Optical Offsets 7To determine the co-seismic horizontal displacement field due to the Gorkha earthquake, we use optical 8 image correlation to measure the displacement of pixels between pre-and post-earthquake satellite im-9 ages. We are able to resolve sub-pixel displacements of less than 1/15th of the Landsat8 pixel resolu-10 tion (i.e. < 1 m) using the COSI-Corr software package images, which helps to increase the signal-to-noise ratio, (4) the deformation field is resolved perpendicular to 16 the look angle (i.e. the horizontal plane for nadir images), thereby providing measurements complementary 17to InSAR (which is sensitive to vertical displacements), (5) the nadir look angle is insensitive to topographic 18 residuals produced during orthorectification of the satellite images (such residuals are produced when a lower 19 resolution digital elevation model, DEM, is used during the orthorectification process), and (5) Landsat8 20 images are freely available from the USGS as an orthorectified product -see 5 for additional details. 21Landsat8 images are typically acquired at 10am each morning. Consequently, the illumination charac-22 teristics (i.e. shadows) vary in every image acquired throughout the year according to the position of the 23 sun. Because shadows produce sharp edges in satellite images, they strongly influence the correlation. There-24 fore, to reduce the effect of differing shadows biasing the displacement field, we correlate Landsat8 images 25 acquired at a similar time of year, thereby yielding images with similar illumination characteristics (i.e. sun 26 azimuth and elevation). In addition to having similar illumination characteristics, we also require images with 27 minimal cloud cover. From the Landsat8 archive, we found two suitable images from the (pre-earthquake) 2813th May 2014 (sun azimuth: 109• , sun elevation: 68

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Mica and hornblende K‐Ar and Ar‐Ar data are presented from each of the three crustal components of the Himalayan collision zone in North Pakistan: the Asian plate, the Kohistan Island Arc, and the Indian plate. Together with U‐Pb and Rb‐Sr data published elsewhere these new data (1) date the age of suturing along the Northern Suture, which separates Kohistan from Asia, at 102–85 Ma; (2) establish that the basic magmatism in Kohistan, which postdates collision along the Northern Suture, predates 60 Ma, and that the later granite magmatism spanned a range of 60–25 Ma; (3) show that uplift amounts within Kohistan are greater toward the Nanga Parbat syntaxis than away from it and that rate of uplift near the syntaxis increased over the last 20 Ma to a current figure of about 5.5 mm a year; (4) show that much of southern Kohistan had cooled to below 500°C by 80 Ma and that the major deformation which imbricated Kohistan probably predated 80 Ma and certainly predated 60 Ma and was related to the Kohistan‐Asia collision rather than the Kohistan‐India one; (5) imply that uplift along the Hunza Shear in the Asian plate together with imbrication of the metamorphics in its hanging wall took place at about 10 Ma and was associated with breakback thrusting in the hanging wall of the Main Mantle Thrust; (6) suggest that the Indian plate has a lengthy pre‐Himalayan history with an early metamorphism at about 1900 Ma, major magmatism at 500–550 Ma and early Jurassic lithospheric extension or inversion; and (7) show that the Indian plate rocks were metamorphosed shortly after the collision within Kohistan, which occurred at circa 50 Ma, and subsequently cooled back through 500°C at circa 38 Ma and 300°C at 30–35 Ma with ages of cooling through 200° and 100°C (as determined by fission track data) locally controlled by Nanga Parbat related uplift tectonics.

Geological and geochemical evidence suggest that the Oman ophiolite is a fragment of a submarine arc-basin complex formed above a short-lived subduction zone in the mid-Cretaceous. Detailed studies of the lava stratigraphy and the intrusive relationships of dykes, sills and high-level plutons provide further evidence for the magmatic and tectonic development of the complex in question. Four consecutive events can be recognized to have taken place before emplacement: (1) eruption of basalts of island arc affinity onto pre-existing (Triassic) oceanic crust; (2) creation of new oceanic crust by backarc spreading; (3) intrusion of magma into this back-arc oceanic crust accompanied by eruption of basalts and andesites from discrete volcanic centres; (4) further intrusion of magma accompanied by uplift and eruption of basalts and rhyolites in submarine graben. A combined structural and geochemical analysis of the dyke swarm indicates that extension took place in approximately a N-S (ridge) and an ESE-WNW (leaky transform) direction relative to an inferred direction of subduction to the NE, and that a small but significant proportion of the sheeted dykes were injected during the ‘arc’ rather than the earlier ‘back-arc spreading’ episode. These various observations can be explained in terms of the progressive response of a non-isotropic lithosphere to the stresses induced during subduction.

