Refine your search
Collections
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Srivastava, Vaibhava
- Structural Analyses of the Crystalline Rocks between Dirang and Tawang, West Kameng District, Arunachal Himalaya
Abstract Views :246 |
PDF Views:0
Authors
Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi - 221 005, IN
1 Department of Geology, Banaras Hindu University, Varanasi - 221 005, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 78, No 1 (2011), Pagination: 45-56Abstract
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 D1, D2, D3 and D4. 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 D1 and D2 phases of deformation, synchronous to F1 and F2 phases of folding respectively. The structures related to progressive ductile shearing developed during D3 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. D4 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.Keywords
Crystalline Rocks, Structural Analyses, Main Central Thrust, Arunachal Himalaya.
- Mylonitic Microfabrics from the Rocks of MCT Zone in Alakhnanda Valley, Garhwal Himalaya
Abstract Views :176 |
PDF Views:0
Authors
Affiliations
1 Department of Geology, Banaras Hindu University, Varanasi-221 005, IN
1 Department of Geology, Banaras Hindu University, Varanasi-221 005, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 75, No Spl Iss 1 (2010), Pagination: 152-159Abstract
MCT Zone of Alakhnanda valley is a major ductile shear zone in Garhwal Himalaya, which is characterised by different types of mylonite rocks. On the basis of grain size and the percentage of matrix in the rock, zones comprising protomylonite, augen mylonite, mylonite and ultramylonite have been identified. The study of microstructures, grain size and crystallographic preferred orientation of quartz c-axis fabric reveals that the rocks of the MCT zone were deformed by a combination of intracrystalline creep (power law creep) and grain boundary migration (sliding super plasticity).Keywords
Microfabrics, Mylonite, MCT, Garhwal Himalaya.References
- BELL, T.H. and ETHERIDGE, M.A. (1973) Microstructures of mylonites and their descriptive terminology. Lithos, v.6, pp.337-348.
- BERTHE, D. CHOUKROUNE, P. and JEGOUZO, P. (1979) Orthogneiss Mylonite and coaxial deformation of granites: the example of the South Armorican shear zone. Jour. Struct. Geol., v.1, pp.31-42.
- BHATTACHARYA, A.R. and AGRAWAL, K.K. (1985) Mylonites from the Kumaun Lesser Himalaya. Neues Jahtbuch Miner. Abh., v.152, pp.65-77.
- BHATTACHARYA, A.R. and WEBER, K. (2004) Fabric development during shear deformation in the Main Central Thrust Zone, NW-Himalaya, India. Tectonophysics, v.387, pp.23-46.
- BOUILLIER,A.M. and GUEGUEN,Y. (1975) S-P mylonites: Origin of some mylonites by superplastic flow. Contrib. Mineral. Petrol., v.50, pp.93-104.
- ETCHECOPAR, A. (1977) A plane kinematic model of progressive deformation in a polycrystalline aggregate. Tectonophysics, v.92, pp.147-170.
- FUSSEIS F. and HANDY, M.R. (2008) Micromechanisms of shear zone propagation at the brittle-viscous transition Jour. Struct. Geol., v.30, pp. 1242-1253.
- GAIROLA, V.K. and ACKERMAND, D. (1988) Geothermobarometry of the Central Crystallines from the Garhwal Himalaya. Jour. Geol. Soc. India, v.31(2), pp.230-242.
- GAIROLA, V.K. and SRIVASTAVA, H.B. (1987) Deformational and metamorphic studies in the Central Crystallines around Joshimath, district Chamoli, U.P. In:V.K. Gairola (Ed.), Proc. Nat. Sem. on Tertiary Orogeny in Indian Subcontinent, pp.49-63.
- GANSSER,A. (1964) Geology of the Himalaya. Interscience, New York, 273p.
- HULL, J., (1988) Thickness-displacement relationships for deformation zones. Jour. Struct. Geol., v.10, pp.244-267.
- JAIN,A.K. (1971) Stratigraphy and tectonics of Lesser Himalayan region of Uttarkashi region, Garhwal Himalaya, U.P. Himalayan Geol., v.1, pp.25-57.
- JAIN, A.K., SINGH, SANDEEP and MANICKAVASAGAM, R.M. (2002) Himalayan Collision Tectonics. Gondwana Res. Group Mem., no.7, pp.1-144
- KOCH NORBERT and MASCH, LUDWIG (1992) Formation of Alpine mylonites and pseudotachylytes at the base of Silveretta nappe, Eastern Alps. Tectonophysics, v.204, pp.289-306.
