Dislocation Zone Research Articles

The Leba Ridge–Riga–Pskov Fault Zone – a major East European Craton interior dislocation zone and its role in the early Palaeozoic development of the platform cover

The Leba Ridge–Riga–Pskov Fault Zone – a major East European Craton interior dislocation zone and its role in the early Palaeozoic development of the platform cover

Deep structure of South Kamchatka according to geophysical data

Differences have been discovered in the deep structures of North and South Kamchatka, which raises a question about a boundary between these regions. This problem has been studied on the basis of the seismologic, inverse seismic tomographic (P-waves) and geoelectrical data obtained in recent years, as well as the information on magnetometry, gravimetry, tectonics and magmatism of the study area. Comprehensive analysis of the geological and geophysical data shows differences in the structure of the crust and upper mantle in North and South Kamchatka and common features of the deep structures of South Kamchatka and the Kuril Islands. A presumed boundary between North and South Kamchatka is related to the zone of transverse deep faults crossing the peninsula. It is evidenced by P-wave velocity anomalies at different levels of the lithosphere. This fault zone is associated with a change in the geometry and strike of the high-velocity focal layer, and reflected in the modern tectonic plan as the Petropavlovsk-Malkinsky zone of transverse dislocations. In this zone, the Avacha-Koryak group of modern volcanoes is also NW-oriented. We propose a geoelectric model showing the depths along the profile constructed across the zone. In its deep part, the model includes sub-vertical anomalies of increased electrical conductivity. The anomalies are related to deep faults. Increased electrical conductivity may be due to the presence of magmatic melts feeding volcanoes. The results obtained in our study give evidence of the common features of the deep structures of South Kamchatka and the Kuril island arc and demonstrate the differences between the deep structures of North and South Kamchatka, being separated by the zone of faults, which may penetrate into the upper mantle. It is suggested that the identified features in the South Kamchatka structure are due to deep processes taking place not only at the side of the Pacific Ocean, but also at the southern margins of the Sea of Okhotsk. These findings are of interest for geodynamics, volcanology, tectonics and other Earth sciences.

LONG-LIVED STRUCTURAL ENSEMBLES OF THE EAST EUROPEAN PLATFORM. ARTICLE 3. TECTONICS OF THE PLATFORM’S COVER

In the modern structure of the East European platform (EEP) an important role is played by long-lived dislocation zones, complicating the complexes of the platform’s cover and the basement. They are organized non-linearly, form a large vortex megastructure twisted clockwise, and are characterized by an inhomogeneous structure in the vertical and lateral directions. In the stages of their development, numerous dynamic (kinematic) inversions are observed, which are associated with the periodic manifestation and repetition of various geodynamic settings: collision, rifting, transpression and transtension. The processes of alternating rotation of EEP using “iris diaphragm” model explain many development laws of long-lived tectonic zones and vortex megastructure.

Quantification of complex-phase steel microstructure by using combined EBSD and EPMA measurements

We combined electron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA) techniques to characterize the microstructure of industrial produced complex-phase CP800 steel. First, three major constituents (ferrite, martensite and bainite) are characterized. Then, transformation-induced dislocation zones in ferrite and bainitic regions consisting of different sub-structures are quantified and segmented. A final digitalized component map including plenty of microstructural features including crystal structures, orientations and elemental distribution are successfully achieved. The precise carbon content is measured in bainite and martensite utilizing EPMA line scans, which is around 0.2 wt% and 0.4 wt%, respectively. In the bainite phase of CP800, a typical Bagaryatski orientation relationship between cementite and lath-like bainitic ferrite is revealed based on the select diffraction patterns of transmission electron microscopy measurements.

