Tectonic implications of Palaeoproterozoic anatexis and Late Miocene metamorphism in the Lesser Himalayan Sequence, Sutlej Valley, NW India

Chambers, Jennifer; Argles, Tom; Horstwood, Matthew; Harris, Nigel; Parrish, Randall R.; Ahmad, Talat

doi:10.1144/0016-76492007/090

Cited by 52 publications

(43 citation statements)

References 59 publications

(90 reference statements)

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“…t = 0. Close arrows represent the pure shear component prevalent during the E 2a -pulse conformity with the disparity in geochemical parameters across the MCT U (their Vaikrita Thrust) as compiled by Chambers et al (2008) and their proposition that across it, the HHSZ was decoupled during extrusion. The absolute timing of the two pulses can be estimated by keeping in mind (1) the ductile extensional shearing in the STDS L and the STDS U cannot form contemporaneously, and (2) Godin et al's (2006) compiled data on timing of the MCT L, the MCT U, the STDS L and the STDS U reframed here as constraint VII in ''Constraints''.…”

Section: Propositionsupporting

confidence: 57%

Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes

Mukherjee

Koyi

2009

Int J Earth Sci (Geol Rundsch)

143

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The Higher Himalayan Shear Zone (HHSZ) in the Sutlej section reveals (1) top-to-SW ductile shearing, (2) top-to-NE ductile shearing in the upper-and the lower strands of the South Tibetan Detachment System (STDS U , STDS L ), and (3) top-to-SW brittle shearing corroborated by trapezoid-shaped minerals in micro-scale. In the proposed extrusion model of the HHSZ, the E 1 -phase during 25-19 Ma is marked by simple shearing of the upper subchannel defined by the upper strand of the Main Central Thrust (MCT U ) and the top of STDS U as the lower-and the upper boundaries, respectively. Subsequently, the E 2a -pulse during 15-14 Ma was characterized by simple shear, pure shear, and channel flow of the entire HHSZ. Finally, the E 2b -pulse during 14-12 Ma observed simple shearing and channel flow of the lower sub-channel defined by the lower strand of the Main Central Thrust (MCT L ) and the top of the STDS L as the lower-and the upper boundaries, respectively. The model explains the constraints of thicknesses of the STDS U and the STDS L along with spatially variable extrusion rate and the inverted metamorphism of the HHSZ. The model predicts (1) shear strain after ductile extrusion to be maximum at the boundaries of the HHSZ, which crudely matches with the existing data. The other speculations that cannot be checked are (2) uniform shear strain from the MCT U to the top of the HHSZ in the E 1 -phase; (3) fastest rates of extrusion of the lower boundaries of the STDS U and the STDS L during the E 2a -and E 2b -pulses, respectively; and (4) variable thickness of the STDS L and rare absence of the STDS U . Non-parabolic shear fabrics of the HHSZ possibly indicate heterogeneous strain. The top-to-SW brittle shearing around 12 Ma augmented the ductile extruded rocks to arrive a shallower depth. The brittle-ductile extension leading to boudinage possibly did not enhance the extrusion.

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Section: Propositionsupporting

confidence: 57%

Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes

Mukherjee

Koyi

2009

Int J Earth Sci (Geol Rundsch)

143

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“…2b of Harris 2006 as deciphered by Grujic et al 1996). (xii) The occurrence of an out-of-sequence thrust (OOST) in the HHSZ (usually south of the STDS L ) in some Himalayan sections (Grujic et al 1996;Hodges et al 1996;Vannay and Hodges 1996;Searle 1999;Jain et al 2000;Grujic et al 2002;Burbank et al 2003;Burbank 2005;Wobus et al 2005;Goscombe et al 2006;Hollister and Grujic 2006;Yin et al 2006;Carosi et al 2007;Harris 2007;Chambers et al 2008;Wobus et al 2008;Mukherjee et al 2009). The next section reviews the OOST within the HHSZ.…”

Section: Discussionmentioning

confidence: 99%

“…However, the footwall contains leucogranites and migmatites, e.g. at Modi Khola , that for the High Himal Thrust (Goscombe et al 2006) and at Sarahan (Chambers et al 2008). The High Himal Thrust dips 20-40°to the E/ENE/NW, and exhibits mylonitization of garnet, sillimanite and feldspar bearing rocks, northward plunging stretching lineations, shear bands, and a very high strain ratio (R) of between 30 and 45 (Goscombe et al 2006).…”

Section: Discussionmentioning

confidence: 99%

“…The STDS U shows dominantly a top-to-NE sense of shearing, whereas it shows a topto-SW shear sense at other locations. Symbols (and references from which ratios were calculated)-MCT L Main Central Thrust-Lower, Ka 1 Kakhtang Thrust (Grujic et al 2002), Ka 2 Kakhtang Thrust (Hollister and Grujic 2006), Ph Physiographic Transition (Harrison et al 1997, Hi High Himal Thrust (HHT), Ch Chaura Thrust (Jain et al 2000, Chambers et al 2008, Kh Khumbu Thrust (Searle 1999); Hi: Higher Himal Thrust (Goscombe et al 2006), Zi Zimithang Thrust , To Toijem Shear Zone (Carosi et al 2007; however, as per Carosi et al 2010, the thrust at Toijem is not an OOST), Kl Kalopani Shear Zone (Vannay and Hodges 1996), Mo Modi Khola Shear Zone . Other symbols defined in caption of experiments with parallel inclined boundaries (experiment numbers 1, 5, 7 to 10 in Table 2; Figs.…”

