Characteristics Of Deposits Research Articles

Multiscale computational fluid dynamics modelling of spatial ALD on porous li-ion battery electrodes

The self-limiting surface reaction characteristic of atomic layer deposition (ALD) makes it ideal for the surface modification of electrode materials for lithium-ion batteries (LIBs). Spatial ALD shows promise as a scalable method for the coating on pre-fabricated electrode sheets. As a strong-coupled multiscale process, various process conditions and microstructure parameters have great influences on the macroscale fluid dynamics and the pore-scale diffusion–reaction process, thus affecting the coating efficiency. This study presents a multiscale numerical model that combines computational fluid dynamics (CFD) with multilevel pore-scale diffusion–reaction kinetics to explore the spatial ALD process on porous LIB electrodes. The dynamic mesh method is utilized to simulate electrode movement. The considerable active surface-to-volume ratio of the porous structure limits the precursor infiltration depth due to the low diffusion rate and inadequate precursor supply. As the electrode velocity increases, an asymmetric distribution of precursor concentration under the injector is observed with a rapid decrease. Elevating both the precursor concentration and inlet gas velocity augments the coating depth by enhancing the supply of the precursor. The experimental data aligns well with our numerical results, verifying the accuracy of the multiscale CFD model. Our observations reveal that a relatively lower operating pressure, around 0.1 atm, compared to 0.01 atm and 1 atm, optimizes the deposition rate along the electrode depth during the half-ALD cycle, especially when the pore size is larger. Electrode porosity of about 0.4 notably improves coating uniformity by elevating the precursor diffusion rate. Predictions show that with a substrate velocity of 0.2 m/s, the coating depth on an electrode having higher porosity at the top compared to the bottom via atmospheric spatial ALD could reach a depth of 38 μm with a precursor utilization of 78 %.

Microplastic transport and deposition in a beach-dune system (Saunton Sands-Braunton Burrows, southwest England)

Although microplastics (MPs) are ubiquitous contaminants that have been extensively studied in the marine setting, there remain gaps in our understanding of their transport and fate in the coastal zone. In this study, MPs isolated from surface sediments sampled from a large beach-dune complex in southwest England have been quantified and characterised. Concentrations above a detectable size limit of 30 to 50 μm ranged from about 40 to 560 MP kg−1 dry weight but, despite local sources of plastics such as an estuary and seasonal tourism, there were no significant differences in median concentrations between different orthogonal foreshore transects and the dunes or according to zonal location on the beach. The majority of MPs were black and blue fibres of <1 mm in length that were constructed of polymers of density > 1 g cm−3 (e.g., rayon, polyester, acrylic). A significant correlation was found between MP concentration and the proportion of very fine sand (100 to 250 μm) but relationships with other granulometric or compositional markers of sediment (e.g., volume-weighted mean diameter, circularity, calcium content) were not evident. An association of MP concentration with very fine sand was attributed to similar particle depositional characteristics and the entrapment of fibres within small interstitial spaces. Overall, the observations reflect the wavelaid and windlaid deposition of MPs from a diffuse, offshore source, and, despite their role as accumulators of particles from the foreshore, dunes do not appear to act as a landward barrier of MPs.

Effects of the 2011 Tohoku‐oki tsunami and human activities on long‐term coastal geomorphic development in northeastern Tohoku, Japan

AbstractThe 2011 Tohoku‐oki tsunami caused large‐scale topographic changes along the Pacific coast of northeastern Japan. More than 10 years have passed since the tsunami waves struck the area. Today, because of reconstruction work, very few places exist where natural post‐tsunami topographic changes can be monitored continuously. For this study, the authors investigated topographic changes caused not only by the 2011 tsunami but also by natural and artificial activities during the 50 years before and after the tsunami based on aerial photographs, excavations and subsurface explorations using ground‐penetrating radar at the Osuka coast in Aomori prefecture, Japan. The site is rare because it is a protected area with few and superficial engineering activities, making it suitable for continuous observation of pre‐tsunami, syn‐tsunami and post‐tsunami topographic changes. The findings indicate that the 2011 tsunami waves generated large topographic changes: depositional and erosional features produced by the tsunami can be recognized, respectively, as tsunami deposits and erosional channels across the sand dunes. During the post‐tsunami phase, the sand volume at the coast quickly recovered naturally. Tsunami deposits and the erosional channels were well preserved underground even at 10 years after the event. However, dynamic movement of the dunes started after the tsunami. The shifting was attributable to the artificial clearing of coastal forests rather than the tsunami effects on the coast. Our results first indicate not only that the sedimentary features of paleo‐tsunamis but also the erosional features have some probability of being preserved in the subsurface of the beach and sand dunes at tsunami‐affected areas. Also, artificial activities such as deforestation are much more crucially undermining of the stability of the coastal geomorphology than the tsunami effects: the coast is now reaching a different status from its pre‐tsunami situation.

