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• The arc is yellow during the flashover of snow-accreted insulator in the artificial climate chamber. While in the natural environment, the discharge arc appears blue and purple, and the phenomenon of arc levitation and snow layer shedding can be observed. • The flashover path of FXBW-35/70 is affected by the snowing degree significantly. The discharge path gradually transitions from the creepage distance under slight snowing to the dry arc distance in the case of severe snowing. • There are many discrepancies between different types of the insulators, such as the creepage distance, dry arc distance and other structural parameters, and the number of air gap after snowing, which affect arc dynamic development properties. Hence, the electrical performance of composite insulator is better than that of glass insulator. The safe and reliable operation of power system in China is significantly affected by snow-covered insulator. At present, many studies on snow-accreted insulator have been undertaken by domestic and foreign scholars in the laboratory. However, whether the laboratory test is equivalent to the field test and whether it can be directly used to guide the external insulation design of transmission line still need to be evaluated. In this regard, AC flashover test of snow-coated insulator was carried out in the laboratory and field in this paper, and then the characteristics of AC discharge path and the variation of leakage current of snow-accreted insulator with time were obtained, and its flashover performance was compared and analysed. The research results show that the amount of snow on the insulator gradually decreases from the stagnation point at the edge of the shed on the windward side to both sides, which is attributed to the uneven distribution of the local collision coefficient of snow crystal particles on the insulator surface. The arc is yellow during the flashover of snow-accreted insulator in the artificial climate chamber. While in the natural environment, the discharge arc appears blue and purple, and the phenomenon of arc levitation and snow layer shedding can be observed. For composite insulator FXBW-35/70 covered with different degrees of snowing in the natural environment, the flashover path develops along the creepage distance in case of the slight snowing, while the path propagates over the dry arc distance under severe snowing condition. Consequently, the flashover voltage decreases by 48.7%. There are many discrepancies between different types of the insulators, such as the creepage distance, dry arc distance and other structural parameters, and the number of air gap after snowing, which affect arc dynamic development properties. Hence, the electrical performance of composite insulator is better than that of glass insulator, and the snowing flashover voltage of the former is 5.56–9.47% higher than that of the latter. [ABSTRACT FROM AUTHOR]

The development effect of water flooding in an ultra-low permeability reservoir is poor due to its poor physical properties and high shale content, so an experimental study of air flooding which helps to complement energy production was carried out. Based on the Accelerating Rate Calorimeter experimental results, the crude oil of N block in L oilfield can undergo low-temperature oxidation reactions, which are the basic condition for air flooding. Three groups of experimental natural cylinder cores designed for oil displacement, water flooding and air flooding were used respectively, and the relationship between differential pressure, oil recovery, injection capacity with injection volume was investigated. It is observed that the recovery efficiency increased 2.58%, the injection-production pressure difference dropped 60% and the injection capability increased 60% in the experiment of shifting air flooding after water flooding to 75% moisture content, compared with water flooding alone. It has been shown in the results that the recovery efficiency improved sharply more than water flooding, the effect of depressurization and augmented injection was obvious, and the air displacement was thus validated. We suggest that other science and technology workers should perform further tests and verify this result through numerical simulation. [ABSTRACT FROM AUTHOR]

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[Display omitted] • 247–241 Ma andesites in the Funing area generated in a subduction-related setting. • They derived from a wedge source recently modified by subducted slab-related components. • An Early-Middle Triassic volcanic arc developed along the southern margin of South China Block. • Northward subduction beneath the southern margin of SCB existed in the Early-Middle Triassic. Questions remain about whether the volcanic rocks and spatially associated mafic to intermediate intrusions in the Funing area, Southwestern China, are part of Emeishan large igneous province (ELIP) and formed in a plume-related extensional setting. Zircon U-Pb ages, geochemical and Sr-Nd-Hf isotopic data are reported for these volcanic rocks, in order to investigate their source, petrogenesis and tectonic setting. Zircon U-Pb dating yields an eruption age of 246 ± 2 Ma for the volcanic rocks, younger than that of the ELIP. They are calc-alkaline rocks, and are characterized by high MgO (>5 wt%) and Al 2 O 3 contents at intermediate SiO 2 contents (52.12–59.20 wt%), similar to those of high-Mg andesites, indicating a mantle source. They are enriched in large ion lithophile elements and light rare earth elements and are depleted in high field strength elements, with evidently negative Nb, Ta and Ti anomalies. They have relatively high Th/Nb and Th/La ratios and low Sr/Y and La/Yb ratios, with radiogenic initial Sr isotopic ratios (87Sr/86Sr i = 0.7080–0.7110) and negative ε Nd (t) (−8.8 to −6.5) and ε Hf (t) (−5.3 to −2.4) values. All of these geochemical features suggest that the Funing high-Mg andesitic rocks were derived from partial melting of an ancient, refractory lithospheric mantle that had been metasomatized by subducted sediment-derived fluids/melts before magma generation. In the context of other Early-Middle Triassic magmatism in the adjacent areas, we suggest that the Early-Middle Triassic volcanic rocks in the Funing area were generated in an arc setting, rather than by mantle plume-related melting. The spatial and temporal distribution of volcanic arc and the ophiolitic mélange in the China-Vietnam border region indicate Early to Middle Triassic northward subduction of the Babu (SW China)-Cao Bang (NE Vietnam) ocean basin beneath the southern margin of the South China Block. [ABSTRACT FROM AUTHOR]

