Saline Fluids Research Articles

Assessing the oxidative potential of dust from great salt Lake

Great Salt Lake (GSL) is one of the world's largest inland bodies of saltwater. Climate change, drought, and water diversions have led to the GSL reaching historically low levels, exposing over 1945 km2 of lakebed. Dust events can transport particulate matter (PM) from the GSL's exposed lakebed to the adjacent urban areas, presenting air quality and health concerns. In this study, we assessed the oxidative potential (OP) of dust from the exposed GSL bed compared to dust samples collected from other regional playas and to reference Arizona test dust. The oxidative potential of PM10 (particles ≤10 μm in aerodynamic diameter) derived from these dusts was assessed by two acellular assays: the ascorbic acid (OPAA) and dithiothreitol (OPDTT) and two extraction solvents: phosphate buffer saline and Gamble's simulated lung fluid. All samples were also analyzed for elemental composition. Our results show that the concentration of As and Li in most of the GSL dust samples exceeded the Environmental Protection Agency (EPA) soil residential regional screening levels, and the OPAA and OPDTT of dust samples from GSL playas were generally higher than the OP of other regional playas. Our findings also indicated that the OP of the GSL dust was associated with metals, including Cu, Mn, Fe, and Al. This is the first study evaluating the oxidative potential of dust from the GSL, which improves our understanding of how increasing aridity, particularly desiccation of saline lakes, affects air quality and public health.

3-D spatial distribution of concealed ore-forming granitoid intrusion and structures determined by the CSAMT survey of Wuxu Sb-Zn-polymetallic ore district, South China

Wuxu ore district is an important lead-zinc-antimony polymetallic ore field within the Danchi metallogenic belt of South China. Although previous geochemical studies have indicated that the deposit type is medium to low-temperature magmatic-hydrothermal, the existing metallogenic models remain controversial due to the thick covering layer and lack of exposure of granitic bodies. To address this issue, this study utilised four CSAMT parallel profiles across the Wuxu anticline to perform two-dimensional inversion, yielding high-resolution subsurface resistivity models. By comparing the resistivity anomalies along the regional strike shown by the profiles and integrating geochemical and ore deposit structural analyses, a detailed geological interpretation was conducted. A significant high-resistivity body beneath the core region of the Wuxu anticline is interpreted to be the Yanshanian period granitic intrusion. There are westward- and eastward-dipping high-conductivity belts existing within the western and eastern wings and appear to sandwich the inferred high-resistivity code of the Wuxu anticline, respectively. They may represent the deep faults extending underground and are the result of decoupling of lithological interface within the anticline and thereby rock fracturing. The high-conductivity feature may be the result of filling with high-conductivity saline fluids, and possible hydrothermal alteration. The regional compression stress during the Caledonian period and the early Yanshanian period promoted the formation of the anticline and rock fracturing of both wings of the anticline. After that, the regional extension background of the late Yanshanian period made the fault zones reactivated, becoming the site and channels for magmatic intrusion, upward transporting of hydrothermal fluid and alteration, causing lead-zinc-antimony polymetallic ore formation. The exposed ore deposits above may also corroborate this view point. In summary, our resistivity model visually depicts the spatial distribution of the granitic intrusion controlling ore formation and major structures such as anticlines, fault zones, and hydrothermal alteration zones in the 3-D space, providing new geophysical constraints for solving the controversy over the metallogenic model for Wuxu ore district.

Nose-to-brain delivery of nano-engineered biomaterials for effective targeting to the brain

Thermoresponsive hydrogels provide a platform for sustained delivery of nanoparticles via nose-to-brain route by resisting mucociliary clearance to the enhanced mean residence time (MRT) of the formulation in the nasal cavity overcoming neurotoxicity induced by uncontrolled delivery of nanoparticles and accumulation in the brain when delivered alone. The reported study presents the synthesis of pullulan (PLN) based nanoparticles (PNP-EHBr) loaded with eletriptan hydrobromide (EHBr) via ionic gelation method having size between 26.65 nm and 29.59 nm after stability studies of 4 h incubation with an average zeta potential of 22.5 ± 0.1 mV and entrapment efficiency of 92.048%. F-127/F-68 based hyaluronic acid-co-pectin hydrogels of EHBr-loaded PLN nanoparticles thermoresponsive hydrogels (HAP-PNP-EHBr/T-Hg) were characterized via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis (TGA/DSC), and scanning electron microscopy and evaluated for their gelation time, gelation temperature, gel strength, cloud point, sol–gel fraction, ex-vivo permeation, etc. HAP-PNP-EHBr/T-Hg showed drug release in a controlled pattern in both phosphate-buffered saline (PBS) and simulated nasal fluid (SNF) i.e., 90.12 and 87.99, respectively, over 48 h, while PNP-EHBR, 99.44 and 97.53 in PBS and SNF, respectively, over 8 h. The controlled release and absorption of EHBr from HAP-PNP-EHBr/T-Hg and PNP-EHBr was estimated by an in-vivo pharmacokinetic study using high-performance liquid chromatography, MRT and area under the curve (AUC) were increased up to 11.337 ± 0.32 h and 3,104.73 ± 75.841 ng/mL*h, 11.088 ± 0.177 h and 3,906.64 ± 152.86 ng/mL*h in brain and blood respectively after IN administration. This work demonstrates the successful synthesis of a twofold drug delivery system with PLN-based nanoparticles (PNP-EHBr) loaded with EHBr laden F-127/F-68 based hyaluronic acid-co-pectin hydrogels (HAP-PNP-EHBr/T-Hg).

