Features Of Arc Research Articles

Issues of ensuring the resistance of high-voltage solar arrays of spacecraft to the effects of secondary arc discharges

We have considered the issues of ensuring the resistance of high-voltage solar battery (SB) of spacecraft to the effects of secondary arc discharges. Research in this area has been going on for more than 50 years, but the answer to all the questions has not yet been found. First of all, this is due to the complexity of the electrophysical processes occurring on the surface of the spacecraft in space and in laboratory conditions. The second reason is the random nature of secondary vacuum arc discharges, which requires the use of special test methods to confirm the effectiveness and reliability of selected design and technological solutions. Tests in conditions close to full-scale conditions do not allow us to solve this problem. We have given a retrospective review of publications on the physical features of secondary arcs arising on SB of spacecraft, the mechanisms of their initiation, experimental research and testing methods. We paid considerable attention to the issues of the occurrence of secondary arc discharges SB of the spacecraft in the conditions of ionospheric plasma and plasma generated by electric propulsion thrusters. We have shown that despite the large amount of accumulated data and knowledge, the transition from low-voltage SB to high-voltage SB remains a difficult scientific and technical problem, which requires additional research to solve. In addition, it is already necessary to start training personnel who possess a wide range of knowledge and are able to work on this topic. To do this, it seems advisable to organize sectoral research, as well as the allocation of targeted funds for the training of highly qualified specialists and their independent research. This approach will make it possible to solve the problem of creating high-voltage SB in the shortest possible time and prepare personnel for the development of this technology.

To the question of construction of welding inverter sources with a high power factor

Purpose. Design a power-factor-corrected, energy- and cost-efficient switchmode power supply for welding. Methodology. It is proposed to use the principle of direct conversion and to develop the "hybrid" power circuit consisting of a main power path using direct conversion and an auxiliary power path having a converter with an intermediate DC link with relatively low stored energy. Since a load to the welding power supply is the welding arc, its instantaneous power fluctuations during the mains voltage period essentially do not influence the welding process due to the thermal constant of the weld pool molten metal. Effective use of this features of the welding arc allows to optimize the power processing, reduce the amount of energy stored in the reactive elements of the circuit and improve the economical, mass and dimensional parameters of the supplies. Findings. A new power factor corrected switchmode power supply topology is proposed utilizing beforementioned principles of power processing. The algorithm for calculating the switching frequency of supply power switches is given. To confirm the adequacy of the developed provisions, an experimental sample of the power supply was created. Oscillograms of mains voltage and source current consumption and oscillograms in output current limitation mode are obtained. The results of experiments showed that the supply has a power factor > 0.94 in a wide range of powers. Originality. A distinctive feature of the supply is the absence of additional inductive components in the power path, a lower capacitance of the DC-link bulk capacitor and a simplified scheme for limiting its inrush current during initial charging. The supply has an increased open circuit voltage, independent of the mains voltage, which allows for easy arc ignition during manual arc welding. Practical value. Due to the increased power factor, the current drawn from the mains is 30 % to 45 % lower than that of widespread inverter supplies without a power factor corrector. These features allow to simultaneously use more power supply units with the same mains current load, and/or to provide stable welding in conditions of a "weak" mains.

Research on Online Measurement Method for Small Workpiece Circular Holes Based on Machine Vision

<p>In modern manufacturing, due to the narrow format, short size, and complex surface structure of small-sized workpieces, automatic detection of surface defects, dimensions, etc. on small-sized workpieces faces difficulties, making it difficult to meet the requirements of fully automated production lines. Especially, there is no good solution to the problem of high-precision automatic measurement of geometric features of circles and arcs on small-sized workpieces. This article takes the engine end cover circular hole thermal component as the research object, builds a hardware platform for image acquisition of small-sized workpieces based on machine vision, proposes an online size measurement method for small-sized circular holes, and realizes the measurement of the position size and aperture size of small-sized product shell workpieces. In order to achieve the above methods, this article builds a visual detection hardware system and describes a detailed machine vision hardware selection scheme. Then, the images collected by the system are preprocessed, including image denoising, image correction, and image feature extraction. Then, for the processed images, an improved Hough transform fitting method is used to obtain the online size of features. In order to visualize the results, the detection system and software are designed according to the actual application scenario. The overall scheme of this article is efficient and reasonable, and the detection result error is within a reasonable range.</p> <p> </p>

