The effect of Dauphiné twinning on plastic strain in quartz

Menegon, Luca; Piazolo, Sandra; Pennacchioni, Giorgio

doi:10.1007/s00410-010-0554-7

Cited by 76 publications

(72 citation statements)

References 45 publications

(89 reference statements)

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“…centre of the pole figure) from the host-grain orientation (e.g. Van Daalen et al, 1999;Menegon et al, 2011). This is confirmed by the boundary trace analysis (Prior et al, 2002;Menegon et al, 2010) of the two main sets of straight low-angle boundaries defining localized extinction bands (parallel to bands of recrystallized grains), one running ENE-WSW (subset 1) and one running ca.…”

Section: Quartz In the Host Rockmentioning

confidence: 66%

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Molli

Menegon

Malasoma³

2017

Solid Earth

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Abstract. The switching in deformation mode (from distributed to localized) and mechanisms (viscous versus frictional) represent a relevant issue in the frame of crustal deformation, being also connected with the concept of the brittle-"ductile" transition and seismogenesis. In a subduction environment, switching in deformation mode and mechanisms and scale of localization may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). However, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in some cases for the localization of deformation and shear zone development, thus representing a case in which switching deformation mechanisms and scale and style of localization (deformation mode) interact and relate to each other. This contribution analyses an example of a millimetrescale shear zone localized by brittle precursor formed within a host granitic protomylonite. The studied structures, developed in ambient pressure-temperature (P -T ) conditions of low-grade blueschist facies (temperature T of ca. 300 • C and pressure P ≥ 0.70 GPa) during involvement of Corsican continental crust in the Alpine subduction. We used a multidisciplinary approach by combining detailed microstructural and petrographic analyses, crystallographic preferred orientation by electron backscatter diffraction (EBSD), and palaeopiezometric studies on a selected sample to support an evolutionary model and deformation path for subducted continental crust. We infer that the studied structures, possibly formed by transient instability associated with fluctuations of pore fluid pressure and episodic strain rate variations, may be considered as a small-scale example of fault behaviour associated with a cycle of interseismic creep and coseismic rupture or a new analogue for episodic tremors and slow-slip structures. Our case study represents, therefore, a fossil example of association of fault structures related to stick-slip strain accommodation during subduction of continental crust.

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Section: Quartz In the Host Rockmentioning

confidence: 66%

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Molli

Menegon

Malasoma³

2017

Solid Earth

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“…λ − σ diagrams (Cox, 2010) illustrate the transient evolution of fluid overpressure. minology after Menegon et al, 2011). The pole figures in Fig.…”

Section: Strain Accommodation History Within the Different Domainsmentioning

confidence: 94%

“…Furthermore, the anisotropy of the elastic properties of quartz may also have contributed to promoting preferential failure along specific crystallographic planes (Menegon et al, 2011;McSkimin et al, 1965). This is suggested by Domain 3 (small square in Fig.…”

Section: Strain Accommodation History Within the Different Domainsmentioning

confidence: 98%

“…The weakest crystallographic plane in quartz is the positive rhomb, both in terms of surface energy and elastic properties (Menegon et al, 2011). Van Daalen et al (1999) report what they refer to as "micro shear zones", that is, bands of new grains along the positive and negative rhomb planes.…”

Section: Strain Accommodation History Within the Different Domainsmentioning

confidence: 99%

“…These microstructures tend to develop during the very early stages of viscous deformation in quartz and are thus studied to better understand strain localization under very low-grade metamorphic conditions. Four mechanisms have been proposed to explain their occurrence: (1) progressive subgrain rotation recrystallization with subsequent grain boundary sliding (Bestmann and Prior, 2003), (2) intrapore growth by dissolution precipitation (e.g., den Brok and Spiers, 1991;Hippertt and Egydio-Silva, 1996), (3) fracturing along specific crystallographic planes with subsequent fragment rotation (e.g., den Brok, 1992;van Daalen et al, 1999;Vernooij et al, 2006b), and (4) localized recrystallization along Dauphiné twins (Stipp and Kunze, 2008;Menegon et al, 2011). Van Daalen et al (1999) observed that bands of new grains tend to develop preferentially along the rhomb direction within the deforming crystal.…”

Section: Introductionmentioning

confidence: 99%

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Brittle–viscous deformation of vein quartz under fluid-rich lower greenschist facies conditions

et al. 2015

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Abstract.We studied by Electron BackScatter Diffraction (EBSD) and optical microscopy a coarse-grained (ca. 0.5-6 mm) quartz vein embedded in a phyllonitic matrix to gain insights into the recrystallization mechanisms and the processes of strain localization in quartz deformed under lower greenschist facies conditions, broadly coincident with the brittle-viscous transition. The vein deformed during faulting along a phyllonitic thrust of Caledonian age within the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The phyllonite hosting the vein formed at the expense of a metabasaltic protolith through feldspar breakdown to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the quartz vein acted as a relatively rigid body. Viscous deformation in the vein was initially accommodated by quartz basal slip. Under the prevailing deformation conditions, however, dislocation glide-and possibly creep-accommodated deformation of quartz was inefficient, and this resulted in localized strain hardening. In response to the (1) hardening, (2) progressive and cyclic increase of the fluid pressure, and (3) increasing competence contrast between the vein and the weakly foliated host phyllonite, vein quartz crystals began to deform by brittle processes along specific, suitably oriented lattice planes, creating microgouges along microfractures. Nucleated new grains rapidly sealed these fractures as fluids penetrated the actively deforming system. The grains grew initially by solution precipitation and later by grain boundary migration. We suggest that the different initial orientation of the vein crystals led to strain accommodation by different mechanisms in the individual crystals, generating remarkably different microstructures. Crystals suitably oriented for basal slip, for example, accommodated strain mainly viscously and experienced only minor fracturing. Instead, crystals misoriented for basal slip hardened and deformed predominantly by domainal fracturing. This study indicates the importance of considering shear zones as dynamic systems wherein the activated deformation mechanisms may vary through time in response to the complex temporal and spatial evolution of the shear zone, often in a cyclic fashion.

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The recrystallized grain size piezometer for quartz: An EBSD‐based calibration

Cross

Prior

Stipp

et al. 2017

Geophysical Research Letters

129

154

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We have reanalyzed samples previously used for a quartz recrystallized grain size paleopiezometer, using electron backscatter diffraction (EBSD). Recrystallized and relict grains are separated using their grain orientation spread, which acts as a measure of intragranular lattice distortion and a proxy for dislocation density. For EBSD maps made with a 1 μm step size, the piezometer relationship is D = 103.91 ± 0.41 ∙ σ−1.41 ± 0.21 (for root‐mean‐square mean diameter values). We also present a “sliding resolution” piezometer relationship, D = 104.22 ± 0.51 ∙ σ−1.59 ± 0.26, that combines 1 μm step size data at coarser grain sizes with 200 nm step size data at finer grain sizes. The sliding resolution piezometer more accurately estimates stress in fine‐grained (<10 μm) samples. The two calibrations give results within 10% of each other for recrystallized grain sizes between 10 μm and 100 μm. Both piezometers match the original light optical microscopy quartz piezometer within error.

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The effect of Dauphiné twinning on plastic strain in quartz

Cited by 76 publications

References 45 publications

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Brittle–viscous deformation of vein quartz under fluid-rich lower greenschist facies conditions

The recrystallized grain size piezometer for quartz: An EBSD‐based calibration

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