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This study investigated the hydrodynamics of highly viscous liquid under vertical acoustic vibration, and examined the effects of vibration parameters and filling ratio on the strain rate, stretching index, and convective intensity of high‐viscosity liquid. A numerical simulation model of gas–liquid flows was developed using computational fluid dynamics method and validated through experiment. Under acoustic vibration, the high‐viscosity liquid predominantly experienced extensional and shearing flows. Significant deformation of the high‐viscosity liquid was observed near the interface between gas and liquid. Increasing the amplitude or frequency of acoustic vibration, selecting a combination of low‐frequency and high amplitude under equal acceleration conditions, as well as appropriately reducing the filling ratio can enhance the stretching and shearing effects on the liquid, and improve the strength of convection. The findings also established a predictive relationship between amplitude and frequency, enabling the determination of optimal mixing conditions. [ABSTRACT FROM AUTHOR]

The Augmitto-Bouzan deposit is a 12 km long segment of the Larder Lake-Cadillac Deformation Zone (LLCDz) south of Rouyn-Noranda (Québec, Canada) that is characterized by an uneven gold distribution hosted in quartz-carbonate ± tourmaline veins within Piché Group ultramafic rocks. This study compares the fluid flow conditions between the variable gold-endowed sectors to identify deposit-scale processes responsible for gold endowment. Stable isotopes indicate that quartz and tourmaline have equilibrium temperatures (228–⁠420 °C) that likely define a high vertical thermal gradient (~ 30 °C/100 m) along the LLCDz. Covariation between temperature and computed δ18OH2O and δDH2O is interpreted to result from mixing between a high temperature (> 420 °C), high δ18O (> 10.8‰), and low δD (< –29‰) deep-seated metamorphic fluid, and a low temperature (< 230 °C), low δ18O (< 4‰) and high δD (~ 0‰) upper crustal pore fluid. Local upwelling of auriferous deep-seated fluid, shown by interpolation of δ18OH2O in the gold-endowed Augmitto-Cinderella and Astoria segments, was likely focused along higher permeability deformation-related pathways. Sectors of low gold endowment have lower δ18OH2O and fluid/rock ratios, likely reflecting a larger proportion of upper crustal fluid and differences in fluid-flow behavior. Modeling of fluid flow shows that this is due to 1) weaker metamorphic fluid flux in the thinner band of Piché Group rocks and 2) more porous volcanic rocks north of the LLCDz, drawing more pore fluid into the fault. We suggest that most of the variation of gold endowment is related to variations in advection of auriferous metamorphic fluid along the segment, whereby a weaker metamorphic fluid flux or increased admixture of upper crustal fluids decrease the gold potential along the LLCDz. [ABSTRACT FROM AUTHOR]

We study the Rayleigh--Taylor instability for two miscible, incompressible, inviscid fluids. Scale invariant estimates for the size of the mixing zone and coarsening of internal structures in the fully nonlinear regime are established following techniques introduced for the Saffman--Taylor instability in [G. Menon and F. Otto, Comm. Math. Phys., 257 (2005), pp. 303--317]. These bounds provide optimal scaling laws and reveal the strong role of dissipation in slowing down mixing. [ABSTRACT FROM AUTHOR]

Metal stable isotopes (e.g., Zn, Cd, and Cu) have been used to track metal sources in different types of hydrothermal systems. However, metal isotopic variations in sulphides could be triggered by various factors such as mineral precipitation and fluid mixing. Thus, tracking the metal sources of hydrothermal systems is still a big challenge for metal isotopes. In this study, we investigated the Cd isotopic systematics of sphalerite from the Nayongzhi Zn–Pb deposit, which is a Mississippi Valley‐type (MVT) deposit in the Sichuan–Yunnan–Guizhou mineralization province (SYGMP). We reinterpreted the published S isotope data for the SYGMP and found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. As such, a model that involves mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction (TSR) can explain the ore formation in the Nayongzhi deposit. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing, and thus the Cd isotopic variations of sphalerite were inherited from the source rocks. The large range of Zn/Cd ratios and uniform Cd isotopic compositions of the sulphides are similar to those of igneous rocks but different from those of sedimentary rocks, indicating that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Our results reaffirm that metal stable isotopes, particularly Cd isotope compositions of sphalerite, are powerful geochemical tracers for investigating the formation mechanisms of ore deposits. Plain Language Summary: Metal stable isotopes, particularly Cd isotopes, have been widely used in investigating the metal sources, fluid evolution, and formation mechanisms of ore deposits. Here, we studied the Cd isotopic compositions of sphalerite from the Nayongzhi Zn–Pb deposit in the Sichuan–Yunnan–Guizhou mineralization province. The range of δ114/110CdNIST‐3108 value is smaller in the Nayongzhi deposit (−0.16–0.21‰), but the published S isotopic composition has significant variation (11.8–33.0‰). We found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. Thus, a mineralization model of the Nayongzhi deposit has been proposed, which involves the mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing. Therefore, the Cd isotopic variations of sphalerite were inherited from the source rocks. Combining the Zn/Cd ratios and Cd isotopic composition characteristics of the sulphides, igneous rocks, and sedimentary rocks, it is indicated that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Key Points: S isotopic variations caused by Rayleigh fractionation between sulphide and reduced S; Cd isotopic variations inherited from source rocksZn/Cd ratios and Cd isotopic compositions reveal that Zn and Cd were dominantly derived from basement rocksThe Nayongzhi deposit was formed by mixing between metal‐rich and reduced sulfur ore‐forming fluids [ABSTRACT FROM AUTHOR]

[Display omitted] The coalescence of droplets with liquid–gas interfaces of different surface tensions is common in nature and industrial applications, where the Marangoni-driven film spreading is an essential process. Unlike immiscible fluids governed by triple contact line dynamics, the mixing between two miscible fluids strongly couples with the film spreading process, which are expected to manifest distinct power-law relations for the temporal increase in the film radius. We experimentally investigate the Marangoni-driven film spreading phenomenon for a droplet with lower surface tension dropping onto a miscible, thin liquid layer. The temporal growth of the film radius was detected by using a novel deep convolutional neural network, the U2-net method. Scaling analysis was performed to interpret the spreading dynamics of the film. We find that the film radius exhibits a three-stage power-law relation over time, with the exponent varying from 1/2 to 1/8, and back to 1/2. The diffusion-affected Marangoni stresses in these three stages were derived, and two estimations of viscous stress were considered. Through estimating and balancing the viscous stress with the Marangoni stress, the three-stage power-law relation was derived and validated. [ABSTRACT FROM AUTHOR]

The Fuli Pb-Zn deposit is situated at the southwestern margin of the Yangtze Block in Yunnan. The deposit, which is hosted in the Permian Yangxin Formation dolomite, is a recent discovery. Our study indicates a significant presence of fluid inclusions in sphalerite from the Fuli Pb-Zn deposit, with fewer inclusions observed in dolomite and calcite. We conducted comprehensive petrographic, microthermometric, and laser Raman analyses on the inclusions within sphalerite and dolomite. Additionally, six samples of dolomite from the mineralization period were selected for H-O isotope analysis. The results of our study reveal the characteristics of ore-forming fluids and explore the mechanisms of ore formation. The study results indicate that the Fuli Pb-Zn deposit is a low- to medium-temperature hydrothermal deposit with fluid inclusions mainly composed of two-phase gas-liquid inclusions. Salinity and homogenization temperature analyses affirmed that there are two types of fluids present, one with low salinity and the other with high salinity. Laser Raman tests demonstrated the presence of CH4, N2, and CO2 in the gas phase of the inclusions. Microthermometric analyses indicated that the sphalerite ore-forming fluids consist of a multicomponent system of Mg2+ and Ca2+ enriched fluids. The features of the ore-forming fluids in the Fuli deposit arise from a blend of high-temperature, low-salinity metamorphic fluids and low-temperature, high-salinity basin brines. The basin brines in question have the potential to emanate from the Youjiang Basin. The formation of the ore is ascribed to the TSR and the mixing of fluids. The combination of these processes provided the requisite materials (SO42−), catalysts (Mg2+), and reducing agents (organic matter, CH4, and H2S) required to initiate the thermochemical sulfate reduction (TSR). As the TSR proceeded, it caused a shift in the pH of the fluids, thus promoting the precipitation of metal sulfides. [ABSTRACT FROM AUTHOR]

