Sulfate is traditionally considered to have retrograde solubility in aqueous solutions. However, our recent hydrothermal diamond-anvil cell (HDAC) experiments have shown that the solubility of Na2SO4 ...changes from retrograde to prograde in the presence of silica, leading to the formation of sulfate-rich solutions at high temperatures, in line with observations on natural geofluids. In this study, we use synthetic inclusions of fused silica capillary capsules containing saturated Na2SO4 solutions and Na2SO4 crystals to quantitatively investigate the solubility of Na2SO4 at different temperatures in the Na2SO4-SiO2-H2O system. Sulfate concentrations were measured using Raman spectroscopy and calibrated using Cs2SO4 solutions with known concentrations. The solubility of crystalline Na2SO4 dropped slightly when heated from 50 to 225°C and dramatically from 225 to 313°C. At 313°C, the Na2SO4 crystals began to melt, forming immiscible sulfate melt coexisting with the aqueous solution, with or without solid Na2SO4. With the formation of sulfate melt, the solubility of Na2SO4 was reversed to prograde (i.e., solubility increased considerably with increasing temperatures). The solubility of Na2SO4 in the measured solution was significantly higher than that predicted in the absence of SiO2 over the entire temperature range (except for temperatures around 313°C). This indicates that the presence of SiO2 greatly changes the dissolution behavior of Na2SO4, which may be caused by the formation of a sulfate-silicate intermediates such as Si(OH)4SO42-. Considering that most crustal fluids are silica-saturated, the solubility curve of Na2SO4 obtained in this study can better reflect the characteristics of geofluids when compared to that of Na2SO4-H2O binary system. At temperatures of 313-425°C, the solubility of Na2SO4 increases with temperature following the function Csulfate=-3173.7/T to +5.9301, where Csulfate and T represent the solubility of Na2SO4 in mol/kg H2O and temperature in Kelvin, respectively. As an application, this temperature-solubility relationship can be used to evaluate the sulfate contents in fluid inclusions that contain sulfate daughter minerals, based on the temperature of sulfate disappearance obtained from microthermometric analysis. The sulfate concentrations of the ore-forming fluids of the giant Maoniuping carbonatite-related rare earth element (REE) deposit (southwest China) were calculated to be 4.67-4.81 m (mol/kg H2O). These sulfate concentrations were then used as internal standards to calibrate the previously reported semi-quantitative results of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of REE-forming stage fluid inclusions at this deposit. The calculated Ce concentrations in the REE-mineralizing fluid range from 0.42 to 0.49 wt%. The high fluid REE contents suggest that the sulfate-rich fluids are ideal solvents for REE transport. A mass-balance calculation was carried out to evaluate the minimal volume of carbonatite melt that was required for the formation of the giant Maoniuping REE deposit. The result indicates that the carbonatite dikes in the mining area are enough to provide the required fluids and metals, and thus a deep-seated magma chamber is not necessary for ore formation.
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•A revised method for zircon pressure sensor.•It is applicable for zircon with different ambient wavenumber and composition.•Synthetic zircon can determine pressure in fused silica ...capillary capsule (FSCC).•Thick-walled FSCC can be treated as an isochoric system below ~480 °C.•Thin-walled FSCC cannot be treated as an isochoric system even at low temperature.