System organization of disjunctive tectonics of consolidated basement in Dnipro-Donets paleorift. Part 3. Structural-cinematic parageneses of horizontal-shear dislocations zones

Formulation of the problem. Getting knowledge of the processes and mechanisms of the rocks tectonic flow is important both for geotectonics and for oil and gas geology as horizontal displacements and rotation of geological blocks in creep dislocations form secondary deformation structures. Zones of both raised and reduced tectonic stresses are formed in the structural and kinematic parageneses - the so-called shadow geodynamic zones, in which active fluid-dynamic processes contributing to traps formation and accumulation of hydrocarbons in them, are formed. Objects of research are secondary deformation structures of tectonic flow (STF). Their newest structural-kinematic parageneses and structured drawings on the surface of Precambrian crystalline basement were studied. Horizontal strike-slip dislocations create their modern architectural structure together with relics of the riftogenic structure. The purpose of the article. The aim of the research is to study structural manifestation of collisional post-tectonic tectogenesis processes in the architectural structure of the DDP crystalline basement. The research tasks are: - To study the types of tectonic movements and mechanisms of tectonic flow deformations in the foundation and identification of the structural patterns; - To diagnose morphogenetic types of strike-slip deformation structures of the basement and structural-kinematic parageneses of tectonic flow. Methods. According to Plates tectonics theory the tectonic-physics method of structural drawings analysis was used to study the basement tectonics. It allows us to diagnose tectonic movements and deformations of geomass, in particular, its longitudinal, transverse and rotational displacement relative to the extension of the paleoriff structure in various kinematic forms of bending in the horizontal plane, extrusion and injection, as well as the adjoining movements of domains - groups of horizontal strike-slip faults ensembles and their created geological blocks. Results. According to the results of regional tectonophysical studies: It is established that considerable internal tectonic mobility of the Precambrian foundation at the newest stage of the DDP evolution is manifested in the formation of horizontal strike-slip dislocations zones in the regional system of faults activated in the latest geodynamic stress field. The processes and mechanisms of collision tectonics, which caused formation in the knot zones of the deformation structures of the tectonic flow and the formation of strike-slip structural and kinematic parageneses, have been studied. They are reflected in the tectonic plan of the foundation in the form of characteristic structural elements of the structure and determine its modern architectural structure. The three basic tectonophysical mechanisms of horizontal strike-slip islocations, which differ in kinematics and directions of joint horizontal displacements of block domains, relative to the axis of the paleorief strike, are distinguished: - longitudinal elongation under the mechanism of joint antithyroid rotations of blocks on systems of diagonal strike-slip faults; - transverse extension of the mechanism of joint synthetic rotation of blocks on systems of orthogonal and diagonal shifts, as well as their complex combination without the rotation of the duplex blocks; - tectonic megabout by means of coordinated reciprocating movements without rotational component of adjacent blocks along kinematically identical sub-parallel strike-slip faults. Scientific novelty and practical significance . In the framework of the newest zones of horizontal strike-slip dislocations, three genesic types of structurally-kinematic parageneses, which correspond to the main geodynamic conditions, are established: – contractional duplexes that form ensembles of longitudinal and transverse to reach the paleiorief of positive forms-«palm tree» on the surface of the foundation -structural-tectonic and embrio-tectonic arcs; – extensional duplexes of the sprawl, forming the negative forms- «flower structures» or pull-apart basine - lens-like minigrabens; geological blocks - megabodies of oval form, forming local depressions in the relief of the foun-dation.

Torsion delamination and recrystallized cementite of heavy drawing pearlitic wires after low temperature annealing

Relationship between torsion delamination and cementite recrystallization in heavily cold drawn pearlitic steel wires was investigated following low temperature annealing. It was found that torsion delamination occurred inevitably when the wires underwent annealing at temperatures ranging from 210℃ to 350℃ with duration from 2min to 60min. The torsion angle corresponding to uniform torsional deformation of annealed wires was dropped to about 10% as compared to the as-drawn wires. The torsional tolerance is independent of tensile mechanical properties when subjected to annealing treatment. Low temperature annealing didn’t alter the morphology of cementite in the wires, but instead it changed cementite structure from disordered (i.e., near amorphous) to nano-crystalline state. After low temperature annealing, dislocation cells formed in ferrite during torsion tests. The recrystallized cementite impeded dislocation motion and was found to break up around high-density dislocation zones. Micro-cracks resulting from torsion delamination were observed near damaged cementite sites. By contrast, in as-drawn steel wires cementite and ferrite deformed in a coherent and coordinated manner. In doing so, the wires exhibited a greater tolerance to torsion damage.

