Far-field Effects Research Articles

The early Paleozoic intracontinental orogeny in South China: A far-field response to the closure of the Proto-Tethys Ocean in the Indochina Block

The nature and geodynamics of the early Paleozoic orogen in South China are modeled as either products of direct subduction-collision or intracontinental orogeny. The synchronous basaltic-andesitic rocks within the orogen are at the heart of this scientific debate, but they have been less systematically investigated. The petrogenesis and tectonic setting of these mafic rocks are highly controversial, given their arc-like geochemical characteristics. We systematically investigated the patterns of field relations, ages, chemistry, and Hf-Nd isotopes of the early Paleozoic basaltic-andesitic rocks in the Yunkai massif and those reported elsewhere in the orogen. Based on chemical and isotopic signatures, these basaltic-andesitic rocks (ca. 460−420 Ma) can be divided into calc-alkaline light rare earth element (LREE)-enriched basalts, LREE-enriched andesitic rocks, and tholeiitic LREE-depleted basalts. The calc-alkaline suites mostly display arc-type geochemical features, with enrichment in large-ion lithophile elements, LREEs, and Pb, but depletion in high field strength elements relative to heavy rare earth elements. Their high La/Nb and Ba/Nb ratios, and low Nb/Th ratios, along with negative εHf(t) and εNd(t) isotope values, indicate the distinctive fractionation of incompatible trace elements that may have been derived from the partial melting of ancient metasomatized lithospheric mantle sources. On the other hand, the tholeiitic basalts show normal mid-oceanic-ridge basalt-like rare earth element patterns and positive zircon Hf isotope compositions, which reflect the partial melting of a depleted asthenosphere. Given the “intraplate-type” sedimentary, tectonic deformation, and metamorphic signatures across South China, we conclude that these planar-distributed basaltic-andesitic rocks were associated with the activation of the lithospheric mantle and asthenosphere, which occurred in a postorogenic tectonic environment rather than a subduction-related arc regime. Therefore, all geological facts and data patterns favor the Wuyi-Yunkai orogen as a typical intracontinental orogen. Moreover, the Indochina and South China blocks display comparable early Paleozoic faunas and sedimentary records, while the early Paleozoic Tam Ky−Phuoc Son Suture has been identified in Central Indochina. The timing of orogenesis in South China (ca. 460−440 Ma) overlaps with the pre-450 Ma accretionary orogeny in the Central Indochina Block. Therefore, we propose a geodynamic model of linked South China and Indochina blocks in the northern margin of Gondwana, with the geodynamic stress of the Wuyi-Yunkai orogeny derived from a subduction-collision event in Central Indochina. The Wuyi-Yunkai orogen is thus an intracontinental orogen resulting from the far-field effects of plate tectonics.

New 40Ar/39Ar mineral ages of Archaean to early Proterozoic rocks in northern Sweden and implications for the 1.8–1.5 Ga tectonothermal history of northernmost Fennoscandia

Abstract The bedrock in northernmost Sweden comprises Archaean (2.8–2.65 Ga) and Karelian (2.4–1.96 Ga) rocks and a volumetrically dominant population of magmatic rocks which formed during the Svecofennian (1.9–1.8 Ga) stage. New Ar–Ar (hornblende and muscovite) and U–Pb (zircon and monazite) isotopic results from representative lithologies are used to shed further light on the geological evolution. With respect to the Ar–Ar isotopic system, somewhat variable dates (hornblende) are interpreted as cooling ages that indicate different uplift histories, following a 1.8 Ga metamorphic peak, at different sides of the Karesuando-Arjeplog deformation zone. Other post-1.7 Ga 40Ar/39Ar ages are suggested to reflect either a neocrystallisation (muscovite) or an event leading to isotopic resetting (hornblende). It is suggested that post-1.76 Ga crustal processes have influenced the Ar–Ar mineral systems during three relatively short-lived (a few tens of million years) stages; peaking at ~ 1.73 Ga, ~ 1.63 Ga and ~ 1.55 Ga. Tentatively, the timing of these stages is coupled with far-field effects that elsewhere are associated with the alkali-rich granitic magmatism forming part of the Transscandinavian Igneous Belt (the 1.73 Ga event) and Rapakivi massifs (the 1.63 and 1.56 Ga events). It is proposed that the N-S to NW–SE orientation of these vast, regional granitic complexes matches that of major deformation zones in northernmost Fennoscandia and that locally initiated hydrothermal fluids followed weakness zones in the crust and ultimately led to element mobilisation, new mineral growth and isotopic over-printing preferentially affecting shear- and ore zones. Graphical abstract

Exploring Near- and Far-Field Effects in Photoplethysmography Signals Across Different Source-Detector Distances.