Permian tectonic switch of the southern Central Asian Orogenic Belt: Constraints from magmatism in the southern Alxa region, NW China

Abstract Late Paleozoic plutons are widely distributed in the Alxa region, southernmost Central Asian Orogenic Belt, and provided an important clue in constraint for the closing time of the Paleo-Asian Ocean (PAO). In this article, we present new zircon U-Pb ages and whole-rock geochemical data from the Permian Huoersen and Zongnaishan plutons in the southern Alxa region. The Huoersen gabbro (ca. 285 Ma) is enriched in large-ion lithophile elements and depleted in high-field strength elements, similar to the features of continental marginal arc. They were most likely generated by partial melting of depleted mantle that was modified by subduction metasomatic fluids. The Zongnaishan granites (ca. 267 Ma) show characteristics of I-type granites and were generated in a syn-collision setting. The Huoersen granites (ca. 259 Ma) are peralkaline and have positive Ɛ Nd(t) (+1.2 to +1.5) values, exhibiting A2-subtype granites affinities. They were formed by melting of lower crust in post-collision extension setting. Based on geodynamic mechanism, a three-stage evolution model is delineated: subduction, syn-collision to post-collisional extension for oceanic branch of the PAO during the Permian. In general, the rock assemblages indicate a tectonic switch from subduction to post-collision extension regimes and the final closure of the PAO.

РОЗРОБКА ТА ДОСЛІДЖЕННЯ МОДЕЛІ ПІД-РЕГУЛЯТОРА НАПРУГИ ДУГИ ПІД ЧАС НАПЛАВЛЕННЯ

The development and testing of a PID-controller model capable of automatically adjusting and maintaining the specified arc voltage during electric arc welding are presented. Some features of arc surfacing processes are analyzed. In particular, the choice of surfacing modes, as well as the main devices - potentiometers, which are used in the electrical circuits of surfacing installations to regulate the main parameters of surfacing modes - voltage and current. Evidence is presented for the need to control the voltage directly on the arc, rather than the voltage on the power source, to regulate the welding process. Based on this analysis, a model of the PID- controller of the arc voltage during arc welding was created using the Simulink MATLAB program. The test results of the PID-controller show that the device provides more accurate and stable setting of the deposition mode than traditional control methods. The PID-controller will make it possible to significantly reduce possible errors in the development and use of technologies of automatic arc welding of various parts and products. References 10, figures 6, table 1.

Geochemical comparison between oceanic and continental arc volcanic rocks: Insights to arc magmatism

Compositional differences between continental and oceanic arc volcanic rocks have long been recognized; however, our understanding of them is incomplete. This study presents a comprehensive geochemical comparison, including major, trace and Sr–Nd–Pb isotope compositions, between global continental and oceanic arc volcanic rocks. Our data compilation reveals that volcanic rocks from a single oceanic arc occupy basaltic to basaltic–andesitic average lithochemical compositions, except for volcanic rocks from the Lesser Antilles arc, which occupies an andesitic average lithochemical composition, similar to the bulk composition of volcanic rocks from single continental arcs. The composition of the average continental arc volcanic rocks, the average Lesser Antilles arc volcanic rocks and the average oceanic arc volcanic rocks are different in many ways, which span the entire compositional range from basalts to rhyolites, and are reflected in major, trace element and Sr–Nd–Pb isotope compositions. Qualitative geochemical analyses and semi‐quantitative modelling suggest that the compositional differences in mafic arc volcanic rocks can be accounted for by differences in source mixing between mantle wedge peridotite and slab‐derived crustal components. Slab melts‐peridotite source mixing governs most of the lithochemical features of the continental arc and the Lesser Antilles arc mafic volcanic rocks, which is especially true for Sr–Nd–Pb isotopes. On the other hand, such source mixing occurred to a lesser extent in the petrogenesis of oceanic arc mafic volcanic rocks. Magma evolution processes such as fractional crystallization may further modify the lithochemical composition of the arc volcanic rocks, especially the felsic ones, but this is not the governing factor.

