Deformation at low and high stress-loading rates

Trepmann, Claudia A.; Seybold, Lina

doi:10.1016/j.gsf.2018.05.002

Cited by 27 publications

(24 citation statements)

References 69 publications

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“…seismic loading; e.g. Küster and Stöckhert, 1999;Trepmann and Stöckhert, 2003;Trepmann et al, 2017;Trepmann and Seybold, 2019). The two models are not mutually exclusive and are both equally valid to explain our observations.…”

Section: Conceptual Model Of the Fault Slip Behaviour Of Bfz045 At Thmentioning

confidence: 49%

“…Recent deformation experiments have opened up new avenues for the investigations of natural deformation microstructures in quartz-rich rocks that result from stress variations during brittle-ductile deformation. The "kick and cook" experiments, for example, have documented quartz microstructures formed during transient high stress deformation followed by stress relaxation (Trepmann et al, 2007). Deformation experiments conducted by Kidder et al (2016) show that the microstructure associated with a stress increase in quartzite is a bimodal distribution of recrystallized grain size.…”

Section: Introductionmentioning

confidence: 99%

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Fluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)

et al. 2020

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Abstract. The microstructural record of fault rocks active at the brittle–ductile transition zone (BDTZ) may retain information on the rheological parameters driving the switch in deformation mode and on the role of stress and fluid pressure in controlling different fault slip behaviours. In this study we analysed the deformation microstructures of the strike-slip fault zone BFZ045 in Olkiluoto (SW Finland), located in the site of a deep geological repository for nuclear waste. We combined microstructural analysis, electron backscatter diffraction (EBSD), and mineral chemistry data to reconstruct the variations in pressure, temperature, fluid pressure, and differential stress that mediated deformation and strain localization along BFZ045 across the BDTZ. BFZ045 exhibits a mixed ductile–brittle deformation, with a narrow (<20 cm thick) brittle fault core with cataclasites and pseudotachylytes that overprint a wider (60–100 cm thick) quartz-rich mylonite. Mylonitic deformation took place at 400–500 ∘C and 3–4 kbar, typical of the greenschist facies metamorphism at the base of the seismogenic crust. We used the recrystallized grain size piezometry for quartz to document a progressive increase in differential stress, from ca. 50 to ca. 120 MPa, towards the shear zone centre during mylonitization and strain localization. Syn-kinematic quartz veins formed along the mylonitic foliation due to transiently high pore fluid pressure (up to lithostatic value). The overprint of the veins by dynamic recrystallization and mylonitic creep is further evidence of the occurrence of brittle events under overall ductile conditions. We propose a conceptual model in which the ductile–brittle deformation cycle was controlled by transient oscillations in fluid pressure and progressively higher differential stress, possibly occurring in a narrowing shear zone deforming towards the peak strength of the crust at the BDTZ.

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Section: Conceptual Model Of the Fault Slip Behaviour Of Bfz045 At Thmentioning

confidence: 49%

Section: Introductionmentioning

confidence: 99%

Fluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)

et al. 2020

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“…In the Talea Ori, that contact has been described as thrust fault related to early nappe stacking (Chatzaras et al 2006;Xypolias et al 2007), whereas other authors observed mainly normal faults (Richter and Kopp 1983). Rocks from the contact area show microstructures indicative of transient high stresses (few hundred of MPa) within metasediments deforming by dissolution-precipitation creep at high strain rates on long term (Trepmann and Seybold 2018). Such microstructures cannot be reconciled with low stress deformation at HP-LT metamorphic conditions in subduction zones as typically recorded from HP-LT metamorphic rocks in Western Crete (Greiling 1982;Schwarz and Stöckhert 1996;Stöckhert et al 1999), but they document the early exhumation history of the HP-LT metamorphic rocks.…”

Section: Introductionmentioning

confidence: 86%

“…5a), which indicates that crystal-plastic deformation did not play a major role for accumulating the main strain at any stage. Yet, monophase quartz layers parallel to the foliation as well as younger quartz veins discordant to the foliation related to the extensional shear bands, show microfabrics that indicate deformation by dislocation creep at temperatures of at least 300-350 °C (Trepmann and Seybold 2018). This indicates firstly that the extensional shear zone at the contact between Talea Ori group and PQ s.str.…”

