Cooling, exhumation, and kinematics of the Kanchenjunga Himal, far east Nepal

Larson, Kyle P.; Camacho, Alfredo; Cottle, John M.; Coutand, Isabelle; Buckingham, Heather Marie; Ambrose, Tyler; Man, Santa

doi:10.1002/2017tc004496

Cited by 20 publications

(23 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although we make comments regarding the implications of the results to the overall tectonic evolution of the Himalayas, the lateral heterogeneity of the P‐T conditions across the strike of the MCT in our samples suggests that a degree of caution should be undertaken to generalize the results of the findings (see also Landry et al, ). Others have suggested MCT activity at a time in the range of our proposed tectonic pause (e.g., Kohn et al, , ; Larson et al, ; Tobgay et al, ), whereas in some locations evidence for post‐early Miocene monazite crystallization within the MCT inverted metamorphic sequence is missing (i.e., Arunachal Pradesh, NE India; Clarke et al, ). Some locations record Oligocene tectonic activity along the MCT, ~10 m.y.…”

Section: Discussionmentioning

confidence: 61%

Modeling High‐Resolution Pressure‐Temperature Paths Across the Himalayan Main Central Thrust (Central Nepal): Implications for the Dynamics of Collision

et al. 2018

View full text Add to dashboard Cite

High-resolution, garnet-based pressure-temperature (P-T) paths were obtained for nine rocks across the Himalayan Main Central Thrust (MCT) (Marsyangdi River transect, central Nepal). Paths were created using garnet and whole rock compositions as input parameters into a semiautomated Gibbs free-energy-minimization technique. The conditions recorded by the paths, in general, yield similar T but lower P compared to estimates from mineral equilibria and quartz-in-garnet Raman barometry. The paths are used to modify a model based on a two-dimensional finite difference solution to the diffusion-advection equation. In this model, P-T paths recorded by the footwall garnets result from fault motion at specified times, thermal advection, and alteration of topography. The best fit between the high-resolution P-T paths and model predictions is that from 25 to 18 Ma, samples within the MCT footwall moved at 5 km/Ma, while those in the hanging wall moved at 10 km/Ma. Under these conditions, topography grew to 3.5 km. A pause in activity along the MCT between 18 and 15 Ma allows heat to advect and may be due to a transfer of tectonic activity to the structures closer to the Indian subcontinent. During this time, the topography erodes at a rate of 1.5 km/Ma. Thrusting within the MCT footwall reactivates between 8 and 2 Ma with exhumation rates up to 12 mm/yr since the Pliocene. The results suggest the potential for the highestresolution garnet-based P-T paths to record both the thermobarometric consequences of fault motion and large-scale erosion.Plain Language Summary The Main Central Thrust (MCT) is a major Himalayan fault system largely responsible for the generation of its high topography. Garnets across the MCT record their growth history in the crust through changes in their chemistry. These chemical changes can be extracted and modeled. Here we report detailed pressure-temperature paths recorded by garnets collected across the MCT along the Marsyangdi River in central Nepal. The paths track evolving conditions in the Earth's crust when the MCT was active during the growth of the Himalayas. The results suggest that the MCT formed as individual rock packages moved at distinct times. Further modeling makes predictions about how the Himalayas developed, including that the MCT may have ceased motion 18-15 million years ago, as other faults closer to the Indian subcontinent became active, and that it reactivated 8-2 million years ago, leading to the generation of high topography. The modeling also suggests that very high erosion rates occurred within the range after reactivation. Although garnets have long been used to understand how fault systems evolve, we provide details of an approach that allows higher-resolution data to be extracted from them and show how they could be used to track large-scale erosion.

show abstract

Section: Discussionmentioning

confidence: 61%

Modeling High‐Resolution Pressure‐Temperature Paths Across the Himalayan Main Central Thrust (Central Nepal): Implications for the Dynamics of Collision

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The south to north younging is interpreted to record the progressive cooling of the GHS from the foreland to the hinterland and is compatible with the southward extrusion of partially molten middle crust (e.g., Antolín et al, ; Searle et al, ). Young white mica cooling ages on the north flank of the Karnali klippe and in the hinterland may also reflect the geometry of the MHT and enhanced erosion above the underlying LHS duplex during basal accretion (e.g., Herman et al, ; Larson et al, ; van der Beek et al, ). However, this second hypothesis is less likely because duplexing in the LHS is interpreted to have occurred in the late Miocene (Robinson et al, ), that is, after the GHS cooled below the isotopic closure temperature of white mica.…”

Section: Discussionmentioning

confidence: 99%

Preservation of the Early Evolution of the Himalayan Middle Crust in Foreland Klippen: Insights from the Karnali Klippe, West Nepal

