Depth Of Deposition Research Articles

Геофизические исследования на разных этапах освоения месторождений медистых песчаников в Казахстане

Using the example of the Zhaman-Aybat deposit, the possibilities of geophysical methods at the stages of forecasting and solving prospecting and exploration geological problems of deposits of copper sandstones in Kazakhstan are shown. The position and dimensions of the Zhaman-Aybat structure and the depth of productive deposits are reliably determined by seismic exploration. According to the local positive anomalies of the gravitational field, separate blocks of rocks were identified, and according to the data of vertical dipole sounding, the depth of the high-resistance horizon identified with the roof of the rocks of the Zhezkazgan formation was determined. By probing the formation of the field in the depth range of 500- 800 m, local anomalies associated with productive deposits of the Taskuduk formation were traced. Geophysical studies of wells and the results of testing have increased the reliability of determining the parameters necessary for recalculation of copper ore reserves. Deep drilling has confirmed the high accuracy of geophysical work.

Multi-hazard stress testing under extreme rainstorms in the Shenzhen metropolitan area

ABSTRACT A severe rainstorm can trigger numerous natural hazards of multiple types in cities with hilly terrain, such as landslides, debris flows, and flooding. Such compound hazards may pose much greater risks than a single hazard to the safety of residents and infrastructures. This study focuses on a metropolitan area of Shenzhen, China and develops a multi-hazard stress testing method for hazard risk management against extreme rainstorms. The probable maximum precipitation in Shenzhen is first estimated using the storm transposition method considering orographic intensification and moisture maximisation, with the centre peak amount being 1441 mm in 24 hours at Tanglang Mountain. An integrated physically-based multi-hazard simulation model, EDDA, is then utilised to simulate the processes of initiation, propagation and transformation of landslides, debris flows and flooding in a unified manner. Under the designated extreme rainstorms of a 1000-year return period and 85% of probable maximum precipitation, deposit depths of landslides and debris flows can be large in some urban areas near the foot of Tanglang Mountain; flooding can be very extensive in the flat built-up regions, with 21.8% and 31.7% of the study area flooded, respectively. The produced multi-hazard maps can facilitate the design of risk mitigation measures against extreme rainstorms.

Competitive co-diffusion as a route to enhanced step coverage in chemical vapor deposition

Semiconductor devices are constructed from stacks of materials with different electrical properties, making deposition of thin layers central in producing semiconductor chips. The shrinking of electronics has resulted in complex device architectures which require deposition into holes and recessed features. A key parameter for such deposition is the step coverage (SC), which is the ratio of the thickness of material at the bottom and at the top. Here, we show that adding a co-flow of a heavy inert gas affords a higher SC for deposition by chemical vapor deposition (CVD). By adding a co-flow of Xe to a CVD process for boron carbide using a single source precursor with a lower molecular mass than the atomic mass of Xe, the SC increased from 0.71 to 0.97 in a 10:1 aspect ratio feature. The concept was further validated by a longer deposition depth in lateral high aspect ratio structures. We suggest that competitive co-diffusion is a general route to conformal CVD.

Magnetic field enable lithium ions to penetrate lithophilic 3D collectors and enhance electrochemical performance

Abstract Lithium metal batteries, celebrated for their exceptional energy density, are promising for advanced energy storage. Nevertheless, the dynamic deformation of lithium metal during cycling often leads to the unchecked proliferation of lithium dendrites, compromising the solid electrolyte interface. This not only deteriorates cycle stability but also poses significant safety risks. In our approach, we develop a three-dimensional lithium-affinitive composite current collector, utilizing an external magnetic field. The lithiophilic nature of V2O5, coupled with the deformability support provided by nickel foam and the depth-enhancing influence of the magnetic field on lithium metal deposition, collectively contribute to a more controlled and stable lithium environment. Our findings indicate that this novel setup allows for a lithium metal deposition depth of up to 310 μm, markedly curtailing the growth of dendrites in successive cycles. Remarkably, batteries reassembled with this magnetically-enhanced, lithium pre-deposited current collector exhibits a coulombic efficiency of 98.3% after 320 cycles at 1 mA cm-2. Moreover, a full cell, equipped with LiFePO4, delivers an initial capacity of 158.4 mAh g-1 at 1 C.

