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The present work illustrates the structural setting in the Hamadat core complex, which located in the Midyan terrane. It is essential to understand deformational processes and products at different scales, which depend on the calculation of finite strain. To assess the tectonic development and structures in the Hamadat core complex, we use field investigation, finite strain analysis and microstructural examination. The Hamadat core complex employed the Rf/φ and Fry techniques for feldspar and mafic grains with 24 collected samples for gneisses, metavolcano-sedimentary rocks from both the Zaam and Baydah groups, deformed granodiorite for Jar-Salajah intrusion and Qazzaz granite. According to finite-strain data, the various rock units have moderate to high degree of deformation, and the axial ratios for XZ section vary from 1.80 to 4.50 for the Rf/φ technique and from 2.10 to 7.40 for the Fry technique. It concluded that the shortening axes display the subvertical related to the subhorizontal foliation. The strain data have the same main-phase foliation and similar deformation behavior. Finite strain acquired through high pressure metamorphism in this instance suggested that the contacts of nappe developed through the buildup of ductile strains. Also, during thrusting and intrusions throughout the deformation process, a building of brittle to ductile deformation was mostly caused by pure shearing in the study area. [ABSTRACT FROM AUTHOR]

Seismic anisotropy constitutes a useful tool for imaging the structure along the plate interface in subduction zones, but the seismic properties of mafic blueschists, a common rock type in subduction zones, remain poorly constrained. We applied the technique of electron backscatter diffraction (EBSD) based petrofabric analysis to calculate the seismic anisotropies of 14 naturally deformed mafic blueschists at dry, ambient conditions. The ductilely deformed blueschists were collected from terranes with inferred peak P‐T conditions applicable to subducting slabs at or near the plate interface in active subduction zones. Epidote blueschists display the greatest P wave anisotropy range (AVp ∼7%–20%), while lawsonite blueschist AVp ranges from ∼2% to 10%. S wave anisotropies generate shear wave splitting delay times up to ∼0.1 s over a thickness of 5 km. AVp magnitude increases with glaucophane abundance (from areal EBSD measurements), decreases with increasing epidote or lawsonite abundance, and is enhanced by glaucophane crystallographic preferred orientation (CPO) strength. Two‐phase rock recipe models provide further evidence of the primary role of glaucophane, epidote, and lawsonite in generating blueschist seismic anisotropy. The symmetry of P wave velocity patterns reflects the deformation‐induced CPO type in glaucophane—an effect previously observed for hornblende on amphibolite P wave anisotropy. The distinctive seismic properties that distinguish blueschist from other subduction zone rock types and the strong correlation between anisotropy magnitude/symmetry and glaucophane CPO suggest that seismic anisotropy may be a useful tool in mapping the extent and deformation of blueschists along the interface, and the blueschist‐eclogite transition in active subduction zones. Plain Language Summary: The directional dependence of seismic wave speeds in the subsurface, or seismic anisotropy, can allow us to map the Earth's structure in subduction zones. To improve the interpretation of seismic data collected in active subduction zones, we characterized the range of seismic anisotropy created by blueschists (a common subduction zone rock‐type) that were returned to the surface after being deformed in ancient subduction margins. We calculate the anisotropy of each blueschist rock from mineral orientations collected in the lab combined with the elastic properties of these minerals. Trends in seismic anisotropy were compared to the changes in composition and preferred orientations of minerals (produced by deformation). We found that blueschists can generate a broad range of seismic anisotropy, and that this anisotropy is enhanced by increasing amounts of the mineral glaucophane. The seismic anisotropy is further increased when the glaucophane minerals are more uniformly oriented, as is typical in rocks that have experienced higher levels of deformation. The seismic anisotropy and seismic wave speeds of blueschists are distinctive from those of other common subduction zone rocks. Therefore, these results suggest blueschist seismic anisotropy can be used to improve our ability to map structure and deformation occurring in active subduction zones. Key Points: Calculated blueschist Vp anisotropy up to ∼20% with a plateau at ∼10%, with lineation‐parallel fast axis and foliation‐normal slow axisThe anisotropy magnitude increases with glaucophane modal abundance/crystallographic preferred orientation (CPO) strength and is diluted by epidote/lawsonite abundanceThe glaucophane CPO type correlates with the Vp pattern and increasing AVp magnitude in mafic blueschists [ABSTRACT FROM AUTHOR]

Electron backscatter diffraction (EBSD) methods are used to investigate the presence of microstructures in pyrite from the giant breccia-hosted Olympic Dam iron–oxide copper gold (IOCG) deposit, South Australia. Results include the first evidence for ductile deformation in pyrite from a brecciated deposit. Two stages of ductile behavior are observed, although extensive replacement and recrystallization driven by coupled dissolution–reprecipitation reaction have prevented widespread preservation of the earlier event. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) element maps of pyrite confirm that many pyrite grains display compositional zoning with respect to As, Co, and Ni, but that the zoning is often irregular, patchy, or otherwise disrupted and are readily correlated with observed microstructures. The formation of ductile microstructures in pyrite requires temperatures above ~260 °C, which could potentially be related to heat from radioactive decay and fault displacements during tectonothermal events. Coupling EBSD methods with LA-ICP-MS element mapping allows a comprehensive characterization of pyrite textures and microstructures that are otherwise invisible to conventional reflected light or BSE imaging. Beyond providing new insights into ore genesis and superimposed events, the two techniques enable a detailed understanding of the grain-scale distribution of minor elements. Such information is pivotal for efforts intended to develop new ways to recover value components (precious and critical metals), as well as remove deleterious components of the ore using low-energy, low-waste ore processing methods. [ABSTRACT FROM AUTHOR]

This contribution presents a review exploring some aspects and issues surrounding the links between metamorphism and deformation at different scales. I first discuss the quantification methods of thermodynamics and the parameters able to overcome the kinetic barriers for metamorphic reactions. On the basis of some world's type iconic examples I discuss how metamorphism is likely to portray the thermo-mechanical evolution of lithosphere active zones, thus large-scale tectonic processes. Finally, I present the multiple interactions between metamorphism and deformation at rock and outcrop scales. [ABSTRACT FROM AUTHOR]

The Eaux‐Chaudes massif provides keys to unravel the deep‐seated deformation of the Iberian rifted margin during the Alpine orogeny in the Pyrenees. The massif conforms to an inlier of upper Cretaceous carbonate rocks within the Paleozoic basement of the western Axial Zone, originally deposited in the upper margin shelf before the Cenozoic collision. New geological mapping and cross‐section construction lead to the description of the lateral structural variation from a km‐scale fold nappe in the west to a ductile, imbricate fold‐thrust fan in the east. The transition from a Variscan pluton to Devonian metasediments underlying the autochthonous Cretaceous induced this structural change. Recumbent folding, which involved upper Paleozoic rocks, was facilitated by a lower detachment in Silurian slates and an upper detachment in an overlying Keuper shale and evaporite thrust sheet. Remnants of this allochthonous sheet form shale and ophite bodies pinched within the upper Cretaceous carbonates, conforming unusual tertiary welds. Ductile shear in the overturned limb of the Eaux‐Chaudes fold nappe imparted strong mylonitic foliation in carbonate rocks, often accompanied by N‐S stretching lineation and top‐to‐the‐south kinematic indicators. The burial of the massif by basement‐involved thrust sheets and the Keuper sheet, along with their Mesozoic‐Cenozoic cover, account for ductile deformation conditions and a structural style not reported hitherto for the Alpine Pyrenees. A hypothesis for the tectonic restoration of this part of the Pyrenean hinterland is finally proposed. Key Points: Alpine ductile deformation and nappe stacking involving basement evidence a tectonic style not reported previously for the Alpine PyreneesUnusual tertiary weld‐like structures have been recognized within the autochthon upper Cretaceous rocksStrong structural variability is evidenced along the Eaux‐Chaudes massif [ABSTRACT FROM AUTHOR]

