Dissolution Precipitation Wave Structure of Hydrothermal Ore Zoning

Hydrothermal ore zoning is a transport-reaction problem in which infiltration is the principal Prcness of transport and dissolution/Precipitation is the Principal process of chemical reactions.Neglecting diffusion and ion exchange/adsorption would not affect the basic attributes of hydrothermal ore zoning. Hydrothermal ore zoning belongs essentially to infiltration metasomatic zoning, it results from the formation and propagation of dissolution/precipitation waves through Permeable media. The authors apply the theory of coupled infiltration and dissolution/precipitation reactions in Physicochemical hydrodynamics to studying the structural characteristics of dissolution/precipitation waves, and apply furthermore the coherence principle in dynamic theory of multicomponent coupled systems to revealing the dynamic mechanisms of their formation. The results of investigation verify and develop . C. 's theory of infiltration metasomatic zoning,on the one hand, raising it from the qualitative, equilibrium thermodynamic basis to the quantitative dynamic level;on the other hand, and more importantly, applying theories of Physicochemical hydrodynamics and dynamics of multicomponent coupled systems to bringing to light the dynamic mechanisms of formation of the structure of hydrothermal ore zoning, and advancing a theory of hydrothermal ore zoning, putting forward new ideas on the nature of the problem of hydrothermal ore zoning, the essence of hydrothermal ore zoning and the structural characteristics and mechanisms of formation of hydrothermal ore zoning.

An experimental study on dynamic coupling process of alkaline feldspar dissolution and secondary mineral precipitation

In order to clarify the dynamic process of feldspar dissolution-precipitation and explore the formation mechanism of secondary porosity,six batch reactor experiments were conducted at 200℃and pH=7 measured at room temperature.Temporal evolution of fluid chemistry was analyzed with an inductively coupled plasma optical emission spectrometer(ICP-OES).Solid reaction products were retrieved from six batch experiments terminated after 36,180,276,415,766 and 1008 h.Scanning electron microscopy(SEM)revealed dissolution features and significant secondary mineral adhered on the feldspar surface.The process of feldspar dissolution-precipitation proceeded slowly and full equilibrium was not achieved after 1008 h.Saturation indices suggested that the albite and K-feldspar dissolution occurred throughout the experiments.The average dissolution rates for albite and K-feldspar were 2.28×10^-10 and 8.51×10^-11 mol m^-2 s^-1,respectively.Based on the experimental data,the reaction process of alkaline feldspar was simulated and the secondary porosity had increased 0.3%after the experiment.

Physical Simulation and Experimental Examination of ε-Cu Particles Dissolution Evolution During Welding of Copper Precipitation Strengthening Steel

The kinetics of ε-Cu particles dissolution in the matrix during welding of a copper-precipitation strengthening steel was determined by a combination of GleebleTM physical simulation, TEM examination and hardness meas urement. The ε-Cu particles underwent a coarsening and part dissolution and then complete dissolution reaction as the peak temperature increased from 750 to 1 000℃, which resulted in the decrease in the number density of ε-Cu particles and hardness in the heat affected zone （HAZ）. The results can be used to understand the evolution of this transformation and a softening behavior of the HAZ during welding of this type of steel.

Timescales of interface-coupled dissolution-precipitation reactions oncarbonates

In the Earth's upper crust, where aqueous fluids can circulate freely, most mineral transformations are controlled by the coupling between the dissolution of a mineral that releases chemical species into the fluid and precipitation of new minerals that contain some of the released species in their crystal structure, the coupled process being driven by a reduction of the total free-energy of the system. Such coupled dissolution-precipitation processes occur at the fluid-mineral interface where the chemical gradients are highest and heterogeneous nucleation can be promoted, therefore controlling the growth kinetics of the new minerals. Time-lapse nanoscale imaging using Atomic Force Microscopy(AFM) can monitor the whole coupled process under in situ conditions and allow identifying the time scales involved and the controlling parameters. We have performed a series of experiments on carbonate minerals(calcite, siderite, dolomite and magnesite) where dissolution of the carbonate and precipitation of a new mineral was imaged and followed through time. In the presence of various species in the reacting fluid(e. g. antimony, selenium, arsenic, phosphate), the calcium released during calcite dissolution binds with these species to form new minerals that sequester these hazardous species in the form of a stable solid phase. For siderite, the coupling involves the release of Fe^(2+) ions that subsequently become oxidized and then precipitate in the form of FeIIIoxyhydroxides. For dolomite and magnesite,dissolution in the presence of pure water(undersaturated with any possible phase) results in the immediate precipitation of hydrated Mg-carbonate phases. In all these systems, dissolution and precipitation are coupled and occur directly in a boundary layer at the carbonate surface. Scaling arguments demonstrate that the thickness of this boundary layer is controlled by the rate of carbonate dissolution,the equilibrium concentration of the precipitates and the kinetics of diffusion of species in a boundary layer. From these parameters a characteristic time scale and a characteristic length scale of the boundary layer can be derived. This boundary layer grows with time and never reaches a steady state thickness as long as dissolution of the carbonate is faster than precipitation of the new mineral. At ambient temperature, the surface reactions of these dissolving carbonates occur on time-scales of the order of seconds to minutes, indicating the rapid surface rearrangement of carbonates in the presence of aqueous fluids. As a consequence, many carbonate-fluid reactions in low temperature environments are controlled by local thermodynamic equilibria rather than by the global equilibrium in the whole system.

