Development Of Faults Research Articles

Branches of the Karakoram fault in Eastern Pamir

ABSTRACT The tectonic evolution of the Karakoram fault in the Pamir Plateau is controversial because the timing and kinematics of several branches of the fault system are unclear. Here we conduct field observations on the East Pamir fault, the North Muskol shear zone, and the Xindi-Waqia fault in the eastern Pamir, and obtain zircon U-Pb and biotite 40Ar/39Ar ages from these ductile shear zones. All three faults/shear zones are hosted by granitic mylonites. The East Pamir fault is a northwest-striking, normal-dextral shear zone that cuts the Rushan-Pshart suture. Zircon U-Pb dating yields a mean age of 201.5 ± 0.5 Ma for the mylonites in this shear zone. Biotite 40Ar/39Ar analysis yields two weighted mean plateau ages, 10.65 ± 0.13 Ma, and 11.04 ± 0.15 Ma. An undeformed granitic vein that cuts the ductile shear zone gives a mean zircon U-Pb age of 9.6 ± 0.3 Ma. We interpret that the granitic protolith crystallized at 201.5 Ma, and the East Pamir fault underwent rapid cooling and exhumation at ca. 11 Ma and ceased by 9.6 Ma. The North Muskol shear zone is an east-striking extensional shear zone along the northern boundary of the Shatput-Muztaghata dome. Two mylonitic samples show mean 206Pb/238U ages of 17.9 ± 0.2 Ma and 17.6 ± 0.3 Ma, which are interpreted as the timing of crystallization of the granitic protolith. The Xindi-Waqia fault is a northwest-striking ductile shear zone and brittle fault that bounds the Muztaghata dome. We obtain two zircon U-Pb ages (231.8 ± 1.1 Ma, 235.9 ± 0.9 Ma) and two biotite 40Ar/39Ar plateau ages (between 6.60 ± 0.10 Ma and 6.87 ± 0.10 Ma) from the mylonites in this fault, and interpret that the granitic rocks were emplaced in the Late Triassic and exhumed in the late Miocene. The newly obtained U-Pb ages, combined with the previously published data, indicate that Rushan-Pshart suture in Pamir marks the closure of an ocean basin within the Palaeo-Tethys Ocean, and cannot be correlated with the Bangong-Nujiang suture in Tibet. We establish a systematic correlation in which the two Palaeo-Tethyan sutures (Tanymas-Jinshajiang and Rushan-Pshart) in Pamir represent the western extensions of the Jinshajiang and Longmu Co-Shuanghu sutures in the Tibetan Plateau, respectively, and the Central Pamir is the western extension of the Tianshuihai-North Qiangtang terrane. This indicates that the dextral slip along the Karakoram fault system in east-central Pamir is 140 ± 10 km, and the mean slip rate since the onset of the Karakoram fault at ca. 18 Ma is 7.8 ± 0.5 mm/yr. Furthermore, our analyses suggest that the North Muskol shear zone was active at ca. 18 Ma before the arrival of the Karakoram fault system then. The East Pamir fault must have been active at ca. 11 Ma, but ceased by ca. 9.6 Ma, and the slip along the Karakoram fault system migrated northeastward and primarily accommodated by the Tashkurgan fault soon after 9.6 Ma. The Xindi-Waqia fault is the southern extension of the ductile shear zone of the Kongur Shan extensional system, as they are highly similar in geometry, kinematics, and timing. Overall, as the Karakoram fault system propagated northward in Pamir during the Cenozoic, crustal deformation migrated northeastward among the Karakoram fault branches from Ladakh to the Kashgar-Yecheng transfer system, and a complex evolution path can be portrayed.

