Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

The Geometric, Kinematics and Deformation Stage Analysis of Metamorphic Rocks around Mashhad

Document Type : Original Research Paper

Authors
M. Koohpeyma 1
M.R. Sheykholeslami 1
M.R. Ghasemi 2
1 Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran. Tectonic Group, Geological Survey of Iran, Tehran, Iran.
2 Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran.
10.22071/gsj.2010.57339
Abstract
The metamorphic rocks around Mashhad city were suffered by several stages of metamorphism and deformation. Special mineral and structural elements were formed in these stages. Metamorphic grade in the pellitic rocks changes from green schist to amphibole facies. Foliations generally are steep toward northeast. Lineations predominantly have gentel to moderate plunge (less than 30°) toward northwest. Kinematic analysis of ductile structures in outcrop and microscopic scale shows dextral strike slip shearing with reverse component from northwest to southeast in shear zones. Contrasting of kinematic analysis of mesoscopic folds coeval deformation with shear sense obtained from ductile shear zones indicates the strain partitioning in the area. Based on field analysis and microscopic studies, the rocks were deformed by two stages of ductile deformation and followed by brittle-ductile and brittle deformation in later stages. The first and second stages of deformation occurred in a progressive and continuous manner accompanied by the higher grade of metamorphism in the area. The main stage of metamorphism is contemporaneous with early Cimmerian orogenic phase.
Keywords
Foliation
Lineation
Ductile deformation
Shear zone
Strain partitioning
References
Alavi, M., 1979- The virani ophiolitic complex and surrounding rocks: Geologische Rundschau., 68, p.25-52.
Alavi, M., 1991- Sedimentary and structural charactristic of paleotethys remanants in northeastern Iran: Geol. Soc. Amer. Bull., 103, p.983-992.
Alavi, M., 1992-Thrust tectonics of  the Binalud region, NE Iran: Tectonics., v.2, p 360-370
Hassanipak, A. A., Ghazi, A. M., Mobasher, K., Tucker, P. J. & Duncan, R. A., 2002- 40Ar – 39Ar Geochronology and Geochemistry of the  Paleo- Tethyan Mashhad ophiolite, NE Iran
Karimpour, M. H., Farmer, L., Ashouri, C. & Saadat, S., 2006- Major, Trace and REE geochemistry of Paleo- Tethys Collision- Related Granitoids from Mashhad, Iran. Jur of Sci, Is. Rep of Iran.v.17, N.2, pp. 127-145.
Madjidi, B.,1978- Etude petrostructural de la region de Mashhad(Iran), Les problems de metamorphites, serpentinites et granitoides Hercynians: these Universite Scientifique et Medicale de Grenoble, France, 277p.
Ramsay, J. G. & Huber, M. I., 1987- The techniques of mothern structural geology, v.2, Fold and fractures: London. Academic press.