Apelin-13 administration allows for norepinephrine sparing in a rat model of cecal ligation and puncture-induced septic shock

BackgroundInfusion of exogenous catecholamines (i.e., norepinephrine [NE] and dobutamine) is a recommended treatment for septic shock with myocardial dysfunction. However, sustained catecholamine infusion is linked to cardiac toxicity and impaired responsiveness. Several pre-clinical and clinical studies have investigated the use of alternative vasopressors in the treatment of septic shock, with limited benefits and generally no effect on mortality. Apelin-13 (APL-13) is an endogenous positive inotrope and vasoactive peptide and has been demonstrated cardioprotective with vasomodulator and sparing life effects in animal models of septic shock. A primary objective of this study was to evaluate the NE-sparing effect of APL-13 infusion in an experimental sepsis-induced hypotension.MethodsFor this goal, sepsis was induced by cecal ligation and puncture (CLP) in male rats and the arterial blood pressure (BP) monitored continuously via a carotid catheter. Monitoring, fluid resuscitation and experimental treatments were performed on conscious animals. Based on pilot assays, normal saline fluid resuscitation (2.5 mL/Kg/h) was initiated 3 h post-CLP and maintained up to the endpoint. Thus, titrated doses of NE, with or without fixed-doses of APL-13 or the apelin receptor antagonist F13A co-infusion were started when 20% decrease of systolic BP (SBP) from baseline was achieved, to restore SBP values ≥ 115 ± 1.5 mmHg (baseline average ± SEM).ResultsA reduction in mean NE dose was observed with APL-13 but not F13A co-infusion at pre-determined treatment time of 4.5 ± 0.5 h (17.37 ± 1.74 µg/Kg/h [APL-13] vs. 25.64 ± 2.61 µg/Kg/h [Control NE] vs. 28.60 ± 4.79 µg/Kg/min [F13A], P = 0.0491). A 60% decrease in NE infusion rate over time was observed with APL-13 co-infusion, (p = 0.008 vs NE alone), while F13A co-infusion increased the NE infusion rate over time by 218% (p = 0.003 vs NE + APL-13). Associated improvements in cardiac function are likely mediated by (i) enhanced left ventricular end-diastolic volume (0.18 ± 0.02 mL [Control NE] vs. 0.30 ± 0.03 mL [APL-13], P = 0.0051), stroke volume (0.11 ± 0.01 mL [Control NE] vs. 0.21 ± 0.01 mL [APL-13], P < 0.001) and cardiac output (67.57 ± 8.63 mL/min [Control NE] vs. 112.20 ± 8.53 mL/min [APL-13], P = 0.0036), and (ii) a reduced effective arterial elastance (920.6 ± 81.4 mmHg/mL/min [Control NE] vs. 497.633.44 mmHg/mL/min. [APL-13], P = 0.0002). APL-13 administration was also associated with a decrease in lactate levels compared to animals only receiving NE (7.08 ± 0.40 [Control NE] vs. 4.78 ± 0.60 [APL-13], P < 0.01).ConclusionAPL-13 exhibits NE-sparing benefits in the treatment of sepsis-induced shock, potentially reducing deleterious effects of prolonged exogenous catecholamine administration.

Geochemistry of coastal geothermal systems from southern Baja California peninsula (Mexico): Fluid origins, water-rock interaction and tectonics