Постановка многокритериальной задачи анализа и прогнозирования гранулометрического состава взорванных горных пород

Changes in the mining and geological characteristics of solid mineral deposits, a sharp decrease in the ore grades in many ore fields as well as the intensification of surface mining methods define the need to develop scientific, theoretical and methodological foundations for improving the efficiency of the interaction between the technological elements within the Mine-to-Mill' (M2M) concept, which can be adapted to each specific mining operation and will help to streamline the operating costs. Drilling and blasting is the main technological operation to break the rock off the rock mass and crush it when mining solid minerals. The main purpose of drilling and blasting operations is to create rock material that has the necessary properties for smooth and efficient handling by mining equipment at the subsequent stages of the field development with due account of the technical and economic costs. Formation of the muck pile affects the subsequent technological processes of the mining operation, and consequently, the cost of the end product of the mining company. The purpose of the study was to develop a mathematical model for forecasting and analyzing the particle size distribution of rocks in the muck pile within the 'Mine-to-Mill' system. Methods used. The study is based on a comprehensive approach, which includes scientific analysis and generalization of previously published research results. From the methodological point of view, the study was based on the system analysis methods, as well as on the use of information technologies.

Three-dimensional seismic evidence for depositional undulations nucleated around pre-existing relief, South China Sea

Sediment undulations are widely distributed along continental shelf and slope worldwide. The driving mechanisms of undulations are crucial for assessing the long-term stability of continental slope, which, however, remain poorly understood. We used high-resolution 3D seismic data to investigate the internal architecture and origin of a field of seafloor and subsurface undulations along the slope of South China Sea (SCS). The undulations have narrow troughs and broad ridges. The reflection geometries in the troughs between undulations tend to be continuous and not offset by faults. These troughs terminate at different subsurface depths, commonly ranging from 50 to 400 ms in two-way travel time (TWTT) below the seafloor, often at locations related to subsurface geological structures, such as buried faults and steps within mass transport deposits (MTDs). These subsurface terminations therefore suggest that the undulations are probably depositional features not linked to creep-related basal detachment. The troughs between undulations display an absence of growth features, while the undulations increase in amplitude from base to top (characteristics that are also incompatible with gravitational deformation). Erosional and depositional features are commonly found in the undulations; thus, we interpret the narrow troughs between undulations to represent the areas where sediment-laden bottom currents undergo passage from supercritical to subcritical conditions. These troughs nucleated mostly from fault scarps and seafloor steps induced by past slope failures. Previous alternative interpretations report that these features originate from subsurface creep; alternatively, the present interpretation as sediment transport structures has significant implications for seafloor management and engineering projects.

Analysis of the Genetic Model of the Extremely Narrow Channel Shallow Water Delta in DL-A Oilfield, Bohai Bay Basin.

