Search

The Jinzhuping and Changkeng granites are related to the Helong W–Sn ore field in southern Jiangxi Province, China. Three different phases can be found in the Jinzhuping pluton, and their LA-ICP-MS zircon U–Pb ages are 155.2 ± 0.68 Ma, 154.0 ± 0.56 Ma, and 153.4 ± 0.99 Ma, respectively, indicating two types of granitic rocks. All granites in the Helong ore field have similar geochemical characteristics, they have high contents of SiO2 (73.99 wt.%–77.68 wt.%), and total alkali (7.56 wt.%–8.76 wt.%) and are weakly to strongly peraluminous. They are slightly enriched in HREE and depleted in Eu, Ba, Sr, P, and Ti. Zircon εHf(t) values of the Jinzhuping three granites are from −14.4 to −10.4, from −15.3 to −11.4, and from −18.1 to −10.5, and the Hf TDM model ages range from 1.83 to 2.06 Ga, from 1.89 to 2.14 Ga, and from 1.83 to 2.31 Ga, respectively. Whole-rock geochemistry and Hf isotope analysis indicate that the Helong granites experienced a high degree of differentiation and evolution derived by partial melting of the Late Paleoproterozoic crustal materials, and they formed in a backarc caused by low-angle subduction of the Paleopacific plate. [ABSTRACT FROM AUTHOR]

Vacuum interrupter is widely used in the medium-voltage power system. Controlling the arc by the magnetic field is an effective method to improve the breaking capacity. The transverse magnetic field (TMF) forces the constricted arc to rotate to reduce local overheating. In this paper, three kinds of TMF contacts, which are Swastika-type contact, cup-shaped contact, and double-TMF contact that combines Swastika-type and cup-shaped contacts coaxially, are investigated in a demountable vacuum chamber with a high-speed camera. The arc voltage and current are also recorded. The experiments were conducted with circuit currents from 5 to 20 kA (root mean square) with a frequency of 50 Hz. There are four current levels in the experiment, which are 5, 10, 15, and 20 kA, and at least three tests are taken for each current level. The results showed that under low current (I = 10 kA), the arc of the three TMF contacts did not rotate. Under high current (I = 20 kA), it was observed that the arc of Swastika-type and double-TMF contacts rotated in the gap. The arc speed of double-TMF contacts is higher than that of Swastika-type contacts. The cup-shaped contacts have the highest arc voltage and noise among the three TMF contacts. The Swastika-type contacts were eroded most seriously. The simulation results show the force distribution of the arc on different locations. The resultant force makes the arc rotate counterclockwise. [ABSTRACT FROM AUTHOR]

Using magnetic fields to control the vacuum arc is a major way to improve the breaking capacity of vacuum interrupters. Besides the single transverse magnetic field (TMF) and single axial magnetic field (AMF), new type of TMF-AMF contact and TMF-TMF contact structures have been put forward to control the vacuum arc in recent years. In this paper, three different structural contacts are used in the experiments. The arc evolution was captured by an high-speed digital video camera, and at the same time, the arc current and arc voltage wave were recorded. The experiment was conducted under current ranging from 5 to 20 kA (root mean square) and 10 mm of gap distance. There are 12 current shots performed on one contact design. There are four current levels in the experiment which are 5, 10, 15, and 20 kA, and three tests are taken for each current level. The results showed that for TMF-AMF contacts, under low current (I = 5 or 10 kA), the arcs of the two kinds of contacts both kept diffused and rotating. Under high current (I = 20 kA), the arc of the TMF-AMF contact with six slots was constricted and rotated on the plate, and the melting was uniform and slight. As for the eight-slot contacts, the arc was constricted but did not rotate which resulted in significant melting in the local region. As for TMF-TMF contacts, the result is similar under low current, while the arc was constricted and rotated quickly on the inner plate under high current. The simulation results show that when the arc core is located on the outer plate; the total Lorentz force is near zero. When the arc core is located on the inner plate, the direction of total force is counterclockwise. [ABSTRACT FROM AUTHOR]

