Journal articles: 'Paleopiezometry'

1

Lopez-Sanchez, M. A., and S. Llana-Fúnez. "An evaluation of different measures of dynamically recrystallized grain size for paleopiezometry or paleowattometry studies." Solid Earth 6, no. 2 (May 7, 2015): 475–95. http://dx.doi.org/10.5194/se-6-475-2015.

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Abstract. Paleopiezometry and paleowattometry studies are essential to validate models of lithospheric deformation and therefore increasingly common in structural geology. These studies require a single measure of dynamically recrystallized grain size in natural mylonites to estimate the magnitude of differential paleostress (or the rate of mechanical work). This contribution tests the various measures of grain size used in the literature and proposes the frequency peak of a grain size distribution as the most robust estimator for paleopiezometry or paleowattometry studies. The novelty of the approach resides in the use of the Gaussian kernel density estimator as an alternative to the classical histograms, which improves reproducibility. A free, open-source, easy-to-handle script named GrainSizeTools ( http://www.TEOS-10.org) was developed with the aim of facilitating the adoption of this measure of grain size in paleopiezometry or paleowattometry studies. The major advantage of the script over other programs is that by using the Gaussian kernel density estimator and by avoiding manual steps in the estimation of the frequency peak, the reproducibility of results is improved.

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Rutter, Ernest, David Wallis, and Kamil Kosiorek. "Application of Electron Backscatter Diffraction to Calcite-Twinning Paleopiezometry." Geosciences 12, no. 6 (May 25, 2022): 222. http://dx.doi.org/10.3390/geosciences12060222.

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Electron backscatter diffraction (EBSD) was used to determine the orientation of mechanically twinned grains in Carrara marble experimentally deformed to a small strain (≤4%) at room temperature and at a moderate confining pressure (225 MPa). The thicknesses of deformation twins were mostly too small to permit determination of their orientation by EBSD but it proved possible to measure their orientations by calculating possible twin orientations from host grain orientation, then comparing calculated traces to the observed twin traces. The validity of the Turner & Weiss method for principal stress orientations was confirmed, particularly when based on calculation of resolved shear stress. Methods of paleopiezometry based on twinned volume fraction were rejected but a practical approach is explored based on twin density. However, although twin density correlates positively with resolved shear stress, there is intrinsic variability due to unconstrained variables such as non-uniform availability of twin nucleation sites around grain boundaries that imposes a limit on the achievable accuracy of this approach.

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Labeur, Aurélie, Nicolas E. Beaudoin, Olivier Lacombe, Laurent Emmanuel, Lorenzo Petracchini, Mathieu Daëron, Sebastian Klimowicz, and Jean-Paul Callot. "Burial-Deformation History of Folded Rocks Unraveled by Fracture Analysis, Stylolite Paleopiezometry and Vein Cement Geochemistry: A Case Study in the Cingoli Anticline (Umbria-Marche, Northern Apennines)." Geosciences 11, no. 3 (March 13, 2021): 135. http://dx.doi.org/10.3390/geosciences11030135.

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Unravelling the burial-deformation history of sedimentary rocks is prerequisite information to understand the regional tectonic, sedimentary, thermal, and fluid-flow evolution of foreland basins. We use a combination of microstructural analysis, stylolites paleopiezometry, and paleofluid geochemistry to reconstruct the burial-deformation history of the Meso-Cenozoic carbonate sequence of the Cingoli Anticline (Northern Apennines, central Italy). Four major sets of mesostructures were linked to the regional deformation sequence: (i) pre-folding foreland flexure/forebulge; (ii) fold-scale layer-parallel shortening under a N045 σ1; (iii) syn-folding curvature of which the variable trend between the north and the south of the anticline is consistent with the arcuate shape of the anticline; (iv) the late stage of fold tightening. The maximum depth experienced by the strata prior to contraction, up to 1850 m, was quantified by sedimentary stylolite paleopiezometry and projected on the reconstructed burial curve to assess the timing of the contraction. As isotope geochemistry points towards fluid precipitation at thermal equilibrium, the carbonate clumped isotope thermometry (Δ47) considered for each fracture set yields the absolute timing of the development and exhumation of the Cingoli Anticline: layer-parallel shortening occurred from ~6.3 to 5.8 Ma, followed by fold growth that lasted from ~5.8 to 3.9 Ma.