Relations between inherited basement fabric and fault nucleation in a continental setting: The Rio do Peixe Basin, NE Brazil

The control of normal fault growth by preexisting basement structures is still a worldwide matter of debate. The objectives of the present study are (i) to investigate where rift faults nucleate in continental-scale ductile shear zones and how these zones influence fault architecture; (ii) how subvertical basement fabric controls listric fault geometry and evolution; (iii) how long reactivation of faults lasts; and (iv) which are the implications of fault reactivation for the oil industry. We contribute to these issues by defining the 3-D relationship between preexisting ductile strike-slip shear zones, the geometry and evolution of subsequent rift-related normal faults using airborne magnetic, 2-D and 3-D seismic reflection, and structural data from the Rio do Peixe Basin, a Cretaceous intracontinental basin in northeastern Brazil. Our results indicate that Precambrian mylonitic foliation and faults share a common strike at the surface, but not a common dip, mostly because the Precambrian shear zones are planar and the reactivated faults are listric (curved). The combined magnetic anomaly and seismic reflection help understand the 3-D geometrical relation between inherited structures and Cretaceous brittle reactivation, which is not obvious from the field data. As inferred from subsurface information, the mylonitic foliation (sub-vertical dip) and shear zone boundary (ca. 60° dip, parallel to brittle faulting) are not parallel. The basin-bounding faults reactivated along ductile shear zones that separate major terranes with mechanical contrast. We conclude that the map view spatial coincidence of Precambrian ductile shear zones and main brittle faults can be deceiving. Mylonitic foliation and faults are parallel along strike but not along dip, indicating that the geometry of rift faults is not controlled by the mylonitic foliation, but by the mechanical contrast between tectonometamorphic units separated by ductile shear zones.

Insights into the geometry and evolution of the southern San Andreas fault from geophysical data, southern California

AbstractTwo new joint gravity-magnetic models in northern Coachella Valley provide additional evidence for a steep northeast dip of the Mission Creek strand of the southern San Andreas fault (southern California, USA). Gravity modeling indicates a steep northeast dip of the Banning fault in the upper 1–2 km in northern Coachella Valley. The Mission Creek strand and its continuation to the southeast (Coachella segment) coincide with the northeastern margin of a Cenozoic basin and are marked by prominent gravity and magnetic gradients that are consistent with these strands of the San Andreas fault having accommodated >160 km of right-lateral and 1–5 km of vertical displacement. These anomalies are best fit by a moderate to steep northeast dip. Such a geometry is further supported by seismicity, reflectivity, geodesy, and boundary-element modeling. We explore the possibility that these fault strands forming the margin of Coachella Valley were originally near vertical and have rotated into their present orientation by underplating of a localized high-velocity, lower-crustal prong within the Peninsular Ranges batholith. Reconstructions of San Andreas fault offset suggest that this crystalline body was translated into the San Gorgonio Pass area at the time of major fault reorganization at 1.1–1.3 Ma.

New Insights into the Distribution and Evolution of WNW-Directed Faults in the Liaodong Bay Subbasin of the Bohai Bay Basin, Eastern China

WNW-directed faults are widespread in eastern China, but debates regarding their distributions and evolutionary processes remain unsettled. Based on the latest 3-D seismic data, a series of WNW-directed faults south of the Liaodong Bay subbasin was identified, for which the evolution and formation mechanisms were discussed. The results show that four WNW-directed faults are characterized by poor continuity and nearly parallel orientations. Vertically, they exhibit listric geometries and cut through Paleozoic and Mesozoic formations. Since the late Triassic, these faults began as reverse faults under nearly S-N horizontal compression. In the Jurassic, those faults maintained their reverse-faulting activities with dramatically decreased intensities. In the Early Cretaceous, the WNW-directed faults were changed into normal faults under regional extension and were influenced by the sinistral strike-slip movement along the Tan-Lu fault zone. In the Late Cretaceous, the WNW-directed normal faults probably stopped moving due to a regional compressional event. During the Paleogene, the WNW-directed faults were reactivated with decreased intensities and were cut by NNE-directed faults. Here, we emphasize that the evolution of the WNW-directed faults could shed light on the regional tectonics. The WNW-trending faults that developed in the Liaodong Bay subbasin are closely related to the faults in the Yanshan orogenic belt. Therefore, investigating the characteristics and origin of WNW-induced faults will provide evidence for the tectonic evolution of the North China Block. In addition, the development of WNW-directed faults in the southern Liaodong Bay subbasin was conducive to the formation of buried Mesozoic and Paleozoic hills and hydrocarbon accumulations. In addition, we suggest that the compressional segment of the conjugated strike-slip transition zone that was formed by the interaction of the WNW- and NNE-directed strike-slip faults was conducive to hydrocarbon accumulations.

