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The Zaozigou gold deposit lies south of the Xiahe–Hezuo regional fault zone in the western Qinling orogenic belt and contains many intermediate to felsic dikes. Diorite porphyry, quartz diorite porphyry and biotite diorite porphyry are mineral‐bearing dikes, whereas granite porphyry is unrelated to gold mineralization. To compare the relationship between different dikes and mineralization, this study analyzed the cathodoluminescence (CL) of zircon crystals in all four types of dikes exposed in the Zaozigou deposit, using a zircon typological classification. The formation temperature of the granite porphyry (734°C) was higher than the average temperature of the other three types of dikes (704°C), whereas the former's alkalinity index (395) was lower than the average alkalinity index of the other three dikes (425). The ΣREE amount of granite porphyry (147.18 ppm) was smaller than the average ΣREE amount of the other three dikes (246.80 ppm) and its δEu value (0.33) was larger than the average δEu values of the other three dikes (0.30). The U‐Pb ages of zircon in the four types of dikes were relatively consistent with the crystallization ages of approximately 240 Ma, which indicates that all four types of dikes intruded in the Middle Triassic. Compared to the other three ore‐bearing dikes, the morphology of the zircon crystals in the barren dikes evolved from S13 to S5 and then returned to S13. These results indicate that the barren dike underwent an increase in temperature and a decrease in alkalinity, which may be an important reason for the absence of mineralization. [ABSTRACT FROM AUTHOR]

A new type of small, dry-filled geotextile tubes is introduced, that, in a stacked formation, can be used as dike cores. Dikes made out of these tubes consist of great potential regarding more resilient flood protection. The geotextile protects the fill from erosion, enabling steeper slopes along with reduced material and less land consumption. The behavior and potential failure mechanisms of such dikes were investigated first by literature research and second by full-scale hydraulic model tests under systematic variation of tube number, number of textile layers, filling ratio, and fill material. The tubes were exposed to the loads of seepage and overflow. Most relevant failure mechanisms were seepage-induced sagging, lateral displacement, and overturning of the upper tube due to overflow. During seepage, the tube height was reduced by up to 22.8 % due to sagging. Overflow led to a lateral displacement of up to 13 cm and, at overflow heights of 23.1 cm and 26.8 cm, to overturning of the upper tube. The present results give new insights into the behavior of innovatively constructed geotextile tubes under hydraulic loads and serve as basis for the development of design rules. • Dry-filled geotextile tubes represent a promising way towards resilient river dikes • Tube behavior is investigated experimentally under parameter variation • Sagging and lateral deformation must be considered in design rules • The tubes withstand overflow heights of >20 cm • Compacting the tubes increases the stability [ABSTRACT FROM AUTHOR]

Understanding the geometric dimensions of pipes formed during backward erosion piping (BEP) is crucial for comprehending the BEP mechanism and conducting numerical simulations. However, current research primarily focuses on the two-dimensional morphology of pipes, with a lack of sufficient understanding regarding their three-dimensional (3D) characteristics. To study the 3D geometric characteristics of the pipe, the 3D size of the pipe was measured and analyzed using the gypsum injection method and 3D laser scanning method in this study. The variations in pipe depth, width, and the ratio of width to depth were investigated in detail. And the influence of cover plate roughness and sand compactness on the 3D geometry of the pipe was clarified. It is found that the cross-section shape of the pipe is approximately rectangular, with the horizontal scale being significantly larger than the vertical scale. With increasing distance from the outlet hole, there is a gradual decrease in both the depth and width of the pipe. The relationship between the pipe's depth and width with respect to its length can be described using linear functions. As the compactness of sand layer increased, the depth and width of the pipe decreased to a certain extent. [ABSTRACT FROM AUTHOR]

Backward erosion piping constitutes a major threat for dikes on sandy or silty foundations during high water and floods. This erosion mechanism results in the formation and development of shallow hollow spaces (pipes) at the interface between the impermeable top layer and the aquifer. Erosion at the tip of the pipe determines the progression of the pipe towards the upstream side. A valid criterion should be developed to predict the critical local gradient at which erosion at the pipe tip occurs. Based on the failure mode of the tip of the pipe that the erosion near the toe of the scarp of the pipe tip causes the collapse of the scarp, in combination with the seepage field near the pipe tip, analyses are conducted regarding the equilibrium of forces on single particles at the toe of the scarp and a group of particles of the scarp. The conditions for incipient motion for particles at the pipe tip are determined. And a novel criterion for predicting the critical local gradient at the pipe tip is developed, which is essential for assessing the risk of pipe progression in practice. [ABSTRACT FROM AUTHOR]

The Cracked Mountain edifice is a basaltic subglacial volcano (i.e. tuya) situated in southwest British Columbia, Canada. The edifice is dominated by subaqueously deposited, massive to poorly stratified, variably palagonitized lapilli tuffs intruded by syn-eruptive dikes and lobes of peperitic pillow-lavas (15–20 vol.%); minor stacks of pillow-lava are found on the margins of the edifice. Here, we present mineralogical, textural, and physical property data for 134 sample cores from the palagonitized volcaniclastic deposits. Our sample suite includes three specific field environments defined by proximity to intrusive heat sources: (i) proximal (< 1 m) deposits (ENV1), (ii) deposits within 1–5 m of intrusions (ENV2), and (iii) deposits far removed (> 5 m) from discernible heat sources (ENV3). The dataset comprises mineralogy and measurements of density, porosity, permeability, P-wave velocity, uniaxial compressive strength, and paleomagnetism. Increased palagonitization is marked by increases in authigenic mineral abundance (smectite and analcime), density, strength, and P-wave velocity and concomitant decreases in porosity and permeability. Paleomagnetic data show a common pole direction recorded by all volcanic deposits indicating volcanism occurred within a single paleomagnetic moment (< 200 years). Palagonitization of the volcaniclastic deposits is driven by heat supplied by syn-eruptive intrusions and is most intense in ENV1, where dikes raised temperatures (> 150 °C) for a prolonged duration (< 1 year), and weakest in ENV3 deposits reheated to lower temperatures (< 150 °C). The timescale of palagonitization was short and coincident with the emplacement and cooling of syn-eruptive intrusions. The mapped intensity of palagonitization and thermal modelling are used to define a ‘palagonite window’ as a function of time and distance from heat sources (i.e. dikes). [ABSTRACT FROM AUTHOR]

This paper presents the results of isotope-geochronological and petrological studies of gabbroic and combined diorite-granite dikes located in the eastern part of the Kaakhem magmatic area. Both groups of dikes cut through diorite-tonalite-plagiogranite associations of different ages (489±5 and 476±4 Ma). Zircons from granitoid of mingling dikes have an age of 477±3 Ma (LA-ICP-MS). The age of the gabbroic dikes was determined by LA-ICP-MS (zircon) and Ar-Ar (amphibole) methods and is 454±10 and 450±6.3 Ma, respectively. Similar contents of major and trace elements in basic and intermediate rocks of dikes indicate their formation from a single source with subduction characteristics. The salic rocks of the combined dikes vary in composition and are close to the heterogeneous diorite-tonalite-plagiogranite-granite associations of the host rocks. The formation of dike complexes occurred at the collisional stage of development of the Kaakhem magmatic area and is associated with the development of local extension zones.