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Lacombe, Olivier, Camille Parlangeau, Nicolas E. Beaudoin, and Khalid Amrouch. "Calcite Twin Formation, Measurement and Use as Stress–Strain Indicators: A Review of Progress over the Last Decade." Geosciences 11, no. 11 (October 28, 2021): 445. http://dx.doi.org/10.3390/geosciences11110445.

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Mechanical twins are common microstructures in deformed calcite. Calcite twins have been used for a long time as indicators of stress/strain orientations and magnitudes. Developments during the last decade point toward significant improvements of existing techniques as well as new applications of calcite twin analysis in tectonic studies. This review summarises the recent progress in the understanding of twin formation, including nucleation and growth of twins, and discusses the concept of CRSS and its dependence on several factors such as strain, temperature and grain size. Classical and recent calcite twin measurement techniques are also presented and their pros and cons are discussed. The newly proposed inversion techniques allowing for the use of calcite twins as indicators of orientations and/or magnitudes of stress and strain are summarized. Benefits for tectonic studies are illustrated through the presentation of several applications, from the scale of the individual tectonic structure to the continental scale. The classical use of calcite twin morphology (e.g., thickness) as a straightforward geothermometer is critically discussed in the light of recent observations that thick twins do not always reflect deformation temperature above 170–200 °C. This review also presents how the age of twinning events in natural rocks can be constrained while individual twins cannot be dated yet. Finally, the review addresses the recent technical and conceptual progress in calcite twinning paleopiezometry, together with the promising combination of this paleopiezometer with mechanical analysis of fractures or stylolite roughness.

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Stipp, Michael, Jan Tullis, Martin Scherwath, and Jan H. Behrmann. "A new perspective on paleopiezometry: Dynamically recrystallized grain size distributions indicate mechanism changes." Geology 38, no. 8 (August 2010): 759–62. http://dx.doi.org/10.1130/g31162.1.

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A. Lopez-Sanchez, Marco. "GrainSizeTools: a Python script for grain size analysis and paleopiezometry based on grain size." Journal of Open Source Software 3, no. 30 (October 6, 2018): 863. http://dx.doi.org/10.21105/joss.00863.

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Lopez-Sanchez, M. A., and S. Llana-Fúnez. "GrainSizeTools: a Python script for estimating the dynamically recrystallized grain size from grain sectional areas." Solid Earth Discussions 6, no. 2 (November 27, 2014): 3141–96. http://dx.doi.org/10.5194/sed-6-3141-2014.

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Abstract. Paleopiezometry and paleowattometry studies, required to validate models of lithospheric deformation, are increasingly common in structural geology. These studies require a numeric parameter to characterize and compare the dynamically recrystallized grain size of natural mylonites with those obtained in rocks deformed under controlled conditions in the laboratory. We introduce a new tool, a script named GrainSizeTools, to obtain a single numeric value representative of the dynamically recrystallized grain size from the measurement of grain sectional areas (2-D data). For this, it is used an estimate of the most likely grain size of the grain size population, using an alternative tool to the classical histograms and bar plots: the peak of the Gaussian kernel density estimation. The results are comparable to those that can be obtained by other stereological software available, such as the StripStar and CSDCorrections, but with the advantage that the script is specifically developed to produce a single and reproducible value avoiding manual steps in the estimation, which penalizes reproducibility.

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Newman, Julie, Vasileios Chatzaras, Basil Tikoff, Jan R. Wijbrans, William M. Lamb, and Martyn R. Drury. "Strain Localization at Constant Strain Rate and Changing Stress Conditions: Implications for Plate Boundary Processes in the Upper Mantle." Minerals 11, no. 12 (November 30, 2021): 1351. http://dx.doi.org/10.3390/min11121351.