Stress State of a Coal Pillar in Fully Mechanized Longwall Mining in Dislocation Zone

Stress state of rock mass during fully mechanized longwalling in dislocation zone is analyzed. In focus is the variant of crossing the dislocation zone with disassembling the fully mechanized longwall system and its re-assembling in a new room. Stress redistribution in coal and host rocks when heading approaches dislocation and in post-dislocation mining from the new assembling room is determined.

Crimea–Kopet Dagh zone of concentrated orogenic deformations as a transregional late collisional right-lateral strike-slip fault

It is shown that the Crimea, Caucasus, and Kopet Dagh fold systems make up a single whole unified by a lithospheric strike-slip fault zone of concentrated dislocations. The strike-slip fault that dissects the sedimentary cover and consolidated crust is rooted in subcrustal layers of the mantle. The notions about strike-slip dislocations in the structure of the Crimea–Kopet Dagh System are considered. Comparative analysis of structure, age, and amplitude of strike-slip fault segments is carried out. The effect of strike-slip faulting on the deep-seated and near-surface structure of the Earth’s crust is considered. Based on estimation of strike-slip offsets, the paleogeography of Paleogene basins is refined; their initial contours, which have been disturbed and fragmented by slipping motion strike-slip displacement, have been reconstructed.

Molecular dynamics study of deformation behavior of crystalline Cu/amorphous Cu50Zr50 nanolaminates

Crystalline/amorphous (C/A) metallic nanolaminates have been increasingly studied due to its excellent mechanical behaviors. Here, the effects of layer thickness and sample size on the deformation behavior of C/A Cu/CuZr nanolaminates under tension loading are investigated using molecular dynamics simulation method. For nanolaminates with equal layer thickness of crystalline and amorphous, a transition in the plastic deformation mode takes place in the C/A nanolaminates from homogeneous plastic co-deformation between interfacial dislocation and shear transformation zones to multiple shear bands interaction. For the nanolaminates with fixed amorphous layer, the peak stress decreases with the decreasing crystalline layer thickness, consisting with the results calculated by the mixed rule. However, when crystalline layer thickness is >5nm, the peak stress reaches a plateau, which can be well-explained by the confined layer slip model. In addition, the results indicate that the plastic deformation behavior of nanolaminates transits from global plastic deformation to local plastic deformation with decreasing aspect ratio.