Abstract The large Weilasituo Sn-polymetallic deposit is a recent exploration discovery in the southern Great Xing’an Range, northeast China. The ore cluster area shows horizontal mineralization zoning, from the inner granite body outward, consisting of high-T Sn–W–Li mineralization, middle-T Cu–Zn mineralization and peripheral low-T Pb–Zn–Ag mineralization. However, the intrinsic genetic relationship between Sn-W-Li mineralization and peripheral vein-type Pb–Zn–Ag–Cu mineralization, the formation mechanism and the deep geological background are still insufficiently understood. Here, we use fluid inclusions, trace elements concentrations in quartz and sphalerite, and H–O isotope studies to determine the genetic mechanism and establish a metallogenic model. Fluid inclusion microthermometry and Laser Raman spectroscopic analysis results demonstrates that the aqueous ore-forming fluids evolved from low-medium salinity, medium–high temperature to low salinity, low-medium temperature fluids. Laser Raman spectroscopic analysis shows that CH4 is ubiquitous in fluid inclusions of all ore stages. Early ore fluids have δ18OH2O (v–SMOW) values from + 5.5 to + 6.2‰ and δD values of approximately − 67‰, concordant with a magmatic origin. However, the late ore fluids shifted toward lower δ18OH2O (v–SMOW) (as low as 0.3‰) and δD values (~ − 136‰), suggesting mixing between external fluids derived from the wall rocks and a contribution from meteoric water. Ti-in-quartz thermometry indicates a magmatic crystallization temperature of around 700 °C at a pressure of 1.5 kbar for the magmatic ore stage. Cathodoluminescence (CL) imaging and trace element analysis of quartz from a hydrothermal vug highlight at least three growth episodes that relate to different fluid pulses; each episode begins with CL-bright, Al-Li-rich quartz, and ends with CL-dark quartz with low Al and Li contents. Quartz from Episode 1 formed from early Sn-(Zn)-rich fluids which were likely derived from the quartz porphyry. Quartz from episodes 2 and 3 formed from Zn-(Sn)-Cu-rich fluid. The early magmatic fluid is characterized by low fS2. The SO2 produced by magma degassing reacted with heated water to form SO4 2−, causing the shift from low fS2 to high fS2. The SO4 2− generated was converted to S2– by mixing with CH4-rich, Fe and Zn-bearing external fluid which led to late-stage alteration and dissolution of micas in vein walls, thus promoting crystallization of pyrrhotite, Fe-rich sphalerite and chalcopyrite and inhibiting the precipitation of anhydrite. This study shows that ore formation encompassed multiple episodes involving steadily evolved fluids, and that the addition of external fluids plays an important role in the formation of the later Cu–Zn and Ag–Pb–Zn mineralization in the Weilasituo ore district.

Abstract Metal stable isotopes (e.g., Zn, Cd, and Cu) have been used to track metal sources in different types of hydrothermal systems. However, metal isotopic variations in sulphides could be triggered by various factors such as mineral precipitation and fluid mixing. Thus, tracking the metal sources of hydrothermal systems is still a big challenge for metal isotopes. In this study, we investigated the Cd isotopic systematics of sphalerite from the Nayongzhi Zn–Pb deposit, which is a Mississippi Valley‐type (MVT) deposit in the Sichuan–Yunnan–Guizhou mineralization province (SYGMP). We reinterpreted the published S isotope data for the SYGMP and found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. As such, a model that involves mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction (TSR) can explain the ore formation in the Nayongzhi deposit. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing, and thus the Cd isotopic variations of sphalerite were inherited from the source rocks. The large range of Zn/Cd ratios and uniform Cd isotopic compositions of the sulphides are similar to those of igneous rocks but different from those of sedimentary rocks, indicating that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Our results reaffirm that metal stable isotopes, particularly Cd isotope compositions of sphalerite, are powerful geochemical tracers for investigating the formation mechanisms of ore deposits.

Carbonate‐brucite chimneys are a characteristic of low‐ to moderate‐temperature, ultramafic‐hosted alkaline hydrothermal systems, such as the Lost City hydrothermal field located on the Atlantis Massif at 30°N near the Mid‐Atlantic Ridge. These chimneys form as a result of mixing between warm, serpentinization‐derived vent fluids and cold seawater. Previous work has documented the evolution in mineralogy and geochemistry associated with the aging of the chimneys as hydrothermal activity wanes. However, little is known about spatial heterogeneities within and among actively venting chimneys. New mineralogical and geochemical data (87Sr/86Sr and stable C, O, and clumped isotopes) indicate that the brucite and calcite precipitate at elevated temperatures in vent fluid‐dominated domains in the interior of chimneys. Exterior zones dominated by seawater are brucite‐poor and aragonite is the main carbonate mineral. Carbonates record mostly out of equilibrium oxygen and clumped isotope signatures due to rapid precipitation upon vent fluid‐seawater mixing. On the other hand, the carbonates precipitate closer to carbon isotope equilibrium, with dissolved inorganic carbon in seawater as the dominant carbon source and have δ13C values within the range of marine carbonates. Our data suggest that calcite is a primary mineral in the active hydrothermal chimneys and does not exclusively form as a replacement of aragonite during later alteration with seawater. Elevated formation temperatures and lower 87Sr/86Sr relative to aragonite in the same sample suggest that calcite may be the first carbonate mineral to precipitate. Plain Language Summary: At the Lost City hydrothermal field, warm alkaline fluids are discharging out of uplifted mantle rocks. When vent fluids mix with seawater at the seafloor, carbonate and brucite minerals form spectacular towers up to 60 m high. Systems like Lost City are important because the reaction between water and rocks provides carbon and energy sources for microbial life. However, we still do not fully understand what controls the mineralogy and geochemistry of the Lost City hydrothermal chimneys. In this paper, we suggest that the extent of mixing between the hydrothermal fluids and seawater influences the mineralogy and geochemistry of the chimneys. Calcite, which was previously thought to form only during alteration of aragonite by seawater, can also form during seawater‐hydrothermal fluid mixing. Both calcite and brucite form in the interior of the chimneys where vent fluid is more dominant. Aragonite, on the other hand, forms in the exterior of the structures from seawater‐rich fluids. Lastly, because minerals precipitate rapidly during fluid mixing, the stable isotope geochemistry of the carbonates mostly records the composition and temperature of seawater and not the mixed fluid. Thus, care should be exercised in interpreting mineral geochemical data from similar systems. Key Points: The mineralogy and geochemistry of Lost City chimneys are controlled by the extent of mixing between hydrothermal fluids and seawaterBrucite and calcite precipitate in vent fluid dominated zones while aragonite forms in the exterior of the structures in seawater‐rich zonesCarbonates precipitate in isotopic disequilibrium and record the O and C stable isotope composition of seawater dissolved inorganic carbon [ABSTRACT FROM AUTHOR]

The effectiveness of fluid mixing in a reactor is crucial for the success of chemical reactions. In this paper, we propose a novel multi-phase flow reactor for continuous flow technology and employ computational fluid dynamics (CFD) to optimize the mixing efficiency for a liquid-liquid system. The uniformity index and phase boundary area per unit volume (custom parameters representing mixing efficiency) are used to characterize the mixing effects of the fluid. We investigate the impact of stirring paddle structure, rotation speed, and feed flow rate on fluid mixing. The numerical simulation results demonstrate that employing multiple stirring paddles enhances the mixing effects of the fluid, but there is an upper limit to this improvement. Increasing the rotation speed improves fluid mixing, but excessively high speeds generate a strong centrifugal effect. Effectively enhancing fluid mixing can be achieved by reducing the feed flow rate to prolong the reaction time. These findings are valuable for the application of multi-phase flow reactor. [ABSTRACT FROM AUTHOR]

Abstract Carbonate‐brucite chimneys are a characteristic of low‐ to moderate‐temperature, ultramafic‐hosted alkaline hydrothermal systems, such as the Lost City hydrothermal field located on the Atlantis Massif at 30°N near the Mid‐Atlantic Ridge. These chimneys form as a result of mixing between warm, serpentinization‐derived vent fluids and cold seawater. Previous work has documented the evolution in mineralogy and geochemistry associated with the aging of the chimneys as hydrothermal activity wanes. However, little is known about spatial heterogeneities within and among actively venting chimneys. New mineralogical and geochemical data (87Sr/86Sr and stable C, O, and clumped isotopes) indicate that the brucite and calcite precipitate at elevated temperatures in vent fluid‐dominated domains in the interior of chimneys. Exterior zones dominated by seawater are brucite‐poor and aragonite is the main carbonate mineral. Carbonates record mostly out of equilibrium oxygen and clumped isotope signatures due to rapid precipitation upon vent fluid‐seawater mixing. On the other hand, the carbonates precipitate closer to carbon isotope equilibrium, with dissolved inorganic carbon in seawater as the dominant carbon source and have δ13C values within the range of marine carbonates. Our data suggest that calcite is a primary mineral in the active hydrothermal chimneys and does not exclusively form as a replacement of aragonite during later alteration with seawater. Elevated formation temperatures and lower 87Sr/86Sr relative to aragonite in the same sample suggest that calcite may be the first carbonate mineral to precipitate.