2-D Dynamic Excitation Temperature of Cu+ Under Diffuse Mode in Vacuum Arc

Cu I (Cu neutrals) excitation temperature is usually measured by researchers while analyzing vacuum arcs (ignited by CuCr electrodes). Since ions may have information that neutrals do not have, measuring Cu II (Cu <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{+})$</tex-math> </inline-formula> might reveal some new features of the vacuum arc. In this article, Cu II excitation temperature is measured by observing seven Cu II lines. Measurement results show the existence or not of a Cr component in a vacuum arc can greatly change the 2-D distribution pattern of Cu II excitation temperature (researchers suggest no influence on Cu I); from a “flat” shape changes to a “columnar” or a “bowl” shape (related to gap length). However, the Cr ratio in CuCr electrodes does not cause a noticeable difference both in Cu II excitation temperature value and in 2-D distribution shape. In the case of CuCr electrodes, before the arc mode change to anode spot mode, a new phenomenon occurs under diffuse mode; as the arc current grows higher than a critical value under a certain length of the gap, the temperature starts to drop in the area near the anode surface, forming a temperature valley. This temperature valley can be interpreted as a local increase in Cu II density. The local ion eruption caused by the Cr component might be a trigger or a pre-process for arc mode changing to anode spot mode.

Prediction of weld back width based on top vision sensing during laser-MIG hybrid welding

Online welding quality monitoring has gained increasing attention in modern automatic production. This work proposed a prediction method of weld back width based on top vision during laser-MIG (Metal Inert-Gas) hybrid welding. A high-speed photography system was used to monitor the laser-MIG hybrid welding, which could observe the visual information from top of the weldment. Visual information including the features of keyhole, arc and molten pool, were extracted as model inputs by image processing and signal processing, and the weld back width was extracted as model output by 3D (Three-Dimension) point cloud processing. An ATT-LSTM (Attention - Long Short Term Memory) prediction model was constructed to predict the weld back width. Experimental results show that ATT-LSTM can not only improve the accuracy and generalization ability of weld back width prediction but also deliver interpretable analysis, compared with other methods such as RNN (Recurrent Neural Network), LSTM, GRU (Gated Recurrent Unit), LSTM-ATT, which MSE (mean square error) was 0.0848 mm2, R2 (r-squared) was 0.5900, CORR (correlation coefficient) was 0.7694 and the comprehensive prediction error (2σ) was 0.5853 mm. The most attention was focused on the keyhole feature, and the feature information reflecting droplet transfer and laser-arc coupling stability was also discussed.

Series DC Arc Characteristic and Diagnosis Strategy for Distributed PV Power Generation