The Columbrets Basin is the largest Mesozoic rift basin of the Valencia Trough in the Western Mediterranean. The analysis of a seismic‐reflection survey makes it possible to reconstruct the tectonic fabric underlying the sedimentary basin, including the structure of the top of the lower crust and the Moho. It is proposed that the ductile deformation of the mid‐lower crust was the main mechanism controlling the basin geometry, with the radial flow of mid‐lower crust coeval with the reactivation of two large‐offset SW‐dipping normal faults, inherited from the precursor Permian–Triassic rifting. Mid‐lower crustal necking occurred below the major depocenters, immediately before hyperextension. Our results provide new insight into the formation of circular‐shaped basins and the evolution of depth‐dependent extensional processes during rifting. [ABSTRACT FROM AUTHOR]

This contribution presents a review exploring some aspects and issues surrounding the links between metamorphism and deformation at different scales. I first discuss the quantification methods of thermodynamics and the parameters able to overcome the kinetic barriers for metamorphic reactions. On the basis of some world’s type iconic examples I discuss how metamorphism is likely to portray the thermo-mechanical evolution of lithosphere active zones, thus large-scale tectonic processes. Finally, I present the multiple interactions between metamorphism and deformation at rock and outcrop scales.

ABSTRACTIn this study, we investigated the Zicavo Metamorphic Complex (southern Corsica), which is part of the innermost Axial Zone of the Corsica-Sardinia Variscan belt. To better evaluate its geological and structural outline, a 1:5000 geological map, coupled with new structural/microstructural and petrographic data, is presented. The complex is formed by three tectonic units, from bottom to top: (i) an Orthogneiss Unit, (ii) a Leptyno-Amphibolite Unit, and (iii) a Micaschist Unit. They are separated by ductile shear zones with a top-to-the-SE sense of shear. They underwent a polyphase deformation and polymetamorphic history, with a shortening stage in the amphibolite facies, responsible for the main structures and shearing, followed by an exhumation phase.

Archean gneiss domes are a very common structure in old cratons, these are different from the structural patterns in the post‐Archean linear orogenic belts related to subduction and collision. There are two tectonic models in Archean tectonics: horizontal tectonism and vertical tectonism. The formation mechanisms of Archean gneiss domes are still debated. Here we present data from the Anziling gneiss dome, a typical gneiss dome structure from the eastern North China Craton, which was formed dominantly by vertical tectonism during Neoarchean times (2554–2452 Ma). The Anziling gneiss dome is located in the east of Shuangshanzi, East Heibei Province and consists of the Anziling gneiss (a diopside‐monzonitic gneiss) in the center outwards surrounded by the Jiguanshan gneiss (hornblende‐plagioclase gneiss) and the Niuxinshan gneiss (trondhjemitic gneiss), together showing an irregular elliptical shape with a NE‐ward extending tail on the surface. But in the cross‐section, it represents a deflective dome, both north‐western and south‐eastern limbs dip approximately to the west. The dome suffered inhomogeneous ductile shear deformation, much stronger with more displacement in the north‐western half (especially close to the margin) than that in the eastern half. The core area shows only a relatively weak deformation. Therefore, we suggest that the Anziling gneiss dome was formed by the TTG (trondhjemite, tonalite, granodiorite) pluton rising obliquely up towards the east by diapirism in the first stage, followed by sub‐horizontal emplacement towards the north and then to the north‐east associated with clockwise rotation in the second stage. The Anziling gneiss dome and its neighbouring Shuangshanzi shear zone were formed simultaneously, indicating that the Anziling gneiss dome was driven by both gravitational forces and magma diapirism. [ABSTRACT FROM AUTHOR]

In migmatitic environments the behaviour of the system is controlled by the generation and amount of the anatectic melt. Accordingly, migmatites typically show a genetic linkage between the tectonic deformation and melt migration. We investigated this relationship in Olkiluoto (SW Finland) and identified four phases of ductile deformation, which are distinguished by the multiple folding phases, ductile shear events and cross-cutting features associated with pegmatitic leucosomes and/or a specific type of diatexitic migmatite with feldspar megacrysts. U–Pb LA-MC-ICPMS data on zircon cores and rims from migmatites and cross-cutting pegmatites indicate two distinct metamorphic events associated with melt generation and migration at 1.87–1.84 Ga and 1.82–1.78 Ga. These two migmatitic events suggest that the orogenic evolution of the area was long-lasting and characterized by slow cooling. The structural data and the age constraints presented in this paper support the idea of similar tectonic evolution and metamorphic environment in SW Finland and central E Sweden.

With the aid of an electronic universal testing machine and a scanning electron microscope, uniaxial compression tests and microscopic examinations of cemented tailings backfill with mixed fibers were carried out in order to investigate the impact of mixing steel fiber (SF) and polypropylene fiber (PF) on the static mechanical properties and failure mode. The findings demonstrate that; the inclusion of hybrid fiber has a substantial impact on the failure mode of the backfill; the CTB is mostly damaged by single bevel shear, displaying an evident brittle failure;the SP-FRB is primarily damaged by relatively minor secondary cracks due to the bridging and crack-resisting action of internal fibers; and the specimen is fractured as a whole,demonstrating an obvious ductile deformation; The addition of hybrid fiber can increase the filler s uniaxial compressive strength,but there is a maximum amount that should be used. The stress-strain curves of both CTB and SP-FRB contain four stages: pore compaction, linear elastic deformation, plastic yield,and post-failure. The results of the microscopic tests indicate that the initial pore size and number inside the filler are significant factors in its failure. Steel fiber and polypropylene fiber can both maintain high integrity inside the filler and prevent crack expansion through adhesion with the matrix and their own fatigue fracture, respectively. [ABSTRACT FROM AUTHOR]

Quantifying the timing and conditions of ductile deformation is essential for quantitative models of lithospheric deformation. Yet, directly constraining these variables and documenting how they change during a single deformation event remain difficult. We present titanite microstructural, zoning, trace‐element, and U‐Pb data from

A mechanism accommodating large strain in superplastic flow with elongation of 100%–300%, is described for fine‐grained calcareous shales deformed at temperature of 200–335°C and depths of 5–8 km up to slate schists in the Oisans massif, Western Alps, France. Using electron microscopy techniques on thin sections parallel to the principal finite strain axes, we show that the shape ratios of the slightly elongated grains (1.4–1.6), mainly calcite and quartz, do not match the finite strains recorded by the markers of the deformation (truncated belemnites, folded veins) in the maximum elongation and shortening plane (ratio 6.7) or in the maximum and minimum elongations plane (ratio 2.4). Consequently, a grain boundary sliding mechanism is required to explain the measured large finite strains. The most soluble minerals (quartz, calcite, dolomite, and albite), which represent about 95% of the rock, accommodate deformation by pressure solution grain boundary sliding whereas the least soluble minerals (muscovite, chlorite, Fe‐Ti oxides) act as indenters or are passively reoriented. Pressure solution is especially efficient in polymineralic rocks. Soluble minerals, which have been healed together in veins or fossils, are much more resistant to deformation and act as rigid objects. Models with idealized tessellation of hexagonal grains and creep laws derived from pressure solution indentation experiments provide deformation maps. We discuss the main parameters of this ductile deformation in the upper crust (thermodynamic conditions, strain rate, stress, distance of mass transfer) and show possible drastic decrease of mass transfer efficiency with decrease of stress and strain rate. Plain Language Summary: The formation of mountain ranges such as the Alps is associated with large strain flow of fine‐grained rocks even at low temperatures (200–335°C) and shallow depths (5–8 km). Such ductile behavior represents an aseismic alternative (without earthquakes) in highly deformed zones, so it is important to understand and model it in order to predict the mechanical behavior of actively deforming regions. However, the mechanism and the parameters of the deformation remain enigmatic. Relying on grain shape analyses derived from microscopy techniques, we demonstrate that the deformation is accommodated by grain boundary sliding with locally stress‐driven dissolution in zones that oppose grain sliding and re‐deposition in zones that are stress‐relaxed by this sliding. By comparison with laboratory experiments, we show that this ductile process may operate in fine‐grained rocks, at much lower stresses than required for seismic deformation. We establish flow laws that describe the relation between strain rate and the parameters of the deformation, such as thermodynamic conditions, stress, distance and characteristics of mass transfer along grain boundaries. We show that, at low differential stress and slow strain rate, diffusive mass transfer along grain boundaries could be much slower than when measured in laboratory experiments at high stress and strain rate. Key Points: During the Alpine orogeny, calcareous shales transformed to slate schists accommodated large ductile deformation at shallow depth (5–8 km)Microstructural studies reveal near‐equant fine grains and mass transfers implying grain‐boundary sliding mechanism in superplastic flowModeled deformation maps show that diffusive mass transfer properties may be slower in nature than in laboratory experiments [ABSTRACT FROM AUTHOR]