A Novel Multilabel Classification Framework for Coupling Faults in Hot Rolling Processes

Compared with a single fault, the occurrence, evolution, and composition of coupling faults have more uncertainties and diversities, which make coupling fault classification a challenging topic in academic research and industrial application areas. This brief addresses the classification problems of coupling faults from a new perspective. Specifically, the main innovations are: 1) a classification framework for coupling faults is first proposed, which integrates multiple kernel learning and multilabel dimensionality reduction; 2) label correlations and nonlinear characteristics among coupling faults are fully explored aiming at improving classification performance; and 3) a trace ratio form of l_1 norm-based objective function is designed for improving the robustness of multilabel classifier. Extensive experiments on the hot rolling process (HRP) are finally given to validate the effectiveness of the proposed scheme.

Research on fault characteristic of modular multilevel converter

Along with China proposes to build a new energy power system, various DC transmission technologies have been extensively studied. As the most serious fault type of the DC transmission system, permanent DC bipolar short-circuited fault is easy to cause converter damage. Modular multilevel converter can be used in the DC power transmission and distribution systems because of its modular design and strong ability on handling fault. When permanent DC bipolar short-circuited fault occurs, the research on fault characteristics of modular multilevel converter can offer important support for current-limiting control of converters and relay protection of power system. By analogy with the fault evolution mechanism of two-level converter, the equivalent zero-crossing voltage of sub-module capacitance is defined, and the fault evolution mechanism of modular multilevel converters can be obtained. The expressions of the fault characteristic parameters including the equivalent zero-crossing voltage of the sub-module capacitance, the DC steady short-circuited current, the peak value of the DC short-circuited current and their difference, and the peak time of the DC short-circuited current were deduced. By the way of analysis and simulation, the influence of the main circuit parameters in MMC on the characteristic variables with short-circuited fault can get the regularity, it can provide the theory basis for the current-limiting control and relay protection.

BIG EARTH DATA PROCESSING USING MACHINE LEARNING FOR INTEGRATED MAPPING OF THE DEAD SEA FAULT, JORDAN

In this research, an integrated framework on the big Earth data analysis has been developed in the context of the geomorphology of Jordan. The research explores the correlation between several thematic datasets, including machine learning and multidisciplinary geospatial data. GIS mapping is widely used in geological mapping as the most adequate technical tool for data visualization and analysis. GIS applications encourage geological prospective modeling by visualizing data aimed at the prognosis of mineral resources. However, automatization using machine learning for big Earth data processing provides the speed and accurate processing of multisource massive datasets. This is enabled by the application of scripting and programming in cartographic techniques. This study presents the combined machine learning methods of cartographic analysis and big Earth data modeling. The objective is to analyze a correlation between the factors affecting the geomorphological shape of Jordan with respects to the Dead Sea Fault and geological evolution. The technical methodology includes the following three independent tools: 1) Generic Mapping Tools (GMT); 2) Selected libraries of R programming language; 3) QGIS. Specifically, the GMT scripting program was used for topographic, seismic and geophysical mapping, while QGIS was used for geologic mapping and R language for geomorphometric modeling. Accordingly, the workflow is logically structured through these three technical tools, representing different cartographic approaches for data processing. Data and materials include multisource datasets of the various resolution, spatial extent, origin and formats. The results presented cartographic layouts of qualitative and quantitative maps with statistical summaries (histograms). The novelty of this approach is explained by the need to close a technical gap between the traditional GIS and scripting mapping, which is wider for big data mapping and where the crucial factors are speed and precision of data handling, as well as effective visualization achieved by the machine graphics. The paper analyzes the underlying geologic processes affecting the formation of geomorphological landforms in Jordan with a 3D visualization of the selected fragment of the Dead Sea Fault zone. The research presents an extended description in methodology, including the explanations of code snippets from the GMT modules and examples of the use of R libraries ‘raster’ and ‘tmap’. The results revealed strong correlation between the geological and geophysical settings which affect geomorphological patterns. Integrated study of the geomorphology of Jordan was based on multisource datasets processed by scripting. A thorough analysis presented regional correlations between the geomorphological, geological and tectonic settings in Jordan. The paper contributed both to the development of cartographic engineering by introducing scripting techniques and to the regional studies of Jordan including the Dead Sea Fault as a special region of Jordan. The results include 12 new thematic maps including a 3D model.

