complexes along the Myanmar-Andaman segment of the collision zone. Metallogenesis of Andean-type margins (Cu-Au-Mo porphyry; epithermal Au-Ag) can be seen along the Jurassic-Eocene Transhimalayan ranges of Pakistan, Ladakh, South Tibet, and Myanmar. Large porphyry Cu deposits in Tibet are related to both precollisional calc-alkaline granites and postcollisional alkaline adakite-like intrusions. Metallogenesis of continent-continent collision zones is prominent along the Myanmar-Thailand-Malaysia Sn-W granite belts, but less common along the Himalaya. The Mogok metamorphic belt of Myanmar is known for its gemstones associated with regional high-temperature metamorphism (ruby, spinel, sapphire, etc). In Myanmar it is likely that extensive alkaline magmatism has contributed extra heat during the formation of high-temperature metamorphism. This paper attempts to link metallogeny of the Himalaya-Karakoram-Tibet and Myanmar collision zone to tectonic processes derived from multidisciplinary geologic studies.