In situ differential scanning calorimetry analysis of dissolution and precipitation kinetics in Mg-Y-RE alloy WE43

Further development of our differential scanning calorimetry(DSC)method for the analysis of solid-solid phase transformations now also allows for its application in the kinetic analysis of age hardening in Mg alloys.As a result,the state-of-the-art for DSC on Mg alloys has been improved with respect to the accessible temperature range,zero-level accuracy and dynamic range.DSC analysis was performed on the example of Mg wrought alloy WE43.Heating DSC experiments on the initial condition T4 and even direct continuous cooling DSC analysis on the kinetics of quench induced precipitation during cooling from solution treatment were possible,covering a dynamic range of 0.01-3 K/s.The DSC findings are discussed with respect to literature knowledge and scanning electron microscopy analysis of the defined heat treatment states.

Discontinuous Precipitation and Dissolution in Cu-4, 6 at% In Alloy under the Effect of Plastic Deformation and the Temperature

The study of the discontinuous precipitation reaction and the lamellar precipitate dissolution in the alloy Cu-In system provoked a considerable benefit and has been the subject of many theoretical and experimental investigations. The aim of this work is to make the evidence on the one hand the effect of the plastic deformation on the mechanism of the discontinuous precipitation reaction such as nucleation, growth and lamellar coarsening and in other hand the effect of temperature on the characteristics and front behavior movement of the opposite reaction (discontinuous dissolution). Different techniques of analysis have been used in this respect such as the optical microscopy, the differential thermal analysis and the microhardness Vickers. The obtained results confirm various works achieved in this field.

Discontinuous Precipitation and Dissolution under the Influence of the Plastic Strain and Temperature in Al-15 at.%Zn and Al-30 at.%Zn Alloys

The discontinuous precipitation and dissolution in the alloy Al-Zn system has been the subject of many theoretical and experimental investigations that have contributed to the understanding of the different mechanisms which control them. However, many questions remain unanswered because of the complexity of the constituted phases which are affected by the speed of the quenched, deformation, the temperature of homogenization and ageing effect. The purpose of this work is to clarify the effect of temperature and deformation on the mechanisms of these two reactions during ageing of Al-15 at.% Zn and Al-30 at.% Zn alloy. The techniques of analysis used in this respect are the optical microscopy, the X-ray diffraction and the hardness Vickers.

Dissolution and reprecipitation of 14H-LPSO structure accompanied by dynamic recrystallization in hot-extruded Mg_(89)Y_(4)Zn_(2)Li_(5) alloy

We investigate the variation induced in long-period stacking ordered(LPSO)structures,dynamic recrystallization(DRX),and mechanical performance of hot-extruded Mg89Y4Zn2Li5 alloys fabricated at different extrusion speeds(Ve=0.4,0.8,1.0,1.2 mm/s)and die angles(α=30°,60°,90°)under 400℃,the dissolution and reprecipitation of 14H LPSO structure accompanied by DRX process are then clarified in detail.Upon all extrusion conditions,the block 18R LPSO structures elongate in the extrusion direction,while the lamellar 14H LPSO structures dissolve under the deformation strain.In addition,due to discontinuous and continuous DRX mechanisms,all hot-extruded alloys have a full DRX microstructure consisting of equiaxed recrystallized grains,but the DRX grain size reduces when both extrusion speed and die angle decrease.Note that,in the interior of DRX grains,thin LPSO lamellae mixing 14H,18R and 24R structures nucleate and dynamically precipitate due to the dissolution of the original lamellar 14H LPSO structures.Furthermore,the hot-extruded Mg_(89)Y_(4)Zn_(2)Li_(5)alloy becomes stronger as decreasing of the extrusion speed and die angle,whereas the ductility remains nearly constant.Finally,the hotextruded Mg_(89)Y_(4)Zn_(2)Li_(5)alloy achieves an excellent strength-ductility balance at a relatively low extrusion speed(0.4 mm/s)and small die angle(30°)mainly due to the elongated 18R LPSO structure,fine and full DRX microstructure,thin mixed LPSO precipitates in the DRX grains,twins and dislocations.