Photoplethysmography is a widely used optical technique to extract physiological information non-invasively. Despite its large use and adoption, multiple factors influence the signal shape and quality, including the instrumentation used. This work analyzes the variability of the DC component of the PPG signal at three source-detector distances (6 mm, 9 mm, and 12 mm) using green, red, and infrared light and four photodiodes per distance. The coefficient of variation (CV) is proposed as a new signal quality index (SQI) to evaluate signal variabilities. This study first characterizes the PPG system, which is then used to acquire PPG signals in the chest of 14 healthy participants. Results show a great DC variability at 6 mm, homogenizing at 9 and 12 mm. This suggests that PPG systems are also sensitive to the near- and far-field effects commonly reported and studied in optics, which can impact the accuracy of physiological parameters dependent on the DC component, such as oxygen saturation (SpO2).

A novel wall interference correction method for airfoil

Corrections for wind tunnel experimental results are crucial when accounting for tunnel wall interference. This study introduces a new method, the non-uniform wall pressure signature method (NUWPSM), which is designed to address tunnel wall interference in airfoil. The improved wall pressure signature method (WPSM), an enhanced version of the WPSM, is developed to address the velocity disparities and systematic errors in pressure measurements between with and without model conditions. Furthermore, the NUWPSM considers the non-uniformity of the flow induced by the limited far-field effect in wind tunnel experiments. Utilizing experimental data from three different scaled models of the WA210 airfoil, the efficacy of both the Improved WPSM and NUWPSM is verified. Results indicate that the Improved WPSM exhibits superior capabilities in simulating the distribution of axial induced velocity along the wall compared to the traditional WPSM. Additionally, both the Improved WPSM and NUWPSM demonstrate comparable abilities in correcting tunnel wall interference, achieving precise corrections within an angle of attack range of −180° to +180°. Notably, the NUWPSM effectively captures the velocity non-uniformity induced by the limited far-field effect, thereby extending its applicability to a broader range of scenarios. Furthermore, the NUWPSM showcases enhanced robustness by eliminating human intervention in the singularity quantity and distribution.

Episodic cooling of the Hannan-Micangshan Dome at the northern margin of the Yangtze Block, Central China: Response to progressive convergence in the eastern Tethys since the Mesozoic

The Hannan-Micangshan Dome (HMD) is a Meso-Cenozoic intra-continental compressional tectonic belt that provides an excellent natural laboratory to study intra-continental deformation processes and geodynamic mechanisms in Central China. Although many low-temperature thermochronological studies have been conducted in the HMD, the timing of initial cooling/exhumation, rapid exhumation phases and their relationship to progressive convergence in the eastern Tethys are still poorly constrained. In this study, we present new multiple thermochronological analyses of apatite (AFT) and zircon fission track (ZFT), hornblende and muscovite Ar-Ar, and zircon U-Pb dating of granitoid and sedimentary rocks from the HMD. Granitoids from the HMD yield Proterozoic zircon U-Pb ages and slightly younger hornblende and muscovite Ar-Ar ages, indicating rapid cooling after emplacement. ZFT dating of granitoids yielded apparent ages of ∼208–140 Ma. AFT dating of Triassic-Cretaceous sandstones and Proterozoic granitoids yielded apparent ages between ∼117 and ∼58 Ma. Thermal modeling results suggest that the HMD has experienced the onset of cooling and exhumation since the Early Jurassic followed by three phases of rapid cooling/exhumation during the Late Jurassic-Early Cretaceous (∼160–100 Ma), Middle Eocene (∼40 Ma) and since the Late Oligocene-Early Miocene (∼23–15 Ma). The initial exhumation in the HMD by the Early Jurassic may be related to the closure of the Paleo-Tethys Ocean between the Kunlun and Qiangtang terranes. The Late Jurassic-Early Cretaceous rapid exhumation in the HMD can be related to the basement-involved thrusting triggered by the far-field effects of the ongoing collision between the Qiangtang and Lhasa terranes following the closure of the Meso-Tethys since the Late Jurassic. Two phases of rapid Cenozoic exhumation by the Middle Eocene and since the Late Oligocene-Early Miocene in the HMD were attributed to the far-field stress effects of the collision between the India and Asian plates and the lateral growth of the Tibetan Plateau. Therefore, we proposed that the episodic cooling since the Early Jurassic of the HMD at the northern margin of the Yangtze Block can be interpreted as being related to the progressive convergence in the eastern Tethys since the Mesozoic.

