Southern Tibet Detachment System at Khula Kangri, Eastern Himalaya: A Large‐Area, Shallow Detachment Stretching into Bhutan?

1999 ◽  
Vol 107 (5) ◽  
pp. 623-631 ◽  
Author(s):  
M. A. Edwards ◽  
A. Pêcher ◽  
W. S. F. Kidd ◽  
B. C. Burchfiel ◽  
L. H. Royden
Keyword(s):  
Eastern Himalaya ◽  
Large Area ◽  
Southern Tibet

Leucogranites in Lhozag, southern Tibet: Implications for the tectonic evolution of the eastern Himalaya

Lithos ◽  
2017 ◽  
Vol 294-295 ◽  
pp. 246-262 ◽  
Author(s):  
Chunmei Huang ◽  
Zhidan Zhao ◽  
Guangming Li ◽  
Di-Cheng Zhu ◽  
Dong Liu ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Eastern Himalaya ◽  
Southern Tibet

scholarly journals The Timing of Metamorphism, Magmatism, and Cooling in the Zanskar, Garhwal, and Nepal Himalaya

1995 ◽  
Vol 11 ◽  
Author(s):  
M. P. Searle
Keyword(s):  
Hanging Wall ◽  
Crustal Thickening ◽  
Indian Plate ◽  
Eastern Himalaya ◽  
Normal Faults ◽  
The Tibetan Plateau ◽  
Main Central Thrust ◽  
Southern Tibet ◽  
Peak Metamorphism ◽  
Exhumation Rates

Following India-Asia collision, which is estimated at ca. 54-50 Ma in the Ladakh-southern Tibet area, crustal thickening and timing of peak metamorphism may have been diachronous both along the Himalaya (pre-40 Ma north Pakistan; pre-31 Ma Zanskar; pre-20 Ma east Kashmir, west Garhwal; 11-4 Ma Nanga Parbat) and cross the strike of the High Himalaya, propagating S (in Zanskar SW) with time. Thrusting along the base of the High Himalayan slab (Main Central Thrust active 21-19 Ma) was synchronous with N-S (in Zanskar NE-SW) extension along the top of the slab (South Tibet Detachment Zone). Kyanite and sillimanite gneisses in the footwall formed at pressure of 8-10 kbars and depths of burial of 28-35 km, 30- 21 Ma ago, whereas anchimetamorphic sediments along the hanging wall have never been buried below ca. 5-6 km. Peak temperatures may have reached 750 on the prograde part of the P-T path. Thermobarometers can be used to constrain depths of burial assuming a continental geothermal gradient of 28-30 °C/km and a lithostatic gradient of around 3.5-3.7 km/kbar (or 0.285 kbars/km). Timing of peak metamorphism cannot yet be constrained accurately. However, we can infer cooling histories derived from thermochronometers using radiogenic isotopic systems, and thereby exhumation rates. This paper reviews all the reliable geochronological data and infers cooling histories for the Himalayan zone in Zanskar, Garhwal, and Nepal. Exhumation rates have been far greater in the High Himalayan Zone (1.4-2.1 mm/year) and southern Karakoram (1.2-1.6 mm/year) than along the zone of collision (Indus suture) or along the north Indian plate margin. The High Himalayan leucogranites span 26-14 Ma in the central Himalaya, and anatexis occurred at 21-19 Ma in Zanskar, approximately 30 Ma after the collision. The cooling histories show that significant crustal thickening, widespread metamorphism, erosion and exhumation (and therefore, possibly significant topographic elevation) occurred during the early Miocene along the central and eastern Himalaya, before the strengthening of the Indian monsoon at ca. 8 Ma, before the major change in climate and vegetation, and before the onset of E-W extension on the Tibetan plateau. Exhumation, therefore, was primarily controlled by active thrusts and normal faults, not by external factors such as climate change.