Controlling Nickel Deposition Depth in Mesoporous Silicon through Wetting and Deposition Kinetics

A strong mechanical and electrical connection between silicon (Si) and a metal film, such as nickel (Ni) or copper (Cu), is essential for several fields of application such as microelectronics, MEMS, analytical systems, biomedical devices and energy storage and conversion. The strongest connection can be achieved by mechanical interlocking of both materials, i.e. by increasing the adhesive surface area and by creating hooking structures. Functionalizing the surface by etching mesopores into the Si creates an interlocking structure which can drastically increase the mechanical integrity of the Si-metal composite. A complete pore filling of the structure can be achieved by depositing at low current densities and by using an electrolyte with a high micro throwing power, i.e. with a high ability to fill coat through-holes. However, preventing the metal ions from penetrating the porous structure or even controlling the penetration depth of the metallization is much more challenging by electrochemical means.In this contribution, we present an inexpensive and easily scalable method to control the penetration depth of a Ni layer into mesoporous Si (Ni@Si) that is not making use of macromolecular Ni-complexes. Instead, the process exploits the hydrophobic nature of freshly etched, and hydrogen-terminated Si. In combination with an aqueous Ni-electrolyte, such a hydrophobic mesoporous Si leads to the Cassie-Baxter state where the liquid will not enter the pores, leaving them air-filled. A pre-treatment of the porous silicon was shown to restrict the Ni deposition to a tunable depth. The penetration depth should be chosen about twice as deep as the pore diameter to get a strong mechanical connection.In addition to tailoring the surface energy of the porous Si through the pre-treatment, it is of great importance to choose the right plating parameter. In this contribution we will discuss how voltage and current profiles should be adapted to the electrochemical system and how these parameters get influenced by factors such as temperature, electrolyte flow, passivation kinetics, etc. Our method enables a homogeneous nucleation of Ni grains within the pre-treated pore openings.We demonstrate that the resulting interlocked Ni@Si metallization is well suited for a layer transfer process of a full-scale 15.6 x 15.6 cm2 wafer. The interconnection can even withstand the cycling of Si in a battery. Si, being the anode material with the highest known gravimetric capacity for Li-ion batteries, can expand and shrink by a factor of 4 during lithiation and delithiation, respectively. These enormous volumetric changes lead to a fracturing and cohesive failure of the Si, which is the main challenge in commercializing pure Si anodes (without any binder and conductive carbon). The Ni@Si interlocking structure we have developed provides an interface that can withstand these large volumetric changes without showing signs of delamination of the porous Si from the deposited Ni current collector by adhesive failure.

Extreme sulfur isotope heterogeneity in individual Ediacaran pyrite grains revealed by NanoSIMS analysis

Pyrite sulfur isotopic composition (δ34Spy) is a crucial proxy for reconstructing ancient Ediacaran marine environments. However, recent in situ isotopic analyses of sedimentary pyrite have revealed distinct δ34Spy signatures among different pyrite morphologies, indicating that secular changes in bulk δ34Spy may reflect variations in proportions of different pyrite morphologies rather than environmental signals. Up to now, intragrain isotopic patterns within individual pyrite grains have not yet been extensively investigated for Ediacaran samples. The absence of this specific data set has hindered our ability to understand current complexities of bulk δ34Spy in reconstruction paleoenvironment. This study aims to elucidate δ34Spy patterns by conducting in situ isotopic analysis on pyrite grains from Ediacaran drill-core samples. We employed scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Raman spectroscopy, and nanoscale secondary ion mass spectrometry (NanoSIMS) to examine the crystal texture, element atomic ratios (S/Fe), mineral composition, and in situ isotopic composition within single pyrite grains. SEM-EDS observations reveal that the euhedral/subhedral pyrite crystals generally exhibit uniform mineral texture, although some grains show varying degrees of dissolution edges and surface cavities. Raman spectroscopy demonstrates the possible presence of pyrrhotite mineral within pyrite grains at some specific sites and points. In situ isotopic analysis reveals significant intragrain δ34S heterogeneity, with difference reaching up to 69.3‰ on a micrometer scale. Distinct deposition depths and burial rates may contribute to the varying value ranges and degrees of isotopic heterogeneity amongst pyrite grains. A model suggesting rapid precipitation from numerous nucleation sites simultaneously could account for the observed intragrain heterogeneity of in situ δ34S values. Pyrite grains exhibit general atomic S/Fe ratios of > 2, potentially due to the presence of trace elements incorporated into the pyrite structure. The occurrence of pyrrhotite leads to a slightly positive correlation between in situ δ34Spy values and S/Fe ratios, yet the 32S-enriched pyrrhotite plays less substantial in generating intragrain δ34S heterogeneity of pyrite grains. Our findings reveal clear isotopic heterogeneities within individual pyrite grains, in addition to the notable δ34Spy differences among pyrite of various morphologies. These results highlight significant microenvironmental heterogeneity and dynamic sulfur pool mixing on rapid short-term timescale during pyrite growth.