The Baja California peninsula forms the western margin of the Gulf of California (GC) rift system, which is an active tectonic setting manifested by seismicity and numerous geothermal sites. The present study examines the geochemistry of thermal fluids (major ions and gas species, δ18O-δD, δ13C, 3He/4He) from the southern tip of the peninsula (Los Cabos Block, LCB). Sampling was mostly focused on the coastal thermal manifestations in the towns of Buenavista and El Sargento, but other sites further inland are also included for broadening the scope of the study. The main objectives include: (i) characterize water-rock interactions and other processes controlling the fluid composition, (ii) constrain solute geothermometry estimates through multi-step geochemical modeling, and (iii) discuss the fluid origins in terms of tectonics and regional shear-wave velocity anomalies in the upper lithosphere. The geothermal systems in the area have a tectonic origin and result from fluid circulation along regional faults that penetrate the upper crust through the granitic basement. Mixing between the thermal fluids and seawater at the coast is clearly illustrated through major ions and δ18O-δD relationships. Reconstruction of the pre-mixing chemical compositions indicates a low-salinity fluid at Buenavista (Cl = 104–109 mg L−1) and a saline fluid at El Sargento (Cl = 7169 mg L−1). The geochemical modeling allows us to validate these endmember compositions and to address a common issue when using solute geothermometry, which is the uncertainty on the state of equilibrium of the thermal fluid with respect to wall-rock minerals. The corresponding results reveal contrasting thermal regimes at depths (Buenavista: 101–122 °C, El Sargento: 212–220 °C), likely associated with differences in geothermal gradient and fluid circulation depth. Our gas samples have among the lowest He isotopic ratios (0.07–0.95 Ra) in the Baja California peninsula, indicating that the origin of helium is mainly crustal. Shear wave tomography demonstrates that the study area is associated with two low velocity regions, one in the crust and the other one in the upper mantle. Our results favor the hypothesis that the heating of fluids is produced by lower-crustal flow driven by strong topographic gradients along the rifted margin. This study provides new insights into the origin of the thermal anomalies in the LCB and the adjacent GC rift system.

Effects of inorganic salt ions on the wettability of deep coal seams: Insights from experiments and molecular simulations

Coal wettability plays a significant role in the efficiency of coalbed methane (CBM) extraction since it determines fluid transport and distribution. Deep coal seam aqueous fluids have a high salinity. Consequently, coal wettability experiments utilizing fresh water are not representative for those coal seams. Therefore, the effect of aqueous fluids with inorganic salt ions on coal wettability needs to be investigated. In this study, both experiments and molecular simulations are conducted to unravel the wetting behaviour and mechanisms of saline fluids on coal surfaces, investigating different fluid salt concentrations, temperatures, valence states, and coal pore sizes. The results reveal that a more saline fluid displays a more hydrophobic behaviour on the coal surface. Microscopically, water molecules have a tendency to assemble around cations and anions as hydration shells and gradually detach from the coal surface, leading to a gradual transition from hydrophilicity to hydrophobicity. A change in wettability with fluid salinity can be caused by two mechanisms. On the one hand, an increase in ion concentration constrains the diffusion of water molecules through hydration, weakening the mobility of water molecules. On the other hand, a higher ion concentration weakens the interaction between water molecules and oxygen-containing functional groups, reducing the affinity of the water molecules with the pore wall. Moreover, at higher temperatures, ion valence states, and for coal with smaller pores, the impact of inorganic salt ions in fluids on the wetting behaviour of coal surfaces becomes more significant. The coal wettability influences the capillary pressure of coal pores. This study provides new insights on the effect of saline fluids on coal wettability which may help address challenges of fracturing fluid loss and water-blocking in CBM production activities.

Lithospheric electrical structure and geodynamic model of the red river fault zone and its adjacent areas in southwest China: Constraints from 3-D magnetotelluric imaging

The Red River Fault (RRF) zone is situated on the southeastern boundary of the Tibetan Plateau. To further explore the geodynamic model of the region and the collision mechanism of the Eurasian continent, the electrical structure model of the lithosphere in the RRF was obtained through 3-D inversion of MT data. The preferred model indicated that fault zones were primarily distinguished by low resistivity anomalies, with some exhibiting high resistivity characteristics. It was hypothesized that the low resistivity anomalies may be attributed to the presence of saline fluids or metal sulfide within the fault zones, on the other hand, the high resistivity characteristics suggested inactivation due to fault cooling. Rapid changes in the electrical structure occurred on both sides of the fault zones, causing the upper and middle crust to be divided into distinct secondary tectonic units. Based on the effective viscosity calculation, we analyzed the crust-mantle rheology of the RRF area. We assumed that the RRF area was composed of three geodynamic models: the “crustal flow” model was distributed from the northern part of the Lancang River Fault (LCRF) zones to the southern part of the RRF zones. The “ductile continuum rheology” model was distributed from the north of the RRF to the western part of the Xiaojiang Fault (XJF) zones. The “mantle upwelling” model was distributed in the southeast part of the RRF.

Geochemistry and fluid inclusion study of the Jbel Tirremi fluorite-baryte deposit, Morocco: New insights into the genetic model in relation to Mesozoic tectonics

The highly fractured Jurassic carbonates at Jbel Tirremi in northeastern Morocco host fluorite-baryte deposit. The mineralization occurs both as stratabound in marl-limestone contact and as fault-hosted veins (N-S- and NNW-SSE). The mineral paragenesis consists of two fluorite and baryte generations and calcite with subordinate amounts of quartz, dolomite, traces of sulfides (chalcopyrite, pyrite, galena), and oxidized minerals. Fluid inclusion data reveal that hot moderately saline fluids derived from the Paleozoic basement mixed with Triassic brines and cooler, meteoric waters. The REY inventory, C-O-S-Pb-Sr-Nd isotope, and crush-leach data point to the Paleozoic basement as the primary source of metals with a contribution from the Triassic red beds. The refined ore genetic model developed in this study from our new geological and geochemical data includes the downward movement of Triassic-Jurassic evaporated seawaters along normal faults, followed by the leaching of metals from Paleozoic and Triassic rocks, and the subsequent upward flow of these metalliferous fluids. During the Late Cretaceous-Paleocene basin inversion, the deep-seated ore-forming fluids migrated upward, which eventually mixed with Triassic brines and cooler meteoric waters. This fluid mixing caused the precipitation of multiple generations of fluorite and baryte.