The operation of a diesel engine leads to the emission of a substantial amount of waste heat flue gas, resulting in a continuous increase in the wall temperature of the exhaust system. To mitigate this continuous rise in temperature, a pre-swirling device has been developed to enhance the heat exchange between cold air and the wall, thus averting heating wall by the hot air. In this study, an experimental system was devised and implemented to analyze the dynamic behavior of the wall temperature in an air duct. The system considered both with and without the pre-swirling device, incorporating different cold air temperatures and flow rates to examine its impact on the increase in wall temperature. The results revealed a gradual rise in wall temperature after reaching a steady state, particularly demonstrating lower wall temperatures at 19 measurement points in the presence of pre-swirl compared to without swirl. Notably, the maximum temperature rise in the air duct wall was reduced by 55.7 %, from 7.9 °C without pre-swirl to 3.5 °C with the inclusion of the pre-swirling device, highlighting the significant thermal protection it provides and suggesting potential applications in exhaust thermal protection engineering. Moreover, the experimental findings consistently indicate that the incorporation of a pre-swirling device effectively diminishes the increase in wall temperature across different cold air flow rates and temperatures.

This work is concerned with nonlinear feedback control design for the problem of fluid mixing via advection. The overall dynamics is governed by the transport and Stokes equations in an open bounded and connected domain Ω ⊂ R d , with d = 2 or d = 3. The feedback laws are constructed based on the ideas of instantaneous control as well as a direct approximation of the optimality system derived from an optimal open-loop control problem. It can be shown that under appropriate numerical discretization schemes, two approaches generate the same sub-optimal feedback law. On the other hand, different discretization schemes may result in feedback laws of different regularity, which determine different mixing results. The Sobolev norm of the dual space (H 1 (Ω)) ′ of H 1 (Ω) is used as the mix-norm to quantify mixing based on the known property of weak convergence. The major challenge is encountered in the analysis of the asymptotic behavior of the closed-loop systems due to the absence of diffusion in the transport equation together with its nonlinear coupling with the flow equations. To address these issues, we first establish the decay properties of the velocity, which in turn help obtain the estimates on scalar mixing and its long-time behavior. Finally, mixed continuous Galerkin (CG) and discontinuous Galerkin (DG) methods are employed to discretize the closed-loop system. Numerical experiments are conducted to demonstrate our ideas and compare the effectiveness of different feedback laws. [ABSTRACT FROM AUTHOR]

The relationship between Sn–Ag mineralization and mantle magmatism is a topic of high interest in current ore deposit research. Here, we investigate porphyry-, skarn-, and cassiterite-sulfide type Sn-polymetallic deposits associated with granitoids and vein-type Ag–Pb–Zn deposits hosted in sub-volcanic rocks in the southern Great Xing'an Range (SGXR), northeast China, as a case example. We use He, Ar, and S isotopes and isotopic end-member simulation calculations to determine the contribution of mantle-derived fluids/melts to the ore mineralization. Our He–Ar isotope data demonstrate that the ore-forming fluids are mixtures of shallow crust-derived fluid containing radiogenic 4He but no radiogenic 40Ar and magmatic fluids with mantle-derived 3He and 40Ar. The Pb–Zn–Ag deposits have a higher contribution of magmatic volatiles than the Sn-polymetallic deposits. Sulfide δ34S values of − 2.7 to − 0.6‰ in the Pb–Zn–Ag deposits are consistent with a magmatic sulfur source, whereas sulfides with δ34S values of − 12.2 to − 0.15‰ in the Sn-polymetallic deposits signal a possibly bimodal source of sulfur, i.e., crustal light sulfur mixed with magmatic sulfur. The noble gas compositions of the ore fluids are controlled by crustal thickness, high 3He fluxes (24 to 404 at/s/cm2), and low residence time (1 to 18 Myr) of He in the asthenosphere below the SGXR. Non-equilibrium open-system magma degassing is evidenced by the range of elevated values of 4He/40Ar* ratios (4.8–127). The 3He/heat ratio of the ore fluids from the Sn and Pb–Zn–Ag deposits overlap (0.01–0.76 × 10−2 cm3 STP J−1 (cubic centimeter at standard temperature and pressure per joule) and 0.02–1.08 × 10−2 cm3 STP J−1, respectively), indicating a consequence of conduction of mantle-derived heat across the magma-hydrothermal interface. Furthermore, an increasing abundance of Sn reserves in the SGXR deposits can be equated with an increase in the mantle-derived He component in the ore fluids. These findings suggest that a continuous flux of mantle-derived fluids/melts plays an essential role in Sn–Ag–Pb–Zn mineralization. [ABSTRACT FROM AUTHOR]

Although computational fluid dynamics (CFD) modelling has been applied to study bioprocesses where mechanical mixing and aerations are key, the effect of having a free surface has usually been ignored. This work studies a mixing tank for bioprocess applications to analyze the impact that the assumption of a flat liquid level has upon the modelling results, with and without aeration. The methodology takes an experimental and modelling approach. A dual impeller mixer with a speed of 400 rpm is used for batch systems with both non‐Newtonian and Newtonian fluids to characterize the axis torque and surface vortex formation. Several multi‐phase CFD models are applied to study the modelling and numerical effects of the headspace on the results. Regarding modelling accuracy, the CFD models are shown to be able to capture the effect of the free surface on the fluid dynamics of the stirred tank for different fluid rheologies. Therefore, the simplification of the liquid level as a flat and fixed surface should not be applied, especially for a process with aeration or when unaerated conditions can lead to a surface vortex. Regarding the numerical accuracy, it is concluded that the mixture model does not predict the interface shape as well as the Eulerian model. However, only the mixture model shows to be numerically stable. Overall, this work provides validated CFD configurations able to predict the effect of a free surface on the mixing mechanisms in stirred reactors. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Unconformity-related uranium (URU) deposits in the Athabasca Basin occur in local areas near the intersections of the basal unconformity of the basin and regional-scale, basement-rooted faults. This study examines the ore-controlling factors through analysis of fluid inclusions from syn-mineralization drusy quartz in mineralized and distal (> 500 m away from mineralized zones) barren areas of two major URU-hosting structures: the P2 fault in the eastern, and the Patterson Lake corridor (PLC) in the southwestern, parts of the basin. Microthermometric data indicate that fluids in mineralized zones have salinities ranging from 24.8 to 31.7 wt.% NaCl + CaCl2 and homogenization temperatures (Th) from 64 to 227 °C, which are comparable with those from distal barren areas with salinities ranging from 25.2 to 32.5 wt.% NaCl + CaCl2 and Th from 91 to 213 °C. Laser ablation-inductively coupled plasma-mass spectrometry analyses of individual fluid inclusions indicate that the fluids have elevated concentrations of U in both mineralized zones (0.50 to 109 mg/kg) and distal barren areas (0.32 to 73.8 mg/kg). Bulk fluid inclusion analyses also indicate elevated U concentrations for mineralized zones (0.39 to 1560 mg/kg) and distal barren areas (0.12 to 1.5 mg/kg), and U was detected in fluid inclusions from both mineralized and distal areas with synchrotron X-ray fluorescence mapping. The development of uraniferous fluids with similar geochemistry in distant areas with different basement lithologies supports the hypothesis that U for mineralization was mainly derived from the basin. The presence of uraniferous fluids with similar thermal and compositional characteristics in both mineralized zones and distal barren areas along the same structures with similar lithologies suggests that mixing of U-rich fluids with reductants-carrying fluids played a critical role in ore precipitation; lack or low flux of either or both fluids resulted in lack or poor development of mineralization. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of the dynamic and thermal behavior of air-flow within a heat exchanger equipped with two distinctive baffles: a perforated baffle and a partially inclined baffle. The influence of hole positioning in the perforated baffle on the overall performance of the heat exchanger is thoroughly investigated through a systematic examination of temperature curves at varying Reynolds number values. The results demonstrate significant enhancements in flow characteristics attributed to the presence of these baffles. The flow structure exhibits prominent main currents across the gaps and secondary currents through the holes. The inclusion of these barriers leads to significant deformations and the emergence of well-developed recycling cells in the form of vortices. Both the perforated and inclined baffles effectively reduce pressure values on their frontal regions, thereby mitigating friction losses. Furthermore, the introduction of a perforation in the lower part of the baffle induces a more turbulent flow compared to the other cases. This is attributed to the expansion of the recirculating cells, resulting in improved fluid mixing and subsequent enhancement of thermal energy gain. These findings offer valuable insights into the design and optimization of heat exchangers, enabling improved performance and efficiency in various engineering applications. [ABSTRACT FROM AUTHOR]

