Vein Geometry Research Articles

Influences of stenosis and transplantation on behavior of blood flow in the host and grafted vessels using computational fluid dynamics

In this research, the changes of wall shear stress (WSS) of flow blood affected by stenosis and grafted vessels are studied. For the simulation of non-Newtonian fluid, blood in this paper, the Carreau fluid model is used. The severity of the stenosis is considered to reduce the internal cross-sectional area of the host vessel by 30 %. In this paper, simulations are performed on the human body in sports, which are classified into anemia (LHD), normal (NHD) and high blood pressure (HHD). Results are presented in three sections including after stenosis region, transplantation section, and after transplantation region by calculating wall shear stress (WSS). It is reported that wall shear stress is increased after stenosis location due to immediate variation in the cross-section area when blood flows. To explain, Stenosis reduces the cross-section area of the vessel which causes flow contraction. Consequently, this phenomenon increases flow velocity in the central region of blood flow whereas, after passing from stenosis, blood flow is exposed to an abrupt expansion which causes flow back from the central region to wall vicinity in lateral regions of the vessel. Maximum amounts of wall shear stress are achieved at 280 Pa, 350 Pa, and 550 Pa for anemia, normal, and hypertensive individuals in order. However, the consequence of the mentioned phenomenon in hypertensive individuals is more severe than that of anemic ones. Therefore, the geometry of veins is very important in medical surgeries to prevent vessel failure, especially in stressful points of transplantation.

The Significance of Cross-Sectional Shape Accuracy and Non-Linear Elasticity on the Numerical Modelling of Cerebral Veins under Tensile Loading.

Traumatic brain injury (TBI) is a serious global health issue, leading to serious disabilities. One type of TBI is acute subdural haematoma (ASDH), which occurs when a bridging vein ruptures. Many numerical models of these structures, mainly based on the finite element method, have been developed. However, most rely on linear elasticity (without validation) and others on simplifications at the geometrical level. An example of the latter is the assumption of a regular cylinder with a constant radius, or the geometry of the vein acquired from medical images. Unfortunately, these do not replicate the real conditions of a mechanical tensile test. In this work, the main goal is to evaluate the influence of the vein's geometry in its mechanical behaviour under tensile loading, simulating the real conditions of experimental tests. The second goal is to implement a hyperelastic model of the bridging veins where it would be possible to observe its non-linear elastic behaviour. The results of the developed finite element models were compared to experimental data available in the literature and other models. It was possible to conclude that the geometry of the vein structure influences the tensile stress-strain curve, which means that flattened specimens should be modelled when validating constitutive models for bridging veins. Additionally, the implementation of hyperelastic material models has been verified, highlighting the potential application of the Marlow and reduced polynomial (of fourth and sixth orders) constitutive models.

Occlusion and catheter ablation using a large-size cryoballoon for various pulmonary veins: a case series

Abstract Background It is established that pulmonary vein isolation using the POLARx™ (Boston Scientific, Marlborough, MA, USA) cryoballoon is a rapid, safe, and effective approach. The new POLARx™ FIT (Boston Scientific), which is expandable from 28 to 31 mm in diameter, is currently available. However, there is limited evidence available regarding the treatment of atrial fibrillation in this setting. In this article, we report a case series of cryoballoon ablation in patients with atrial fibrillation using POLARx™ FIT. Case summary This case series describes a comparison of obstruction in three patients with pulmonary veins of different shapes and diameters undergoing cryoballoon ablation and pulmonary vein isolation with a 31 mm diameter balloon. Discussion Cryoballoon ablation using the 31 mm mode of POLARx™ FIT has the potential to provide safe and stable pulmonary vein isolation with good occlusion for a variety of pulmonary vein geometries. In this case series, the 31 mm mode of the POLARx™ FIT resulted in better pulmonary vein occlusion than the 28 mm mode in patients with large left atria and large pulmonary veins, including the left common pulmonary vein. This approach may be considered a first-line therapy option of cryoballoon ablation in patients with atrial fibrillation.