In recent years, the oil and gas reserves discovered in shallow water deltas in China have continued to grow. The research on shallow water delta deposition models and depositional genesis is becoming more and more mature. In this latest discovery, a unique type of extremely narrow channel shallow water delta deposit was found at the top of the V oil group in the lower part of the Minghuazhen Formation during the Neogene period at DL-A Oilfield, located in the Bohai Bay Basin. The width of most single channels in this deposit measures between 100 and 200m, which is relatively rare and differs from existing research. To better understand this unique narrow channel shallow water delta deposit, a range of analysis methods were conducted including trace element analysis, major element analysis, grain size analysis, core observation, casting thin section observation, 3D seismic analysis, and other methods. These analyses were used to determine the sedimentary environment and sedimentary genesis of the deposit in the study area. The results show the following: (1) The top of the V oil group in the lower part of Minghuazhen Formation was deposited with a strong oxidizing environment. In the early stage, the climate was dry and cold, and gradually changed to warm and humid in the late stage. (2) Due to the frequent exposure to the surface, obvious weathered surfaces and sedimentary discontinuities were observed on the cores; the particle size analysis shows that the lamina types developed in the study area are clastic-clay laminae and clay-clastic laminae, which are mostly developed in shallow lakes area. (3) Observations of cores and thin sections also indicated that the hydrodynamic conditions frequently changed in the study area, alternating between strong and weak hydrodynamic conditions in a short period due to the alternating occurrence of flood and dry periods during the rainy season. Weak hydrodynamic conditions and slow water flow result in insufficient undercutting and sidecutting of rivers. The alternating occurrence of flood periods and dry periods has led to the development of crevasse splays and frequent river channel diversions, resulting in the inability of long-term stable development of the river channel. Besides, the change of water level has also led to the rebuilding of the river. Therefore, the multiple effects led to the formation of an extremely narrow channel shallow water delta. The accuracy of the sedimentary model is verified by a comparative study of the Shaliu River and Buha River in the modern Qinghai Lake. The new extremely narrow channels deposition model proposed this time further improves the deposition theory. At the same time, the modern depositional characteristics of the Shaliu River and Buha River also reveal the reservoir deposition between channels that cannot be distinguished by seismic data, providing guidance for the development of oil and gas in the study area.

Substantiation of technological resource-saving conditions for the use of equipment in the sand deposit mining

The mining and technological features of the Gusarovsky deposit of molding sands mining under the conditions of technological limitations of the existing enterprise have been studied. The granulometric composition of balance reserve sands, as well as overburden rocks, was analyzed. In order to obtain a high-quality commercial product with a minimum content of fine and clay particles from the initial rock mass of the surface and watered ledges, the parameters of the hydromechanized complex were substantiated by mining and processing. The calculation is based on the three most available options for filling the mining and processing complex (MPC). To substantiate the rational parameters of the MPC and ensure the purification of the commercial product from fine impurities, a graphical characteristic of the hydraulic vertical classifier GKCD2000 was constructed when supplying clean water and at a slurry concentration of 10%. The graphical characteristics of hydraulic transport systems were constructed in accordance with the design diagrams of the accepted variants of the complex. To substantiate the rational parameters of the pumping station, the characteristics of the mining and processing complex were constructed when pumping clean water and slurry at a concentration of 10%. For the first time, the rational parameters of the technological complex of mining and processing, consisting of a suction dredger – a transport slurry pipeline – and a vertical hydraulic classifier GKCD2000, have been substantiated. The development of a technological complex of mining and processing will allow the existing enterprise to continue developing the deposit and obtaining high-quality commercial products under the conditions of technological limitations.

The Motion and Deposit Characteristics of Dry Granular Flow Based on Experimental Study

The Motion and Deposit Characteristics of Dry Granular Flow Based on Experimental Study

Geomorphic evolution of the craton-derived Sone megafan in the southern Ganga plain, India: A tectono-climatic interplay