Linked detachment folds, thrust faults, and salt diapirs: Observations and analog models

Contractional deformation in salt-bearing rifted- and convergent-margin settings often involves diapirism. Diapirs may predate the onset of shortening, such that they exert a pronounced influence on how contractional strain is accommodated, or they may be triggered by the shortening. Analog models have been used to help understand the interaction and evolution of detachment folds, thrust faults, and diapirs, but few surface or subsurface datasets provide adequate three-dimensional images to test and refine the experimental results. Here we use 3D depth-migrated seismic data from the Sureste Basin, offshore SE Mexico, to map two structures, one dominated by salt-cored anticlines and one characterized by thrust faults. Associated diapirs include both pre- and syncontractional stocks and walls. We show that although analog models in the literature nicely reproduce some of the seismic geometries, there are also apparent mismatches. Whereas models often generate decapitated diapirs and thrust-fault salients centered on the diapirs, such features are absent in the study area. Moreover, in contrast to model thrust faults that dip 20-45°, faults in the study area are steeper, ranging from 50 to 75°. We bring in observations from other salt basins to discuss these discrepancies, possible explanations, and suggestions for improving the applicability of models to nature.

Interpretable online updated weights: Optimized square envelope spectrum for machine condition monitoring and fault diagnosis

Bearings are key components of rotating machines, and their condition monitoring and fault diagnosis have received much attention from academia and industry in recent years. Existing fault diagnosis methods can be generally classified into signal processing-based fault characteristic frequency (FCF) identification methods and machine learning-based model classification methods. Though the former owns clear physical meaning, its integration with monitoring data for automatically optimizing square envelope spectrum for identification of FCF is not fully explored. As for the latter, lacking explicit interpretability of learned model weights limits its wide applications. In this paper, to address these critical issues, the integration of online monitoring data with cyclostationarity of fault transients is sufficiently studied and utilized to construct a fault cyclostationarity-based convex optimization model. The maximum logarithmic likelihood estimation is then used to solve the convex optimization model. Moreover, an online weight updating algorithm is developed to relieve the requirement of historical data and to make the weight updating of the proposed optimization model adaptive to online monitoring data. Subsequently, interpretable online updated weights as an optimized square envelope spectrum (OSES) are proposed to enhance the identification of FCF and its harmonics in the OSES. And a three-dimensional (3D) OSES and a detector with an alarming threshold are designed to eliminate the need for label information and further to simultaneously achieve incipient fault time detection, fault type diagnosis, and online fault evolution monitoring. A practical-project bearing dataset and two experimental bearing run-to-failure datasets are used to validate the effectiveness and superiority of interpretable online updated weights as the OSES and 3D OSES. Results demonstrate that the integration of fault characteristics with machine learning theory (e.g., convex optimization) is a new promising physics-informed perspective to monitor and diagnose machine faults.

Characteristics and Evolution of Strike-Slip Faults in a Stable Cratonic Block: Southwest Ordos Basin, China

Characteristics and Evolution of Strike-Slip Faults in a Stable Cratonic Block: Southwest Ordos Basin, China

Types of Beixi slopes and the process of tectonic evolution

The phenomenon of oil and gas accumulation on the Beixi slope is obvious, which is one of the important directions of oil and gas pre-exploration and increasing reserves and production in the future. Taking the Beixi slope as the target area, according to the geological characteristics, the Beixi slope is divided into the differential subsidence type of the same fault depression, the reverse normal fault tilting and lifting slope and the compound slope. The evolution profile of Beixi slope is restored by using 2Dmove application software. based on the joint action of structure and deposition of Beixi slope, the fault evolution process of Beixi slope can be divided into four stages: rift stage 1 (Tongbamiao formation-N14 reflection layer), rift stage 2 (N14 reflection layer-T22 reflection layer), fault depression conversion stage (T22 reflection layer-T04 reflection layer) and depression inversion stage (above T04 reflection layer).

