Abstract
Pseudotachylytes from a crustal scale shear zone in Central Australia have developed in a cyclical manner: once developed, an individual pseudotachylyte is deformed in a ductile manner, only to be overprinted at a later stage by a new generation of pseudotachylytes. Such cyclic generation and deformation of pseudotachylyte has been interpreted in the past as representing conditions at the brittleductile transition; a different interpretation, however, is presented here. It is proposed that psuedotachylytes and associated ultramylonites can develop entirely within the ductile regime as ductile instabilities. Such instabilities are different in nature to those previously discussed at length in the geophysical literature but are identical in principle with the instabilities that develop for velocity-weakening frictional behavior in spring-slider systems. At a given strain rate a critical temperature,T c, is defined, at which the transient work hardening equals the product of stress relaxation due to a thermal fluctuation and the heat generated by shearing. A necessary condition for ductile instability at a given strain rate is that the temperature is belowT c; then the rate of change of stress with respect to strain is negative. An additional requirement is that this rate of change exceeds, in magnitude, the effective elastic stiffness of the loading system. Ductile instabilities are marginally possible at geological strain rates in quartzites but are possible at mid-crustal temperatures in other rock types. On the basis of these observations a new interpretation is presented for the base of the seismogenic zone in crustal regions.
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References
Argon, A. S. ‘Stability of plastic deformation’, inThe Inhomogeneity of Plastic Deformation. ASM Publication, 1973.
Backofen, W. A.,Deformation Processing. Addison Wesley, London, 1972.
Bell, T. H. andHammond, R. L. (1984),On the internal geometry of mylonite zones. J. Geol.92, 667–686.
Berthe, D., Choukroune, P. andJegouzo, P. (1979),Orthogneiss, mylonite and non coaxial deformation of granites: The example of the South-American Shear Zone. J. Struct. Geol.1, 31–42.
Bott, M. H. P.,The Interior of the Earth. Edward Arnold, 1971.
Brace, W. F. andByerlee, J. D. (1966),Stick-slip as a mechanism for earthquakes. Science153, 990–992.
Brace, W. F. andKohlstedt, D. L. (1980),Limits on lithospheric stress imposed by laboratory experiments. J. Geophys. Res.85, 6248–6252.
Brun, J. P. andCobbold, P. R. (1980),Strain heating and thermal softening in continental shear zones: A review. J. Struct Geol.,2, 149–158.
Burnham, C. W., Holloway, J. R. andDavis, N. F. (1969),Thermodynamic properties of water to 1000°C and 10,000 bars. Special Paper No. 132. Geol Soc. America.
Carter, N. L. andKirby, S. H. (1978),Transient creep and semibrittle behavior of crystalline rocks. Pure Appl. Geophys.116, 807–839.
Chen, W. P. andMolnar, P. (1983),Focal depths of intracontinental and intraplate earthquakes and their implications for the thermal and mechanical properties of the lithosphere. J. Geophys. Res.88, 4183–4214.
Chopra, P. N. andPaterson, M. S. (1981),The experimental deformation of dunite. Tectonophys.78, 453–473.
Delany, J. M. andHelgeson, H. C. (1978),Calculation of the thermodynamic consequences of dehydration in subducting oceanic crust to 100 kb and >800°C. Amer. J. Sci.278, 638–686.
Dieterich, J. H. (1978),Time-dependent friction and the mechanics of stick slip. Pure Appl. Geophys.116, 790–806.
Dieterich, J. H. (1979a),Modeling of rock friction: 1. Experimental results and constitutive equations. J. Geophys. Res.84, 2161–2168.
Dieterich, J. H. (1979b),Modeling of rock friction: 2. Simulation of preseismic slip. J. Geophys. Res.84, 2169–2175.
Dieterich, J. H., ‘Constitutive properties of faults with simulated gouge, inMechanical Behavior of Crystal Rocks, Handin Volume, N. L. Carter, M. Friedman, J. M. Logan, and D. W. Stearns (eds), 1981. Geophys. Monograph Ser.No. 24, AGU, 103–120.
Drucker, D. C. (1960),Extension of the stability postulate with emphasis on temperature changes, Proc. 2nd Symp. Naval Struct. Mech. Brown Univ., E.-H. Lee and P. S. Symonds (eds), Pergamon, 1960.
Etheridge, M. A., Wall, V. J., Cox, S. F. andVernon, R. H. (1984),High fluid pressures during regional metamorphism and deformation: Implications for mass transport and deformation mechanisms. J. Geophys. Res. (Special Issue on Chemical Effects of Water on Rock Deformation) 89, 4344–4358.
Etheridge, M. A., Wall, V. J. andVernon, R. H. (1983),The role of the fluid phase during regional metamorphism and deformation. J. Metamorph. Geol.1, 205–226.