Consideration is being given to the geochemical composition of the rocks, representing the hidden part of the volcanic and intrusive material in the structure of the Yenisei-Khatanga Trough (YKT), in relation to its belonging to a large igneous province (LIP) of Siberia. The geochemical characteristics of mafic rocks, presenting in the sedimentary complexes of the YKT, correspond to three types of mafic rocks allocated to the Siberian LIP: Nadezhdinsky (low Ti), Morongovsky (low Ti), and, in limited quantities, Ivakinsky (rift-related high Ti). Based on the seismic data, there was constructed a deep structural-tectonic cross-sectional model, and there was considered the position of mafic intrusions in the sedimentary section in the western junction zone of the Siberian Platform and the Kara (Taimyr-Severozemelsky) orogen. The seismic data show an anomalous area in the lower crust and at the crust–mantle boundary immediately below the YKT depocenter, whose seismic section is characterized by a chaotic scattered wave field with no reflective boundaries.

Inland navigation structures (INS) facilitate transportation of goods in rivers and canals. Transportation of goods over waterways is more energy efficient than on roads and railways. INS, similar to other civil structures, are aging and require frequent condition assessment and maintenance. Countries, in which INS are important to their economies, such as the Netherlands and the United States, allocate significant budgets for maintenance and renovation of exiting INS, as well as for building new structures. Timely maintenance and early detection of a change to material or geometric properties (i.e., damage) can be supported with the structural health monitoring (SHM), in which monitored data, such as load, structural response, environmental actions, are analyzed. Huge scientific efforts are realized in bridge SHM, but when it comes to SHM of INS, the efforts are significantly lower. Therefore, the SHM community has opportunities to develop new solutions for SHM of INS and convince asset owners of their benefits. This review article, first, articulates the need to keep INS safe to use and fit for purpose, and the challenges associated with it. Second, it defines and reviews sensors, sensing technologies, and approaches for SHM of INS. Then, INS and their components, including structures in ports, are identified, described, and illustrated, and their monitoring efforts are reviewed. Finally, the review article emphasizes the added value of SHM systems for INS, concludes on the current achievements, and proposes future trajectories for SHM of INS and ports. [ABSTRACT FROM AUTHOR]

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We have studied the geological structure, material composition of the ores, and the age of the Nizhny Birkachan volcanogenic gold–silver deposit discovered recently. The ore bodies consist of veins and vein-streak zones of adularia-carbonate-quartz composition; they lie in granodiorite porphyries with U‒Pb zircon age (ID-TIMS) equal to 335 ± 2 Ma. The ores are low sulfide, low silver (Au/Ag = 1–2), with pyrite dominating the ore minerals. The Ag minerals are tennantite, Ag sulfide, native gold and silver, and hessite. From an ore vein we obtained an adularia-based 40Ar/39Ar age equal to 169 ± 4 Ma, which reflects the rejuvenation of the isotopic argon system after the emplacement of a dike of unaltered Jurassic basites that cuts through the ore body. The Nizhny Birkachan deposit has a geological structure and ore composition that are very similar to those of other Au-Ag deposits at the Kedon volcano-plutonic belt such as Kubaka and Birkachan; it was also formed in the age span 290–335 Ma. [ABSTRACT FROM AUTHOR]

This article presents an investigation of ground movement measurements based on a combination of TerraSAR-X and Sentinel-1 data, in opposite tracks, aiming to detect ground de-formation of the remaining dikes of Germano mine, after the Fundão dam collapse. The differential interferometry technique SBAS (Small Baseline Subset) was applied to obtain the deformation of the surface in different Line of Sight (LoS), in order to carry out the vector decomposition and generate the deformation measurements in the vertical and horizontal directions. A set of 37 single-look complex (SLC) images of TerraSAR-X (TSX), acquired during the period from 19 February 2016 to 15 May 2017, and 37 SLC images of Sentinel-1, acquired from 8 February 2016 to 15 May 2017, were used to perform this investigation. For the TerraSAR-X interferometric processing, a coherence threshold of 40%, 4 looks in range and 2 looks in azimuth, 1200 m of atmospheric filter, and 10 % of max normal baseline of the critical were used. For the Sentinel-1 interferometric processing a coherence threshold of 26%, 8 looks in range and 2 looks in azimuth, 1200 m of atmospheric filter, and 20% of the of max normal baseline of the critical were used. For both sensors a digital elevation model generated by Pleiades 1-A was used for removing the topographic phase component. The final results were consistent with the topographic in situ measurements, providing key information to make crucial decisions regarding risks, or even mitigation, repairs or emergency response, as well as for a better understanding of the on-going instability phenomena affecting the dikes and dams.

Several experimental runs have been conducted in a rectangular flume in order to investigate the effect of composite hydraulic structures and emerged dikes on flow hydraulic characteristics. The composite hydraulic structures used in this study are composed of a rectangular weir and gate with a different dimensional model. The dikes' structure is simulated by wood sheets of 10 cm height with two lengths, 1.0 and 1.5 cm. Three dike arrangements have been adopted in this study and installed downstream of the composite hydraulic structure. These arrangements consist of one side, both sides, and zigzag arrangement. Each dike arrangement has three cases with different dike numbers and spacing values. All the experiments have satisfied the submerged flow condition. The investigation of the flow cross-sectional area that passes the gate and weir of the composite structure and the dike arrangements, numbers, and lengths have been observed to find their effects on downstream average water depth, actual discharge, discharge coefficient of the composite structure, upstream and downstream Froude numbers, and downstream Reynolds number. The main finding in this study is that the existence of dikes downstream of the composite structure causes an increase in the downstream water depth without any conflict or fluctuation in the workability of the composite hydraulic structure. This study shows reasonable and noticeable results for Froude number, flow velocity, head losses, and water surface profile with distance in the downstream region. The experimental work is supported by adopting the statistical test to inspect the suitability and the acceptability of the average downstream water depth. It is strongly stated that all the observed data follow the normal distribution. [ABSTRACT FROM AUTHOR]

The paper presents detailed geological, petrographic, geochemical, and isotope data on the dolerites from dykes of the Baikal dike subswarm in the central part of the Baikal basement inlier of the Siberian craton. The main geochemical and isotope criteria were identified for classifying the dolerites that are similar in geological–structural position and mineral composition into three geochemical groups. Provisional age estimates of the dolerites are presented. The dolerites of the first and, perhaps, second groups compose Neoproterozoic (715 Ma) dikes. The first group includes medium- to coarse-grained dolerites, which form thick (more than 5–10 m) dikes. The dolerites of this group are characterized by low concentrations of Th (0.6–2.1 ppm) and Nb (3.3–9.2 ppm) and by ɛNd(T) = ‒0.5 to ‒3.9. Considered together, the geochemical and isotope data show that these dolerites could be produced as a result of the melting of a mantle source produced by mixing mantle components close in composition to oceanic plateau basalts and subduction-related subcontinental lithospheric mantle. The second group includes fine-grained dolerites from thin (1–5 m) dikes, including dikes located in contact with the dikes of the first group. The dolerites of the second group are characterized by higher concentrations of Th (3.0–5.3 ppm) and Nb (9.8–21.1 ppm) and by ɛNd(T) = –5.3 to ‒6.0. Geochemical and isotopic data on the dolerites of the second group indicate that continental crustal material was added to the mantle source unified for the dolerites of first and second groups. The third group includes medium-grained dolerites, which make up individual dikes that are contrastingly different in geochemical and isotope characteristics from the Neoproterozoic dolerites of the first and second groups. Dolerites of this group show low concentrations of Th (0.6–1.6 ppm) and Nb (2.7–5.1 ppm) at low values of (Th/La)pm (0.29–0.71) and 143Nd/144Nd (0.511223‒0.511544), which indicates that these dolerites may have been generated as a result of the melting of the subcontinental lithospheric mantle enriched in subduction components. Dolerites of the third group exhibit geochemical characteristics close to those of Paleoproterozoic (1.84 Ga) dikes of the South Siberian post-collisional magmatic belt. [ABSTRACT FROM AUTHOR]

Abstract The flood protection embankments of Hungary and Europe face numerous challenges. Some dike bases were constructed more than 200 years ago; since then, they have been elevated and extended. Because of these iterative adaptations, the dikes bear many construction errors, which can trigger failures and slides. Due to climate change, droughts and low-water periods of the rivers in central Europe are becoming more frequent. As a result of these effects, the water balance of the dikes can alter and desiccate in the long term. The most staggering fissures appeared on dikes built from clays susceptible to volume change. The General Directorate of Water Management ordered a comprehensive survey of dike pavement cracks in Hungary. This was one of the most extensive surveys of such kind. Hungary has some 4400 km of primary flood protection embankments, out of which 1250 km is paved. There are multiple reasons why the pavement of an embankment can crack. The main features of crack patterns related to clays with shrink-swell potential are identified. The results of international studies and the present survey are synthesised. The main objective of this paper is to draw a correlation between drought (aridity) zones, plasticity index of the soil samples, and crack thickness.