A continental-scale strike-slip shear zone frequently presents a long-lasting deformation and physical expression of strain localization in a middle to lower crustal level. However, the deformation evolution of strain localization at a small-scale remains unclear. This study investigated <10 cm wide shear zones developing in undeformed granodiorites exposed at the boundary of the continental-scale Gaoligong strike-slip shear zone. The small-scale ductile shear zones exhibit a typical transition from protomylonite, mylonite to extremely deformed ultramylonite, and decreasing mineral size from coarse-grained aggregates to extremely fine-grained mixed phases. Shearing sense indicators such as hornblende and feldspar porphyroclasts in the shear zone are the more significantly low-strain zone of mylonite. The microstructure and EBSD results revealed that the small-scale shear zone experienced ductile deformation under medium-high temperature conditions. Quartz aggregates suggested a consistent temperature with an irregular feature, exhibiting a dominated high-temperature prism slip system. Additionally, coarse-grained aggregates in the mylonite of the shear zone were deformed predominantly by dislocation creep, while ultra-plastic flow by viscous grain boundary sliding was an essential deformation process in the extremely fine-grained (∼50 µ m) mixed-phases in the ultramylonite. Microstructural-derived strain rates calculated from quartz paleopiezometry were on the order of 10−15 to 10−13 s−1 from low-strain mylonite to high strained ultramylonite. The localization and strain rate-limited process was fluid-assisted precipitation presenting transitions of compositions as hydrous retrogression of hornblende to mica during increasing deformation and exhumation. Furthermore, the potential occurrence of the small-scale shear zone was initiated at a middle-deep crust seated crustal condition dominated by the temperature-controlled formation and rheological weakening. [ABSTRACT FROM AUTHOR]

In this study, we investigated the Zicavo Metamorphic Complex (southern Corsica), which is part of the innermost Axial Zone of the Corsica-Sardinia Variscan belt. To better evaluate its geological and structural outline, a 1:5000 geological map, coupled with new structural/ microstructural and petrographic data, is presented. The complex is formed by three tectonic units, from bottom to top: (i) an Orthogneiss Unit, (ii) a Leptyno-Amphibolite Unit, and (iii) a Micaschist Unit. They are separated by ductile shear zones with a top-to-the-SE sense of shear. They underwent a polyphase deformation and polymetamorphic history, with a shortening stage in the amphibolite facies, responsible for the main structures and shearing, followed by an exhumation phase. [ABSTRACT FROM AUTHOR]

The mylonitic band of Rey Bouba Greenstone Belt (RBGB), oriented NE-SW that straddles between the Neoproterozoic batholite of the northern domain to the NW and the Adamawa-Yadé Paleoproterozoic domain to the SE, is a Neoproterozoic back-arc basin made of deformed volcanosedimentary rocks. A tectonic and microtectonic study of this basin was carried out under a petrographic and structural approach both in the field and in the laboratory. Structural analysis carried out in the study area allowed the identification of a complex four-phase D1–D4 polyphase deformation. The first three phases are ductile and the fourth essentially brittle. The D1 deformation phase, which is not very visible in the field, is characterized by a general flattening induced by a shortening oriented N-S in a pure shear regime leading to the development of S1 foliation and L1 mineral stretching line oriented E-W. The deformations D2 and D3, characteristics of sub-basins, are very intense and complex and implemented in two stages. The D2 deformation phase, essentially ubiquitous, is first a tangential tectonics associated with the formation of the composite S0/S2a/C2a surface and a single shear C2b of major direction NE-SW parallel to the Tcholliré-Banyo Shear Zone (TBSZ), C2b shear affecting the S2b foliation axial plane of the right P2b folds, synforms, and antiforms. NNE-SSW is the overall direction. D3 deformation also begins with the placement of the S0/S3a/C3a surface and the open folds P3a, then a simple shear, a translation in extensive speed materialized by the stretching lineation L3b, and ends with the ductilo-fragile deformation. The D4 deformation phase is represented by the syntectonic basic and acid veins oriented NE-SW and N-S to NNE-SSW, respectively, faults and breakages. [ABSTRACT FROM AUTHOR]

Shear strength and ductile deformation capacity of monolithic exterior shear keys play important roles on the seismic behavior of highway bridges. Improving the ductility of the shear key through reasonable design could effectively restrict superstructure displacement and minimize damage to pier columns. However, most existing studies primarily focus on evaluating the shear strength and damage mechanisms of shear keys, with limited attention given to analytical models for assessing ductile deformation capacity. To this end, this study proposes a method that combines quantile regression and machine learning techniques to predict the ductile deformation limit states of shear keys. The proposed numerical modeling method for shear keys is validated using the experimental data on lateral load-displacement curves. On this basis, Latin hypercubic sampling and joint simulation are utilized to establish the ductile deformation limit state database. The ductile deformation limit states of shear keys are characterized by their lateral displacements in three distinct damage states. The main influencing factors of each limit states are investigated by correlation analysis. Three quantile regression machine learning models are trained and constructed to conduct point and interval prediction for the ductile deformation limit states. All three models, particularly the Gaussian process quantile regression model, are proven to demonstrate exceptional prediction accuracy and uncertainty quantification. Experimental data validation confirms that these models outperform the prediction accuracy of existing simplified models. • Finite element modeling approach of shear keys is developed and validated. • Main factors of ductile limit states are investigated by correlation analysis. • The QR-ML techniques are adopted to establish probabilistic prediction models. • The established models are compared for point and interval prediction performance. [ABSTRACT FROM AUTHOR]

Revealing the ductile deformation mechanisms of ultra-hard brittle cubic silicon carbide (3C-SiC), as well as their correlations with microstructure evolution, are crucial for facilitating the ductile machinability of the ceramic material. In the present work, we report the formation of highly oriented high density stacking faults accompanied with suppressed amorphization and cracking in polycrystalline 3C-SiC in ultrasonic elliptical vibration-assisted diamond cutting, which contributes to significantly enhanced ductile material removal of the ceramic material compared to ordinary cutting. Specifically, characterizations of Raman spectroscopy on machined surface and cross-sectional transmission electron microscopy on subsurface, as well as molecular dynamics simulations of the two kinds of cutting processes, are jointly performed to elucidate the mechanisms of phase transformation and microstructure evolution that govern the ductile material removal of polycrystalline 3C-SiC under the vibration assistance. In particular, the formation mechanisms of highly oriented high density stacking faults emitted from grain boundaries are revealed. Current findings provide insights into the ductile deformation behavior of hard brittle ceramics enhanced by field-assisted deformation process. [ABSTRACT FROM AUTHOR]