• It is the first review to compile FT-ICR-MS results for DOM in water treatments. • EEM-PARAFAC and FT-ICR-MS are two powerful tools for characterizing DOM. • The high diversity of DOM composition is a major challenge for water treatments. • Effects of water treatments on DOM are largely dependent on the DOM composition. • The DOM composition and its removal is key to optimize the treatment processes. Dissolved organic matter (DOM) plays a critical role in determining the quality of wastewater and the safety of drinking water. This is the first review to compare two types of popular DOM monitoring techniques, including absorption spectroscopy and fluorescence excitation-emission matrices (EEMs) coupled with parallel factor analysis (PARAFAC) vs. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), for the applications in wastewater and drinking water treatments. The optical techniques provide a series of indices for tracking the quantity and quality of chromophoric and fluorescent DOM, while FT-ICR-MS is capable of identifying thousands of DOM compounds in wastewater and drinking water at the molecule level. Both types of monitoring techniques are increasingly used in studying DOM in wastewater and drinking water treatments. They provide valuable insights into the variability of DOM composition in wastewater and drinking water. The complexity and diversity of DOM highlight the challenges for effective water treatments. Different effects of various treatment processes on DOM are also assessed, which indicates that the information on DOM composition and its removal is key to optimize the treatment processes. Considering notable progress in advanced treatment processes and novel materials for removing DOM, it is important to continuously utilize these powerful monitoring tools for assessing the responses of different DOM constituents to a series of treatment processes, which can achieve an effective removal of DOM and the quality of treated water. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Previous researches focused on dry sample thermal treatment to enhance rock permeability indicate that thermal treatment can be a novel stimulation technique for geothermal and hydrocarbon reservoirs development. The mechanicm of thermal permeability enhancement depends on the generation of microcracks by thermal cracking. In this study, chemical solutions were introduced on sandstone rock samples and observed that they can be used to control thermal permeability enhancement. Sandstone specimens with the same order of permeability were saturated with different salt solutions and heated to different temperatures. The results quantify permeabilities and porosities of specimens saturated with electrolyts over them without chemical treatment but heated to the same temperature. The KCl solution had the largest effect on permeability enhancement for the tested rock and showed a tenfold increase in permeability, and followed by NaCl and K 2 CO 3 solutions. However, CaCl 2 solution and distilled water had negative effects. Laboratory results also revealed a positive correlation between some chemical concentration with the permeability increment of rock. The effects of electrolyte type and concentration on thermally permeability enhancement of the tested rocks were determined and a statistical model was fitted. The results show that the permeability increment follows an exponential growth with temperature when the rock was heated over the threshold temperature of thermal cracking. Introducing specific chemical species into a low-permeability formation and heating the formation beyond the threshold temperature of rock thermal cracking will be a promising way to further enhance formation permeability. • Reservoir rocks saturated different chemical agents were heated at high temperature. • Saturated rock has larger potential in permeability enhancement than dried one. • Types and concentrations of chemical agents largely affect the degree of rock thermal cracking. • Thermal stimulation with chemical agent is a promising way to enhance reservoir permeability. • An exponential growth model for permeability increment is proposed. [ABSTRACT FROM AUTHOR]

The Jenkyns Event (~183 Ma) represents an exceptional warming period in the Jurassic, which is characterized by intense environmental and climate perturbation. The eruption of the Karoo‐Ferrar Large Igneous Province (K‐F LIP) triggered pronounced carbon isotope negative excursion (N‐CIE) in exogenic carbon reservoirs, global widespread organic carbon burial and extensive ocean anoxia. However, the synchronic coupling relationship between the carbon release, volcanic activity, and intense weathering induced by the K‐F LIP during this period remains poorly understood. In this study, detailed sedimentologic and geochemical studies were conducted on the terrestrial stratigraphy of the Lower Jurassic Fuxian Formation in the Ordos Basin. Three spore‐pollen assemblages have been identified, with the Cyathidites‐Deltoidospora‐Chasmatosporites assemblage suggesting a Pliensbachian age, the Classopollis‐Cycadopites‐Chasmatosporites assemblage indicating an early to middle Toarcian age, and the Cyathidites‐Cycadopites‐Psophosphaera assemblage indicating a late Toarcian age. The lower part of the Classopollis‐Cycadopites‐Chasmatosporites assemblage shows a negative CIE with a magnitude of 2.7‰, accompanied by organic carbon enrichment. Mercury concentrations and Hg/total organic carbon ratios also show peaks during the initial stage of the carbon isotope negative shift, implying a synchrony between volcanic activities and carbon perturbation. Furthermore, the Chemical Index of Alteration value has reached its maximum and the kaolinite content shows a sharp increase at the same position as the carbon isotope negative shift initiation, indicating a simultaneous enhancement of continental weathering during volcanic activity. The changing patterns of the continental weathering intensity encompassing the Jenkyns Event also indicate that continental weathering may have functioned as a significant approach to counteract the greenhouse effect caused by substantial volcanic CO2 emissions. [ABSTRACT FROM AUTHOR]