The Raman shift of the ν3(SiO4) mode of zircon at ~1008 cm−1 has been observed to vary with the pressure (P) and temperature (T) of the environment. The relationship between the ν3(SiO4) peak position and P-T was calibrated in previous work and used to develop a pressure sensor for high P-T experiments, up to 1000 °C and 10 GPa, to an accuracy within ±50 MPa. This pressure measurement method is valid for zircon grains for which the ν3(SiO4) Raman shift occurs specifically at or close to 1008.17 cm−1 at room temperature (25 °C). However, the peak position of ν3(SiO4) for some zircon grains may shift to a lower or higher wavenumber under ambient conditions, mainly due to the chemical composition of the grains. This may cause substantial deviation in the measured pressures. In the present study, we recalibrated the pressure sensor by determining the position of the ν3(SiO4) peak for zircon grains with different chemical compositions at given P-T conditions and developed a model applicable to both natural and synthetic zircon samples. All the zircon samples considered were found to have a universal ν-T relationship when the ν3(SiO4) wavenumbers under ambient conditions were calibrated to the same position. Based on this relationship, the temperature-induced wavenumber shift of ν3(SiO4) can be expressed as ΔνT (cm−1) = 8.00 × 10–9 × (T3 – T03) – 2.00 × 10–5 × (T2 – T02) – 2.78 × 10–2 × (T – T0), where T and T0 are the target and room temperatures, respectively. In addition, the pressure-induced wavenumber shift of ν3(SiO4) can be calculated using ΔνP (cm−1) = Δν – ΔνT, where Δν is the total frequency shift between the target and ambient P-T conditions. By the linear regression of the experimental results, the global slope (∂ν/∂P)T was determined to be 5.91 × 10–3 cm−1/MPa. In addition, high P-T experiments performed in isochoric systems using a hydrothermal diamond anvil cell (HDAC) showed that the cross-derivative term (∂2ν/∂P∂T) was equal to zero, which is the same as the previous study. The revised method was used to determine the pressures inside a fused silica capillary capsule (FSCC) containing a NaCl solution. The pressures determined from the zircon Raman spectra (PZr) were compared with those calculated using the equation of state (PEoS) of a NaCl-H2O system. The determined PZr and PEoS values agreed well for temperatures lower than ~500 °C. However, PZr was significantly lower than PEoS at higher temperatures due to the thermal expansion of the FSCC, i.e., the expansion of the sample chamber under the high internal pressures when the silica glass softened at high temperatures. The revised method was programmed in a Microsoft EXCEL spreadsheet and is presented in the Appendix B.
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•A method to predict the Th of easily decrepitated fluid inclusions is proposed.•This method can be applied to H2O-NaCl and H2O-CO2-NaCl inclusions.•The errors of estimated Th are ...within ±5 °C for most inclusions.•Good accuracies of Th prediction are expected for inclusions bigger than ~20 μm.
Measuring homogenization temperature (Th) is a basic work in fluid inclusion studies. However, the Th of some fluid inclusion is hard to obtain using the traditional microthermometric method, in particular those that is easy to decrepitate upon heating. Such inclusions are common when the host minerals have well-developed cleavages (e.g., calcite and fluorite) and the fluids are enriched in volatile components such as CO2 or CH4. In theory, upon heating of H2O-NaCl and H2O-CO2-NaCl inclusions that tends to homogenize to the liquid phase, their bubble volumes (Vg) will decrease with increasing temperatures (T) following cubic and quartic polynomial Vg-T functions, respectively. A method that can predict inclusion Th without heating it to homogenization is proposed in this study. The core idea is to retrieve the Vg-T function of a given inclusion based on a series of (Vg, T) data points that were measured before total homo genization (or decrepitation of the inclusion), and then calculate the Th based on the function (the temperature at which Vg equals to zero). To test the performance of this method, a total of 14 synthetic and natural fluid inclusions were heated to homogenization (at Th, real) and their changes in Vg were recorded with increasing temperature. It is assumed that the inclusions get decrepitated before homogenization, and their homogenization temperatures were predicted (Th, predicted) using the method proposed by this study. If the inclusions were “decrepitated” at temperatures 40 °C below the Th, real, the differences between the predicted and real homogenization are mostly smaller than 3 °C. This approach provides a quantitative estimation of the Th for inclusions that are easy to decrepitation, and is much more accurate than directly using the temperature of decrepitation as an approximation of Th. This method was programed in two Microsoft EXCEL worksheets that are available in Supplementary Materials for Th calculations of H2O-NaCl and H2O-CO2-NaCl inclusions, respectively.
In recent years, it is in a special period of agricultural transformation in China. As the living concept and the requirements for living space have been making a great shift, the traditional ...settlement space can no longer satisfy the modern agricultural production and living needs any more. Taking the earth dwellings in Gannan as the research object, this paper studied on changes of the traditional dwellings and the renewal methods of native earth dwellings. Based on a lot of investigation and interviews, the paper analyzed the transition of the construction material, techniques and the experiences about how to use and adapt to the nature during the traditional dwellings construction.
