Vorticity estimates based on porphyroclasts analysis are limited by the extrapolation to three dimensions of two-dimensional data. We describe a 3D approach based on the use of X-ray micro-computed tomography that better reflects the real 3D geometry of the porphyroclasts population. This new approach for kinematic vorticity analysis in the Munsiari Thrust mylonites, the lower boundary of the Main Central Thrust zone (MCTz) in Indian Himalaya, indicates a large pure shear component during non-coaxial shearing. 40Ar/39Ar ages of micas along the mylonitic foliation of the Munsiari and Vaikrita thrusts (the upper boundary of the MCTz) constrain thrust activity to 5–4 and 8–9 Ma, respectively. Available kinematic vorticity analyses of the Vaikrita mylonites suggest the dominance of a simple shear component. Combining these data, we suggest that the southward and structurally downward shift of deformation along the MCTz was accompanied by a progressive increase in the pure shear component in a general shear flow.

Montemagni, C., Carosi, R., Fusi, N., Iaccarino, S., Montomoli, C., Villa, I., et al. (2020). Three‐dimensional vorticity and time‐constrained evolution of the Main Central Thrust zone, Garhwal Himalaya (NW India). TERRA NOVA, 32(3), 215-224 [10.1111/ter.12450].

Three‐dimensional vorticity and time‐constrained evolution of the Main Central Thrust zone, Garhwal Himalaya (NW India)

Montemagni, Chiara
;
Fusi, Nicoletta;Villa, Igor M.;Zanchetta, Stefano
2020

Abstract

Vorticity estimates based on porphyroclasts analysis are limited by the extrapolation to three dimensions of two-dimensional data. We describe a 3D approach based on the use of X-ray micro-computed tomography that better reflects the real 3D geometry of the porphyroclasts population. This new approach for kinematic vorticity analysis in the Munsiari Thrust mylonites, the lower boundary of the Main Central Thrust zone (MCTz) in Indian Himalaya, indicates a large pure shear component during non-coaxial shearing. 40Ar/39Ar ages of micas along the mylonitic foliation of the Munsiari and Vaikrita thrusts (the upper boundary of the MCTz) constrain thrust activity to 5–4 and 8–9 Ma, respectively. Available kinematic vorticity analyses of the Vaikrita mylonites suggest the dominance of a simple shear component. Combining these data, we suggest that the southward and structurally downward shift of deformation along the MCTz was accompanied by a progressive increase in the pure shear component in a general shear flow.
Articolo in rivista - Articolo scientifico
Shear zone, Kinematic vorticity RGN method, 3D microCT, Himalayan Main Central Thrust zone, 40Ar/39Ar geochronology
English
17-gen-2020
2020
32
3
215
224
reserved
Montemagni, C., Carosi, R., Fusi, N., Iaccarino, S., Montomoli, C., Villa, I., et al. (2020). Three‐dimensional vorticity and time‐constrained evolution of the Main Central Thrust zone, Garhwal Himalaya (NW India). TERRA NOVA, 32(3), 215-224 [10.1111/ter.12450].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/260176
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