Dikes of Paleoproterozoic ultramafic rocks from the Kun-Manie area were studied within the southeastern framing of the Siberian Platform. At the end of the Paleoproterozoic, this area was spanned by the processes of overthrust faultings, the latest of which were accompanied by the emplacement of mafic-ultramafic dikes and sills that control the distribution of Cu–Ni–PGE sulfide mineralization. The petrographic texture of ultramafic dikes suggests their emplacement in tectonically active settings. The elevated concentrations of LREE relative to HREE coupled with other data allowed us to ascribe them to high-Mg ultramafic rocks of the picrite–tholeiite series, which were derived from picrobasaltic rather than from ultramafic magma. The REE level and normalized patterns in ultramafic rocks indicate the involvement of sufficiently enriched sources in the generation of primary melts, which produced rocks that radically differed from peridotites of ophiolite associations and typical komatiite melts. In terms of trace-element patterns and contents of indicator elements (Nb, Yb and Th), they are close to an E-MORB type "enriched" mantle source, but differ in the lower REE concentrations. The Zr/Y–Nb/Y relations in the ultramafic rocks suggest a nonplume source of their primary melts in the upper depleted mantle. Rocks derived from such a melt are characteristically enriched in fluid components (S, Cl, F, As, Te, Se, and H2O), which is evident in the presence of hydroxyl-rich minerals: amphiboles and phlogopite of igneous origin. The ore-forming system evolved from Ni-bearing at the early magmatic stage during the formation of disseminated mineralization to Cu-rich at the postmagmatic stage. The geological data indicate that it was formed during the collision between the Paleoproterozoic island arc and the microcontinent. The combination of subduction and intraplate geochemical characteristics in magmatic rocks is characteristic of a transform margin as a result of the oceanic (Upper Maya) and continental (Uchur) microplates sliding horizontally relative to each other. [ABSTRACT FROM AUTHOR]

In this work, we described the patterns of formation and distribution of gold occurrences of various morphological types in the terrigenous sequence of the Upper Yakokutsk graben depression. We characterized the zones of ore-bearing dislocations with increased permeability within the ore region confined by regional faults. Such zones with a frame-block structure forming the nodes of conjugation of regional structures are favourable for their repeated resumption and correspond to the most prospective areas. The study of native gold from ores and surrounding metasomatites showed a large variation in its fineness, based on which we can assume that the gold ore zones were repeatedly renewed from the Middle Jurassic to the Early Cretaceous. A correlation was noted for several subordinate structures: zones of ore-bearing dislocations – structures of prospective areas – ore bodies of various morphologies. The terrigenous sequence is considered not only as a structure-forming unit but also as a component involved in hydrothermal ore formation due to the presence of carbonaceous siltstones layers. The proposed model of the gold ore region makes it possible to allocate the most promising prospective areas. The presence of similar graben depressions developed in prospective ore regions within the Central Aldan ore district indicates the likelihood of identifying common patterns of endogenic mineralization within them.

Variable single and/or swarms of post-granitic dikes are widespread at Gabal Serbal, Southwestern Sinai, Egypt. The present article aims to identify and discriminate these multiphase dikes through detailed geological, petrographical, and geochemical examinations. These dikes are classified into two subphases: (1) acidic dikes (porphyritic dacite, microgranite, granophyre, and alkaline granophyre dikes); and (2) basic dikes (basalt and dolerite dikes). They range from vertical or steeply inclined bodies, 0.5–15 m wide, pink to black color, and NE–SW to N–S directions. Acidic dikes with different mineralogical constituents have medium to high k-characters, originating from calc-alkaline magma and extruded in a volcanic arc environment. In contrast, basic dikes have medium k-characters, originating from tholeiitic magma and developing within a plate environment. Basic dikes are enriched with opaque minerals, where the basaltic dike contains iron oxides (magnetite and hematite), such as apatite in addition to copper minerals. Dolerite dike comprises magnetite, titanomagnetite, and pyrite.

This article presents an investigation of ground movement measurements based on a combination of TerraSAR-X and Sentinel-1 data, in opposite tracks, aiming to detect ground de-formation of the remaining dikes of Germano mine, after the Fundão dam collapse. The differential interferometry technique SBAS (Small Baseline Subset) was applied to obtain the deformation of the surface in different Line of Sight (LoS), in order to carry out the vector decomposition and generate the deformation measurements in the vertical and horizontal directions. A set of 37 single-look complex (SLC) images of TerraSAR-X (TSX), acquired during the period from 19 February 2016 to 15 May 2017, and 37 SLC images of Sentinel-1, acquired from 8 February 2016 to 15 May 2017, were used to perform this investigation. For the TerraSAR-X interferometric processing, a coherence threshold of 40%, 4 looks in range and 2 looks in azimuth, 1200 m of atmospheric filter, and 10 % of max normal baseline of the critical were used. For the Sentinel-1 interferometric processing a coherence threshold of 26%, 8 looks in range and 2 looks in azimuth, 1200 m of atmospheric filter, and 20% of the of max normal baseline of the critical were used. For both sensors a digital elevation model generated by Pleiades 1-A was used for removing the topographic phase component. The final results were consistent with the topographic in situ measurements, providing key information to make crucial decisions regarding risks, or even mitigation, repairs or emergency response, as well as for a better understanding of the on-going instability phenomena affecting the dikes and dams. [ABSTRACT FROM AUTHOR]

Due to dissolution, weathering and erosion, limestone and marble form karstic landscape with precipitous hills, rugged valleys, caves and sinkholes. In the event of an intrusion, the magma, which resides below the limestone bedrock will ascend toward the earth's surface and fill up the fractures within the pre-existing rocks, forming dikes and sills. Dikes and veins can also be formed when minerals precipitate from hydrothermal fluids within a fracture. The objective of this study was to determine the texture and mineralogy of the dikes cutting the marble in the study area. The findings suggest that the mineral composition and physical structure of the dikes differ from the marble host rock based on its mineral, chemical and physical properties. Three samples were collected and analyzed using Scanning Electron Microscopy (SEM), X-ray diffraction analysis (XRD) and petrographic microscope. The results show that there are at least two types of dike, which are quartz and a coarse-grained granite dike at the study area. The presence of these dikes may affect the chemical and mechanical properties of aggregates produced from the quarry, and in turn affect the excavated rocks of its usage. [ABSTRACT FROM AUTHOR]

The delegation of management of aquatic environments and flood prevention to public inter-municipal cooperation establishments to January 1, 2018 resulted in a deep recomposition of the system of actors in charge of the dikes, and a questioning of coastal dike management policies. On the Normandy coast, a series of semi-structured interviews with institutional actors, associations and users was conducted between 2018 and 2021. This investigation highlights, on the one hand, a multiplicity of uncoordinated former managers and, on the other hand, a relative abandonment of several protective dikes that calls into question their very future. In view of the uncertainties linked to the transfer of competencies, the vulnerability of these mostly agricultural territories, the concerns of all actors towards the risk of submersion and salinization, several contrasting orientations are proposed by the institutional actors or by former managers. These proposals range from hard defense (strengthening of dikes) to softer management (partial depolderization, retreat of dikes).