Creating a good fracture network in hot dry rocks is the key to the success of an Enhanced Geothermal Systems project. Instead of creating large-scale fractures, the proposed thermal stimulation method has clear advantages by generating small-scale cracks, increasing crack density, and forming fracture networks in tight rocks. Granite samples from a tight formation in Lijin County in China were thermally treated at various temperatures to evaluate the permeability enhancement and the feasibility of thermal stimulation. Scanning electron microscope (SEM) method was also used to investigate the changes in interior structure in granite rocks. The experiments show that the threshold temperature of Lijin granites is around 300°C, the permeability can improve approximately 2 orders and the porosity can increase more than 5 times when heating over 600°C. Both crack length and width increase about 10 folds under the experiment conditions, and the original mineral disappearance and new mineral generation were observed. Thermal cracking under high temperatures plays a key role in permeability and porosity enhancement. Numerical simulation results show that the heated zone is very limited if only heating in a borehole. To expand the affected zone and improve energy recovery, a new thermal stimulation method combining microwave excitation with proppants to heat inside hydraulic fractures is proposed and discussed. [ABSTRACT FROM AUTHOR]

In order to improve the breaking capacity of contacts, it is very important to find a better contact material. In this paper, the triggering experiments of plate contact with different materials are studied to investigate the characteristics of vacuum arc. The current range is from 1 to 9 kA (rms). The gap distance is selected as 3 and 5 mm. The arc appearance and the behavior of cathode spots are captured by high-speed camera with an exposure time of $2~\mu \text{s}$. The surface topography of contacts after experiments is evaluated by scanning electron microscope. The arc current and arc voltage are measured at the same time by Rogowski coil and high-voltage probe. The diameter of the contact is 25 mm. There are seven kinds of materials (CuCr10, CuCr25, CuCr30, CuCr40, WCu10, WCu30, and CuW–WC) conducted in this paper. Compared with the experimental results, the arc of WCu alloy distributes more evenly on the contact plane with many bright cathode spots. The small gap distance makes the burning point more fixed. The arc of CuW–WC is unstable. During the arc trigger moment to the arc stable burning stage, the radial diffusion velocity of WCu10 cathode spot is the lowest with about 25% of CuCr10. CuCr10 alloy has the worst melting resistance. WCu alloy has good melting resistance and bad toughness. The toughness of CuW–WC is even worse. Under the low current, CuCr30 might be preferred for vacuum interrupters from the cathode spots’ radial diffusion speed, arc appearance, and erosion result. When the current increasing, the arc can easily spread to the entire surface of WCu contact, and WCu10 would be the prefer material with the diffusion arc and good erosion resistance. [ABSTRACT FROM AUTHOR]

As a special phenomenon under transverse magnetic field (TMF) contacts, vacuum arc rotation deserves more attention. In this article, rotation characteristics of three typical TMF contacts, i.e., swastika-type, cup-shaped, and double-TMF contacts, are systematically studied. According to arc images, recorded by a high-speed camera, physical terms related to arc rotation such as rotation duration and rotation speed are clearly defined. The magnetic field and Lorentz force are calculated and the force balance of the moving arc is analyzed. On this basis, the effects of arc ignition mode, peak current, and contact type on arc rotation are investigated. Arc voltage noise as well as arc splashing outside caused by rotation is also discussed. The results show that the duration from ignition to rotation in two-point arc ignition (TPAI) mode is usually the shortest because of the rapidest constructed column formation. As the peak current increases, arc rotation becomes easier. Due to stronger TMF, the arc under double-TMF contacts has the longest rotation duration and the highest rotation speed. [ABSTRACT FROM AUTHOR]