In migmatitic environments the behaviour of the system is controlled by the generation and amount of the anatectic melt. Accordingly, migmatites typically show a genetic linkage between the tectonic deformation and melt migration. We investigated this relationship in Olkiluoto (SW Finland) and identified four phases of ductile deformation, which are distinguished by the multiple folding phases, ductile shear events and cross-cutting features associated with pegmatitic leucosomes and/or a specific type of diatexitic migmatite with feldspar megacrysts. U-Pb LA-MC-ICPMS data on zircon cores and rims from migmatites and cross-cutting pegmatites indicate two distinct metamorphic events associated with melt generation and migration at 1.87-1.84 Ga and 1.82-1.78 Ga. These two migmatitic events suggest that the orogenic evolution of the area was long-lasting and characterized by slow cooling. The structural data and the age constraints presented in this paper support the idea of similar tectonic evolution and metamorphic environment in SW Finland and central E Sweden. [ABSTRACT FROM AUTHOR]

Carbon fiber–reinforced polymer (CFRP) composites' performance on metallic tubular sections under compression was investigated in this work. The strength and stiffness of CFRP strips strengthened metallic samples were estimated. Fiber plies were used in the band layout having a width of 70 mm, and the distance between the adjacent strips was kept at 60 mm. CFRP strips were externally wrapped in the steel tube with 1, 2, and 3 layers. All test samples were tested in a column testing machine. Experimental results indicated that the addition of CFRP layers exhibited more strength, ductility, and stiffness compared to the unwrapped sample. The addition of three CFRP layers showed an average compressive strength improvement of up to 35% compared to the bare sample. [ABSTRACT FROM AUTHOR]

Nanomodified granular cement has higher strength and durability and has a denser microstructure than traditional concrete. Nanomaterials have surface effects, filling effects, and nucleation effects, which can improve the microstructure of concrete. In order to obtain cement materials with better performance, this article will mix nano-sulfur dioxide (SiO2), nano-silica (NS), and nano-titanium oxide (NT) into granular cement to study the types and dosages of nanomaterials and the effect of curing systems on the particles. The influence of cement abrasion resistance, by adding nanomodified materials of different particle sizes to the granular cement, the cement made on the 14th and 28th days after its setting has been tested for its compression resistance, ductility deformation, and frost resistance. The experimental results show that the ductility and deformation ability of concrete mixed with nanoparticles has a more obvious effect on the ductility deformation of 30 nm NS concrete, but the effect on 30 nm NT concrete is not as significant as that of 28d nano-concrete with the optimal amount of ductility deformation. It can be seen that 15 nm NS is 6.3% higher than 30 nm NS, and 30 nm NS is 11.1% higher than 30 nm NT. This shows that, in order to play the role of the nanomodified material particle cement, it is necessary to carefully study and judge different projects in order to play a better role. [ABSTRACT FROM AUTHOR]

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This paper provides an overview of research on core from Oman Drilling Project Hole BT1B and the surrounding area, plus new data and calculations, constraining processes in the Tethyan subduction zone beneath the Samail ophiolite. The area is underlain by gently dipping, broadly folded layers of allochthonous Hawasina pelagic sediments, the metamorphic sole of the Samail ophiolite, and Banded Unit peridotites at the base of the Samail mantle section. Despite reactivation of some faults during uplift of the Jebel Akdar and Saih Hatat domes, the area preserves the tectonic "stratigraphy" of the Cretaceous subduction zone. Gently dipping listvenite bands, parallel to peridotite banding and to contacts between the peridotite and the metamorphic sole, replace peridotite at and near the basal thrust. Listvenites formed at less than 200°C and (poorly constrained) depths of 25–40 km by reaction with CO2‐rich, aqueous fluids migrating from greater depths, derived from devolatilization of subducting sediments analogous to clastic sediments in the Hawasina Formation, at 400°–500°. Such processes could form important reservoirs for subducted CO2. Listvenite formation was accompanied by ductile deformation of serpentinites and listvenites—perhaps facilitated by fluid‐rock reaction—in a process that could lead to aseismic subduction in some regions. Addition of H2O and CO2 to the mantle wedge, forming serpentinites and listvenites, caused large increases in the solid mass and volume of the rocks. This may have been accommodated by fractures formed as a result of volume changes, mainly at a serpentinization front. Plain Language Summary: This paper reports initial results from study of core from Oman Drilling Project Hole BT1B and the surrounding area. It provides insights into subduction zone processes, including large fluxes of recycled CO2 from subducting sediments into the leading edge of the mantle wedge, and surprisingly low temperature ductile deformation at less than 200°C. Recycling of CO2 via carbon mineralization in the hanging wall of subduction zones may produce an important, lithospheric reservoir in the global carbon cycle. Ductile deformation of serpentinite, and during or after transformation of peridotite to listvenites (mixtures of carbonates and opal or quartz) could explain aseismic subduction atop some subduction zones. Key Points: The area at and around OmanDP Hole BT1B preserves nearly flat‐lying tectonic "stratigraphy" of the basal thrust of the Samail ophioliteRecycling of CO2 from subducting sediment into the mantle wedge produced listvenites (carbonated peridotite) at <200°CSubduction beneath the ophiolite was accommodated, in part, by ductile deformation of serpentinite and listvenite at <200°C [ABSTRACT FROM AUTHOR]

We report contrasting pressure–temperature–time (P–T–t) paths of migmatites developed in the highest‐grade metamorphic zone (Grt–Crd zone) and the contact metamorphic zone (Crd–Kfs zone) of the Mikawa area, Ryoke belt, southwest Japan to discuss the complex P–T–D–t evolution of the middle crust that experienced pulsed granitoid intrusions. In the Grt–Crd zone, sillimanite‐grade high‐T metamorphic condition prevailed from ca. 97 to 87 Ma, followed by cooling to ~500 °C, ~4 kbar. The intrusion of gneissose granitoids below the Grt–Crd zone isobarically reheated the Grt–Crd zone rocks again to the sillimanite‐grade high‐T condition at ca. 84 Ma. This was followed by ca. 71–70 Ma contact metamorphism. Ductile deformation that formed and folded the foliation of migmatites started before ca. 89 Ma and continued at least until ca. 84 Ma in the Grt–Crd zone. On the other hand, ca. 74 Ma age of the Crd–Kfs zone migmatite developed around the Inagawa Granodiorite in addition to ca. 70 Ma age of a syn‐tectonic pegmatite vein revealed that the intrusion of "75–69 Ma granitoids" caused partial melting and locally triggered low‐strain ductile deformation in their contact aureoles. Comparison with other areas of the Ryoke belt suggests that plutono‐metamorphic evolution of the Mikawa and Aoyama areas are similar with each other in that ca. 80 Ma reheating events (i.e., contact metamorphism) are observed, while absence of separate reheating event postdating peak metamorphism in the Yanai area is a rather uncommon feature in the Ryoke belt. [ABSTRACT FROM AUTHOR]

Brittle KH 2 PO 4 (KDP) crystal is difficult-to-machine because of its low fracture resistance whereby brittle cracks can be easily introduced in machining processes. To achieve ductile machining without any cracks, this type of materials is generally processed by some ultra-precision machining techniques at ambient temperature with nanoscale material removal, yielding low machining efficiency and high processing cost. Recently, thermal-assisted techniques have been used to successfully facilitate the machining of some difficult-to-machine materials, like superalloys, but little effort has been made to explore whether the temperature effect can contribute to the ductile machinability of brittle materials yet. Thus, the aim of this study is to figure out the specific role of temperature in the deformation behaviours of brittle KDP crystal by nano indentation/scratch methods. It is found that compared with those at ambient temperature (AT, i.e. 23 °C), the hardness and Elastic modulus of KDP crystal at elevated temperature (ET, i.e. 160 °C) decrease substantially by 21.4% and 32.5%, respectively, while the fracture toughness increases greatly by 15.5%, implying a higher ability of ductile deformation at ET. Meanwhile, the scratch length within ductile removal has been identified to be extended more than 4 times by increasing temperature from AT to ET. Both the quantity and size of brittle features (e.g., cracks and chunk removal) show a reducing trend with the increase of temperature. To uncover the underlying mechanism of this phenomenon, an updated stress field model is proposed to analyze the scratch-induced stress distribution by considering the evolution of material property at various temperature. These presented results are significant for the future design of specific thermal-assisted processing techniques for machining brittle materials efficiently. [ABSTRACT FROM AUTHOR]