The establishment of the Bulgarian Khanate along the Lower Danube River and the Northern Black Sea coast changed the geo-political situation in the early medieval Southeastern Europe. It is beyond doubt that the Bulgarians did not develop navy or commercial fleets at that time. However, one cannot reveal substantial reserves about the statement that Khan Asparukh’ descendants were not completely disadvantaged by their Black Sea coastline that they managed to keep under control due to political and military reasons. This becomes clear if the prolonged series of clashes between Byzantium and Bulgaria in 750s–770s are taken into consideration. Despite an obvious usefulness of the cooperation between land armies and navy squadrons in those endeavors, as well as the nonchallenged Byzantine maritime supremacy along the Black Sea shores, the Imperial navy met substantial difficulties or did not completely accomplish its tasks on many occasions.

The flood protection embankments of Hungary and Europe face numerous challenges. Some dike bases were constructed more than 200 years ago; since then, they have been elevated and extended. Because of these iterative adaptations, the dikes bear many construction errors, which can trigger failures and slides. Due to climate change, droughts and low-water periods of the rivers in central Europe are becoming more frequent. As a result of these effects, the water balance of the dikes can alter and desiccate in the long term. The most staggering fissures appeared on dikes built from clays susceptible to volume change. The General Directorate of Water Management ordered a comprehensive survey of dike pavement cracks in Hungary. This was one of the most extensive surveys of such kind. Hungary has some 4400 km of primary flood protection embankments, out of which 1250 km is paved. There are multiple reasons why the pavement of an embankment can crack. The main features of crack patterns related to clays with shrink-swell potential are identified. The results of international studies and the present survey are synthesised. The main objective of this paper is to draw a correlation between drought (aridity) zones, plasticity index of the soil samples, and crack thickness. [ABSTRACT FROM AUTHOR]

Xiangshan volcanic-related uranium ore field, as the historic largest uranium producer in China, is characterized by a large volcanic-intrusive complex and a number of uranium deposits. In most of the deposits, various types of dikes are spatially associated with the uranium ore bodies, although there have been no systematic attempts to integrate the geochronology and petrogenesis of these dykes and their link with uranium mineralization. In this study, whole-rock major and trace elements, zircon U–Pb dating and zircon Hf–O isotopic analysis were carried out on the Xiagnshan felsic-intermediate dikes, including granitic porphyry, quartz monzonitic porphyry and dioritic porphyry. These felsic-intermediate dikes have the similar geochemical characteristics with the major ore-hosting volcanic rocks, such as enrichment in large lithophile elements (i.e., Rb and Th) and some high-field strength elements (i.e., Zr, Y), but relative depletion in Sr, Ba, P and Ti. These dikes also exhibit zircon εHf(t) values concentrating from -9 to -4 and zircon δ18O values ranging from 7.6 to 10.0 ‰. Geochemical and isotopic data suggest that these dikes were predominantly derived from partial melting of crustal materials and possibly mingled with different proportions of mantle-derived materials during the formation of melts. SIMS and SHRIMP U–Pb dating of zircon grains from these felsic-intermediate dikes yield high-precision ages ranging from 136 to 131 Ma. Combined with previously reported age data indicates a rapid and concentrated dike emplacement event, although a few mafic-felsic dikes were sporadically emplaced at 126 -122 Ma. Such a relatively concentrated dike emplacement in the Early Cretaceous were most likely caused by the back-arc extension or intra-arc rift due to progressive rollback of the Paleo-Pacific Plate. Previous metallogenetic studies supported that the late-stage dikes at Xiangshan were temporally and spatially closely related to uranium mineralization. However, our new geochronological data and field observations indicate that the two episodes of uranium mineralization were not synchronous with the majority of dikes intrusions, indicating that they probably have no direct relationship in origin and that spatial coexistence were more likely due to multistage activities of faults. Rather, these dikes might act as a relatively reduced environment, and thus could facilitate the precipitation of uranium. In addition, all of these dikes can be considered favorable prospecting indicators in the Xiangshan ore field. [ABSTRACT FROM AUTHOR]

Predicting piping failure is essential for assessing dike and dam safety. To improve the current description of internal erosion, we sought to evaluate the effects of laminar and turbulent flow on the transport of particles, which is lacking in existing assessment manuals. These insights are necessary to develop engineering tools to predict piping caused by seepage-induced backward erosion in loose sediment inside or below the dike or dam body. Particle transport occurs when there is an imbalance between the wall shear stress of the water in the pipe and the critical wall shear stress of the material. Here, we focus on pipe erosion beneath clayey dikes and impermeable dams, where piping is governed solely by the flow resistance in the pipes. We describe pipe properties, flow characteristics and turbulence intensities in relation to existing hypotheses from the literature. [ABSTRACT FROM AUTHOR]

China has arguably the longest continuous tradition of writing on water control, but many of the oldest texts were produced by the central government and discuss only the largest water control projects. In recent decades, archaeologists have excavated several caches of documents written on wood and bamboo that contain important new evidence on the management of water systems that were not mentioned in traditional historical texts, including river dikes and irrigation reservoirs. Legal texts make clear that managing local water systems was a regular government responsibility across the Qin and Han empires. Two groups of documents have been discovered that were produced by officials surveying ruined water infrastructure to evaluate the labor that would be needed to repair them. Overall these documents make clear that the early Chinese empires had a sophisticated administrative system to maintain a highly anthropogenic network of waterways for the benefit of agricultural society. [ABSTRACT FROM AUTHOR]

The spatial distribution of wave overtopping water behind dikes is a key parameter for assessing the safety zone behind dikes in coastal areas, and it is essential for the safety of pedestrians behind dikes and the placement of critical infrastructure. A 2D OpenFOAM numerical model is validated using experimental data for predicting overtopping discharges and the spatial distribution of wave overtopping water behind a dike. The influences of slope angle, berm, landward ground level, relative structure freeboard, and product of incident wave height and wavelength are studied using a validated numerical model. Numerical model outcomes indicate that the lower slope angle has a critical value that is to be determined by the breaker parameter. Tests were conducted for a range of breaker parameters, including structure freeboard, and empirical-based predictive equations were derived for overtopping events under different wave conditions. We also found that the extent of the hazard area due to wave overtopping is significantly reduced when the landward ground level is negative. The findings of this study provide data and predictive formulas for assessments of the hazard zones behind the dikes and indicate the capability of numerical models in the design and safety assessment of dikes. • Investigated the 2D OpenFOAM model's ability to predict wave overtopping discharges and spatial distribution. • Investigate trends in the spatial distribution of overtopping waters on various parameters. • New prediction formulas are proposed for evaluating the spatial distribution of overtopping. [ABSTRACT FROM AUTHOR]

The results of petromagnetic and paleomagnetic studies of rocks from mafic dykes of the Sergeevka Terrane that intruded the basement rocks and are widespread in coastal outcrops of the eastern part of Peter the Great Bay of the Sea of Japan between the Anna and Priboinaya bays in the southern part of Primorskii krai are reported. The structural information allows us to conclude that dykes of both the eastern (Srednyaya Bay–Priboinaya Bay) and western (Anna Bay–Cape De Livron) clusters intruded from the igneous feeding channels of the same orientation. Rocks of the dykes were subjected to significant secondary alterations. Inverse magnetic fabric in the dykes is due to high-temperature decomposition and granulation of primary titanomagnetites upon postmagmatic deformations and metamorphism, traces of which are clearly visible in the microscopic and microprobe study of secondary alteration products. This provides evidence for a significant secondary change in rocks of the dykes after their intrusion. This is the secondary heating of the dykes above the temperature of 600°C, i.e., above the Curie point of magnetite (578°C). The nature of the isolated high-temperature NRM component of the dykes is not primary, but secondary, that is, metachronous. The paleomagnetic data constrained the time of the metamorphic event leading to the remagnetization of mafic dykes of the Sergeevka Terrane to about 250 Ma. The calculated paleolatitude of the Sergeevka Terrane at the time of acquisition of the metachronous NRM component by mafic dykes (21.8° ± 4.2° N) is consistent with the paleolatitudes of the northeastern edge of the North China Craton at the Late Permian/Early Triassic boundary. [ABSTRACT FROM AUTHOR]