Carbonate-hosted Pb–Zn deposits are of major economic importance. The Sichuan–Yunnan–Guizhou metallogenetic belt (SYGMB), located on the western margin of the Yangtze Block, comprises over 400 carbonated-hosted Pb–Zn deposits. However, ore-forming fluids recorded in these deposits have led to controversy regarding ore genesis. We investigated a fluid system for the Maoping deposit in the SYGMB, based on fluid inclusions, and H–O–He–Ar isotopic studies. The results showed that ore-forming fluids in the Maoping deposit are characterized by mixing of high-temperature and low-salinity metamorphic fluids and low-temperature and high-salinity basinal brines. The Precambrian basement is considered to produce metamorphic fluids, while the basinal brines are said to originate from the Youjiang Basin. The mineralization at the depositional site appears to reflect the coincidence of the metamorphic fluids, basinal brines, Carboniferous coal seams, and structural-stratigraphic traps. Regional-scale data show large-scale heterogeneity in fluid properties, including basinal brines, metamorphic fluids, and organic fluids. Furthermore, the data suggest a precipitation model for some high-grade Pb–Zn deposits in the SYGMB. These findings will contribute to an understanding of deposit types in the SYGMB. [ABSTRACT FROM AUTHOR]

The rheological response and the computational hydrodynamic continuous stirred‐tank behavior were analyzed to increase the understanding of the bioleaching process in mineral pulps. The rheological properties of the mineral pulps showed that a smaller particle size increases the magnitude of the rheological parameters, shortens the bioleaching process time, and, indirectly, increases the concentration of bacteria in the medium, thus augmenting the gel strength. The bioreactor hydrodynamics results revealed that the best dual‐impeller configuration corresponds to a Rushton (top)/Maxflo (bottom) configuration, generating power savings of ∼9 %. Finally, when analyzing apparent viscosity maps, velocity fields, and streamlines at different stirring speeds, enhanced hydrodynamic conditions were observed at 400 rpm. [ABSTRACT FROM AUTHOR]

Tungsten-tin-(rare-metal) deposits are most commonly granite-related and an important source of critical metals. This study describes the fluid evolution in the Tiantangshan Rb-Sn-W deposit, Nanling Range, China, and discusses the implications for mineralizing processes. Mineralization at Tiantangshan is spatially zoned. The greisen roof hosts wolframite-cassiterite quartz veins. The surrounding volcanic rocks host biotite quartz veins (Rb mineralization) crosscut by cassiterite quartz veins and sphalerite-galena quartz veins. The earliest intermediate-density fluids are responsible for the early W-(Sn)-Rb mineralization and evolve towards decreasing homogenization temperature (Th) and ratios of W, Sn, Rb, Cs, Fe, and Mn to Na + K as the fluid migrated from the greisen to the volcanic rocks hosted veins (Th: 420 to 350 °C; salinity: 13 to 4 wt% NaCleq). The spatial distribution of mineralization and fluid paragenesis indicates that precipitation of wolframite, early cassiterite, and Rb-rich biotite was associated with a pH increase during fluid-rock interaction. Late cassiterite and intergrown quartz precipitated from a degassing fluid with lower Th (mainly 360 to 340 °C) and salinity (10 to 2 wt% NaCleq) and with distinctly lower Sn concentrations. Late cassiterite precipitation is therefore likely related with depressurization by brittle failure of the rock leading to simultaneous boiling and meteoric water input. Late Pb–Zn mineralization precipitated from low Th (< 320 °C) and salinity (0 to 2 wt% NaCleq) fluids through extensive mixing with meteoric water. The tempo-spatial development of Rb-Sn-W-Pb–Zn mineralization at Tiantangshan was controlled by a mixing fluid regime, where input of meteoric water gradually increased with time. [ABSTRACT FROM AUTHOR]

The Hongqiling is a vein-type Sn-W polymetallic deposit in southern Hunan (South China). It is geologically located on the northern margin of the Nanling metallogenic belt. Based on the mineral assemblage and vein crosscutting relationship, three mineralization stages were identified: Sn-W mineralization (S1: cassiterite, wolframite, scheelite, arsenopyrite, molybdenite, pyrite, chalcopyrite, and quartz), Pb-Zn mineralization (S2: chalcopyrite, pyrrhotite, galena, sphalerite, pyrite, quartz, and fluorite), and late mineralization (S3: quartz, fluorite, calcite, galena, sphalerite, and pyrite). According to laser Raman probe analysis, H2O dominates the fluid inclusions in the S1 and S2 stage quartz, with CO2 and trace N2 following close behind. The ore fluid has low salinity, low density, and a wide temperature range, as per our microthermometric data: the S1 stage has homogenization temperatures (Th) of 236–377.6 °C (average 305.3 °C) and salinity of 3.5–10.7 wt.% NaCleqv; the S2 stage has Th of 206.5–332 °C (average 280.7 °C) and salinity of 1.6–5.1 wt.% NaCleqv; and the S3 stage has Th of 170.9–328.7 °C (average 246 °C) and salinity of 0.2–5.9 wt.% NaCleqv. Based on the results of the aforementioned investigation, the fluid inclusions in quartz, fluorite, and calcite are mainly H2O-NaCl vapor-liquid two-phase. Additionally, examinations of inclusions in S1 wolframite and coexisting quartz using infrared and microthermometry show that the mineralizing fluid likewise belongs to the NaCl-H2O system. The Th of inclusions in wolframite is ~40 °C higher than that of coexisting quartz. Moreover, the fluid experienced a decrease in temperature accompanied by nearly constant salinity, which indicates that wolframite precipitation is due to fluid mixing and simple cooling, and the precipitation is earlier than quartz. In situ S and H-O isotope data show that the samples have δ34S = −2.58‰ to 1.84‰, and the ore fluids have δD = −76.6 to −51.5‰ (S1 and S2), and δ18Ofluid = −6.6 to −0.9‰ (S1) and −12.9 to −10.2‰ (S2). All these indicate that the mineralizing fluid was derived from the granitic magma at Qianlishan, with substantial meteoric water incursion during the ore stage. Such fluid mixing and subsequent cooling are most likely the primary controls for ore deposition. [ABSTRACT FROM AUTHOR]

Supersonic Ejectors (SE) can be used to replace mechanical compressors in several industrial applications, including residential and commercial space heating/cooling and water heating, industrial distillation/desalination and drying systems, among others. Since SE are thermally driven, the SE-based systems can make direct use of many forms of thermal energy including waste heat, solar thermal, natural gas, or biogas, depending on emission targets, availability and cost. In this paper, Computational Fluid Dynamics (CFD) has been used to investigate the effects of different geometrical parameters and operating conditions on the ejector performance. The numerical simulations were validated against experimental measurements in terms of entrainment ratio and pressure distribution. The effects of the supersonic nozzle location and its dimensions have been investigated with respect to pressure distribution. The flow dynamics was also investigated for various geometry parameters with the purpose of identifying the mechanisms leading to higher ejector performance. The main conclusion is that under a given set of operating regimes, different geometric parameters should be simultaneously considered for an optimal performance of a supersonic ejector.