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We present results from a natural deformed shear zone in the Turon de Técouère massif of the French Pyrenees that directly addresses the processes involved in strain localization, a topic that has been investigated for the last 40 years by structural geologists. Paleopiezometry indicates that differential stresses are variable both spatially across the zone, and temporally during exhumation. We have, however, also calculated strain rate, which remains constant despite changes in stress. This result appears to be at odds with recent experimental deformation on monophase (olivine) rocks, which indicate that strain localization occurs dominantly as a result of constant stress. We hypothesize that in the Turon de Técouère massif—and many natural shear zones—strain localization occurs as a result of reactions, which decrease the grain size and promote the activation of grain size sensitive deformation mechanisms. From a tectonics perspective, this study indicates that the deformation rate in a particular plate boundary is relatively uniform. Stress, however, varies to accommodate this deformation. This viewpoint is consistent with deformation at a plate boundary, but it is not the typical way in which we interpret strain localization.

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White, S. H., M. R. Drury, S. E. Ion, and F. J. Humphreys. "Large strain deformation studies using polycrystalline magnesium as a rock analogue. Part I: grain size paleopiezometry in mylonite zones." Physics of the Earth and Planetary Interiors 40, no. 3 (November 1985): 201–7. http://dx.doi.org/10.1016/0031-9201(85)90130-x.

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10

Beaudoin, Nicolas, Olivier Lacombe, Daniel Koehn, Marie-Eléonore David, Natalie Farrell, and David Healy. "Vertical stress history and paleoburial in foreland basins unravelled by stylolite roughness paleopiezometry: Insights from bedding-parallel stylolites in the Bighorn Basin, Wyoming, USA." Journal of Structural Geology 136 (July 2020): 104061. http://dx.doi.org/10.1016/j.jsg.2020.104061.

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11

Fazio, Eugenio, Gaetano Ortolano, Roberto Visalli, Rosolino Cirrincione, Hartmut Kern, Kurt Mengel, Antonino Pezzino, and Rosalda Punturo. "Strain rates of the syn-tectonic Symvolon pluton (Southern Rhodope Core Complex, Greece): an integrated approach combining quartz paleopiezometry, flow laws and PT pseudosections." Italian Journal of Geosciences 137, no. 2 (June 2018): 219–37. http://dx.doi.org/10.3301/ijg.2018.10.

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12

Beaudoin, N., M. Gasparrini, M. E. David, O. Lacombe, and D. Koehn. "Bedding-parallel stylolites as a tool to unravel maximum burial depth in sedimentary basins: Application to Middle Jurassic carbonate reservoirs in the Paris basin, France." GSA Bulletin 131, no. 7-8 (December 10, 2018): 1239–54. http://dx.doi.org/10.1130/b32064.1.

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Abstract In recent years stylolites, which are rough dissolution surfaces commonly found in carbonates, have been used for paleopiezometry estimates. The Stylolite Roughness Inversion Technique (SRIT) applied on sedimentary bedding-parallel stylolites (BPS) grants access to the maximum principal vertical stress experienced by the host carbonates and thus to their maximum burial paleo-depth. This study reports the results of SRIT applied to a BPS population hosted in carbonate platform reservoirs of the Paris basin sub-surface (France). Middle Jurassic carbonates from two well cores from the depocenter and margin of the basin, for which the burial and thermal history are known, based on a thermally calibrated 3-D basin model, were analyzed. By defining a consistency criterion and using two signal treatment methods, we propose a new approach to select which BPS can be reliably used to reconstruct the maximum vertical stress undergone by the host carbonates, which then can be converted into maximum burial depth. The study of a BPS population shows that there is a control operated by the host rock texture and the stylolite morphology on the burial depth recorded. Especially suture and sharp peak BPS are better suited to estimate the real maximum depth, whereas seismogram pinning BPS record preferentially intermediate depths. Median values of maximum depth derived from our data set (1300 and 1650 m for the margin and depocenter cores, respectively) are in line with maximum burial estimates provided by conventional basin modeling (1450 and 1800 m, respectively), thus showing that SRIT is a standalone robust depth gauge in sedimentary basins, provided sample selection and data treatment are carried out in a rigorous and thoughtful manner.