Reducing the diameter of the atomized particles by coating polymer membrane on the inner wall of micro-tapered holes of the ultrasonic mesh atomizers

Atomized inhalation therapy with its rapid efficacy, low side effects and high medicine utilization, has become a crucial method for treating respiratory diseases. The depth of atomized particles deposition in the respiratory tract mainly depends on the particle diameter, making the reducing of the atomized particle size crucial for medicine deposit in lung. In the existing literatures, for the widely used dynamic mesh atomizer, the majority of the researches focused on the mechanical structure and the vibration characteristics of the atomizers. However, there is little researches on the micro-tapered holes of the metal sheet of the atomizer, despite the fact that the diameter of these tapered holes determines the size of the atomized particles. Due to the processing technology, the diameter of the micro-tapered holes cannot be further reduced, which greatly limits the development of the dynamic mesh atomizer in inhalation therapy. In this study, we consider the use of polymer coating on the inner wall of the micro-tapered holes to eliminate burrs, reduce the diameter of the holes, and ultimately reduce the size of the atomized particles. A theoretical model of the initial thickness of the coating polymer membrane and the rupture depth under the uniform air pressure applied to a single tapered hole was established. The metal sheets with different initial coating thicknesses were processed to verify the theoretical model by observing the quality of the inner surface and measuring the diameter of the holes. The particle size measurement experiment results show that when the initial coating thickness was 3 μm and 4.5 μm, the average particle sizes were reduced by 12.5 % and 23.2 %, respectively. Therefore, the proposed method can effectively reduce the atomized particles size, which helps to efficiently deposit atomized drugs in the lungs.

Genesis of the Bailugou Vein-Type Zinc-Lead-Silver Deposit, Eastern Qinling Orogen, China: Constraints from Ore Geology and Fluid Inclusions

The Bailugou vein-type zinc-lead-silver deposit is located in the Eastern Qinling Orogen, China. There has been a long-standing debate about whether its formation is related to magmatism or metamorphism. To determine the origin of ore-forming materials and fluids, we conducted a geological and fluid inclusion investigation of the Bailugou. Field surveys show that the vein-type orebodies are controlled by faults in the dolomitic marbles of the Mesoproterozoic Guandaokou Group, and they are distal to the regional Yanshanian intrusions. Four ore stages, i.e., quartz–pyrite ± sphalerite (Stage 1), quartz–polymetallic sulfides (Stage 2), dolomite–polymetallic sulfides (Stage 3), and calcite (Stage 4), are identified through microscopic observation. The homogenization temperatures of measured fluid inclusions vary in the range of 100 °C to 400 °C, with the dominating concentration at 350 °C to 400 °C, displaying a descending trend from early to late stages. The estimated formation depth of the Bailugou deposit varies from 2 km to 12 km, which is deeper than the metallogenic limit of the epithermal hydrothermal deposit but conforms to the typical characteristics of a fault-controlled deposit. The ore-forming fluid in Stage 1 originates from a fluid mixture and experiences a phase separation (or fluid immiscibility) between the metamorphic-sourced fluid and the fluids associated with ore-bearing carbonate-shale-chert association (CSC) strata. This process results in the transition to metamorphic hydrothermal fluid due to water–rock interactions in Stage 2, culminating in gradual weakening and potential fluid boiling during the mineralization of Stage 3. Collectively, the Bailugou lead-zinc-silver mineralization resembles an orogenic-type deposit formed by metamorphic fluids in the Qinling Yanshanian intracontinental orogeny.