The Seismic Surface Rupture Zone in the Western Segment of the Northern Margin Fault of the Hami Basin and Its Causal Interpretation, Eastern Tianshan

The Eastern Tianshan region, influenced by the far-field effect of northward compression and expansion of the Qinghai-Xizang block, features highly developed Late Quaternary active faults that exhibit significant neotectonic activity. Historically, the Barkol-Yiwu Basin, located to the north of the Eastern Tianshan, experienced two major earthquakes in 1842 and 1914, each with a magnitude of M71/2. In contrast, the Hami Basin on the southern margin of the Eastern Tianshan has no historical records of any major earthquakes, and its seismic potential, mechanisms, and future earthquake hazards remain unclear. Based on satellite image interpretation and field surveys, this study identified a relatively recent and well-preserved seismic surface rupture zone with good continuity in the Liushugou area of the western segment of the Northern Margin Fault of the Hami Basin (HMNF), which is the seismogenic structure responsible for the rupture. The surface rupture zone originates at Kekejin in the east, extends intermittently westward through Daipuseke Bulake and Liushugou, and terminates at Wuzun Bulake, with a total length of approximately 21 km. The rupture zone traverses the youngest geomorphic surface units, such as river beds or floodplains and first-order terraces (platforms), and is characterized by a series of single or multiple reverse fault scarps. The morphology of fault scarps is clear, presenting a light soil color with heights ranging from 0.15 m to 2.13 m and an average displacement of 0.56 m, suggesting that this surface rupture zone likely represents the most recent seismic event. Comparison with historical earthquake records in the Eastern Tianshan region suggests that the rupture zone may have been formed simultaneously with the Xiongkuer rupture zone by the 1842 M71/2 earthquake along the boundary faults on both sides of the Barkol Mountains, exhibiting a flower-like structural pattern. Alternatively, it might represent a separate, unrecorded seismic event occurring shortly after the 1842 earthquake. The estimated magnitude of the associated earthquake is about 6.6~6.9. Given that surface-rupturing earthquakes have already occurred in the western segment, the study indicates that the Erdaogou–Nanshankou section of the HMNF has surpassed the average recurrence interval for major earthquakes, indicating a potential future earthquake hazard.

Chronology, structures and salt tectonics in the northern Kuqa Depression, NW China: Implications for the Cenozoic uplift of Tian Shan and foreland deformation

Foreland fold-and-thrust belts (FTBs) are shaped by the coupled influence of surface processes (e.g., erosion, sedimentation) and deep geological processes (e.g., plate rheology, flexure and kinematics) across various timescales. These processes record multiple phases of orogenic evolution and are crucial for understanding the interplay between mountain building and the sedimentary basin filling. In this paper, we conducted an integrated study including magnetostratigraphy of exposed strata, detailed field investigations and interpretations of subsurface seismic profiles in the northern Kuqa Depression. This study aims to elucidate the tectonic uplift of the Tian Shan by examining salt-related structures. The present findings reveal that diapirism in the study area commenced in the early Eocene and continued at least into the late Miocene. Notably, the Tuzimaza diapir has been significantly squeezed due to regional contraction since ∼5.3 Ma. The exposed growth strata were primarily compressional, rather than halokinetic, suggesting the lateral expansion of the Tuzimaza anticline since the latest Miocene (∼5.3 Ma). This expansion was a response to the far-field effects of the Indian-Eurasian collision. We propose that the local activation of the Tian Shan likely initiated in the early Oligocene (∼34 Ma), with three subsequent episodes of deformation occurring ∼24 Ma, ∼10 Ma and ∼ 5.3 Ma. The earlier episodes can be attributed to basement uplift in the northern Kuqa Depression, whereas the later episode starting at ∼5.3 Ma reflects more intensive deformation across the entire foreland, indicative of the steady outward growth of the Tian Shan. Collectively, all these tectonic events have contributed to the formation of the modern Tian Shan.