Evans, B., andWong, T.-F., ‘Shear localization in rocks induced by tectonic deformation’ chap. 10, inMechanics of Geomaterials, Z. Bazant (ed), John Wiley, 1985, 189–210.
Fleitout, L. andFroidevaux, C. (1980),Thermal and mechanical evolution of shear zones. J. Struct. Geol.2, 159–164.
Forman, D. J. (1966),Regional geology of the south-west margin, Amadeus Basin, central Australia. Bur. Miner. Resour. Aust.Rept. 87.
Goetze, C. (1978),The mechanisms of creep in olivine. Phil. Trans. R. Soc. Lond. A22, 99–119.
Griggs, D. T. andBaker, D. W. (1969), ‘The origin of deep focus earthquakes’, inProperties of Matter under Unusual Conditions. H. Mark and S. Fernbach (eds), Interscience, 1969, p. 23–42.
Gruntfest, I. J. (1963), ‘A note on thermal feedback and the fracture of solids’, inFracture of Solids. Metallurg. Soc. Conf.20, Interscience, 189–193.
Gu, J.-C., Rice, J. R., Ruina, A. L. andTse, S. T. (1984),Slip motion and stability of a single degree of freedom elastic system with rate and state dependent friction. J. Mech. Phys. Solids32, 167–196.
Hobbs, B. E., McLaren, A. C. andPaterson, M. S. ‘Plasticity of single crystals of synthetic quartz, inFlow and Fracture of Rocks. Geophys. Monograph Ser.16 H. C. Heard et al. (eds), AGU Washington 1972, p. 29–53.
Jaoul, O., Tullis, J. A. andKronenberg, A. K. (1984),The effect of varying water contents on the creep behavior of Heavitree quartzite. J. Geophys. Res. (Special Issue on Chemical Effects of Water on Rock Deformation)89, 4298–4312.
Kirby, S. H. (1980),Tectonic stress in the lithosphere: Constraints provided by the experimental deformation of rocks. J. Geophys. Res.85, 6353–6363.
Kirby, S. H. andKronenberg, A. K. (1984),Deformation of clinopyroxenite: Evidence for a transition in flow mechanisms and semibrittle behavior. J. Geophys. Res.89, 3177–3192.
Lehner, F. K., Li, V. C. andRice, J. R. (1981),Stress diffusion along rupturing plate boundaries. J. Geophys. Res.86, 6155–6169.
Lister, G. S. andSnoke, A. W. (1984),S-C mylonites. J.Struct. Geol.6, 617–638.
Macaudiere, J. andBrown, W. L. (1982),Transcrystalline shear fracturing and pseudotachylyte generation in a meta-anorthosite (Harris, Scotland). J. Struct Geol.4, 395–406.
Maddock, R. H. (1983),Melt origin of fault generated pseudotachylytes demonstrated by textures. Geology11, 105–108.
Miyashiro, A.,Metamorphism and Metamorphic belts, Allen and Unwin, London, 1973.
Nicholson, D. W., andKiddy, K. C. (1984),A large deformation plasticity model with rate sensitivity and thermal softening, Trans. ASME106, 388–392.
Ord, A. andHobbs, B. E. (1986a),Experimental control of the water-weakening effect in quartz, Geophysical Monograph36, B. E. Hobbs and H. C. Heard (eds.) American Geophysical Union, 51–72.
Ord, A. andHobbs, B. E. (1986b),The strength of the continental crust, detachment zones and the development of plastic instabilities, submitted toTectonics.
Orowan, E. (1960),Mechanism of seismic faulting. Geol. Soc. Amer. Mem.79, 323–345.
Passchier, C. W. (1982a),Mylonitic deformation in the Saint-Barthelemy Massif, French Pyrenees, with emphasis on the genetic relationship between ultramylonite and pseudotachylyte, GUA Papers Geology, Ser. 116, 1–173.
Passchier, C. W. (1982b),Pseudotachylyte and the development of ultramylonite bands in the Saint-Barthelemy Massif, French Pyrenees J. Struct. Geol.4, 69–79.
Passchier, C. W. (1984).The generation of ductile and brittle shear bands in a low-angle mylonite zone. J. Struct. Geol.6, 273–281.
Passchier, C. W. (1984),Thigin of pseudotachylytes Amer. J. Sci.262, 1008–1035.
Poirier, J. P. (1980),Shear localization and shear instability in materials in the ductile field. J. Struct. Geol.2, 135–142.
Poirier, J. P., Bouchez, J. L. andJonas, J. J. (1979),A dynamic model for seismic ductile shear zones Earth and Planet Sci. Lett.43, 441–453.
Recht, R. F. (1964),Catastrophic thermoplastic shear, Trans. ASME 31E (J. Appl. Mech.),2, 189–193.
Rice, J. R. andGu, J.-C. (1983),Earthquake aftereffects and triggered seismic phenomena Pure Appl. Geophys.121, 187–219.
