Geological signatures of slab shear-off during ongoing India-Asia convergence

2021 ◽  
Author(s):  
Abdul Qayyum ◽  
Nalan Lom ◽  
Eldert L Advokaat ◽  
Wim Spakman ◽  
Douwe J.J van Hinsbergen
Keyword(s):  
Numerical Models ◽  
Leading Edge ◽  
Plate Motion ◽  
Indian Plate ◽  
Mantle Structure ◽  
Continental Lithosphere ◽  
Common View ◽  
Plate Convergence ◽  
Collision Zone ◽  
The Himalaya

<p>Much of our understanding of the dynamics of slab break-off and its geological signatures rely on numerical models with a simplified set-up, in which slab break-off follows arrival of a continent in a mantle-stationary trench, the subsequent arrest of plate convergence, and after a delay time of 10 Ma or more, slab break off under the influence of slab pull. However, geological reconstructions show that plate tectonic reality deviates from this setup: post-collisional convergence is common, trenches are generally not stationary relative to mantle, neither before nor after collision, and there are many examples in which the mantle structure below collision zones is characterized by more, or fewer slabs than collisions.</p><p>A key example of the former is the India-Asia collision zone, where the mantle below India hosts two major, despite the common view of a single collision. Kinematic reconstructions reveal that post-collisional convergence amounted 1000s of kms, and was associated with ~1000 km of trench/collision zone advance. Collision between India-Asia collision zone may provide a good case study to determine the result of post-collisional convergence and absolute lower and upper plate motion on mantle structure, and to evaluate to what extent commonly assumed diagnostic geological phenomena of slab break-off apply.</p><p>In addition to the previously identified major India, Himalaya, and Burma slabs, we here map smaller slabs below Afghanistan and the Himalaya that reveal the latest phases of break-off. We show that west-dipping and east-dipping slabs west and east of India, respectively, are dragged northward parallel to the slab, slabs subducting north of India are overturned, and that the shallowest slab fragments are found in the location where the horizontally underthrust Indian lithosphere below Tibet is narrowest. Our results confirm that northward Indian absolute plate motion continued during two episodes of break-off of large (>1000 km wide) slabs, and decoupling of several smaller fragments. These slabs are currently found south of the present day trench locations. The slabs are located even farther south (>1000 km) of the leading edge of the Indian continental lithosphere, currently underthrust below Tibet, from which the slabs detached, signalling ongoing absolute Indian plate motion. We conclude that the multiple slab break-off events in this setting of ongoing plate convergence and trench advance is better explained by shearing off of slabs from the downgoing plate, possibly at a depth corresponding to the base of the Indian continental lithosphere, are not (necessarily) related to the timing of collision. A recently proposed, detailed diachronous record of deformation, uplift, and oroclinal bending in the Himalaya that was liked to slab break-off fits well with our kinematically reconstructed timing of the last slab shear-off, and may provide an important reference geological record for this process. We find that the commonly applied conceptual geological signatures of slab break-off do not apply to the India-Asia collision zone, or to similar settings and histories such as the Arabia-Eurasia collision zone. Our study provides more realistic boundary conditions for future numerical models that aim to assess the dynamics of subduction termination and its geological signatures.</p>

Towards resolving the metamorphic enigma of the Indian Plate in the NW Himalaya of Pakistan

2019 ◽  
Vol 483 (1) ◽  
pp. 255-279 ◽  
Author(s):  
Peter J. Treloar ◽  
Richard M. Palin ◽  
Michael P. Searle
Keyword(s):  
Leading Edge ◽  
Shear Zones ◽  
Indian Plate ◽  
Main Central Thrust ◽  
Nw Himalaya ◽  
Basement Rocks ◽  
Upper Paleozoic ◽  
The Himalaya ◽  
Temperature Path ◽  
Tethyan Himalaya

AbstractThe 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.