Parametric study of low‐temperature solar‐assisted flash evaporation desalination systems using two‐phase water–steam ejector

AbstractThis study aims to investigate a two‐phase subsonic ejector added to a flash evaporation desalination system to increase the system productivity of distilled water. The flash evaporation was of low‐temperature condition that it could be powered by a flat and evacuated tube solar water heater. A parametric study of superheat degree (range 5°C–25°C), back pressure (range 10–30 kPa of absolute pressure), primary fluid flow rate (range 1–3 L/min), nozzle diameter (range 1–3 mm), and salinity concentration (range 0%–7%) were investigated to examine the system productivity and the ejector performance in terms of its entertainment ratio under different operating conditions. Results show that the inclusion of the ejector led to an average of 99% improvement in system productivity, primarily through the efficient secondary flow. Moreover, the effect of the studied parameter was more pronounced in the considered flash evaporation desalination system as it has two places where flash evaporation occurs, compared with the normal system where the flash evaporation occurs at one place. All in all, the application of the ejector could enhance the system's productivity significantly under different operating conditions.

Fluid Inclusion Petrography and Microthermometry of Barren/Mineralized Quartz Veins-Reef of Malanjkhand Cu Deposit, Central India: Implication on Ore and Non-Ore Forming Environment

Quartz reefs and veins of variable thickness have been intruded in host Paleoproterozoic Malanjkhand granites in the mine area and are primarily restricted to phyllic as well as potassic alteration zones. They are mainly of two types: mineralized and barren. Fluid inclusion petrography depicts mainly five types of inclusion which are aqueous biphase, monophase, monocarbonic, H2O-CO2 and polyphase (L+V+H). They are called here Type I, Type II, Type III, Type IV, and Type V, respectively, and are present in both mineralized and barren quartz veins/reefs. All types of inclusion are common except type V, which appears rare in both. However, the sizes of type II and IV are unexpectedly small. The micro thermometry results imply a relatively high temperature (209.4-376.4oC) of fluid entrapment in the mineralized counterpart. However, it is considerably lower (133.9-182.2oC) for the barren counterpart. Although the salinity of fluid appears low for mineralized quartz veins/reef (0.63-0.87 wt.% NaCl equivalent), while for barren counterpart, it is considerably higher (0.92-0.98 wt.% NaCl equivalent). The observed textural and microthermometry results advocate that the Malanjkhand hydrothermal system has resemblances with the porphyry system and indicates probable genetic linkage between barren and mineralized quartz veins/reef. Keywords: Fluid Inclusions, Quartz Veins/Reef, Aqueous Inclusions

Barite Replacement as a Key Factor in the Genesis of Sediment-Hosted Zn-Pb±Ba and Barite-Sulfide Deposits: Ore Fluids and Isotope (S and Sr) Signatures from Sediment-Hosted Zn-Pb±Ba Deposits of Iran

Iran hosts more than 350 Precambrian to Cenozoic sediment-hosted Zn-Pb±Ba and barite-sulfide deposits, including shale-hosted massive sulfide (SHMS, also called SEDEX) and Irish-type and Mississippi Valley-type (MVT) mineralization, and barite is a common mineral in these deposits. In the SHMS deposits, barite is typically found as fine-grained disseminations in thin laminae. In these deposits, the sulfide laminae often occur as diagenetic replacements and as bands containing authigenic and diagenetic barite and pyrite framboids. In the Irish-type Zn-Pb-Ba and stratabound barite-sulfide deposits, barite exhibits various textures, including fine-grained disseminated barite, banded zebra textures, veins, and massive barite lenses. In some of the giant Irish-type deposits, as well as in the stratabound barite-sulfide mineralization, the main stratabound sulfide ore is developed within a barite envelope and is characterized by the replacement of barite and pyrite by chalcopyrite, galena, and sphalerite. In the MVT deposits, the formation of barite is often related to dolomitization, and sulfide mineralization involves the replacement of the dolomitized carbonate rocks, as well as associated barite. Fluid inclusion studies on the Irish-type deposits indicate that the temperatures and salinities of the sulfide-forming fluids are higher compared to those of the barite-forming fluids. Fluid inclusion analyses of coarse-grained barites from Irish and MVT deposits reveal their hydrothermal origin. The δ3⁴S values of sulfide minerals (pyrite, sphalerite, and galena) in Irish-type deposits exhibit a broad range of low values (mostly −28 to +5‰), primarily revealing a process of bacterial sulfate reduction (BSR). However, the textures (replacement, colloform, and banded) and more positive sulfur isotope values (+1 to +36‰) in the SHMS Zn-Pb deposits suggest that bacterial sulfate reduction (BSR) plays a less significant role. We suggest that thermochemical sulfate reduction (TSR) connected to the direct replacement of barite plays a more relevant role in providing sulfur for the sulfide mineralization in the SHMS, barite-sulfide, and MVT deposits. Based on the textual evidence, sulfur isotopic data, and fluid inclusion studies, barite has been identified as a key controller for the subsequent Zn-Pb mineralization by providing a suitable host and significant sulfur contribution in the sediment-hosted Zn-Pb and stratabound barite-sulfide deposits. This implies that diagenetic barite might be a precursor to all types of sediment-hosted Zn-Pb mineralization.

