The observation of dislocations in mica

Silk, E. C. H.; Barnes, R.S.

doi:10.1016/0001-6160(61)90158-4

Cited by 27 publications

(5 citation statements)

References 5 publications

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“…These directions have since been confumed, both by external rotations measured in experimentally kinked biotite [Borg and Handin, 1966;Etheridge eta/., 1973] and by TEM of muscovite, biotite, and lepidolite [Silk and Barnes, 1961;Amelinclcx and Delavignette, 1962;Demny, 1963a,b;Meike, 1989]. Denmy [1963] [Meike, 1989].…”

Section: Previous Identifications Of Slip Systemsmentioning

confidence: 99%

“…Microstructures of the deformed samples were examined optically in thin sections prepared parallel to the compression axis and perpendicular to cleavage while dislocations in the basal phme were imaged by transmission electron microscopy TEM in thin plates prepared by cleavage [Silk and Barnes, 1961]. Electron beam damage at an accelerating voltage of 120 KV (using a Philips 400T) was rapid at room temperature and a cryogenic specimen holder (eapab!e of cooling to 100 K) was necessary to slow damage rates.…”

Section: Optical and Transmission Electron Microscopymentioning

confidence: 99%

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Basal slip and mechanical anisotropy of biotite

Kronenberg¹,

Kirby²,

Pinkston³

1990

J. Geophys. Res.

270

163

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The basal slip systems of biotite and their mechanical expressions have been investigated by shortening single crystals oriented to maximize and minimize shear stresses on (001). Samples loaded at 45 ø to (001) exhibit gentle external rotations associated with dislocation glide. High-angle kink bands in these samples, unlike those developed in micas loaded parallel to (001), are limited to sample comers. Samples shortened pertxmdicular to (001) show no evidence of nonbasal slip and fail by fracture over all conditions tested. The mechanical respome of biotite shortened at 45 ø to (001) is nearly perfectly elastic-plastic; stress-strain curves are characterized by a ste• elastic slope, a sharply deemed yield point, and continued deformation at low (mostly < 100 MPa), relatively constant stresses at strains >1%. Stresses measured beyond the yield point are insensitive to conf'ming pressure over the range 200 to 500 MPa and exhibit weak dependencies upon strain.. rare and ten3•a•e. Assuming an exponential relationship between differential stress c•a and strain rate oe of the form oe = C exp (otC•d) exp (-Q/RT), the data collected over strain rates and temperatures of 10-7 to 10-4 s-1 and 20 ø to 400øC, respectively, are best fit by an exponential constant ct of 0.41 q' 0.08 MPa-1 and an activation energy Q of 82 + 13 lcJ/mol. A power law fits the dam equally well with n = 18 + 4 and Q = 51 q' 9 kJ/mol. Samples oriented favorably for slip in directions [100] and [110] are measurably weaker than those shortened at 45 ø to [010] and [310], consistent with the reported Burg?rs vectors <100>, 1/2 <110>, and 1/2 <110>. The anisotropy of biotite is further revealed by contrastang these plastic strengths with results of samples deformed parallel and perpendicular to (001). Previous studies have shown that biotite loaded in the (001) plane is strong prior to the nucleation of kink bands.The strength of biotite shortened perpendicular to (001) exceeds that measured parallel to (001) and is pressure dependent. Application of the results to deformation within the continental crust suggests that biotite oriented favorably for slip is much weaker than most other silicates over a wide range of geologic conditions. Its presence within foliated rocks and shear zones may limit locally the stresses that can be supported. INTRODUCtiON Layer ,s_ilicares are weak and evidence of their deformation in •he Earths crust is widespread. The d6collements of major ttu•t sheets are commonly defined by clay-bearing shales and slams [e.g., Hayes, 1891; Rodgers, 1949; King, 1950; Chapple, 1978] and localized shear strains of mylonites and ductile shear zones are frequently associated with the presence of micas [e.g., Bell and Etheridge, 1973; Hobbs et al., 1976; White et al., 1980; Wilson, 1980; Tullis et al., 1982]. On a f'm•r scale, micas within metamorphic tectonites exhibit sharp deformation and kink bands [Hobbs et al., 1976; Wilson and Be!l, 1979; Baronnet and Olives, 1983; Vernon et al., 1983; Goodwin and Wenk, 1990], strong crystallographic ...