The Ganga plain neotectonics has been studied from surface and sub-surface faults, frequent geomorphic readjustment, changing sedimentation pattern, piedmont progradation, pedological variation, and frequent earthquake occurrences. However, being neotectonically stable, the peninsular region’s geomorphic changes are governed by climatic fluctuations, contributing to the Ganga plain’s sedimentation. Therefore, peripheral craton sourced marginal alluvial deposits in the Ganga basin are appropriate features to study the control of both the Himalayan tectonics and climate of core peninsular region away from their respective source areas. This study uses a process-response approach model to describe the geomorphic development of the Sone megafan, located at the marginal part of the Ganga plain to the south of the Ganga River, bordering the Indian craton.Geomorphological mapping, field investigation of the depositional features, soil profiles, and Optical Stimulated Luminescence (OSL) chronology suggest four phases of geomorphic evolution, i.e., in 22–8 Ka, 8.0 Ka–7.3 Ka, 7.3 Ka–2.4 Ka, and 2.4 Ka–0.5 Ka on the Sone megafan. The different evolutionary phases are marked by channel and floodplain abandonment and soil profile development. The megafan surface is divided into four distinct geomorphic units (OdSP – Oldest Sone Plain, OSP – Old Sone Plain, YSP – Young Sone Plain, and AFP – Active Floodplain) based on OSL ages and soil properties. Geomorphology and soil suggest a mixed climate in the source and sink area. The arid climate in the catchment contributed to the sediment production, and the humid climate promoted its transport, which resulted in the largest depositional unit of the megafan, even during the arid period in the Ganga basin. Contrast to the north of the Ganga River, no surface faults are found on the Sone megafan. However, the tectonic activity of the bounded basement faults, i.e., the East and the West Patna faults, are well pronounced in the sediment distribution and fluvial response. Tilting and twisting the fault-bounded block controls the sediment remobilization in space and time. Thus, the climatic fluctuation in the source, the sink, and the activity of the basement faults, propelled by the Himalayan tectonics, contributed to the Sone megafan’s geomorphic evolution. Two events of the Ganga River’s encroachment at the distal part of the Sone megafan were recorded (2.4 ± 0.14 and 1.3 ± 0.16 ka). The correlation between OSL ages of megafan units, climatic fluctuations in the Sone River’s catchment, and established time windows of tectonic episodes in the Ganga basin has also been investigated. As the Sone and the Gandak megafans rest on the same tectonic blocks, their tectono-geomorphic responses to the Himalayan neotectonics are similar.

Age and Tectonic Setting of Layered Lead–Zinc Ore Bodies in the Xiaohongshilazi Deposit: Constraints from Geochronology and Geochemistry of the Volcanic Rocks in Central Jilin Province, NE China

The newly discovered Xiaohongshilazi deposit located in Panshi City, central Jilin Province, NE China, is a medium-scale Pb–Zn–(Ag) deposit. The Pb–Zn–(Ag) orebodies are divided into layered and vein-type orebodies, which have different ore geneses. The layered Pb–Zn orebodies are mainly hosted within and spatially controlled by the volcanic rocks. To constrain the age and tectonic setting of the layered Pb–Zn mineralization, we completed laser-ablation–ICP–MS zircon U–Pb dating and whole-rock major and trace element analyses of the ore-bearing volcanic rocks. The dacite samples were confirmed as belonging to the Daheshen Formation and were the main ore-bearing volcanic rocks for the layered orebodies. They yielded concordia U–Pb ages of 278.1 ± 1.8 Ma and 278.3 ± 1.8 Ma, respectively, indicating that the volcanic rocks from the Daheshen Formation and related layered Pb–Zn mineralization were formed in the early Permian. The andesite and rhyolite located above the layered orebodies yielded concordia U–Pb ages of 225.0 ± 1.1 Ma, 225.3 ± 1.5 Ma, and 224.7 ± 1.2 Ma, respectively; these substances are considered to be of the Sihetun Formation and were first reported in the area. The dacite samples associated with layered Pb–Zn mineralization were high in SiO2 (62.54–65.02 wt.%), enriched in LREEs and LILEs (e.g., Rb, Ba, and K), and showed depletion in HFSEs (e.g., P and Ti). It showed slightly negative Eu anomalies (δEu = 0.60–0.65) and negative Nb anomalies, with Th/Nb (1.12–1.21) and La/Nb (2.8–4.7) ratios, presenting subduction-related arc magma affinity formed in an active continental margin setting. In agreement with previous studies on zircon Hf isotopes (εHf (t) = +0.23~ +10.60) of the volcanic rocks from the Daheshen Formation, we infer that they were derived from the partial melting of the depleted lower crust. In conclusion, mineralization characteristics, geochronological data, geochemical features, and regional tectonic evolution suggest that two Pb–Zn–(Ag) mineralization stages from the Xiaohongshilazi deposit occurred: the layered VMS-type Pb–Zn mineralization associated with the marine volcanic rocks from the early Permian Daheshen Formation, which was induced by the subduction of the Paleo-Asian oceanic plate beneath the northern margin of the North China Craton, and the vein-type Pb–Zn–(Ag) mineralization caused by the subduction of the Paleo-Pacific Plate in the early Jurassic. Considering this, along with the mineralization characteristics of the same-type polymetallic deposits in this region, we propose that the early Permian marine volcanic rocks have great prospecting potential for the VMS-type Pb–Zn polymetallic deposits.

