Strain Analysis of the Shear Zones of Ambaji Granulite in the South Delhi Terrane of the Aravalli-Delhi Mobile Belt, NW India, and its Implication on the Exhumation of the Mid-lower Crustal Rocks
Authors
-
Department of Earth Sciences, IIT Bombay, Powai, Mumbai-400076
Ragini Saraswati -
Department of Earth Sciences, IIT Bombay, Powai, Mumbai-400076
Neeraj Kumar Sharma
-
Department of Earth Sciences, IIT Bombay, Powai, Mumbai-400076
Tapas Kumar Biswal
DOI:
https://doi.org/10.17491/jgsi/2024/173957Keywords:
Ambaji granulite, exhumation, Aravalli-Delhi mobile belt, thrusting, strike-slip shearing, termination splay, 2D-3D strain analysis, VorticityAbstract
Kilometer-scale granulite pockets bounded by shear zones occur within low to medium-grade rocks of the Precambrian mobile belts. Emplacement kinematics of such deeper rocks is reflected in the strain pattern of the associated shear zones. We have carried out the strain analysis of the shear zones of the Ambaji granulite in the Neoproterozoic South Delhi Terrane of the Aravalli-Delhi Mobile belt, NW India. The Kui-Chitraseni shear zone is the main strand and the other shear zones imbricates from it. The shear zones record an earlier phase of thrust kinematics in granulite grade that was primarily responsible for exhuming the rocks from the mid-lower crust. Later a strike-slip shearing was superimposed on those shear zones when the retrogression of the granulites took place. Strain and vorticity analysis of strike-slip shear indicates a transpressive strain consisting of pure and simple shear in different proportions, that led to further extrusion of granulite. Strain gradually diminishes towards the termination points of each shear zone and from center to wall. We have modeled the shear zones in the form of a splay which initiated as a leading thrust splay, transformed into a strike-slip transpressional splay, and subsequently as an extensional termination splay. Extensional splay further contributed to tectonic erosion and exhumation of granulite.
Downloads
Metrics
Issue
Section
Downloads
Published
How to Cite
References
Anderson, J.B. (1999) Antarctic marine geology. Cambridge University Press. Piedmont, USA. Geol. Soc. London, Spec. Publ., v.224, pp.249-264.
Bailey, C.M., Francis, B.E., Fahrney, E.E. (2004) Strain and vorticity analysis of transpressional high-strain zones from the Virginia Piedmont, USA. Geol. Soc. London, Spec. Publ., v.224(1), pp.249-264.
Behyari, M., Shahbazi, M. (2019) Strain and vorticity analysis in the Zagros suture zone (W Iran): Implications for Neo-Tethys post-collision events. Jour. Struct. Geol., v.126, pp.198-209.
Bhowmik, S.K., Dasgupta, S., Baruah, S., Kalita, D. (2018) Thermal history of a Late Mesoproterozoic paired metamorphic belt (?) during Rodinia assembly: New insight from medium-pressure granulites from the AravalliDelhi Mobile Belt, Northwestern India. Geosci. Front., v.9(2), pp.335354.
Biswal, T.K. (1988) Polyphase deformation in Delhi rocks, southeast of Amirgad, Banaskantha district of Gujarat. Geol. Soc. India Mem., no..7, pp.267-277.
Biswal, T.K., Gyani, K.C., Parthasarathy, R., Pant, D.R. (1998a) Implications of the geochemistry of the pelitic granulites of the Delhi supergroup, Aravalli Mountain Belt, northwestern India. Precambrian Res., v.87, pp.7585.
Biswal, T.K., Gyani, K.C., Parthasarathy, R., Pant, D.R. (1998b) Tectonic implication of geochemistry of gabbronorite-basic granulite suite in the Proterozoic Delhi Supergroup, Rajasthan, India. Jour. Geol. Soc. India, v.52, pp.721-732.
Biswal, TK., Pradhan, R.M., Sharma, N.K., Tiwari, S.K., Beniest, A., Behera, B.M., Singh, S., Saraswati, R., Bhardwaj, A., Umasankar, B.H., Singh, Y.K., Sarkar, S., Mahadani, T., Saha, G. (2022) A review on deformation structures of different terranes in the Precambrian Aravalli-Delhi Mobile Belt (ADMB), NW India: Tectonic implications and global correlation. Earth-Sci. Rev., v.203, p.104037.