Section: The Extensional Shear Zonementioning

confidence: 92%

“…3, 6, 8) were interpreted by Trepmann and Seybold (2018) to have developed dominantly by crack-seal increments during flow of the metasediments at high strain rates on the order of 10 − 9 to 10 − 10 s − 1 . Although the shear zone itself is not interpreted to be seismically active, the high strain rates and the locally recorded high stress crystal-plastic deformation at few hundred of MPa are probably related to seismic stress pulses introduced by near-by seismic active faults in the overlying seismogenic zone (Trepmann and Seybold 2018). The deformation related to the shear zone, therefore is episodic with transient stages of flow at changing stress and strain rate conditions.…”

Section: The Extensional Shear Zonementioning

confidence: 99%

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A ductile extensional shear zone at the contact area between HP-LT metamorphic units in the Talea Ori, central Crete, Greece: deformation during early stages of exhumation from peak metamorphic conditions

Seybold

Trepmann

Janots

2018

Int J Earth Sci (Geol Rundsch)

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We report on an extensional ductile shear zone in central Crete at the contact area between the high-pressure low-temperature (HP-LT) metamorphic Phyllite-Quartzite unit sensu stricto (PQ s.str.) and the Talea Ori group (Plattenkalk unit). Mapping and microscopic analysis along the 20 km long contact reveal extensional shear bands, shear band cleavages (C′-type) and associated quartz veins in both units, occurring over a width of up to a kilometer. The shear offset along the shear bands is systematically perpendicular to the contact with the hanging block (PQ s.str.) being downfaulted. Abundant discordant quartz veins are associated to shear band boundaries, asymmetric boudinage and foliation boudinage, forming m-wide vein networks. These mesoscopic deformation structures together with related microstructures such as strain shadows, growth rims of albite porphyroblasts and stylolites indicate dissolution-precipitation creep as main deformation mechanism accompanied by vein formation. Temperatures during deformation are indicated to be close to peak metamorphic temperatures (≥ 300-350 °C) by the growth rims of albite porphyroblasts and micas present in the shear band cleavages, which are consistent with quartz vein microstructures showing subgrains and sutured high angle grain boundaries. Peak metamorphic temperatures inferred by the degree of graphitization of carbonaceous material are similar in the hanging wall and the footwall of the shear zone, which is consistent with fast and nearly adiabatic exhumation. Our study demonstrates the importance of ductile shear zones with high strain rate dissolution-precipitation creep and vein formation in HP-LT metamorphic rocks for the early exhumation history.

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Strength of dry and wet quartz in the low-temperature plasticity regime: insights from nanoindentation

Ceccato

Menegon

Hansen

2021

Preprint

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Experimental rock deformation has demonstrated that the strength of quartz is significantly reduced by the presence of intracrystalline H 2 O either bonded to the crystal lattice or occurring as micro-fluid inclusions, that is, quartz exhibits hydrolytic weakening (Ave Lallemant & Carter, 1971;Griggs, 1967;Griggs & Blacic, 1965;Tullis & Yund, 1980). Results from laboratory experiments established that hydrolytic weakening occurs in both synthetic and natural quartz crystals with intracrystalline H 2 O contents larger than 20-30 wt ppm (about 150 H/10 6 Si; Stünitz et al., 2017 and references therein). Several different microphysical processes have been proposed to explain hydrolytic weakening in quartz: (a) hydrolyzation of Si-O-Si bonds around dislocations, consequently decreasing the resistance to dislocation motion (i.e., reducing the Peierls stress; Griggs, 1967), (b) enhanced dislocation generation around H 2 O clusters within the crystal lattice (McLaren et al., 1989;Stünitz et al., 2017), and (c) enhanced recovery through increased ionic diffusivities and faster dislocation climb (Post et al., 1996;Tullis & Yund, 1989). Hydrolytic weakening has been experimentally observed in natural and synthetic quartz deformed at high homologous temperature, conditions for which dislocation climb and recovery processes control the overall strain rate (

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Deformation at low and high stress-loading rates

Cited by 27 publications

References 69 publications

Fluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)

Fluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)

A ductile extensional shear zone at the contact area between HP-LT metamorphic units in the Talea Ori, central Crete, Greece: deformation during early stages of exhumation from peak metamorphic conditions

Strength of dry and wet quartz in the low-temperature plasticity regime: insights from nanoindentation

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