Veined Rock Performance under Uniaxial and Triaxial Compression Using Calibrated Finite Element Numerical Models

Geotechnical rockmass characterization is a key task for design of underground and open pit excavations. Hydrothermal veins influence excavation performance by contributing to stress-driven rockmass failure. This study investigates the effects of vein orientation and thickness on stiffness and peak strength of laboratory scale specimens under uniaxial and triaxial compression using finite element numerical experiments of sulfide veined mafic igneous complex (CMET) rocks from El Teniente mine, Chile. The initial numerical models are calibrated to and validated against physical laboratory test data using a multi-step calibration procedure, first of the unveined Lac du Bonnet granite to define the model configuration, and second of unveined and veined CMET. Once calibrated, the numerical experiment involves varying the vein geometry in the veined CMET models by orientation (5 to 85°) and thickness (1, 4, 8 mm). This approach enables systematic investigation of any vein geometry without limitations of physical specimen availability or complexity of physical materials. This methodology greatly improves the value of physical laboratory test data with a limited scope of vein characteristics by using calibrated numerical models to investigate the effects of any other vein geometry. In this study, vein orientation and thickness were both found to have a significant impact on the specimen stiffness and peak strength.

CARD20: Investigating the Impact of Ventriculoatrial Shunts on Venous Hydrodynamics: A Computational Fluid Dynamics Analysis

Ventriculoatrial (VA) shunts are a common treatment option for patients suffering from hydrocephalus and requiring cerebrospinal fluid (CSF) drainage. However, the impact of this treatment on cardiac hydrodynamics has yet to be fully understood. To shed light on this issue, the present study employs computational fluid dynamics (CFD) simulations to evaluate the effects of VA catheters on venous hydrodynamics in hydrocephalus patients. The study focuses on five models of different sections of veins, including the Internal Jugular Vein (IJV), Right and Left Brachiocephalic Veins (RBV-LBV), and the Superior Vena Cava (SVC). The vein geometry was reconstructed from neck CT scans of a patient with mild hydrocephaly without a catheter. Blood flow simulations were performed using pressure-based transient laminar models solved with the Ansys Fluent Navier-Stokes solver. The analysis was conducted on two healthy cases with and without catheters, and three hydrocephalus cases with catheters, considering mild, moderate, and severe hypertension. The results show that pressure accumulation near the IJV bulb was observed in all cases, with maximum pressure in the severe hypertension case. A pressure of 3,050 Pa was reached over the catheter insertion site. The healthy case without the shunt showed velocities of up to 0.8 m/s, while in the severe hypertension case, velocities were less than 0.2 m/s in similar regions for the IJV, RBV, and LBV. Healthy streamlines showed some vortices throughout the IJV, which seemed to be minimized by the presence of the catheter in the other models. In conclusion, this study provides valuable information regarding the hydrodynamic alterations seen in patients with VA shunts. The observed pressure accumulation and decreased velocity can be associated with potential adverse effects such as thrombotic formation. These findings can be used to guide future treatment options and warrant further long-term study. The use of CFD simulations offers a non-invasive and efficient method to study the effects of VA shunts on cardiac hydrodynamics and can provide a deeper understanding of the complex interplay between cerebrospinal fluid drainage and venous hydrodynamics.

Paleo‐Permeability Structure of the Crustal Section of the Samail Ophiolite Based on Automated Detection of Veins in X‐Ray CT Core Images From the Oman Drilling Project

