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Michael Stipp - One of the best experts on this subject based on the ideXlab platform.
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Do local kinematics have an effect on the Recrystallized Grain Size piezometer?
2020Co-Authors: Rüdiger Kilian, Michael StippAbstract:<p><br>The quartz Recrystallized Grain Size piezometer was determined by axial shortening experiments on Black Hills quartzite in Griggs type triaxial deformation apparatus (Stipp & Tullis, 2003). The analysis of general shear experiments on Black Hills quartzite (Heilbronner & Kilian, 2017) reveal a striking discrepancy between both experimental &#160;setups; at a given differential stress, Recrystallized Grains are much larger in the general shear experiments than in axial shortening.<br>A major difference between both sets of experiments is, that the finite Grain volume of quartz in the general shear experiments almost entirely consists of Recrystallized Grains while the here investigated axial shortening experiments have fractions of Recrystallized Grains in the range of 15 to 30% in the high stress experiments and up to 60% in the low stress experiments. Quartz in the general shear experiments developed a moderate to strong crystallographic preferred orientation (CPO) while, apart from a Dauphin&#233;-induced ordering of poles to {10-11} and {01-11}, no overall significant CPO developed in the axial shortening experiments.<br>Based on the analysis of the EBSD data of Cross et al. (2017), we observed that the dispersion axes of large quartz Grains in the axial shortening experiments correspond to the global kinematic reference frame. The dispersion axes of the fraction of small, Recrystallized Grains depend on the local kinematics between the porphyroclasts. Slip transparency indicates that boundaries between the largest Grains are rather hard while Recrystallized Grains can accommodate strain induced by crystal plastic slip more effectively and homogeneously.<br>These results suggest that Recrystallized Grains in the axial shortening experiments, at least in those with low fractions of Recrystallized Grains, correspond to a material deforming at a rate higher than the imposed shortening rate while the axial load is predominantly supported by the porphyroclasts. In contrast, Recrystallized Grains in general shear experiments deform at the imposed (global) rate and derived stresses correspond on average to the deforming zone. Due to strain and strain rate inhomogeneities in the latter experiments, however, there is a systematic variation in Recrystallized Grain Size across the general shear zone. We compare these local microstructural variations and discuss their significance for the Recrystallized Grain Size piezometer calibration.</p>
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the Recrystallized Grain Size piezometer for quartz an ebsd based calibration
Geophysical Research Letters, 2017Co-Authors: A J Cross, Michael Stipp, David J Prior, Steven KidderAbstract:We have re-analyzed 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 (GOS), 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 RMS 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 Recrystallized Grain Size piezometer for quartz: An EBSD‐based calibration
Geophysical Research Letters, 2017Co-Authors: A J Cross, Michael Stipp, David J Prior, Steven KidderAbstract:We have re-analyzed 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 (GOS), 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 RMS 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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Stress measurements in the earth's crust - Recrystallized Grain Size piezometry revisited
2012Co-Authors: Michael StippAbstract:EGU2012-13016 The dynamically Recrystallized Grain Size is the most reliable paleo-piezometer to determine the differential stress in the Earth’s crust and mantle. Knowledge on the stress magnitude is enigmatic to quantify tectonic processes in orogens and plate tectonic forces in general. Owing to this significance, a considerable number of research groups has proposed different theoretical concepts of piezometers in the last couple of years. The Recrystallized Grain Size has been suggested to be not only a function of stress, but also of temperature, strain rate, strain and other parameters. In the meantime, data of experimental studies and from natural shear zones have been collected. Hence, empirical piezometer models and theoretical concepts can be confronted with these data sets. A Recrystallized Grain Size compilation of quartz mylonites from shear zones worldwide indicates that specific Grain Sizes are less frequent corresponding to transitions in the recrystallization mechanisms. This indicates that the Recrystallized Grain Size development is significantly controlled by the different recrystallization mechanisms in natural mylonites. This relationship should be constrained by any valid piezometer or dynamic recrystallization model which is, however, not the case. Most of the piezometer models assume a temperature dependence via an activation energy term. While the majority of these models predicts a decrease in Recrystallized Grain Size with increasing temperature one implies an increase with increasing temperature. However, neither a decrease nor an increase has reliably been shown by deformation experiments on different minerals. In fact, experimental data on dislocation creep of quartz do not show any temperature-dependence within the error of the given stress-Recrystallized Grain Size measurements. A strain rate dependence is – if at all – less important and also not constrained by experimental data. Also a water-dependence of the piezometer does not exist for quartz and there is contradicting experimental evidence for olivine. Experimentally deformed quartz samples display 2d- Recrystallized Grain Size distributions close to a normal distribution with a slight tendency to a positive skewness. The dispersion of the distribution does not change over the experimental range of strain (7 – 46 %) and also not with the volume proportion of Recrystallized Grains (2 – 60 %). Hence, increasing strain does not change the Recrystallized Grain Size distribution. In summary, no dependence on temperature, strain rate, strain, Grain Size distribution and water content can be observed for the quartz piezometer. There is only evidence for the dependence on the recrystallization mechanism. Therefore, it is recommended to refer to the original empirical piezometer relationship in which the Recrystallized Grain Size is only a function of the differential stress when measuring stress in the Earth’s crust.