Boyer, S.E., Elliotte, D. (1982) Thrust System. AAPG Bull., v.66, pp.11961230.
Bretherton, F.P. (1962) The motion of rigid particles in a shear flow at low Reynolds number. Jour. Fluid Mech., v.14(2), pp.284-304.
Butler, R.W.H. (1982) The terminology of structures I thrust belt. Jour. Struct. Geol., v.4(3), pp.239-245.
Choudhury, M.R., Das, S., Chatterjee, S.M., Sengupta, S. (2016) Deformation of footwall rock of Phulad Shear Zone, Rajasthan: evidence of transpressional shear zone. Jour. Earth Syst. Sci., v.125, pp.1033-1040.
Cloos, E. (1947) Oölite deformation in the South Mountain fold, Maryland. Geol. Soc. Amer. Bull., v.58, pp.843-918.
Cottle, J.M., Larson, K.P., Kellett, D.A. (2015) How does the mid-crust accommodate deformation in large, hot collisional orogens? A review of recent research in the Himalayan orogen. Jour. Struct. Geol., v.78, pp.119133.
Dasgupta, N., Mukhopadhyay, D., Bhattacharyya, T. (2012) Analysis of superposed strain: a case study from Barr Conglomerate in the South Delhi Fold Belt, Rajasthan, India. Jour. Struct. Geol., v.34, pp.30-42.
De Joussineau, G., Mutlu, O., Aydin, A., Pollard, D.D. (2007). Characterization of strike-slip fault–splay relationships in sandstone. Jour. Struct. Geol., v.29(11), pp.1831-1842.
De Paor, D.G. (1980) Some limitations of the Rf/ö technique of strain analysis. Tectonophysics, v.64, pp.29-31.
Desai, S.J., Patel, M.P., Merh, S.S. (1978) Polymetamorphites of BalamarAbu Road area, north Gujarat and southwestern Rajasthan. Jour. Geol. Soc. India, v.19, pp.383-394.
Dewey, J.F., Holdsworth, R.E., Strachan, R.A. (1998) Transpression and transtension zones. Geol. Soc. London, Spec. Publ., v.135(1), pp.1-14.
Dharma Rao, C.V., Santosh, M., Kim, S.W. (2012) Cryogenian volcanic arc in the NW Indian Shield: Zircon SHRIMP U Pb geochronology of felsic tuffs and implications for Gondwana assembly. Gondwana Res., v.22, pp.36-53.
Dunnet, D. (1969) A technique of finite strain analysis using elliptical particles. Tectonophysics, v.7(2), pp.117-136.
Fareeduddin, M., Basavalingu, B., Janardhan, A. (1994) PT conditions of pelitic granulites and associated charnockites of Chinwali area, west of Delhi fold belt, Rajasthan. Jour. Geol. Soc. India, v.43, pp.169-178.
Flinn, D. (1962) On folding during three-dimensional progressive deformation. Quart. Jour. Geol. Soc., v.118(1-4), pp.385-428.
Forte, A.M., Bailey, C.M. (2007) Testing the utility of the porphyroclast hyperbolic distribution method of kinematic vorticity analysis. Jour. Struct. Geol., v.29(6), pp.983-1001.
Fossen, H. (2016) Structural Geology. Cambridge University Press (2nd Ed.), Cambridge, 463p.
Fossen, H., Cavalcante, G.C.G. (2017) Shear zones–A review. Earth-Sci. Rev., v.171, pp.434 -455.
Fossen, H., Tikoff, B. (1993) The deformation matrix for simultaneous simple shearing, pure shearing and volume change, and its application to transpression-transtension tectonics. Jour. Struct. Geol., v.15(3-5), pp.413422.
Ghosh, S.K., Ramberg, H. (1976) Reorientation of inclusions by combination of pure shear and simple shear. Tectonophysics, v.34, pp.1-70.
Godin, L., Grujic, D., Law, R.D., Searle, M.P. (2006) Channel flow, ductile extrusion and exhumation in continental collision zones: an introduction. Geol. Soc. London, Spec. Publ., v.268(1), pp.1-23.
Graziani, R., Larson, K.P., Law, R.D., Vanier, M.A., Thigpen, J.R. (2021) A refined approach for quantitative kinematic vorticity number estimation using microstructures. Jour. Struct. Geol., v.153, p.104459.
