Crustal thickening, Barrovian metamorphism, and exhumation of midcrustal rocks during doming and extrusion: Insights from the Himalaya, NW India

M. J. Jessup; J. M. Langille; J. M. Cottle; T. Ahmad

doi:10.1002/2015tc003962

Crustal melt granites and migmatites along the Himalaya: melt source, segregation, transport and granite emplacement mechanisms

Earth and Environmental Science Transactions of the Royal Society of Edinburgh ◽

10.1017/s175569100901617x ◽

2009 ◽

Vol 100 (1-2) ◽

pp. 219-233 ◽

Cited By ~ 60

Author(s):

M. P. Searle ◽

J. M. Cottle ◽

M. J. Streule ◽

D. J. Waters

Keyword(s):

Partial Melting ◽

Shear Zone ◽

Internal Heat ◽

Shear Zones ◽

Source Rocks ◽

Crustal Thickening ◽

Main Central Thrust ◽

Crustal Layer ◽

Middle Crust ◽

The Himalaya

ABSTRACTIndia–Asia collision resulted in crustal thickening and shortening, metamorphism and partial melting along the 2200 km-long Himalayan range. In the core of the Greater Himalaya, widespread in situ partial melting in sillimanite+K-feldspar gneisses resulted in formation of migmatites and Ms+Bt+Grt+Tur±Crd±Sil leucogranites, mainly by muscovite dehydration melting. Melting occurred at shallow depths (4–6 kbar; 15–20 km depth) in the middle crust, but not in the lower crust. 87Sr/86Sr ratios of leucogranites are very high (0·74–0·79) and heterogeneous, indicating a 100 crustal protolith. Melts were sourced from fertile muscovite-bearing pelites and quartzo-feldspathic gneisses of the Neo-Proterozoic Haimanta–Cheka Formations. Melting was induced through a combination of thermal relaxation due to crustal thickening and from high internal heat production rates within the Proterozoic source rocks in the middle crust. Himalayan granites have highly radiogenic Pb isotopes and extremely high uranium concentrations. Little or no heat was derived either from the mantle or from shear heating along thrust faults. Mid-crustal melting triggered southward ductile extrusion (channel flow) of a mid-crustal layer bounded by a crustal-scale thrust fault and shear zone (Main Central Thrust; MCT) along the base, and a low-angle ductile shear zone and normal fault (South Tibetan Detachment; STD) along the top. Multi-system thermochronology (U–Pb, Sm–Nd, 40Ar–39Ar and fission track dating) show that partial melting spanned ̃24–15 Ma and triggered mid-crustal flow between the simultaneously active shear zones of the MCT and STD. Granite melting was restricted in both time (Early Miocene) and space (middle crust) along the entire length of the Himalaya. Melts were channelled up via hydraulic fracturing into sheeted sill complexes from the underthrust Indian plate source beneath southern Tibet, and intruded for up to 100 km parallel to the foliation in the host sillimanite gneisses. Crystallisation of the leucogranites was immediately followed by rapid exhumation, cooling and enhanced erosion during the Early–Middle Miocene.

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Crustal Thickening and Rise of the Himalaya: A Metamorphic Perspective

10.46427/gold2020.2728 ◽

2020 ◽

Author(s):

Jia-Min Wang ◽

Gautam Khanal

Keyword(s):

Crustal Thickening ◽

The Himalaya

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Quantifying displacement on the South Tibetan Detachment normal fault, Everest massif, and the timing of crustal thickening and uplift in the Himalaya and South Tibet

Journal of Nepal Geological Society ◽

10.3126/jngs.v26i0.32071 ◽

2002 ◽

Vol 26 ◽

Author(s):

M. P. Searle ◽

R. L. Simpson ◽

R. D. Law ◽

D. J. Waters ◽

R. R. Parrish

Keyword(s):