The thickness of the brittle lithosphere—the outer portion of a planetary body that fails via fracturing—plays a key role in the geological processes of that body. The properties of both a planet and its host star can influence that thickness, and the potential range of those properties exceeds what we see in the Solar System. To understand how planetary and stellar parameters influence brittle lithospheric thickness generally, we modeled a comprehensive suite of combinations of planetary mass, surface and mantle temperature, heat flux, and strain rate. Surface temperature is the dominant factor governing the thickness of the brittle layer: smaller and older planets generally have thick brittle lithospheres, akin to those of Mercury and Mars, whereas larger, younger planets have thinner brittle lithospheres that may be comparable to the Venus lowlands. But certain combinations of these parameters yield worlds with exceedingly thin brittle layers. We predict that such bodies have little elevated topography and limited volatile cycling and weathering, which can be tested by future telescopic observations of known extrasolar planets. Plain Language Summary: The outer layer of a rocky planetary body is generally rigid and behaves in a brittle manner. The thickness of this layer is important in governing numerous aspects of that body's geological character, including whether it can support plate tectonics and even retain habitable conditions at the surface. Factors inherent to the planet, such as size, interior temperature, composition, and even climate affect the thickness of this outer layer, but so too do factors specific to the host star, including how luminous and far away it is. We ran a large set of computer models to see how various combinations of planetary and stellar properties influence the thickness of a planetary body's outer layer. Our models predict that worlds that are small, old, or far from their star likely have thick, rigid layers but, in some circumstances, planets might have an outer brittle layer only a few kilometers thick. These worlds, which we call "eggshell planets," might resemble the lowlands on Venus, and we suggest that at least three such extrasolar planets are already known. We propose that these planets be examined with planned and future space telescopes to test if our models are correct. Key Points: We modeled the effects of planetary mass, age, and surface temperature on brittle lithospheric thicknessSurface temperature is the primary determinant of the thickness of brittle exoplanet lithospheresCertain combinations of these parameters yield "eggshell planets"—worlds with ultra‐thin brittle lithospheres [ABSTRACT FROM AUTHOR]

The Griggs apparatus is a triaxial piston-cylinder instrument used in deformation experiments of geological material at temperatures up to 1200 °C and confining pressures up to 3 GPa. Currently, most Griggs apparatuses can carry out deformation experiments only at constant displacement rate. As a result, few experimental studies have explored other geologically-relevant deformation scenarios. We present supplemental instrumentation and software that enables Griggs apparatus users to carry out deformation experiments at controlled differential stress conditions. The add-on instrument includes a feedback loop mechanism that regulates the imposed differential stress on the sample and a data acquisition system that allows for real-time display of mechanical data in units of stress and displacement. We demonstrate the application of this instrument through two deformation experiments at constant differential stress on (1) an aluminum cylinder at room temperature and (2) a quartz aggregate at 850 °C, both at ~1 GPa confining pressure. These experiments show that the instrument can reliably control the imposed differential stress on the sample throughout the deformation. Applications of the instrument can be extended beyond constant differential stress to more sophisticated stress paths (e.g., stress pulse, stress ramp) or to maintain true strain rates by accounting for anticipated geometrical changes in the sample during deformation.

We present a flow law for dislocation‐dominated creep in wet quartz derived from compiled experimental and field‐based rheological data. By integrating the field‐based data, including independently calculated strain rates, deformation temperatures, pressures, and differential stresses, we add constraints for dislocation‐dominated creep at conditions unattainable in quartz deformation experiments. A Markov Chain Monte Carlo (MCMC) statistical analysis computes internally consistent parameters for the generalized flow law: ε˙ = AσnfH2Ore−(Q+VP)/RT. From this initial analysis, we identify different effective stress exponents for quartz deformed at confining pressures above and below ∼700 MPa. To minimize the possible effect of confining pressure, compiled data are separated into "low‐pressure" (<560 MPa) and "high‐pressure" (700–1,600 MPa) groups and reanalyzed using the MCMC approach. The "low‐pressure" data set, which is most applicable at midcrustal to lower‐crustal confining pressures, yields the following parameters: log(A) = −9.30 ± 0.66 MPa−n−r s−1; n = 3.5 ± 0.2; r = 0.49 ± 0.13; Q = 118 ± 5 kJ mol−1; and V = 2.59 ± 2.45 cm3 mol−1. The "high‐pressure" data set produces a different set of parameters: log(A) = −7.90 ± 0.34 MPa−n−r s−1; n = 2.0 ± 0.1; r = 0.49 ± 0.13; Q = 77 ± 8 kJ mol−1; and V = 2.59 ± 2.45 cm3 mol−1. Predicted quartz rheology is compared to other flow laws for dislocation creep; the calibrations presented in this study predict faster strain rates under geological conditions by more than 1 order of magnitude. The change in n at high confining pressure may result from an increase in the activity of grain size sensitive creep. Plain Language Summary: At conditions present in the middle and lower crust, rocks generally deform by ductile processes, instead of brittle fracture which is dominant closer to the Earth's surface. As a volumetrically dominant mineral in many crustal rocks, quartz is commonly thought to control the overall strength of the crust. Much of our understanding of how quartz behaves comes from deformation experiments; but to produce the same type of deformation we observe in middle‐ or lower‐crustal rocks, experiments must be performed at conditions different from what natural rocks experience. The difference poses a potential issue in extrapolating experimental results to natural conditions. Here, we integrate mechanical data from deformation experiments and naturally deformed rocks to arrive at a quantitative relationship that relates material properties and deformation conditions to the rate at which quartz deforms. Because we add constraints at deformation conditions not attainable in experiments, we likely produce a more accurate representation of ductile quartz behavior. Our results indicate that quartz‐rich rocks in the middle and lower crust deform at least an order of magnitude faster than previous predictions, which has important implications for crustal strength, geodynamic modeling, and potentially for the loading of seismically active faults. Key Points: We use Bayesian statistical analysis on compiled rock deformation data to produce a flow law for dislocation creep in wet quartzThis analysis indicates a low sensitivity to water fugacity, while other parameters are broadly consistent with existing valuesUnder geological conditions, wet quartz aggregates deform faster than is predicted by existing flow laws [ABSTRACT FROM AUTHOR]

Abstract Sheath folds recognized on kilometer scale are rare and only described in salt tectonics in seismic data. Here, we present mega‐sheath folds spectacularly imaged in a 3‐D seismic survey in the seismic basement flooring the hyperextended Liwan subbasin in the northern margin of the South China Sea. The sheath folds show eye structures delimited by anastomosing discontinuities. The axial planes of the sheath folds are subparallel to a rift‐related, extensional detachment surface separating hyperextended seismic basement from the syn‐rift sedimentary sequence. The sheath folds as well as the anastomosing discontinuities formed during hyperextension by ductile shearing of the forearc inherited and prestructured metasediments. The ductile shearing eventually resulted in the metasediments derived from midcrust unroofed at the footwall of an extension detachment fault. The discovery of mega‐sheath folds and ductile deformation within the basement conflicts with the general assumption that hyperextended domains are in the brittle field. The new seismic observations show the importance of forearc inherited, prestructured anisotropic basement controlling the crustal rheology during hyperextension.