The unconformity-related uranium (URU) deposits, which are best developed in the Proterozoic Athabasca Basin (Canada), can be divided into the monometallic (U) and polymetallic (U-Ni-Co-As) subtypes. Different models have been proposed to explain the formation of the two subtypes of URU deposits. The conventional "diagenetic-hydrothermal" model suggests that both subtypes formed from oxidizing, acidic basinal brines in a unified mineralization system, whereas a newly proposed model suggests that the polymetallic deposits formed from monometallic U deposits superimposed by Ni-Co-As mineralization. While the second model has been the subject of ongoing debates, there are also unanswered questions in the diagenetic-hydrothermal model; in particular, it remains unclear what geological factors controlled the formation of one subtype or another in a unified mineralization system. This paper aims to address this question with geochemical modeling of hydrothermal U-Ni-Co-As transport and deposition using the Geochemist's Workbench (GWB) software. The conditions for U-Ni-Co-As transport were examined with thermodynamic modeling. The results indicate that highly oxidizing (log fO 2 (g) > −25), acidic (pH = 3.5) brines can transport large amounts (>100 ppm) of U together with Ni-Co-As, whereas moderately oxidizing (−40 < log fO 2 (g) < −25), less acidic (3.5 < pH < 6) brines can transport only minor amounts (<1 ppm) of U while still capable of carrying large amounts (>100 ppm) of Ni-Co-As, and very reducing (log fO 2 (g) < −40) brines with pH from 3.5 to 6 can dissolve only minor amounts (<1 ppm) of U and Ni-Co-As. The mechanisms of U-Ni-Co-As deposition were examined with reaction path modeling involving fluid-rock interaction and fluid-fluid mixing. The results indicate that as a U-Ni-Co-As-bearing, acidic, oxidizing brine progressively reacts with basement rocks or mixes with a reducing fluid, U precipitates before Ni-Co-As in relation to pH increase and fO 2 (g) decrease. In the case of fluid mixing, while U precipitation can be caused by any of the reducing agents (CH 4 (aq), H 2 (aq), H 2 S(aq), and Fe2+(aq)) in the reducing fluids examined, Ni-Co-As deposition requires the participation of CH 4 (aq) or H 2 (aq). Based on the modeling results, it is inferred that U and Ni-Co-As were not transported by the same fluid, otherwise all the URU deposits would be polymetallic. The U was most likely derived from the basin rather than from the basement, because as oxidizing basinal brines infiltrate and interact with basement rocks, their ability to dissolve and transport U quickly diminishes due to fO 2 (g) decrease and pH increase. In contrast, as these basinal brines infiltrate the upper part of the basement, which is moderately oxidizing, they retain the ability to dissolve and transport significant amounts of Ni-Co-As, enabling the scavenging of these metals from the basement. While all URU mineralization requires U-bearing basinal brines and reducing agents, the formation of polymetallic (U-Ni-Co-As) deposits depends on the availability of Ni-Co-As-rich lithologies in the upper part of the basement, together with an ample supply of robust reducing agents, such as CH 4 and H 2 that were derived from the deeper part of the basement. Therefore, although the possibility that polymetallic U-Ni-Co-As deposits formed from Ni-Co-As mineralization superimposing on monometallic U deposits cannot be ruled out, the results of this study demonstrate that both polymetallic and monometallic URU deposits can be formed in a unified diagenetic-hydrothermal mineralization system in the Athabasca Basin. • Geochemical modeling of unconformity-related U(-Ni-Co-As) mineralization in Athabasca Basin. • Polymetallic U-Ni-Co-As and monometallic U deposits controlled by metal sources and fluid flow paths. • U sourced from the basin and Ni-Co-As sourced from the upper basement. • Involvement of deeply-derived CH 4 and H 2 is essential for U-Ni-Co-As deposition. [ABSTRACT FROM AUTHOR]

As a state-of-the-art technology, micromixers are being used in various chemical and biological processes, including polymerization, extraction, crystallization, organic synthesis, biological screening, drug development, drug delivery, etc. The ability of a micromixer to perform efficient mixing while consuming little power is one of its basic needs. In this paper, a passive micromixer having vortex-generating mixing units is proposed which shows effective mixing with a small pressure drop. The micromixer works on the split and recombination (SAR) flow principle. In this study, four micromixers are designed with different arrangements of mixing units, and the effect of the placement of connecting channels is evaluated in terms of mixing index, pressure drop, and mixing performance. The channel width of 200 μm, height of 300 μm, and size of mixing units are maintained constant for all the micromixers throughout the evaluation process. The numerical simulation is performed for the Reynolds number (Re) range of 0.1–100 using Comsol Multiphysics software. By categorizing the flow patterns into three regimes based on the range of Re, the fluid flow throughout the length of the micromixer is visualized. The micromixer with dislocated connecting channels provides a satisfactory result with the mixing index of 0.96 and 0.94, and the pressure drop of 2.5 Pa and 7.8 kPa at Re = 0.1 and Re = 100 respectively. It also outperformed the other models in terms of the mixing performance. The proposed micromixer might very well be used in microfluidic devices for a variety of analytical procedures due to its straightforward construction and outstanding performance.

Experimental and numerical investigations are carried out on water injection in a humidification process of air traveling steadily through the curved part with a constant cross-section. A principal aim is to study the flow behavior through the curved duct and the generation of secondary flow. The effect of bend angle on the development of secondary flow and flow structure intensities and enhancement of the heat and mass transfer downstream the curved duct. Moreover, the influence of the mixing process between liquid and gas in an air humidification process was examined. Experiments were performed with an average air velocity range from (2.5 to 5 m/s) while keeping the water injection rate of (19 kg/h) through (50) cm square wind tunnel includes three bend angles of (45º, 90ºand 135º) along with three sets of nozzle tilt angles of (-45º, 0º and 45º) to the axial flow direction. The study also implies a numerical analysis using ANSYS FLUENT 2019 R3 with the turbulent model of RNG using (k-ε). Experimental results showed that the optimum operating condition (greater extent of cooling and humiliation) was obtained with a bend angle of 135º at axial water injection, i.e., 0º nozzle tilt angle at the lowest air velocity of 2.5 m/s. This could be attributed to the strong identical vortices developed and better droplet distribution across the duct, and more time available for heat exchange between water droplets and the air stream. The maximum reduction in treated air temperature was 28 %, with 219% in the relative humidity of the air stream. This condition gave corresponding cooling effectiveness of 58%.