Raman spectroscopy is a crucial technology in geoscience and often employed in in situ quantification experiments to investigate fluid compositions at elevated temperatures. Raman spectroscopic ...quantification is fundamental to understanding the hydrothermal behaviors of aqueous species, such as SO42− and H3PO40. Considering that SO42− and PO43− are closely associated with metal transportation and deposition, investigating the hydrothermal behaviors of these species, via Raman spectroscopic quantification, can give an assistance for the comprehension of relative ore-forming processes. During Raman spectroscopic quantification, the accuracy of the calibration coefficient (k), which bridges the concentration of a species (Cspecies) and its Raman peak area (Anormalized) in the form of Cspecies = k · Anormalized, is the key to accurate measurement of fluid composition. For high-temperature experiments, quantification of fluid composition is complicated because the coefficient k varies with varying temperatures. In this study, the temperature dependence of the calibration coefficients is retrieved, based on experiments on solutions containing SO42− and H3PO40 using the fused silica capillary capsules. The results show a well-established linear relationship between the k and 1/T (absolute temperature in Kelvin) for both SO42− and H3PO40. The reported linear k − 1/T relationship simplifies Raman-based fluid composition investigation at elevated temperatures: the k values throughout the whole temperature range of interest can be retrieved by measuring the room-temperature Raman intensity of a standard sample (i.e., with known composition) and one single data point at high temperature. We speculate that this linear k − 1/T relationship method may be established for other species (e.g., carbonate ions) and can be applied for experiments using other technics (e.g., hydrothermal diamond anvil cell) or retrieving the compositions of natural or synthetic fluid inclusions. For example, the empirical linear relationship can facilitate the measurements of gas concentrations (e.g., CO2) in natural fluid inclusions.
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•An empirical method in Raman spectroscopic quantification.•The coefficient (k) shows linear relationship with 1/T (absolute temperature).•The linear relationship can be used in in situ fluid composition investigation.
Sulfate-bearing hydrothermal fluids are widespread in crustal environments, and recent papers highlight a possible important role of sulfate as an agent for mass and electron transfers in subduction ...zone. The geochemical characters of sulfate-bearing fluids (e.g., ability of complexing with ore-forming elements) depend largely on the dissociation behavior of HSO4−. However, the dissociation of HSO4− was only investigated at vapor saturation pressures and the pressure dependence of the dissociation behavior is thus unclear. In this study, we modified the fused silica capillary capsule (FSCC) method to explore the dissociation behavior of HSO4− quantitatively via in situ Raman spectroscopy experiments. We designed a new heating stage that can accommodate a 7 cm-long FSCC, and we show that thick-walled FSCCs with high degrees of filling can withstand pressures up to 645 MPa at temperatures to 450 °C. The sulfate concentrations in Cs2SO4–H2SO4 solutions were measured using Raman spectroscopy with increasing pressures and temperatures (P–T). The sulfate concentrations were calibrated using Cs2SO4 solutions with known concentrations, and the concentrations of HSO4− were determined by mass balance. According to our experimental results, increasing pressure increases the dissociation of HSO4− into SO42− and H+ while increasing temperature promotes ion association, which means that HSO4− dissociation is favored in high-density fluids. Comparisons between our experimental results with those of thermodynamic predictions using currently available thermodynamic properties indicate that the dissociation of HSO4− is stronger than previously thought in high-density fluids, especially at high pressures. We then optimized the thermodynamic properties of HSO4− based on our experimental results, and used them to simulate the S(VI) speciation in slab-derived fluids. Similar with our experimental results, the simulations also predict that the HSO4− will largely dissociate into SO42− and H+ in fluids with high P–T conditions, causing the SO42− as the predominant S(VI) speciation in subduction zone.
Sulfate-bearing geofluids are widespread in many geological environments and play important roles in ore-forming processes. Recent experiments provide evidences that in silica-rich fluids, Na2SO4 ...solubility exhibits a complex temperature dependence, first decreasing from 25 to 313 °C and then increasing from 313 to 425 °C. The fluid-borne silica have critical implications for sulfate-bearing hydrothermal systems and formations of rare earth element deposits. However, whether other sulfate salts share the same characteristics remains unknown.