Role of Tau protein in long COVID and potential therapeutic targets.

Long COVID is an emerging public health burden and has been defined as a syndrome with common symptoms of fatigue, shortness of breath, cognitive dysfunction, and others impacting day-to-day life, fluctuating or relapsing over, occurring for at least two months in patients with a history of probable or confirmed SARS CoV-2 infection; usually three months from the onset of illness and cannot be explained by an alternate diagnosis. The actual prevalence of long-term COVID-19 is unknown, but it is believed that more than 17 million patients in Europe may have suffered from it during pandemic. Currently, there is limited understanding of the pathophysiology of this syndrome, and multiple hypotheses have been proposed. Our literature review has shown studies reporting tau deposits in tissue samples of the brain from autopsies of COVID-19 patients compared to the control group, and the in-vitro human brain organoid model has shown aberrant phosphorylation of tau protein in response to SARS-CoV-2 infection. Tauopathies, a group of neurodegenerative disorders with the salient features of tau deposits, can manifest different symptoms based on the anatomical region of brain involvement and have been shown to affect the peripheral nervous system as well and explained even in rat model studies. Long COVID has more than 203 symptoms, with predominant symptoms of fatigue, dyspnea, and cognitive dysfunction, which tauopathy-induced CNS and peripheral nervous system dysfunction can explain. There have been no studies up till now to reveal the pathophysiology of long COVID. Based on our literature review, aberrant tau phosphorylation is a promising hypothesis that can be explored in future studies. Therapeutic approaches for tauopathies have multidimensional aspects, including targeting post-translational modifications, tau aggregation, and tau clearance through the autophagy process with the help of lysosomes, which can be potential targets for developing therapeutic interventions for the long COVID. In addition, future studies can attempt to find the tau proteins in CSF and use those as biomarkers for the long COVID.

Spraying performance of umbrella wind-field-type atomization and its application to parameter optimization.

We designed an umbrella wind-field-type anti-drift spraying device to improve droplet deposit in the fruit tree canopy, reduce spray drift between fruit tree rows, and avoid uneven droplet deposit in the canopy. We used Computational Fluid Dynamics combined with wind field tests to optimize the parameters of the anti-drift spray device, and the results showed that airflow velocity at the outlet of the device after optimization was 24.5 m s-1 , which is 48% higher than that before optimization (16.5 m s-1 ) airflow velocity. We designed wind tunnel tests and field tests to analyze the anti-drift characteristics of the anti-drift spraying device. Wind tunnel test results showed that the side airflow velocity, outlet diameter, spray distance, and spray drift ratio were correlated. The mathematical models established by vertical and horizontal multifactor orthogonal tests were significant (P < 0.05, R2 0.947, 0.878, respectively). The results of the field tests showed that side airflow, velocity spray pressure and outlet diameter had significant effects on the droplet deposit characteristics (in descending order: the side airflow velocity, spray pressure, and outlet diameter). The maximum droplet deposit was 6.34 μL cm-2 when the side airflow velocity was 2 m s-1 , the spray pressure was 0.4 MPa, and the outlet diameter was 70 mm2 . When the side airflow velocity exceeded 2 m s-1 , the outlet diameter and spray pressure had to be reduced to ensure better droplet deposit. The results indicated that the umbrella wind field could reduce spray drift and ineffective deposit in off-target areas and provides a reference for the comprehensive analysis of the spray drift deposit law. © 2023 Society of Chemical Industry.