SYSTEM ORGANIZATION OF DISJUNCTIVE TECTONICS IN CONSOLIDATED BASEMENT OF DNIPRO-DONETS PALEORIFT

Formulation of the problem. The article is the second in trilogy, which exposes geological structure and geodynamic evolution of Proterozoic crystalline basement of Dnieper-Donets paleorift. Knowledge of strike-slip tectonics of intraplate geostructures with sedimentary basins belonging to them, such as Dnieper-Donets paleorift with cognominal hydrocarbon bearing basin within it, has important applied significance, owing to structure-froming and strcuture-controlling role of strike-slip faults, that cause spatial distribution of various tectono-magmatic centers, zones of fold uplifts series, structural-facial zones, salt-folds subbasins, etc., within which oil & gas fields are localised. The subject of the research is structural appearance of strike-slip tectonics in precambrian crystalline basement in the form of secondary deformed structures of rift evolution stage. The subject of studies has been structural-paleotectonic and peleogeodynamic conditions of Dnieper-Donets rift formation.The purpose of the article. Purpose of the research has been study of structure-forming processes at the rifting stage, for which the following tasks have been resolved:− study of territory expansion in the ancient rift zones of horizontal strike-slip dislocations;− reconstruction of tectonical position of paleogeodynamic field’s main parameters in paleotensions of rift evolution stage;− study of typical structural-kinematic paragenesis in identified zones of strike-slip dislocations;− modelling of Dnieper-Donets rift formation kinematics.Methods. Methodical approach in researches of rift stage tectonic evolution has been indentified by complexing of structural-kinematic and structural-paragenenetic methods of tectonophysical analysis for study and diagnostic of morphogenetic type of Precambrian basement dislocaion structures. Actual curvlinearity of basement faults has been converted to discrete assemblage of lineaments with overall number of 900 items, which filled output database for tectono-physics analysis of disjunctive systems.Results. Spatial dislocation, paleotectonic position and paleogeodynamic conditions of ancient riftogenic fault systems formation has been studied. Modelling of rift formation kinematics has been carried-out based on reconstruction of main parameters of earth crust tension-deformation state at the stage of rifting. It has been shown that rifting was occurring in overall plate collision geodynamic environment under interference of local horizontal strike-slip field of paleotensions from tangential componental stretching. Under these geodynamic conditions in zones of dynamic influence of almost all regional systems of disjunctive faults, linear zones of concentration of horizontal strike-slip dislocations, creating within them typical ensembles of secondary deformed strike-slip structural-kinematic paragenesis, were forming. Elastic deformation with divergence of "cold" continental earth crust was grounded by the rifting mechanism. The main role in rifting mechanism was played by transforming faults formed following structural directions of transverse transregional fault systems. They served as unique tectonic “rails” by which opposite margins of megasegments – pull-apart basins were spreading, which consequently joined and tuned into one rift system.Scientific novelty. The main factor and cause of continental rifting should be considered stretching deformations of earth crust in strike-slip field of geodynamic tesnsions, owing to that "embryo" subbasins, following mechanism of pull-apart basin was formed. They created "windows" for injection of mantle substance by newly built weaken zones in earth crust, and as a result they formed a steady-state "mantle window" in lithosphere, that served as distributary channel in the rift system of mantle fluids.

Stress State of a Coal Pillar in Fully Mechanized Longwall Mining in Dislocation Zone

Stress State of a Coal Pillar in Fully Mechanized Longwall Mining in Dislocation Zone

Sedimentary cover deformations in the equatorial Atlantic and their comparison with geophysical fields

The deformations of the sedimentary cover at near-latitudinal geotraverses west and east of the Mid-Atlantic Ridge in the equatorial part of ocean are compared with potential fields and variations of the Vp/Vs attribute at a depth of ~470 km. The features of sedimentary cover deformations in abyssal basins are formulated, as well as their differences from the undisturbed bedding of sediments. The elements of chain of phenomena with common spatial manifestations and cause-and-effect relationships have been established, including heterogeneous horizontal movements, which make up macrojointing above “cold” mantle blocks at a depth of ~470 km; serpentinization of upper-mantle rocks; the formation of superposed magnetic anomalies; the release of the fluids, which acoustically bleach out the sedimentary sequence in seismic imaging; and decompaction of rocks leading to vertical motions and forced folding. The origin of the Atlantic marginal dislocation zone is explained. The coincidence of the deformation boundary in the equatorial Atlantic with the zero contour line of the Vp/Vs attribute is revealed. This coincidence is an indicator of the rheological state of the upper mantle.

Picosecond laser micromachining prior to FIB milling for electronic microscopy sample preparation

In order to check the manufacturing quality of electronic components using electron microscopy, the area of interest must be exposed. This requires the removal of a large quantity of matter without damaging the surrounding area. This step can be accomplished using ion milling but the processing can last a few hours. In order to accelerate the preparation of the samples, picosecond laser micromachining prior to Focused Ion Beam polishing is envisioned. Laser ablation allows the fast removal of matter but induces damages around the ablated area. Therefore the process has to be optimized in order to limit the size of both the heat affected zone and induced dislocation zone. For this purpose, cavities have been engraved in silicon and in electronic components, using a linearly polarized picosecond laser (∼50ps) at three different wavelengths (343, 515 and 1030nm). Results showed that the cross sectional shapes and the surface topologies can be tuned by the laser fluence and the number of pulses. Clear cross sections of bumps and cavity openings, exposing multilayer interfaces, are demonstrated. The silicon removal rates, tuned by the applied energy density, have been measured. Removal rates achieved at 200kHz were typically hundred times higher than those achieved by ion milling and the best efficiency was obtained at 343nm.