New granular rock-analogue materials for simulation of multi-scale fault and fracture processes

AbstractIn this study, we present a new granular rock-analogue material (GRAM) with a dynamic scaling suitable for the simulation of fault and fracture processes in analogue experiments. Dynamically scaled experiments allow the direct comparison of geometrical, kinematical and mechanical processes between model and nature. The geometrical scaling factor defines the model resolution, which depends on the density and cohesive strength ratios of model material and natural rocks. Granular materials such as quartz sands are ideal for the simulation of upper crustal deformation processes as a result of similar nonlinear deformation behaviour of granular flow and brittle rock deformation. We compared the geometrical scaling factor of common analogue materials applied in tectonic models, and identified a gap in model resolution corresponding to the outcrop and structural scale (1–100 m). The proposed GRAM is composed of quartz sand and hemihydrate powder and is suitable to form cohesive aggregates capable of deforming by tensile and shear failure under variable stress conditions. Based on dynamical shear tests, GRAM is characterized by a similar stress–strain curve as dry quartz sand, has a cohesive strength of 7.88 kPa and an average density of 1.36 g cm−3. The derived geometrical scaling factor is 1 cm in model = 10.65 m in nature. For a large-scale test, GRAM material was applied in strike-slip analogue experiments. Early results demonstrate the potential of GRAM to simulate fault and fracture processes, and their interaction in fault zones and damage zones during different stages of fault evolution in dynamically scaled analogue experiments.

Analogue Sandbox Scaled Modelling of Oblique and Orthogonal Extension Rifting in Rukwa Rift Basin, Tanzania

Fault evolution in oblique and orthogonal rift systems in the brittle upper crust of the Rukwa rift basin was simulated using scaled sandbox modelling by varying the angle between the rift axis and the extension direction, α, through 45° and 90°, over a 10 cm displacement. The 45° oblique model exhibits a half-graben architecture bounded by a planar fault, intra-rift faults and a conjugate fault in some vertical sections. The map view of the model’s basin trends in the NW-SE direction, and is comparable with the Rukwa rift basin orientation. The 90° oblique model forms a basin structure which is orthogonal to the extension direction of the model in aerial photos. Its linear fault remains orthogonal to the extension direction, while the flexural side of the model segments into sinuous normal faults. Planar to slightly curved intra-rift faults are observed in vertical sections. The half-grabens have similar geometries in vertical sections for both models, while intra-rift faults elongate in vertical sections. The results of the oblique model are similar to natural examples of rift fault systems like the Rukwa rift. The fault geometries of the sandbox models can serve as examples for recognizing fault styles in oblique rift systems.
 Keywords: Analogue Sandbox modelling, Oblique rifting, Orthogonal rifting, Tanganyika-Rukwa-Malawi Rift Segment, Rukwa Rift Basin

Cenozoic tectono-sedimentary evolution of the northern Turkana Depression (East African Rift System) and its significance for continental rifts

Rifting is an emblematic facet of continental drift and its early stage (i.e., stretching phase) is pivotal to be fully characterized and understood because it then conditions all subsequent stages of the break-up cycle. Although the final architectures of rifted margins have been extensively documented and discussed over the past decades from a wide range of examples and from multiple surface and sub-surface data, the complete evolution of the stretching phase itself remains mostly illustrated from analogue and numerical models and more rarely from real case studies and field evidences. The northern Turkana Depression (Cenozoic East African Rift System) stands as a key natural example to investigate every stage of the evolution of a stretching phase, as it provides almost ∼30 Ma of rift evolution from its initiation to present-day. In this study, we combine field analyses and seismic reflection data to characterize every stage of this tectono-sedimentary evolution, with a focus on the, rarely observed, surface rupture initiation and tectonic decay. In particular, we show rifting initiates with the reactivation of non-optimal inherited structures, progresses with their abandonment during the development of long and wide grabens or half-grabens, and locally terminates with the development of a post-tectonic flexural sag, synchronously to the migration of the locus of brittle deformation to an adjacent area where starts a similar cycle. Our observations allow us to nuance commonly accepted generic rift evolution models, and to discuss possible geodynamic controls on fault evolution and strain migration. We propose a field-based alternate conceptual evolution model for rift systems sharing common characteristics with the northern Turkana Depression such as abundant inherited basement structures, thin and hot lithosphere and a low to moderate magmatism.