THEORETICAL AND EXPERIMENTAL RESULTS ON THE KINETICS OF CALCITE DISSOLUTION AND PRECIPITATION

INTRODUCTION Dissolution and precipitation of carbonates plays an important role in nature, such as in the chemistry of seawater, the sedimentation of carbonate at the seafloor, the geochemical evolution of freshwater aquifers and last but not least, most spectacular, the evolution of karst landscapes. To provide a deeper understanding to all these processes knowledge is required

Effect of precipitation/re-dissolution processes from the supersaturated solution on the intestinal absorption of poorly water-soluble drugs

As one of the possible technologies to improve the oral absorption of poorly water-soluble drugs, supersaturable formulation, which enables to dissolve the drug to the higher concentration than their equilibrium solubility, is now attracting the attention (1)This include salt-formation, soliddispersion, co-crystallization or the use of amorphous form.Since supersaturation is a thermodynamically metastable state,supersaturated solution has a high potential to precipitate. Some pharmaceutical excipients.

Heterointerface Engineering-Induced Oxygen Defects for the Manganese Dissolution Inhibition in Aqueous Zinc Ion Batteries

Manganese-based material is a prospective cathode material for aqueous zinc ion batteries(ZIBs)by virtue of its high theoretical capacity,high operating voltage,and low price.However,the manganese dissolution during the electrochemical reaction causes its electrochemical cycling stability to be undesirable.In this work,heterointerface engineering-induced oxygen defects are introduced into heterostructure MnO_(2)(δa-MnO_(2))by in situ electrochemical activation to inhibit manganese dissolution for aqueous zinc ion batteries.Meanwhile,the heterointerface between the disordered amorphous and the crystalline MnO_(2)ofδa-MnO_(2)is decisive for the formation of oxygen defects.And the experimental results indicate that the manganese dissolution ofδa-MnO_(2)is considerably inhibited during the charge/discharge cycle.Theoretical analysis indicates that the oxygen defect regulates the electronic and band structure and the Mn-O bonding state of the electrode material,thereby promoting electron transport kinetics as well as inhibiting Mn dissolution.Consequently,the capacity ofδa-MnO_(2)does not degrade after 100 cycles at a current density of 0.5 Ag^(-1)and also 91%capacity retention after 500cycles at 1 Ag^(-1).This study provides a promising insight into the development of high-performance manganese-based cathode materials through a facile and low-cost strategy.

Characteristics and control factors of feldspar dissolution in gravity flow sandstone of Chang 7 Member,Triassic Yanchang Formation,Ordos Basin,NW China

To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7^(th) member of Triassic Yanchang Formation(Chang 7 Member)in the Ordos Basin,thin sections,scanning electron microscopy,energy spectrum analysis,X-ray diffraction whole rock analysis,and dissolution experiments are employed in this study to investigate the characteristics and control factors of feldspar dissolution pores.The results show that:(1)Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area:secondary overgrowth of feldspar,replacement by clay and calcite,and dissolution of detrital feldspar.(2)The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid,and is further affected by the type of feldspar,the degree of early feldspar alteration,and the buffering effect of mica debris on organic acid.(3)Feldspars have varying degrees of dissolution.Potassium feldspar is more susceptible to dissolution than plagioclase.Among potassium feldspar,orthoclase is more soluble than microcline,and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar.(4)The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar.Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar.(5)Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content,and they improve the reservoir physical properties,while in areas with high mica content,the number of feldspar dissolution pores decreases significantly.

Effect of drying-wetting cycles on pore characteristics and mechanical properties of enzyme-induced carbonate precipitation-reinforced sea sand

Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored yet.This study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W cycles.The uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles.The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles.The proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W cycles.The micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched.The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W cycles.Overall,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.