The Erosion Pattern and Hidden Momentum in Debris‐Flow Surges Revealed by Simple Hydraulic Jump Equations

AbstractThe erosion‐deposition propagation of granular avalanches is prevalent and may increase their destructiveness. However, this process has rarely been reported for debris flows on gentle slopes, and the contribution of momentum hidden under the surge front to debris‐flow destructiveness is ambiguous. Therefore, the momentum carried by the apparent surge front is often used to indicate debris‐flow destructiveness. In this study, the erosion‐deposition propagation is confirmed by surge‐depth hydrographs measured at the Jiangjia Ravine (Yunnan Province, China). Based on simple hydraulic jump equations, the eroded deposition depth of surge flow is quantified, and the erosion pattern can be divided into two patterns (shallow and deep erosion). For surge flows with erosion‐deposition propagation, significant downward erosion potential is confirmed, and debris‐flow surge erosion is considered the deep erosion. The total momentum carried by surge flow is further quantified by two Froude numbers (surge‐front and rearward Froude numbers) and verified through the field observation of surge flows. The total momentum of surge flow not only originates from the apparent surge front, but also includes the momentum within the eroded deposition layer. This study provides a theoretical approach for quantifying the upper limit of erosion depth and revealing the destructiveness of debris‐flow surges. A perspective on the importance of substrate deposition for debris‐flow erosion on gentle slopes is emphasized, as this approach can improve the reliability of debris‐flow risk assessment.

Determination of geochemical stability of swamp ecosystems of the taiga zone of Western Siberia to anthropogenic impact

Relevance. The need for scientifically based regulation of impacts on wetland ecosystems taking into account their specificity and geochemical stability. Aim. To determine the geochemical stability of wetlands in the taiga zone of Western Siberia to pollutants for two typical cases associated with: 1) operation of sludge pits; 2) discharge of domestic and industrial wastewater. Methods. Mathematical modeling, statistical methods. Results and conclusions. The authors have carried out the analysis of the results of studies of the chemical composition of wetland waters and extracts from peat and mineral soils of wetlands in the taiga zone of Western Siberia (mainly in the Tomsk region, as well as in the adjacent territories of the Khanty-Mansiysk Autonomous Okrug, Novosibirsk and Omsk regions). They obtained the estimates of the average values of geochemical indicators of wetland waters and peat by the depth of the peat deposit in peat bogs with varying degrees of anthropogenic impact. The paper introduces the method for assessing the anthropogenic impact of wastewater discharge and geomigration on swamps in areas where oil and gas facilities are located (permissible concentrations in wastewater entering swamp ecosystems), taking into account the «geochemical background» and sorption capacity of peat. In particular, the authors substantiated and tested the method for assessing the values of permissible concentrations, which should be considered as a «relatively safe» level of impact on swamp ecosystems, at which secondary pollution of swamp waters is not expected. It is shown that anthropogenic changes are mainly limited vertically by the upper layer of the peat deposit up to 1–2 m, and horizontally (within the active horizon of the peat deposit) – by areas up to 100–200 m.

Ichnotaxonomy of microboring traces in marine aphotic depths

Microboring traces in carbonate skeletal fragments deposited in aphotic depths of the oceans are studied, evaluated, and described with respect to their marine ecology and palaeoecology as well as ichnotaxonomy. Sand-size deep sea sediment particles dredged from depths ranging between 600 and 3266 m of the Bermuda Pedestal, Central Atlantic Ocean, the Florida Escarpment, the Mediterranean Sea, the Red Sea and the Indian Ocean were studied. Following ichnological rules, trace fossils are described as ichnogenera and ichnospecies, defined as products of organismal behaviour. This, in our view, refers to the growth habit of microboring organisms in response to environmental stimuli within the substrate they penetrate. The problem of palaeobathymetry is discussed in conjunction with the distinction between light-dependent and light independent microboring organisms, with the emphasis on the latter. We considered this distinction to be important because only the light-dependent microborers have been recognized as indicators of ancient depositional depths, whereas the light-independent ones are expected to occur at any depth, subject to the availability of organic nutrients. Microboring organisms often leave morphologically similar traces due to convergent evolution. Their responses may change during their life cycle; they may produce different traces when pursuing their vegetative vs. reproductive functions. New ichnotaxa are described. All are regarded as organotrophs given their aphotic zone deep sea origin. This work presents the most complete set of deep sea microbial euendolith traces, to date.