Parametric study on the margination of white blood cells (WBCs) in a passive microfluidic device

From fundamental research exploring molecular mechanisms to advanced endeavours like the development of artificial white blood cells, white blood cells have widespread applications due to their crucial role in safeguarding the body, defending against infection, and eliminating external pathogens, serving as indicators of several diseases. So, white blood cells must be separated efficiently with high purity to make the passive microdevices more effective for diagnostic applications. In this study, we investigated how cell concentration and viscosity collectively impact the margination of white blood cells in an inertial flow microchannel. We aim to improve white blood cell separation efficiency in microfluidic devices. Unlike previous studies that examined individual factors, this research focused on the interplay between bio-physical properties like cell interaction and viscosity. To explore their correlation, we diluted the blood with phosphate-buffered saline and viscoelastic fluid to manipulate the viscosity and cell concentration. Viscoelastic fluid improved white blood cells margination, while higher viscosity and low cell concentration decreased it. Maintaining blood-like viscosity, optimizing cell-free layer width, and promoting cell-cell interaction in the focusing zone collectively enhanced white blood cells margination.

Effect of silica-sprayed collection tubes on synovial fluid bacterial culture.

Silica-sprayed tubes (SSTs) are often used to transport synovial fluid samples in equine practice. They promote the coagulation of the sample. The objective of the study is to evaluate the effect of SST on bacterial culture. The study was divided into two parts: sterile saline (Part A) and synovial fluid (Part B). Four common bacteria associated with equine synovial sepsis were used: Streptococcus pyogenes, Escherichia coli, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Three collection tubes were used: STT, plain (no-additives) and brain and heart infusion (BHI) broth. Bacteria were cultured in horse blood agar plates for 48h. Outcome variables were negative culture, positive culture and total number of colony-forming units (CFUs). Statistical analysis was performed using Mann-Whitney U test, and significance was set at p<0.05. The total number of agar plates read was 1557 (779 saline; 778 synovial fluid). Total negative cultures were 25/779 on saline and 3/778 on synovial fluid. In broth, maximum growth CFU was achieved after 8h for both saline and synovial fluid for all bacteria. S. pyogenesand E. coli produced a significantly lower number of CFU when in SST compared to plain or broth after 4h, whereas S. aureus (American Type Culture Collection [ATCC] and MRSA) only after 24h. Silica-containing tubes reduced bacterial proliferation, whereas the use of a BHI broth provided the highest bacterial load in the sample. The use of SST may have a negative effect on bacterial proliferation in samples obtained from clinical cases.

Effects of fluid composition and salinity on subcritical crack growth in granite

Using the double-torsion technique, the fracture mechanical response of granite specimens was investigated under the influence of fluid with different electrolyte types and salinities. The fracture toughness (KIC) and critical mechanical energy release rate (G0) of the granite in electrolyte solution are weakened compared to those in distilled water. The KIC in all electrolyte solutions is 2.08–2.28 MPa·m1/2, which is 8.4 % − 16.5 % lower than that in distilled water, and it is insensitive to ion type and salinity. In contrast, the subcritical crack growth index (n) shows different salinity dependence in three salt (AlCl3, CaCl2, and NaCl) solutions. The slight increase in n with rising salinity of the AlCl3 solution is attributed to crack tip blunting caused by over-dissolution of minerals. The n and G0 decrease and then increase with rising salinity of CaCl2 solution, which may be related to the salinity-dependent dissolution rate of quartz and the weakening of repulsive force between crack surfaces. The n and G0 shows a negative correlation with salinity and decrease by 26.4 % and 15.4 %, respectively as the NaCl salinity increases from 0.1 M to 1.0 M. Limitations in the dissolution reactions of the main minerals (albite, biotite and diopside) is accountable for enhancement of n in silica solutions. Experimental results emphasize the critical and subcritical fracture behavior of the granite in response to chemically reactive fluids with implications for both hydraulic fracture stimulations in geothermal fields and caprock integrity for CO2 sequestration. In these applications, the fracture properties of the reservoir rock can be enhanced or weakened by changing the electrolyte type and salinity of the fluid, depending on the actual requirements.