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a new perspective on paleopiezometry dynamically Recrystallized Grain Size distributions indicate mechanism changes
Geology, 2010Co-Authors: Michael Stipp, Martin Scherwath, Jan Tullis, Jan H. BehrmannAbstract:The dynamically Recrystallized Grain Size is a material parameter associated with dislocation creep of crystalline solids that is especially important as a flow stress indicator via piezometer calibrations. Grain Sizes have been measured in many studies of deformed rocks as well as metals and ceramics, but global analyses of the frequency distribution of dynamically Recrystallized Grain Sizes are lacking. Here we present the first systematic investigation of the Recrystallized Grain Size distribution, for quartz. The Grain diameters, compiled from 555 samples of 31 studies of quartz mylonites deformed over a wide range of conditions, extend from ∼3 μm to 3 mm, with distinct maxima at 10–20 μm and 70–80 μm, and minima at 35–40 μm and ∼120 μm. The frequency maxima correlate with distinct microstructures and the minima with the transitions between these microstructures, which we interpret to result from the dominance of the recrystallization mechanisms of bulging, subGrain rotation, and Grain boundary migration recrystallization. These results demonstrate the necessity of distinct piezometer calibrations for different recrystallization mechanisms and highlight the importance of the Recrystallized Grain Size for theoretical models of dynamic recrystallization.
Jan Tullis - One of the best experts on this subject based on the ideXlab platform.
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a new perspective on paleopiezometry dynamically Recrystallized Grain Size distributions indicate mechanism changes
Geology, 2010Co-Authors: Michael Stipp, Martin Scherwath, Jan Tullis, Jan H. BehrmannAbstract:The dynamically Recrystallized Grain Size is a material parameter associated with dislocation creep of crystalline solids that is especially important as a flow stress indicator via piezometer calibrations. Grain Sizes have been measured in many studies of deformed rocks as well as metals and ceramics, but global analyses of the frequency distribution of dynamically Recrystallized Grain Sizes are lacking. Here we present the first systematic investigation of the Recrystallized Grain Size distribution, for quartz. The Grain diameters, compiled from 555 samples of 31 studies of quartz mylonites deformed over a wide range of conditions, extend from ∼3 μm to 3 mm, with distinct maxima at 10–20 μm and 70–80 μm, and minima at 35–40 μm and ∼120 μm. The frequency maxima correlate with distinct microstructures and the minima with the transitions between these microstructures, which we interpret to result from the dominance of the recrystallization mechanisms of bulging, subGrain rotation, and Grain boundary migration recrystallization. These results demonstrate the necessity of distinct piezometer calibrations for different recrystallization mechanisms and highlight the importance of the Recrystallized Grain Size for theoretical models of dynamic recrystallization.