Study of the evolution of density and particle transport during density relaxation phase after pellet fueling on the EAST tokamak

Abstract The impact of pellet injection depth on particle transport characteristics and density profile evolution during the post-pellet density relaxation phase is investigated on the experimental advanced superconducting tokamak. Experiments were conducted under similar background plasma conditions and the results showed that variations in pellet deposition depths led to differences in density profiles despite comparable core fueling efficiencies. By computing the effective particle transport coefficients immediately after the pellet injection, it is found that the differences in density profiles are mainly due to significantly different transport velocities in the inner region of ρ < 0.4. The potential influence of pellets on electrostatic turbulence in this region is investigated using the trapped gyro Landau fluid model and CO 2 laser collective scattering diagnostics. The simulation suggests that the increase in transport coefficients following pellet injection is attributed to the destabilization of lower-k modes rather than the higher-k modes within the diagnostic measurement range.

Modeling pore fluid pressure and deformation in unsaturated soils under gravitational compaction and cyclic loading

Cyclic loading of fluid-bearing soils often induces excess pore water pressure, leading to accumulation of strain in the solid matrix. Additionally, variations in material density and volumetric fraction due to gravitational effects generate momentum forces, which subsequently cause deformation in the soil. In this paper, we present a mathematical framework of poroelasticity that generalizes the simultaneous action of gravitational body forces and cyclic loading to analyze solid deformation and fluid pressure dissipation in partially-saturated porous media. To account for the effect of gravity, the gradient of the vertical displacement needs to be treated as an additional dependent variable alongside pore air and water pressures.We numerically solve a mixed strain-controlled and pressure-prescribed boundary-value problem using a finite difference scheme as a representative example to quantify the impact of gravitational forces. Our results show that gravitational compaction affects both total settlement and excess pore water pressure, with its influence being particularly significant at lower water saturations, regardless of excitation frequency, soil depth, or type. The effect of gravity is more pronounced in soils with higher compressibility but appears insensitive to excitation frequency. Notably, the gravitational effect correlates linearly with the depth of the soil deposit and, therefore, should be well integrated into the consolidation theory of poroelasticity.

Stochastic hazard assessment framework of landslide blocking river by depth-integrated continuum method and random field theory

Landslide-induced barrier dams pose a threat to the safety of humans, livestock and nearby infrastructures. The efficient assessment of landslide blocking river is crucial for disaster prevention and mitigation solutions. This study proposes a novel stochastic assessment framework to evaluate the landslide blocking river through the prediction of their deposition depths and considering the heterogeneity of shear strength parameters on the potential sliding surface. The depth-integrated continuum method (DICM) is used to simulate the landslide runout process. Using an enhanced Karhunen-Loève expansion (KLE) method, the spatial variations in soil's shear strength parameters are modeled by random fields to incorporate the effects of soil's spatial heterogeneity on the landslide deposition pattern. Subsequently, the multi-response surrogate model is constructed to relate the random field variables to the deposition depths based on extreme gradient boosting (XGBoost). To improve the performance of the surrogate model, principal component analysis (PCA) and sliced inverse regression (SIR) methods are employed for the dimension reduction of output and input variables, respectively. Furthermore, the algorithm for river blockage identification is developed to search for the deposition ridges. To demonstrate the capability of the stochastic assessment framework, an example of the first Baige landslide in Tibet, China is simulated, and the affected region and deposition depths of the landslide are predicted to calculate the probability of river damming. The presented methodology provides a practical means for improving the landslide blocking river prediction and new insights for early warning and risk mitigation.

Analyzing sedimentation patterns in the Naumure Multipurpose Project (NMP) reservoir using 1D HEC-RAS modeling

Naumure Multipurpose Project (NMP) featuring a 169 m high Concrete Face Rock Filled Dam (CFRD) is the proposed reservoir project in the West Rapti River with an installed capacity of 218.34 MW. Most of the rivers in Nepal carry significant sediment loads that will consequently catalyze reservoir sedimentation. This phenomenon prevails as the primary factor in reducing reservoirs useful life, making ineffective for both flood control and hydroelectricity generation. Ultimately, such process of sedimentation has adverse impacts on projects economic feasibility and long-term sustainability. Therefore, the objective of this research was to examine the expected sediment deposition pattern in the NMP reservoir throughout its operational period by employing 1D HEC-RAS model to simulate the sedimentation process. The model was simulated for 10, 20, 30, 40 and 50 years. Yang’s equation as a sediment transport function, Active layer as a bed sorting method and Toffaleti as a fall velocity method were best suited for the river reach. The delta deposition was formed between 11 km and 22 km upstream of the dam region in the Jhimruk river, with the sediment deposition depth reaching peaks of about 23 m, 38 m, 39 m, 41 m and 49 m in 10, 20, 30, 40 and 50 years, respectively. Similarly, the delta deposition was formed between 13 km and 33 km upstream of dam region in the Madi river, with the sediment deposition depth reaching peaks of about 47 m, 62 m, 60 m, 68 m and 75 m in 10, 20, 30, 40 and 50 years respectively. Headcutting of delta deposition occurred between 20 and 30 year due to high flood during low stage of reservoir. Furthermore, the study revealed that about 6.22%, 11.61%, 15.94%, 22.96% and 25.65% of the storage capacity of NMP reservoir will be depleted in 10, 20, 30, 40 and 50 years respectively.