Albitization related U and Th mobilization under reducing conditions

Hydrothermally altered quartzofeldspathic gneisses, granites and pegmatites of the West Garo Hills, Shillong Plateau (eastern India) preserve alteration assemblages of monazite, xenotime and zircon comprising thorite and coffinite in the altered domains. Albitization of muscovite and K-feldspars, sericitization of K-feldspar and albite, alteration of biotite to hydrobiotite, and crystallization of tourmaline is suggestive of the involvement of acidic fluids. The microtextural relations and the mineral assemblages indicate prevalence of low-temperature (T < 300 °C) conditions during hydrothermal alteration. The light δ11B values of tourmaline (–15.1 to –13.5 ‰) suggests derivation/interaction of the fluids from/with metapelitic rock and/or S-type granite. Low ‘inferred’ Fe3+/Fe2+ ratio in tourmaline (based on high Al content in Y-site, 0.16–0.56 apfu, avg. 0.36 apfu), estimated excess charge (0.22–0.47, avg. 0.35 apfu) and lack of any Fe–Al relation support a reduced nature of the hydrothermal fluid. Mass balance calculations reveal that Th and U required for the formation of thorite and coffinite, respectively were likely derived from monazite and xenotime, and zircon. Significantly lower Cl─ contents in hydrobiotite (avg. 0.03 wt%) compared to the unaltered biotite (avg. 0.13 wt%) suggests release of Cl─ to the hydrothermal fluid during alteration. Textural evidences of albitization together with Cl─ release from biotite suggest increased Cl─ concentrations in the fluid during hydrothermal alteration. Based on solubility calculations for various U and Th species, we propose that high Cl─ content in the fluid aided mobilization of Th and U as ThCl40 and UCl40/UO2Cl20 complexes from accessory radioactive phases under reducing conditions. These results suggest that significant mobility of U and Th can be achieved in acidic high salinity fluid even under reducing conditions. Thermodynamic calculations for the solubility of Th- and U-chloride complexes and stability of monazite/xenotime in a range of pH and temperature suggest that thorite and coffinite precipitation was the result of an increase in pH.

The interplay between dolomitizing fluids, tectonically-controlled saddle dolomite and calcite cements in lower Cambrian to Furongian strata in the Tazhong Uplift

The interplay between dolomitizing fluids, tectonically-controlled saddle dolomite and calcite cements in Lower-Cambrian to Furongian strata in the Tazhong Uplift, Tarim Basin were interpreted from petrography, geochemistry and fluid inclusions microthermometry. Stochiometric replacement dolomites (RD1, RD2 and RD3) and saddle dolomite (DC) cement were identified. Equant-drusy calcite (ECAL) and blocky-to columnar calcite (LCAL) cements were identified. Weak relationships exist between δ13C, δ18O, 87Sr/86Sr, Mg/Ca versus Mn/Sr ratios, which are tools used to evaluate the impact of diagenetic environment on C–O–Sr isotope composition of the carbonates. The replacement dolomites and DC with high Mg/Ca ratios (0.97–1.21) have low depleted δ18O, δ13C values, compared to the ECAL and LCAL with more depleted δ18O, δ13C values, indicating that the C–O–Sr isotope composition suffered diagenetic alteration by higher-temperature and equilibrium isotopic fractionation. The carbonates fluid system is characterized by negative shift in C–O-isotopic composition with hypersaline signatures compared to Early Paleozoic evaporative seawater. Moreover, the increasing trend in (Cl, Br, I)/(CaO + MgO) ratios with Mg/Ca ratios, couple with positive relationship between Cl and Br, suggests fluids contamination by halogen-rich inclusions. The RD1, RD2 and RD3 were precipitated by relatively higher-temperature saline fluids at depth during shallow-deep burial dolomitization. The DC have average Th-values (141.5–199.2 °C) mostly higher than the estimated ambient temperatures (165 °C) of the studied strata, meaning their growth in fractures resulted from higher-temperature Mg-enriched saline basinal fluids conveyed by hydrothermal convection and short-lived geothermal squeegee-type flow. The LCAL were precipitated by Ca/Mg-enriched basinal brine fluids diluted by influx of meteoric water, cementing fractures in host rocks, as dolomite was replaced by calcite (i.e., calcitization). The conceptual model reveals that dolomitizing fluids and calcitization fluids were conveyed through permeable horizons resulting from strong extensional tectonics and weak compressional tectonics, forming irregular networks of saddle dolomite and calcite cement in host rocks.