The Dutch regional water authorities face an enormous task: the strengthening of about 1500 km of dikes and 500 civil-engineering structures before 2050. This immense operation is being funded, prioritised and supported by the Dutch Flood Protection Programme (DFPP), an alliance of regional water authorities and the Ministry of Infrastructure and Water Management. The work will be executed in nearly 300 projects located throughout the country on the coast, lakes and major rivers. To complete this task on time and within budget, innovation (a better insight into the behaviour of flood defences, new techniques and processes) is believed to be the way forward. In this paper, we look at how the DFPP has encouraged innovations between 2012 and the present. We stress the importance of using a sender–receiver approach to further knowledge transfer and uptake, and we describe how, by using an action research approach, the Dutch Flood Protection Programme is currently adapting its innovation strategy on the basis of lessons learned to improve knowledge uptake. We will address some of the innovations that have been developed over the years and how monitoring knowledge uptake helps to further improve the learning-by-doing approach. [ABSTRACT FROM AUTHOR]

Purpose: to determine the erosion control efficiency and action time of the bioengineering complex, represented by a flow regulating forest belt in combination with the simplest hydraulic structures. Materials and methods. The studies were carried out on the eroded slope soils in the south of the European territory of Russia with a system of soil protection measures represented by forest plantations, agricultural practices and the simplest hydraulic structures. The methods generally accepted in land and forest reclamation, erosion studies and agriculture were used. Results. According to long-term observations (1978–2018), high erosion-preventing efficiency of dike-ditches in combination with forest belts was found. The flow-regulating role of the dike-ditches and their duration will depend on their location in the forest belt and the presence of soil-protective agrotechnical measures at the catchment, which should be represented by the contour-strip placement of agricultural crops and agricultural backgrounds, special agrotechnical techniques: on the fall with micro limans, dimples, intermittent furrows, on crops of winter crops and perennial grasses by soil slitting and moling. It ensures the snowmelt runoff retention with a layer of 50–60 mm and regulates soil loss to the controlled values (0.3–1.0 t per ha per year). The removal of the contour-strip placement of crops and agricultural backgrounds, special agricultural techniques from the soil-protection system noticeably reduces the erosion-control effectiveness of the bioengineering complex. Conclusions. The erosion control efficiency of the complex under consideration increases with the growth and development of trees: bulk density decreases to 1.05–1.15 grams per cubic centimeter, the number of water-resistant units increases to 55–75 %, the permeability to 4–6 mm per min. The forest belt accumulates a significant part of the solid runoff, protecting the dikes-ditches from siltation, increasing the duration of their action. The most efficient placement of dikes-ditches is in the last row spacing of the forest belt.

Research subject. The Koytash ore field is located in the potentially productive Au, Ag, W, Mo, Ti, Fe, Cu, Pb, Zn and REE North Nuratau mineralisation zone of Tien Shan. The authors undertook a study of the composition of dikes breaking through the Paleozoic ore-bearing formations, as well as their petro- and ore-generating role in the formation of the Koytash-Ugat sulphide-rare-metal (W, Mo, Fe) specialised mineralisation. Materials and methods. A study of rock and mineral composition was performed at the Institute of Geology and Geophysics named after Kh.M. Abdullaev. The content of petrogenic and rare elements in rocks and sulphides was determined by ICP-MS using an ICPE-9000 mass-spec trometer in the Central Laboratory of the State Committee for Geology of the Republic of Uzbekistan. The chemical analysis of minerals was performed using a Jeol-8800Rh electronic microanalyser at the Institute of Geology and Geophysics named after Kh.M. Abdullaev. The micrographs of transparent sections were obtained using Nikon Optiphot 2 Pol and Polam R-311 microscopes. Results and conclusions. The conducted study showed that, in terms of their structure, the Koytash ore field dike formations can be regarded as lamprophyres. In terms of their chemical composition, these formations are mafic and intermediate rocks of the subalkaline series. It was found that the composition of lamprophyre dikes correlates with the size of the erosion section. Their melanocratic varieties are confined to the southern part of the intrusion (absolute elevations are 1000–1200 m), and leucocratic – to the northern (about 1900 m). This is assumed to be the result of crystallization differentiation of a single initial melt. The dikes of the Koytash ore field lamprophyres break through not only sulphide-rare-metal bodies of the Koytash-Ugat strip, but also skarn and carbonate rocks and, in turn, are broken through by quartz-polymetallic ore-bearing veins, which testifies to their inter-ore character.

The article is devoted to the design substantiation of a new type of drainage structures based on fibrous materials for ground dams. To assess the effectiveness of the application, two-dimensional modeling of hydraulic processes using the software environment Plaxis 2D AE 2013 finite-element method of a ground dam was carried out. Experimental research has become the basis study the effect of the rock mass on the filtration flow of water passing through the drainage from fibrous polymeric materials. Method of valuation suggested in article of the height of the layer and the slope of drainage from fibrous materials take into account the experimental data obtained for ground dams.

Changbai Mountains intraplate volcanism (NE China) developed above the 500 km deep stagnant portion of the Pacific slab in the last 20 Ma. The more recent activity includes a shield-forming stage (2.8–0.3 Ma), the Tianchi cone construction stage (1.5–0.01 Ma), and a caldera-forming stage (0.2 Ma-present). Detailed studies on the petrogenesis of the volcanic products between the first two stages and the possible role of geodynamics and local tectonics in controlling the volcanism, however, are lacking. Here, we present structural and whole-rock geochemical and zircon Hf isotopic data on Pleistocene dikes of the Changbai Mountains at the transition from the shield-forming to the Tianchi stage with the aim to constrain their age and the source(s) of their parental magma. The dikes represent the shallower feeding system of monogenetic cones and have a NW-SE strike, which is also the preferred strike of the major fault affecting the area and along which the Changbai Mountains monogenetic scoria cones align. The dikes have a potassic affinity and a trachybasaltic composition. Their zircon U–Pb age is 1.19–1.20 Ma (Calabrian). The trachybasalts are enriched in Rb, Ba, Th, U, Nb, Ta, K, Pb, and LREE and slightly depleted in Sr, Zr, Hf, Ti, and HREE with a weak negative Eu/Eu* (δEu = 0.96–0.97). Trace elements and isotopic compositions are compatible with an OIB-type source with an EMI signature. The calculated (87Sr/86Sr)i (=0.705165–0.705324), (143Nd/144Nd)i (= 0.512552–0.512607, εNd(t) = −0.58 to −1.65), and Hf model ages (TDM2) of 1768–1562 Ma suggest that the trachybasaltic dikes were contaminated by a Mesoproterozoic, relatively basic lower crust. The source of the Calabrian trachybasalts consists of asthenospheric melts modified by a subcontinental lithospheric mantle. These melts upwell from depth and stop at the crust-mantle interface where underplating processes favor the assimilation of ancient lower crust material. During the ascent to the surface along deep-seated crustal discontinuities, these magmas weakly differentiate.