Sheath folds recognized on kilometer scale are rare and only described in salt tectonics in seismic data. Here, we present mega‐sheath folds spectacularly imaged in a 3‐D seismic survey in the seismic basement flooring the hyperextended Liwan subbasin in the northern margin of the South China Sea. The sheath folds show eye structures delimited by anastomosing discontinuities. The axial planes of the sheath folds are subparallel to a rift‐related, extensional detachment surface separating hyperextended seismic basement from the syn‐rift sedimentary sequence. The sheath folds as well as the anastomosing discontinuities formed during hyperextension by ductile shearing of the forearc inherited and prestructured metasediments. The ductile shearing eventually resulted in the metasediments derived from midcrust unroofed at the footwall of an extension detachment fault. The discovery of mega‐sheath folds and ductile deformation within the basement conflicts with the general assumption that hyperextended domains are in the brittle field. The new seismic observations show the importance of forearc inherited, prestructured anisotropic basement controlling the crustal rheology during hyperextension. Plain Language Summary: A wealth of research has established the classic crustal model with a strong brittle upper crust and a weak ductile lower crust. The styles of deformation depend on rheological and mechanical properties of the materials and generally exhibit brittle faulting in the upper crust and ductile flow in the lower crust, respectively. However, remarkable changes in the crustal rheology and mechanics can occur in strongly inherited, complex geological settings, which up to date have not been well established. In this study, we present and discuss the occurrence of mappable sheath folds generated under high ductile shear strain in metasediments in the basement, and we decipher the questions of when, how, and in what conditions these structures formed. Our results demonstrate that these mega‐sheath folds formed within a forearc inherited anisotropic basement, and the rocks are derived from midcrustal levels. During hyperextension, they were unroofed in the footwall of a major extensional detachment. Ductile deformation and shearing became responsible for the extreme thinning of the crust. Key Points: Sheath folds in seismic basement flooring the Liwan subbasin developed weak, forearc inherited anisotropic metasedimentsMetasediments derived from midcrust levels were unroofed in the footwall of an extensional detachment fault during hyperextensionCombination of a pure shear and a simple shear regime accounts for the extreme thinning of the crust underneath the Liwan subbasin [ABSTRACT FROM AUTHOR]

Abstract We have analyzed the spatial variation in coda Q in the northeastern part of a high strain rate zone, the Niigata–Kobe Tectonic Zone (NKTZ), to investigate the cause of the high strain rate by correlating coda Q with the differential strain rate and the S-wave velocity. The spatial distributions of coda Q in the 2–4 and 4–8 Hz frequency bands are found to be negatively correlated with the differential strain rate. Coda Q in the 2–4 Hz frequency band is correlated spatially with the S-wave velocity at a 25 km depth, as has been reported previously. We also find a positive correlation between the perturbation of the S-wave velocity at a 10 km depth and coda Q in the 4–8 Hz frequency band, implying that the spatial distribution of coda Q in this frequency band is mainly attributed to the heterogeneity of the upper crust. This feature is different from that of the central part of the NKTZ reported previously, which indicates a difference in the cause of the high strain rate. Therefore, we suggest that the high deformation rate in the upper crust, which is characterized by a thick sediment basin, as well as that in the ductile lower crust, contributes to the generation process of the high strain rate on the surface in the northeastern part of the NKTZ. Graphical abstract .

The self-developed TRTP-2000 high temperature and high pressure deformation experimental system is used to test the deformation of coal under sub-high temperature and high pressure deformation conditions. Micro-Raman and Micro-FTIR in-situ test methods are used to observe the microscopic deformation of coal after deformation. The typical brittle and ductile deformation points in the domain are analyzed for macromolecular structure. The results show that with the decrease of strain rate, the toughness deformation phenomenon in the sample develops gradually, which promotes the increase of secondary structural defects and the disorder of molecular structure. The brittle deformation is produced by the coupling of mechanical force and frictional heat. The oxygen-containing functional groups of coal macromolecules break and fall off with side chains, resulting in increased disorder and secondary structural defects. The ductile deformation acts on the coal macromolecular structure through the continuous accumulation of strain energy, due to the difference in strain rate. The deformation time changes. The high strain rate (≧1×10-6) toughness deformation leads to an increase in the total amount of aromatic carbon, a decrease in molecular structure disorder, and a relative decrease in secondary structural defects; a deformation at a low strain rate (=2×10-7) There is sufficient time to accumulate a large amount of strain energy in the process, which leads to dislocation slip of the aromatic layer. The accumulation of dislocations causes the aromatic ring to disintegrate, the total amount of aromatic carbon is relatively reduced, and the secondary structural defects are increased. [ABSTRACT FROM AUTHOR]

Coal organic macromolecular structure can be significantly altered by tectonic stress, but such macromolecular models are seldom reported. Here, based on the ultimate analysis, FT-IR, XPS, and 13C NMR results, three molecular models of primary coal (P1) and TDCs (the brittle coal model B2 and ductile coal model D3) within periodic boundary conditions were constructed through the molecular mechanics (MM) and molecular dynamics (MD) calculation methods. By comparing the morphology characteristics of the above three models, the crystal parameters decrease with the increasing deformation intensity, which leads to a tighter configuration. Bridge bonds are easier to be stretched and even broken up within deformed coal, which can furtherly crack the coal molecules into several smaller segments. Oxygen functional groups and methyl can be lost by the deformation on coal, which leads to an increase of the disorder units within coal molecules. On the one hand, the ductile deformation increases the condensation degree of the aromatic layers through promoting the small disorder units (viz. CO) embed into the secondary structural defects. On the other hand, it can also improve the order degree and the stacking degree of aromatic layers. By comparative analysis, the evolution path of tectonically deformed coal molecules is furtherly proposed. The ultra micropore volumes of three models are several orders of magnitude larger than the pore volume within the range of 2–50 nm, indicating that ultra micropores are important storage spaces for excess methane resulting in coal and gas outburst. [ABSTRACT FROM AUTHOR]

The widespread migmatites in the northwestern part of the Sulu Orogen, China, indicate regional anatexis that is of great significance when discussing the tectonic evolution of this continental orogenic belt. Cathodoluminescence (CL) images, U–Pb ages, and in situ trace element compositions of zircons from four pegmatite veins within these migmatites provide clear evidence for the nature of the post-collisional evolution of the Sulu Orogen. The inherited zircon cores reveal that the protoliths of the migmatites were middle Neoproterozoic magmatic rocks (810–620 Ma) of the South China Block. The protoliths underwent two partial melting events. The mantle domains of the inherited zircons record a Late Triassic (222.0–204.0 Ma) partial melting event that occurred during the exhumation and retrograde metamorphism, after ultrahigh-pressure (UHP) metamorphism. Subsequent newly grown zircons record a Middle–Late Jurassic to Early Cretaceous (164.1–125.5 Ma) anatexis event, indicating that the late Mesozoic anatexis started before ca. 164.1 Ma, reached a peak at ca. 152.1 Ma, and ceased at ca. 125.5 Ma. Combined with previous results of studies on the Sulu orogen, the late Mesozoic anatexis suggested that the thickened crust of the Sulu Orogen had started to become unstable before 164.1 Ma. The duration of ~164.1–137 Ma corresponds to a period of transition in the tectonic regime of the Sulu Orogen, enabling the early high-temperature ductile deformation. After ca. 137 Ma, the tectonic regime was fully transformed into extension and the Sulu Orogen underwent rapid thinning and collapse, thus leading to the late medium–low temperature ductile deformation (137–121 Ma) and laying the foundations for the large-scale magmatic emplacement during the late Early Cretaceous (127–115 Ma). These two partial melting events together promoted the rapid exhumation of the Sulu UHP rocks. [ABSTRACT FROM AUTHOR]