Spatio-Temporal Characteristics of Heavy Precipitation Forecasts from ECMWF in Eastern China

This study examines the spatio-temporal characteristics of heavy precipitation forecasts in eastern China from the European Centre for Medium-Range Weather Forecasts(ECMWF) using the time-domain version of the Method for Object-based Diagnostic Evaluation(MODE-TD). A total of 23 heavy rainfall cases occurring between 2018 and 2021 are selected for analysis. Using Typhoon “Rumbia” as a case study, the paper illustrates how the MODE-TD method assesses the overall simulation capability of models for the life history of precipitation systems. The results of multiple tests with different parameter configurations reveal that the model underestimates the number of objects’ forecasted precipitation tracks, particularly at smaller radii. Additionally, the analysis based on centroid offset and area ratio tests for different classified precipitation objects indicates that the model performs better in predicting large-area, fast-moving, and longlifespan precipitation objects. Conversely, it tends to have less accurate predictions for small-area, slow-moving, and shortlifespan precipitation objects. In terms of temporal characteristics, the model overestimates the forecasted movement speed for precipitation objects with small-area, slow movement, or both long and short lifespans while underestimating it for precipitation with fast movement. In terms of temporal characteristics, the model tends to overestimate the forecasted movement speed for precipitation objects with small-area, slow movement, or both long and short lifespans while underestimating it for precipitation with fast movement. Overall, the model provides more accurate predictions for the duration and dissipation of precipitation objects with large-area or long-lifespan(such as typhoon precipitation) while having large prediction errors for precipitation objects with small-area or short-lifespan. Furthermore, the model’s simulation results regarding the generation of precipitation objects show that it performs relatively well in simulating the generation of large-area and fast-moving precipitation objects. However, there are significant differences in the forecasted generation of small-area and slow-moving precipitation objects after 9 hours.

Progress on Transition Metal Ions Dissolution Suppression Strategies in Prussian Blue Analogs for Aqueous Sodium-/Potassium-Ion Batteries

Aqueous sodium-ion batteries(ASIBs)and aqueous potassium-ion batteries(APIBs)present significant potential for large-scale energy storage due to their cost-effectiveness,safety,and environmental compatibility.Nonetheless,the intricate energy storage mechanisms in aqueous electrolytes place stringent require-ments on the host materials.Prussian blue analogs(PBAs),with their open three-dimensional framework and facile synthesis,stand out as leading candidates for aqueous energy storage.However,PBAs possess a swift capacity fade and limited cycle longevity,for their structural integrity is compromised by the pronounced dis-solution of transition metal(TM)ions in the aqueous milieu.This manuscript provides an exhaustive review of the recent advancements concerning PBAs in ASIBs and APIBs.The dissolution mechanisms of TM ions in PBAs,informed by their structural attributes and redox processes,are thoroughly examined.Moreover,this study delves into innovative design tactics to alleviate the dissolution issue of TM ions.In conclusion,the paper consolidates various strategies for suppressing the dissolution of TM ions in PBAs and posits avenues for prospective exploration of high-safety aqueous sodium-/potassium-ion batteries.

Future changes in precipitation and water availability over the Tibetan Plateau projected by CMIP6 models constrained by climate sensitivity

Precipitation projections over the Tibetan Plateau(TP)show diversity among existing studies,partly due to model uncertainty.How to develop a reliable projection remains inconclusive.Here,based on the IPCC AR6–assessed likely range of equilibrium climate sensitivity(ECS)and the climatological precipitation performance,the authors constrain the CMIP6(phase 6 of the Coupled Model Intercomparison Project)model projection of summer precipitation and water availability over the TP.The best estimates of precipitation changes are 0.24,0.25,and 0.45 mm d^(−1)(5.9%,6.1%,and 11.2%)under the Shared Socioeconomic Pathway(SSP)scenarios of SSP1–2.6,SSP2–4.5,and SSP5–8.5 from 2050–2099 relative to 1965–2014,respectively.The corresponding constrained projections of water availability measured by precipitation minus evaporation(P–E)are 0.10,0.09,and 0.22 mm d^(−1)(5.7%,4.9%,and 13.2%),respectively.The increase of precipitation and P–E projected by the high-ECS models,whose ECS values are higher than the upper limit of the likely range,are about 1.7 times larger than those estimated by constrained projections.Spatially,there is a larger increase in precipitation and P–E over the eastern TP,while the western part shows a relatively weak difference in precipitation and a drier trend in P–E.The wetter TP projected by the high-ECS models resulted from both an approximately 1.2–1.4 times stronger hydrological sensitivity and additional warming of 0.6℃–1.2℃ under all three scenarios during 2050–2099.This study emphasizes that selecting climate models with climate sensitivity within the likely range is crucial to reducing the uncertainty in the projection of TP precipitation and water availability changes.