Gregory, L.C., Meert, J.G., Bingen, B., Pandit, M.K., Torsvik, T.H. (2009) Paleomagnetism and geochronology of the Malani Igneous Suite, Northwest India: Implications for the configuration of Rodinia and the assembly of Gondwana. Precambrian Res., v.170(1-2), pp.13-26.
Gupta, S.N., Arora, Y.K., Mathur, R.K., Iqbaluddin, B.P., Sahai, T.N., Sharma, S.B., Murthy, M.V.N. (1980) Lithostratigraphic Map of Aravalli region, Southern Rajasthan and Northeastern Gujarat. Geol. Surv. India, Hyderabad.
Hatcher, R.D. (1995) Structural geology: Principles, concepts, and problems. Prentice and Hall. Englewood Cliffs, New Jersey, 525pp.
Heron, A.M. (1953) The geology of central Rajputana. Mem. Geol. Surv. India, v.79, 389p.
Hossack, J.R. (1968) Pebble deformation and thrusting in the Bygdin area (S. Norway). Tectonophysics, v.5, pp.315-339.
Jeffery, G.B. (1922) The motion of ellipsoidal particles immersed in a viscous fluid. Proc. R. Soc. London Series A, Containing papers of a mathematical and physical character, v.102, pp.161-179.
Jessup, M.J., Law, R.D., Frassi, C. (2007) The rigid grain net (RGN): an alternative method for estimating mean kinematic vorticity number (Wm). Jour. Struct. Geol., v.29, pp.411-421.
Joshi, G., Agarwal, A., Agarwal, K.K., Srivastava, S., Valdivia, L.A. (2017) Microstructures and strain variation: evidence of multiple splays in the north Almora thrust zone, Kumaun lesser Himalaya, Uttarakhand, India. Tectonophysics, v.694, pp.239-248.
Just, J., Schulz, B., De Wall, H., Jourdan, F., Pandit, M.K. (2011) Monazite CHIME/EPMA dating of Erinpura granitoid deformation: Implications for Neoproterozoic tectonothermal evolution of NW India. Gondwana Res., v.19, pp.402-412.
Khan, T., Khan, M.S. (2015) Clastic rock geochemistry of Punagarh basin, trans-Aravalli region, NW Indian shield: implications for paleoweathering, provenance, and tectonic setting. Arab. Jour. Geosci., v.8, pp.3621-3644.
Kroner, A., Stern, R.J. (2005). AFRICA | Pan-African Orogeny. In: Selley, R.C. et al. (Eds.), Encyclopedia of Geology. Elsevier, pp.1-12.
Law, R.D. (1990) Crystallographic fabrics: a selective review of their applications to research in structural geology. Geol. Soc. London, Spec. Publ., v.54, pp.335-352.
Law, R.D., Knipe, R.J., Dayan H. (1984) Strain path partitioning within thrust sheets: microstructural and petrofabric evidence from the Moine Thrust zone at Loch Eriboll, northwest Scotland. Jour. Struct. Geol, v.6, pp.477– 497.
Law, R.D., Searle, M.P., Simpson, R.L. (2004) Strain, deformation temperatures and vorticity of flow at the top of the Greater Himalayan Slab, Everest Massif, Tibet. Jour. Geol. Soc., v.161(2), pp.305-320.
Lin, S., Jiang, D. (2001) Using along-strike variation in strain and kinematics to define the movement direction of curved transpressional shear zones: An example from northwestern Superior Province, Manitoba. Geology, v.29, pp.767-770.
Lin, S., Jiang, D., Williams, P.F. (1998) Transpression (or transtension) zones of triclinic symmetry: natural example and theoretical modelling. Geol. Soc. London, Spec. Publ., v.135(1), pp.41-57.
Lisle, R.J. (1985) Geological strain analysis: A manual for the Rf/0 technique. Pergamon Press.
Lister, G.S., Snoke, A.W. (1984) SC mylonites. Jour. Struct. Geol., v.6, pp.617638.
Lode, W. (1926) Experiments on the influence of the mean principal stress on the flow of the metals iron, copper and nickel. Jour. Phys., v.36, pp.913939.
Mahan, K.H, Goncalves, P., Williams, M.L., Jercinovic, A.M. (2006) Dating metamorphic reactions and fluid flow: application to exhumation of high P granulites in a crustal scale shear zone, western Canadian Shield. Jour. Metamorph. Geol., v.24, pp.193-217.