Natural metal contents and influence of salinization in deep Canadian Shield groundwater: Base level versus mineral deposit enrichment halos

Groundwater interacts with mineral deposits, making this secondary environment a medium of choice for geochemical exploration. With increasing depth, groundwater in Precambrian shields typically matures and increases in salinity through prolonged water–rock interactions and mixing with geologically old saline fluids. As the focus of mineral exploration is gradually shifting toward deeper targets, the influence of salinity on pathfinder background levels and anomalous thresholds must be considered. We compiled a deep background database (Deep Abitibi Groundwater database; DAGW) containing groundwater samples between depths of 0 m and 690 m from barren exploration boreholes in the Abitibi subprovince, Quebec, to evaluate the natural elemental levels at depth. The DAGW provides valuable knowledge of the base levels of a wide spectrum of elements and of the changes in these base levels along with the increasing salinity in bedrock aquifers of the deep Canadian Shield. This can serve to estimate background values during hydrogeochemical exploration campaigns. The regional Abitibi base level for Zn (median of 7.5 μg/L), a key pathfinder for VMS mineralization, is unaffected by the increasing salinity levels down to depths of 690 m. Hence, down to this depth, the Zn concentrations measured may be used directly for mineral exploration, and no further correction for the effects of salinization is necessary. We conducted a case study near an undisturbed VMS-type deposit (Daniel 25) and a Zn enrichment halo was observed. Within the halo, Zn concentrations increased with depth, indicating that Zn mobility was positively affected by the geochemical conditions of the deeper aquifer. Anomalous Zn thresholds representing the proximal (50–600 m from the mineralization) and direct contact (within 50 m of the mineralization) footprints of the Daniel 25 deposit were estimated at 50 μg/L and 380 μg/L, respectively. An anomalous threshold was also estimated for Co, a secondary pathfinder, at 0.5 μg/L. Unlike Zn, several other elements, which could be used to trace mineral deposits, are affected by salinization. As a final step, we applied a correction to the Daniel 25 data, based on elemental baseline trends observed in the DAGW. The aim was to remove the effects of salinity and enhance the statistical correlations caused by the presence of the mineralized body. This correction led to the emergence of new spatial correlations, notably with Na and Sr, that are coherent with the increasing hydrothermal alteration in proximity to the ore.

Fluid origin and evolution of the Taolin Pb-Zn deposit in northeastern Hunan Province, South China: Insights from fluid inclusions and H-O-He-Ar isotopes

Situated in northeastern Hunan Province, the vein-type Pb-Zn orebodies at Taolin are mainly hosted in NE-/NEE-trending faults between Dayunshan-Mufushan pluton and Neoproterozoic metasedimentary rocks of the Lengjiaxi Group. Hydrothermal mineralization can be divided into five stages: (1) coarse-grained quartz stage, (2) quartz-fluorite-base metal stage, (3) quartz-barite-fluorite-base metal stage, (4) pale pink and colorless quartz stage, and (5) fine-grained quartz stage. In this research, fluid inclusions as well as stable (H-O) and noble gas (He-Ar) isotope compositions were performed to uncover the nature, origin, and evolution of the ore-forming fluids, ore precipitation mechanisms, and mineralization process of the Taolin deposit. Four types of fluid inclusions, i.e., liquid-rich two-phase inclusions (LV-type), pure liquid phase inclusions (PL-type), vapor-rich two-phase inclusions (VL-type), and pure vapor phase inclusions (PV-type), were distinguished in sphalerite, quartz, and fluorite. Microthermometric analysis of fluid inclusion assemblages in sphalerite, quartz, and fluorite from different stages indicates that from the Stage 1 to Stage 5, the homogenization temperatures vary between 168 and 211 °C, between 151 and 198 °C, between 131 and 180 °C, between 132 and 164 °C, and between 118 and 138 °C, respectively, whereas the fluid salinities vary from 12.4 to 16.9 wt% NaCl equivalent, from 9.7 to 14.6 wt% NaCl equivalent, from 5.6 to 10.3 wt% NaCl equivalent, from 3.6 to 9.7 wt% NaCl equivalent, and from 0.9 to 3.8 wt% NaCl equivalent, respectively. The H-O isotope data of quartz and the He-Ar isotopic compositions of sulfide crystals suggest that the ore-forming fluids were a mixture of crust-derived magmatic hydrothermal fluid and meteoric water. Fluid mixing and cooling were likely the crucial mechanisms for ore precipitation.

