Investigation of deformation pattern using finite strain and kinematic vorticity analyses, Cheshmeh Sefid deformed area, Sanandaj-Sirjan metamorphic belt.

Samani, Babak; Charchi, Abbas; Faghih, Ali

Investigation of deformation pattern using finite strain and kinematic vorticity analyses, Cheshmeh Sefid deformed area, Sanandaj-Sirjan metamorphic belt.

Authors

¹ Faculty of Earth Sciences, Shahid Chamran University, Ahvaz, Iran

² Department of earth Sciences,Shiraz University, iran

Abstract

Deformed conglomerates and microconglomerates of Mesozoic in the Sanandaj-Sirjan Metamorphic Belt are the most suitable kinematic markers for the strain studies. The R / technique for two dimensional strain analysis show that the finite strain of X/Z plane in comparison to X/Y and Y/Z aspect ratios, is highest (Rs=5.4). The calculation of harmonic mean from axial ratio of extracted pebbles and transfer these data into Flinn diagram determine K= 0.6 to 0.9. Kinematic vorticity analysis of deformed porphyroclasts show that kinematic vorticity number (W_k) varies from 0.43 to 0.63. These amounts of W_k show that both simple and pure shear components act in this area. With application of the kinematic vorticity results the percent of pure and simple shear was determined so that (30% <simple shear < 42%) and (58 %< pure shear <70%). These results show the nature of deformation with pure shear dominated due to convergence movement between Afro-Arabian continental plane and Iranian microcontinent. Shortening values in the study area measured parallel to the XZ principal plane of the finite strain ellipsoid are calculated using strain and vorticity results. The estimated values of shortening generally range from 42% to 55% in the study area.

Keywords

References

Alavi, M., 1994. Tectonics of the Zagros orogenic belt of Iran: new data and interpretations. Tectonophysics 229, 211-238.

Alavi, M., 2004.Regional stratigraphy of the Zagros fold-thrust belt of Iran, and its proforeland evolution. American Journal of Science 304, 1–20.

Bailey, C.M., Gilmer, A.K., Marquis, M.N., 1999. A tale of two shear zones: the vorticity and strain path of two greenschist facies shear zones. Geological Society of America Abstracts with Programs 31 (7), 59.

Berberian, M., King, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran. Canadian Journal of Earth Sciences 18, 210–265.

De Paor, D.G., 1988. R/ strain analysis using an orientation net. Journal of Structural Geology 10, 323–333.

Dewey, J.F., Pitman, W.C. III, Ryan, W.B.F., Bonnin, J., 1973. Plate tectonics and the evolution of the Alpine System. Geological Society of America Bulletin 84, 3137–3180.

Eshraghi, S.A., Roshan Ravan, J., Sabzehei, M., 1999. Geological map of the Quatruyeh area, scale 1:100,000. Geological Survey of Iran.

Fort, A.M., Bailey, C.M., 2007. Testing the utility of the porphyroclast hyperbolic distribution method of kinematic vorticity analysis. Journal of Structural Geology 29, 983–1001.

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. Journal of the Geological Society, London 161, pp. 305–320.

Lin, S., Jiang, D., Williams, P.F., 1998. Transpression (or transtension) zones of triclinic symmetry: natural example and theoretical modelling. In: Holdsworth, R.E., Strachan, R.A., Dewey, J.F. (Eds.), Continental Transpressional and Transtensional Tectonics. Special Publication of the Geological Society, London 135, pp. 41–57.

McClay, K.R., Whitehouse, P.S., Dooley, M and Richards, M., 2004. 3D evolution of fold and thrust belts formed by oblique convergence. Marine and Petroleum Geology 21, 857-877.

Mc Quarrie, N., 2004. Crustal scale geometry of the Zagros fold–thrust belt, Iran. Journal of Structural Geology 26, 519–535.

Means, W.D., Hobbs, B.E., Lister, G.S., Williams, P.F., 1980. Vorticity and noncoaxiality in progressive deformations. Journal of Structural Geology 2, 371–378.

Meere, P.A., Mulchrone, K.F., 2003. The effect of sample size on geological strain estimation from passively deformed clastic sedimentary rocks. Journal of Structural Geology 25, 1587-1595.

Mohajjel, M., Fergusson, C.L., 2000. Dextral transpression in Late Cretaceous continental collision, Sanandaj–Sirjan Zone, western Iran. Journal of Structural Geology, 22, 1125-139.

Passchier, C. W., Trouw, R. A. J., 2005. Microtectonics. Springer-Verlag, Berlin. 336p.

Ramsay, J.G., Huber, M.I., 1983. The Techniques of Modern Structural Geology, Volume 1. Strain Analysis. Academic Press, London.

Ramsay, J.G., Wood, D.S., 1973. The geometric effects of volume change during deformation processes. Tectonophysics 16, 263-277.

Samani, B., 2010. Finite strain and deformation flow geometry in the Sanandaj-Sirjan HP-LT metamorphic belt, Iran. Ph.D thesis, Shiraz University, Iran.

Sarkarinejad, K., 1999. Tectonic finite strain analysis using Ghuri deformed conglomerate, Neyriz area Southwestern Iran. Iranian Journal of Science and Technology 23, 351–363.

Sarkarinejad, K., Azizi, A., 2008. Slip partitioning and inclined dextral transpression along the Zagros Thrust System, Iran. Journal of Structural Geology 30, 116–136.

Sarkarinejad, K., Faghih, A., Grasemann, B., 2008. Transpressional deformations within the Sanandaj-Sirjan Metamorphic Belt (ZagrosMountains, Iran). Journal of Structural Geology 30, 818–826.

Sarkarinejad, K., Samani, B., Faghih, A., Grasemann, B., Moradipoor, M., 2010. Implications of strain and vorticity of flow analyses to interpret the kinematics of an oblique convergence event (Zagros Mountains, Iran). Journal of Asian Earth Sciences 38, 34–43.

Sheikholeslami, M.R., Pique, A., Mobayen, P., Sabzehei, M., Bellon, H., Hashem Emami, M., 2008. Tectono-metamorphic evolution of the Neyriz metamorphic complex, Quri-Kor-e-Sefid area (Sanandaj-Sirjan Zone, SW Iran). Journal of Asian Earth Sciences 31, 504–521.

Simpson, C., De Paor, D. G. 1997. Practical analysis of general shear zones using 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, London, 169–184.

Stocklin, J. 1968. Structural history and tectonics of Iran. A review. American Association of Petroleum Geologists Bulletin 52, 1229-1258.

Treagus, S.H., Treagus, J.E., 2002. Studies of strain and rheology of conglomerates. Journal of Structural Geology 24, 1541-1567.

Truesdell, C., 1953. Two measures of vorticity. Journal of Rotational Mechanical Analysis 2, 173-217.

Wallis, S.R., 1992. Vorticity analysis in a metachert from the Sanbagawa belt, SW Japan. Journal of Structural Geology 14, 271-280.

Wallis, S., 1995. Vorticity analysis and recognition of ductile extension in the Sanbagawa belt, SW Japan. Journal of Structural Geology 17, 1077–1093.

Wallis, S. R., 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. American Journal of Science, 293, 463–495.

Xypolias, P., 2010. Vorticity analysis in shear zones: A review of methods and applications. Journal of Structural Geology 32, 2072–2092.