Modelling and simulation analysis of MMC‐HVDC system based on transient energy flow

In the high voltage direct current (HVDC) transmission system composed of modular multilevel converters (MMC), considering the distribution of transient energy flow (TEF) contributes to the transient modelling and fault characteristic analysis when dc short-circuit fault occurs. For single MMC, based on transient energy conservation, the capacitors of half bridge sub-modular (HBSM) can be equivalent to time-varying capacitor. And the MMC transient model is established, in which dynamic switching of HBSM and ac import are considered. By solving state equations of the model, the fault and TEF characteristics of MMC are obtained. For MMC-HVDC grid, a TEF analysis method based on electromagnetic transient simulation results is proposed, which can not only reveal the evolution of dc fault, but also realize quantitative analysis of fault current through recursive calculation. Based on characteristics of TEF, an energy limitation strategy considering the fluctuation range of capacitor voltage in HBSM is proposed, which can delay the blocking time effectively. According to the simulation results in PSCAD, the correctness of the transient model and the energy limitation strategy is verified, meanwhile, the TEF analysis method is applied to the four-terminal MMC-HVDC grid to obtain its fault characteristics.

Structural characteristics of transtensional fault system and its implication for hydrocarbon accumulation in S Block, South Asia area

Transtensional faults are well developed in the S Block of the South Asia area, which have an important impact on the hydrocarbon accumulation. However, the transtensional fault structure is very complex. Based on drilling and seismic data interpretation results, faults are divided into three typical types in the Lower Cretaceous, which can help to understand the complex fault system. The main faults are distributed in the NNW-SSE direction and parallel arrangement with dextral strike-slip shear characteristics, which determines the development of the tectonic belt. The secondary faults are often associated with the main faults, often composed of multiple branch faults. The complexity of the fault system is further aggravated by the small interlayer faults. Based on balanced crosssection technique analysis, the fault evolution has experienced five geological periods, which is closely related to the Indo-Pakistan plate tectonics and the Indus Basin evolution. In the diagonal extension stage of the Late Cretaceous, the fault activity was very strong, which had a significant impact on the tectonic pattern of "horst-graben structures and locally complex faulted blocks" in S Block. It is found that transtensional fault assemblage patterns are regular and diverse. It consists of six kinds of plane assemblage and seven kinds of profile assemblage patterns. Plane assemblage patterns include en echelon, broom, feather, comb, horsetail and diamond shape, while profile assemblage patterns consist of horst-graben faulted type, consequent faulted type, antithetic faulted type, "Y" and reverse "Y" type, "X" type and negative flower type. Different transtensional fault assemblage patterns form various kinds of hydrocarbon trap types, including faulted block, faulted nose, faulted anticline and composite traps. Fault activity and evolution promote the hydrocarbon generation, control the formation of tectonic zones and favorable traps and play an important control role in hydrocarbon migration and accumulation. Therefore, in this study the main exploration and evaluation targets are faulted reservoirs in the study area.

Characteristics of sedimentary differential response for multi-episode rifting cycles in lacustrine rift basin: A case study of the Palaeogene Baxian sag in the Bohai Bay Basin

The evolution of a lacustrine rift basin is a multi-periodic and multi-cyclic procedure. In the present study, we interpreted and analysed a filling process in the Palaeogene Baxian sag of the Bohai Bay Basin (China). Further, we also investigated the evolution of the filling process. We identified the reason for the difference in lacustrine rift basins. Geological and geophysical data, including drilling data, well logging curves, and high-quality full-coverage 3D seismic volume survey data, were used to interpret and analyse the sedimentary system types and their spatial and temporal distribution. The filling evolution of the Baxian sag in the Palaeogene comprised three episodes and had stages where filling occurred. Four depositional systems, namely, alluvial-rivers, lake-deltas, lake beach-bars, and fluvial-floodplains, were detected. The findings of this study suggest that this basin has undergone stages of shallow–deep–shallow water. The entire rifting process could be separated into several multi-episodic sub-processes, with each sub-process undergoing four stages, i.e., initial rifting, strong rifting, stable rifting, and post-fault return. Further, the formation and evolution of faults, particularly boundary faults, control the stratigraphic structure and distribution of sedimentary systems in rift lacustrine basins. Differences in the category and distribution of the sedimentary system illustrate the relationship between fault activity intensity and provenance supply in such basins. Near-source sediments were deposited rapidly in the early stage; subsequently, the basin deepened rapidly. The deep-water deposits and far-source deposits were laid down slowly in the middle and late stages, respectively. Differential activities of boundary faults, influenced by mantle differential convection, controlled the formation and development of rift lacustrine deposits and the differential evolution of the basin. We further summarized the development process and general principles of typical rift lacustrine basins and determined the controlling factors of the corresponding differential evolution. This study provides a basis for investigating the genesis and evolution process of other similar basins.