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Mosonyi, Emilia, and Ferenc L. Forray. "Metamorphic tourmaline and its petrogenetic significance from the Maramureș Mountains (East Carpathians, Romania)." Austrian Journal of Earth Sciences 115, no. 1 (January 1, 2022): 146–66. http://dx.doi.org/10.17738/ajes.2022.0007.

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Abstract This study describes mineralogical and crystallochemical characteristics of metamorphic tourmalines from an Alpine shear zone in a Variscan metamorphic rock sequence from the Maramures region in the northern part of the East Carpathians. We use this mineral to unravel aspects of the evolution of the tourmaline bearing host rocks and compare the crystallo-chemical characteristics to other tourmalines from Alps. Petrographic and microstructural observations, as well as electron microprobe analyses on several zoned tourmalines and associated minerals (mica, feldspar) from mylonitic schist of the Rebra terrane (Maramureș Mountains), indicate that the pre-kinematic tourmalines belong to the alkali group (Na dominant), hydroxyl dominated on the crystallographic W-site and can be assigned to the species dravite and schorl. The tourmaline-bearing rocks have a metasedimentary protolith. The analysed porphyroblasts, rotated by simple shear, show corroded rim that are interpreted to have formed due to pressure release. Three main compositional zones were evidenced on a tourmaline porphyroblast: a core zone and two asymmetrically arranged inclusion-poor/free rims, all formed in pre-alpine prograde metamorphic conditions. Based on mineral microstructural relations and geothermobarometry (tourmaline–muscovite, tourmaline–plagioclase geothermometry and phengite geobarometry), the metamorphic peak conditions of the investigated Rebra terrane were evaluated to have been at a temperature of ca. 590 to 620 ± 22 °C and Pmin = 5.5 - 6.0 ± 0.5 kbar. By observing dynamically recrystallized microstructures in quartz and feldspar in the shear zone a temperature of 350 - 400 °C was estimated and the quartz paleopiezometry outlined a differential stress of about 1.5 kbar that implied only minor chemical change in tourmaline outer zone.

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Hughes, Cameron A., Micah J. Jessup, Colin A. Shaw, and Dennis L. Newell. "Deformation conditions during syn-convergent extension along the Cordillera Blanca shear zone, Peru." Geosphere 15, no. 4 (June 13, 2019): 1342–67. http://dx.doi.org/10.1130/ges02040.1.

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AbstractStrain localization across the brittle-ductile transition is a fundamental process in accommodating tectonic movement in the mid-crust. The tectonically active Cordillera Blanca shear zone (CBSZ), a ∼200-km-long normal-sense shear zone situated within the footwall of a discrete syn-convergent extensional fault in the Peruvian Andes, is an excellent field laboratory to explore this transition. Field and microscopic observations indicate consistent top-down-to-the-southwest sense of shear and a sequence of tectonites ranging from undeformed granodiorite through mylonite and ultimately fault breccia along the detachment.Using microstructural analysis, two-feldspar and Ti-in-quartz (TitaniQ) thermometry, recrystallized quartz paleopiezometry, and analysis of quartz crystallographic preferred orientations, we evaluate the deformation conditions and mechanisms in quartz and feldspar across the CBSZ. Deformation temperatures derived from asymmetric strain-induced myrmekite in a subset of tectonite samples are 410 ± 30 to 470 ± 36 °C, consistent with TitaniQ temperatures of 450 ± 60 to 490 ± 33 °C and temperatures >400 °C estimated from microstructural criteria. Brittle fabrics overprint ductile fabrics within ∼150 m of the detachment that indicate that deformation continued to lower-temperature (∼280–400 °C) and/or higher-strain-rate conditions prior to the onset of pervasive brittle deformation. Initial deformation occurred via high-temperature fracturing and dissolution-precipitation in feldspar. Continued subsolidus deformation resulted in either layering of mylonites into monophase quartz and fine-grained polyphase domains oriented subparallel to macroscopic foliation or the interconnection of recrystallized quartz networks oriented obliquely to macroscopic foliation. The transition to quartz-controlled rheology occurred at temperatures near ∼500 °C and at a differential stress of ∼16.5 MPa. Deformation within the CBSZ occurred predominantly above ∼400 °C and at stresses up to ∼71.4 MPa prior to the onset of brittle deformation.