Section: Model Design and Materialsmentioning

confidence: 99%

“…The 'Greater Himalayan Sequence' of Godin et al (2006) is presented here as the HHSZ, and their MCT-zone as the MCT L . Locations of the OOST were taken from the following references-Chaura/Sarahan: Chambers et al (2008); Toijem : Carosi et al (2007) (However, as per Carosi et al 2011, the thrust at Toijem is not an OOST); Kalopani: Vannay and Hodges (1996); Modi Khola ; Physiographic Transition, PT: Wobus et al (2005); Khumbu: Searle et al (1995); High Himal Thrust (Hi): Goscombe et al (2006); Kakhtang: Hollister and Grujic (2006); and Zimithang: Yin et al (2006) word 'extrusion' is used to denote upward movement of rocks that effectively behaved as fluids (similar to Stüwe 2007).…”

Section: Introductionmentioning

confidence: 99%

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Implications of channel flow analogue models for extrusion of the Higher Himalayan Shear Zone with special reference to the out-of-sequence thrusting

Mukherjee

Koyi

Talbot

2011

Int J Earth Sci (Geol Rundsch)

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The Higher Himalayan Shear Zone (HHSZ) contains a ductile top-to-N/NE shear zone-the South Tibetan detachment system-lower (STDS L ) and an out-ofsequence thrust (OOST) as well as a top-to-N/NE normal shear at its northern boundary and ubiquitously distributed compressional top-to-S/SW shear throughout the shear zone. The OOST that was active between 22 Ma and the Holocene, varies in thickness from 50 m to 6 km and in throw from 1.4 to 20 km. Channel flow analogue models of this structural geology were performed in this work. A Newtonian viscous polymer (PDMS) was pushed through a horizontal channel leading to an inclined channel with parallel and upward-diverging boundaries analogous to the HHSZ and allowed to extrude to the free surface. A top-to-N/NE shear zone equivalent to the STDS U developed spontaneously. This also indirectly connotes an independent flow confined to the southern part of the HHSZ gave rise to the STDS L . The PDMS originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel. The lower boundary of this faster PDMS defined the OOST. The model OOST originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began. The genesis of the OOST seems to be unrelated to any rheologic contrast or climatic effects. Profound variations in the flow parameters along the HHSZ and the extrusive force probably resulted in variations in the timing, location, thickness and slip parameters of the OOST. Variation in pressure gradient within the model horizontal channel, however, could not be matched with the natural prototype. Channel flow alone presumably did not result in southward propagation of deformation in the Himalaya.

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Extrusion vs. duplexing models of Himalayan mountain building 1: Discovery of the Pabbar thrust confirms duplex-dominated growth of the northwestern Indian Himalaya since Mid-Miocene

Webb

2015

Tectonics

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Ongoing Himalayan growth is generally thought to be dominated by duplexing and/or extrusion processes. These models may be tested by reconstructing Himalayan fold-thrust belt growth since the middle Miocene. However, our knowledge of basic structural geometry remains too fragmentary to resolve the issue, even in areas with rich stratigraphic diversity such as the northwestern Indian Himalaya. In this region, a primary outstanding question involves the uncertain relationship of the Berinag thrust and the Tons thrust, structures with displacements of >80 km and >40 km, respectively. The uncertain geometry and kinematics allow for the complete range of duplexing or extrusion processes for the integrated kinematic history since the middle Miocene. To address this issue, field mapping and kinematic analysis were performed to reconstruct the deformation of the Lesser Himalayan Sequence in the northwest Indian Himalaya. Our results reveal a new discovery: a~450 m thick top-to-southwest shear zone, termed the Pabbar thrust. The Pabbar thrust placed the Outer Lesser Himalayan Sequence (the Tons thrust hanging wall) directly on the Berinag Group (the Berinag thrust hanging wall). This discovery requires that the Berinag thrust and Tons thrust are, in fact, the same structure, and discrete duplexing processes dominated growth of the northwest Indian Himalaya for the past 10-15 million years. Along-strike extension of these kinematics and corresponding geometries is consistent with the observed orogenic framework and resolves a stratigraphic continuity problem across the India-west Nepal border, where prior work suggests that structures are continuous but stratigraphy does not match.

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Tectonic implications of Palaeoproterozoic anatexis and Late Miocene metamorphism in the Lesser Himalayan Sequence, Sutlej Valley, NW India

Cited by 52 publications

References 59 publications

Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes

Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes

Implications of channel flow analogue models for extrusion of the Higher Himalayan Shear Zone with special reference to the out-of-sequence thrusting

Extrusion vs. duplexing models of Himalayan mountain building 1: Discovery of the Pabbar thrust confirms duplex-dominated growth of the northwestern Indian Himalaya since Mid-Miocene

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