Basin inversion, drifting and hyper-extension in the Central Atlantic Ocean and Maghrebian Tethys as fluid driving mechanisms for the superimposed base metal mineralization events in the Jbel Bou Dahar carbonate-hosted Pb-Zn-Ba deposits (High Atlas, Morocco)

The Early Jurassic Jbel Bou Dahar reef-bearing carbonate platform in the eastern High Atlas, Morocco, contains numerous carbonate-hosted and fault-controlled Pb-Zn-Ba deposits, prospects, and showings. Combined field, petrographic and geochemical data, including REE + Y analyses, stable (C-O-S), radiogenic (SrPb) and noble gas (He, Ne, Ar) isotopic compositions, record two temporally distinct metallogenic events. Both events are related to post-rifting and inversion of the inherited Mesozoic Atlas paleorift. The ore deposits are thought to have been formed during large-scale episodes of transtensional basin evolution, which developed as a far-field effect of the drifting of the Central Atlantic Ocean and Maghrebian Tethys while the basin continued to invert in response to the ongoing convergence between the African and the Eurasian plates. The paragenetically earliest Zn-rich ore was generated in a transtensional setting coincident with the hyper-extension of Maghrebian Tethys and the initial stages of drifting and formation of the Central Atlantic passive margin. Crustal extension and high heat fluxes provided by the hot upwelling mantle would have triggered buoyancy-driven convection of deeply sourced fluids and maturation of organic matter dispersed within the host carbonates to produce hydrocarbons within an extensional basin setting. These relatively reduced Zn-rich ore-forming fluids acquired metals mainly through protracted interaction with the country rocks including the underlying Triassic siliciclastic series and the granitic basement rocks. Regional ENE- to E-W-trending major faults would have acted as conduits for upward fluid flow and traps for Zn-Pb-Ba mineralization. Conversely, the late Pb-rich mineralization stage II is broadly constrained to have occurred between ca. 70 Ma and 10 Ma and is thought to be related to the transition from orogenic shortening (late Eocene) to post-orogenic crustal extension and exhumation (early Miocene) following Alpine orogenic collapse. Mixing of down-ward percolating meteoric fluids and ascending rock-buffered hydrothermal brines that had previously equilibrated with the radiogenic basement rocks along with thermochemical sulfate reduction of transported sulfate and/or thermal cracking, would have been the main ore-forming processes that controlled ore deposition. Given these fluid characteristics and geodynamic settings, the Jbel Bou Dahar ore field is classified as a hybrid carbonate-hosted Pb-Zn-Ba district formed by the juxtaposition of two deposit types rather than one progressively evolving mineralizing system. From an exploration standpoint, new delineation here of the two metallogenic events provides valuable exploration tools for further targeting PbZn and barite resources in the Atlas system of North Africa and other areas where similar orogenic belts experienced post-rift subsidence and basin inversion.

Late Paleozoic to Mesozoic tectonic evolution of the Qinling Orogenic Belt: Structural and geochronological constraints from the Devonian Liuling Group, eastern Qinling area, China

The Late Paleozoic to Mesozoic tectonic evolution of the Qinling Orogenic Belt is not fully understood. To address this, structural analysis and rutile U-Pb dating were performed on the Middle–Late Devonian Liuling Group located along the northern margin of the South Qinling Belt (SQB). Detailed structural analysis reveals that the Liuling Group experienced four main deformation events (D1–D4). Initial D1 deformation is characterized by intrafolial folds (F1) and a regional penetrative foliation (S1). Subsequent D2 is marked by SW-vergent asymmetric, overturned folds and related crenulation lineation (L2). D3 and D4 are represented by, respectively, nearly E-W trending open folds and NNE-SSW trending centimeter-scale kink folds, both of which slightly modify D1 and D2 structures. Taking into account published chronological data, we propose that D1 and D2 occurred at 363–349 Ma and 332–318 Ma, respectively, and were associated with NE-SW oriented shortening during continental subduction of the SQB. Our new rutile U-Pb ages of 243–240 Ma provide a lower age limit for D3 deformation, which was related to N-S oriented shortening triggered by continental collision between the South China Block (SCB) and SQB along the Mianlue Suture Zone (MLSZ). Finally, D4 deformation was associated with the far-field effects of Late Jurassic subduction of the Paleo-Pacific Plate, which generated a WNW-ESE oriented shortening. Our findings suggest that continental subduction of the SQB continued until the earliest Late Carboniferous. Subsequently, the northern margin of the SQB experienced a Triassic metamorphic overprint triggered by collision between the SCB and SQB.