AbstractTo assess the paleo‐permeability structure of oceanic crust, we used 3‐D X‐ray Computed Tomography (XCT) images to quantify the distribution and geometry of mineral veins in core samples from Oman Drilling Project Holes GT1A, GT2A, and GT3A, which correspond to the upper to lower crustal sections of the Samail ophiolite. We developed a new method that automatically detects veins in the XCT core images based on iterative adaption of the two‐step Hough transform combined with multiscale Hessian filtering for identifying an elongate structure. Application of the developed method allowed us to identify the geometry and Computed Tomography number of more than 1500 veins with millimeter‐scale apertures in core sections with a total length of ∼1,200 m. High‐CT (HCT) veins in the drilled cores can be related to relatively high‐temperature fluid circulation near the mid‐ocean ridge, whereas Low‐CT (LCT) veins can be related to subsequent low‐temperature fluid circulation. Applying fracture fluid‐flow models to the geometric information for the detected veins, we found that the HCT and LCT vein systems both yielded bulk permeability of 10−13–10−9 m2 for each hole. This indicates that millimeter‐wide fractures can control crustal‐scale permeability, even in the lower oceanic crust. However, these vein systems show different depth dependencies and anisotropies of permeability, possibly reflecting the different spatial variations of high‐ and low‐temperature fluid circulation in oceanic crust.

Bionic Mechanical Analysis of Dragonfly Wings: The Feasibility of Mesh Combination to Improve Structural Stiffness

The nodes of the object will show different degrees of deformation and displacement or even damage over time. The mesh structure is flexible and different mesh shapes and arrangements will affect the structural stiffness of the object. The unique structure of dragonfly wing veins allows the dragonfly to withstand pressures several times higher than itself and to fly freely. This study is based on dragonfly wing bionics to disassemble the structure of dragonfly wing vein geometry. And it aims to investigate the deflection under different geometries and three-dimensional spatial structures by using the drawing software Auto CAD to draw dragonfly sample graphics, the finite element software Hyper mesh to build the model and the solver OptiStruct to analyze the structure of wrinkling, arching deflection, z-direction maximum displacement, y-direction maximum rotation angle, combined displacement test under the different loads. The results show that: (1) The dragonfly wing vein mesh structure can enhance the stiffness under load. (2) In contrast, the displacement deformation of quadrilateral and combined hexagonal is smaller. (3) The structural stiffness of quadrilateral hexagon is enhanced as the height of wrinkling and arching increases. (4) The improvement of grid deflection with membrane structure is better than that without membrane structure. According to the above experimental results, the quadrilateral wrinkling and hexagonal arching structure has a significant improvement on the load bearing and deflection of the mesh, and has the potential to make structural optimization of the mesh series products, which is suitable for practical application and promotion.

Compiling regional structures in geological databases: The giant quartz veins of the Pyrenees as a case study

Gathering and arranging specific data related to different types of geological structures in thematic and interactive databases has become central for the geosciences. However, a well-defined workflow to achieve this goal is currently lacking. We present a Geographical Information System-based method for the systematic compilation, evaluation, and interpretation of regional geological structures. The method is demonstrated by indexing 741 giant quartz veins cropping out along the Pyrenees (SW Europe) in a database called GIVEPY (GIant quartz VEins of the PYrenees). The GIVEPY database incorporates information of the geometry, distribution, and statistics of the indexed veins, as well as of their host rocks, and can serve as a starting point for boosting the understanding of giant quartz veins in the Pyrenees and other areas. The first-order structural controls on vein emplacement are hypothesized on the basis of vein distribution and linkage with other brittle and ductile structures, such as faults, folds, shear zones, and regional foliations. Furthermore, we discuss the strengths and limitations of the workflow and its potential application to other geological structures. The GIVEPY database is dynamic and freely available at https://givepy.info/.