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Beaudoin, Nicolas, and Olivier Lacombe. "Recent and future trends in paleopiezometry in the diagenetic domain: Insights into the tectonic paleostress and burial depth history of fold-and-thrust belts and sedimentary basins." Journal of Structural Geology 114 (September 2018): 357–65. http://dx.doi.org/10.1016/j.jsg.2018.04.001.

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Beaudoin, Nicolas, Daniel Koehn, Olivier Lacombe, Alexandre Lecouty, Andrea Billi, Einat Aharonov, and Camille Parlangeau. "Fingerprinting stress: Stylolite and calcite twinning paleopiezometry revealing the complexity of progressive stress patterns during folding-The case of the Monte Nero anticline in the Apennines, Italy." Tectonics 35, no. 7 (July 2016): 1687–712. http://dx.doi.org/10.1002/2016tc004128.

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van der Werf, Thomas, Vasileios Chatzaras, Leo Marcel Kriegsman, Andreas Kronenberg, Basil Tikoff, and Martyn R. Drury. "Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico." Solid Earth 8, no. 6 (December 21, 2017): 1211–39. http://dx.doi.org/10.5194/se-8-1211-2017.

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Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.

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Beaudoin, Nicolas, Olivier Lacombe, Marie‐Eléonore David, and Daniel Koehn. "Does stress transmission in forelands depend on structural style? Distinctive stress magnitudes during Sevier thin‐skinned and Laramide thick‐skinned layer‐parallel shortening in the Bighorn Basin (USA) revealed by stylolite and calcite twinning paleopiezometry." Terra Nova 32, no. 3 (February 6, 2020): 225–33. http://dx.doi.org/10.1111/ter.12451.

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Li, Le, and Shaocheng Ji. "On microboudin paleopiezometers and their applications to constrain stress variations in tectonites." Journal of Structural Geology 130 (January 2020): 103928. http://dx.doi.org/10.1016/j.jsg.2019.103928.

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Beaudoin, Nicolas E., Aurélie Labeur, Olivier Lacombe, Daniel Koehn, Andrea Billi, Guilhem Hoareau, Adrian Boyce, et al. "Regional-scale paleofluid system across the Tuscan Nappe–Umbria–Marche Apennine Ridge (northern Apennines) as revealed by mesostructural and isotopic analyses of stylolite–vein networks." Solid Earth 11, no. 4 (August 31, 2020): 1617–41. http://dx.doi.org/10.5194/se-11-1617-2020.

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Abstract. We report the results of a multiproxy study that combines structural analysis of a fracture–stylolite network and isotopic characterization of calcite vein cements and/or fault coating. Together with new paleopiezometric and radiometric constraints on burial evolution and deformation timing, these results provide a first-order picture of the regional fluid systems and pathways that were present during the main stages of contraction in the Tuscan Nappe and Umbria–Marche Apennine Ridge (northern Apennines). We reconstruct four steps of deformation at the scale of the belt: burial-related stylolitization, Apenninic-related layer-parallel shortening with a contraction trending NE–SW, local extension related to folding, and late-stage fold tightening under a contraction still striking NE–SW. We combine the paleopiezometric inversion of the roughness of sedimentary stylolites – that constrains the range of burial depth of strata prior to layer-parallel shortening – with burial models and U–Pb absolute dating of fault coatings in order to determine the timing of development of mesostructures. In the western part of the ridge, layer-parallel shortening started in Langhian time (∼15 Ma), and then folding started at Tortonian time (∼8 Ma); late-stage fold tightening started by the early Pliocene (∼5 Ma) and likely lasted until recent/modern extension occurred (∼3 Ma onward). The textural and geochemical (δ18O, δ13C, Δ47CO2 and 87Sr∕86Sr) study of calcite vein cements and fault coatings reveals that most of the fluids involved in the belt during deformation either are local or flowed laterally from the same reservoir. However, the western edge of the ridge recorded pulses of eastward migration of hydrothermal fluids (>140 ∘C), driven by the tectonic contraction and by the difference in structural style of the subsurface between the eastern Tuscan Nappe and the Umbria–Marche Apennine Ridge.

