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Mineralogical Characteristics of Garnet in Garnet Mica Schist and Its Tectonic Significance in the Tongbai Section of the Shangdan Fault Zone

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ABSTRACT
Studies on the metamorphism and deformation conditions of rocks in the suture zone are good ways to discuss the orogenic process and mechanism. The microstructure and ultramicrostructure features of minerals are true embodiment of formation environment of the orogenic belt. Based on the study of microstructure, ultramicrostructure deformation characteristic and compositional zonation of garnets in garnets-mica schists in the Tongbai mountain, east section of the Shangdan fault zone, the results show that the three types of garnets have suffered various states of plastic deformation. The dynamic recrystallization of garnets is due to the subgrain growth and boundary migration. The dislocations are mainly free dislocation and dislocation walls. The free dislocation density ρ = 6.14 × 108/cm2, and dislocation movement are mainly slips; slip planes are 1/2 <111> {110} and <100> {001}. Garnet microprobe analysis shows that it belongs to almandine, and reflects it has undergone epidote-amphibolite to amphibolite facies metamorphism. Compositional zonation of garnet shows that the rocks had experienced progressive metamorphism. First metamorphic environment was continuous temperature-pressure and in mid-term there were two non-synchronous transient cooling and decompression processes, and it finally underwent decompression and warming process of the thermal relaxation environment. The formation condition of garnet-mica schist is estimated: T = 562°C - 617°C, and P = 0.77 - 1.02 GPa. The differential stress is 0.511 GPa and strain rate is 4.97536 × 10-10 m/s. After systemic analysis, a conclusion is drawn that the plastic deformation mode, deformation mechanism and formation environment of garnets are closely related to the formation and development of the Shangdan fault zone. It truly reflects that the Shangdan fault zone, as the suture zone of Yangtze and north China plate, has been subjected to early medium-grade metamorphism. With the continuous compression after the collision, the left-lateral shearing happened and caused the formation of high density dislocations and subgrains of the garnets; finally the plastic deformation happened and the bulging recrystallization formed in the period of heat relaxation had a relative low stress.
 
Cite this paper
Ren, S. , Song, C. and Li, J. (2015) Mineralogical Characteristics of Garnet in Garnet Mica Schist and Its Tectonic Significance in the Tongbai Section of the Shangdan Fault Zone. Open Journal of Geology, 5, 13-27. doi: 10.4236/ojg.2015.51002.
 
References
[1]Zhang, G.W. and Liu, X.M. (1998) Some Remarks on China Central Orogenic System. Earth Science, 23, 443-448. (In Chinese with English Abstract)
 
[2]Song, C.Z., Zhang, G.W., Ren, S.L., Li, J.H. and Huang, W.C. (2009) The Research on Deformation Features of Some Structural Zones in the Qinling-Dabieshan Orogenic Belt. Journal of Northwest University (Natural Science Edition) 39, 368-380. (In Chinese with English Abstract)
 
[3]Liu, X.C., Lou, Y.X. and Dong, S.W. (2005) P-T-t Path of Low-Temperature Eclogites from the Tongbaishan Area. Acta Petrologica Sinica, 021, 1081-1093. (In Chinese with English Abstract)
 
[4]Huang, S.Y. and Xu, B. (2006) Geometry, Kinematics and Evolution of the Tongbai Orogenic Belt. Earth Science Frontiers (D Series), 36, 242-251. (In Chinese with English Abstract)
 
[5]Wei, C.J., Wu, Y.X., Ni, Y.Y., Chen, B. and Wang, S.G. (1999) The Characteristics of Eclogite and Its Geological Significance in Tongbai Area in Henan Province. Chinese Science, 44, 1882-1885. (In Chinese with English Abstract)
 
[6]Bell, T.H. and Johnson, S.E. (1995) Porphyroblast Inclusion Trails: The Key to Orogenesis. Journal of Metamorphic Geology, 7, 279-310. http://dx.doi.org/10.1111/j.1525-1314.1989.tb00598.x
 
[7]Bell, T.H. and Forde, A. (1995) On the Significance of Foliation Patterns Preserved around Folds by Mineral Overgrowth. Tectonohysics, 246, 171-181. http://dx.doi.org/10.1016/0040-1951(94)00263-9
 
[8]Williams, M.L. (1994) Sigmoidal Inclusion Trails, Punctuated Fabric Development, and Interactions between Metamorphism and Deformation. Journal of Metamorphic Geology, 12, 1-21.
http://dx.doi.org/10.1111/j.1525-1314.1994.tb00001.x
 