New detailed geological/structural mapping coupled with microstructural investigations and amphibole chemistry analyses are used to elucidate the enigmatic tectonic evolution of the Makrotantalo nappe on northern Andros (Aegean region). On the basis of the new geological map, we re-evaluate the structural position of samples with previously published metamorphic ages to show that the Makrotantalo nappe has been affected by the early Eocene high-pressure (HP) metamorphism. Therefore, the Makrotantalo nappe is an integral part of the Cycladic Blueschist Unit (CBU). The early, main ductile deformation phase recognized in the mapped area, is associated with the emplacement of the Makrotantalo nappe over the North Cyclades nappe at deep subduction levels during early Eocene. The subsequent deformation phase occurred at the middle Eocene–Oligocene synchronous with the decompression of blueschist rocks from the stability field of glaucophane to that of actinolite. During this phase, the nappe pile was folded by map-scale folds, which were locally transposed by ductile shear zones. These shear zones were related with NE-directed oblique thrusting and, locally, either restacked the nappe pile or reworked the early nappe contact. Our results in combination with previous studies in the northern Cyclades show that the top-to-the-NE shearing was dominant at a large part of the CBU during exhumation. Opposite, SW-directed shearing was restricted at the upper structural levels of the CBU. We suggest that the observed spatial variation in shear sense is compatible with NE- rather than SW-directed ductile extrusion of the CBU. [ABSTRACT FROM AUTHOR]

The study on deformation characters of the Liaohe Group, exposed in eastern Liaoning Province, NE China, provides a key constraint on the tectonic evolution of the Palaeoproterozoic Liao–Ji active belt in the eastern part of the North China Craton (NCC). In this paper, the deformation pattern and mechanism of the Dashiqiao Fm. from Liaohe Group in Hupiyu area have been systematically studied. The present results show that the structure of the investigated Dashiqiao Fm. exhibits a SW bedding‐parallel thrust shearing which is dominated by simple shearing. Simultaneously, S‐SL tectonites were formed under directional flattening. The deformed quartz grains show obvious dislocation slip which is mainly controlled by the low temperature system of the basal slip system, while calcites mainly develop in low temperature with twin slip. Based on microstructural analysis coupled with fabric features, we estimated that the strain rate is 10−12.78–10−8.32 s−1 under the deformation temperature of 350–400°C with a differential stress of 27.3–44.9 MPa. Our macrostructural–microstructural investigation together with previous researches indicates that the Liaohe Group suffered a bedding‐parallel sliding with top‐to‐outside away from the granite body in the core of Hupiyu anticline, corresponding to the uplift of the Hupiyu granite in the early extensional stage. Subsequently, the Hupiyu area suffered SW–NE compression which resulted in the overturn of the southern limb of the Hupiyu anticline and the top‐to‐SW thrusting. [ABSTRACT FROM AUTHOR]

Building upon the two‐phase and grain damage theory, we propose a new formulation allowing to track the evolution of phase mixing/segregation during ductile deformation of a two‐phased aggregate. Our model is based on a set of variables characterizing a rock texture: the mean grain sizes and the phase proportion. During ductile deformation, activation of different micromechanical processes impacts the aggregate texture. Dislocation and diffusion creep are the two main deformation processes considered. We only account for the effect of Zener pinning in slowing down grain growth and allow for active grain‐size reduction mechanisms in the diffusion creep domain. For this purpose, an equation is proposed to track the phase mixing evolution during ductile deformation. Numerical application using anorthite rheology shows that any grain reduction mechanisms that could be active in the diffusion creep regime requires a very high partition fraction in order to reach the grain size predicted by the feldspar piezometer. Application of this model to gabbroic composition, relevant for the ductile crust, demonstrates that the strong coupling between phases grain sizes and interface evolution results in steady‐state grain sizes far below the field boundary. This effect is coeval with an important increase of mixing between the two phases. In addition, accounting for the phase mixing results in a drop of the global aggregate stress during deformation. This model allows for further comparison of mylonitized textures evolution with natural shear zones at the local and regional scales. Plain Language Summary: In the Earth lower crust, the rocks deform by slow creep instead of breaking due to high temperature and pressure. Observations of natural material deformed in such conditions show that deformation concentrates on narrow‐banded structures. At small scales (1 cm to 1 μm), these shear bands generally present a very fine mean crystal size and a very good mixing of the minerals. These features are characteristic of deformed rocks, but their origins and consequences on geological structures at larger scales (1 m to 100 km) are yet to be fully understood. In this study we propose a physical model (a mathematical representation of reality) that allows to represent a rock consisting of two minerals, their mean crystal sizes and proportions and the quality of their mixing. This is based on parameters constrained experimentally for each pure mineral. Using this model, we are able to track the evolution of these rocks microscopical characteristic and their consequences on the rock strength during deformation. Eventually, the results allow us to refine our understanding of the implied processes by comparing the computed variables to measures performed on rock samples. The physical equations proposed could then be used to model the rock strength in geodynamical models at larger scales. Key Points: The presented model adresses the evolution of mylonite texture during ductile deformationThis model tracks the role of creep mechanisms on the mixing state evolution of the aggregateAn effective viscosity that depends on the mixing degree of the two‐phase increases stress weakening [ABSTRACT FROM AUTHOR]

A mechanical tough polylactic acid (PLA) that substantially retains its stiffness and transparency was created through reaction with a polyrotaxane derivative. A graft polyrotaxane (GPR), composed of a linear Polyethylene glycol backbone threaded with cyclodextrins bearing grafted poly(ε-caprolactone), was bonded to the hydroxyl end-groups of PLA with hexamethylene diisocyanate (HDI), which then solidified to form a PLA-bonded GPR that was distributed throughout the PLA matrix. The addition of 5 wt% GPR resulted in a seven-fold increase in Izod impact strength and a three-fold increase in fracture elongation, with only an 11% loss of stiffness; the transparency was comparable to neat PLA. Electron microscopy revealed that HDI facilitated the dispersal of GPR in the PLA matrix and avoided the sea-island phase-separated structure observed in the PLA/GPR blend devoid of HDI, and that the homogenized structure led to ductile deformation. A GPR content of only 5 wt% efficiently increased PLA-matrix-chain flexibility. [ABSTRACT FROM AUTHOR]

Abstract In order to assess the effect of shape preferred orientation (SPO) of halite grains on deformation of rock salt, ductile plane strain deformation experiments have been conducted. Natural halite cubes with and without an SPO from the Asse mine of northern Germany were deformed at 345 °C, atmospheric pressure and a strain rate of ~10−7 s−1. The SPO was oriented at different angles (ß = 0°, 45° and 90°) to the main shortening direction, Z. The sample is confined in the Y direction and can freely move to the principal stretching direction, X. Most of the strain was accommodated by dislocation creep. The qualitative analysis of the stress-strain data shows the clear influence of the SPO on the mechanical data. At a shortening strain of ca. −10%, the samples with β = 0° and 45° are weaker than the samples without an SPO. In contrast, the sample with β = 90° is stronger than the samples without an SPO. A new SPO is formed in all samples with the long axis of the grain shape fabric being subparallel to the principal stretching axis, X. At these larger shortening strains, the samples show similar strength, with an exception of the 90° oriented sample that is still stronger than the samples without an SPO. Even though the experimental set up has to be improved to obtain quantitative results on the influence of SPO on mechanical strength of rock salt, the results show that the SPO of rock salt likely has to be taken into account when building a repository for nuclear waste and could have an effect on the stability of caverns. Highlights • Coarse-grained rock salt samples with and without SPO were experimentally deformed • Until ε z of −10%, samples with ß = 0° and 45° are weaker than samples without SPO • Until ε z of −10%, sample with ß = 90° is stronger than the samples without an SPO • At ε z > −10% strengths are similar, new SPO forms with long grain axis parallel to X [ABSTRACT FROM AUTHOR]

