- Open Access
Growth of plastic shear zone and its duration inferred from theoretical consideration and observation of an ancient shear zone in the granitic crust
Earth, Planets and Space volume 54, pages1207–1210(2002)
A new model for growth of plastic shear zone is proposed based on the basis of a theory of fluid dynamics coupled with a rheological constitutive function, and is applied to a natural shear zone. Mylonite, ultramylonite and other ductile fault rocks are well known to deform in a plastic flow regime. The rheological behavior of these kinds of rocks has been well documented as a non-linear viscous body, which is empirically described as , where : strain rate, τ: shear stress, Q: activation energy, R: universal gas constant, T: absolute temperature, and A and n are constants. Strain rate- and temperature-dependent viscosity is obtained by differentiating the equation, and simplified by substituting n = 1. Then, substitution of the equation into a diffusion equation, , derives an equation δ = 4[t/p · A exp(−Q/RT)]1/2, where δ: thickness of active layer of viscous deformation, ν: kinematic viscosity, and ρ: density. The duration of creep deformation along the ancient plastic shear zone (thickness: 0.076 m) is estimated to be around 760 s, in a temperature range from 300 to 500°C. This estimation is rather good agreement with intermittent creep during inter-seismic period, than steady state creep or co-seismic slip.
Beach, A., Retrogressive metamorphic processes in shear zones with special reference to the Lewisian complex, Jour. Str. Geol, 8, 257–263, 1985.
Carter, N. C., D. A. Anderson, F. D. Hansen, and R. L. Kranz, Creep and creep rupture of granitic rocks, Am. Geophys. Un. Monogr, 24, 61–82, 1981.
Christie, J. M., P. S. Koch, and R. P. George, Flow law of quartzite in the alpha quartz field, EOS, Trans. Am. Geophys. Un, 60, 948, 1979.
Fujimoto, K., T. Ohtani, N. Shigematsu, Y. Miyashita, T. Tomita, H. Tanaka, K. Omura, and Y. Kobayashi, Water-rock interaction observed in the brittle-plastic transition zone, Earth Planets Space, 54, this issue, 1127–1132, 2002.
Harris, L. B. and P. R. Cobbold, Development of conjugate shear bands during bulk simple shearing, Jour. Str. Geol, 7, 37–44, 1984.
Heard, H. C., Steady state flow in polycrystalline halite at pressures of 2 kilobars, Am. Geophys. Un. Monogr, 16, 191–210, 1972.
Hobbs, B. E., A. Ord, and C. Teyssier, Earthquake in the ductile regime?, Pure. Appl. Geophys., 124, 309–336, 1986.
Mitra, G., Ductile deformation zones and mylonites, Am. Jour. Sci., 278, 1057–1084, 1978.
Poirier, J. P., Shear localization and shear instability in materials in the ductile field, Jour. Str. Geol, 2, 135–142, 1980.
Prandtl, L., Über flüssigkeitsbewegung bei sehr kleiner reibung, in Verhandlungen des dritten internationalen Mathematiker-Kongresses, Heidelberg, Germany, 1904 (in German).
Ramsay, J. G. and R. H. Graham, Strain variation in shear belts, Can. Jour. Earth Sci., 7, 786–813, 1970.
Ramsay, J. G. and M. I. Hubert, The Techniques of Modern Structural Geology, Vol. 1, Strain Analysis, Academic Press, London, 1977.
Shelton, G., Experimental deformation of single phase and polyphase crystal rocks at high pressure and temperature, Ph.D. Dissertation, Brown University, 1981.
Shigematsu, N. and H. Tanaka, Dislocation creep of fine grained recrystallized plagioclase under low temperature conditions, Jour. Str. Geol., 22, 65–79, 2000.
Simpson, C. and S. M. Schmid, Microstructural indicators of sense of shear in shear zones, Geol. Soc. Am. Bull., 94, 1281–1288, 1983.
About this article
Cite this article
Tanaka, H., Shibazaki, B., Shigematsu, N. et al. Growth of plastic shear zone and its duration inferred from theoretical consideration and observation of an ancient shear zone in the granitic crust. Earth Planet Sp 54, 1207–1210 (2002). https://doi.org/10.1186/BF03353321
- Shear Zone
- Creep Deformation
- Steady State Creep
- Plastic Regime
- Viscous Deformation