In order to realize the nation’s goal of achieving carbon peaking before year 2030 and the carbon neutrality by year 2060, the installed capacity of distributed PV power generation system has increased year by year in China, which increases the probability of DC arc fault. The features of DC arc may be very weak under some conditions. When the current of DC arc is large and the voltage level of photovoltaic array is high, DC arc will be very stable, and it is hard to be detected. Besides, if there are many high-power devices around DC arc detector, the output signal of current sensor will be seriously interfered, and it will be more difficult to distinguish between normal state and arc fault state. DC arc can be divided into unstable combustion stage and stable combustion stage. When in stable combustion stage, DC arc is also hard to be detected. Fortunately, the features of DC arc are obvious when in unstable combustion stage and the value of current spectrum energy will significantly increase. When the spectrum energy exceeds the set threshold in five consecutive time windows, it is preliminarily determined that there is a suspected arc. If the spectrum energy still exceeds the set threshold within five consecutive time windows, it is finally determined that there is an arc fault, otherwise, short PV array for further diagnosis. If there is an arc fault, the fluctuation characteristics of DC arc will be enhanced and the loop current will go fluctuating intensely again, then spectrum energy calculated will exceed the set threshold and an arc fault alarm can be sent out. Taking into consideration the different features of DC arc’s unstable combustion stage and stable combustion stage, a Series DC arc diagnosis method based on current spectrum energy is proposed, which amplifies the fluctuation characteristics of arc current and keeps arc current fluctuating strongly for a long time by shorting the PV array. The spectrum energy is calculated through FFT analysis of each PV string’s current, compared to the calculated spectrum energy with the set threshold, and then decided whether DC arc fault exists. The results to an experimental platform verify the effectiveness of the arc detection method, which has advantages of low calculation cost and high accuracy.

Mesozoic magmatic arc in East Asian continental margin triggered by Paleo-Pacific plate subduction: Constraints from gravity and magnetic anomalies

The Mesozoic East Asian Continental Margin (EACM) is generally considered as a continental magmatic arc triggered by Paleo-Pacific Plate subduction. However, the magmatic arc was not evident for a long time. This paper tries to use the gravity and magnetic responses along the magmatic arc to deeply explore its spatio-temporal distribution. Based on the gravity and magnetic anomalies of the Mesozoic magmatic arc on the EACM and combined with the integration of previous geological and geochronological studies, it is found that the tectonic features of the magmatic arc are more obvious in the fourth-order approximation/detail gravity anomaly fields by using wavelet multi-scale analysis. Furthermore, the residual crustal gravity anomalies containing the medium-wavelength components of the complete Bouguer gravity anomalies are analyzed for the identification of the Jurassic magmatic arcs. Finally, line-drawing analysis is performed on the fourth-order detail gravity anomaly field to explore the response of the Mesozoic magmatic arcs to Paleo-Pacific subduction on the EACM. Our results support that the magmatic arcs on the EACM mainly developed in the Late Triassic-Early Cretaceous Andean Active Continental Margin and in the late Early Cretaceous-Eocene transtensional continental margin. Our study contributes to the formation and refinement of the Paleo-Pacific Plate subduction mechanism and the Mesozoic tectonic evolutionary model of the EACM, and also provides geophysical evidence for the reconstruction of dynamic processes of the EACM.

Machine-learning model for prediction of martensitic transformation temperature in NiMnSn-based ferromagnetic shape memory alloys

Martensitic transformation temperature (TM) of NiMnSn-based ferromagnetic shape memory alloys (FSMAs) is crucial to identifying the operating range of an application. From a materials design point of view, an efficient method that can predict the TM accurately should be strongly pursued, to meet various applications with different operating temperatures. In this paper, we demonstrate that machine learning (ML) can rapidly and accurately predict the TM in NiMnSn-based FSMAs. We evaluate the performance of four machine learning models, including Random Forest Regressor (RFR), Support Vector Regression (SVR), Linear Regression (LR), and XGBRegressor (XGBR) model. Three important features of Numa, Arc, and avg Ven are selected as the optimal feature combination for building the model. Moreover, to ensure the best generalization ability of the model, multiple methods of cross-validation (Leave-One-Out Cross-Validation, 3-fold Cross-Validation, and 5-fold Cross-Validation) are used. Finally, the XGBR model exhibits the best performance for predicting the TM (R2 = 0.903 and RMSE = 5.4, R5f2 = 0.869 and R3f2 = 0.838). The results of small deviation and variance proven that the XGBR model, proposed in this work, is suitable to be used to predict the TM of unknown NiMnSn-based FSMAs. This work is expected to promote the targeted design of FSMAs.

