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The rational use of natural wind in extra-long tunnels for feedforward operation ventilation control can dramatically reduce tunnel operation costs. However, traditional tunnel natural wind calculation theory lacks a prediction function. This paper proposes a three-stage tunnel natural wind prediction method relying on the Yanglin Tunnel in Yunnan, China based on the massive meteorological parameters provided by the open-source national meteorological stations around the tunnel, which make up for the partial deficiency of the meteorological parameters of the tunnel portal. The multi-layer perceptron model (MLP) was used to predict the real-time meteorological parameters of the tunnel portal using the data from four national meteorological stations. The nonlinear autoregressive network model (NARX) was used to predict the meteorological parameters of the tunnel portal in the next period based on the predicted and measured real-time data. The natural wind speed in the tunnel was obtained by a theoretical calculation method using the predicted meteorological parameters. The final tunnel natural wind prediction results are in good agreement with the field measured data, which indicates that the research results of this paper can play a guiding role in the feedforward regulation of tunnel operation fans. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal micas in pegmatoid and greisen are Li-phengite and zinnwaldites. • The ore-forming fluids are magmatic-origin and CO 2 -rich, F-poor and rare metal-rich. • The breakdown of Ca-plagioclase and fluid-rock interactions drive W mobilization. The Xiuwacu deposit is a typical granite-related quartz-scheelite-molybdenite vein type deposit hosted within sandstones and sandy slates in the southern Yidun Terrane, western Yunnan Province, China. The Xiuwacu complex comprises the Late Triassic biotite granite and Late Cretaceous monzogranite porphyry (MGP) and aplite granite. Extensive and intensive alteration including potassic, propylitic, phyllic, silicic and argillic alteration developed within the Late Cretaceous monzogranite porphyry. Greisenization and pegmatization occurred in the roof of the Xiuwacu complex, suggesting large-scale fluid-rock interactions. However, the effects of fluid-rock interactions on the elemental exchange and ore-forming processes at Xiuwacu still remained unclear. This study firstly reported whole-rock major and trace elements of representative altered rocks and in situ major and trace elements of micas from fresh and altered rocks, and quantitively constrained the mobilization of elements by normalized isocon diagrams. The altered MGP are characterized by higher loss on ignition (LOI) values (>2), lower light rare earth elements (LREEs) and variable large ion lithophile elements (LILEs) contents, with higher Cs, K, Rb and Ba contents and lower Sr content than fresh MGP. The classification diagram based on mica composition shows that magmatic biotites from the Late Triassic biotite granite and Late Cretaceous monzogranite porphyry belong to Fe biotites. Hydrothermal micas from pegmatoid and greisen belong to Li-phengites and zinnwaldites, and hydrothermal micas from quartz-molybdenite vein are classified as zinnwaldites. Li-phengites and zinnwaldites have relatively lower F contents, higher W, Sn, Li, Cs contents than biotites, intergrown with calcite and ankerite, suggesting CO 2 -rich, F-poor and rare metal-rich nature of hydrothermal fluids. Based on a compilation of fluid inclusions, H–O–S-Sr isotopes, scheelite geochemistry from previously published literatures and compositions of altered rocks and micas from this study, the tungsten ore-forming processes at Xiuwacu could be concluded as follows: (1) the initial moderately-oxidized, F-rich fluids exsolved from parental magmas of MGP form fluorite-quartz assemblages (pegmatoid; 400–300 °C); (2) the F-poor, W-rich, moderately acid fluids cause the breakdown of Ca-rich plagioclases, which consumes H+ and provides Ca2+ for the precipitation of early-stage scheelites (greisen; approximately 300 °C); the evolved nearly neutral and medium- to low-temperature fluids (300–150 °C) drive the fluid-rock interactions to supply Ca2+ for the deposition of main-stage scheelites. The deposition of Mo was not determined by the fluid-rock interactions, but by the ore-forming fluids transformed from oxidized to reduced nature. [ABSTRACT FROM AUTHOR]

The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block. The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east and west sides and the discontinuous marginal zone, the late-stage main body of dominant riebeckite granite, and minor aegirine granite. Studies on petrological geochemistry and LA-ICP-MS zircon U-Pb dating of the late-stage riebeckite granite, origin and evolution of the Muchang alkali granite and the relationship between the granite and the associated skarn-type Luziyuan Pb-Zn deposit are discussed in this paper. The results show that the Muchang alkali granites belong to A-type granites, which are characterized by enrichment in Al2O3, SiO2, total alkali and Fe, depletion in MgO and CaO contents with high FeOT/MgO ratios. The REE concentrations are relatively high, exhibiting highly fractionated LREE patterns with significantly Eu negative anomaly. The Muchang granites are obviously enriched in lithophile elements (e.g., Rb, K, U and Th) and high field strength elements (e.g., Zr, Hf, Nb, Y and Ga) with high 10000×Ga/Al ratios and depleted in Sr, Ba, Ti, Cr and Ni, which are similar to those of the A-type granites and quite different from those of S-type and I-type granites. The LA-ICP-MS zircon dating results of the Muchang granite gave a weighted mean age of 266.2±5.4 Ma (2σ), suggesting that they were formed in the stage of extension at the end of post-collision at Middle Permian and the consumption of Paleo-Tethys ocean took place before 266 Ma. It is suggested that the unexposed intermediate-acid intrusive rocks in the Luziyuan ore district, which is the 'sister' rocks material of the Muchang granites and related closely to Luziyuan Pb-Zn mineralization, were the product of Middle Permian. [ABSTRACT FROM AUTHOR]