Paleozoic-Mesozoic multistage tectonic evolution of the North Qilian Shan revealed by detrital zircon U-Pb and fission-track double dating

Knowledge of the tectonic history of the North Qilian Shan contributes to our understanding of the formation of the Tibetan Plateau. However, when the North Qilian Shan were formed has been controversial. We report new detrital zircon U-Pb (n = 899) and double dating fission track and U-Pb (n = 450) results from nine samples of Lower Cretaceous and Oligocene sandstone units, integrating with published geochronology and thermochronology data in order to reconstruct the evolution history of the North Qilian Shan. Nine samples from this unit show detrital zircon fission track age populations that center at: 636–603, 495, 406–331, 290–266, 247–224, 193–151, and 144–102 Ma. These fission track data are older than their corresponding depositional ages, suggesting that the fission track ages are unreset and record magmatic-related cooling or exhumation stages of the North Qilian Shan since the Late Neoproterozoic. Deconvolved fission track peak ages document major cooling events associated with the opening of the North Qilian Ocean at 636–603 Ma. Late Cambrian peak age (495 Ma) is attributed to the early phase of the subduction of the North Qilian Ocean. The Devonian period exhibited a cooling phase between 406 and 381 Ma, corresponding to the collision event between the Qaidam terrane, Central Qilian Shan, and Alxa Block. The peak age of 331 Ma signifies the cooling event associated with the subduction of the Paleo-Asian Ocean. The peak ages during the Early-Middle Permian period (290–266 Ma) provide evidence of significant exhumation events that occurred during the Late Paleozoic era. These events were linked to the subduction of the Paleo-Tethys Ocean to the south and the Paleo-Asian Ocean to the north. The Triassic peak ages (247–224 Ma) unveil exhumation signals in the North Qilian Shan region that were generated by the far-field effect of the collision between the Qiangtang and Kunlun terranes. During the Jurassic (193–151 Ma) and the Early Cretaceous periods (144–102 Ma), the exhumation of the North Qilian Shan region was a consequence of the subduction of the Neo-Tethys Ocean and the collision between the Lhasa and Qiangtang blocks, respectively. The peak ages of the Xinminpu Formation in the Early Cretaceous (123–121 Ma) are in close proximity to their depositional age (125–105 Ma), indicating that the North Qilian Shan underwent rapid exhumation during this period. The peak ages observed in the Oligocene Baiyanghe Formation (31–24 Ma) from 144 to 102 Ma, indicate that it has been influenced by the recycled sediments originating from the Cretaceous Xinminpu Formation. The North Qilian Shan gradually emerged during the late Paleozoic and Mesozoic eras, providing the foundation for its subsequent reactivation in the Cenozoic era. The multi-stage cooling or exhumation events of North Qilian Shan since Late Neoproterozoic reflect the complex formation process of the northeastern margin of Tibetan Plateau.

Earthquake Sequence Simulation and Hazard Analysis in the Tianshan Orogenic Belt and Adjacent Areas

ABSTRACT The Tianshan orogenic belt is located in central Eurasia. Its tectonic deformation and seismicity are primarily influenced by the far-field effect of the India–Eurasia collision. It is one of the regions with the most intensive seismicity in China. Understanding the mechanisms of earthquake nucleation in this region is a hot topic in the seismicity community. The numerical simulation of earthquake sequences is an efficient measure for comprehensively exploring earthquake occurrence characteristics, tectonic loading, and subsequence patterns. It is also an important method for predicting and mitigating earthquake disasters. This study utilized a finite-element model to investigate the evolution of regional historical earthquakes via the split-node method. Coulomb failure stress analyses from interactions of simulated historical earthquakes since 1900 indicate that the Taxkorgan fault may be prone to the next significant earthquake event.

Comparative analysis of blast prediction software for far-field shock wave effects behind a blast wall

This paper investigates a selection of current and emerging software used in the prediction of overpressure generated through the detonation of a high explosive in the far field behind a blast wall. In particular, this paper compares the software Autodyn, blastFoam, ProSAir, Viper::Blast and WALAIR++. These packages are compared by simulating a 100 kg TNT explosive charge at a stand-off distance of 25 m from a complex structure, then reviewing the performance in terms of the overpressure results, speed of each modelling package, the degree of effect from mesh, and domain sizes and ease of use. A live experimental trial representing the simulation was also performed, although it used a similar but different explosive, for a high-level comparison. The live-trial instrumentation design details are reviewed and compared with best practice. The choice of software is found to lead to variations in peak pressure predictions of 28%, specific impulse by 10% and the simulation speed can vary by a factor of up to 1600 for this type of study. This shows that the choice of blast software package can have a significant impact on the accuracy and attainability of blast predictions.