Molecular physiology of Arc/Arg3.1: The oligomeric state hypothesis of synaptic plasticity.

The immediate early gene, Arc, is a pivotal regulator of synaptic plasticity, memory, and cognitive flexibility. But what is Arc protein? How does it work? Inside the neuron, Arc is a protein interaction hub and dynamic regulator of intra-cellular signaling in synaptic plasticity. In remarkable contrast, Arc can also self-assemble into retrovirus-like capsids that are released in extracellular vesicles and capable of intercellular transfer of RNA. Elucidation of the molecular basis of Arc hub and capsid functions, and the relationship between them, is vital for progress. Here, we discuss recent findings on Arc structure-function and regulation of oligomerization that are giving insight into the molecular physiology of Arc. The unique features of mammalian Arc are emphasized, while drawing comparisons with Drosophila Arc and retroviral Gag. The Arc N-terminal domain, found only in mammals, is proposed to play a key role in regulating Arc hub signaling, oligomerization, and formation of capsids. Bringing together several lines of evidence, we hypothesize that Arc function in synaptic plasticity-long-term potentiation (LTP) and long-term depression (LTD)-are dictated by different oligomeric forms of Arc. Specifically, monomer/dimer function in LTP, tetramer function in basic LTD, and 32-unit oligomer function in enhanced LTD. The role of mammalian Arc capsids is unclear but likely depends on the cross-section of captured neuronal activity-induced RNAs. As the functional states of Arc are revealed, it may be possible to selectively manipulate specific forms of Arc-dependent plasticity and intercellular communication involved in brain function and dysfunction.

Features of a burning electric arc superimposed on gas discharge with liquid electrolyte cathode

The conditions for burning an electric arc in a discharge plasma with a solution cathode have been studied. Both discharges were connected to the same metal anode. The electric arc burned in the current range of 5–10 A. The discharge current with a solution cathode varied within 8-15 A. In the experiments, aqueous solutions of common salt were used. The specific electrical conductivity of the solutions was 10–15 mS/cm. Spectral investigations of arc plasma radiation and discharge with a solution cathode have been carried out. Calculations of the parameters of the electron gas in the plasma column have been performed.

The “Nazas Arc” is a continental rift province: Implications for Mesozoic tectonic reconstructions of the southwest Cordillera, U.S. and Mexico

Abstract We reject the notion of a Jurassic continental arc in eastern Mexico, termed the “Nazas arc,” on geologic grounds. Instead, we propose that the Jurassic continental arc of the SW Cordilleran U.S. and northern Sonora, Mexico, passed southward into the oceanic realm and is represented by Jurassic arc volcanic and plutonic rocks that fringed the Mexican paleo-Pacific margin, which are currently found in the western Peninsular Ranges of southern California, USA, and Baja California, the Vizcaino Peninsula of Baja California, and western mainland Mexico. To show this, we present a summary of the geologic features of a continental arc, using the geology of the southern end of the Jurassic continental arc, in southern Arizona and northern Sonora. These features include multi-kilometer–thick sections of volcanic rock; large volcanic centers, including silicic calderas; major eruptive units that can be correlated for distances of 100 km or more; abundant, large plutonic suites; and continuity of these features for distances of hundreds of kilometers along the length of the continental arc. Then we show that the “Nazas arc” consists of scattered, small continental rift basins with thin (meters to tens of meters thick) volcanic sections at the base of clastic sections that are hundreds of meters thick. Plutonic rocks are entirely absent from the “Nazas arc,” despite the fact that post-Jurassic tectonic events should have exposed them if they existed. This paper also presents a tabulation of all published U-Pb zircon dates in the Jurassic continental arc of southern Arizona, USA, and northern Sonora (Table 1A), and in the “Nazas arc” of eastern Mexico (Table 1B), with ages, methods, the rock type dated, and notes on geologic relations. We use this to detail the abundance of thick, laterally extensive volcanic sections and large plutonic suites in a continental arc (the Jurassic arc of southern Arizona–northern Sonora), which contrasts sharply with the “Nazas arc.” The term “Nazas arc” has been in widespread usage for volcanic rocks in eastern Mexico for decades in many dozens of papers, and it is portrayed as a 2000-km-long, 250-km-wide belt that extends from Sonora through eastern Mexico to Chiapas. It has been misunderstood to form a subduction-related silicic large igneous province (SLIP), and it has been proposed that the Gulf of Mexico formed as a backarc basin behind the “Nazas arc.” The “Nazas arc” model also requires an east-dipping subduction zone under Mexico, and a separate west-dipping subduction zone under the oceanic arc rocks of western Mexico, which those models portray as an exotic arc, despite the presence of abundant detrital zircon from the Mexican margin. We urge workers to abandon the term “Nazas arc” and replace it with “Nazas rift province,” which represents continental rift basins formed during the breakup of Pangea.