- LE FORT, P. (1975) Himalayas: the collided range. Present knowledge of continental arc. Amer. Jour. Sci., v.275A, pp.1-44.
- LISTER, G.S. and SNOKE, A.W. (1984) S-C mylonites. Jour. Struct. Geol., v.6, pp.617-638.
- MEANS, W.D. (1984) Shear zones of types I and II and their significance for the reconstruction of rock history. Geol. Soc. Am. Bull., Abstract Programs, v.16, p.50.
- MEANS,W.D. (1995) Shear zones and rock history.Tectonophysics, v.247, pp.157-160.
- METCALFE, R. P. (1993) Pressure, temperature and time constraints on metamorphism across the Main Central Thrust zone and High Himalayan Slab in the Garhwal Himalaya. In: P.G.Trelaor and M.P. Searle, (Eds.), Himalayan Tectonics. Geol. Soc. Spec. Publ., v.74, pp.485-509.
- MITRA, G. (1984) Brittle to ductile transition due to large strains along the white rock thrust, Wind river mountains, Wyoming. Jour. Struct. Geol., v.6(1-2), pp.51-61.
- POIRIER, J.P. (1985) Creep of Crystals. High temperature deformation process in metals ceramic and minerals. Cambridge University Press. Cambridge, U.K., 260p.
- RAMSAY, J.G. (1980) Shear zone geometry: a review. Jour. Struct. Geol., v.2(1/2), pp.83-99.
- SCHMID, S.M. and CASEY, M. (1986) Complete fabric analysis of some commonly observed quartz c-axis fabric patterns. Geophys. Monogr.Am. Geophys. Union (The Paterson vol.), v.36, pp.263-286.
- SEARLE, M.P., METCALF, R.P. REX, A.J. and NORRY, M.J. (1993) Field relations, petrogenesis and emplacement of Bhagirathi Leucogranite, Garhwal Himalaya. In: P.J. Trelaor, and M.P Searle, (Eds) Himalayan Tectonics. Geol. Soc. London Spec. Publ., v.74, pp.429-444.
- SIBSON, R.H. (1977) Fault rocks and Fault mechanism. Jour. Geol. Soc. London, v.133, pp.191-213.
- SINGH, K. and THAKUR, V.C. (2001) Microstructure and strain variation across the footwall of the Main Central Thrust Zone, Garhwal Himalaya. Jour.Asian Earth Sci., v.19, pp.17-29.
- SRIVASTAVA, H.B. and TRIPATHY, N.R. (2005) Shear Zones structures from the Main Central Thrust Zone of the Joshimath area, Garhwal Himalaya. Spec. Publ. Paleont. Soc. India, no.2, pp.53-64.
- SRIVASTAVA, H.B. and TRIPATHY, N.R. (2007) Geometrical analysis of mesoscopic shear zones in the crystalline rocks of MCT Zone of Garhwal Higher Himalaya. Jour. Asian Earth Sci., v.30, pp.599-612.
- TAKAGI HIDEO (1986) Implications of mylonitic structures for the geotectonic evolution of the Median Tectonic Line, Central Japan. Jour. of Struc. Geol., v.8(1), pp.3-14.
- TURNER, F.J. and WEISS, L.E. (1963) Structural analysis of Metamorphic Tectonites. McGraw Hill, New York., 545p.
- URAI, J.L., MEANS, W.D. and LISTER, G.S. (1986) Dynamic recrystallization of minerals. In: B.E. Hobbs and H.C. Heard (Eds.), Mineral and Rock deformations; Laboratory Studies. Geophys. Monogr.Am. Geophysical Union, v.36, pp.161-199.
- VALDIYA, K.S. (1980) The two Intracrustal boundary thrusts of Himalaya. Tectonophysics, v.323, pp.323-348.
- VIRDI, N.S. (1986) Litho-stratigraphy and structure of Central Crystallines in the Alaknanda and Dhauliganga valleys in Garhwal Himalaya, U.P. In: P.S. Saklani (Ed.), Himalayan Thrusts and Associated Rocks. Current Trends in Geology, v.10 pp.155-166.
- WHITE, S.H., BURROWS, S.E., CARRERAS, J. SHAW, N.D. and HUMPHREYS, F.J. (1980) On mylonites in ductile shear zones. Jour. Struct. Geol., v.2(1/2), pp.175-187.