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supplementary material a new perspective on paleo piezometry dynamically Recrystallized Grain Size distributions indicate mechanism changes
2010Co-Authors: Michael Stipp, Martin Scherwath, Jan Tullis, Jan H. BehrmannAbstract:For the present study, the quality of the compiled data sets is crucial. The complete data sets are therefore presented along with comments on the data quality in Table 1S for the natural and Table 2S for the experimental samples. Introductory remarks focus on why sampling procedure and Grain Size modifications during and after deformation can only weaken rather than cause discontinuities in the Recrystallized Grain Size distribution. Then we explain the basis for our data refinement and the reasons why we rely primarily on natural samples. Additional micrographs from other field examples are shown in order to demonstrate that the Tonale mylonite microstructures (Fig. 1a-c; Stipp et al. 2002a) are representative. Finally we describe the bootstrap analysis which proves the statistical significance of the bimodal Recrystallized Grain Size distribution observed in the refined data set. SAMPLING AND Grain Size MODIFICATION
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effect of water on the dislocation creep microstructure and flow stress of quartz and implications for the Recrystallized Grain Size piezometer
Journal of Geophysical Research, 2006Co-Authors: Michael Stipp, Jan Tullis, Harald BehrensAbstract:Deformation experiments on Black Hills quartzite with three different initial water contents (as-is, water-added, and vacuum-dried) were carried out in the dislocation creep regime in order to evaluate the effect of water on the Recrystallized Grain Size/flow stress piezometer. Samples were deformed in axial compression at temperatures of 750°–1100°C, strain rates between 2 × 10−7 s−1 and 2 × 10−4 s−1 and strains up to 46% using a molten salt assembly in a Griggs apparatus. An increase of the initial water content at otherwise constant deformation conditions caused a decrease in flow stress, an effect known as hydrolytic weakening. The total water content of the starting material was analyzed by Karl Fischer titration (KFT) and Fourier transform infrared (IR) spectroscopy, and quenched samples were analyzed microstructurally and by IR. Changes in the dynamic recrystallization microstructure correlate with changes in flow stress, but there is no independent effect of temperature, strain rate or water content. IR absorption spectra of the deformed spectra indicate that different water contents were maintained in the three sample sets throughout the experiments. However, the amounts of water measured within the vacuum-dried (∼260 ± 40 ppm H2O), the as-is (∼340 ± 50 ppm H2O), and the water-added (∼430 ± 110 ppm H2O) samples are significantly smaller than the initial content of the quartzite (∼640 ± 50 ppm H2O). Water from the inclusions in the starting material adds to the free fluid phase along the Grain boundaries, which probably controls the water fugacity and the flow strength, but this water is largely lost during IR sample preparation. Vacuum-dried as well as water-added samples have the same Recrystallized Grain Size/flow stress relationship as the piezometer determined for as-is samples. No independent effect of water on the piezometric relationship has been detected.
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the Recrystallized Grain Size piezometer for quartz
Geophysical Research Letters, 2003Co-Authors: Michael Stipp, Jan TullisAbstract:D=1 0 3.56±0.27 * s 1.26 ±0.13 , with no change in slope at the regime 2–3 transition and no effect of temperature or a/b stability field. Another experimental piezometer relation for regime 1 of Hirth and Tullis [1992] differs in slope, suggesting that different recrystallization mechanisms require different piezometer calibrations. INDEX TERMS: 3902 Mineral Physics: Creep and deformation; 5120 Physical Properties of Rocks: Plasticity, diffusion, and creep; 8030 Structural Geology: Microstructures; 8159 Tectonophysics: Rheology—crust and lithosphere; 8164 Tectonophysics: Stresses—crust and lithosphere. Citation: Stipp, M., and J. Tullis, The Recrystallized Grain Size piezometer for quartz, Geophys. Res. Lett., 30(21), 2088, doi:10.1029/2003GL018444, 2003.
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a Recrystallized Grain Size piezometer for experimentally deformed feldspar aggregates
Tectonophysics, 1999Co-Authors: Alice Post, Jan TullisAbstract:Abstract A Recrystallized Grain Size piezometer for low-temperature migration recrystallization in feldspar has been experimentally calibrated. Hot-pressed samples of fine-Grained albitic feldspar (Grain Size 1–10 μm) and a natural albitic feldspar aggregate (∼150 μm) were deformed in simple shear and axial compression at a temperature of 900°C and a confining pressure of 1500 MPa. Transmission electron microscopy (TEM) verified that deformation occurred by recrystallization-accommodated dislocation creep. Grain Size distributions were measured from scanning electron microscopy (SEM) photographs of polished and etched samples. The results yield a Recrystallized Grain Size piezometer relationship of d=55±5·σ−0.66±0.07 where d is the geometric mean Grain Size (μm) and σ the differential stress (MPa). The exponent is higher than that determined in previous studies of other materials for rotation recrystallization and high-temperature migration recrystallization, indicating that different recrystallization mechanisms have distinct Recrystallized Grain Size piezometer relationships.