Abstract The net tectonic rotation method is an alternative to paleomagnetic tilt corrections. The method was originally developed for sedimentary rocks and lavas, which have paleohorizontal indicators, but was later adapted for dikes by assuming that dikes intrude vertically. We conduct multiple numerical experiments that demonstrate geometric flaws in the net tectonic rotation method if dikes are not quite vertical prior to deformation. These flaws can impact the interpretations from the method, but the size of the impact depends on the original dike strike, dike dip, and the paleomagnetic reference direction. Our experiments show the worst behavior occurs for dikes that are approximately perpendicular to the reference declination. In addition, the results for dipping dikes of all initial strikes become increasingly distorted as the reference direction's inclination increases. Using data from two field areas in Cyprus and northern Iceland, we compare the application of net tectonic rotation to alternative techniques—relative comparisons and spatial regressions—that do not require an assumption of initially vertical dikes. We conclude with a list of questions that workers should answer prior to future application of net tectonic rotation to dikes.

Abstract In order to investigate the role of dikes in the volcanic evolution and the triggering mechanisms of catastrophic mass wasting volcanoes, we have sampled for a pilot study, seven dikes within the Wai’anae volcano, Oahu, Hawaii. The width of the dikes ranged between 0.4 and 2.5 m. This work focuses on the characterization of the magma flow directions using anisotropy of magnetic susceptibility (AMS) data in dikes of the inner part of the Wai’anae volcano. This part is now exposed, because this volcano experienced destabilization and flank collapse. Rock magnetism data show composite magnetic mineralogy, corresponding when plotted on the Day diagram to be dominated by single domain (SD) and pseudo-single domain particles of pure titanomagnetite, suggesting possible inverse magnetic fabric associated with the SD grains. The obtained magnetic fabric does not reflect such grain sizes and is probably partly related to the presence of different magnetic phases, resulting in part of our samples as having “abnormal” fabrics. We therefore used a simple criterion to eliminate most of the abnormal fabrics in order to analyze the magnetic fabric data in a clearer way. After rejection of most of the abnormal data, the determination of the magnetic zone axis, which underlines the effect of imbrication in dike margins, yielded reliable magma flow directions in most of the studied dikes, with a predominance of vertical to subvertical AMS directions. The inferred dominantly vertical to subvertical magma flow of dikes (feeding from below) within the most internal parts of the volcano, suggests a process of accumulation of new magma at different levels within the inner part of the edifice. This process was enhanced by subhorizontal magma flow toward the volcano center in two other dikes. Such accumulation helps to explain the inflation, subsequent destabilization, and flank collapse of the Wai’anae volcano.

We analyze and generalize new data inferred from the geological, geochronological, and metallogenic studies performed in recent decades on igneous rocks of the Iorokhan gold-bearing complex in the eastern Bureya Massif. It is shown that four phases are determinative of the structure of the Iorokhan complex of minor intrusions whose rocks are referred to hypabyssal and subvolcanic intrusive facies. Specific features of their rock composition and structural tectonic conditions of localization are described and geological and geochronological (103 ± 1.0-97.4 ± 6.5 Ma) data on their Late Albian–Early Cenomanian age are presented. Based on the alumina, calcium, and alkali ratio, the major part of their compositions corresponds to the I-type (A/CNK < 1.1) high-alumina magnesia and magnesia–ferruginous varieties with decreased HFSE concentrations, including HREE. Melts formed due to amphibolite source melting might have been the deep sources of the Iorokhan diorites. The Noni deposit is briefly described and the main localization factors of the gold-ore mineralization are considered. The Iorokhan magmatite areals of the East Bureya Volcano–Plutonic Zone may be considered as one of the fragments of the structure bordering between the continental margin of the Bureya Massif and the accretionary prisms of the Sikhote Alin Orogenic Belt. The Iorokhan complex of minor intrusions is assumed to be a small fragment of an extensive band of Late Albian–Early Cenomanian magmatites developed in southern Far East Russia that originated under the transform continental marginal setting, and a combination of synstrike–slip compression and extension zones typical of such margins with further development of the pull-apart depressions. [ABSTRACT FROM AUTHOR]

The net tectonic rotation method is an alternative to paleomagnetic tilt corrections. The method was originally developed for sedimentary rocks and lavas, which have paleohorizontal indicators, but was later adapted for dikes by assuming that dikes intrude vertically. We conduct multiple numerical experiments that demonstrate geometric flaws in the net tectonic rotation method if dikes are not quite vertical prior to deformation. These flaws can impact the interpretations from the method, but the size of the impact depends on the original dike strike, dike dip, and the paleomagnetic reference direction. Our experiments show the worst behavior occurs for dikes that are approximately perpendicular to the reference declination. In addition, the results for dipping dikes of all initial strikes become increasingly distorted as the reference direction's inclination increases. Using data from two field areas in Cyprus and northern Iceland, we compare the application of net tectonic rotation to alternative techniques—relative comparisons and spatial regressions—that do not require an assumption of initially vertical dikes. We conclude with a list of questions that workers should answer prior to future application of net tectonic rotation to dikes. Plain Language Summary: A dike is a tabular intrusion of volcanic rock. It may record the direction of Earth's magnetic field at the time of the dike's formation, and it may subsequently rotate due to tectonic processes. By analyzing the magnetic content of a dike, a geologist can therefore acquire information about Earth's tectonic history. Net tectonic rotation is a particular technique for acquiring such information. It assumes that dikes are vertical at the time of their intrusion. We perform experiments that show that if dikes are not quite vertical, the inferences from this technique will be flawed. The flaws are not systematic and in some cases can lead to egregious errors in the interpretations. We show some alternatives to this approach using real data from Cyprus and northern Iceland. We also list a series of questions for workers to consider if they wish to use this method in the future. Key points: The net tectonic rotation method has been used to predict initial dike strikes from paleomagnetic dataThe method assumes that dikes are initially vertical and can return the correct dike strike in these casesNumerical experiments show the method returns biased answers for dipping dikes that may impact geologic interpretations [ABSTRACT FROM AUTHOR]

The results of geochemical studies of Paleoproterozoic volcanic rocks in the structure of the Polmak–Pechenga–Imandra–Varzuga belt of the northeastern part of the Fennoscandian Shield are presented. Taking into account new geochronological data, the volcanic series are correlated with subvolcanic and intrusive rocks of the Murmansk and Kola–Norwegian terranes. The comparative analysis of sections of volcanic rocks of the Imandra–Varzuga and Pechenga structures indicate asynchronous evolution of these fragments of the belt in a range of 2.51–2.40 Ga and a significant time gap (probably, >300 m.y.) in evolution of both the Imandra–Varzuga and Pechenga structures. The geochemical evidence is provided for the cyclic plume-lithospheric interaction during magmatism of the Sumian–Sariolian period, which shows that basic melts mostly generated from facies of spinel lherzolites exhibit features of significant crustal contamination as a result of their interaction with rocks of the Archean basement. [ABSTRACT FROM AUTHOR]