AC-driven QLED based on far-field effect of Au NPs

As the pixel size continues to shrink, conventional display devices are unable to satisfy the increasing demand. Therefore, a novel light-emitting device has garnered significant attention. This device emitted light under an alternating current (AC) electric field and blocked the injection of external carriers by using the insulating layer. However, at the same time, this approach leads to a reduction in brightness. In this paper, we have realized the performance enhancement of AC-driven QLEDs by incorporating Au NPs of different sizes in PEDOT:PSS. Our investigation reveals that Au NPs of greater size exhibit a notable enhancement of the brightness, rising from 5512 cd/m2 to 7234 cd/m2, representing a substantial increase of approximately 31.2 %. It demonstrates the great potential of the "far-field" effect in AC-driven QLEDs.

Deformation and displacements of Earth’s surface in Turkish earthquakes era in February 2023 by geodesy data

The work analyzes the connection between a series of Turkish earthquakes in February 2023 and coseismic displacements and deformations on the Earth's surface. In areas of seismic rupture during the five days, there are recordings of three earthquakes on February 6 with magnitudes 7.8, 6.7, 7.5 and then for 5 days period – 42 events of magnitude 4.5–6.0. This work analyzed data obtained by various geodesy methods in the epicentral region. Coseismic effects in a 300 kilometers zone, covering a significant part of the East Anatolian Fault, are considered. Relative displacements up to 6 m have been recorded, with an average value 4 m. When for studying far-field effects, we used GPS network data from 27 international stations, of which seven stations located in Turkey. For the closest to the epicenters of the main aftershock on February 6, 2023, MERS station received coseismic 3D displacements up to 20 mm. The displacement and deformation fields have been constructed according to IGS data. Rates of coseismic deformations in the far zone reach up 10–8 , which is an order of magnitude higher than the background values of 10–9 . Post-seismic horizontal and vertical displacements rates of the Earth's surface in areas of Turkey, located to the southwest of the earthquake epicenters can be associated with floods. A study of displacements rates and deformations of the territory was carried out Turkey and its surroundings in the era of 2017–2023. Highlighted decrease displacement rates two years before seismic activation in 2023. The resulting picture of displacement and deformation rates reflects a current processes in the territory located on the borders of Anatolian Block and tectonic plates: Eurasian, Arabian, and African.

Eccentricity control on fluvial sedimentation in the tropics during the Middle-Late Pennsylvanian icehouse (∼306–314 Ma, Upper Silesian Basin)

Far-field effects of the Late Paleozoic glaciation (∼340–260 Ma) recorded in well-dated stratigraphic intervals of the Pangea can be instrumental in detecting the short-term variability of icehouse climate and deconvolving the climate mechanisms. This study examines the Cracow Sandstone Series (CS), which provides a snapshot of the Middle to Late Pennsylvanian (∼306–314 Ma) fluvial sedimentation in the eastern equatorial Pangea (Upper Silesian Basin, ∼2°N paleolatitude). Spectral estimates of borehole lithological data suggest predominant ∼100-kyr eccentricity pacing of coal-bearing fluvial cycles and persistence of this pattern across the onset of Late Pennsylvanian aridification. The immediate climatic and depositional controls involve changes in seasonal precipitation along the Intertropical Convergence Zone and resulting fluctuations in sediment input. The prominence of eccentricity pacing and suppression of precession-scale variability in the fluvial environment contrasts with the frequency spectra of seasonal insolation series – an issue comparable to the “100-kyr problem” of the Late Pleistocene. The traditional explanation considers the eccentricity component being imposed as a far-field response to glaciation, analogous to the Pleistocene carbon-cycle feedback. Here we propose an alternative possibility that calls upon time-integrated insolation at the equator and the role of semi-annual wet/dry cyclicity in transferring variance from precession-scale insolation changes to the modulating eccentricity term. Autogenic processes in the fluvial system might have participated in “shredding” the precessional and semi-precessional signals. The alternative scenario is decoupled from high-latitude climate and would imply a muted climate sensitivity of the eastern equatorial Pangea to glaciation. The individual options cannot be evaluated with the Upper Silesian data alone, but offer testable hypotheses, potentially helpful in revealing the short-term structure of glaciation and climate teleconnections during the Late Paleozoic.