Steven Kidder - One of the best experts on this subject based on the ideXlab platform.
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The effect of cooling during deformation on Recrystallized Grain-Size piezometry
Geology, 2020Co-Authors: Hamidreza Soleymani, Greg Hirth, Steven Kidder, Gordana GarapićAbstract:Abstract Most exposed middle- and lower-crustal shear zones experienced deformation while cooling. We investigated the effect of the strengthening associated with such cooling on differential stress estimates based on Recrystallized Grain Size. Typical geologic ratios of temperature change per strain unit were applied in Griggs Rig (high pressure-temperature deformation apparatus) general shear experiments on quartzite with cooling rates of 2–10 °C/h from 900 °C to 800 °C, and a shear strain rate of ∼2 × 10−5 s−1. Comparisons between these “cooling-ramp” experiments and control experiments at constant temperatures of 800 °C and 900 °C indicated that Recrystallized Grain Size did not keep pace with evolving stress. Mean Recrystallized Grain Sizes of the cooling-ramp experiments were twice as large as expected from the final stresses of the experiments. The traditional approach to piezometry involves a routine assumption of a steady-state microstructure, and this would underestimate the final stress during the cooling-ramp experiments by ∼40%. Recrystallized Grain Size in the cooling-ramp experiments is a better indicator of the average stress of the experiments (shear strains ≥3). Due to the temperature sensitivity of recrystallization processes and rock strength, the results may underrepresent the effect of cooling in natural samples. Cooling-ramp experiments produced wider and more skewed Grain-Size distributions than control experiments, suggesting that analyses of Grain-Size distributions might be used to quantify the degree to which Grain Size departs from steady-state values due to cooling, and thereby provide more accurate constraints on final stress.
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the Recrystallized Grain Size piezometer for quartz an ebsd based calibration
Geophysical Research Letters, 2017Co-Authors: A J Cross, Michael Stipp, David J Prior, Steven KidderAbstract:We have re-analyzed 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 (GOS), 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 RMS 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 Recrystallized Grain Size piezometer for quartz: An EBSD‐based calibration
Geophysical Research Letters, 2017Co-Authors: A J Cross, Michael Stipp, David J Prior, Steven KidderAbstract:We have re-analyzed 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 (GOS), 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 RMS 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.
Ichiko Shimizu - One of the best experts on this subject based on the ideXlab platform.
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Stress and temperature dependence of Recrystallized Grain Size: A subGrain misorientation model
Geophysical Research Letters, 1998Co-Authors: Ichiko ShimizuAbstract:The steady-state Grain Size of Earth materi- \nals undergoing solid state flow is estimated based on a\nnucleation-and-growth model of dynamic recrystallization.\nAssuming a nucleation mechanism of subGrain rotation, the\nmean diameter d of Recrystallized Grains is obtained as\nd/b = A(a/i•) -p exp[-((Qgb- Qv)/mkT)], where b is the\nlength of the Burgers vector, a is differential stress,/• is the\nshear modulus, Qgb is the activation energy for the jump\nof an atom across the Grain boundary, Qv is that for self-\ndiffusion in the Grain volume, k is the Boltzmann constant,\nT is temperature, A is a constant, p = 1.25 and m = 4\nfor intracrystalline nucleation, and p = 1.33 and rn = 3 for\nGrain-boundary nucleation. The exponent p = 1.25 • 1.33\nagrees well with available data for high- temperature dis-\nlocation creep of rock-forming minerals. A weak negative\ndependence of Grain Size on temperature is expected from\nthis theory.
Greg Hirth - One of the best experts on this subject based on the ideXlab platform.
