Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature

Fukuda, Jun; Raimbourg, Hugues; Shimizu, Ichiko; Neufeld, Kai; Stünitz, Holger

doi:10.5194/se-10-621-2019

Cited by 7 publications

(52 citation statements)

References 68 publications

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“…Using temperatures of 650°C–750°C and pressures of 0.7–0.75 GPa for steady‐state deformation in the Nusfjord mylonitized pseudotachylytes (Menegon et al, ), and water fugacities calculated for these conditions (Tödheide, ), the minimum period necessary for transformation from the fine‐grained recrystallized quartz to the foam texture ranges from 1–100 years, inversely proportional to temperature (Figure c). The grain growth parameters of Wightman et al, are somewhat pressure dependent, but those of Fukuda et al () are not, excepting the input of water fugacity. Although the more recent work of Fukuda et al suggested that the temperature dependence of the Wightman et al () grain growth parameters might be overestimated, the timescales estimated by both methods are very similar under the Nusfjord deformation conditions.…”

Section: Discussionmentioning

confidence: 93%

“…Also shown is the dry dislocation creep flow law for an anorthite‐diopside aggregate (grey curve; Dimanov & Dresen, ) to represent the hypothetical viscous deformation of the bulk anorthosite. The inset magnifies the mixed flow laws at low flow stress; (b) microstructures observed in quartz in mylonitized pseudotachylytes in Nusfjord related to relaxation of stress and strain rates over time after some perturbation, for example, seismic slip; and (c) static grain growth of quartz from an initial grain size of 6.5 μm modeled for Nusfjord deformation temperatures and pressures using the quartz grain growth parameters of Wightman et al () and Fukuda et al ().…”

Section: Discussionmentioning

confidence: 99%

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Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Campbell

Menegon

2019

JGR Solid Earth

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Understanding the ability of the lower crust to support transient changes in stresses and strain rates during the earthquake cycle requires a detailed investigation of the deformation mechanisms and rheology of deep crustal fault rocks. Here, we show that lower crustal pseudotachylyte-bearing shear zones are able to accommodate short-term episodes of high strain rate and high stress deformation by accelerated viscous creep, followed by a reduction in stresses to some ambient deformation condition. Quartz microstructure within pseudotachylyte-bearing shear zones in otherwise undeformed granulites from Lofoten, Norway, indicates that dynamic recrystallization occurred during viscous creep under rapid strain rates and high stresses of~10 −9 s −1 and~100 MPa, respectively. Lower stress microstructures (i.e., foam textures) are also recorded in the shear zones, indicating spatial and temporal variations of stress and strain rate during deformation cycles. Both the high and lower stress quartz recrystallization took place under granulite facies conditions of 650°C-750°C and 0.7-0.8 GPa and represented a record of highly localized viscous creep within the lower crust. This implies that lower crustal pseudotachylytes are potentially able to form extremely localized weak zones within strong lower crust, enabling a deep mechanical response to perturbations in stress and strain rate such as those experienced during the seismic cycle, for example, seismogenic loading followed by subsequent postseismic relaxation.Plain Language Summary Detailed investigation of the strength and deformation style of fault rocks sourced from the Earth's lower crust is important to understand how the lower crust reacts to shortterm variations in stress and strain rate, which can occur, for example, between earthquakes. Here, we show that solidified pseudotachylytes (initially melts produced due to frictional heating along the fault plane during an earthquake) occurring at depths of 25-30 km in the lower crust can accommodate deformation at particularly high strain rates and high stresses via solid-state creep. We look at pseudotachylytes formed in lower crustal shear zones that are now exhumed in Lofoten, Norway. Deformation microstructures in quartz within these pseudotachylytes have recorded rapid strain rates and high stresses. These microstructures are occasionally transformed into lower stress versions, indicating that during the deformation the stress and strain rate varied through both time and space. Both stages, however, record the same deformation temperatures and pressures, indicating that these are snapshots of ongoing deformation within the lower crust. We conclude that, when the lower crust is strong, pseudotachylytes will form important weak zones that accommodate deformation even during rapid variations in the deformation conditions, for example, as occurs during the postseismic period immediately after an earthquake.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Campbell

Menegon

2019

JGR Solid Earth

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“…8). However, unlike polygonal structures that result from static grain growth (e.g., Fukuda et al 2019), the actual grain shapes in dynamically recrystallized quartz rocks of the type-I and type-III are not close to cubes or tetradecahedra, and grain boundaries show curved or serrated morphologies (Takahashi et al 1998). Moreover, grain size distribution in dynamic recrystallization is close to lognormal, which means that the grains smaller than the average size are large in number (Shimizu 1998(Shimizu , 1999.…”

Section: Discussionmentioning

confidence: 99%

Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents

Fukuda

Shimizu

2019

Earth Planets Space

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We evaluated water distributions in deformed quartz in schists along the Asemi River, Central Shikoku, in the Sanbagawa Metamorphic Belt, Japan, using infrared spectroscopic (IR) mapping. The water trapped in quartz as molecular H 2 O showed a broad IR absorption band at 2800-3750 cm −1. A necessary step before assessing the quartz water content was to evaluate and compare six previously proposed IR calibrations in terms of the molar absorption coefficients of H 2 O (L/mol H 2 O cm 2). The coefficients vary from 24,100 to 89,000 L/mol H 2 O cm 2 , and the values of the coefficients show a rough increase with increasing component of structural-OH in the IR spectra. We used Paterson's calibration, which does not require input regarding the mineral species, but which was modified in his paper for measurements of molecular H 2 O in quartz. The absorption coefficient is 38,000 L/mol H 2 O cm 2. IR mapping was performed on Sanbagawa metamorphic rocks with increasing grades of metamorphism, where the mean grain size of quartz increases from ~ 40 to ~ 120 µm. The absorption bands that are only from the quartz can be distinguished on the basis of microstructural observations and the corresponding mapping results. The IR spectra of quartz commonly show dominant molecular H 2 O bands at 2800-3750 cm −1 with no additional bands associated with crystalline-OH when only quartz is measured. The water contents of quartz in all our samples were 40-310 ppm, and these values are about one-third of previously reported values measured using point analyses with the unified Paterson's calibration. This difference seems to reflect the incorporation of phyllosilicates in previous measurements that showed a broad band around 3600 cm −1. The lowest and highest water contents in our quartz samples are associated with intragranular water and grain boundary water, respectively. We estimated the grain boundary widths to be at most ~ 10 nm on the basis of the water contents at grain boundaries.

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“…addition, the high activation enthalpy determined byWightman et al (2006) leads to slower growth rates when extrapolated to crustal temperatures. As for the grain growth law determined byFukuda et al (2019), the uncertainty in Qg is relatively large. This uncertainty partly reflects that most of their 1000°C grain growth experiments show slower grain growth than 900°C experiments (seeFigure 10in Fukuda et al, 2019).…”

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confidence: 99%

“… is empirically fit in each plot. Fukuda19 and Wightman06 refers to the grain growth laws developed byFukuda et al (2019) andWightman et al (2006), respectively.…”

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Assessment of quartz grain growth and the application of the wattmeter to predict recrystallized grain sizes

Tokle¹,

Hirth²

2020

Preprint

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Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature

Cited by 7 publications

References 68 publications

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Transient High Strain Rate During Localized Viscous Creep in the Dry Lower Continental Crust (Lofoten, Norway)

Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents

Assessment of quartz grain growth and the application of the wattmeter to predict recrystallized grain sizes

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