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  • 1
    Electronic Resource
    Electronic Resource
    Coulomb constitutive laws for friction: Contrasts in frictional behavior for distributed and localized shear (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 195-214 
    Details
    ISSN: 1420-9136
    Keywords: Friction ; Coulomb failure ; constitutive laws ; localized shear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We describe slip-rate dependent friction laws based on the Coulomb failure criteria. Frictional rate dependence is attributed to a rate dependence of cohesionc and friction angle ϕ. We show that differences in the stress states developed during sliding result in different Coulomb friction laws for distributed shear within a thick gouge layer versus localized shear within a narrow shear band or between bare rock surfaces. For shear within gouge, shear strength is given by τ=c cosφ + σ n sinφ, whereas for shear between bare rock surfaces the shear strength is τ=c cosφ + σ n tanφ, where τ and σ n are shear and normal stress, respectively. In the context of rate-dependent Coulomb friction laws, these differences mean that for a given material and rate dependence of the Coulomb parameters, pervasive shear may exhibit velocity strengthening frictional behavior while localized shear exhibits velocity weakening behavior. We derive from experimental data the slip-rate dependence and evolution ofc and ϕ for distributed and localized shear. The data show a positive rate dependence for distributed shear and a negative rate dependence for localized shear, indicating that the rate dependence ofc and ϕ are not the same for distributed and localized shear, even after accounting for differences in stress state. Our analysis is consistent with the well-known association of instability with shear localization in simulated fault gouge and the observation that bare rock surfaces exhibit predominantly velocity weakening frictional behavior whereas simulated fault gouge exhibits velocity strengthening followed by a transition to velocity weakening with increasing displacement. Natural faults also exhibit displacement dependent frictional behavior and thus the results may prove useful in understanding the seismic evolution of faulting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876327
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  • 2
    Electronic Resource
    Electronic Resource
    Earthquakes in the ductile regime? (1986)
    Springer
    Pure and applied geophysics 124 (1986), S. 309-336 
    Details
    ISSN: 1420-9136
    Keywords: Earthquakes ; pseudotachylytes ; ductile instabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00875730
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  • 3
    Electronic Resource
    Electronic Resource
    Reconstruction of tectonically deformed sedimentary structures (1969)
    Springer
    International journal of earth sciences 59 (1969), S. 213-222 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract A method of reconstructing the initial shape of tectonically deformed sedimentary structures is presented. This method makes no assumptions regarding the state of strain in the rock. Examples are given in which the observed asymmetry of convolute structures is shown to be solely of tectonic origin.
    Abstract: Résumé Une méthode de réconstitution de la forme initiale des structures sédimentaires est présentée. Cette méthode n'implique aucune hypothèse concernant les déformations subies par la roche. Des exemples sont donnés selon lesquels l'asymétrie des structures de convolution est attribuable exclusivement à une cause tectonique.
    Notes: Zusammenfassung Eine Methode zur Rekonstruktion der ursprünglichen Form tektonisch deformierter Sediment-Strukturen wird dargelegt. Dabei werden keine Annahmen bezüglich des Spannungszustandes im Gestein gemacht. Beispiele sind angeführt, in denen ein rein tektonischer Ursprung der beobachteten Asymmetrie gewisser Sediment-Strukturen aufgezeigt wird.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01824952
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  • 4
    Electronic Resource
    Electronic Resource
    Dislocation structure of the deformation lamellae in synthetic quartz; a study by electron and optical microscopy (1970)
    Springer
    Contributions to mineralogy and petrology 29 (1970), S. 104-115 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Single crystals of experimentally deformed synthetic quartz showing optical deformation lamellae were examined by transmission electron microscopy. Dislocations are distributed fairly uniformly throughout the crystal. However, parallel to the trace of the deformation lamellae, which may be irrational, there are walls of tangled dislocations whose characteristics suggest that they are directly associated with the lamellae. The nature and formation of the optical image is discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392018
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  • 5
    Electronic Resource
    Electronic Resource
    Dislocations associated with optical features in naturally-deformed olivine (1971)
    Springer
    Contributions to mineralogy and petrology 30 (1971), S. 53-63 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Transmission electron microscopy has been used for the direct observation of dislocations in naturally-deformed olivine. The dislocations are arranged in arrays forming low-angle sub-boundaries which have been identified with features observed in the optical microscope. Comparison of this dislocation substructure with that observed in olivine, and in metals, experimentally deformed under various conditions, suggests that the deformation in nature has occurred by creep. Possible mechanisms of creep, involving the cooperative glide and climb of dislocations, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373368