This paper reports a computational modelling study of a mixing tank for bioprocess applications. A dual impeller mixer containing several probes is used with a mixing speed of 400 rpm. The single‐phase transient model is validated against experimental measurements using torque and velocity profiles as the validation variables. A complete workflow is illustrated that addresses all the relevant steps in the modelling of mixing. Many assumptions that are commonly made are explored and their importance is demonstrated. The necessity of including the probes in the computational domain is illustrated. The grid and time‐step size are examined, and the relationship between the two is explained. Two turbulence models for RANS equation closure are compared, and the efficacy of the appropriate solution methodology for each is described. The importance of using the correct near‐wall treatment is shown. Overall, this paper presents a standardized framework for the modelling of mixing tanks with turbulent flow. [ABSTRACT FROM AUTHOR]

Post‐orogenic back‐arc magmatism is accompanied by hydrothermal ore deposits and mineralizations derived from mantle and crustal sources. We investigate Zannone Island (ZI), back‐arc Tyrrhenian basin, Italy, to define the source(s) of mineralizing hydrothermal fluids and their relationships with the regional petrological‐tectonic setting. On ZI, early Miocene thrusting was overprinted by late Miocene post‐orogenic extension and related hydrothermal alteration. Since active submarine hydrothermal outflow is reported close to the island, Zannone provides an ideal site to determine the P‐T‐X evolution of the long‐lived hydrothermal system. We combined field work with microstructural analyses on syn‐tectonic quartz veins and carbonate mineralizations, X‐ray diffraction analysis, microthermometry and element mapping of fluid inclusions (FIs), C, O, and clumped isotopes, and analyses of noble gases (He‐Ne‐Ar) and CO2 content in FIs. Our results document the evolution of a fluid system of magmatic origin with increasing mixing of meteoric fluids. Magmatic fluids were responsible for quartz veins precipitation at ∼125 to 150 MPa and ∼300°C–350°C. With the onset of extensional faulting, magmatic fluids progressively interacted with carbonate rocks and mixed with meteoric fluids, leading to (a) host rock alteration with associated carbonate and minor ore mineral precipitation, (b) progressive fluid neutralization, (c) cooling of the hydrothermal system (from ∼320°C to ∼86°C), and (d) embrittlement and fracturing of the host rocks. Both quartz and carbonate mineralizations show noble gases values lower than those from the adjacent active volcanic areas and submarine hydrothermal systems, indicating that the fossil‐to‐active hydrothermal history is associated with the emplacement of multiple magmatic intrusions. Key Points: Deciphering the fossil‐to‐active hydrothermal system on Zannone Island in which magmatic and meteoric fluids mixedPolyphase and long‐lived hydrothermal activity associated with mantle‐ and crustal‐derived magmasFluid mixing and fluid‐rock interaction led to fluid neutralization, cooling, embrittlements, alteration, and minor ore minerals [ABSTRACT FROM AUTHOR]

Geothermal resource exploration is generally limited to areas with surface expressions of thermal activity (fumaroles and hot springs), or relies on expensive geophysical exploration techniques. In this study, the hidden subsurface distribution of geothermal fluids has been identified using a free and publicly available water quality dataset from agricultural and domestic water wells in Surprise Valley, northeastern California. Thermally evolved waters in Surprise Valley have element ratios that vary in response to Ca carbonate and Mg silicate mineral precipitation, and have elevated total dissolved solids (TDS). The arid climate in Surprise Valley leads to surface water evaporation in a closed basin, producing high TDS Na-Cl-CO3-SO4 brines in three ephemeral alkali lakes and in shallow groundwater under elevated soil CO2 conditions. Evaporated fluids in Surprise Valley follow a chemical divide that leads to Ca carbonate and Mg silicate mineral precipitation. Plots of dissolved element ratios can be used to distinguish groundwater affected by evaporation from water affected by thermal water-rock interaction, however it is challenging to select components for plotting that best illustrate different fluid evolution mechanisms. Here, we use a principal component analysis of centered log-ratio transformed data, coupled with geochemical models of fluid evaporation and thermal mixing pathways, to identify components to plot that distinguish between groundwater samples influenced by evaporation from those influenced by thermal processes. We find that groundwater samples with a thermal signature come from wells that define a coherent, linear geographical distribution that closely matches the location of known and inferred faults. Modification of the general approach employed here provides promise for identifying blind geothermal resources in other locations, by applying low-cost geochemical modeling and statistical techniques to areas where large groundwater quality geochemical datasets are available.

Geothermal resource exploration is generally limited to areas with surface expressions of thermal activity (fumaroles and hot springs), or relies on expensive geophysical exploration techniques. In this study, the hidden subsurface distribution of geothermal fluids has been identified using a free and publicly available water quality dataset from agricultural and domestic water wells in Surprise Valley, northeastern California. Thermally evolved waters in Surprise Valley have element ratios that vary in response to Ca carbonate and Mg silicate mineral precipitation, and have elevated total dissolved solids (TDS). The arid climate in Surprise Valley leads to surface water evaporation in a closed basin, producing high TDS Na-Cl-CO3-SO4 brines in three ephemeral alkali lakes and in shallow groundwater under elevated soil CO2 conditions. Evaporated fluids in Surprise Valley follow a chemical divide that leads to Ca carbonate and Mg silicate mineral precipitation. Plots of dissolved element ratios can be used to distinguish groundwater affected by evaporation from water affected by thermal water-rock interaction, however it is challenging to select components for plotting that best illustrate different fluid evolution mechanisms. Here, we use a principal component analysis of centered log-ratio transformed data, coupled with geochemical models of fluid evaporation and thermal mixing pathways, to identify components to plot that distinguish between groundwater samples influenced by evaporation from those influenced by thermal processes. We find that groundwater samples with a thermal signature come from wells that define a coherent, linear geographical distribution that closely matches the location of known and inferred faults. Modification of the general approach employed here provides promise for identifying blind geothermal resources in other locations, by applying low-cost geochemical modeling and statistical techniques to areas where large groundwater quality geochemical datasets are available.

Abstract Post‐orogenic back‐arc magmatism is accompanied by hydrothermal ore deposits and mineralizations derived from mantle and crustal sources. We investigate Zannone Island (ZI), back‐arc Tyrrhenian basin, Italy, to define the source(s) of mineralizing hydrothermal fluids and their relationships with the regional petrological‐tectonic setting. On ZI, early Miocene thrusting was overprinted by late Miocene post‐orogenic extension and related hydrothermal alteration. Since active submarine hydrothermal outflow is reported close to the island, Zannone provides an ideal site to determine the P‐T‐X evolution of the long‐lived hydrothermal system. We combined field work with microstructural analyses on syn‐tectonic quartz veins and carbonate mineralizations, X‐ray diffraction analysis, microthermometry and element mapping of fluid inclusions (FIs), C, O, and clumped isotopes, and analyses of noble gases (He‐Ne‐Ar) and CO2 content in FIs. Our results document the evolution of a fluid system of magmatic origin with increasing mixing of meteoric fluids. Magmatic fluids were responsible for quartz veins precipitation at ∼125 to 150 MPa and ∼300°C–350°C. With the onset of extensional faulting, magmatic fluids progressively interacted with carbonate rocks and mixed with meteoric fluids, leading to (a) host rock alteration with associated carbonate and minor ore mineral precipitation, (b) progressive fluid neutralization, (c) cooling of the hydrothermal system (from ∼320°C to ∼86°C), and (d) embrittlement and fracturing of the host rocks. Both quartz and carbonate mineralizations show noble gases values lower than those from the adjacent active volcanic areas and submarine hydrothermal systems, indicating that the fossil‐to‐active hydrothermal history is associated with the emplacement of multiple magmatic intrusions.

• A fluid-structure interaction model of acoustic resonant system was built. • The dynamic characteristics of the coupled system were systematically analyzed. • The equivalent mass of fluid decreases as the excitation amplitude increases. • Increasing the excitation frequency can enhance dynamic response of the system. This paper investigates the dynamic characteristics of a multi-degree-of-freedom (multi-DOF) acoustic resonant system involving highly viscous fluids. First, a fluid-structure interaction (FSI) model is established to describe the interaction between the multi-DOF acoustic resonant system and the two-phase fluids, and then the effects of various excitation parameters on the dynamic response of the coupled system are studied. Under the influence of vertical acoustic vibration, the fluid in the container undergoes violent and irregular motions, which leads to a decrease and fluctuation in the equivalent mass of the fluid. The reduction in fluid equivalent mass causes the excitation frequency to deviate from the natural frequency of the multi-DOF acoustic resonant system, thus significantly reducing the dynamic response of the coupled system. Furthermore, the fluctuation of the fluid equivalent mass induces a quasi-periodic motion pattern of the acoustic resonant system. Although increasing the excitation amplitude can effectively increase the dynamic response of the coupled system, it can also increase the fluctuation level of the dynamic response to a certain extent. By appropriately increasing the excitation frequency, the coupled system can operate at a new resonant frequency, thereby reducing the influence of fluid motion on the dynamic response of the system. [ABSTRACT FROM AUTHOR]