Preiskava Portevin-Le Chatelier učinka pri vročem valjanju Fe-13Mn-0.2C-1Al-1Si TWIP jekla

This study was undertaken to investigate the microstructure and mechanical properties of hot rolled Fe-13Mn-0.2C-1Al-1Si TWIP steel. Tensile tests were carried out at different strain rates to determine the Portevin-Le Chatelier (PLC) effect during deformation. Subsequently, the samples were investigated by light microscopy and SEM. The sample microstructures revealed inhomogeneous dislocation zones, deformation twinning and twin-dislocation interactions. Consequently, the PLC effect during deformation was determined to be responsible for the excellent mechanical properties of the TWIP steel.

Mechanistic coupling of dislocation and shear transformation zone plasticity in crystalline-amorphous nanolaminates

The deformation behavior of crystalline-amorphous nanolaminates is explored through molecular dynamics simulations using nanolaminate models that contain columnar nanograins in the crystalline layers to more closely resemble experimentally accessible nanolaminate structures. Quantitative analysis of the plastic strain distribution among competing mechanisms and their coupling at the nanoscale is accomplished through the implementation of continuum deformation metrics. The transfer of plastic strain between shear transformation zone (STZ) and dislocation plasticity initially transpires through the emission of dislocations from STZ activity impinging on the amorphous-crystalline interface (ACI). The addition of grain boundaries biases this process to regions near the boundaries at low strains, which reduces the activation barrier for the onset of dislocation plasticity. With increasing strain, dislocations are absorbed into the amorphous layers via slip transfer across the ACI, in turn triggering the activation of new STZs. Cooperative slip transfer between dislocations and STZs suppresses grain boundary microcracking collectively with large-scale shear localization, and provides an explanation for the enhanced toughness of crystalline-amorphous nanolaminates.

Formation of flower structures in a geological layer at a strike-slip displacement in the basement

Formation of dislocations in a geological layer at a strike-slip displacement in its basement is studied by three-dimensional (3D) numerical modeling. It is shown that the pattern of strain localization is determined by the initial stress state or thickness of the deformed layer as well as by the Poisson ratio and strength of the medium. Three types of fracture zones are observed. Shear bands of the first type are dominated by the propeller-like surfaces of Riedel R-shears, which merge into a single main fault with feathering structures. In the second type of dislocation zones, the primary role is played by the surfaces oriented at an angle of ∼40° to the shear axis in the horizontal projections. After reaching the free surface, these discontinuities are cut by a V-shaped fault. In this case, the pattern of dislocations most closely corresponds to the flower structures. The third type is a trough, which may accommodate the formation of yet another strain localization zone along its axial part—a vertical fault.

Uskok Starego Julianowa w sowiogórskim kompleksie gnejsowym i sytuacja geologiczna w miejscu jego występowania (Pogórze Wałbrzyskie, Sudety Środkowe, południowa Polska)