Relationship between electrical conductivity, metallogeny, and lithospheric structure in south China

The South China Block (SCB) is located at the junction of the Pacific, Eurasian, and Indo-Australian plates. Their interaction led to large-scale multi-stage mineralization in the SCB during the Mesozoic. Several regional ore-concentration areas, such as the Middle-Lower Yangtze Metallogenic Belt (MLYMB), the Qinzhou-Hangzhou Metallogenic Belt (QHMB), the Wuyishan Metallogenic Belt (WYMB), and the Nanling Metallogenic Belt (NLMB) were formed during this process. However, the dominant mineral types of these metallogenic belts are different. To study the deep mechanisms of the different metallogenic types developed in the same tectonic background at almost the same period, the magnetotelluric sounding (MT) data from 691 sites located mainly within the eastern SCB are employed to obtain a regional lithospheric 3-D resistivity model.It could be concluded from the resistivity model that deep low-resistivity anomalies and mantle upwelling channels mainly controlled almost all the Mesozoic deposits. Large-scale low-resistivity bodies extend from the crust to the upper mantle beneath the MLYMB and the QHMB, interpreted as channels of mantle-derived magma and melts/fluids containing metallogenic elements upwelling. However, the MLYMB and the QHMB have different upper crustal ore-conducting and ore-controlling structures, thus forming porphyry copper and copper-bearing tungsten deposits. Small-scale low-resistivity anomalies are invading the high-resistivity crust in the NLMB. And remelting the upper crust, mixing, and intrusion of crust-source magma, enriching tungsten-tin elements near the NLMB. Larger-scale low-resistivity anomalies exist deep in the WYMB, remelting the lower crust and resulting in the formation of porphyry copper in it. Significantly, the upper-mantle low-resistivity anomalies beneath the eastern SCB show a spatial distribution that is gradually shallowing from south to north, probably indicating that the asthenospheric materials are upwelling from south to north, corresponding with the changing progressively of magma and metallogenic activities. We propose that the lithospheric delamination and asthenospheric upwelling caused by the far-field effects of the Paleo-Pacific Plate subduction are the sources of solid magmatic activities and related metallogeny.

Generalizing electroosmotic-flow predictions over charge-modulated periodic topographies: tuneable far-field effects

The classical Helmholtz–Smoluchowski (HS) model of electroosmosis holds for homogeneously charged interfaces in contact with a fluid layer bearing an equal and opposite net charge. However, inhomogeneities in the surface charge and topography are inevitable, either as practical materials and fabrication artefacts, or at times as deliberately introduced modulations for flow control. In an effort to arrive at an analytically tractable theoretical framework for addressing the underlying electro-mechanical coupling, here, we generalize the traditional HS theory to an extent where both the surface charge and topographies may bear arbitrary and independent periodic forms. Using a spectral-asymptotic approach, we further arrive at closed-form expressions for describing the resulting electroosmotic pumping for topographic features with small characteristic amplitude to pattern period ratio, as relevant for most practical scenarios. We subsequently execute full-scale numerical simulations without any restrictions on the surface charge and topography variations to assess the efficacy of the theoretical framework. The corresponding test beds include distinctive signature patterns – for example, a square-wave surface charge distribution on trapezoidal pit topographies. Our results reveal that the charge–topography interplay induces an anisotropic flow drift, deviating from the classical HS paradigm. This, in turn, provides new quantitative insights into highly selective electroosmotic flow control via judicious design of the charge and topographical patterns, resulting in controllable accentuation, attenuation, nullification, deflection and even complete reversal of the flow. Our analysis further establishes a provision of estimating the zeta potentials of naturally ‘contaminated’ surfaces, as well as explaining the electrophoresis of large inhomogeneous particles; a paradigm that remained to be explored thus far.