Surface processes control on orogenic evolution: inferences from 3D coupled numerical models and observations from the India-Eurasia collision zone

2021 ◽  
Author(s):  
Luuk van Agtmaal ◽  
Attila Balazs ◽  
Dave May ◽  
Taras Gerya
Keyword(s):  
Numerical Models ◽  
Surface Processes ◽  
Climatic Forcing ◽  
Plate Convergence ◽  
Thermal Fields ◽  
Denudation Rates ◽  
Collision Zone ◽  
Sediment Transportation ◽  
Modelling Techniques ◽  
Evolution Modeling

<p>The inherent links between tectonics, surface processes and climatic variations have long since been recognised as the main drivers for the evolution of orogens. Oceanic and continental subduction and collision processes lead to distinct topographic signals. Simultaneously, different climatic forcing factors and denudation rates substantially modify the style of deformation leading to different stress and thermal fields, strain localisation and even deep mantle evolution. An ideal area where the above-mentioned processes and their connections can be studied is the India-Eurasia collision zone.</p><p>Understanding the complex interplay between tectonics, erosion, sediment transportation and deposition requires the coupled application of thermo-mechanical and surface processes modelling techniques. To this aim, we used a 3D coupled numerical modelling approach. The influence of different plate convergence, erosion and sedimentation rates has been tested by the thermo-mechanical code I3ELVIS (Gerya and Yuen, 2007) coupled to the diffusion-advection based (FDSPM) surface processes model.</p><p>We show preliminary results to demonstrate  that the diffusion-advection erosion implementation has significant effects on local and regional mass redistribution and topographic evolution within narrow, curved, high orogens such as the Himalayas and their syntaxes, where erosion is a dominant forcing factor. We also discuss possible implications from different erosion/sedimentation implementations such as DAC (Ueda et al., 2015; Goren et al., 2014) in combination with the reference thermo-mechanical model to analyse changes in orogenic development as a consequence of different erosional processes in more detail.</p><p>References:</p><p>Gerya, T. V., & Yuen, D. A. (2007). Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Physics of the Earth and Planetary Interiors, 163(1-4), 83-105. <br>Ueda, K., Willett, S. D., Gerya, T., & Ruh, J. (2015). Geomorphological–thermo-mechanical modeling: Application to orogenic wedge dynamics. Tectonophysics, 659, 12-30.<br>Goren, L., Willett, S. D., Herman, F., & Braun, J. (2014). Coupled numerical–analytical approach to landscape evolution modeling. Earth Surface Processes and Landforms, 39(4), 522-545.</p>

What is driving India-Asia convergence?

2021 ◽  
Author(s):  
Santanu Bose ◽  
Wouter P Schellart ◽  
Vincent Strak ◽  
João C. Duarte ◽  
Zhihao Chen
Keyword(s):  
Subduction Zones ◽  
Boundary Migration ◽  
Physical Models ◽  
Plate Motion ◽  
Indian Plate ◽  
Mountain Range ◽  
Complete Disappearance ◽  
The Tibetan Plateau ◽  
Main Driver ◽  
The Himalaya

<p>The Himalaya and the Tibetan plateau, the highest mountain range on Earth, have been growing continuously for the last 55 Myrs since India collided with Eurasia. The forces driving this protracted mountain building process are still not fully understood, and continue to puzzle Earth Scientists. Although it is now well accepted that subduction zones are the main driver for plate motion, plate boundary migration, and mantle flow in the asthenosphere, their role in driving Indian indentation into the Asian landmass has never been tested with geodynamic models. This study uses four-dimensional geodynamic physical models to test the role of lateral subduction zones in driving the India-Asia collision. The objective of our study is to investigate if the slab pull force of the Sunda and Makran slabs have any role to play in the dynamics of the ongoing India-Asia convergence, particularly after the complete disappearance of the Tethyan slab, which was primarily steering the northward travel of the Indian plate since late Jurassic. To address this issue, we performed three experiments by varying the size and configuration of the subducting plate in the initial model setup.  Our experimental results show that active subduction of the Indo-Australian plate along the Sunda subduction zone is the main driver of the India-Asia convergence, Indian indentation, the growth of the Himalaya-Tibet mountains, and the eastward extrusion of southeast Asia. Our work further suggests that the protracted growth of collisional mountains on Earth requires nearby active subduction zones and, therefore, Himalayan-type orogens may have been rare in the Earth’s history.</p>

scholarly journals The convergence history of India-Eurasia records multiple subduction dynamics processes

2020 ◽  
Vol 6 (19) ◽  
pp. eaaz8681 ◽  
Author(s):  
Adina E. Pusok ◽  
Dave R. Stegman
Keyword(s):  
Indian Ocean ◽  
Numerical Models ◽  
Plate Motion ◽  
Indian Plate ◽  
Geological Evidence ◽  
Sequence Of Events ◽  
History Of ◽  
The Indian Ocean ◽  
Fast Motion ◽  
Subduction System