The Chain of Processes Forming Porphyry Copper Deposits—An Invited Paper

Abstract Porphyry-related mineral deposits are giant geochemical anomalies in the Earth’s crust with orders-of-magnitude differences in the content and proportion of the three main ore metals Cu, Au, and Mo. Deposit formation a few kilometers below surface is the product of a chain of geologic processes operating at different scales in space and time. This paper explores each process in this chain with regard to optimizing the chances of forming these rare anomalies. On the lithosphere scale, deposits with distinct metal ratios occur in provinces that formed during brief times of change in plate motions. Similar metal ratios of several deposits in such provinces compared with global rock reservoirs suggest preceding enrichment of Au or Mo in lithospheric regions giving rise to distinct ore provinces. The largest Cu-dominated deposits and provinces are traditionally explained by selective removal of Au during generation or subsequent evolution of mantle magmas, but the possibility of selective Cu pre-enrichment of lithosphere regions by long-term subduction cannot be dismissed, even though its mechanism remains speculative. Evolution of hydrous basaltic melts to fertile magmas forming porphyry Cu deposits requires fractionation toward more H2O-rich magmas in the lower crust, as shown by their adakite-like trace element composition. The prevailing interpretation that this fractionation leads to significant loss of chalcophile ore metals by saturation and removal of magmatic sulfide might be inverted to a metal enrichment step, if the saturating sulfides are physically entrained with the melt fraction of rapidly ascending magmas. Ascent of fertile magma delivers a large mass of H2O-rich ore fluid to the upper crust, along points of weakness in an overall compressive stress regime, within a limited duration as required by mass and heat balance constraints. Two mechanisms of rapid magma ascent are in debate: (1) wholesale emplacement of highly fractionated and volatile-rich granitic melt into a massive transcrustal channelway, from which fluids are exsolved by decompression starting in the lower crust, or (2) partly fractionated magmas filling a large upper crustal magma chamber, from which fluids are expelled by cooling and crystallization. Transfer of ore-forming components to a hydrothermal ore fluid is optimized if the first saturating fluid is dense and Cl rich. This can be achieved by fluid saturation at high pressure, or after a moderately H2O rich intermediate-composition melt further crystallizes in an upper crustal reservoir before reaching fluid saturation. In either case, metals and S (needed for later hydrothermal sulfide precipitation) are transferred to the fluid together, no matter whether ore components are extracted from the silicate melt or liberated to the ore fluid by decomposition of magmatic sulfides. Production and physical focusing of fluids in a crystallizing upper crustal magma chamber are controlled by the rate of heat loss to surrounding rocks. Fluid focusing, requiring large-scale lateral flow, spontaneously occurs in mushy magma because high water content and intermediate melt/crystal ratio support a network of interconnected tubes at the scale of mineral grains. Calculated cooling times of such fluid-producing magma reservoirs agree with the duration of hydrothermal ore formation measured by high-precision zircon geochronology, and both relate to the size of ore deposits. Ore mineral precipitation requires controlled flow of S- and metal-rich fluids through a vein network, as shown by fluid inclusion studies. The degree of hydrothermal metal enrichment is optimized by the balance between fluid advection and the efficiency of cooling of the magmatic fluid plume by heat loss to convecting meteoric water. The depth of fluid production below surface controls the pressure-temperature (P-T) evolution along the upflow path of magmatic fluids. Different evolution paths controlling density, salinity, and phase state of fluids contribute to selective metal precipitation: porphyry Au deposits can form at shallow subvolcanic levels from extremely saline brine or salt melt; high-grade Au-Cu coprecipitation from coexisting and possibly rehomogenizing brine and vapor is most efficient at a depth of a few kilometers; whereas fluids cooling at greater depth tend to precipitate Cu ± Mo but transport Au selectively to shallower epithermal levels. Exhumation and secondary oxidation and enrichment by groundwater finally determine the economics of a deposit, as well as the global potential of undiscovered metal resources available for future mining.

A numerical model for the quantification of fluid inclusion property variations caused by heterogeneous entrapment and post-entrapment modifications in the H2O-NaCl system

The primary geological conditions for hydrothermal systems can be reconstructed using fluid inclusions, which generally requires that fluid inclusions trapped a single homogeneous phase and experienced no mass and volume changes after entrapment (Roedder's Rules). However, heterogeneous entrapment and post-entrapment modifications have been frequently identified in fluid inclusion studies, making the recovery of primary fluid properties from fluid inclusion data challenging or impossible. In this study, we constructed a specific tool, FlincPro, for the calculations of ideal and nonideal Fluid inclusion Properties in the H2O-NaCl system (ideal here refers to fluid inclusions that adhere to Roedder's Rules). Multiple modules have been developed to quantify the variations of fluid inclusion properties caused by heterogeneous entrapment, volume contraction/expansion, and water loss. The developed software illustrates possibilities in the variation of fluid inclusions in a specific assemblage with the input of a certain starting point.We found that compositions of the vapor endmember fluid are more significantly affected by heterogeneous entrapment than the liquid endmember, as the latter may have several orders of magnitude higher salinity and density. Homogenization pressure and temperature of halite-bearing fluid inclusions trapped on the halite liquidus will increase sharply with the addition of halite, but the homogenization behavior will not be changed. Volume contraction/expansion are effective ways to change the homogenization behaviors, especially for high salinity fluid inclusions. Water loss is not likely to cause the homogenization behavior change from total homogenization by vapor disappearance to total homogenization by halite dissolution for a halite-bearing fluid inclusion without additional volume contraction. Low-salinity and low-density fluid inclusions with total homogenization temperature around the critical temperature of water are least affected by post-entrapment modifications. Therefore, the interpretation of fluid inclusions formation depends on more parameters, e.g., petrographic observations, density and composition variations in fluid inclusion assemblages, and geological information, than only microthermometric data.