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The Sichuan Basin (SCB) and its surrounding mountainous areas have complicated topography, and the "Nocturnal Rainfall in the Basin (NRB)" and "Nocturnal Rainfall in the Mountainous Areas (NRMA)" are frequent. To further clarify the relationship and the interaction between the two types of "nocturnal rainfall" synoptic systems, the characteristics of the synoptic meteorology, thermodynamics, dynamics, and water vapor fields of the nocturnal precipitation process generated by two Mesoscale Convective Systems (MCSs) that originated from the mountainous area on the western side of the SCB on June 4, 2019 were analyzed and diagnosed in this paper. In addition, the WRF-LES model was used to simulate and analyze the macro and micro physical characteristics of two precipitation centers formed by the main system MCS1 in the center of the SCB and the mountainous areas around it. The results showed as follows. (1) Two MCSs originated from the mountainous area on the western side of the SCB were generated by the eastward movement of the low-pressure trough over the Tibetan Plateau (TP) coupling the higher Convective Available Potential Energy (CAPE) value with the unstable circulation of the upper level. They matured in the SCB and matured and split in the western end of Mt. Daba, respectively. (2) After splitting, the southern part of the sub-system MCS2 sank and moved south along the southern foot of Mt. Daba and uplifted the main system MCS1. After its explosive development, two precipitation centers with the characteristics of the NRB and NRMA were formed. (3) The vertical velocity, divergence, thermal helicity, and potential vorticity could be used as the thermodynamics and dynamics diagnostic quantities to indicate the occurrence and development of the two MCSs. The potential vorticity was an obvious precursory parameter compared with the other three. The water vapor flux divergence and moisture helicity could better indicate the vertical transport of water vapor in the systems. (4) The precipitation simulation result of the WRF-LES model on the main system MCS1 in the SCB was better than that on the sub-system MCS2 in the mountainous area on the northern margin of the SCB. In each MCS1 stage, the precipitation of the NRB was mainly induced by the cold cloud process (supplemented by the warm cloud process), while the precipitation of the NRMA was mainly induced by the warm cloud process. The combination of diagnostic analysis and numerical simulation could effectively promote an understanding of the relationship and interaction between the NRB and NRMA. • The relationship and interaction between nocturnal rainfall in Basin (NRB) and mountainous areas (NRMA) by MCSs were clarified. • A diagnostic analysis method was established to analyze evolution and roles of MCSs during NRB and NRMA. • Combination of diagnosis and simulation successfully revealed the macro and micro physical mechanism of NRB and NRMA. [ABSTRACT FROM AUTHOR]

The Nb-Ta-Zr-Hf-REY-Ga mineralization in the Late Permian coals in southwestern China has been well investigated by several studies and has generally been attributed to alkaline pyroclastics coupled with input from hydrothermal fluids. The Late Triassic is one of the important coal-forming periods but the critical element mineralization in coals of this geological age has not been well documented. In this paper, the mechanism of Nb-Ta-Zr-Hf-REE-Ga-Th-U mineralization in the K5 coal seam of the Upper Triassic Xujiahe Formation from the Gaosheng Mine, Sichuan Basin, southwestern China, was investigated. The K5 coal is a high-ash, low-sulfur, and low-volatile bituminous coal. The minerals in this coal include illite, kaolinite, quartz, and, to a lesser extent, anatase, calcite, chamosite, bassanite, and pyrite, along with traces of ankerite, rutile, and zircon. Compared with the averages of common world hard coals, the studied coals are enriched in critical elements including Zr (247 ppm), Hf (5.56 ppm), Nb (23 ppm), Ta (1.55 ppm), rare earth elements and yttrium (REY, 168 ppm), Ga (18.3 ppm), Th (14.1 ppm), and U (6.18 