During the Cretaceous, the Indian plate moved towards Eurasia at the fastest rates ever recorded. The details of this journey are preserved in the Indian Ocean seafloor, which document two distinct pulses of fast motion, separated by a noticeable slowdown. The nature of this rapid acceleration, followed by a rapid slowdown and then succeeded by a second speedup, is puzzling to explain. Using an extensive observation dataset and numerical models of subduction, we show that the arrival of the Reunion mantle plume started a sequence of events that can explain this history of plate motion. The forces applied by the plume initiate an intra-oceanic subduction zone, which eventually adds enough additional force to drive the plates at the anomalously fast speeds. The two-stage closure of a double subduction system, including accretion of an island arc at 50 million years ago, may help reconcile geological evidence for a protracted India-Eurasia collision.

Delineation of lithosphere structure and characterization of the Moho geometry under the Himalaya–Karakoram–Tibet collision zone using surface-wave tomography

2019 ◽  
Vol 481 (1) ◽  
pp. 19-40 ◽  
Author(s):  
Naresh Kumar ◽  
A. Aoudia ◽  
M. Guidarelli ◽  
Vivek G. Babu ◽  
Devajit Hazarika ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Indian Plate ◽  
Moho Depth ◽  
S Wave ◽  
Low Velocity ◽  
Period Range ◽  
Velocity Models ◽  
Collision Zone ◽  
The Himalaya ◽  
Group Velocities

AbstractGroup velocities for a period range of 6–60 s for the fundamental mode of the Rayleigh wave passing across the Himalaya–Karakoram–Tibet orogen are used to delineate the structure of the upper lithosphere using the data from 35 broadband seismic stations. 2D tomography velocity maps of group velocities were obtained at grids of 1° separation. Redefined local dispersion curves are inverted non-linearly to obtain 1D velocity models and to construct a 3D image of the S-wave structure down to a depth of 90 km.The Moho discontinuity is correlated with c. 4.0 km s−1 S-wave velocity. The results depict a NE-dipping trend of the Moho depth from c. 40 km beneath the frontal part of the Himalaya to up to c. 70–80 km beneath the collision zone before shallowing substantially to c. 40 km beneath the Tarim Basin. The study also reveals thick deposits of sediments in the Indo-Gangetic plains and the Tarim Basin. A broad low-velocity zone at mid-crustal depth in the western Tibetan Plateau, the Karakoram region and the surface-collision part of the India–Eurasia tectonic plates is interpreted as the effect of partial melting and/or the presence of aqueous fluid. The high velocities in the southern deeper part indicate that the lower crust and uppermost mantle of the Indian Plate are dense and cold.

Reconciling plate convergence and orogeny: The influence of India-Asia convergence rate on the formation of the Himalayas

2020 ◽  
Author(s):  
Ben S. Knight ◽  
Fabio A. Capitanio ◽  
Roberto F. Weinberg
Keyword(s):  
Tibetan Plateau ◽  
Numerical Models ◽  
The Tibetan Plateau ◽  
Thrust Belt ◽  
Plate Convergence ◽  
Structural Style ◽  
Fold And Thrust Belt ◽  
Velocity History ◽  
The Himalaya

<p>The collision of India and Eurasia since ~50 Ma has resulted in a broad range of deformation along the Himalaya-Tibetan orogeny, accommodating >2700 km of convergence. The region is characterised by the Tibetan Plateau, the Himalayan internal units and fold-and-thrust belt from North to South. These formed as a consequence of a convergence history characterised by a progressive decrease in velocity, from ~10 cm/yr 50 Ma, to ~8 cm/yr 42.5 Ma and to present-day values of ~4 cm/yr around 20 Ma. Here, we test the controls of such a convergence velocity history on the orogeny of a viscoplastic wedge during collision, above a subducting continental lithosphere. We compare numerical models simulating India-Asia plate convergence and collision, comparing the structures observed throughout the evolution with those observed in the Himalayan-Tibetan region. The models display distinct phases of growth and structural style evolution in the Himalayan-Tibetan region that are a result of the change in convergence velocity and long-term collision. After an initial stacking, the high convergence velocity forces deformation migration towards the upper plate, where a plateau forms, while late stage slowdown of collision favours the formation of the Himalayan fold-and-thrust belt. While the latter is in agreement with the structuring of the southermost domains and the South Tibetan Detachment (STD) fault, the former provide constraints to the initial uplift of the Tibetan Plateau.</p>

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