Raman spectroscopy, applied to the carbonaceous matter (CM) present in fault zones, is a potentially powerful tool to aid in the reconstruction of slip conditions, provided the respective effect of heating and strain can be disentangled. For this purpose, we have carried out static heating and deformation experiments on low-grade sediments containing disseminated CM particles and tracked the evolution of CM crystalline ordering (crystallinity) using Raman spectroscopy. Heating at high pressure (200 MPa), at varying temperatures (500 to 800 °C) and durations (3 to 1080 h) resulted in an increased crystallinity, which was observed by an increase in the intensity ratio of the Disordered Band over the Graphite Band (Intensity Ratio R1 parameter) of the Raman spectra. The experimental relationship between R1, T and duration was compiled into a law of evolution, which was then used to design the deformation experiments. Experiments were performed in a Paterson rig at 150 MPa or in a Griggs-type rig at 1 GPa. We observed two types of deformation microstructures: (1) purely brittle ones, such as breccia along slip planes and (2) ductile ones, such as foliated layers, resulting from grain reorientation and comminution along with dissolution precipitation. In all deformation microstructures, an increase in R1 is visible and interpreted to be the result of higher crystallinity of carbonaceous particles. Such increase is negligible in breccia, but is significant, up to 40%, in ductile deformation zones. The slow strain rates prevailing in ductile deformation prevented any local temperature increase, therefore the increase in crystallinity of the CM can be solely attributed to deformation. Thus, in natural fault zone, the increased crystallinity of CM reported in the literature and interpreted to be the result of frictional heating during earthquakes might rather be the result of strain localization without transient temperature increase. • Using Raman we studied carbonaceous matter (CM) evolution with strain and temperature. • Kinetics of evolution were derived from high-pressure experiments of static heating. • High-pressure deformation experiments show the large effect of strain on Raman of CM. • Raman anomalies in natural fault zones can result from strain and not temperature. [ABSTRACT FROM AUTHOR]

Abstract The relationships between deformation and fluid flow have been investigated in the Paleozoic basement of an isolated horst of the Catalan Coastal Ranges. A structural, petrological and geochemical study has been performed in a complex fracture network that resulted from a long-lived tectonic history (from Carboniferous to Miocene). Nine fracture types, developed from a ductile regime in the greenschist facies to a shallow brittle regime, have been characterized in order to establish P, T and fluid compositions during the evolution of the horst. Syn-cleavage and late-cleavage quartz veins (qtz 1 -chl 1 ± mu and late qtz 2 -chl 2 -dol 1) formed during the Hercynian ductile deformation. These minerals precipitated from metamorphic fluids, possibly evolved from seawater, at temperatures between 240 and 340 °C. En-echelon albite vein arrays (ab-qtz 3 -chl 3 ± ti-an) and NE-SW normal faults generating breccias mark the change from ductile to brittle, from compression to extension and from a closed to an open hydrologic regime. This paragenesis precipitated from the mixing of metamorphic and magmatic fluids at temperatures between 180 and 290 °C during the early Permian extension. Dolomite veins (dol 2 -chl 4 -qtz 4), precipitated at 210–280 °C from the mixing of previous fluids with hypersaline oxidizing external brines, possibly during the late stage of the early Permian extension. Reverse faults and calcite veins (Cc1-ba) formed either during the Paleogene compression or during the Langhian to early Serravallian minor compression. Calcite and barite precipitated from meteoric or marine waters in an open hydrological system at temperatures below 50 °C. The Miocene extension is represented by NE-SW normal faults with fault gouges and NNW-SSE normal faults cemented by calcite 2 that precipitated at temperatures below 50 °C from meteoric fluids in an open basin-scale hydrological system. The studied horst was part of a relay zone between two segments of the NNW-SE Llobregat fault during the early Permian, explaining the high fracture density and the fast upflowing of hydrothermal fluids at that time, thus controlling the development of albite veins exclusively in this area. Highlights • Ductile to shallow brittle deformation structures recorded in crystalline basement. • Mineral paragenesis are controlled by the host rock, fluid origin, fO 2 and T. • A coupled fluid flow system (channelized and pervasive) occurs during metamorphism. • An Early Permian relay zone generates a dense network of hydrothermal veins. • During the Miocene, shallow deformation linked to an open basin-scale fluid flow occurs. [ABSTRACT FROM AUTHOR]

All the minerals in a rock contribute to its anisotropy of magnetic susceptibility (AMS). In weakly magnetic sedimentary rocks, the strongest contributors are the paramagnetic minerals, predominantly represented by clay minerals, together with the ferrimagnetic minerals that are typically magnetite and/or maghemite. In contrast, ferrimagnetic minerals solely control the anisotropy of magnetic remanence (AMR). An investigation of both AMS and AMR can therefore help distinguish among the deposition, diagenetic and deformation histories of the paramagnetic and ferrimagnetic minerals in the same rock specimen. We present a test case from relatively weakly deformed Intra-Carpathian Palaeogene sandstones (Skorušina Hills, Slovak Republic) where AMR and AMS fabrics generally coaxial yet also exhibited notable differences. In particular, AMR foliations were more readily deflected away from the bedding plane, perpendicular to the maximum stress axis, than the AMS foliations. These factors are interpreted in terms of higher sensitivity of the ferrimagnetic minerals to ductile deformation than that of the paramagnetic clay minerals. [ABSTRACT FROM AUTHOR]

The Liaoyuan Terrane (LT) in NE China formed as a result of accretion during the final closure of the Paleo-Asian Ocean between the North China and Siberian cratons. However, the timing of the deformation and the location of the eastern LT remain controversial. Here we present structural data, zircon U–Pb age dating, and Hf isotopic data to constrain the kinematics and timing of deformation, and the southern boundary of the eastern LT in relation to the NE–SW-striking Yilan–Yitong Fault (YYF), one of two branches of the continental-scale Tan–Lu Fault Zone in NE China. Pre-Jurassic rocks in the eastern LT were widely involved in ductile deformation within WNW–ESE-striking thrust belts. The microstructures in these shear zones indicate a top-to-the-SSW sense of shear and deformation temperatures of 450–500 °C. The northern margin of the North China Craton (NCC) was also affected by the NNE–SSW contraction, as shown by similar ductile deformation in the Archean gneisses and WNW–ESE trending folds in the Mesoproterozoic sedimentary cover. The ages of crystallization in deformed and undeformed igneous rocks in the LT constrain the deformation to an interval between 241 and 193 Ma. U–Pb dating of zircons in syn-kinematic migmatitic rocks indicates an age of 234–229 Ma for the deformation. We consider this Middle Triassic age to represent the final closure time of the Paleo-Asian Ocean along the eastern LT, and this timing is consistent with the eastwards scissor-style closure model. Lithological variations, zircon age spectra, ε Hf ( t ) values, and model ages confirm the eastward extension of the LT across the YYF. The data constrain the boundary between the LT and NCC to be roughly along the Liao River to the west of the YYF, and along the northern edge of the exposed Archean gneisses to the east. The boundary follows the Bayan Obo–Chifeng–Kaiyuan Fault, which was active as a thrust (thrusting of material to the SSW) during the Middle Triassic orogeny. The newly determined boundary location indicates a 35 km sinistral displacement along the YYF. [ABSTRACT FROM AUTHOR]

The basement surface and sediments of the Kochkor basin have been studied by structural geological and geophysical methods. The work included high-resolution mapping of the southern basin margin, with a focus on Cenozoic basin stratigraphy, structural unconformities, basement/sediment contacts, and latest deformation (folds, fractures, and faults). Magnetotelluric (MT) soundings provided insights into basin and basement structure, especially important in the poorly exposed eastern flank of the basin margin. The sections across the southern margin of the basin based on geological and geophysical data reveal deformation in both the basement and the sediments. Deformation in sediments shows up as folding, conformal peneplain surfaces, large faults, low-angle detachment faults, and related thrust-fold belts. Thrusting in sediments is inferred to result from cataclastic flow and mass redistribution in disintegrated basement granites. With this mechanism, the total amount of thrusting in the central part of the basin can exceed the convergence of the basin sides. [ABSTRACT FROM AUTHOR]