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Section: Previous Identifications Of Slip Systemsmentioning

confidence: 99%

Section: Optical and Transmission Electron Microscopymentioning

confidence: 99%

Basal slip and mechanical anisotropy of biotite

Kronenberg¹,

Kirby²,

Pinkston³

1990

J. Geophys. Res.

270

163

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“…In the trioctahedral mica case, Takeuchi & Haga (1971) worked out a theory of geometrical interest based upon periodic slips localized in the octahedral sheet of the mica structure. The physical significance of this slip mechanism seems rather hazardous since glide occurs much more easily in the interlayer region as shown by detailed studies of perfect (Cartz & Tooper, 1965;Silk & Barnes, 1961;Willaime & Authier, 1966) and partial (Caslavsky, 1969) dislocations in micas by electron microscopy and X-ray topography. Furthermore, attempts to transform biotite polytypes by annealing (Takeuchi & Haga, 1971) remain unsuccessful.…”

Section: Hi Discussionmentioning

confidence: 99%

Growth spirals and complex polytypism in micas. I. Polytypic structure generation

Baronnet¹

1975

Acta Cryst Sect A

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The possible polytypic structures of a mica monocrystal are generated, using a single screw dislocation emerging on both (001) faces. The discussion takes into account: (1) each basic structure the crystallite may have during its previous layer-by-layer growth, (2) the number and position of the elementary layers of the crystal when the spiral becomes active, (3) the Burgers vector strength of the dislocation. Deduced new polytypic structures, belonging to different structural series, are described and their positions with respect to the different basic structures are discussed. Some well-known growth features in micas such as 'epitaxic overgrowths' and 'macroscopic' twinning may, in some cases, be connected with a spiral growth mechanism. The layer-stacking sequences of complex polytypic structures of natural and synthetic micas reported thus far in the literature can be compared with the predictions of the screw dislocation theory of polytypism on perfect or more or less faulted basic structures. 345

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“…Important information on the M1 --~ M2 layer transformation is obtained by considering the mechanical strength and the occurrence of slips in the micas. Notwithstanding the wide-ranging literature on edge dislocations in micas which started with Silk and Barnes (1960) Caslavsky and Vedam, 1970;Etheridge et al, 1973;Bafios et al, 1983;Kronenberg et al, 1990 (Christoffersen and Kronenberg, 1993). Bell and Wilson (1977, 1981), Wilson and Bell (1979), and Noe and Veblen (1999) The biotite studied by Bell and Wilson (1977, 1981) and Wilson and Bell (1979) was more susceptible to deformation than coexisting muscovite, but contained a low concentration of E In contrast, the biotite investigated by Kronenberg et al (1990) and Mares and Kronenberg (1993) was stronger than muscovite, but was F-rich.…”

Section: Polytype Formation and Mechanical Strength: Crystallographicmentioning

confidence: 99%

Perturbative Theory of Mica Polytypism. Role of the M2 Layer in the Formation of Inhomogeneous Polytypes

Nespolo

2001

Clays and clay miner.

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Abstract--A new model is proposed to explain, within the framework of the theory of spiral growth of Frank, the formation on inhomogeneous mica polytypes. This model relates the interaction and cooperative growth of two components (spirals and/or crystals) to produce a new stacking sequence. Depending on the relative orientation between the two components, a mismatch of the interlayer positions occurs, which is compensated through either a growth defect or a crystallographic slip at the octahedral (O) sheet. Both these adjustments transform the M1 layer into the M2 layer. These two types of layers have the same chemical composition but differ in cation distribution in the O sheet. The coalescence and cooperative growth of crystals occurs in fluid-rich environments and is most frequent in druses and volcanic fumaroles. These environments favor the inhomogeneous polytypes, especially those with complex stacking sequences. In addition, the M1 -~ M2 transformation is most probable in micas with an oxybiotitic composition, where the removal of the OH dipole strengthens the interlayer bonding and the presence of high-charge cations destabilizes the O sheet. Three examples of inhomogeneous polytypes of titaniferous oxybiotite from Ruiz Peak (a volcanic environment where many inhomogeneous polytypes have been reported) are presented.

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The observation of dislocations in mica

Cited by 27 publications

References 5 publications

Basal slip and mechanical anisotropy of biotite

Basal slip and mechanical anisotropy of biotite

Growth spirals and complex polytypism in micas. I. Polytypic structure generation

Perturbative Theory of Mica Polytypism. Role of the M2 Layer in the Formation of Inhomogeneous Polytypes

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