Seafloor hydrothermal chimneys from back-arc basins are important hosts for metals such as Cu, Zn, Pb, Ag, and Au. Although the general growth history of chimneys has been well documented, recent studies have revealed that the fine-scale mineralogy can be highly complex and reflects variable physicochemical conditions of formation. This study utilized a novel combination of scanning electron microscopy (SEM)-based electron backscattered difraction (EBSD) and synchrotron X‑ray fluorescence microscopy (SXFM) to uncover the detailed growth processes of multiple chalcopyrite-lined conduits within a modern chalcopyrite-sphalerite chimney from Manus Basin and to assess the controls on native gold precipitation. On the basis of previous studies, the chimney conduit was thought to develop from an initial sulfate-dominated wall, which was subsequently dissolved and replaced by sphalerite and chalcopyrite during gradual mixing of hydrothermal fluids and seawater. During this process, sphalerite was epitaxially overgrown by chalcopyrite. Accretionary growth of chalcopyrite onto this early formed substrate thickened the chimney walls by bi-directional growth inward and outward from the original tube wall, also enclosing the outgrown pyrite cluster. A group of similar conduits with slightly diferent mineral assemblages continued to form in the vicinity of the main conduit during the further fluid mixing process. Four types of distinct native gold-sulfide/ sulfosalt associations were developed during the varying mixing of hydrothermal fluids and seawater. Previously unobserved chains of gold nanoparticles occur at the boundary of early sphalerite and chalcopyrite, distinct from gold observed in massive sphalerite as identified in other studies. These observations provide baseline data in a well-preserved modern system for studies of enrichment mechanisms of native gold in hydrothermal chimneys. Furthermore, native gold is relatively rarely observed in chalcopyrite-lined conduit walls. Our observations imply that: (1) native gold is closely associated with various sulfides/sulfosalts in chalcopyrite-lined conduit walls rather than limited to the association with tennantite, Bi-rich minerals, and bornite as reported previously; and (2) the broad spectrum of gold occurrence in chalcopyrite-line conduits is likely to be determined by the various mixing process between hot hydrothermal fluids with surrounding fluids or seawater. Quantitative modeling of fluid mixing processes is recommended in the future to probe the precise gold deposition stages to eficiently locate gold in modern hydrothermal chimneys. [ABSTRACT FROM AUTHOR]

Deep hydrothermal Mo, W, and base metal mineralization at the Sweet Home mine (Detroit City portal) formed in response to magmatic activity during the Oligocene. Microthermometric data of fluid inclusions trapped in greisen quartz and fluorite suggest that the early-stage mineralization at the Sweet Home mine precipitated from low- to medium-salinity (1.5–11.5 wt% equiv. NaCl), CO2-bearing fluids at temperatures between 360 and 415 °C and at depths of at least 3.5 km. Stable isotope and noble gas isotope data indicate that greisen formation and base metal mineralization at the Sweet Home mine was related to fluids of different origins. Early magmatic fluids were the principal source for mantle-derived volatiles (CO2, H2S/SO2, noble gases), which subsequently mixed with significant amounts of heated meteoric water. Mixing of magmatic fluids with meteoric water is constrained by δ2Hw–δ18Ow relationships of fluid inclusions. The deep hydrothermal mineralization at the Sweet Home mine shows features similar to deep hydrothermal vein mineralization at Climax-type Mo deposits or on their periphery. This suggests that fluid migration and the deposition of ore and gangue minerals in the Sweet Home mine was triggered by a deep-seated magmatic intrusion. The findings of this study are in good agreement with the results of previous fluid inclusion studies of the mineralization of the Sweet Home mine and from Climax-type Mo porphyry deposits in the Colorado Mineral Belt. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic North American Midcontinent Rift hosts the world's largest accumulation of native copper in Michigan's Keweenaw Peninsula. During a regional metamorphogenic-hydrothermal event, native copper was deposited along with spatially zoned main-stage minerals in a thermal high. This was followed by deposition of late-stage minerals including minor copper sulfide. Inferences from the oxygen and carbon isotopic composition of main-stage hydrothermal fluids, as calculated from 296 new and compiled isotopic measurements on calcite, are consistent with existing models that low-sulfur saline native copper ore-forming fluids were dominantly derived by burial metamorphic processes from the very low sulfur basalt-dominated rift fill at depth below the native copper deposits. Co-variation of oxygen and carbon isotopic compositions are consistent with mixing of metamorphic-derived fluids with two additional isotopically different fluids. One of these is proposed to be evolved seawater that provided an outside source of salinity. This fluid mixed at depth and participated in the formation of a well-mixed hybrid metamorphic-dominated ore-forming fluid. Secondary Ion Mass Spectrometry in-situ isotopic analyses of calcite demonstrate a high degree of variability within samples that is attributed to variable degrees of shallow mixing of the hybrid ore-forming fluid with sulfur-poor, reduced evolved meteoric water in the zone of precipitation. The oxygen and carbon isotopic compositions of 100 new and compiled measurements on late-stage calcite are mostly isotopically different than the main-stage hydrothermal fluids. The late-stage hydrothermal fluids are interpreted as various proportions of mixing of evolved meteoric water, main-stage hybrid ore-forming fluid, and shallow, evolved seawater in the relatively shallow zone of precipitation. [ABSTRACT FROM AUTHOR]

Tin and tungsten are important metals for the industrializing society. Deciphering the origin and evolution of hydrothermal fluids responsible for their formation is critical to underpin genetic models of ore formation. Traditional approaches obtain isotopic information mainly from bulk analysis of both ore and gangue minerals, or less frequently from in situ analysis of gangue minerals, which either bear inherited complexities and uncertainties or are indirect constraints. Hence, directly obtaining isotopic information from ore minerals such as cassiterite by in situ techniques is warranted. However, this has been hampered by challenges from both analytical and applicational aspects. In this study, we first demonstrate a lack of crystallographic orientation effects during cassiterite ion microprobe oxygen isotope analysis. Along with our newly developed matrix-matched reference material, the Yongde-Cst, which has a recommended δ18O value of 1.36 ± 0.16‰ (VSMOW) as defined by gas source isotope ratio mass spectrometry, in situ oxygen isotope analysis of cassiterite now is possible. We further refine the oxygen isotope fractionation (1000 ln α) for quartz-cassiterite by first-principles calculations, which is given by the equation of 1.259 × 106/T2 + 8.15 × 103/T − 4.72 (T is temperature in Kelvin). The 1000 ln α for quartz-cassiterite has a sensitive response to temperature, and makes cassiterite-quartz an excellent mineral pair in oxygen isotope thermometry, as described by the equation of T (℃) = 2427 × (δ18Oqtz − δ18Ocst)−0.4326 − 492.4. Using the well-established 1000 ln α of quartz-water, 1000 ln α of cassiterite-water is derived as 2.941 × 106/T2 − 11.45 × 103/T + 4.72 (T in Kelvin), which shows a weak response to temperature. This makes cassiterite an ideal mineral from which to derive δ18O of fluids as robust temperature estimates are no longer a prerequisite. We have applied oxygen isotope analysis to cassiterite samples from six Sn(-W) deposits in China. The results show considerable variability in δ18O values both within a single deposit and among studied deposits. Combining the δ18O of cassiterite samples and the equilibrium oxygen isotope fractionation, we find that the δ18O values of ore-forming fluids show a strong magmatic affinity with variable but mostly no to low degree involvements (~0-10%) of meteoric water, hence our results invite a reassessment on the extent and role of meteoric water in Sn-W mineralization. This study demonstrates that in situ oxygen isotope analysis of cassiterite is a promising tool to refine sources of ore-forming fluids, and to decode hydrothermal dynamics controlling tin and tungsten mineralization. [ABSTRACT FROM AUTHOR]