2018

Self Cite

View full text Add to dashboard Cite

Although the India‐Asia collision has been ongoing since the Eocene, the exposed hinterland of the Himalayan orogen was pervasively deformed and metamorphosed at high temperature during the Miocene and hence reveals little information about the Eocene‐Oligocene period of collision. New pressure‐temperature‐time‐deformation data from the Karnali klippe in west Nepal foreland demonstrate that Greater Himalayan sequence (GHS) rocks there escaped the Miocene overprint and consequently unveil the early tectonometamorphic evolution of the middle crust. Prograde metamorphism in the GHS occurred at 40 Ma and peak suprasolidus conditions in the kyanite stability field (i.e., >650–700°C and >0.7–1.0 GPa) were attained between 35 and 30 Ma. Peak metamorphism was followed by cooling, decompression, and melt crystallization at circa 30 Ma during tectonic exhumation below the South Tibetan detachment. As the middle crust was exhumed, strain propagated up section within the South Tibetan detachment high‐strain zone, which remained active through circa 16 Ma. The GHS cooled below ~450–475°C at 20–17 Ma on the southwest flank and 17–14 Ma on the northeast flank of the Karnali klippe. In marked contrast, GHS rocks now exposed in the hinterland were still buried, hot and actively deforming, while the foreland was cooled and exhumed. Oligocene cooling of the frontal tip of the GHS is compatible with the southward extrusion of partially molten midcrustal rocks followed by renewed shortening along out‐of‐sequence shear zones in the hinterland.

show abstract

“…Nepal, Sikkim and Bhutan) in the last 20 years we can observe a clear evolution from the classical geological maps, mainly based on field work, toward a new generation of geological maps based on integrated field work, remote sensing, meso-and micro-structural analysis, petrology and in situ geochronology. This approach led to the mapping of "hidden or cryptic discontinuities" in the metamorphic core of the belt (Carosi et al, 2010(Carosi et al, , 2016Montomoli et al, 2013Montomoli et al, , 2015Cottle et al, 2015;Iaccarino et al 2015Iaccarino et al , 2017aWang et al, 2015Wang et al, , 2016Larson et al 2017 with references) which had primary consequences on the tectonic and metamorphic evolution of the belt and could be used as guidelines for mapping similar discontinuities in other modern and ancient orogenic belts. The "hidden discontinuities" are both in-sequence-thrust sense shear zones or thrusts (Carosi et al, 2016 with references) acting after the collision between India and Asia and out-of-sequencethrusts (Ambrose et al, 2015;Mukherjiee, 2015) affecting the Greater Himalayan Sequence after the activity of the Main Central Thrust.…”

Section: Introductionmentioning

confidence: 99%

20 years of geological mapping of the metamorphic core across Central and Eastern Himalayas

Carosi

Montomoli

Iaccarino

2018

Earth-Science Reviews

107

View full text Add to dashboard Cite

The largest crystalline unit representing the mid-crust in the Himalayan belt is the Greater Himalayan Sequence (GHS) which stretches all over the 2400 km of length of the belt. The GHS, recognised since the first geological explorations of the Himalayas, has been considered for a long time as a coherent tectonic unit, exhumed by the contemporaneous shearing along the Main Central Thrust and the South Tibetan Detachment System in the time span ~ 25-17 Ma. A multidisciplinary approach, integrating geological mapping, structural analysis, petrology and geochronology allowed to better constraints on its internal architecture characterised by several levels of tectonic-metamorphic discontinuities on the regional scale with a top-to-the-S/SW sense of shear and active since ~ 40 Ma. The GHS is consequently divided in three main tectonic units exhumed progressively from the upper part to the lower one by ductile shear zones, later involving the Lesser Himalayan Sequence. Above the Main Central Thrust a cryptic tectono-metamorphic discontinuity (Higher Himalayan Discontinuity; HHD) has been recognized and mapped in Central-Eastern Himalaya. The mapping of the HHD has been allowed by the use of a multidisciplinary approach involving structural analysis, geochronology and petrography. A new map of Western Nepal is presented. In this framework the popular models of exhumation of the GHS mainly based on the contemporaneous activity of the two bounding shear zones (Main Central Thrust and the South Tibetan Detachment) and considering the GHS as a coherent tectonic unit, should be reconsidered. An in-sequence shearing tectonic model, from the deeper to the upper structural levels, further affected by out-of-sequence-thrusts, is more appropriate to explain the deformation, metamorphism and exhumation of the mid-crust in the Himalayan belt. Geological mapping of the Himalayan belt is very far away to be exhaustively completed. Anyway during the last 20, and particularly during the last few years, it has been notably improved due to a new multidisciplinary approach.

show abstract

Cooling, exhumation, and kinematics of the Kanchenjunga Himal, far east Nepal

Cited by 20 publications

References 49 publications

Modeling High‐Resolution Pressure‐Temperature Paths Across the Himalayan Main Central Thrust (Central Nepal): Implications for the Dynamics of Collision

Modeling High‐Resolution Pressure‐Temperature Paths Across the Himalayan Main Central Thrust (Central Nepal): Implications for the Dynamics of Collision

Preservation of the Early Evolution of the Himalayan Middle Crust in Foreland Klippen: Insights from the Karnali Klippe, West Nepal

20 years of geological mapping of the metamorphic core across Central and Eastern Himalayas

Contact Info

Product

Resources

About