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A molybdenum-bismuth sulfide ore in Hunan Province contains 0.05% molybdenum and 0.1% bismuth. And the traditional flotation process, i.e., full flotation of molybdenum-bismuth-sulfur-separation of molybdenum from bismuth-sulfur-separation of bismuth-sulfur, exists with low recovery of molybdenum and bismuth, complicated pharmaceutical system, larger dosage of pharmaceuticals, and higher production cost. In order to strengthen the separation of molybdenum and bismuth, calcium hypochlorite was introduced to replace sodium sulfide as bismuth depressant, and the flotation process of this molybdenum-bismuth sulfide ore was optimized. The new flotation process is molybdenum-bismuth mixed flotation-molybdenum-bismuth separation-sulfur flotation, which can obtain a molybdenum concentrate with molybdenum grade of 42.02 % and molybdenum recovery of 81.45% and a bismuth concentrate with bismuth grade of 42.23% and bismuth recovery of 76.38%. Compared with the traditional flotation process, the new process increased the grade and recovery of molybdenum concentrate by 1.63 and 2.35 percentage points, and that of bismuth concentrate by 11.98 and 9.21 percentage points, and at the same time reduced the content of pH, COD, suspended solids, and some heavy metal ions in the beneficiation wastewater, which is of good industrial value and broad application prospect. [ABSTRACT FROM AUTHOR]

Calculated by using the pipeline model, the burial depths of the 150 and 180°C hot dry rocks (HDRs) are 3.20–3.56 and 3.92–4.36 km in the Reshuiwei geothermal field, respectively, while those in the Huitang geothermal field are 3.13–3.50 and 3.84–4.28 km, respectively. Based on the analysis of the geophysical and terrestrial heat flow data, rock thermal generation rates, and the hydrochemical thermometric scale data, we summarized the formation mechanisms of the HDRs in Hunan Province: (i) the boundary deep faults in the welding area have made the intersection part of the deep faults an open tectonic environment, which is beneficial to the upwelling of deep-mantle-sourced thermal matter. (ii) The southeastern Hunan Province is the front region of the West Pacific subduction and retreat. Lithospheric thinning in this area is significant since the Mesozoic era, especially in the Dongting Lake basin, which was formed during extension and depression. This kind of regional lithospheric thinning is favorable for the lateral and upward migration and the intrusion of the deep-mantle-sourced hot substances. (iii) Rocks with high radioactive heat production rates are important crustal thermal sources for the formation of HDRs. Besides that, plutons with similar geological conditions are favorable for the formation of HDR resources. These plutons include the Baimashan pluton and its surrounding areas, and the eastern Dongting Lake plain. Moreover, the intermediate and acid granites distributed in the Chenzhou-Linwu deep fault are also part of the plutons, and the area where the Chenzhou-Linwu deep fault convergent with the Changde-Anren deep fault. [ABSTRACT FROM AUTHOR]

The Huangshaping-Baoshan ore field is located in the Qianlishan-Qitianling ore concentration area in southern Hunan. The structure in the ore field is multi-period, and the ore body output is obviously controlled by the structure. In previous studies on the structure of this area, there is a lack of numerical simulation of the tectonic stress field for the process of tectonic deformation and its rock-controlling and ore-controlling processes. Therefore, based on the previous research results, this paper analyzes the typical geological structure points of the ore field in detail and further improves the stress state of the ore field structure system and the main tectonic period. Using ANSYS finite element numerical simulation software, this paper discusses the distribution characteristics and evolution of the tectonic stress field in the pre-mineralization stage and ore-forming stage of the ore field and summarizes the characteristics of tectonic deformation and the law of tectonic stress field controlling rock and ore control. It is considered that the near SN trending compression-torsional fracture is formed by regional SN compression before mineralization, and the KW-trending fracture shows obvious low strain energy, which provides favorable conditions for subsequent magmatic emplacement. The dominant position of the maximum principal stress in the ore-forming stage changed to the NE direction, and the maximum shear stress intensity was large, indicating that the deformation was strong in this period, and the pre-existing structure was strongly reformed. At this time, the KW-trending strain energy low-value fault zone was a powerful channel for magmatic emplacement and was limited by the NE-trending strain energy high-value fault zone in the periphery of the mining area, so that it could continuously gather and precipitate mineralization in the low strain energy area. Finally, through the comparative study of structural stress field characteristics of known ore points, it provides the basis for prospecting direction in this area. [ABSTRACT FROM AUTHOR]

The effect of alteration on the geochemistry and mechanical properties of granite from Pingjiang, Hunan Province, China was investigated. Six weathered and 14 hydrothermally altered samples in 3 adits were collected for mechanical strength tests, mineralogical and geochemical analysis. The types of alteration observed within the samples were chloritization and argillization. Samples taken from a silicified fracture zone were enriched in quartz. Weathering was observed to significantly weaken the granite whereas the effects of hydrothermal alteration on strength were more complex. The porosity increased with the enrichment of the altered minerals, indicating that the formation of altered minerals degrades the strength of physical bonds between minerals within the granite. The granite Na2O, CaO, K2O, MgO and SiO2 contents decreased while Fe2O3T increased due to weathering. Variations of major elements within the hydrothermally altered granite were distinguished from those observed in weathered samples—notably Mg was removed whilst Si and Fe were generally stable during the hydrothermal alteration. Whereas the quartz-enriched samples gained Si with slight depletions in Mg and Fe. Trace and rare earth elements were both removed in hydrothermal alteration. The variable behavior of major element was quantified by the mobility index which indicated that the different geochemical changes were attributed tochloritization and argillization. Furthermore, the mobility index of Mg was used to identify the dominated alteration in granite and evaluate the effects of chloritization and argillization. Generally, chloritization was found to be more dominant than argillization in weakening the granite. [ABSTRACT FROM AUTHOR]