Review on the development of multi- and hyperspectral remote sensing technology for exploration of copper–gold deposits

Most Copper (Cu) and Gold (Au) deposits are accompanied by hydrothermal alteration, generally related to ore-forming hydrothermal fluids. Multispectral and hyper-spectral Remote Sensing (RS) technology is essential for Cu-Au mineral prospecting. This paper provides an overview of RS data and the research situation and development tendencies of RS exploration technologies related to Cu-Au deposits. Initially, RS geologists applied the Band Ratio (BR) and Principal Component Analysis (PCA) to extract hydroxyl and iron anomalies from Landsat RS data to characterize the hydrothermal alterations associated with Cu-Au deposits. In the era of advanced spaceborne thermal emission and reflection radiometry (ASTER), clay minerals, sulfate minerals, carbonate minerals, silica minerals, and iron minerals can be identified because of three Visible and near-infrared bands (VNIR), six shortwave infrared bands (SWIR), and five Thermal Infrared bands (TIR). Alteration of mineral assemblages can be carried out to map alteration zones, which are essential for calibrating Cu-Au alteration zones, such as the typical alteration zoning characteristics of Porphyry Copper Deposits (PCD). Because of its high spectral resolution, Satellite hyperspectral RS can quantitatively map surface alteration minerals to indicate the exploration of Cu-Au deposits. RS geologists have extensively researched matching libraries and field spectra for Alteration Mineral Mapping (AMM). However, subpixel mineral information caused by low spatial resolution and atmospheric factors has an unavoidable influence on satellite hyperspectral RS AMM, and it is essential to use low-altitude unmanned aerial vehicle (UAV) hyperspectral RS. UAV hyperspectral AMM combined with geochemistry and geophysics is a means of prospecting and exploring Cu-Au deposits.

Genesis and stages of mineral formation of the Zun-Ospa gold and silver deposit (Eastern Sayan)

The paper presents the general characteristics of the Zun-Ospa gold deposit. The mineral composition of ores is given. According to mineralogical studies we have been established two stages of mineralization: the first stage (hydrothermal), which was divided into four stages and the second hypergenic. The data of microprobe analysis of the mineral phases that make up the ores of the deposit are presented. We described gold in two generations, which are different both in composition and associations.

Understanding Chemical and Mineralogical Composition of Nahartangi Nephrite from Goshta

The geochemical mineralogical characteristics of the Nahartangi nephrite deposit in the Goshta district of Nangarhar province are investigated in this research. Nephrite is a Cyclosilicate mineral with a high silicate content. Ca2(Mg, Fe)5Si8O22(OH)2 is its chemical formula, and it is monoclinic. It's been discovered in metamorphic rocks across the arena. The nephrite zone of Nahartangi is linked to the Jalalabad structural band and the ophiolite complex. Jalalabad is a region in eastern Afghanistan, southeast of Nuristan. As a result, this belt is associated with the upper or late Cambrian. The age of the rocks in this quarter is related to the Archean-Mesoproterozoic AR-PR2. This manuscript offers the first systematic mineralogical and geochemical observation of the Nahartangi nephrite deposit electronic probe Microanalysis, X-ray fluorescence spectroscopy (XRF) and mineralogical analysis. The Nahartangi nephrite was investigated using an XRF and petrographic microscope. According to field research, dolomitic marble is involved in Nahartangi nephrite deposits close to the intrusive granitoids. According to petrographic investigations, nephrite is mostly made up of fine-grained actinolite, schist, and dolomite, all of which are metamorphic minerals. Through every phase, nephrite samples had low Fe/(FeO+MgO) values (8.2524.17%) according to geochemical analysis, and SiO2 (81.30%), Al2O3 (3.22), and CaO (17.41%) were also low and 1.21% NiO content, as well. Chemical records analysis and interpretation of Mg+Fe percentages indicate that actinolite is the type of nephrite. The formation of veins and hydrothermal lenses in contact with serpentinite and carbonates has produced nephrite deposits. Dolomitic marble rocks are the specific rocks found near the study area. The economy and value are immediately impacted by color and its transparency. The presence of Mg elements causes the nephrite from the Goshta district to appear green.