[9]He, T.X. (1980) Metamorphic Petrology. Geological Publishing House, Beijing, 60-65. (In Chinese with English Abstract)
 
[10]Clarke, G.L., Aitchison, J.C. and Cluzel, D. (1997) Eclogites and Blueschists of Pam Penisula, NE New Caledonia: Are Appraisal. Journal of Petrology, 38, 843-876. http://dx.doi.org/10.1093/petroj/38.7.843
 
[11]Spear, F.S. and Daniel, C.G. (2001) Diffusion Control of Garnet Growth, Harpswell Neck, Maine, USA. Journal of Metamorphic Geology, 19, 179-195. http://dx.doi.org/10.1046/j.0263-4929.2000.00306.x
 
[12]Cygan, R.T. and Lasaga, A.G. (1985) Self-Diffusion of Magnesium in Garnet at 750 to 900?C. Science, 285, 328-350.
 
[13]Menzer, G. (1928) Die kristallstrktur der Granate. Zeitschrift für Kristallographie, 69, 300-396.
 
[14]O’neill, B., Bass, J.D., Smyth, J.R. and Vaughan, M.T. (1989) Elasticity of Grossular-Pyrope-Almandine Garnet. Journal of Geophysical Research, 94, 17819-17824. http://dx.doi.org/10.1029/JB094iB12p17819
 
[15]Chen, N.S. and Sun, M. (2003) Major- and Trace-Element Zoning in Metamorphic Garnets and Their Metamorphic Process Implications. Earth Science Frontiers, 10, 315-320. (In Chinese with English Abstract)
 
[16]Ji, S.C. and Martignole, J. (1997) Fracturing of Garnet Crystals in Anisotropic Metamorphic Rocks during Uplift. Journal of Structure Geology, 19, 603-620. http://dx.doi.org/10.1016/S0191-8141(97)00006-0
 
[17]Nicolas, A. and Poirier, J.P. (1976) Crystalline Plasticity and Solid State Flow in Metamorphic Rocks. John Wiley & Sons, New York.
 
[18]Voegele, V., Ando, J.I. and Cordier, P. (1998) Plastic Deformation of Silicate Garnets I High-Pressure Experiments. Physics of the Earth and Planetary Interiors, 108, 305-318.
http://dx.doi.org/10.1016/S0031-9201(98)00110-1
 
[19]Wang, Y.F. and Jin, Z.M. (2001) Diffusion Creep of Rocks and Its Implications. Geological Science and Technology Information, 20, 5-10. (In Chinese with English Abstract)
 
[20]Brok, B.D. and Kruhl, J.H. (1996) Ductility of Garnet as an Indicator of Extremely High Temperature Deformation: Discussion. Journal of Structural Geology, 18, 1369-1373. http://dx.doi.org/10.1016/S0191-8141(96)00064-8
 
[21]Prior, D.J., Wheeler, J. and Brndnker, F.E. (2000) Crystal Plasticity of Natural Garnet: New Microstructures Evidence. Geology, 28, 1003-1006.
http://dx.doi.org/10.1130/0091-7613(2000)28<1003:CPONGN>2.0.CO;2
 
[22]Ren, S.L., Song, C.Z., Lin, S.F., Zhang, H.R., Li, J.H., Tu, W.C., Zhang, H. and Zhang, J.J. (2011) Mineralogy Feature and Tectonic Significance of Garnet from Garnet-Mica Schist at the West Section of Xinyang-Shucheng Fault Belt. Chinese Journal of Geology, 46, 350-363. (In Chinese with English Abstract)
 
[23]Massonne, H.J. and Szpurka, Z. (1997) Thermodynamic Properties of White Micas on the Basis of High-Pressure Experiments in the Systems K2O-MgO-Al2O3-H2O and K2O-FeO-Al2O3-SiO2-H2O. Lithos, 41, 229-250. http://dx.doi.org/10.1016/S0024-4937(97)82014-2
 
[24]Chen, Y., Wei, C.J., Zhang, J.S. and Chu, H. (2005) Phase Equilibria of Mica-Schists and Gneisses in the HP-UHP Belt of Southern Dabie Shan. Acta Petrologica Sinica, 21, 1657-1668. (In Chinese with English Abstract)
 
[25]Zheng, Y.D. and Chang, Z.Z. (1985) Finite Strain Measurement and Ductile Shear Zones. Geological Publishing House, Beijing, 188. (In Chinese with English Abstract)                                                   eww150127lx
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