Recent suggestions that the Greater Himalayan Sequence (GHS) represents a mid-crustal channel of low viscosity, partially molten Indian plate crust extruding southward between two major ductile shear zones, the Main Central thrust (MCT) below, and the South Tibetan detachment (STD) normal fault above, are examined, with particular reference to the Everest transect across Nepal-south Tibet. The catalyst for the early kyanite _ sillimanite metamorphism (650-680~ 7-8 kbar, 32-30 Ma) was crustal thickening and regional Barrovian metamorphism. Later sillimanite + cordierite metamorphism (600-680~ 4-5 kbar, 23-17 Ma) is attributed to increased heat input and partial melting of the crust. Crustal melting occurred at relatively shallow depths (15-19 km, 4-5 kbar) in the crust. The presence of highly radiogenic Proterozoic black shales (Haimanta-Cheka Groups) at this unique stratigraphic horizon promoted melting due to the high concentration of heat-producing elements, particularly U-bearing minerals. It is suggested that crustal melting triggered channel flow and ductile extrusion of the GHS, and that when the leucogranites cooled rapidly at 17-16 Ma the flow ended, as deformation propagated southward into the Lesser Himalaya. Kinematic indicators record a dominant southvergent simple shear component across the Greater Himalaya. An important component of pure shear is also recorded in flattening and boudinage fabrics within the STD zone, and compressed metamorphic isograds along both the STD and MCT shear zones. These kinematic factors suggest that the ductile GHS channel was subjected to subvertical thinning during southward extrusion. However, dating of the shear zones along the top and base of the channel shows that the deformation propagated outward with time over the period 20-16 Ma, expanding the extruding channel. The last brittle faulting episode occurred along the southern (structurally lower) limits of the MCT shear zone and the northem (structurally higher) limits of the STD normal fault zone. Late-stage breakback thrusting occurred along the MCT and at the back of the orogenic wedge in the Tethyan zone. Our model shows that the Himalayan-south Tibetan crust is rheologically layered, and has several major low-angle detachments that separate layers of crust and upper mantle, each deforming in different ways, at different times.The Tibetan plateau (Fig. 1), covering an area of >5 • 106 km, is an arid plateau with low relief and low erosion rates, and forms the largest area of high elevation (average elevation of 5023 m) and thick crust (65-80 km) on the planet (Fielding

The Greater Himalayan Slab (GHS) is composed of a north-dipping anatectic core, bounded above by the South Tibetan detachment system (STDS) and below by the Main Central thrust zone (MCTZ). Assuming simultaneous movement on the MCTZ and STDS, the GHS can be modelled as a southward-extruding wedge or channel. New insights into extrusion-related flow within the GHS emerge from detailed kinematic and vorticity analyses in the Everest region. At the highest structural levels, mean kinematic vorticity number (Wm) estimates of 0.74–0.91 (c. 45–287fb3e69cure shear) were obtained from sheared Tethyan limestone and marble from the Yellow Band on Mount Everest. Underlying amphibolite-facies schists and gneisses, exposed in Rongbuk valley, yield Wm estimates of 0.57–0.85 (c. 62–357fb3e69cure shear) and associated microstructures indicate that flow occurred at close to peak metamorphic conditions. Vorticity analysis becomes progressively more problematic as deformation temperatures increase towards the anatectic core. Within the MCTZ, rigid elongate garnet grains yield Wm estimates of 0.63–0.77 (c. 58–447fb3e69cure shear). We attribute flow partitioning in the GHS to spatial and temporal variations that resulted in the juxtaposition of amphibolite-facies rocks, which record early stages of extrusion, with greenschist to unmetamorphosed samples that record later stages of exhumation.