• The wavelength 1455 nm is important for the mineralization. • Silicification variation can indicate the fluid flow direction. • Illite crystallinity is associated with mineralization and metallogenic environment. • Illite mapping with SWIR can judge whether low sulfidation epithermal deposit is. Field measurements using shortwave infrared (SWIR) reflectance from drill hole samples provided an effective method to map variations in illite crystallinity and the illite assemblage minerals associated with hydrothermal alteration zonation of the Sinongduo low sulfidation epithermal Ag-Pb-Zn deposit, Tibetan Plateau, China. The SWIR mineral spectral information was combined with electron probe micro-analysis (EPMA) measurements, and microscope observations to provide geological insights into: (a) the likely metallogenic fluid nature of the mixture of magmatic fluids and a cooler water source; (b) the illite physico-chemical properties of the associated hydrothermal fluids; (c) the illite, montmorillonite and sericite evolutionary interactions among these fluids, country rocks, and alteration minerals; and (d) the alteration minerals relationships and illite crystallinity to the economic mineralization. The results suggest that illite characterizations can be used as an indicator for epithermal deposit prospecting. [ABSTRACT FROM AUTHOR]

In this paper, the arc characteristics of cup-shaped AMF contacts in vacuum arc experiments under different materials was studied. The experiment was conducted in a detachable vacuum chamber with a gas pressure of 10-4Pa. The arc voltage and current were measured at the same time by high-voltage probe and Rogowski coil, and the arc pictures were photographed with a high-speed camera. The cup and the rod of the contact are made of pure copper material, and the contact pieces are selected ten common contact materials for comparison (CuCr10, CuCr 20, CuCr 30, CuCr 40, CuCr 50, WCu10, WCu20, WCu30, CuW-WC). Fixed-distance trigger experiments were conducted with currents of 5kA (rms), 10kA (rms), and 15kA (rms) for each contact. The arc appearance, cathode surface morphology, and anode status morphology were observed. The shape of the arc was analyzed in conjunction with the voltage and current after the experiment. The morphology of cathode and anode surface was analyzed by combining the erosion after the experiment. The effect of various material properties was discussed under the AMF. It's found that the center of the anode erosion area is approximately hexagonal, and the slot is burned more outward than the plane. WCu contact has better erosion resistance than CuCr contact. For CuCr, the erosion of CuCr30 is the slightest with low depth and small area. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorite at Qulong includes three types of chlorite veins and disseminated chlorite. • The chlorite co-existing with Cu mineralization is high Fe with long wavelength. • The ore fluid evolved to be more acidic and higher silica activity over time. • SWIR and chlorite geochemistry can be combined for porphyry exploration in orogen. The genetic mechanism and exploration model for porphyry deposits in subduction zones has been comprehensively and systematically investigated; in contrast, our understanding for porphyry mineralization in collisional orogeny is limited. Qulong porphyry Cu-Mo deposit, a typical porphyry Cu deposit (PCD) developed in the collisional setting, was chosen as the subject of this study. The study is mainly focused on interpretation of short-wave infrared (SWIR) spectroscopy combined with mineral geochemistry of chlorite from Qulong deposit to guide exploration in future. Hydrothermal alteration in Qulong mineralization system can be divided into three zones, which are the inner potassic alteration zone, the outside propylitic alteration zone and phyllic alteration. Phyllic alteration can be intensively superimposed on the early potassic and prophylitic alteration zones. Chlorite is widely distributed in both of the propylitic and phyllic zones. Four types of chlorite were observed in Qulong deposit, including three stages of vein-related chlorite (Chl-I, Chl-II, Chl-III) and one type of disseminated chlorite (Chl-D). Mineral assemblage of Chl-I stage includes chlorite–anhydrite–pyrite. Minerals in Chl-II stage consist of chlorite–epidote–pyrite–chalcopyrite. Mineral assemblage of Chl-III stage is composed of chlorite–sericite–quartz–chalcopyrite, which is later than both Chl-I and Chl-II. Chl-D was developed mainly by alteration of primary biotite phenocryst. Chl-I, Chl-II and Chl-D were formed along with the propylitic alteration; however, Chl-III is from the phyllic alteration. Chl-II and Chl-III are both closely related with Cu mineralization. The major element compositions of chlorite show a regular variation of Mg# with fluid evolution. Transition from shorter wavelength chlorite (Fe feature around 2250 nm) to longer wavelength goes with the decrease of Mg#, except for Chl-D. In summary, chlorite associated with Cu mineralization in Qulong is mainly occurred in veins and has low Mg# ratios and longer wavelength. Such chlorite is the indicator for Cu mineralization and should be the target in future exploration. In addition to chlorite, sericite in Qulong also shows systematic change from early-stage phengite to late-stage muscovite. In combination of mineral geochemistry and thermodynamic modelling, we suggest that ore-forming fluid gradually evolved to be more acidic with higher silica activity over time. [ABSTRACT FROM AUTHOR]