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  • 6
    Electronic Resource
    Electronic Resource
    Experiental deformation of single crystals of biotite (1973)
    Springer
    Contributions to mineralogy and petrology 38 (1973), S. 21-36 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Single crystals of biotite have been shortened up to 20% in compression tests parallel to [100], [110] and [010] directions at 3 Kbar confining pressure and temperatures from 300 to 700° C, and at a strain rate of 10−4 sec−1. Thick metal constraining sleeves were used and led to a distribution of kinking throughout the crystals. The orientation of kink boundaries, angle of bending and asymmetry of the basal plane across the kink boundaries and the axes of bending were measured. A minor amount of unidentified non-basal slip must have occurred to account for the assymmetry, but basal slip predominates at all temperatures. From the axes of bending, the discrete slip directions [100], [110] and [110] for basal slip are deduced. Increase in temperature mainly leads to a simpler pattern of kinking associated with the kinks being wider and the kinking angle larger, presumably as a result of greater mobility of dislocation walls that form the kink boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371724
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  • 7
    Electronic Resource
    Electronic Resource
    Chemical and deformational controls on recrystallization of mica (1974)
    Springer
    Contributions to mineralogy and petrology 43 (1974), S. 111-124 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Chemical and microstructural data from one experimentally and two naturally deformed and recrystallized micas are discussed in terms of established metallurgical mechanisms for strain-induced nucleation and growth during recrystallization. It is suggested that none of these nucleation mechanisms is applicable, and that nucleation is driven by energy from both chemical and permanent strain sources. Subsequent growth of the nuclei is influenced by the deformation or by coincidence lattice relationships.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572714
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  • 8
    Electronic Resource
    Electronic Resource
    Experimentally produced preferred orientation in synthetic mica aggregates (1974)
    Springer
    Contributions to mineralogy and petrology 44 (1974), S. 275-294 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract An experimental study of the behaviour of micaceous aggregates undergoing deformation during and after mica growth has been undertaken using pelletised powder consisting of an oxide mix with the stoichiometry of phlogopite. The influences of temperature, pore fluid content, strain, strainrate, and pre-mixing time have been examined. It is concluded that oriented growth of anisotropic crystals, due either to anisotropy of pore structure and hence permeability or to pressure solution phenomena, gives rise to most of the preferred orientation observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371557
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  • 9
    Electronic Resource
    Electronic Resource
    Coarsening kinetics of the exsolution microstructure in alkali feldspar (1974)
    Springer
    Contributions to mineralogy and petrology 48 (1974), S. 45-55 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A maximum microline-low albite of 33 mole percent Or was prepared by alkali ion exchange at 1000° C and subsequently annealed in air at lower temperatures. The exsolution microstructure produced in these samples was studied by transmission electron microscopy. At or above 600° C the compositional difference of the coherent lamellae increases rapidly and reaches a maximum, corresponding to the coherent solvus, within a few days. The lamellar spacing (λ) increases more slowly and the coarsening rate is given by λ=λ0+kt 1/3; where t is annealing time, k is a constant for a given temperature, and λ0 is the lamellar spacing obtained by extrapolation to zero annealing time. λ0 is 65 Å at 600° C and ca. 200 Å at 700° C. The latter is near the maximum temperature at which exsolution is observed. The nonzero value of λ0 and its increase with increasing temperature is evidence that the exsolution occurs by a spinodal mechanism. Data for the coarsening kinetics at other temperatures should be useful for estimating the thermal history of cryptoperthites with coherent lamellae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399109
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  • 10
    Electronic Resource
    Electronic Resource
    Experimental deformation and recrystallization of a peristerite (1976)
    Springer
    Contributions to mineralogy and petrology 57 (1976), S. 49-54 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Partial syntectonic recrystallization has been produced in an experimentally deformed plagioclase (peristerite An4.5). The recrystallized grains are scattered through the strongly deformed matrix and appear to have developed by a nucleation and growth mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392851
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