Two-stage cooling history of pelitic and semi-pelitic mylonite (sensu lato) from the Dongjiu–Milin shear zone, northwest flank of the eastern Himalayan syntaxis

Palin, Richard M.; Searle, Michael P.; St-Onge, M R; Waters, D. J.; Horstwood, Matthew; Parrish, Randall R.; Weller, Owen M.

doi:10.1016/j.gr.2014.07.009

Cited by 39 publications

(37 citation statements)

References 115 publications

(171 reference statements)

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“…Two analyses of one anhedral grain gave reproducible ages of c. 201 Ma (Table S5). This age is interpreted to date peak metamorphism in the sample, as monazite typically starts to grow in pelitic assemblages around the staurolite isograd (e.g., Palin et al, 2015;Smith and Barreiro, 1990;Weller et al, 2013). The result is consistent with a muscovite 40 Ar/ 39 Ar age of 155 ± 2 Ma reported for a schistose sample from the same locality (Harrison et al, 1995).…”

Section: X7supporting

confidence: 83%

Miocene magmatism in the Western Nyainqentanglha mountains of southern Tibet: An exhumed bright spot?

Weller

St-Onge

Rayner

et al. 2016

Lithos

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Section: X7supporting

confidence: 83%

Miocene magmatism in the Western Nyainqentanglha mountains of southern Tibet: An exhumed bright spot?

Weller

St-Onge

Rayner

et al. 2016

Lithos

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“…Localization of deformation is ubiquitous in Earth materials and observed over a broad range of scales in space and time (Fossen & Cavalcante, ). In the brittle upper crust, localization is represented by fault zones (Coyan et al, ; Valoroso et al, ) transitioning into localized ductile shear zones in the middle‐lower crust at the brittle‐ductile transition hosting mylonites and ultramylonites (Palin et al, ; Park & Jung, ). Localization within the deeper ductile lithosphere is accommodated by a combination of different deformation mechanisms, for example, diffusion and dislocation creep, frictional sliding, or cataclasis, depending on mineral composition and boundary conditions (Burlini & Bruhn, ; Kenkmann & Dresen, ).…”

Section: Introductionmentioning

confidence: 99%

Strain Localization and Weakening Processes in Viscously Deforming Rocks: Numerical Modeling Based on Laboratory Torsion Experiments

et al. 2019

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Localization processes in the viscous lower crust generate ductile shear zones over a broad range of scales affecting long-term lithosphere deformation and the mechanical response of faults during the seismic cycle. Here we use centimeter-scale numerical models in order to gain detailed insight into the processes involved in strain localization and rheological weakening in viscously deforming rocks. Our 2-D Cartesian models are benchmarked to high-temperature and high-pressure torsion experiments on Carrara marble samples containing a single weak Solnhofen limestone inclusion. The models successfully reproduce bulk stress-strain transients and final strain distributions observed in the experiments by applying a simple, first-order softening law that mimics rheological weakening. We find that local stress concentrations forming at the inclusion tips initiate strain localization inside the host matrix. At the tip of the propagating shear zone, weakening occurs within a process zone, which expands with time from the inclusion tips toward the matrix. Rheological weakening is a precondition for shear zone localization, and the width of this shear zone is found to be controlled by the degree of softening. Introducing a second softening step at elevated strain, a high strain layer develops inside the localized shear zone, analogous to the formation of ultramylonite bands in mylonites. These results elucidate the transient evolution of stress and strain rate during inception and maturation of ductile shear zones.

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“…Localization of deformation is ubiquitous in Earth materials and observed over a broad range of scales in space and time (Fossen & Cavalcante, 2017). In the brittle upper crust, localization is represented by fault zones (Coyan et al, 2013;Valoroso et al, 2013) transitioning into localized ductile shear zones in the middle-lower crust at the brittle-ductile transition hosting mylonites and ultramylonites (Palin et al, 2014;Park & Jung, 2017). Localization within the deeper ductile lithosphere is accommodated by a combination of different deformation mechanisms, for example, diffusion and dislocation creep, frictional sliding, or cataclasis, depending on mineral composition and boundary conditions (Burlini & Bruhn, 2005;Kenkmann & Dresen, 2002).…”

Section: Introductionmentioning

confidence: 99%

Strain Localization and Weakening Processes in Viscously Deforming Rocks: Numerical Modeling Based on Laboratory Torsion Experiments

Doehmann¹,

Brune²,

Nardini³

et al. 2018

Preprint

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Localization processes in the viscous lower crust lead to the formation of deformation zones over a broad range of scales that may affect the mechanical response of faults in the upper crust during the entire seismic cycle. In order to gain detailed insight into the processes involved in strain localization and rheological weakening in viscously deforming rocks we conduct centimeter-scale numerical models. Our 2D Cartesian models are benchmarked to high-temperature and high-pressure torsion experiments on Carrara marble samples containing a single weak Solnhofen limestone inclusion. The numerical models successfully reproduce bulk stress-strain transients and final strain distributions observed in the experiments by applying a simple softening law that mimics rheological weakening. By varying softening parameter values within this modeling framework, we quantify the impact of rheological weakening on localization and shear zone formation.We find that local stress concentrations forming at the inclusion tips initiate strain localization inside the host matrix. Rheological weakening is a precondition for shear zone formation within the matrix. At the tip of the propagating shear zone, weakening occurs within a process zone which expands with time from the inclusion tips towards the matrix. Shear zone width is found to be controlled by the degree of softening. Introducing a second softening step at elevated strain, a high strain layer develops inside the localized shear zone, analogue to the formation of ultramylonite bands in mylonites.

show abstract

Two-stage cooling history of pelitic and semi-pelitic mylonite (sensu lato) from the Dongjiu–Milin shear zone, northwest flank of the eastern Himalayan syntaxis

Cited by 39 publications

References 115 publications

Miocene magmatism in the Western Nyainqentanglha mountains of southern Tibet: An exhumed bright spot?

Miocene magmatism in the Western Nyainqentanglha mountains of southern Tibet: An exhumed bright spot?

Strain Localization and Weakening Processes in Viscously Deforming Rocks: Numerical Modeling Based on Laboratory Torsion Experiments

Strain Localization and Weakening Processes in Viscously Deforming Rocks: Numerical Modeling Based on Laboratory Torsion Experiments

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