The Kupol Epithermal Au-Ag Vein District, Chukotka, Far Eastern Russia

Abstract The Kupol epithermal Au-Ag vein district is located in the northern part of the Okhotsk-Chukotka volcanic belt, a Late Cretaceous subduction-related continental volcanic arc exposed for >3,000 km along the eastern coast of Russia. High-grade veins are hosted in the Kupol andesite sequence, a 300- to 1,000-m-thick, subhorizontal, layered sequence of andesite flows, sills, and ash tuffs, dated at 97 to 96 Ma (Cenomanian). The Kupol andesite sequence is underlain by mixed mafic-felsic volcanic units plus sedimentary rocks (“older volcanics”) and overlain by a >1-km-thick “upper felsic” sequence of dacitic-rhyolitic tuffs and associated dikes and flow domes, dated at 95 to 85 Ma, with local sequences of fluvio-lacustrine sedimentary rocks. The epithermal veins occupy N-striking, steeply dipping normal faults that cut thick coherent andesite flows and sills in the central-upper part of the Kupol andesite sequence. The district is dominated by the large Kupol vein (180.7 tonnes (t) Au and 1,986 t Ag produced to 2020), hosted by the 5.5-km-long Kupol fault, which accommodates normal, east-side-down displacement of up to 190 m. The Moroshka and Providence veins, 5 km east-southeast of Kupol, occupy shorter faults (1- to 2-km strike) with smaller vertical displacements (to 70 m). The Moroshka vein is dated at 93.5 ± 1.5 Ma (Turonian; 40Ar/39Ar method on adularia), and the timing of vein mineralization here and at Kupol overlaps with the early stage of upper felsic sequence magmatism. Veins contain subhorizontal ore shoots, controlled by the intersection of the steep faults with flat-lying Kupol andesite sequence stratigraphy and by steepening of the faults to a more dilational orientation as the inferred paleosurface is approached. Local structural controls are also evident, reflecting a component of oblique slip on the Kupol fault, with the thickest vein segments at steeply pitching jogs and relays. Main-stage veins grew via repeated encrustation by quartz-chalcedony ± amethyst ± lattice bladed calcite (replaced by quartz), with Au-Ag–bearing crustiform adularia ± clays ± sulfides/sulfosalts/electrum ± chlorite ± hematite bands. The main controls on Au grade are inferred to have been boiling, resulting in sharp vertical limits to high metal grades typical of epithermal veins, coupled with optimal dilation of the vein system where the hosting normal fault steepens near surface with decreasing differential stress. Although much of the displacement on the controlling faults is pre-mineralization in timing, lithified cataclastic breccia, coeval with some vein stages, and vein geometry patterns indicate that some vein development occurred contemporaneously during late normal displacement along the fault system. Waning of the hydrothermal system is marked by late carbonate fill, initially Fe dolomite, then coarse calcite as veins, matrix to vein breccia, and central vein cavity fill. The Kupol district veins have proximal adularia-quartz alteration (haloes meters wide), within an extensive (hundreds of meters in scale) clay alteration halo. Clays are zoned both vertically and laterally with respect to veins, with inner illite-chlorite that was magnetite-destructive (at highest paleotemperature; >220°C), grading outward and upward to illite/interlayered illite-smectite with kaolinite, then to an outer zone (or upper blanket) of smectite, at lowest paleo-temperature (<150°C). The boundary between the illite and smectite zones is interpreted to mark the interaction limit of paleo-hydrothermal systems with cooler groundwater. District-scale pathfinder element zonation correlates with clays, with S-Te-Bi-As in the illite-chlorite core and Sb-Cs-Tl(-As-Li) in the smectite blanket. Pathfinder zonation patterns at Kupol point to a magmatic source at depth or, more likely given the scale of the anomalies, multiple magmatic sources, with the surface clay zonation indicating the extent of coalesced paleo-hydrothermal systems associated with upflow plumes. This is the best-defined alteration record with geochemical signature for a complete district hosting a large, high-grade vein deposit. Early definition of clay and pathfinder element patterns across an entire epithermal district can be carried out at low cost to provide useful constraints on vein targeting.

Geometry and scale property of a gold-silver-bearing vein system associated with an oblique-slip fault zone at Gasado Island, Korea