ppm) (all on a whole coal basis). The Al 2 O 3 /TiO 2 ratios, Eu anomalies, and the relationships of Al 2 O 3 /TiO 2 vs. Zr/TiO 2 and Nb/Yb suggest that the sediment-source rocks of the Gaosheng coals were Neoproterozoic and Early-Middle Triassic felsic-intermediate igneous rocks from the southeastern Qinling and Longmenshan Orogens, along with the Hannan and Micangshan-Dabashan Uplifts. Other probable sources are contemporaneous felsic-intermediate pyroclastics from the Late Triassic volcanic areas around the Sichuan Basin (i.e., East Kunlun Orogen, West Qinling Orogen, and East Tibetan Plateau). The relationships of Al 2 O 3 /TiO 2 vs. Zr/Al 2 O 3 , Al 2 O 3 /TiO 2 vs. Nb/Al 2 O 3 , Ga/Al 2 O 3 , and Al 2 O 3 /TiO 2 vs. LREY/Al 2 O 3 further indicate that the elevated concentrations of Nb(Ta)-Zr(Hf)-REY-Ga in the Gaosheng coal are probably sourced from both the erosion of sediment-source regions and contemporaneous pyroclastics. The illite-kaolinite aggregates with a vermicular texture and authigenic illite, quartz, anatase, pyrite, calcite, ankerite, barite, and REE-rich minerals, REY distribution patterns, as well as elemental variation trends of the coal seam, collectively indicate that the studied coals were likely influenced by multiple-stage infiltration of various solutions. These solutions leached the fresh pyroclastics and products of erosion derived from granites in the sediment-source regions, leading to redistribution of the critical elements (e.g., Zr, Nb, and HREY) between the roof, floor, and parting mudstones and the coal benches. The concentrations of (Nb,Ta) 2 O 5 , (Zr,Hf) 2 O 5 , and Ga in the coals are 107, 1093, and 57.6 ppm, respectively, close to or higher than the marginal grade of conventional ore deposits for these elements, and thus the Gaosheng coals have potential as raw materials for the recovery of the critical metals Nb, Ta, Zr, Hf, and Ga. [Display omitted] • The coal contains elevated concentrations of Nb, Ta, Zr, Hf, REE, Ga, Th, and U. • The sediment-source region of the coals was felsic-intermediate igneous rocks. • Elevated concentrations of critical elements in coal due to products of erosion and pyroclastics. • The coals are likely influenced by the multiple-stage infiltration of acid solutions. • The acid solutions leached the fresh pyroclastic and terrigenous materials. [ABSTRACT FROM AUTHOR]

The Emei Shan stands on the southeast side of the Longmen Shan. It marks the southeastern most edge of the eastern margin of the Tibetan Plateau (EMTP) and towers above the Sichuan Basin to its east, with the highest peak being 3099 m. A large number of structural and thermo-chronological studies have been published focused on the Longmen Shan orogen, which is considered to be the northern part of the EMTP. However, for the southern part of the EMTP where the Emei Shan lies, its tectonics and uplift history are still poorly understood. This paper dates five granite samples from the Emei Shan batholith using the apatite fission track (AFT) method. The boundary faults of the Emei Shan and structural deformation in adjacent region are also investigated and mapped in detail. (1) In Miocene time, compressional stress from the eastward extrusion of the EMTP caused large-scale thrusting and mountain uplift along narrow Longmen Shan in northern EMTP, in contrast to southern EMTP where a broad and gentle Yaan−Emei Shan fold belt absorbed most of the stress. By Pliocene time, the southeastward extrusion of the Tibetan Plateau caused the transpressional stress and rotated the Chuandian fragment along the Xianshuihe−Xiaojiang fault belt. As a consequence, the Emei Shan region was intended northeastwards into the Sichuan Basin, bounded by two strike-slip faults on its north and southeast sides. (2) The AFT results show the Emei Shan uplifted since ∼25–20 Ma ago. The threshold and main stage of uplift of the Emei Shan possibly lagged behind the Longmen Shan of approximately 5 Myr. As the leading edge of fold belt, uplift of the Emei Shan indicated the eastward propagation of the EMTP was time-transgressive from Late Oligocene to Middle Miocene. [ABSTRACT FROM AUTHOR]