In this study, fused silica capillary capsules (FSCCs) containing K2SO4-saturated solutions and K2SO4 crystals are used to quantitatively investigate the solubility of K2SO4 at different temperatures in the K2SO4-SiO2-H2O system. In the K2SO4-SiO2-H2O system, K2SO4 shows prograde solubility from 50 to 400 °C, and does not melt through the whole investigated temperature range. The relationship between temperature and the solubility of K2SO4 can be described by a simple linear function with R2 = 0.991: Csulfate = 4.1307 × 10−3 × T + 0.5532, where Csulfate and T represent the solubility of K2SO4 in m (mol/kg H2O) and temperature in °C, respectively. These results show that the solubility of K2SO4 can be enhanced by 3 to 5 times at 300–400 °C by the presence of silica, compared with that in silica-absent system, even without the formation of sulfate melt. Considering that quartz is ubiquitous in the Earth's crust, the solubility of sulfate in natural geofluids may reach a much higher level than previously expected.
The temperature dependences of the solubilities of K2SO4 and Na2SO4 in silica-saturated fluids were used to constrain the compositions of the mineralizing fluids of the synmetamorphic hematite-quartz veins at Ouro Fino (SE Brazil) and the Maoniuping REE deposit (SW China), based on the previously reported microthermometric results of fluid inclusions that contain sulfate daughter minerals. For the hematite-quartz vein at Ouro Fino, the sulfate concentration was calculated to be 8.9–19.2 wt%, which is in line with previous laser ablation measurements (~15.3 wt%). For the Maoniuping REE deposit, the total sulfate concentration was determined to be 16.3–27.4 wt%, and the REE concentration of the ore-fluid was further estimated to be 0.30–0.44 wt%.
•Potassium sulfate exhibits prograde solubility in the presence of silica.•Presenting solubility of K2SO4 in silica-saturated fluids at 50–400 °C•Evaluating REE contents in ore-fluids of the Maoniuping deposit
Pursuing smart traffic systems for non-motorized users has been becoming more important in the past few years. Non-motorized road users are requiring more efficient and user-friendly infrastructure ...facilities with improved equity, especially at the intersection areas. However, most existing achievements in this field either proposed overcomplex solution and led to lacking reliability and scalability, or proposed something that were not keeping pace with time enough to improve users’ accessibilities. Therefore, in this research, a new system is proposed to replace the traditional push-button switch or traffic lights. The system utilized a roadside device as the communication media between signal controller and user, and users only need to install a mobile phone app to use the system. Compared to existing similar solutions, our solution introduced a smart gateway to achieve multiple protocols integration. The proposed phone app that can also classify users according to their motions, different non-motorized user groups can now easily view their waiting time and sending crossing request manually or automatically without searching for the physical push-button switch and press it. Our experiments indicates that our system is a touch-free, quick responding, reliable and highly accessible for all user groups. In addition, this proposed system is the first equity-aware solutions for both normal and vulnerable users and can completely replace the traditional physical push-button system.
The association between pre–intracerebral hemorrhage (ICH) statin use and clinical outcomes after intracerebral hemorrhage (ICH) is still conflicting. Recently, some studies investigating the effects ...of in-hospital statin use after the onset of ICH have been published. To provide a more complete picture of the clinical effects of statin use in ICH, we performed a systematic review to examine whether statin use influences clinical outcomes.
We conducted a systematic review of literature in the Cochrane Library, MEDLINE, EMBASE, and the China National Knowledge Infrastructure database.
Twenty-one studies were included in our systematic review. Meta-analysis of 12 studies suggested that pre-ICH statins use did not significantly decrease mortality when aggregated across all time points tested—that is, in-hospital or at 30 or 90 days (odds ratio OR, 0.85; 95% confidence interval CI, 0.70–1.03). Meta-analysis of 7 studies suggested that pre-ICH statins use did not significantly affect poor functional outcomes, defined as a modified Rankin Scale (mRS) score of 3–6 (OR, 0.93; 95% CI, 0.72–1.18) or mRS score of 4–6 (OR, 0.92; 95% CI, 0.60–1.40). Meta-analysis of 7 studies suggested that in-hospital statin use significantly decreased mortality when aggregated across all time points tested (OR, 0.37; 95% CI, 0.28–0.50). Statin discontinuation was independently associated with poor clinical outcome.
The patients with pre-ICH statin use did not improve clinical outcomes. However, in-hospital statin use can significantly decrease mortality after ICH. In-hospital statin therapy might be beneficial for patients with ICH.
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