Gasado Island, on the southwestern Korean Peninsula, comprises c. 50 Ma volcanic rocks that are cut by faults and fractures hosting low-sulfidation epithermal Au-Ag mineralization. In this study, we examined the relationship between the fault-fracture networks and auriferous vein systems to better understand the role of brittle structures in controlling hydrothermal fluid flow. Geometrical and fractal analyses were performed to express and quantitatively compare the vein geometries and thickness population. The results were as follows: (1) The geometrical analysis revealed a strong relationship between Au-Ag-bearing quartz veins and NE-SW-striking, oblique sinistral-normal faults, indicating that these structures are a key control on mineralization. (2) Box-counting fractal analysis applied to veins hosted by fault zone demonstrated that the D-values (fractal dimensions) are directly proportional to vein density – indicating that damage zones control vein density. (3) The linear traverse line analysis yielded cumulative frequency plots of vein thicknesses that showed obvious changes in the slope, which are reflected in the variable D-values. The cause of this slope variability is interpreted to be the presence of hybrid veins that fill secondary fault planes, which disturbs the original linear relationship shown by cumulative thickness distribution data. This study shows that vein density and physical properties are strongly controlled by the types, or existence, of fault damage zones. Understanding fault zone architecture may assist with the prediction of locations that concentrate mineralizing fluids and may benefit the initial stage of mineral exploration.

A progressive model for the development of the Cavanacaw Au–Ag–Pb vein deposit, Northern Ireland, and implications for the evolution and metallogeny of the Grampian Terrane

Deformed vein systems may exhibit complex geometries with kinematics that are not always easily reconciled within the overall tectonic framework and interpreted palaeostress fields. In ore exploration and mining, the misinterpretation of complex vein geometries as polyphase deformation, as opposed to progressive deformation, may be detrimental to developing effective exploration strategies or geometric models for ore bodies. An example of this is the Cavanacaw Au–Ag–Pb vein deposit in Northern Ireland which has previously been interpreted to have had a polyphase deformation history linking economic mineralisation to span both the Caledonian and Variscan orogenies. Here, we present structural analysis to demonstrate that the geometries and kinematics of the broadly N to WNW-striking vein system is more easily explained with a single progressive kinematic model incorporating overall sinistral shearing along Silurian ENE–WSW-striking transcurrent faults during the Scandian event of the Caledonian orogeny. This progressive deformation further accounts for a regional, abrupt ‘knee bend’ strike swing in Dalradian Supergroup rocks that is probably related to the wider mineralisation and penetrative mid-Silurian deformation in the area. Our analysis additionally implies that Cavanacaw is younger than the nearby Late Ordovician Curraghinalt deposit which is related to the Grampian event, but is also slightly older than the Early Devonian Cononish deposit in Scotland that similarly links to the Scandian event. This study ultimately demonstrates how an understanding of progressive deformation can have key scientific and economic implications by informing regional and tectonic deformation models and exploration strategies, respectively.

Internal Jugular Vein Geometry Under Multiple Inclination Angles with 3D Low-Field MRI in Healthy Volunteers.

Cerebral venous pathways are subjected to geometrical and patency changes due to body position. The internal jugular veins (IJVs) are the main venous drainage pathway in supine position. Their patency and geometry should be evaluated under different body inclination angles over a three-dimensional (3D) volume in the healthy situation to better understand pathological cases. To investigate whether positional changes in the body can affect the geometrical properties and patency of the venous system. Prospective. 15 healthy volunteers, of which seven males and median age 22 years in a range of 19-59. A 0.25-T tiltable MRI system was used to scan volunteers in 90° (sitting position), 69°, 45°, 21°, and 0° (supine position) in the transverse plane with the top at vertebra C2. A gradient echo sequence was used. Three observers assessed IJVs on patency and created automatic centerlines from which diameter and patency were analysed perpendicular to the vessel at every 4 mm starting at the level of C2. A Student's t test was used to find statistical difference (p < 0.05) in average IJV diameters per inclination angle. The amount of fully collapsed IJVs increased from 33% to 93% (left IJV) and 14% to 80% (right IJV) when increasing the inclination angle from 0° to 90°. In both IJVs, the mean diameter (±SD) of the open vessels was significantly higher at 0° than 90° with 6.3 ± 0.5 mm vs. 4.4 ± 0.1 mm (left IJV) and 6.6 ± 0.6 mm vs. 4.3 ± 0.4 mm (right IJV). Tiltable low-field MRI can be used to assess IJV geometry and its associated venous pathways in 3D under multiple inclination angles. Next to a higher amount of collapsed vessels, the average diameter of noncollapsed vessels decreases with increasing inclination angles for both left and right IJVs. 2 TECHNICAL EFFICACY STAGE: 1.