Characteristics of debris flow development in Daxilada watershed and its hazard analysis on Lexi Expressway

The occurrence of frequent debris flow catastrophes in the mountainous regions of southwest China has necessitated the inclusion of debris flow disaster analysis and prevention as an essential component in the planning and construction of mountainous roadways. Daxilada watershed is located in the south of Mabian Yi Zuzizhixian, Leshan City, Sichuan Province, and the proposed Leshan-Xichang Expressway (Lexi Expressway) will pass through the upper reaches of Daxilada watershed. It is essential to consider that the presence of debris flows within the Daxilada watershed could have detrimental effects on the construction and functionality of the proposed Luoshanxi Bridge. This study examined the Daxilada watershed as a case study and analyzed the factors contributing to debris flow formation in the area. This analysis was based on field investigations, remote sensing interpretation, and experimental analysis. Additionally, the study utilized the Massflow software to simulate debris flow movement. It integrated the simulation results to determine the potential hazards the Daxilada Gully debris flow posed to the line project. This study found that Daxilada Gully meets debris flow formation conditions. The simulation results demonstrated that during the debris flow activity, there would be a maximum deposition depth of 2.1 m in the proposed Engineering Agency, which may lead to siltation and blocking disaster of the line project. Concerning the parameters related to the debris flow with a frequency of one in a hundred years, in conjunction with the outcomes obtained from numerical simulation, it would provide the design basis of the cross-flow cross-section of the proposed bridge. In a quantitative analysis of the blockage situation in the gully, debris flow deposits have the potential to cause damage to the line project. Debris flow deposits block the gully, but the risk of blockage is small. The study results have specific reference values for the debris flow prevention and control project of Lexi Expressway and offer valuable insights for the prevention and mitigation of similar disasters in relative projects.

Influence of laser absorptivity of CuCr0.8 substrate surface state on the characteristics of laser directed energy deposition inconel 718 single track

An effective method for fabricating copper-nickel bimetallic liquid rocket engine thrust chambers involves utilizing laser directed energy deposition (LDED) technology. However, the state of the substrate surface significantly impacts the LDED process. This study investigates the effects of various substrate treatments on LDED single tracks, using CuCr0.8 high-copper alloy as the substrate and Inconel 718 as the deposition material. The treatments include polishing, sandblasting, laser etching, and cold spraying. Substrate surface roughness, laser absorptivity, molten pool morphology, and microstructure were characterized, and the mechanisms of laser absorptivity change and the different LDED processes were analyzed. The results indicate that the laser-etched surface exhibits the worst surface roughness (Ra 15.20 ± 0.60 μm), the highest laser absorptivity(80.70% at 1080 nm wavelength), the largest deposition width (947.33 ± 29.85 μm), and the maximum number of fine grains among the four substrates. Additionally, the cold-sprayed surface shows the largest deposition depth (237.33 ± 39.04 μm), the minimum number of fine grains and a higher laser absorptivity (66.20% at 1080 nm wavelength). In situ observations of molten pool formation and flow during LDED was conducted using an in situ high-speed high-resolution imaging system. The mechanisms underlying the alteration in laser absorptivity primarily involve the "trapped light" effect and modifications to the surface material. This research is significant as it provides foundational insights for laser processing of highly reflective materials, offering important theoretical and practical implications for engineering applications.

