Strain and Crystallographic Fabric in Mesoscopic Ductile Shear Zones of Garhwal Himalaya

Srivastava, H. K.; Sahai, Atul; Lal, S

doi:10.1016/s1342-937x(05)70297-5

Cited by 9 publications

(4 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In shear zones the increase in the foliation intensity can be related to an increase in strain intensity and also to a better developed crystallographic fabric (Srivastava et al 1995(Srivastava et al , 2000. The analysis of shear zones involves measurement of shear strain, amount and direction of tectonic transport, percentage of volume loss (Srivastava et al1995) and determination of compression direction.…”

Section: Shear Zone Analysismentioning

confidence: 99%

“…However, Ramsay and Huber (1987) explain that though the shear zones rotate during a progressive deformation, the direction of bulk shortening (obtuse bisector) and bulk stretching (acute bisector) maintains nearly constant orientations. Therefore, unless the shear field undergoes a significant change, bisectors of preferred orientations of conjugate shear zones should give a reasonable measure of compressional direction (Srivastava et al 2000).…”

Section: Shear Zone Analysismentioning

confidence: 99%

See 1 more Smart Citation

Structural analyses of the crystalline rocks between Dirang and Tawang, West Kameng district, Arunachal Himalaya

Srivastava

et al. 2011

J Geol Soc India

Self Cite

View full text Add to dashboard Cite

In Kameng Valley of Arunachal Pradesh, the crystalline rocks of Se La Group of Higher Himalaya are thrust over the Lesser Himalayan rocks of Dirang Formation, Bomdila Group along the Main Central Thrust and exhibit well preserved structures on macro-to microscopic scales. Detailed analysis of structures reveals that the rocks of the area have suffered four phases of deformation D 1 , D 2 , D 3 and D 4 . These structures have been grouped into (i) early structures (ii) structures related to progressive ductile thrusting and (iii) late structures. The early structures which developed before thrusting formed during D 1 and D 2 phases of deformation, synchronous to F 1 and F 2 phases of folding respectively. The structures related to progressive ductile shearing developed during D 3 phase of deformation, when the emplacement of the crystalline rocks took place over the rocks of Dirang Formation along the Main Central Thrust. Different asymmetric structures/kinematic indicators developed during this ductile/brittle-ductile regime suggest top-to -SSW sense of movement of the crystalline rocks of the area. D 4 is attributed to brittle deformation. Based on satellite data two new thrusts, i.e. Tawang and Se La thrusts have been identified parallel to Main Central Thrust, which are suggestive of imbricate thrusting. Strain analysis from the quartz grains of the gneissic rocks reveals constriction type of strain ellipsoid where k value is higher near the MCT, gradually decreases towards the north. Further, the dynamic analysis carried out on the mesoscopic ductile and brittle-ductile shear zones suggest a NNE-SSW horizontal compression corresponding to the direction of northward movement of Indian Plate.

show abstract

Section: Shear Zone Analysismentioning

confidence: 99%

Section: Shear Zone Analysismentioning

confidence: 99%

Structural analyses of the crystalline rocks between Dirang and Tawang, West Kameng district, Arunachal Himalaya

Srivastava

et al. 2011

J Geol Soc India

Self Cite

View full text Add to dashboard Cite

show abstract

“…Listric thrust faults and associated folds indicate that the frontal part of the wedge is a fold and thrust belt (FTB) (e.g., Schelling and Arita 1991;Schelling 1992;Srivastava and Mitra 1994;Powers et al 1998;Mukhopadhayay and Mishra 1999;Mukul 2000;Srivastava et al 2000;DeCelles et al 2002). The two major E-W trending thrusts in the Himalayan FTB are: the Main Central Thrust (MCT) and the Main Boundary Thrust (MBT).…”

Section: General Geologymentioning

confidence: 99%

Deformation mechanisms in the frontal Lesser Himalayan Duplex in Sikkim Himalaya, India

Matin

Mazumdar

2009

J Earth Syst Sci

View full text Add to dashboard Cite

Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to the complex nature of the deformed rocks and their genesis. Crustal deformation in the Himalayan thrust belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at depths controlled mainly by regional strain-rate and geothermal gradient. However, material property, grain-size and their progressive changes during deformation are also important controlling factors. We present evidence of EF deformation from Gondwana rocks developed during the emplacement of one of the frontal horses (Jorthang horse) in the Lesser Himalayan Duplex (LHD) structure associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the Rangit window near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand meso-structures from an undeformed protolith to cataclasite suggesting that it was emplaced under elastico-frictional conditions. Meso-to micro-scale shear fractures are seen developed in Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates are deformed by cataclastic flow suggesting that material property and grain-size have played an important role in the deformation of the Jorthang horse. In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation structures. This suggests that the Jorthang horse was emplaced under shallower crustal conditions than the antiformally folded Ramgarh thrust sheet even though the Ramgarh sheet presently overlies the Jorthang horse.

show abstract

“…Classically the finite strain of the rock is measured by deformed strain markers such as fossils, ooliths, pebbles and reduction spots (Flinn, 1956;Ramsay, 1967;Hossack, 1968;Burns and Spry, 1969;Dunnet, 1969;Ramsay and Huber, 1983;Lisle, 1985). In the last three decades quartz has received considerable attention for petrofabric and strain studies (White, 1977;Brunel, 1980;Lister and Hobbs, 1980;Mawer, 1982;Saha, 1989;Srivastava et al, 2000). This is partly due to its importance in controlling the rheology of large variety of fabric types found under different deformational and metamorphic conditions (Law, 1990).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a regional strain gradient in mylonitic quartzites from the footwall of the Main Central Thrust Zone (Garhwal Himalaya, India): Inferences from finite strain and AMS analyses

Tripathy

Srivastava

Mamtani

2009

Journal of Asian Earth Sciences

Self Cite

View full text Add to dashboard Cite

Strain and Crystallographic Fabric in Mesoscopic Ductile Shear Zones of Garhwal Himalaya

Cited by 9 publications

References 11 publications

Structural analyses of the crystalline rocks between Dirang and Tawang, West Kameng district, Arunachal Himalaya

Structural analyses of the crystalline rocks between Dirang and Tawang, West Kameng district, Arunachal Himalaya

Deformation mechanisms in the frontal Lesser Himalayan Duplex in Sikkim Himalaya, India

Evaluation of a regional strain gradient in mylonitic quartzites from the footwall of the Main Central Thrust Zone (Garhwal Himalaya, India): Inferences from finite strain and AMS analyses

Contact Info

Product

Resources

About