Cenozoic deformation of the Weihe Graben in central China: Insights from Analogue modeling

The Weihe Graben is located in the composite area of the Tethys-Himalayan tectonic and circum-pacific tectonic domains and is an essential structural feature related to Cenozoic intracontinental deformation. However, two different hypotheses, sinistral strike-slip, and extensional mechanism, are proposed for the origin of this graben. In this study, we designed crust-scale analog models based on fault kinematics to better understand the deformation and dynamic mechanisms of the Weihe Graben. Fault kinematics shows early sinistral strike-slip and NW-SE extensional deformation and late NE-SW, S-N, and NW-SE extensional deformation. Our experimental results reveal that Model C1 (sinistral strike-slip + NW-SE extension) is the most similar to the geological structure of the Weihe Graben in the Paleogene. Furthermore, the NE-SW extension results in two larger subsidence areas in the northeast and southwest of the basin, similar to the formation of the two depressions during the Miocene. The S-N extension causes the basin to expand southward and northward, consistent with the sedimentary characteristics of Weihe Graben in the Pliocene. The NW-SE extension leads to relatively strong fault activity in the northwest and southeast of the basin, resembling the active fault characteristics since the Quaternary. Therefore, we propose that the Weihe Graben formed by a strike-slip and extensional combined mechanism in the Eocene-Oligocene, influenced by the far-field effects of the Indian-Asian collision and crust-mantle processes triggered by the stagnant paleo-Pacific plate. Subsequently, during the Neogene-Quaternary, the graben’s development shifted towards an extensional regime under the influence of the eastward extrusion of the Tibetan Plateau.

Strain partitioning, transfer and implications for the ongoing process of intracontinental graben formation in the northwestern margin of the Ordos block, China: insights from densified GNSS measurements

SUMMARY The northwestern margin of the Ordos block is structurally separated by the Yinchuan–Hetao graben system. As one of the most active intracontinental graben systems within the Eurasian continent, its kinematic pattern of crustal extension is crucial for unraveling the ongoing processes of intracontinental graben formation, while it remains unclear principally due to a lack of geological constraints on crustal deformation. We obtained and analysed a densified GNSS (Global Navigation Satellite System) velocity field in this region. Our results suggest that the western margin of the Hetao graben exhibits the NW-directed crustal extension (∼ 1.1 mm yr−1), which can be attributed to the conjugate transtension resulting from the left-lateral motion along the E–W-trending northern boundaries of the Alashan and Ordos blocks, as well as the right-lateral motion along the N–S-trending western margin of the Ordos block. Additionally, in response to the NE-directed extrusion of the Tibetan Plateau, the Alashan block undergoes approximately NE-directed contraction (4.9 ± 1.1 nanostrain yr−1) and NW-directed extrusion (2.8 ± 0.8 nanostrain yr−1), which vacates space for the crustal extension of the Yinchuan graben with a rate of 0.9 ± 0.1 mm yr−1. Although it is challenging to determine whether the left-lateral motion (approximately 1 mm yr−1) along the E–W-trending Hetao graben is the far-field effect of western Pacific subduction, the gradual decrease in right-lateral motion from the N–S-trending western margin of the Ordos block toward the north side of the Yinshan Orogen manifests the far-field effect of the Indo-Eurasian plate convergence extending into the Mongolian Plateau.

Dynamic Response Analysis Method of a High-Strength RC Beam Subjected to Long-Duration Blast Loading

An analysis method of normalized pressure–impulse (P-I) diagrams related to the ductility ratio of structural components is proposed, to quickly estimate the dynamic response of high-strength reinforcement concrete (RC) beams subjected to long-duration blast loading. Firstly, the overall bending deformation mode of RC beams is uncovered via explosion tests in a closed chamber, where the durations of the near-planar blast loadings are varied within 80–105 ms. Then, a single-degree-of-freedom (SDOF) model is established based on the bending deformation mode. The resistance function for the uniform pressure loading is developed using a novel approach, consisting of (1) developing and benchmarking a three-dimensional (3D) improved steel–concrete separated finite-element (FE) model; (2) using the benchmarked FE model to conduct numerical simulations for uniform pressure loading; and (3) idealizing the resistance function for uniform pressure using a bilinear relationship. Finally, the SDOF model is used to conduct parametric analyses and develop a normalized P-I diagram that can be used to analyze or design RC beams for far-field blast effects. This P-I diagram is verified using results from blast load tests that are primarily in the dynamic region. A total of 188 additional 3D nonlinear FE analyses of RC beams are conducted to expand the database in the impulse and quasi-static regions. Considering the limitations of the proposed method in predicting the shear-dominated deformation and the fracture behavior of members, the P-I diagram is applicable to the dynamic response of the bending deformation of members under far-field explosion, which can provide an important reference for the blast-resistant design and analysis of high-strength RC beams.