Massironi, M., Kim, Y.S. (2014) Strike slip faults. Encyclopedia of Planetary Landforms, Springer, pp.1-12.
McClay, K.R. (1992) Thrust tectonics. Springer Science & Business Media, 435p.
Means, W.D., Hobbs, B.E., Lister, G.S., Williams, P.F. (1980) Vorticity and non-coaxiality in progressive deformations. Jour. Struct. Geol., v.2, pp.371378.
Meert, J.G., Santosh, M. (2017) The Columbia supercontinent revisited. Gondwana Res., v.50, pp.67 6 83.
Merschat, A.J., Hatcher Jr, R.D., Davis, T.L. (2005) The northern Inner Piedmont, southern Appalachians, USA: kinematics of transpression and SW-directed mid-crustal flow. Jour. Struct. Geol., v.27(7), pp.1252-1281.
Michels, Z.D., Kruckenberg, S.C, Davis, J.R., Tikoff, B. (2015) Determining vorticity axes from grain- scale dispersion of crystallographic orientations. Geology, v.43, pp.803-806.
Mitra, G. (1978) Ductile deformation zones and mylonites; the mechanical processes involved in the deformation of crystalline basement rocks. Am. Jour. Sci., v.278, pp.1057-1084.
Mookerjee, M., Mitra, G. (2009) Understanding kinematic data from the Moine thrust zone in terms of a kinematics-based mathematical model of deforming thrust wedges. Jour. Struct. Geol., v.31(12), pp.1556-1572.
Nádai, A. (1963) Theory of Flow and Fracture of Solids; McGraw-Hill, New York, 640pp.
Pant, N.C., Kundu, A., Joshi, S. (2008) Age of metamorphism of Delhi Supergroup rocks-electron microprobe ages from Mahendragarh district, Haryana. Jour. Geol. Soc. India, v.72, pp.365 6 372.
Passchier, C.W. (1987) Stable positions of rigid objects in non-coaxial flow— a study in vorticity analysis. Jour. Struct. Geol. v.9, pp.679-690.
Platt, J.P., Behrmann, J.H. (1986) Structures and fabrics in a crustal-scale shear zone, Betic Cordillera, SE Spain. Jour. Struct. Geol., v.8, pp.15-33.
Pradhan, R.M., Singh, A. Ojha, A.K., Biswal, T.K. (2022) Structural controls on bedrock weathering and its implications on groundwater resources. Sci. Rep., v.12(1), p.11815.
Prakash, A., Piazolo, S., Saha, L., Bhattacharya, A., Pal, D.K., Sarkar S. (2018) Deformation behavior of migmatites: insights from microstructural analysis of a garnet–sillimanite–mullite–quartz–feldspar-bearing anatectic migmatite at Rampura–Agucha, Aravalli–Delhi Fold Belt, NW India. Int. Jour. Earth Sci., v.107, pp.2265-2292.
Ramberg, H. (1975a) Superposition of homogeneous strain and progressive deformation in rocks. Bulletin of the Geological Institution of the University of Upsala, v.6, pp. 35-67.
Ramberg, H. (1975b) Particle paths, displacement and progressive strain applicable to rocks. Tectonophysics, v.28, pp.1-37.
Ramsay, J.G. (1967) Folding and Fracturing of rocks. McGraw Hill Book Company, 568p.
Ramsay, J.G., Graham, R.H. (1970) Strain variation in shear belts. Can. Jour. Earth Sci., v.7, pp.786-813.
Ramsay, J.G., and Allison, I. (1979) Structural analysis of shear zones in an alpinised Hercynian granite (Maggia Lappen, Pennine Zone, Central Alps).
Schweiz. Mineral. Petrogr. Mitt., v.59, pp.251-279 Ramsay, J.G., Huber, M.I. (1983) The Techniques of Modern Structural Geology: Strain Analysis. Vol. 1. Academic Press, London.
Ramsay, J.G., Huber, M.I. (1987) The Techniques of Modern Structural Geology: Folds and Fractures. Vol. 2. Academic Press, London.
Ramsay, J.G., Lisle, R.J. (2000) Applications of continuum mechanics in structural geology. Vol. 3. Academic Press.
Reinhardt, J., Kleemann, U. (1994) Extensional unroofing of granulitic lower crust and related low-pressure, high-temperature metamorphism in the Saxonian Granulite Massif, Germany. Tectonophysics, v.238, pp.71-94.