Anisotropy of Magnetic Susceptibility (AMS) is a valid tool to investigate magma flow direction within dikes. However, geometrically inverse magnetic fabric characterized by maximum magnetic susceptibility axis (kmax) perpendicular to the dike wall may complicate the interpretation of flow trajectories. To better understand the nature of this fabric, we present a multiscale study on 19 dikes (383 samples) in the Miocene Alftafjordur volcanic system (Iceland), where 80% of the samples show a geometrically inverse magnetic fabric. We carried out (1) AMS measurements at different magnetic fields and temperatures, along with Anisotropy of Anhysteretic Remanent Magnetization (AARM) analysis; (2) hysteresis loops and FORC diagrams; (3) thin section analysis; (4) structural fieldwork. A variable Ti‐content (0.1 < x < 0.6, Fe3‐xTixO4) titanomagnetite is the main magnetic carrier, and the contribution of the paramagnetic elongated crystals to the magnetic fabric is negligible. Single domain is not the prevailing domain state of the magnetic particles, suggesting that its occurrence cannot be the main cause for the inverse fabric. AMS analysis at different fields and temperatures along with AARM allow us to exclude any mineral phase change of the titanomagnetite across the dike. Nevertheless, kmax is parallel to a diffuse horizontal column‐like fracture pattern perpendicularly oriented with respect to the dike strike. This suggests that the Ti‐magnetite mineral orientation during dike cooling was affected by the fracture network progressively developing columnar basalts. This study demonstrates that the interpretation of AMS data on old and deep volcanic bodies is not straightforward and observations at different scales are required. Key Points: Our analyses about the magnetic fabric of the Alftafjordur dike swarm revealed that most of the samples show an inverse magnetic fabricThe origin of the inverse magnetic fabric is associated with the development of horizontal fractures during the cooling stage of dikesIt is not straightforward to infer the magma flow direction on deep and old exhumed dikes by using standard low‐field AMS measurements only [ABSTRACT FROM AUTHOR]

The paper presents data on dolerite dikes in the Murmansk block in the northeastern Kola Peninsula. The dikes belong to a Middle Paleozoic flood-basalt association, which is a principal element of the large-scale plume–lithospheric process in the area of the Barents Sea. According to their geological, petrological, and geochemical features, the dolerite dikes are classified into two groups: older and younger, which pertain to the initial and final evolution of the large igneous province produced under the effect of the Barents Sea plume at 450–340 Ma. One of the results of the plume–lithosphere interaction was the origin of the Eastern Barents Basin, which is filled with large volumes of basalts, and this predetermined the further subsidence of the area in Meso-Cenozoic time and the accumulation of thick sedimentary sequences with significant hydrocarbon resources. The peripheries of the area with products of basaltic magmatism are marked by alkaline rock complexes. The largest of the latter are the intrusions of the Kola Province and kimberlites in Archangelsk oblast. The dolerites of the dikes abound in xenogenic grains of zircon, which were dated at 2.7, 1.8, 1.3, 0.7 Ga. These age values suggest that the parental melts may have been derived in the lower crust and that the magma-generating processes may have evolved in the root zone of an ancient rift system. [ABSTRACT FROM AUTHOR]

As a result of still more flood events in Denmark in the last few years, flood protection has received growing attention in many local communities. By law, in Denmark, protecting your property from flooding from the sea is a private responsibility. This obliges communities to debate their own flood risk and their ability and options to fund additional protection. However, creating and maintaining flood protection are challenging. The related negotiations frequently develop into conflicts, which prolong the processes. This research concludes that the main challenges are not the technical issues, but the planning and negotiation between different interests. The paper presents the results of four qualitative case studies of existing dikes and dike projects in Denmark. By applying a situated analysis, the controversies in each case have been unravelled, with the aim of understanding the deeper reasons behind them. The paper concludes that the controversies often revolve around broader issues in the local communities such as liveability and population decline, but also feed on less visible aspects to do with people's long- and short-term experience of living and moving around in their local landscape. The results of the paper underline the need to move beyond risk assessments and meteorological calculations when flood risk protection projects are planned and managed. Other issues have to be included if conflicts are to be minimised and better solutions found. [ABSTRACT FROM AUTHOR]

Abstract—Granitoids and dikes of Svyatoy Nos pluton of Cape Svyatoy Nos in the northwestern part of Verkhoyansk-Kolyma folded area, cutting terrigenous and volcanogenic-sedimentary rocks of Upper Jurassic–Lower Cretaceous, are considered. Obtained U‒Pb SIMS geochronological data on zircons from granitoids and dike rocks indicate, that their crystallization ages correspond to Aptian‒Albian (119–111 Ma). Petrography and geochemical affinitites of rocks allow to refer granitoids and felsic dikes to I-type granites. Similarity in chemical composition with coeval granitoids of Great Lyakhovsky Island, the most northern member of Chokhchuro‒Chokurdakhsky submeridional belt of granitoids and Aptian‒Albian granitoids of sublatitudinal belt of Anyui‒Chukotka fold belt is shown. Earlier it was established by many authors, that intrusion of Aptian-Albian granitoids and dikes (117–105 Ma) on the Arctic margin of Chukotka and in the northwestern part of Verkhoyansk‒Kolyma folded area occurred during extension. Aptian‒Albian age, post-shortening character of intrusion and similarity of Svyatoy Nos granitoids in chemical composition with mentioned above Aptian-Albian granitoids allow to refer them to a single stage of postcollisional extension. [ABSTRACT FROM AUTHOR]

Seven three‐component ocean bottom seismometers (OBS) of the Ocean Observatories Initiative (OOI) Cabled Array on top of Axial Seamount are continuously streaming data in real time to the Incorporated Research Institutions for Seismology (IRIS). The OBS array records earthquakes from the submarine volcano which last erupted on 24 April 2015, about 4 months after the array came online. The OBS data have proven crucial in providing insight into the volcano structure and dynamics (Wilcock et al., 2016, https://doi.org/10.1126/science.aah5563). We implemented a real‐time double‐difference (RT‐DD) monitoring system that automatically computes high‐precision (tens of meters) locations of new earthquakes. The system's underlying double‐difference base catalog includes nearly 100,000 earthquakes and was computed using kurtosis phase onset picks, cross‐correlation phase delay times, and 3‐D P and S velocity models to predict the data. The relocations reveal the fine‐scale structures of long‐lived, narrow (<200 m wide), outward dipping, convex faults on the east and west walls of the caldera that appear to form a figure 8‐shaped ring fault system. These faults accommodate stresses caused by the inflation of magma prior to and deflation during eruptions. The east fault is segmented and pulled apart in east‐west direction due to its interaction with the Juan de Fuca Ridge, which at this location forms an overlapping spreading center. The RT‐DD system enables the monitoring and rapid analysis of variations in fine‐scale seismic and fault properties and has the potential to improve prediction of timing and location of the next Axial eruption expected to occur in the 2022–2023 time frame. Key Points: Real‐time double‐difference (RT‐DD) system enables precision monitoring of seismicity at Axial Seamount using the OOI cabled OBS arrayPrecise event locations reveal structure and evolution of a mature, outward dipping, convex ring fault system in the shape of a figure 8The faults express the complex interaction between volcanic processes at Axial Seamount and sea floor spreading at the Juan der Fuca Ridge [ABSTRACT FROM AUTHOR]

Initial damage, caused by previous wave loading or other events, might affect the hydraulic stability of pattern-placed revetments. Three common types of damage are considered in this study. The effect of this assumed initial damage on the hydraulic stability and failure probability of revetments is quantified using a FEM model. This model is developed using data from large-scale flume and field experiments. Using results from the FEM model, surrogate models are created to predict the effect of each type of initial damage on the hydraulic stability and failure probability. Through the use of these surrogate models, it is demonstrated that S-shaped deformation caused by filter migration around the wave impact zone has the largest effect on the hydraulic stability decreasing up to 30%, and failure probability per year increasing up to 10,000 times. When the granular filling between the joints of the columns is washed-out, the stability decreases up to 29% and the failure probability increases up to 700 times. A missing column has a limited effect on the hydraulic stability and failure probability when there is no other (structural) damage. However, if it originates from underlying damage, it might be an initial sign of total failure of the revetment. This study demonstrates the effectiveness of finite element modeling for studying (damaged) revetments, which can be used to complement flume experiments. The results can be used to prioritize maintenance efforts in risk-based maintenance of pattern-placed revetments. • The effect of damage on the performance of a pattern-placed revetment is studied. • Finite element modeling is used to develop a model to study three types of damage. • Even a small deformation can cause a significant decrease in hydraulic stability. • Washed-out joint filling affects hydraulic stability in particular when most is lost. • The root cause of a missing column is vital for its effect on hydraulic stability. [ABSTRACT FROM AUTHOR]

The results of investigations for the large structural Surozh and Near-Azovian megablock of the Ukrainian Shield are presented. The features of fault-block tectonics and its influence on forming the ore knot are defined. The other fault zones of the orthogonal and diagonal systems and their significance in the localization of unique fluorite rare-earth deposit are characterized, by using satellite images and geological-geophysical data. The features of magmatism manifestation are studied.