Assessment of Wet Season Precipitation in the Central United States by the Regional Climate Simulation of the WRFG Member in NARCCAP and Its Relationship with Large-Scale Circulation Biases

Assessment of past-climate simulations of regional climate models(RCMs)is important for understanding the reliability of RCMs when used to project future regional climate.Here,we assess the performance and discuss possible causes of biases in a WRF-based RCM with a grid spacing of 50 km,named WRFG,from the North American Regional Climate Change Assessment Program(NARCCAP)in simulating wet season precipitation over the Central United States for a period when observational data are available.The RCM reproduces key features of the precipitation distribution characteristics during late spring to early summer,although it tends to underestimate the magnitude of precipitation.This dry bias is partially due to the model’s lack of skill in simulating nocturnal precipitation related to the lack of eastward propagating convective systems in the simulation.Inaccuracy in reproducing large-scale circulation and environmental conditions is another contributing factor.The too weak simulated pressure gradient between the Rocky Mountains and the Gulf of Mexico results in weaker southerly winds in between,leading to a reduction of warm moist air transport from the Gulf to the Central Great Plains.The simulated low-level horizontal convergence fields are less favorable for upward motion than in the NARR and hence,for the development of moist convection as well.Therefore,a careful examination of an RCM’s deficiencies and the identification of the source of errors are important when using the RCM to project precipitation changes in future climate scenarios.

Impacts of Future Changes in Heavy Precipitation and Extreme Drought on the Economy over South China and Indochina

Heavy precipitation and extreme drought have caused severe economic losses over South China and Indochina(INCSC)in recent decades.Given the areas with large gross domestic product(GDP)in the INCSC region are distributed along the coastline and greatly affected by global warming,understanding the possible economic impacts induced by future changes in the maximum consecutive 5-day precipitation(RX5day)and the maximum consecutive dry days(CDD)is critical for adaptation planning in this region.Based on the latest data released by phase 6 of the Coupled Model Intercomparison Project(CMIP6),future projections of precipitation extremes with bias correction and their impacts on GDP over the INCSC region under the fossil-fueled development Shared Socioeconomic Pathway(SSP5-8.5)are investigated.Results indicate that RX5day will intensify robustly throughout the INCSC region,while CDD will lengthen in most regions under global warming.The changes in climate consistently dominate the effect on GDP over the INCSC region,rather than the change of GDP.If only considering the effect of climate change on GDP,the changes in precipitation extremes bring a larger impact on the economy in the future to the provinces of Hunan,Jiangxi,Fujian,Guangdong,and Hainan in South China,as well as the Malay Peninsula and southern Cambodia in Indochina.Thus,timely regional adaptation strategies are urgent for these regions.Moreover,from the sub-regional average viewpoint,over two thirds of CMIP6 models agree that maintaining a lower global warming level will reduce the economic impacts from heavy precipitation over the INCSC region.

Time-lagged Effects of the Spring Atmospheric Heat Source over the Tibetan Plateau on Summer Precipitation in Northeast China during 1961–2020:Role of Soil Moisture

The spring atmospheric heat source(AHS)over the Tibetan Plateau(TP)has been suggested to affect the Asian summer monsoon and summer precipitation over South China.However,its influence on the summer precipitation in Northeast China(NEC)remains unknown.The connection between spring TP AHS and subsequent summer precipitation over NEC from 1961 to 2020 is analyzed in this study.Results illustrate that stronger spring TP AHS can enhance subsequent summer NEC precipitation,and higher soil moisture in the Yellow River Valley-North China region(YRVNC)acts as a bridge.During spring,the strong TP AHS could strengthen the transportation of water vapor to East China and lead to excessive rainfall in the YRVNC.Thus,soil moisture increases,which regulates local thermal conditions by decreasing local surface skin temperature and sensible heat.Owing to the memory of soil moisture,the lower spring sensible heat over the YRVNC can last until mid-summer,decrease the land–sea thermal contrast,and weaken the southerly winds over the East Asia–western Pacific region and convective activities over the South China Sea and tropical western Pacific.This modulates the East Asia–Pacific teleconnection pattern,which leads to a cyclonic anomaly and excessive summer precipitation over NEC.

Differences in spring precipitation over southern China associated with multiyear La Ni?a events

Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Ni?a events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone(WNPC), which can in turn be attributed to the different sea surface temperature anomaly(SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance.SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Ni?a events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.