Special features of coldwire gas metal arc surfacing

To study the features of GMA surfacing with the supply of an additional cold filler wire, the bead welding at different wire feed rates with different arc polarity are performed, at which the arc current and the current flowing from the electrode wire to the base metal are measured. It is determined that with the reverse polarity of the arc, the normal formation of the welding bead is ensured with a slight penetration of the base metal, while with the direct polarity, the heat release on the base metal is insufficient to form a bead of an acceptable shape, and the process is accompanied by significant spatter. It is established that during the feeding at an angle of 45°, the feed rate of the filler wire, which ensures that the wire is being melted in the center of the arc, is 1.4 times greater than when feeding is occurring at an angle close to 90°. In this case, the filler wire is melted due to the plasma radiation of an arc, and not by the current flowing through it.

Some features of automatic electric arc surfacing under the flux with controlled periodic change of modes

The development and application of automatic electric arc surfacing under flux with controlled periodic change of modes makes it possible to expand significantly the possibilities of traditional technological processes of surfacing. The carried out experimental investigations make enabled us to determine the advantages of the welding process with modulation of modes in comparison with welding in stationary mode. It is established that the parameters of the modulated welding current (frequency, sparseness) determine the degree of influence on the physical and mechanical characteristics of the welded metal and in most cases improve them compared to the characteristics of stationary mode. The result of the analysis defines that in the pulse mode it is possible to achieve the reduction of inclusions from the composition of the flux by almost 30%. This reduction is an additional factor in ensuring the characteristics of strength (hardness, wear resistance) of the weld roller and weld.

Potentiodynamic corrosion behavior and microstructural features of gas tungsten constricted arc (GTCA)-welded superalloy 718 joints

Abstract The gas tungsten constricted arc welding (GTCAW) process was used to join thin Su-718 alloy sheets to minimize alloying segregation and Laves phase precipitation in the fusion zone (FZ). The potentiodynamic corrosion behavior of GTCAW Su-718 alloy joints was studied and correlated to the microstructural features of welds. The potentiodynamic corrosion test was done in a 3.56 wt.-% NaCl solution to determine the corrosion rate of Su-718 alloy joints. The optical microscopy (OM) technique was used to analyze the microstructure of corroded weldments. The scanning electron microscopy (SEM) technique was used to study the Laves phase development in FZ. The SEM X-ray energy dispersive spectroscopy (EDS) technique was used to for elemental mapping of FZ. The corrosion resistance of Su-718 joints is inversely proportional to the precipitation of Laves phase in FZ. The GTCA welded Su-718 alloy joints disclosed superior corrosion resistance for the joints with lower Laves phase precipitation. It is correlated to the refining of FZ microstructure, which aids in minimizing the Laves phase precipitation. The joints with higher Laves phase precipitation revealed inferior corrosion resistance. It is attributed to coarsening of FZ microstructure, which raises the alloying segregation and leads to depletion of alloying elements in FZ. The dendritic core regions showed severe corrosion compared to the interdendritic regions. The corrosion resistance of GTCA welded Su-718 joints is better than that of CC-GTAW and PC-GTGAW joints and comparable to that of EBW and LBW joints. It refers to the arc constriction and high frequency current pulsation.