Frequency and lapse time dependent seismic attenuation in eastern Himalaya and southern Tibet

2016 ◽  
Vol 85 (3) ◽  
pp. 1709-1722 ◽  
Author(s):  
Sagar Singh ◽  
Chandrani Singh ◽  
Rahul Biswas ◽  
Arun Singh
Keyword(s):  
Seismic Attenuation ◽  
Time Dependent ◽  
Eastern Himalaya ◽  
Lapse Time ◽  
Southern Tibet

Fractal and b-Value Mapping in Eastern Himalaya and Southern Tibet

2009 ◽  
Vol 99 (6) ◽  
pp. 3529-3533 ◽  
Author(s):  
C. Singh ◽  
A. Singh ◽  
R. K. Chadha
Keyword(s):  
B Value ◽  
Eastern Himalaya ◽  
Southern Tibet

scholarly journals Mio-Pliocene piracy, relict landscape and drainage reorganization in the Namcha Barwa syntaxis zone of eastern Himalaya

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Nilesh Kumar Jaiswara ◽  
Prabha Pandey ◽  
Anand K. Pandey
Keyword(s):  
Drainage Area ◽  
Eastern Himalaya ◽  
Foreland Basins ◽  
Sedimentation Pattern ◽  
Southern Tibet ◽  
Base Level ◽  
Tectonically Active ◽  
Regional Landscape ◽  
Accelerated Growth ◽  
Regional Tectonics

AbstractThe presence of unique elevated low relief relict landscape in the transient Dibang catchment, at the orographic edge of Tibet-Himalaya in the tectonically active Namcha Barwa syntaxial zone, is modelled to understand evolving regional landscape, drainage reorganization and tectonics. This elevated low relief landscape represents a Mio-Pliocene abandoned paleo-channel of the Yarlung river, which was captured by the headward eroding Siang river owing to >600 m base level advantage. The river capture caused isolation of the Dibang river, which evolved as a transient parched catchment since 3–6 Ma after loss of ~17 times drainage area and 4–17 times discharge. The drainage area and discharge gained by the Siang river triggered enormous incision causing aneurysm leading to the accelerated growth of the Tsangpo gorge and affected regional tectonics. This paleo-drainage reorganization is reflected in the Mio-Pliocene sedimentation pattern in the southern Tibet-Himalaya and foreland basins.

Syn-collisional magmatic record of Indian steep subduction by 50 Ma

2020 ◽  
Author(s):  
Yue Qi ◽  
Chris J. Hawkesworth ◽  
Qiang Wang ◽  
Derek A. Wyman ◽  
Zheng-Xiang Li ◽  
...  
Keyword(s):  
High Volume ◽  
Isotope Ratios ◽  
Eastern Himalaya ◽  
Continental Lithosphere ◽  
Southern Tibet ◽  
Geochemical Composition ◽  
Crustal Rocks ◽  
Continental Subduction ◽  
Magmatic Rocks ◽  
Formation And Evolution

Subduction of Indian continental lithosphere during the Asia-India collision played an important role in the formation and evolution of the Himalaya-Tibetan orogen. However, the geometry of early Indian continental subduction remains debated. Given that the Indian continent is characterized by enriched isotope ratios (87Sr/86Sr > 0.730, εNd(t) < −10), relative to those in subducted oceanic materials (87Sr/86Sr < 0.704, εNd(t) ≈ +8), changes in the composition of magmatic rocks with time, in particular their radiogenic isotope ratios, is used to constrain the timing and nature of continental subduction. This study reports the field relations, zircon U-Pb ages and geochemical composition of a syn-collisional batholith that crosscuts the central Indus-Yarlung Zangbu suture in the Saga area of southern Tibet. Zircon U/Pb ages for the batholith mainly range from 50 to 46 Ma. Samples from the Lopu Range batholith have enriched zircon Hf (εHf(t) = −0.4 to −8.6) and whole rock 87Sr/86Sri = 0.7094−0.7121 and εNd(t) = −7.3 to −9.8, suggesting that they were derived from a mixture of juvenile Gangdese and isotopically enriched Indian crustal materials. This result indicates that subduction of Indian crustal rocks occurred before 50 Ma in the central Himalaya. The geochemical composition and distribution of high volume ca. 51 Ma magmatism in the Gangdese belt, combined with thermal models of the subduction zone, suggests a steepening of the subducted Indian continental lithosphere occurred between the onset of India-Asia collision (59 Ma) and 46 Ma in the central-eastern Himalaya.