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The effect of garnet and muscovite on the Recrystallized Grain Size of quartz from general shear experiments
2020Co-Authors: Leif Tokle, Greg Hirth, Luiz F. G. Morales, Holger StünitzAbstract:<p>To investigate the role of strong and weak secondary phases on the Recrystallized Grain Size of quartz, we performed Grain Size analyses on quenched samples from general shear experiments on quartz-garnet and quartz-muscovite mixtures. Six general shear experiments were conducted in the Griggs apparatus; three with mixtures of quartz-garnet (vol.% garnet 5, 15, 30) and three with mixtures of quartz-muscovite (vol.% muscovite 5, 10, 25). The starting powders for both set of experiments were synthetic mixtures of quartz-muscovite or quartz-garnet with 0.1 wt.% water added. The quartz-garnet experiments were conducted at 900&#176;C, a pressure of 1.2 GPa, and a shear strain rate of ~10<sup>-5</sup> s<sup>-1</sup>, while the quartz-muscovite experiments were conducted at 800&#176;C, a pressure of 1.5 GPa, and a shear strain rate of ~10<sup>-5</sup> s<sup>-1</sup>. At these deformation conditions quartz is stronger than muscovite and weaker than garnet. We observed that the bulk strength of the aggregate decreases with a greater volume percent of muscovite and increases with a greater volume percent of garnet. Garnet at these conditions does not deform plastically. The presence of secondary phases within the deforming aggregate causes stress concentrations and partitioning of strain rate between the different phases relative to the measured bulk stress and strain rate. The degree of partitioning is primarily related to the rheology and volume percent of the phases. Due to the piezometric relationship between Recrystallized Grain Size and stress, we can use the quartz Recrystallized Grain Size to determine the local stress of quartz in the experiments and compare it to the measured bulk stress. The results from these analyses will provide new insight into the effect of strain partitioning in general and of strong and weak secondary phases on quartz rheology.</p>
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The effect of cooling during deformation on Recrystallized Grain-Size piezometry
Geology, 2020Co-Authors: Hamidreza Soleymani, Greg Hirth, Steven Kidder, Gordana GarapićAbstract:Abstract Most exposed middle- and lower-crustal shear zones experienced deformation while cooling. We investigated the effect of the strengthening associated with such cooling on differential stress estimates based on Recrystallized Grain Size. Typical geologic ratios of temperature change per strain unit were applied in Griggs Rig (high pressure-temperature deformation apparatus) general shear experiments on quartzite with cooling rates of 2–10 °C/h from 900 °C to 800 °C, and a shear strain rate of ∼2 × 10−5 s−1. Comparisons between these “cooling-ramp” experiments and control experiments at constant temperatures of 800 °C and 900 °C indicated that Recrystallized Grain Size did not keep pace with evolving stress. Mean Recrystallized Grain Sizes of the cooling-ramp experiments were twice as large as expected from the final stresses of the experiments. The traditional approach to piezometry involves a routine assumption of a steady-state microstructure, and this would underestimate the final stress during the cooling-ramp experiments by ∼40%. Recrystallized Grain Size in the cooling-ramp experiments is a better indicator of the average stress of the experiments (shear strains ≥3). Due to the temperature sensitivity of recrystallization processes and rock strength, the results may underrepresent the effect of cooling in natural samples. Cooling-ramp experiments produced wider and more skewed Grain-Size distributions than control experiments, suggesting that analyses of Grain-Size distributions might be used to quantify the degree to which Grain Size departs from steady-state values due to cooling, and thereby provide more accurate constraints on final stress.
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the stress dependence of olivine creep rate implications for extrapolation of lab data and interpretation of Recrystallized Grain Size
Earth and Planetary Science Letters, 2015Co-Authors: Greg Hirth, David L KohlstedtAbstract:Abstract Based on measured values for the stress exponent, n ≈ 3.5 , combined with the empirically determined relationship between dislocation density and stress ( ρ ∝ σ 1.37 ) and an analysis of diffusion kinetics in olivine, we conclude that silicon pipe diffusion limits strain rate in the dislocation creep regime. Furthermore, assuming that steady state Recrystallized Grain Size is set by a dynamic balance between strain energy density (associated with dislocations) and surface energy density (associated with Grain boundaries), the resulting dependence of Recrystallized Grain Size on stress accurately describes experimental observations when the empirical dislocation density versus stress relationship is accounted for ( d ∝ 1 / σ 1.37 ). The improved physical understanding of the stress dependence of creep rate provides justification for incorporation of experimentally derived flow laws into models of geodynamical process and Grain Size evolution. These lab constraints combined with independent analyses of the stress dependence of mantle viscosity based on geophysical data provide bounds on rheological properties such as the yield stress of the lithosphere.