Abstract: Voluminous Late Paleozoic igneous rocks and associated Cu–Au–Mo deposits occur in the northwestern Tianshan district, Xinjiang, west China. However, the tectonic setting and petrogenesis of these rocks remain controversial. This paper reports zircon U–Pb and Hf CUU isotopic data, major and trace elements, and Sr–Nd–Pb isotopic data for the intrusive rocks and minor dacites in the Lamasu–Dabate area of northwestern Tianshan adjacent to the Cu–Au–Mo deposits. LA-ICPMS U–Pb zircon analyses suggest that the Lamasu porphyries were formed at 366±3Ma and contain 907–738Ma inherited zircons, the Dabate dacites were formed at 316±4Ma, and granite porphyries were formed at 289±3Ma with ~319Ma inherited zircons. The Lamasu porphyries consist of plagioclase granite and granodiorite, and are geochemically similar to adakites, e.g., having high Al2O3 (14.54–19.75wt.%) and Sr (308–641ppm) and low Y (7.84–16.9ppm) contents, with fractionated rare earth element (REE) patterns and slightly positive Sr anomalies. However, they have variable initial ratios of 87Sr/86Sr (0.7072–0.7076) and 206Pb/204Pb (18.139–18.450), and variable εNd(t) (−5.6 to −0.8) and positive εHf(t) (+1.4 to +10.6) values. They also have variable Mg# (100×Mg2+/(Mg2++Fe2+)) (41–73) and low Th (3.13–8.09) and Th/Ce (0.14–0.28) values. We suggest that the Lamasu adakitic magmas were generated through partial melting of southward subducted Junggar oceanic crust, with subsequent melt-mantle interaction and assimilation of basement rocks. The Dabate dacites show typical arc-like geochemical characteristics (e.g., enrichment of large ion lithophile elements (LILE) and strong negative anomalies of Ta, Nb, P and Ti), with variable εNd(t) (+0.1 to +3.3). They were probably generated by melting of juvenile basaltic lower crust as a result of magma underplating. The Dabate granite porphyries are geochemically similar to A2-type granites, e.g., high SiO2 (75.6–77.6wt.%) and alkalis (Na2O+K2O=8.27–8.70wt.%), low CaO (0.28–0.34wt.%) and Mg# (2–10), and obvious negative Eu, Ba and Sr anomalies. They have variable values of εNd(t) (−1.7 to 0) and 206Pb/204Pbi (18.567–18.721) and zircon εHf(t) (+0.5 to +11.1). The Dabate A-type granite porphyries contain Late Carboniferous residual zircon cores, suggesting that their source rock possibly contained Carboniferous arc igneous rocks. Taking into account all available data from Late Paleozoic magmatic rocks and Cu–Mo–Au mineralization in the northern Tianshan district, we suggest that the Dabate–Lamasu area was a continental arc during the Late Devonian–Carboniferous but had entered a post-collisional stage by the Early-Permian (~290Ma). [Copyright &y& Elsevier]

Abstract: Two types of Neoproterozoic metabasites occur together with regionally intruded arc-related Neoproterozoic granitoids (ca. 850–830 Ma) in the Hongseong area, southwestern Gyeonggi Massif, South Korea, which is the extension of the Dabie–Sulu collision belt in China. The first type of metabasite (the Bibong and Baekdong metabasites) is a MORB-like back-arc basin basalt or gabbro formed at ca. 890–860 Ma. The Bibong and Baekdong metabasites may have formed during back-arc opening by diapiric upwelling of deep asthenospheric mantle which was metasomatized by large ion lithophile element (LILE) enriched melt or fluid derived from the subducted slab and/or subducted sediment beneath the arc axis. The second type of metabasite (the Gwangcheon metabasite) formed in a plume-related intra-continental rift setting at 763.5±18.3 Ma and is geochemically similar to oceanic island basalt (OIB). These data indicate a transition in tectonic setting in the Hongseong area from arc to intra-continental rift between ca. 830 and 760 Ma. This transition is well correlated to the Neoproterozoic transition from arc to intra-continental rift tectonic setting at the margin of the Yangtze Craton and corresponds to the amalgamation and breakup of Rodinia Supercontinent. [Copyright &y& Elsevier]

Abstract: Uncritical application of geochemical plots for granitic rocks, without full appreciation of the limitations of such plots, the broader geological constraints and information about coexisting other rock types, commonly lead to incorrect tectonic interpretations. We consider this to be the case for the arc interpretations of the 850–740Ma igneous rocks in South China. In this Reply, we counter-argue all four lines of evidence used by Munteanu and Wilson [Munteanu, M., Wilson, A., this volume]. The South China piece in the Rodinian puzzle. A comment on “Assembly, configuration, and break-up history of Rodinia: a synthesis” by Li et al. (2008) [Precambrian Res. 160 (2008) 179–210]. Precambrian Res.] for an arc model in the western South China Block between 850 and 740Ma. [Copyright &y& Elsevier]