Palaeoslab and plume signatures in the mantle transition zone beneath Eastern Himalaya and adjoining regions

2020 ◽  
Vol 221 (1) ◽  
pp. 468-477
Author(s):  
Dipankar Saikia ◽  
M Ravi Kumar ◽  
Arun Singh
Keyword(s):  
Transition Zone ◽  
Broad Band ◽  
Receiver Functions ◽  
Eastern Himalaya ◽  
Bengal Basin ◽  
Southern Tibet ◽  
Data Set ◽  
Mantle Transition Zone ◽  
Tomographic Images ◽  
Indian Lithosphere

SUMMARY A comprehensive data set of 73 876 high quality receiver functions computed using waveforms recorded by 327 broad-band seismic stations is used to investigate the mantle transition zone (MTZ) structure beneath the eastern Himalaya, southern Tibet, Assam valley and the previously unexplored Burmese arc and Bengal basin regions. A highly variable and perturbed mantle transition zone, with depressed 410 and 660 km discontinuities, is observed beneath the Bengal basin and to the east of the eastern Himalayan syntaxis. The 410 is elevated by ∼10 km along the Himalayan collision front, while it deviates in the range of ±5 km beneath most parts of Tibet and the Himalayan Foredeep. In northern Tibet and along the Red River Fault, delayed conversions from the 410 reveal a deepening of more than 10 km. The 410 and 660 km discontinuities are uplifted by nearly 10 km beneath the Arunachal Himalaya, due to the presence of a subducting Indian lithosphere, as evident in the regional tomographic images. We observe a thick (>20 km) transition zone beneath the Burmese Arc and close to the Tengchong volcano. An uplifted 410 together with a depressed 660 km discontinuity requires presence of lithospheric slabs within the MTZ. Delayed P-to-s conversions from the 410 and 660 km discontinuities in the proximity of the Jinsha suture zone seem to be consistent with the earlier results that invoke flow of a hot Tibetan asthenosphere into the mantle transition zone, as an explanation. Interestingly, results from the Bengal basin reveal a deepening (∼10 km) of both the 410 and 660 km discontinuities. Similar results from other plume affected regions prompt us to interpret this as a signature of the Kergulean plume.

Timing of slip across the South Tibetan detachment system and Yadong–Gulu graben, Eastern Himalaya

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2019-197
Author(s):  
Hanwen Dong ◽  
Kyle P. Larson ◽  
Dawn A. Kellett ◽  
Zhiqin Xu ◽  
Guangwei Li ◽  
...  
Keyword(s):  
Late Miocene ◽  
Analytical Data ◽  
Eastern Himalaya ◽  
Model Parameters ◽  
The South ◽  
Southern Tibet ◽  
Content Type ◽  
The North ◽  
Extensional Strain ◽  
Supplementary Material

The Yadong–Gulu graben preserves the kinematic and temporal relationships between east–west-directed extension in southern Tibet and north–south extensional strain in the Himalaya. In the Yadong region, distinct outer and inner top-down-to-the-north segments of the South Tibetan detachment system (STDS) are recognized. Herein, we combine high- to medium-T (U–Pb, 40Ar/39Ar) and low-T (apatite fission-track, apatite (U–Th)/He and zircon (U–Th)/He) thermochronometry to investigate the timing of slip across the STDS and Yadong–Gulu structures. These data demonstrate that the cessation of the Yadong shear zone, the structurally outer ductile segment of the STDS, occurred c. 20 Ma and that motion along the inner brittle–ductile Zherger La detachment continued after c. 16.6 Ma, ending by 11 Ma. The cooling history in the immediate STDS footwall is characterized by two main episodes of relatively rapid cooling and exhumation. The first occurred in the middle Miocene (c. 15–11 Ma), and is common along-strike of the innermost STDS footwall, related to cooling of the STDS. The second occurred in the late Miocene–Pliocene (c. 7–3 Ma), and is local to the Yadong–Gulu graben footwall in NW Bhutan, indicating that late Miocene–Pliocene slip along the graben system contributed to exhumation of the STDS east of the graben rift.Supplementary material: Tables of analytical data, dating results, and input data and model parameters of HeFTy are available at https://doi.org/10.6084/m9.figshare.c.5132941

Convergent Beam Electron Diffraction

1978 ◽  
Vol 36 (3) ◽  
pp. 304-315
Author(s):  
G. Lehmpfuhl
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Crystal Surface ◽  
Diffraction Spot ◽  
Crystal Thickness ◽  
Large Area ◽  
Electron Microscopic ◽  
Additional Information ◽  
Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

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