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Takeshita, Toru. "Quartz Microstructures from the Sambagawa Metamorphic Rocks, Southwest Japan: Indicators of Deformation Conditions during Exhumation." Minerals 11, no. 10 (September 25, 2021): 1038. http://dx.doi.org/10.3390/min11101038.

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The Sambagawa metamorphic rocks in central Shikoku, southwest Japan consist of an inverted metamorphic sequence from the upper chlorite to oligoclase-biotite zones at the lower structural level (LSL), which is overlain by a normal metamorphic sequence consisting of the albite-biotite and garnet zones at the upper structural level (USL). These sequences form a large-scale recumbent fold called the Besshi nappe. To unravel the mechanism of recrystallization and physical conditions in quartz, and their relation to exhumation tectonics, microstructures of recrystallized quartz grains in quartz schist from the Asemi-Saruta-Dozan River traverse were analyzed. The recrystallized quartz grain size increases with increasing structural level from 40 µm in the upper chlorite zone to 160 µm in the garnet zone of the USL. Further, the mechanism of dynamic recrystallization of quartz changes from subgrain rotation to grain boundary migration with increasing structural level across the uppermost garnet zone of the LSL. From these data, the deformation temperatures in quartz schist are calculated to increase with increasing structural level within the range between 300 and 450 °C using paleopiezometers and experimental flow laws. It could be interpreted that a rapid cooling of the Besshi nappe from above is responsible for the deformation temperatures recorded in quartz schist.

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Ji, Shaocheng, and Le Li. "Feldspar microboudinage paleopiezometer and its applications to estimating differential stress magnitudes in the continental middle crust (examples from west Yunnan, China)." Tectonophysics 805 (April 2021): 228778. http://dx.doi.org/10.1016/j.tecto.2021.228778.

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Brochard, Crystal, Michel Jébrak, and Stéphane De Souza. "Deformation and paleopiezometry of auriferous quartz veins in Archean orogenic gold deposits of the Abitibi greenstone belt." Journal of Structural Geology, October 2023, 104986. http://dx.doi.org/10.1016/j.jsg.2023.104986.

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Duan, Qingbao, Åke Fagereng, Jianye Chen, and Thomas Blenkinsop. "Fluid environment controls along-strike variation in slip style: Midcrustal geological signatures from the Red River fault, China." Geology, February 28, 2024. http://dx.doi.org/10.1130/g51865.1.

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The slip style of continental midcrustal shear zones plays a crucial role in determining the seismogenic potential of faults, but it remains poorly understood because geological observations that can be directly tied to seismic behavior are scarce. We describe frictional-viscous shear zones in the Red River fault, China, which consists of two segments with distinct seismic behaviors and fluid availabilities. The northern segment hosts moderate to large earthquakes, and midcrustal fault slip is localized into mylonitized pseudotachylyte-bearing layers where dynamically recrystallized quartz records flow stresses exceeding 100 MPa and accelerated viscous creep. The southern segment is dominantly aseismic but active microseimically. Fault slip is accommodated in several mylonitized cataclasite layers, comprising interconnected biotite and intervening fractured clasts, with evidence for pervasive dissolution-precipitation creep. Microstructures, paleopiezometry, and microphysical modeling suggest transient aseismic slip in response to increased strain rates during viscous creep at <50 MPa. We interpret that along-strike variations in fluid environment control fault slip styles and seismic behaviors. The dry and strong northern segment is capable of nucleating large earthquakes, while greater fluid availability in the southern segment activates dissolution-precipitation creep at low driving stresses, which limits interseismic elastic strain accumulation at frictional-viscous transition depths. In this model, compaction-driven fluid pressurization and dilatant hardening are invoked to explain the aseismic slip transients in the southern segment.