Rice, J. R. andRuina, A. L. (1983),Stability of steady frictional slipping, Trans. ASEM J. Appl. Mech.50, 343–349.
Rice, J. R. andTse, S. T. (1986),Dynamic motion of a single degree of freedom following a rate and state dependent friction law, J. Geophys. Res.91, 521–530.
Rogers, H. C. (1979),Adiabatic plastic deformation, Ann.Rev. Mat. Sci.9, 283–311.
Rubin, D. andDrucker, D. C. ‘On stability of viscoplastic systems with thermo-mechanical coupling, inContributions to Mechanics, D. Abir (ed), Pergamon, 1969, p. 171–179.
Ruina, A. L.,Friction laws and instabilities: A quasistatic analysis of some dry frictional behavior, Ph.D. Thesis, Brown Univ., 1980.
Ruina, A. L. (1983),Slip instability and state variable friction laws J. Geophys. Res.88, 10359–10370.
Rutland, R. W. R. (1976),Orogenic evolution of Australia Earth Sci. Rev.12, 161–196.
Schubert, G. andYuen, D. A. (1978),Shear heating instability in the Earth's upper mantle Tectonophys.50, 197–205.
Shelton, G. andTullis, J. (1981),Experimental flow laws for crustal rocks (Abstr.), EOS, Trans. AGU62, 396.
Shimamoto, T. andLogan, J. M. (1985),Velocity-dependent behavior of simulated halite shear zones: An analog for silicates unpub. ms. presented 1985 Ewing Symp.
Sibson, R. H. (1977).Fault rocks and fault mechanisms, J. Geol. Soc. (Lond.)133, 191–214.
Sibson, R. H. (1980),Transient discontinuities in ductile shear zones J. Struct Geol.2, 165–171.
Sibson, R. H. (1982),Fault zone models, heat flow, and the depth distribution of earthquakes in the continental crust of the United States Bull. Seismol. Soc. Am.72, 151–163.
Sibson, R. H. (1984),Roughness at the base of the seismogenic zone: Contributing factors J. Geophys. Res.89, 5791–5799.
Staker, M. R. (1981),The relation between adiabatic shear instability strain and material properties Acta Met.29, 683–689.
Stel, H. (1981),Crystal growth in cataclasites: Diagnostic microstructures and implications Tectonophys.78, 585–600.
Stel, H. (1986),The effect of cyclic operation of brittle and ductile formation on the metamorphic assemblage in cataclasites and mylonites Pure Appl. Geophys.124, 000–000.
Teyssier, C. (1985),A crustal thrust system in an intracratonic tectonic environment J. Struct Geol.7, 689–700.
Teyssier, C. andHobbs, B. E. (1985),Deformation and softening mechanisms in a major crustal fault zone, Redbank deformed zone (Central Australia) submitted to J. Struct. Geol.
Tse, S. T. andRice, J. R. (1985),Crustal earthquake instability in relation to the depth variation of frictional slip properties (unpub. ms presented 1985 Ewing Symp.).
Tullis, T. andWeeks, J. (1985),Frictional sliding of dolomite: A variation in constitutive behavior J. Geophys. Res.90, 7821–7826.
Tullis, J. A. andYund, R. A. (1985),Dynamic recrystallization of feldspar: A mechanism for ductile shear zone formation Geology13, 238–241.
Vernon, R. H.,Metamorphic Processes, Allen and Unwin, London, 1976.
Warren, R. G. (1983),Granulite and the tectonic evolution of the Arunta Block Geol. Soc. Aust. 6th Aust. Geol. Conv. Abstr. Ser.9, 59.
Weeks, J. D. andTullis, T. (1984),Frictional behavior of dolomite (Abstr), EOS, Trans. AGU65, 1077.
Weiss, L. E. andWenk, H. R. (1983),Experimentally produced pseudotachylyte-like veins in gabbro Tectonophys.96, 299–310.
Wenk, H. R. (1978),Are pseudotachylytes products of fracture or fusion? Geology6, 507–511.
Wenk, H. R. andWeiss, L. E. (1982),Al-rich calcic pyroxene in pseudotachylyte: An indicator of high pressure and high temperature? Tectonophys.84, 329–341.
Yuen, D. A. andSchubert, G. (1977),Asthenospheric shear flow: Thermally stable or unstable? Geophys. Res. Let.4, 503–506.
Zener, C. andHollomon, J. H. (1944),Effect of strain-rate upon plastic deformation of steel J. Appl. Phys.15, 22–32.
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Hobbs, B.E., Ord, A. & Teyssier, C. Earthquakes in the ductile regime?. PAGEOPH 124, 309–336 (1986). https://doi.org/10.1007/BF00875730
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DOI: https://doi.org/10.1007/BF00875730