Deposit comminution in a weak variably-cemented breccia rock avalanche

Rock avalanches display a distinct and complicated behavior that is not yet completely understood. Analyzing the deposit characteristics is crucial for studying the comminution mechanism during its emplacement. Combining field investigation, image processing, and numerical modeling, we explore the deposit characteristics and comminution process of the Wangjiapo rock avalanche triggered by the Mw6.2 Ludian earthquake. First, we use UAV photogrammetry to obtain a three-dimensional point cloud model and a digital orthophoto, from which we semi-automatically extract the geometry and position of 80,602 blocks by adopting a new block photo-analytical procedure, in addition to a further 4388 coarse blocks that were mapped from manual procedure. We analyze the longitudinal and transversal variation of the block distribution within the deposit. Large boulder content was more abundant in the middle part, while the fine blocks were distributed more evenly. Blocks were prevalently equant-sphere (ES) shaped with no dependence on volume and location, but the roundness increased significantly with runout. Additionally, we find fractal dimensions ranging from 1.42 to 1.83, lower with respect to other rock avalanches, probably due to the high weakness of materials. Furthermore, we propose two comminution models based on the significant differences observed between the eastern deposit II and western deposit III, which were caused by variably-cemented breccias. Finally, numerical modeling indicates that the large amount of fine material damped the grain-grain velocity during runout, leading to a limited spread of the rock avalanche and so explaining the short displacement of the front observed.

Genesis of the Graphite from the Tugeman Graphite Deposit, Xinjiang, China: Evidence for Carbon Isotope Refining by Fluids Associated with the Ductile Shear Zone

The Altun orogenic belt is situated along the northern boundary of the Tibetan Plateau. In this study, we present an analysis of the ore deposit, mineral composition, and carbon isotope signatures of the Tugeman graphite deposit within the Altun orogenic belt. The graphite in the Tugeman graphite deposit occurs within graphite-bearing schists and marble. Graphite enrichment is observed in the ductile shear zone. The carbon isotope values of graphite range between −18.90‰ and −10.03‰ (with an average value of −12.70‰). These values differ significantly from those observed in organic matter and marine carbonates, suggesting the occurrence of a mixing process involving reduced carbon fluid derived from biological organic material during regional metamorphism as well as a potential influx of oxidized carbon fluid from external sources. In addition, the metamorphic temperature of Tugeman graphite calculated from Raman spectroscopy is between 494 °C and 570 °C, which indicates that the disordered material is transformed from greenschist-amphibolite facies metamorphism to moderate-crystalline graphite. Combining the geological and carbon isotope characteristics of the Tugeman graphite deposit, we argue that the Tugeman graphite deposit is a regional metamorphic graphite deposit of biogenic origin, and during the late stage of metamorphism, it underwent interaction with fluids.

Atypical chromitite deposit in the Gaositai mafic-ultramafic complex, North China Craton: Geochemical, geochronological, and isotopic systematics

The Gaositai mafic-ultramafic complex in the North China Craton hosts a significant chromitite deposit featuring morphological and geochemical characteristics that deviate from the usual characteristics of typical high-Cr and low-Al podiform chromitites. Field observations and microscopic studies reveal notable variations in textural layering, mineralogy, and geochemical composition, challenging conventional features of stratiform chromitite deposits. Zircon UPb ages indicate that chromitite is most likely Carboniferous-Permian in age (330–275 Ma), but also contains numerous inherited zircons with concordant ages as old as 2544 Ma, reflecting a complex geological evolution. Post-formation metasomatic or metamorphic imprints can be evident by concordant zircon ∼247 Ma. Variable zircon εHf(t) values (−15 to +9.6) and depleted mantle model ages (432 to 2819 Ma) attest the presence of heterogeneous or reworked source materials.The PGE and trace element characteristics of the Gaositai chromitite are comparable to the geochemical features of Bushveld and Great Dyke deposits. Pyrite, millerite, norsethite, galena, and PGM (mainly OsIr alloys) inclusions are ubiquitous in chromite. Galena inclusions with homogenous Pb-isotopic ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) suggest a mixed sources of lead. In contrast, pyrite inclusions display significant variations in δ34SV-CDT values (−0.11 ‰ to 18.31‰) indicative of a crustal origin of sulfur. Bulk-rock ReOs isotope data of 0.1264–0.1294 shows 187Os/188Os ratios similar to abyssal peridotites, implying a potential connection between chromitite and the host ultramafic rocks. Highly disparate mantle model ages (55 to 2141 Ma) and re-depletion ages (28 to 692 Ma) suggest disturbance of the ReOs isotopic system during post-formational metasomatic or metamorphic events. These variations may, alternatively, reflect heterogeneity by subduction components. The obtained results do not support the Alaskan-type genesis of the host complex, but point towards an atypical stratiform type.