Specific Features of Electric Arc Furnaces as Electric Energy Receivers

Specific Features of Electric Arc Furnaces as Electric Energy Receivers

Physico-chemical conditions of crystallization of minerals-phenocrysts in basaltic complexes hosting massive sulfide deposits of the Urals fnd Siberia

he paper discusses the physico-chemical formation conditions of minerals-pheno-crysts in basaltic complexes, which host massive sulfde deposits of the Urals and Siberia. It is found as a result of study of melt inclusions that clinopyroxene from basalts of the Valentorka (North Urals) and Kyzyl-Tashtyg (South Siberia) deposits crystallized from melts with similar temperature (1165–1130 and 1210–1085 °С, respectively) and chemical parameters. In both cases, the composi¬tions of basalt-andesite magmas (with features of igneous island arc and back-arc basin systems) evolved with a decrease in FeO, MgO, and CaO contents and increase in K2O and SiO2 contents. Modeling, which is based on the compositions of inclusions and clinopyroxene, showed that miner-als-phenocrysts crystallized from intermediate magma chambers of diferent depth, the parameters of which are consistent with each other and with data on present-day suprasubduction magmatism: Valentorka deposit – 33–27, 23–13, and 10–3 km, 1185–1090 °C; Kyzyl-Tashtyg deposit – 27–20, 15.0–6.7, and 5.0–1.7 km, 1215–1105 °С. Calculations using compositions of melt inclusions show a consistent change of melts from basalts to rhyolites, indicating that the combination of contrasting volcanic complexes of the deposits studied are a result of the evolution of initial basaltic magmas during their uplift to the upper crustal horizons. Our studies of rocks, clinopyroxene and melt inclu¬sions indicate that the basaltic complexes of the Valentorka and Kyzyl-Tashtyg deposits formed in an ancient suprasubduction island arc – back-arc basin system.

Mineralization and petrogenesis of the Qiongheba porphyry copper deposit in Mengxi district, East Junggar, China

The Qiongheba porphyry Cu deposit is characterized by geochemical features of island arc and adakitic intrusions with fractional crystallization playing a key role in the formation of the ore-bearing rocks. Calculated sulfur concentrations in silicate melts at sulfide saturation show that two-thirds of the sulfur was exsolved during the fractional crystallization process to contribute to the formation of sulfides. The ore-bearing rocks in the Qiongheba area yielded U-Pb zircon ages of 414–412 Ma coeval with the 412 Ma Re-Os age of molybdenite indicating that sulfide mineralization is broadly coeval with magmatic crystallization. The color cathodoluminescence of quartz (purple) and K-feldspar (pink) in the fibrous veins and miarolitic cavities (Qtz-2 and Kfs-2) are the same as those (Qtz-1 and Kfs-1) in the granitic porphyry whereas the hydrothermal quartz (Qtz-3) and K-feldspar (Kfs-3) are black and green, suggesting that the color cathodoluminescence can be used to unravel the paragenesis of PCD. The oxygen isotopic values of Qtz-1 and Qtz-2 range from 9.15 to 10.1‰ and 8.93 to 10.4‰ with calculated equilibrium fluid compositions of 9.86 to 11.7‰ and 10.5 to 12.0‰, respectively, indicating a magma-dominated fluid composition, whereas Qtz-3 veins have very low oxygen isotopic values from −4.60 to −1.25‰ with corresponding fluid compositions of −3.51 to −0.17‰, implying that the fluid formed via the mixing of magmatic and meteoric water. Titanium-in-quartz thermometry constrains the magmatic crystallization to 580–627 °C, whereas the magmatic to hydrothermal transition occurred at 523–613 °C.