Large Scale ◽

Regional Metamorphism ◽

Normal Fault ◽

Crustal Thickening ◽

The Tibetan Plateau ◽

The South ◽

Main Central Thrust ◽

Ductile Shearing ◽

The Himalaya ◽

South Tibet

ABSTRACT Lithospheric convergence of India and Asia since collision has resulted in horizontal shortening, crustal thickening and regional metamorphism in the Himalaya and beneath southern Tibet. The boundary between the High Himalaya and the Tibetan plateau is a large scale, north-dipping, low-angle normal fault termed the South Tibetan Detachment (STD) which was active contemporaneously with the Main Central Thrust (MCT) bounding the southern margin of the High Himalaya. Previous studies have estimated minimum northward displacement along the STD of 35 km along the Everest profile. Here, we demonstrate approximately 200 km of southward displacement of footwall sillimanite + cordierite gneisses (minimum 90-108 km), formed at 600-630°C and pressures of 4.0-4.9 kbar ( 14-18 km depth), beneath the STD which acted as a passive roof fault during southward flow of the hot, viscous, ductile middle crust. U-Th-Pb dating of gneisses, sheared and cross-cutting leucogranites indicates that ductile shearing was active at 17-16 Ma, and later brittle motion at <16 Ma cuts all rocks in the footwall. High temperatures (>620°C) were maintained for -14 Ma along the top of the High Himalayan slab from 32-18 Ma, implying active crustal thickening and high topography in south Tibet during this time. The ending of metamorphism and melting in the Himalaya and ductile shearing along the STD coincides with the initiation of strike-slip faulting in SW Tibet and E-W extension in south Tibet.

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Crustal thickening prior to 43 Ma in the Himalaya: Evidence from lower crust‐derived adakitic magmatism in Dala, eastern Tethyan Himalaya, Tibet

Geological Journal ◽

10.1002/gj.3639 ◽

2019 ◽

Vol 55 (5) ◽

pp. 4021-4046 ◽

Cited By ~ 2

Author(s):

Zuowen Dai ◽

Lei Dong ◽

Guangming Li ◽

Jan Marten Huizenga ◽

Jun Ding ◽

...

Keyword(s):

Lower Crust ◽

Crustal Thickening ◽

The Himalaya ◽

Tethyan Himalaya

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Gneiss Dome Formation in the Himalaya and southern Tibet

Geological Society London Special Publications ◽

10.1144/sp483.15 ◽

2019 ◽

Vol 483 (1) ◽

pp. 401-422 ◽

Cited By ~ 5

Author(s):

Micah J. Jessup ◽

Jackie M. Langille ◽

Timothy F. Diedesch ◽

John M. Cottle

Keyword(s):

Tibetan Plateau ◽

Late Miocene ◽

Shear Zones ◽

Crustal Thickening ◽

Southern Tibet ◽

Gneiss Domes ◽

Time Deformation ◽

Temperature Time ◽

The Himalaya ◽

Parallel Extension

AbstractGneiss domes in the Himalaya and southern Tibet record processes of crustal thickening, metamorphism, melting, deformation and exhumation during the convergence between the Indian and Eurasian plates. We review two types of gneiss domes: North Himalayan gneiss domes (NHGD) and later domes formed by orogen-parallel extension. Located in the southern Tibetan Plateau, the NHGD are cored by granite and gneiss, and mantled by the Tethyan sedimentary sequence. The footwall of these were extruded southwards from beneath the Tibetan Plateau and subsequently warped into a domal shape. The second class of domes were formed during displacement on normal-sense shear zones and detachments that accommodated orogen-parallel extension during the Late Miocene. In some cases, formation of these domes involved an early stage of southwards-directed extrusion prior to doming. We review evidence for orogen-parallel extension to provide context for the formation of these gneiss domes. Compilations of pressure–temperature–time–deformation data and temperature–time paths indicate differences between dome types, and we accordingly propose new terminology. Type 1 domes are characterized by doming as an artefact of post-high-temperature exhumation processes in the Middle Miocene. Type 2 domes formed in response to exhumation during orogen-parallel extension in the Late Miocene that potentially post-dates south-directed extrusion.

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