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Utilizing in situ oxygen isotope analysis, we demonstrate the potential of cassiterite as a robust recorder of fluid source and evolution. Cassiterite is an ore mineral, and its mineral–water oxygen isotope fractionation factor is only weakly temperature-dependent. Unlike most explored gangue minerals such as quartz, cassiterite can provide a direct and robust archive of ore-forming fluids, e.g., fluid oxygen isotope composition (δ18O values). Core and rim domains of a representative cassiterite crystal from the Piaotang tin-tungsten (Sn-W) deposit, China, are characterized by contrasting δ18O values. Cassiterite δ18O values are –2.14 ± 0.41 ‰ for the core and 2.36 ± 0.36 ‰ for the rim, which equate to fluid δ18O values of ~ 4.1 ‰ (core) and ~ 8.6 ‰ (rim). Additionally, the cassiterite rim is enriched in niobium (Nb) and tantalum (Ta) compared to the mineral core. The δ18O, and Nb and Ta data are interpreted to reflect core to rim crystallization from distinct pulses of magmatic-hydrothermal fluids that possessed a discrete oxygen isotopic, and Nb and Ta composition. Such a pulsed process could be a common feature for Sn-W deposits, and is critical to the formation of giant deposits with high metal grades. Involvement of meteoric water associated with the first mineralization stage reaches ~ 33%, but is limited (~ 7%) in the second (main) mineralization stage. Therefore, cooling induced by fluid mixing may not be necessary for tin deposition, and our new findings invite a reassessment of the role of meteoric water in other Sn-W deposits. Our petrologic modelling shows that fluids exsolved from a 10 – 15 km3 parental granitic magma can yield the Sn-W endowments recorded at Piaotang. Further, during magma fractionation, Sn and W are preferentially transferred into fluids compared to Nb and Ta. As a consequence, fluid chemistry is the primary factor controlling metal endowment and zoning in W-Sn deposits, as observed at Piaotang, and explains the predominant magmatic origin of Nb–Ta deposits. [ABSTRACT FROM AUTHOR]

Microorganisms capable of biomineralization can catalyze mineral precipitation by modifying local physical and chemical conditions. In porous media, such as soil and rock, these microorganisms live and function in highly heterogeneous physical, chemical and ecological microenvironments, with strong local gradients created by both microbial activity and the pore-scale structure of the subsurface. Here, we focus on extracellular bacterial biomineralization, which is sensitive to external heterogeneity, and review the pore-scale processes controlling microbial biomineralization in natural and engineered porous media. We discuss how individual physical, chemical and ecological factors integrate to affect the spatial and temporal control of biomineralization, and how each of these factors contributes to a quantitative understanding of biomineralization in porous media. We find that an improved understanding of microbial behavior in heterogeneous microenvironments would promote understanding of natural systems and output in diverse technological applications, including improved representation and control of fluid mixing from pore to field scales. We suggest a range of directions by which future work can build from existing tools to advance each of these areas to improve understanding and predictability of biomineralization science and technology. [ABSTRACT FROM AUTHOR]

The Duna Pb-Ba-(Ag) mine is located ca. 155 km north of Tehran in the central Alborz structural zone, northern Iran. The ore mineralization occurs as stratabound, epigenetic, E-W and WSWENE trending veins and veinlets in fracture-controlled as well as massive and open-space filling textures within a Permian dolomitic limestone host rock. Field observations as well as mineralogical and petrographic studies show dolomitization, silicification and possibly haematisation in the host rock. In the mineralization zone, galena and barite are the main minerals, followed by pyrite, quartz, chalcopyrite, tetrahedrite, sphalerite, calcite and supergene minerals such as covellite, malachite, azurite, cerussite, anglesite, and Fe-oxides. The chemical analyses of the highgrade ore samples show an average grade of 18.66 wt. % for Pb, 19.99 wt. % for Ba, and 120 ppm for Ag together with substantial quantities of Zn (0.15 wt. %), As (690 ppm), Cu (0.86 wt. %), Sb (0.25 wt. %), and Sr (0.56 wt. %). The amount of silver in some samples from the tunnel and discordant layers is up to 7030 ppm. The positive Eu/Eu* ratio and the weak negative Ce/Ce* anomaly in the ore samples were most likely inherited from magmatic water. The presence of minerals such as pyrite and chalcopyrite together with the co-precipitation of sphalerite and chalcopyrite suggest a high-temperature for mineralizing fluids. The homogenization temperatures of fluid inclusions from barite in concordant layers span between 135 and 165 ºC with salinities between 18.54 and 23.65 wt. % NaCl equivalent, while the homogenization temperatures of fluid inclusions from barite of discordant layers span between 113 and 285 ºC with salinities between 7.34 and 23.65 wt. % NaCl equivalent. The structural, geological, geochemical, and mineralogical studies together with the paragenesis of the ore minerals and fluid inclusion data allow consideration of the Duna Pb-Ba-(Ag) mine as a two stage mineralization scenario; 1st stage /older/MVT-type (Early Cimmerian tectonic phase), and the second stage/younger/Irish-type (Laramide orogenic movements). The structural data, high temperature of the fluid inclusions, positive Eu/Eu* ratio and high silver content, especially in the discordant layers, indicate the involvement of a magmatic water mixed with meteoric and connate fluids comparable to the Irishtype mineralization in the second stage, which formed along brecciated zones of the thrust faults. The second stage of mineralization was most likely influenced by the Akapol granitoid intrusive mass, which overprinted the 1st stage/older/MVT-type. [ABSTRACT FROM AUTHOR]

We consider the evolution of two incompressible fluids with homogeneous densities ρ - < ρ + subject to gravity described by the inviscid Boussinesq equations and provide the explicit relaxation of the associated differential inclusion. The existence of a subsolution to the relaxation allows one to conclude the existence of turbulently mixing solutions to the original Boussinesq system. As a specific application we investigate subsolutions emanating from the classical Rayleigh-Taylor initial configuration where the two fluids are separated by a horizontal interface with the heavier fluid being on top of the lighter. It turns out that among all self-similar subsolutions the criterion of maximal initial energy dissipation selects a linear density profile and a quadratic growth of the mixing zone. The subsolution selected this way can be extended in an admissible way to exist for all times. We provide two possible extensions with different long-time limits. The first one corresponds to a total mixture of the two fluids, the second corresponds to a full separation with the lighter fluid on top of the heavier. There is no motion in either of the limit states. [ABSTRACT FROM AUTHOR]

The coupling between solute transport and rock's geomechanical processes, for example, flow‐induced fracture activation, has emerged as an important hydrogeological challenge due to its role in applications such as underground waste disposal, carbon sequestration, contaminant remediation, enhanced oil recovery, and tracer‐based reservoir surveillance. Despite recent advances in modeling flow and geomechanics coupling, a holistic approach to capturing the synergy between fluid flow, solute transport, induced stresses, and fracture mechanics is lacking. This study investigates the rich interplay between these processes within a novel computational framework that is proposed to solve the coupled flow, transport, geomechanics, and fracture mechanics problem. The Embedded Discrete Fracture Modeling (EDFM) method is used to model the flow and transport processes in fractured porous media while an improved Bandis model is employed to capture the fracture mechanical response to flow‐induced stress perturbations. The role of transport‐geomechanics coupling in modulating the spreading and miscibility of a solute slug during viscously unstable flows is examined. We investigate how flow‐transport coupling, parameterized through the solute viscosity contrast and the fracture permeability, influences the stress state and fracture stability in the domain. A case study, inspired by a huff‐n‐puff tracer flowback study, is conducted to investigate the applicability of the proposed framework in the field. A sensitivity analysis is performed to evaluate the dependence of global transport characteristics, permeability evolution, and fracture stability on parameters dictating the strength of coupling between geomechanics, flow, and transport. Key Points: Quantitative characterization of the geomechanical coupling effect on transport metrics: solute breakthrough time and degree of mixingMechanistic understanding of permeability evolution and fracture stability during hydrodynamically unstable transportEffect of the injected‐to‐resident fluid viscosity ratio on the stress state and fracture stability [ABSTRACT FROM AUTHOR]

The pesticide reducing has been a key issue in pesticide areas in recent years. The use of nano-carrier technology to incorporate pesticides into nanoparticles provides a new route for solving the problem. Different from most nano-carrier technologies which are based on thermodynamic equilibrium self-assembly, the emerging Flash Nanoprecipitation (FNP) method is based on kinetic control, preparing nanoparticles through turbulent mixing of chemical engineering fluids. It has advantages like high drug loading efficiency, short preparation time (milliseconds), easy to scale-up and continuously production, etc. Moreover, it can also systematically control the microstructures of nanoparticles, such as morphology, internal structure and surface structure, which can provide help for further improving the efficiency and low-toxic utilization of pesticide nanoparticles. [ABSTRACT FROM AUTHOR]