Creating patient-specific vein models to characterize wall shear stress in hemodialysis population

End-Stage Renal Disease (ESRD) patients require arteriovenous fistulas (AVF) that allow a mature vein to withstand hemodialysis. Unfortunately, venous thrombosis and stenosis in the cephalic vein arch after AVF placement is common and heavily influenced by hemodynamics. To better assess forces and flow behavior in the cephalic arch, we have built patient-specific millifluidic models that allow us to explore the complex interplay between patient-specific vein geometry and fluctuating hemodynamics. These 3D models were created from patient-specific intravascular ultrasound and venogram images obtained three- and twelve-months post AVF creation and fabricated into soft elastomer-based millifluidic devices. Geometric validation of fabricated phantom millifluidic device shows successful replication of original computational 3D model. Millifluidic devices were perfused with a blood-mimicking fluid containing fluorescent tracer beads under steady-state physiologic cephalic vein flow conditions (20 mL/min). Particle image velocimetry was employed to calculate wall shear stress (WSS) across the cephalic arches. Experimental WSS profile evaluation reveals that the physiologic cephalic arch model yields WSS values within physiologic range [76–760 mPa]. Moreover, upon comparing WSS profiles across all models, it is noticeable that WSS values increase as vein diameter decreases, which further supports employed experimental and analysis strategy. The presented millifluidic devices show promise for experimental WSS characterization under pathologic flow conditions to contrast from calculated physiologic hemodynamics and better understand WSS influence on thrombosis and stenosis in hemodialysis patients.

Function of arteries and veins in conditions of simulated cardiac arrest.

Introduction: The study examined the behavior of vasculature in conditions of eliminated cardiac function using mathematical modeling. In addition, we addressed the question of whether the stretch-recoil capability of veins, at least in part accounts for the slower response to simulated cardiac arrest. Methods: In the first set of computational experiments, blood flow and pressure patterns in veins and arteries during the first few seconds after cardiac arrest were assessed via a validated multi-scale mathematical model of the whole cardiovascular system, comprising cardiac dynamics, arterial and venous blood flow dynamics, and microcirculation. In the second set of experiments, the effects of stretch-recoil zones of venous vessels with different diameters and velocities on blood velocity and dynamic pressure analyzed using computational fluid dynamics (CFD) modeling. Results: In the first set of experiments, measurement of changes in velocity, dynamic pressure, and fluid flow revealed that the venous system responded to cardiac arrest more slowly compared to the arteries. This disparity might be due to the intrinsic characteristics of the venous system, including stretch-recoil and elastic fiber composition. In the second set of experiments, we attempted to determine the role of the stretch-recoil capability of veins in the slower response to cardiac arrest. During the second set of experiments, we found that this recoil behavior increased dynamic pressure, velocity, and blood flow. The enhancement in dynamic pressure through combining the results from both experiments yielded a 15-40% increase in maximum dynamic pressure due to stretch-recoil, depending on vein diameter under normal conditions. Conclusion: In the situation of cardiac arrest, the vein geometry changes continue, promoting smooth responses of the venous system. Moreover, the importance of such vein behavior in blood displacement may grow as the pressure on the venous side gradually decreases with time. Our experiments suggest that the driving force for venous return is the pressure difference that remains within the venous system after the energy coming from every ventricular systole spent to overcome the resistance created by arterial and capillary systems.