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Bah, Boubacar, Olivier Lacombe, Nicolas E. Beaudoin, Aniès Zeboudj, Claude Gout, Jean-Pierre Girard, and Pierre-Alexandre Teboul. "Paleostress evolution of the West Africa passive margin: New insights from calcite twinning paleopiezometry in the deeply buried syn-rift TOCA formation (Lower Congo basin)." Tectonophysics, July 2023, 229997. http://dx.doi.org/10.1016/j.tecto.2023.229997.

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Zeboudj, Aniès, Bah Boubacar, Olivier Lacombe, Nicolas E. Beaudoin, Claude Gout, Nicolas Godeau, Girard Jean-Pierre, and Pierre Deschamps. "Depicting past stress history at passive margins: A combination of calcite twinning and stylolite roughness paleopiezometry in supra-salt Sendji deep carbonates, Lower Congo Basin, west Africa." Marine and Petroleum Geology, March 2023, 106219. http://dx.doi.org/10.1016/j.marpetgeo.2023.106219.

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Wu, Yawei, Jianxin Zhang, Bo Zhang, Xiaohong Mao, Zenglong Lu, Guisheng Zhou, Xia Teng, and Qi Guo. "Early Paleozoic oblique convergence from subduction to collision: Insights from timing and structural style of the transpressional dextral shear zone in the Qilian orogen, northern Tibet of China." Geological Society of America Bulletin, September 11, 2023. http://dx.doi.org/10.1130/b36947.1.

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Transpressional shear zones commonly occur in ancient and modern convergent plate boundaries to accommodate oblique plate convergence. The early Paleozoic Qilian orogen in northeastern Tibet records the subduction of Proto-Tethyan Ocean lithosphere and the accretion-collision of various magmatic arcs and continental terranes. This study focused on the Datong ductile shear zone, which represents the central part of the WNW-ESE−striking ductile shear zone along the northern margin of the Qilian block in the Qilian orogen. This structure bears key information about the evolution of oblique convergence during the early Paleozoic orogeny. The kinematics and timing of the Datong ductile shear zone were investigated via field-based, microstructural, and mica 40Ar/39Ar dating analyses. Mesostructural and microstructural data showed predominantly dextral strike-slip shearing within the Datong ductile shear zone. Microstructural features and quartz c-axis crystallographic preferred orientation patterns indicated that dextral ductile shearing occurred under lower-amphibolite-facies conditions (∼500−550 °C and ∼5.6 kbar) within the shear zone. Microstructures of quartz showed subgrain rotation (SGR) and grain boundary migration (GBM), suggesting dislocation creep−dominated deformation. A strain rate of 10−12 s−1 and a differential stress of 25−39 MPa were estimated by the rheological flow law and quartz paleopiezometry. Finite strain measurements indicated that all deformed rocks of the Datong ductile shear zone exhibit a weakly oblate ellipsoid near the plane strain. Kinematic vorticity (ranging 0.47−0.83) analysis suggested the coexistence of simple shear and pure shear strains within the Datong ductile shear zone, indicating a transpressional setting. Biotite and muscovite 40Ar/39Ar data showed that transpressional shearing deformation started in the Ordovician (before 453 Ma) and lasted to the Silurian (ca. 430 Ma). Our new data combined with regional geological data show that the deformation type, kinematics, and dynamics of the Datong ductile shear zone were controlled by the southward oblique subduction of the Paleo-Qilian Ocean (Proto-Tethyan Ocean) and the following oblique collision between the Qilian block and the Alxa block. The intensive transpressional deformation along the northern Qilian block may reflect strong coupling between the subducting Paleo-Qilian oceanic slab and the overriding Qilian block as well as a high degree of convergence obliquity during the ongoing early Paleozoic convergence.

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Journal articles on the topic 'Paleopiezometry'

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