The gold mineral systems of the West Qinling orogen, central China: New insight from the Baguamiao gold deposit

The Baguamiao gold deposit is the first large deposit discovered in the West Qinling orogen in central China in the 1990 s. However, the occurrence of invisible gold in the deposit has not been reported. There is also no consensus on whether magmatic activity is involved in the gold mineralization, the style of mineralization, and the mechanism of gold precipitation. In this study, the in-situ trace elements, and chemical mapping of pyrite and pyrrhotite in the Baguamiao gold deposit were carried out for the first time. These data combined with the C-H-O isotope data of quartz, ankerite and calcite were used to determine mineralization process. In the Baguamiao gold deposit, five types of pyrite (Py0 to Py4) and pyrrhotite (Po0 to Po4) were identified, corresponding to the sedimentary-diagenetic period and four stages of mineralization (Stage I to Stage IV), respectively. From stage I to stage IV, gold mineralization in pyrite and pyrrhotite occurs as either visible or invisible crystals. The latter occurs dominantly as lattice-bound solid solutions (Au+) and is related to the content of Cu and Te. Co and Ni contents and Co/Ni ratios indicate that pyrite and pyrrhotite are magmatic-hydrothermal origin and affected by fluid-rock interaction. The change of Se and Te concentrations in pyrite and pyrrhotite indicates that oxygen fugacity (ƒO2) was increased from stage I to stage II, and then decreased during stage III and stage IV. In addition, the δ18O values of quartz, calculated δ18OH2O values of the ore-forming fluids and δ13C values range from 16.9 to 20.3 ‰, 7.7 to 12.9 ‰, and − 19.3 to + 0.2 ‰, respectively. Such isotopic signature records typical characteristics of orogenic gold deposit. The ore-forming fluid is a mixed hydrothermal solution involving metamorphic water, magmatic water, and meteoric water, and mixed with marine carbonate and sedimentary organic matter. Gold was precipitated by phase separation, fluid-rock interaction, and fluid mixing. Combined with the tectono-magmatic evolution, metamorphic deformation, and gold mineralization age of the West Qinling orogen, it can be concluded that with the closure of the Mianlue portions of the East Paleo-Tethys Ocean, the Baguamiao gold deposit was formed in the post-collisional extensional environment between the South China Block and the North China Block in the Late Triassic and is an orogenic gold deposit reference to the crustal continuum model.

Evaluating the Impact of Redox Potential on the Corrosion of Q125, 316L, and C276 Steel in Low-Temperature Geothermal Systems

Time series experiments were used to explore the fluid redox impact on the corrosion of Q125, 316L, and C276 steels in low-ionic-strength and neutral water at temperature and pressure conditions associated with low-temperature geothermal systems. After exposing polished samples of each steel grade to an oxidizing (H2O2) and a reducing (Zn-doped) fluid for intervals of 24 h, 1 week, and 6 weeks, the atomic force microscopy results revealed general corrosion for Q125, while 316L and C276 exhibited pitting, crevice expansion, and edge attack corrosion. Secondary depositional features are frequently found as topographic highs, adjacent to pitting corrosion. These features may be identified as there is a very strong spatial correlation between the height retrace and phase retrace surface maps. All steels became progressively rougher over time after exposure to both fluids, while the corrosion rates were more complex. Samples exposed to the reducing fluid experienced an increase in the corrosion rate over time, while C276 and 316L experienced a decrease in the corrosion rate. Finally, a novel data validation technique was developed to address the intrinsic scalability of corrosion. The results indicate that the AFM scan area does not affect the measured surface roughness over nearly three orders of magnitude.