Preliminary data of the Cannero Riviera mineralized system (Southern Alpine Domain, Western Alps, Italy)

Geometry and composition of veins associated with ore deposits, combined with mineralogical and textural constraints, are indispensable to understand the evolution of mineralized systems. The never mined Cannero Riviera mineralized system (VCO province, Western Alps, Italy), has been detected in 2015 by Alpine Gold Lodes Snc and after investigated during the Oberto's Master Thesis in 2019. Preliminary field data, integrated microstructural and petrographic investigations, combined with SEM-EDS and ICP and XRF techniques are fundamental tools to unravel mineralized systems. Our results highlighted the strong relationship between orebody and the Rio Cannero Fault activity, well displayed mainly along the Cannero stream (N46°1'37''; E8°39'24''). This work allows unraveling, for the first time in this area, how different ore parageneses superimpose each other. Two mineralization styles have been detected. The first (Type a) is mainly made by mm-grained arsenopyrite, pyrite and pyrrhotine in quartz-carbonatic gangue, with sometimes important amounts of scheelite and gold. The second (Type b) is represented by less than mm-grained arsenopyrite, pyrite and galena accompanied by mm-grained scheelite, apatite, and electrum. Despite more data are needed to better constraint the structural framework, temperature, timing and the source of the ore fluids, our preliminary data suggest a new possible pre-Alpine deposit.

A methodology for biometric identification using vein geometry in infrared images of the back of the hand

A methodology for biometric identification using vein geometry in infrared images of the back of the hand

Stress fields of ancient seismicity recorded in the dynamic geometry of pseudotachylyte in the Outer Hebrides Fault Zone, UK

Heterogeneous sequences of exhumed fault rocks preserve a record of the long-term evolution of fault strength and deformation behaviour during prolonged tectonic activity. Along the Outer Hebrides Fault Zone (OHFZ) in NW Scotland, numerous pseudotachylytes record palaeoseismic slip events within sequences of mylonites, cataclasites and phyllonites. To date, the kinematics and controls on seismicity within the long active history of the OHFZ have been poorly constrained. Additional uncertainties over the relative location of a meteorite impact and possible pre-OHFZ brittle faulting also complicate interpretation of the diffuse seismic record. We present kinematic analyses of seismicity in the OHFZ, combining observations of offset markers, en echelon injection veins and injection vein geometry to reconstruct slip directions and stress fields. This new dataset indicates that a range of fault orientations, slip directions and slip senses hosted seismicity in the OHFZ. Such complexity requires several stress field orientations, in contrast with the NW–SE Caledonian compression traditionally attributed to frictional melting along the OHFZ, indicating that seismicity had a long-term presence across the fault zone. Persistence of strong frictional failure alongside the simultaneous development of weak fault rocks and phyllonitic shear zones in parts of the OHFZ has significant implications for understanding seismic hazard along mature continental faults. Supplementary material: Tables listing analysed orientation measurements plus further information and sensitivity testing of palaeostress analysis parameters are available at https://doi.org/10.6084/m9.figshare.c.5134797

Four-leaf clovers prove lucky for fuel cell design

Flow fields inspired by four-leaf clovers with optimized vein geometry offer advantages over traditional fuel cell structures.

Shale Anisotropy and Natural Hydraulic Fracture Propagation: An Example from the Jurassic (Toarcian) Posidonienschiefer, Germany

AbstractCores recovered from the Jurassic (Toarcian) Posidonienschiefer (Posidonia Shale) in the Lower Saxony Basin, Germany, contain calcite‐filled fractures (veins) at a low angle to bedding. The veins preferentially form where the shale is both organically rich and thermally mature, supporting previous interpretations that the veins formed as hydraulic fractures in response to volumetric expansion of organic material during catagenesis. Despite the presence of hydrocarbons during fracturing, the calcite fill is fibrous, and so, the veins appear to have contained a mineral‐saturated aqueous solution as they formed. The veins also contain myriad host‐rock inclusions having submillimetric spacing. These inclusions are strands of host rock that were entrained as the veins grew by separating the host rock along bedding planes rather than cutting across planes. The veins therefore produce significantly more surface area – by a factor of roughly 5, for the size of veins observed – compared to an inclusion‐free fracture of the same size. Analysis of vein geometry indicates that, with propagation, a fracture surface area increases with fracture length raised to a power between 1 and 2, assuming linear aperture‐length scaling. As such, this type of fracture efficiently dissipates elastic strain energy as it lengthens, stabilizing propagation and precluding dynamic crack growth. The apparent separation of the host rock along bedding planes suggests that the mechanical weakness of bedding planes is the cause of this inherently stable style of propagation.