In December 2019, the New Crown Pneumonia (the COVID-19) outbroke around the globe, and China imposed a nationwide lockdown starting as early as January 23, 2020. This decision has significantly impacted China's air quality, especially the sharp decrease in PM 2.5 (aerodynamic equivalent diameter of particulate matter less than or equal to 2.5 μm) pollution. Hunan Province is located in the central and eastern part of China, with a "horseshoe basin" topography. The reduction rate of PM 2.5 concentrations in Hunan province during the COVID-19 (24.8%) was significantly higher than the national average (20.3%). Through the analysis of the changing character and pollution sources of haze pollution events in Hunan Province, more scientific countermeasures can be provided for the government. We use the Weather Research and Forecasting with Chemistry (WRF-Chem, V4.0) model to predict and simulate the PM 2.5 concentrations under seven scenarios before the lockdown (2020.1.1–2020.1.22) and during the lockdown (2020.1.23–2020.2.14). Then, the PM 2.5 concentrations under different conditions is compared to differentiate the contribution of meteorological conditions and local human activities to PM 2.5 pollution. The results indicate the most important cause of PM 2.5 pollution reduction is anthropogenic emissions from the residential sector, followed by the industrial sector, while the influence of meteorological factors contribute only 0.5% to PM 2.5. The explanation is that emission reductions from the residential sector contribute the most to the reduction of seven primary contaminants. Finally, we trace the source and transport path of the air mass in Hunan Province through the Concentration Weight Trajectory Analysis (CWT). We found that the external input of PM 2.5 in Hunan Province is mainly from the air mass transported from the northeast, accounting for 28.6%–30.0%. To improve future air quality, there is an urgent need to burn clean energy, improve the industrial structure, rationalize energy use, and strengthen cross-regional air pollution synergy control. [Display omitted] • First study of air quality impacts during COVID-19 in Hunan Province, central China. • The changing meteorological conditions contributed 0.5% to PM 2.5. • The residential sector was the main anthropogenic source. • The sharply reduced NO x and VOCs emissions directly led to the decreased PM 2.5. • The regional transport came from the northeast, accounting for 28.6%∼30.0%. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Baoshan is a typical Cu–Mo–Pb–Zn deposit related to granodiorite porphyry. • Cu, Mo, and Pb–Zn ores have low, high, and moderate δ34S values, respectively. • Cu–Mo and Pb–Zn mineralization formed from the same hydrothermal system. • Basement plays a substantial role for the Baoshan Cu–Mo–Pb–Zn mineralization. Southern Hunan Province, China, is characterized by extensive Mesozoic magmatic rocks and coeval polymetallic deposits, including granite-related W–Sn and granodiorite-porphyry-related Cu–Mo–Pb–Zn mineralization. It is commonly accepted that ore-forming materials for Cu–Mo–Pb–Zn mineralization in the southern Hunan area were generally dominated by granodiorite porphyry, owing to the close spatial and temporal relationship between the two. However, the detailed mineralization process for this type of deposit remains unclear, especially with respect to the relationship between the proximal skarn-hosted Cu–Mo and distal carbonate-hosted Pb–Zn mineralization. In this study, high-resolution in situ LA–MC–ICP–MS sulfur isotopic compositions for different types of sulfide from the typical Baoshan polymetallic Cu–Mo–Pb–Zn deposit are used to investigate the characteristics of mineralization in this area. Our results show that three endmembers with distinct δ34S values contributed to the formation of the Baoshan deposit: (1) granodiorite porphyry with moderate δ34S values (2.6‰ to 3.7‰), (2) carbonate strata with high δ34S values (3.8‰ to 22.7‰), and (3) metamorphic or crystalline basement with low δ34S values (−7.0‰ to 4.5‰). Molybdenite from the proximal skarn-hosted Mo mineralization has high δ34S values ranging from 3.6‰ to 6.6‰, whereas pyrite (−1.0‰ to 4.8‰), chalcopyrite (−1.1‰ to 4.4‰), sphalerite (1.9‰ to 4.2‰), and galena (0.2‰ to 4.8‰) from both the proximal skarn-hosted and distal carbonate-hosted Cu–Pb–Zn mineralization have wide-ranging δ34S values depending on their locations. These values suggest that the granodiorite porphyry and carbonate sources dominated the sulfur input for the entire Mo mineralization and that the granodiorite porphyry source dominated most of the Cu–Pb–Zn mineralization with similar or higher δ34S values in the Baoshan deposit, with some contribution from the carbonate strata for the latter mineralization. Deep-seated metamorphic or crystalline basement likely provided sulfur for the other parts of the Cu–Pb–Zn mineralization with low δ34S values. In addition to the contributions by granodiorite porphyry and carbonate strata, our study emphasizes the substantial contribution of basement rock materials to Cu–Mo–Pb–Zn mineralization. The ore-forming materials accumulated in the basement by the intrusion of early mafic magmas, which were then added to the Baoshan granodioritic magmas by remelting and mingling with these magmas. Ore-forming materials may also have been extracted from the basement by hydrothermal circulation triggered by the intrusion of these late granodioritic magmas. [ABSTRACT FROM AUTHOR]