STARY JULIANOW FAULT IN SOWIE GORY GNEISS COMPLEX AND GEOLOGICAL SITUATION IN THE PLACE OF ITS OCCURRENCE (WAŁBRZYCH FOOTHILLS, CENTRAL SUDETES, SOUTHERN POLAND) Abstract. The paper describes localization and architecture of a uranium-bearing fault, called the Stary Julianow Fault (uStJ). The fault studied occurs in a north-western fragment of the sudetic part of the Gory Sowie Gneiss Massif (MGS ), in the area of the Walbrzych Foothills, between Stary Julianow and Dziecmorowice. It is one of faults that make up the northern part of a broad dislocation zone extending from Stary Julianow to Zagorze Ślaskie, in which the occurrence of hydrothermal mineralization, called mineralization from Dziecmorowice, was described. Information about the Stary Julianow Fault obtained during its exploration by underground workings to the depth of 345 m and the extension of 900 m, which were made in the years 1949–1952 in connection with uranium ore mining. The Stary Julianow Fault belongs to “older” faults with direction NW –SE and it is oriented crosswise to macrofold which occurs in Julianow region. The architecture of a fault zone of the Stary Julianow Fault consists of two parts: a fault core and a damage zone. The fault core is represented by narrow zone, composed of the fault rocks with the occurrence of uranium-bearing calcite lenses. The damage zone is brittle deformation with instances of carbonate mineralization and hydrothermal alteration of gneisses. It is particularly wide developed in the east side of the Stary Julianow Fault. The architecture and position of the Stary Julianow Fault in the tectonic structure of the region suggests its formation during the Variscan evolution of the Gory Sowie Gneiss Massif.

Effect of Grain Size on the Fracture Toughness of Bimodal Nanocrystalline Materials

To research the effect of grain size on the fracture toughness of bimodal nanocrystalline (BNC) materials which are composed of nanocrystalline (NC) matrix and coarse grains, we have developed a theoretical model to study the critical stress intensity factor (which characterizes toughness) of BNC materials by considering a typical case where crack lies at the interface of two neighboring NC grains and the crack tip intersect at the grain boundary of the coarse grain, the cohesive zone size is assumed to be equal to the grain sizedof the NC matrix. Blunting and propagating processes of the crack is controlled by a combined effect of dislocation and cohesive zone. Edge dislocations emit from the cohesive crack tip and make a shielding effect on the crack. It was found that the critical stress intensity factor increases with the increasing of grain sizedof the NC matrix as well as the coarse grain sizeD. Moreover, the fracture toughness is relatively more sensitive to the coarse grain size rather than that of NC matrix.

Homogeneity of rapid grown DKDP crystal

For rapid grown DKDP crystals, homogeneity should be paid more attention than traditional grown ones because their deuterated levels will be affected more significantly by the large supersaturation, which give harmful impact on optical property as well as the related nonlinear optical applications. In this paper, from the points of deuterated level and transmittance, the homogeneity of a point-seed rapid grown DKDP crystal with sizes of 65 × 65 × 113 mm3 is investigated. The results show that the maximum discrepancy of deuterium content is 5.4%, and the ultra-violet transmittances of the dislocation zone and its surrounding areas are ~30% inferior to other regions.

Structural assemblies of the Vladimir-Vyatka dislocation zone and the position of the Puchezh-Katunki Crater, East European Platform

The Puchezh-Katunki (PK) structural unit is situated in the Middle Volga region of the central East European Platform (EEP). It is expressed as a system of complex dislocations and a meteoritic crater with a central uplift. Based on the results of structural study, the attributes of its long evolution have been revealed. Four deformation stages have been established: Hercynian (1) fold-nappe and (2) trancpressional deformations, (3) formation of the Early Jurassic impact crater and the related system of radial-concentric faults, and (4) low-amplitude tectonic reactivation of Hercynian faults during the Kimmerian-Alpine stage of evolution. In general, the PK structural unit is localized in the most strained segment of the Vladimir-Vyatka Dislocation Zone, which separates the largest structural domains of the EEP. This is a long-lived zone, which developed cyclically beginning from Paleoproterozoic collisional events and up to the Kimmerian-Alpine stage of reactivation. Such a direct impact to the cluster of concentrated deformations in one of the largest tectonic zones of the EEP seems unlikely. Nevertheless, available evidence, including the estimated stress related to the impact effect (up to 50 GPa) and its decrease with depth, does not rule out the meteoritic origin of the PK structural unit.