Ruj, T., Dasgupta, N. (2014) Tectonic imprints within a granite exposed near Srinagar, Rajasthan, India. Jour. Earth Syst. Sci., v.123, pp.1361-1374.
Sanderson, D.J., Marchini, W.R.D. (1984) Transpression. Jour. Struct. Geol., v.6(5), pp.449-458.
Scholz, C.H. (1988) The brittle-plastic transition and the depth of seismic faulting. Geol. Rundsch., v.77, pp.319–328.
Scholz, C.H., Ando, R., Shaw, B.E. (2010) The mechanics of first order splay faulting: The strike-slip case. Jour. Struct. Geol., v.32, pp.118-126.
Searle, M.P., Szulc, A.G. (2005) Channel flow and ductile extrusion of the high Himalayan slab-the Kangchenjunga–Darjeeling profile, Sikkim Himalaya. Jour. Asian Earth Sci., v.25, pp.173-185.
Sengupta, S., Ghosh, S.K. (2004) Analysis of transpressional deformation from geometrical evolution of mesoscopic structures from Phulad shear zone, Rajasthan, India. Jour. Struct. Geol., v.26, pp.1961-1976.
Seymour, D.B., Boulter, C.A. (1979) Tests of computerized strain analysis methods by the analysis of simulated deformation of natural unstrained sedimentary fabrics. Tectonophysics, v.58, pp.221-235.
Sibson, R.H. (1977) Fault rocks and fault mechanisms. Jour. Geol. Soc., v.133, pp.191-213.
Simpson, C., De Paor, D.G. (1993) Strain and kinematic analysis in general shear zones. Jour. Struct. Geol., v.15, pp.1-20.
Simpson, C., De Paor, D.G. (1997) Practical analysis of general shear zones using the porphyroclast hyperbolic distribution method: an example from the Scandinavian Caledonides. In: Sengupta, S. (Ed.), Evolution of Geological Structures in Micro- to Macro-Scales. Chapman and Hall, pp.169-184.
Singh, Y.K., de Waele, B., Karmarkar, S., Sarkar, S., Biswal, T.K. (2010) Tectonic setting of the Balaram–Kui–Surpagla–Kengora granulites of the Aravalli Mobile Belt, NW India and its implication on correlation with the East African Orogen in the Gondwana assembly. Precambrian Res., v.183, pp.669-688.
Singh, S., De Waele, B., Shukla, A., Umasankar, B.H., Biswal, T.K. (2021) Tectonic fabric, geochemistry, and zircon-monazite geochronology as proxies to date an orogeny: example of South Delhi Orogeny, NW India, and implications for East Gondwana tectonics. Front. Earth Sci., v.8, p.711.
Sinha-Roy, S. (1988) Proterozoic Wilson cycles in Rajasthan. In: Roy A.B. (Ed.), Precambrian of the Aravalli Mountain, Rajasthan, India. Mem. Geol. Soc. India, no.7, pp.95–108.
Srikarni, C., Desai, S.J., Limaye, M.A. (2000) Plumose symplectites—A case of osumilite break-down in Pelitic granulites of North Gujarat. Proc. Nat. Sem. Precambrian Terrains, pp.265-274.
Stahr III, D.W., Law, R.D. (2011) Effect of finite strain on clast-based vorticity gauges. Jour. Struct. Geol., v.33, pp.1178-1192.
Stahr III, D.W., Law, R.D. (2014) Strain memory of 2D and 3D rigid inclusion populations in viscous flows—What is clast SPO telling us? Jour. Struct. Geol., v.68, pp.347-363.
Suo, S., Zhong, Z., You, Z. (2000) Extensional deformation of post ultrahighpressure metamorphism and exhumation process of ultrahigh-pressure metamorphic rocks in the Dabie massif, China. China Earth Sci. Series D, v.43, pp.225-236.
Sylvester, A.G. (1988) Strike-slip faults. Geol. Soc. Amer. Bull., v.100, pp.1666-1703.
Thiessen, E.J., Gibson, H.D., Regis, D., Pehrsson, S. (2018) Deformation and extensional exhumation of 1.9 Ga high-pressure granulites along the Wholdaia Lake shear zone, south Rae craton, Northwest Territories, Canada. Lithosphere, v.10 (5), pp.641-661.