Tectonic controls on ore deposit exhumation and preservation: A case study of the Handan-Xingtai iron-skarn district

Despite the growing concern regarding post-mineralization thermo-tectonic processes in recent years, the relative roles in exhuming and preserving ore deposits remain highly controversial. This study presents new apatite fission track and (U-Th)/He data from the Xishimen iron skarn deposit in the Handan-Xingtai district, central North China Craton. Apatite fission track dating yielded central ages ranging from 88 ± 18 Ma to 125 ± 9 Ma, with mean confined track lengths varying between 11.9 ± 0.4 μm and 13.3 ± 0.2 μm. Integrated apatite (U-Th)/He dating provided ages of 42.5 ± 0.8 Ma to 48.1 ± 3.3 Ma. Our new data, combined with previous zircon U-Pb and potassium-bearing mineral 40Ar/39Ar ages, revealed three cooling episodes: very rapid cooling (100–140 °C/Ma) at ca. 130–120 Ma, a protracted slow cooling period (0.2–0.4 °C/Ma) at ca. 120–50 Ma, and moderate cooling (0.8–1.0 °C/Ma) since ca. 50 Ma. The initial rapid cooling phase was primarily attributed to post-magmatic thermal equilibration following the shallow emplacement of the Xishimen deposit. The subsequent cooling phases were controlled by uplift and exhumation processes. Our thermal models indicate an estimated total unroofing thickness of < 3 km, which is shallower than the emplacement depth of the ore deposit (3–5 km). This suggests significant potential for mineral exploration. Furthermore, a comprehensive review of preservation mechanisms for various ore deposits underscores the significant role of tectonics in both exhuming and preserving ore bodies.

Improvement of crushed returned concrete aggregates by wet carbonation

A considerable quantity of pre-mixed concrete is returned from construction sites which is usually dumped directly into pits. While this concrete may possess lower quality attributes due to inadequate compaction and curing, the crushed hardened concrete can be potentially used to produce recycled aggregates. Carbonation is regarded as a significant way of improvement of recycled concrete aggregates. This study investigated the effectiveness of wet carbonation method for the improvement of crushed returned concrete aggregates (CRCA) to reuse in concrete productions. Recycled concrete aggregate (RCA) obtained from crushing of old conventionally cast concrete was also subjected to the same treatment, and its properties were compared with those of CRCA to understand the improvement in each type of recycled aggregate. The effectiveness of wet carbonation was evaluated by the aqueous chemistry during carbonation, development of microstructure, depth of calcium carbonate deposition, the mineralogy, water absorption, and compressive strength for both treated and untreated CRCA and RCA for different carbonation durations. The results showed that, although the water absorptions of both uncarbonated and carbonated CRCA were higher than those of RCA, the rate of reduction of water absorption of CRCA after carbonation was higher than that in RCA. Due to the long exposure to open environment, CRCA showed less initial alkalinity and conductivity than RCA but at the end of carbonation, both pH and conductivity were almost same as those of RCA. Wet carbonation successfully produced well shaped calcite in both CRCA and RCA where the deposition depth of calcite was higher in CRCA than in RCA. Mineralogical analysis showed higher calcium carbonate formation in CRCA indicating its potential of sequestrating more CO2 than by RCA. The improvement of concrete compressive strength was more pronounced for CRCA, with a 28 % enhancement observed after 2 hours of carbonation, compared to an 18 % enhancement for RCA. These findings demonstrated that wet carbonation can be regarded as an effective strategy for enhancing CRCA.

Cynodon dactylon and Sediment Interaction in the Three Gorges Reservoir: Insights from a Three-Year Study

Sediment deposition is critical in maintaining riparian plant communities by providing essential nutrients and posing growth challenges. This study focuses on Cynodon dactylon, a dominant clonal species in the riparian zones of the Three Gorges Reservoir, and its interaction with sediment deposition over three years. Results indicated an average sediment deposition depth of 2.85 cm in the lower riparian regions. Observations revealed that C. dactylon coverage increased progressively at lower elevations despite its dominance diminishing with rising elevation levels. Additionally, positive linear correlations between C. dactylon coverage and sediment deposition depths were identified during flood periods, underscoring the species’ role in enhancing sediment deposition. These findings suggest that C. dactylon plays a significant role in sediment accumulation, which may bolster its growth and survival prospects during subsequent growing cycles. The study highlights the importance of riparian vegetation, mainly perennial clonal species like C. dactylon, in promoting sediment accumulation and contributing to the stability and functionality of riparian ecosystems.