The comprehensive geochemical and isotopic-geochronological study of Early Proterozoic volcanic rocks in structure of the Polmak–Pechenga–Imandra–Varzuga belt and dikes and sills of the Murmansk and Kola–Norwegian terranes is conducted. Abundant swarms of mafic dikes (2.06–1.86 Ga) are established in the northwestern frame of the belt, including swarms of metadolerites (2060 ± 6 Ma), ferropicrites and gabbronorites (1983 ± 5 Ma), and poikilophitic dolerites (1860 ± 4 Ma). The comparison of volcanic rocks of the Pechenga and Imandra–Varzuga structures shows asynchronous change in volcanism style, with a significant time lapse. The geochemical features of volcanic rocks of the Tominga Formation are typical of those of continental magmatism and can hardly be correlated with those of the Pilguyarvi Formation. According to isotopic-geochronological data, depleted mantle melts in the Pechenga and Imandra–Varzuga zones intruded at 2010–1970 and 1970–1980 Ma, respectively. The analysis of the conditions of formation of volcanic series shows that Neoarchean lithospheric mantle, which produced melts with low Zr/Nb ratios, was a source for primary melts of the Kuetsjarvi Formation of the Pechenga structure and their homologs of the Imandra–Varzuga structure. In contrast, the volcanic rocks of the Kolasjoki Formation, which were weakly contaminated with crustal material, and the related Ilmozero Formation, as well as the metadolerite dikes of the Kirkenes region, were sourced mostly from asthenosphere with separation of melt above the garnet stability depth. The formation of the volcanic rocks of the Pilguyarvi Formation is related, judging from the geochemical data, to two asthenospheric sources different in depth, which produced tholeiitic and ferropicritic melts. [ABSTRACT FROM AUTHOR]

We report on a numerical experiment by which we investigated the propagation of an erosion pipe in a water saturated granular soil. The simulation was performed with a two-dimensional implementation of the coupling between the discrete element method and the lattice Boltzmann method. A synopsis of the numerical scheme is provided. The specimen and testing conditions were designed as representative of the pipe front region. The kinematics of mobilisation and fluidisation of the granular mass were investigated based on the physically-motivated definition of particle velocity thresholds. We measured a constant mass erosion rate, up to a clogging event. The study includes a micromechanical analysis of the response of the granular skeleton. We emphasise the influence of the unloading-induced damage on the erosion path, and the relevance of force chain arching as a self-organised resistance mechanism. [ABSTRACT FROM AUTHOR]

Backward erosion piping involves the gradual removal of granular material under the action of water flow from the foundation of a dam or levee, whereby shallow pipes are formed that grow in the direction opposite to the flow. This pipe-forming process can ultimately lead to failure of a water-retaining structure and is considered one of the most important failure mechanisms for dikes and levees in the Netherlands and the United States. Modeling of this mechanism requires the assessment of hydraulic conditions in the pipe, which are controlled by the particle equilibrium at the pipe wall. Since the pipe׳s dimensions are controlled by the inflow to the pipe from the porous medium, the flow through the pipe is thought to be laminar for fine- to medium-grained sands. The literature provides data for incipient motion in laminar flow, which is reviewed here and complemented with data from backward erosion experiments. The experiments illustrate the applicability of the laminar incipient motion data to determine the erosion pipe dimensions and corresponding pipe hydraulics for fine- to medium-grained sands, for the purpose of backward erosion piping modeling. [ABSTRACT FROM AUTHOR]

Mixed‐mode fluid‐filled cracks represent a common means of fluid transport within the Earth's crust. They often show complex propagation paths which may be due to interaction with crustal heterogeneities or heterogeneous crustal stress. Previous experimental and numerical studies focus on the interplay between fluid overpressure and external stress but neglect the effect of other crack parameters. In this study, we address the role of crack length on the propagation paths in the presence of an external heterogeneous stress field. We make use of numerical simulations of magmatic dike and hydrofracture propagation, carried out using a two‐dimensional boundary element model, and analogue experiments of air‐filled crack propagation into a transparent gelatin block. We use a 3‐D finite element model to compute the stress field acting within the gelatin block and perform a quantitative comparison between 2‐D numerical simulations and experiments. We show that, given the same ratio between external stress and fluid pressure, longer fluid‐filled cracks are less sensitive to the background stress, and we quantify this effect on fluid‐filled crack paths. Combining the magnitude of the external stress, the fluid pressure, and the crack length, we define a new parameter, which characterizes two end member scenarios for the propagation path of a fluid‐filled fracture. Our results have important implications for volcanological studies which aim to address the problem of complex trajectories of magmatic dikes (i.e., to forecast scenarios of new vents opening at volcanoes) but also have implications for studies that address the growth and propagation of natural and induced hydrofractures. Plain Language Summary: Fluids move within the Earth by means of different mechanisms. One of the most relevant mechanisms, particularly for magma transport within the lithosphere, is the propagation through fluid‐filled fractures: the fluid (or magma) can create its own path through the crustal rocks by fracturing them. If the density of the fluid is lower than the density of the rocks, the fluid would be pushed upward by buoyancy (similarly to a gas bubble in water). However, the propagation path followed by these fluid‐filled fractures may be complex. This may be due to several factors, including the forces (stresses) acting within the crust because of plate tectonic or because of remarkable topographic features. Here we make use of computer simulations and laboratory experiments to test how fluid‐filled fractures interact with such crustal stresses. We quantify how the competition between (i) crustal stresses, (ii) fluid (or magma) pressure, and (iii) the length of a fluid‐filled fracture may affect its direction of propagation. We define a critical range of values for a parameter which may help identifying the path of a fluid‐filled fracture propagating through the Earth crust. Our results may have important implications for volcanological studies which aim to forecast scenarios of new eruption locations. Key Points: We make use of analogue experiments and numerical simulations to study the propagation path of fluid‐filled cracks in interaction with crustal stressesWe show and quantify how the competition between crustal stresses, fluid pressure, and crack length affect the path of fluid‐filled cracksWe provide a critical range of values for a parameter which may help predicting the propagation path of a fluid‐filled crack [ABSTRACT FROM AUTHOR]

Based on geological classification of Iran, Oligocene Lakhshak pluton is situated in the Sistan suture zone that composed of siliciclastic and ophiolitic melanges. The Lakhshak pluton is a host of numerous northeast dikes intruded the siliciclastic sediments. The pluton is granodiorite, granite, diorite, quartz diorite in composition. The dikes occur along shear zones and show moderate to high deformations. Dikes are mainly diorite and granodiorite in composition and consist of plagioclase, biotite, hornblende and quartz. The deformation evidences are quartz microboudines, mica fish (especially in biotite), and fractures in minerals, inflation in quartz, asymmetric porphyroclasts, preferred orientation and rotation of minerals. These evidences show that the dikes suffered from brittle to ductile deformation. Dynamic recrystallization of quartz and feldspar grains is mainly similar as bulge type. Mylonitic structures in the dikes probably formed between 300 and 500°C. Oriented thin sections, three-dimensional block diagram and field studies show dextral shears in dikes. [ABSTRACT FROM AUTHOR]