Thigpen, J.R., Law, R.D., Lloyd, G.E., Brown, S.J. (2010) Deformation temperatures, vorticity of flow, and strain in the Moine thrust zone and Moine nappe: Reassessing the tectonic evolution of the Scandian forelandhinterland transition zone. Jour. Struct. Geol., v.32, pp.920-940.
Tikoff, B., Fossen, H. (1995) The limitations of three-dimensional kinematic vorticity analysis. Jour. Struct. Geol., v.17, pp.1771-1784.
Tiwari, S.K., Biswal, T.K. (2019) Dynamics, EPMA Th U total Pb monazite geochronology and tectonic implications of deformational fabric in the lower middle crustal rocks: A case study of Ambaji granulite, NW India. Tectonics, v.38, pp.2232-2254.
Tiwari S.K., Beniest A., Biswal T.K. (2020a) Variation in vorticity of flow during exhumation of lower crustal rocks (Neoproterozoic Ambaji granulite, NW India). Jour. Struct. Geol., v.30, p.103912.
Tiwari, S.K., Beniest, A., Biswal, T.K. (2020b) Extension driven brittle exhumation of the lower-middle crustal rocks, a paleostress reconstruction of the Neoproterozoic Ambaji Granulite, NW India. Jour. Asian Earth Sci., v.195, 104341.
Truesdell, C. (1953) Two measures of vorticity. Jour. Ration. Mech. Analysis, v.2, pp.173-217.
Twiss, R.J., Moores, E.M. (1992) Structural Geology. W.H. Freeman & Company, New York, 532p.
Van Lente, B., Ashwal, L.D., Pandit, M.K., Bowring, S.A., Torsvik, T.H. (2009) Neoproterozoic hydrothermally altered basaltic rocks from Rajasthan, northwest India: Implications for late Precambrian tectonic evolution of the Aravalli craton. Precambrian Res., v.170, pp.202-222.
Vollmer, F.W. (2010) A comparison of ellipse-fitting techniques for two and three-dimensional strain analysis, and their implementation in an integrated computer program designed for field-based studies. In AGU Fall Meeting Abstracts Vol. 2010, pp. T21B-2166.
Vollmer, F.W. (2017) EllipseFit: Strain and Fabric Analysis Software User Manual Version 3.4.0 [computer software user manual].
Wallis, S.R. (1992) Vorticity analysis in a metachert from the Sanbagawa Belt, SW Japan. Jour. Struct. Geol., v.14, pp.271-280.
Wallis, S.R. (1995) Vorticity analysis and recognition of ductile extension in the Sanbagawa belt, SW Japan. Jour. Struct. Geol., v.17, pp.1077-1093.
Wallis, S., Platt, J.P., Knott, S.D. (1993) Recognition of syn-convergence extension in accretionary wedges with examples from the Calabrian Arc and the Eastern Alps. Amer. Jour. Sci., v.293, pp.463-494.
Wells, M.L. (2001) Rheological control on the initial geometry of the Raft River detachment fault and shear zone, western United States. Tectonics, v.20, pp.435-457.
Wheeler, J. (1986) Strain analysis in rocks with pretectonic fabrics. Jour. Struct. Geol., v.8, pp.887-896.
Woodcock, N.H., Fischer, M. (1986) Strike slip duplexes. Jour. Struct. Geol., v.8(7), pp.725-735.
Xypolias, P. (2009) Some new aspects of kinematic vorticity analysis in naturally deformed quartzites. Jour. Struct. Geol., v.31, pp.3-10.
Xypolias, P. (2010) Vorticity analysis in shear zones: a review of methods and applications. Jour. Struct. Geol., v.32, pp.2072-2092.
Xypolias, P., Chatzaras, V., Beane, R., Papadopoulou, S. (2013) Heterogeneous constrictional deformation in a ductile shear zone resulting from the transposition of a lineation-parallel fold. Jour. Struct. Geol., v.52, pp.44-59.
Xypolias, P., Kokkalas, S. (2006) Heterogeneous ductile deformation along a mid-crustal extruding shear zone: an example from the External Hellenides (Greece). Geol. Soc. London, Spec. Publ., v.268, pp.497-516.
Xypolias, P., Koukouvelas, I.K. (2001) Kinematic vorticity and strain rate patterns associated with ductile extrusion in the Chelmos Shear Zone (External Hellenides, Greece). Tectonophysics, v.338, pp.59-77.