Structural Evolution of Ore-Controlling Trans-Crustal Faults of the Olchan-Nera Zone: Constraints from the Khangalas Ore Cluster, Yana-Kolyma Metallogenic Belt, NE Russia

The article studies the structural evolution of ore-controlling trans-crustal faults of orogenic deposits and occurrences of the Khangalas ore cluster located in the southeastern part of the Olchan–Nera metallogenic zone, in the Upper Indigirka sector of the Yana–Kolyma metallogenic belt, North–East of Russia. Studies have shown that the formation of tectonic structures occurred during four Mesozoic deformation stages. Accretionary thrust stage D1 resulted in formation of the main pattern of the Mesozoic tectonic structures of the region. Further tectonic evolution occurred in a strike–slip setting of the accretionary D2 and post-accretionary D3–D4 stages. Post-ore strike-slip faults activate and complicate the earlier formed structures of the reverse and thrust paragenesis. Mineralization associated with the strike-slip faults has not been established, whereas formation of the gold-antimony mineralization is associated with sinistral strike–slip faults in the Adycha–Taryn metallogenic zone located to the southwest. The new data obtained are consistent with the previously proposed model of the evolution of the deformation structures of the Khangalas deposit.

Impact of basement thrust faults on low-angle normal faults and rift basin evolution: a case study in the Enping sag, Pearl River Basin

Abstract. Reactivation of pre-existing structures and their influence on subsequent rift evolution have been extensively analysed in previous research on rifts that experienced multiple phases of rifting, where pre-existing structures were deemed to affect nucleation, density, strike orientation, and displacement of newly formed normal faults during later rifting stages. However, previous studies paid less attention to the extensional structures superimposing onto an earlier compressional background, leading to a lack of understanding of, e.g. the reactivation and growth pattern of pre-existing thrust faults as low-angle normal faults and the impact of pre-existing thrust faults on newly formed high-angle faults and subsequent rift structures. This study investigating the spatial relationship between intra-basement thrust and rift-related faults in the Enping sag, in the northern South China Sea, indicates that the rift system is built on the previously deformed basement with pervasive thrusting structures and that the low-angle major fault of the study area results from reactivation of intra-basement thrust faults. It also implies that the reactivation mode of basement thrust faults is dependent on the overall strain distribution across rifts, the scale of basement thrust faults, and the strain shadow zone. In addition, reactivated basement thrust faults influence the nucleation, dip, and displacement of nearby new faults, causing them to nucleate at or merge into downwards it, which is representative of the coupled and decoupled growth models of reactivated thrust faults and nearby new faults. This work not only provides insights into the growth pattern of rift-related faults interacting with reactivated low-angle faults but also has broader implications for how basement thrust faults influence rift structures, normal fault evolution, and syn-rift stratigraphy.

Atomic simulation of the effect of orientation on tensile/compressive properties in nickel-based single crystal superalloys

Nickel-based single crystal superalloys reveal obvious anisotropy and orientation correlation. Choosing the orientation with the best mechanical properties is beneficial to prolong its service life. In this paper, the effects of crystal orientation on the plastic deformation and mechanical properties of the nickel-based single crystal two-phase model under uniaxial tension/compression were simulated by molecular dynamics. The microstructure evolution and dislocation movement are studied through stress-strain response and structural changes of the two phases with different crystal orientations. In addition, the typical dislocation structures are analyzed, it is found that the yield stress of different orientation models is: [111] > [001] > [011]. Different orientation models all show tension/compression asymmetry and the [001] orientation is the most obvious. The results showed that the evolution of dislocation and stacking faults is one of the reasons which causes the crystal anisotropy.