Geology, mineralogy, ore fluid characteristics, and 40Ar/39Ar geochronology of the Kahang Cu-(Mo) porphyry deposit, Urumieh-Dokhtar Magmatic Arc, Central Iran

The Kahang Cu-Mo porphyry deposit is located in the middle part of the Urumieh-Dokhtar Magmatic Arc, Central Iran, and is hosted by middle to late Miocene (~14 Ma) porphyritic quartz-diorite and granodiorite stocks intruded into the Eocene tuff, basaltic andesite, and andesitic flow sequences. The Miocene intrusions are calc-alkaline in composition and reflect arc-type to collisional environments (Nb/Y ~ 0.6) based on Nb-Y, Sr/Y-Y, and La/Yb-Yb discrimination diagrams.Copper mineralization occurs within the quartz diorite and granodiorite porphyries and volcanic rock sequences, which have been extensively altered to a central potassic zone (biotite-rich-K-metasomatism), a medial quartz-sericite-pyrite (phyllic) zone, an outer argillic alteration zone, and a peripheral propylitic alteration zone. Hypogene mineralization predominantly occurs within the central potassic zone within veins and breccias. The grade of the mineralization (avgs. 0.6% Cu with 120 million metric tons (Mt) ore reserve and decreases outward from the potassic zone, through a transitional potassic-phyllic zone, to the phyllic zone. Supergene mineralization (5 Mt at 0.3% Cu) that is partially developed in upper parts of the system forms <10 million metric tons (Mt) of the total resource of the Kahang deposit.Three stages of mineralization are recognized based on vein geometry, mineral assemblages, and ore textures. Early-stage mineralization is characterized by the occurrence of quartz-magnetite-chalcopyrite ± molybdenite-pyrite assemblages in veins, veinlets, and breccias with biotite-K-feldspar envelopes. Main-stage Cu- (Mo) mineralization is represented by quartz-chalcopyrite ± molybdenite ± pyrite-gold assemblages in disseminations within biotite-K-feldspar-sericite-altered rocks, and is responsible for the bulk of economic Cu-(Mo) mineralization. Late-stage mineralization, characterized by quartz-pyrite-sphalerite-galena assemblages in veinlets, voids, and fractures with kaolinite-illite envelopes occurs in upper parts of the deposit, and overprints previous alteration and mineralization.Four main types of fluid inclusion are distinguished in quartz from quartz-sulfide veins and veinlets: type I vapor-rich (V) two-phase inclusions with vapor/liquid ratios of 60 to 90; type II liquid-rich (L-V) inclusions with vapor/liquid ratios of < 50; type IIIa and IIIb (L-V-S) hypersaline inclusions with vapor/liquid ratios of 45 to 85 and solid phase of < 30; and type IV (L-V-S-H) multiphase inclusions. Ore fluid salinities during the main-stage mineralization were approximately 35 wt% NaCl equiv at temperatures between 220 and 450 °C and pressures between 500 and 1000 bar, corresponding to depths between 1 and 3 km.The calculated δ18Ofluid and δDfluid values for quartz-biotite veins associated with potassic alteration range between 9.7 and 3.1‰ and − 52 to − 49.8‰, respectively, consistent with precipitation from a high-temperature primary magmatic fluid, which gradually mixed with meteoric fluids in later stages. The δ34Ssulfide isotope compositions of stages II and III-chalcopyrite and pyrite range from 3.6 to 8.6‰ consistent with deposition from an oxidized, sulfate-dominant, high-temperature magmatic-hydrothermal fluid.The 40Ar/39Ar ages on hydrothermal biotite from porphyry stocks and potassic alteration zones indicate that the hydrothermal activity and subsequent porphyry Cu- (Mo) mineralization occurred between 14.73 ± 0.05 and 14.87 ± 0.06 Ma.