Was Himalayan normal faulting triggered by initiation of the Ramgarh–Munsiari thrust and development of the Lesser Himalayan duplex?

Robinson, Delores M.; Pearson, Ofori N.

doi:10.1007/s00531-013-0895-3

Cited by 36 publications

(26 citation statements)

References 110 publications

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“…Vaikrita Group rocks yield similar 87 Sr/ 86 Sr values comparable to those from MCT hanging wall rocks elsewhere in the orogen. The high-grade rocks of the Munsiari Group formed from protoliths similar in age to Paleoproterozoic iLH rocks (Mandal et al, 2015(Mandal et al, , 2016Robinson & Pearson, 2013), and thus yield similar isotopic compositions to iLH and LH rocks of Nepal-in fact, Munsiari rocks have yielded some of the highest 87 Sr/ 86 Sr ratios in the Himalayan orogen (e.g., >1.04) (Ahmad et al, 2000;Bickle et al, 2001). In northwest India, crystalline rocks from the Askot klippe are composed of Paleoproterozoic rocks of Munsiari affinity (Mandal et al, 2016), while rocks from the Almora klippe show GH affinity (Mandal et al, 2015).…”

Section: Himalayan Orogenesis and Cenozoic Seawater Chemistrymentioning

confidence: 99%

Zircon (U‐Th)/He Thermochronometric Constraints on Himalayan Thrust Belt Exhumation, Bedrock Weathering, and Cenozoic Seawater Chemistry

Colleps

McKenzie

Stöckli

et al. 2018

Geochem Geophys Geosyst

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Shifts in global seawater 187Os/188Os and 87Sr/86Sr are often utilized as proxies to track global weathering processes responsible for CO2 fluctuations in Earth history, particularly climatic cooling during the Cenozoic. It has been proposed, however, that these isotopic records instead reflect the weathering of chemically distinctive Himalayan lithologies exposed at the surface. We present new zircon (U‐Th)/He thermochronometric and detrital zircon U‐Pb geochronologic evidence from the Himalaya of northwest India to explore these contrasting interpretations concerning the driving mechanisms responsible for these seawater records. Our data demonstrate in‐sequence southward thrust propagation with rapid exhumation of Lesser Himalayan strata enriched in labile 187Os and relatively less in radiogenic 87Sr at ∼16 Ma, which directly corresponds with coeval shifts in seawater 187Os/188Os and 87Sr/86Sr. Results presented here provide substantial evidence that the onset of exhumation of 187Os‐enriched Lesser Himalayan strata could have significantly impacted the marine 187Os/188Os record at 16 Ma. These results support the hypothesis that regional weathering of isotopically unique source rocks can drive seawater records independently from shifts in global‐scale weathering rates, hindering the utility of these records as reliable proxies to track global weathering processes and climate in deep geologic time.

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Section: Himalayan Orogenesis and Cenozoic Seawater Chemistrymentioning

confidence: 99%

Zircon (U‐Th)/He Thermochronometric Constraints on Himalayan Thrust Belt Exhumation, Bedrock Weathering, and Cenozoic Seawater Chemistry

Colleps

McKenzie

Stöckli

et al. 2018

Geochem Geophys Geosyst

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“…In this ductile setting, ramps and flats on the Main Central Thrust resulted in imbrication or interleaving of the Lesser Himalayan Sequence and Greater Himalayan Sequence in the immediate vicinity of the thrust. Deformation was subsequently transferred to the Ramgarh thrust (Pearson & DeCelles 2005;Robinson & Pearson 2013;Webb 2013), which was responsible for finally exhuming the deformed Daling rocks in its hanging wall and thrusting them upon the Buxa rocks, inverting the original Daling-Buxa sedimentary relationship in the Lesser Himalayan Sequence (Fig. 2c).…”

Section: Provenance and Tectonic Implicationsmentioning

confidence: 99%

Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya

Mottram

Argles

Harris

et al. 2014

JGS

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Geochemical and geochronological analyses provide quantitative evidence about the origin, development and motion along ductile faults, where kinematic structures have been overprinted. The Main Central Thrust is a key structure in the Himalaya that accommodated substantial amounts of the India-Asia convergence. This structure juxtaposes two isotopically distinct rock packages across a zone of ductile deformation. Structural analysis, whole-rock Nd isotopes, and u-Pb zircon geochronology reveal that the hanging wall is characterized by detrital zircon peaks at c.

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“…The majority of the latter is thought to be accommodated by displacement along the Main Himalayan Thrust (MHT) [ Bilham et al , ; Larson et al , ]. The locus of the ~150–200 km of shortening in the frontal Himalaya [ Long et al , ; Mitra et al , ] was accommodated in the past by more hinterland‐located MHT‐parallel thrusts, such as the Main Central Thrust (MCT), with overall deformation propagating toward the foreland as collision progressed [ Robinson and McQuarrie , ; Robinson and Pearson , ].…”

Section: Introductionmentioning

confidence: 99%

Using U‐Th‐Pb petrochronology to determine rates of ductile thrusting: Time windows into the Main Central Thrust, Sikkim Himalaya

et al. 2015

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Quantitative constraints on the rates of tectonic processes underpin our understanding of the mechanisms that form mountains. In the Sikkim Himalaya, late structural doming has revealed time-transgressive evidence of metamorphism and thrusting that permit calculation of the minimum rate of movement on a major ductile fault zone, the Main Central Thrust (MCT), by a novel methodology. U-Th-Pb monazite ages, compositions, and metamorphic pressure-temperature determinations from rocks directly beneath the MCT reveal that samples from~50 km along the transport direction of the thrust experienced similar prograde, peak, and retrograde metamorphic conditions at different times. In the southern, frontal edge of the thrust zone, the rocks were buried to conditions of~550°C and 0.8 GPa between~21 and 18 Ma along the prograde path. Peak metamorphic conditions of~650°C and 0.8-1.0 GPa were subsequently reached as this footwall material was underplated to the hanging wall at~17-14 Ma. This same process occurred at analogous metamorphic conditions between~18-16 Ma and 14.5-13 Ma in the midsection of the thrust zone and between~13 Ma and 12 Ma in the northern, rear edge of the thrust zone. Northward younging muscovite 40 Ar/ 39 Ar ages are consistently~4 Ma younger than the youngest monazite ages for equivalent samples. By combining the geochronological data with the >50 km minimum distance separating samples along the transport axis, a minimum average thrusting rate of 10 ± 3 mm yr À1 can be calculated. This provides a minimum constraint on the amount of Miocene India-Asia convergence that was accommodated along the MCT.

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Was Himalayan normal faulting triggered by initiation of the Ramgarh–Munsiari thrust and development of the Lesser Himalayan duplex?

Cited by 36 publications

References 110 publications

Zircon (U‐Th)/He Thermochronometric Constraints on Himalayan Thrust Belt Exhumation, Bedrock Weathering, and Cenozoic Seawater Chemistry

Zircon (U‐Th)/He Thermochronometric Constraints on Himalayan Thrust Belt Exhumation, Bedrock Weathering, and Cenozoic Seawater Chemistry

Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya

Using U‐Th‐Pb petrochronology to determine rates of ductile thrusting: Time windows into the Main Central Thrust, Sikkim Himalaya

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