Thrusting, extension, and doming during the polyphase tectonometamorphic evolution of the High Himalayan Crystalline Zone in NW India

Robyr, Martin; Vannay, Jean-Claude; Epard, Jean-Luc; Steck, A.

doi:10.1016/s1367-9120(02)00039-1

Cited by 47 publications

(79 citation statements)

References 31 publications

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“…In the western Himalaya, several studies combining structural mapping with thermobarometry show that metamorphic isograds were folded after peak metamorphism, resulting in a right-way-up metamorphic sequence along the top of the GHS beneath the Zanskar shear zone (ZSZ), and an inverted metamorphic sequence along the MCT zone at the base of the slab (Searle & Rex 1989;Searle et al 1992Searle et al , 1999bWalker et al 1999;Dezes et al 1999;Stephenson et al 2000Stephenson et al , 2001Robyr et al 2002;Vannay et al 2004). Peak sillimanite + K-feldspar-grade metamorphism was concomitant with partial melting at c. 22-20 Ma (Noble & Searle 1995).…”

Section: Himalayan Channel Flow Modelmentioning

confidence: 99%

Crustal structure, restoration and evolution of the Greater Himalaya in Nepal-South Tibet: implications for channel flow and ductile extrusion of the middle crust

2006

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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

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Section: Himalayan Channel Flow Modelmentioning

confidence: 99%

Crustal structure, restoration and evolution of the Greater Himalaya in Nepal-South Tibet: implications for channel flow and ductile extrusion of the middle crust

2006

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“…During this phase, some of the paragneiss were migmatized as a consequence of temperature up to ca. 800°C at depth down to ca.40 km (Dèzes et al 1999, Robyr et al 2002. Geochronological data reveal that this SW-directed phase occurred between Middle Eocene and Late Oligocene (Vance andHarris 1999, Schlup et al 2003).…”

Section: High-grade Metamorphic Rocks Of the High Himalayanmentioning

confidence: 95%

“…This migmatitic core is symmetrically surrounded by rocks of the sillimanite, kyanite ± staurolite, garnet, biotite, and chlorite mineral zones. The structural and metamorphic data from the Miyar-Gianbul Valley section reveal that the tectono-metamorphic evolution of the HHCZ in SE Zanskar is associated with a polyphase tectonic history involving converging nappe structures superimposed by opposite-directed extensional structures (Dèzes et al 1999, Steck et al1999, Robyr et al 2002. The first tectonic event corresponds to an early phase of crustal thickening related to NE-directed movements.…”

Section: High-grade Metamorphic Rocks Of the High Himalayanmentioning

confidence: 95%

“…The first tectonic event corresponds to an early phase of crustal thickening related to NE-directed movements. This phase most likely took place during Early to Middle Eocene, and it led to the creation of Shikar Beh nappe, thrusting toward the NE along the Miyar Thrust and responsible for the prograde metamorphic field gradient in the southern limb of the dome , Robyr et al 2002. Beneath the Miyar Thrust, partial melting, related to this initial phase, occurred at temperatures between 750 and 850°C.…”

Section: High-grade Metamorphic Rocks Of the High Himalayanmentioning

confidence: 99%

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Timing of synconvergent extension in NW Himalaya: New geochronological constraints from the Gianbul dome (SE Zanskar)

Robyr

Mattinson

Hacker

2008

Himalayan Journal of Sciences

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“…85 [26][27][28][29][30]. Climatically, Lahaul is sandwiched between the monsoon dominated areas of the Pir Panjal to the south and the mid-latitude Westerlies dominated arid areas of Ladakh to the north of the Great Himalayan Range.…”

Section: Study Areamentioning

confidence: 99%

Late Holocene Glacier Dynamics in the Miyar Basin, Lahaul Himalaya, India

et al. 2017

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Detailed field mapping of glacial and paraglacial landforms and optical dating from these landforms are used to reconstruct the early Holocene glaciation in the semi-arid region of Miyar basin, Lahaul Himalaya. The study identifies three stages of glaciation, of decreasing magnitude and termed, from oldest to youngest, the Miyar stage (MR-I), Khanjar stage (KH-II), and Menthosa advance (M-III). The oldest glacial stage (MR-I) has been established on the basis of detailed geomorphological evidence such as U-shaped valley morphology, trimlines, and truncated spurs. It is speculated to be older than the global Last Glacial Maximum (gLGM) based on the magnitude of ∆ELA (Equilibrium-Line Altitude, 606m). No evidence of glacier expansion recorded from the basin correlates with the period of the gLGM. The second stage (KH-II) is well represented by extensive depositional features such as lateral and terminal moraines, drumlins, and lacustrine fills that have been constrained within 10 ± 1 to 6.6 ± 1.0 ka (Optically stimulated luminescence-OSL-ages), dating it to the early Holocene advance following the Younger Dryas cooling event. Exceptionally young glacial records of expansion are limited within a few hundred meters of the present termini of tributary glaciers and correlates with the 18th-century cooling event. Records of this glacial advance, termed the Menthosa advance, are clearly noticed in some tributary valleys.

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Thrusting, extension, and doming during the polyphase tectonometamorphic evolution of the High Himalayan Crystalline Zone in NW India

Cited by 47 publications

References 31 publications

Crustal structure, restoration and evolution of the Greater Himalaya in Nepal-South Tibet: implications for channel flow and ductile extrusion of the middle crust

Crustal structure, restoration and evolution of the Greater Himalaya in Nepal-South Tibet: implications for channel flow and ductile extrusion of the middle crust

Timing of synconvergent extension in NW Himalaya: New geochronological constraints from the Gianbul dome (SE Zanskar)

Late Holocene Glacier Dynamics in the Miyar Basin, Lahaul Himalaya, India

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