经典电视剧高清无广告播放网站 ,av免费网站_高清全集在线观看

Abstract: The Fengcheng Formation in the Hashan area, located on the northwestern margin of the Junggar Basin, represents a saline-alkaline lake facies with fine-grained mixed sedimentation. This formation is rich in alkaline minerals and serves as a high-quality source rock for hydrocarbon generation in alkaline lakes. However, its lithology is complex, and the origins of the salt minerals remain unclear. This study focuses on the salt minerals in the Fengcheng Formation of the Hashan area. Using core observation, thin section identification, scanning electron microscopy, electron probe micro-analysis, trace and rare earth element analysis, stable isotope analysis, fluid inclusion analysis, and zircon U-Pb dating, the sedimentary age of Fengcheng Formation and the mineralogical and geochemical characteristics of salt minerals were systematically studied. The salt minerals identified in the Fengcheng Formation include calcite, dolomite, eitelite, northupite, shortite, reedmergnerite, and Na-carbonate. According to the different types of salt minerals, the different contact relations between minerals, the different production positions and production styles of mineral combinations, the salt mineral assemblage in the study area is classified into three categories: The combination of calcite, dolomite, shortite, and reedmergnerite, The combination of Na-carbonates, eitelite, shortite, and reedmergnerite, The combination of dolomite, eitelite, shortite, and northupite. Two zircon U-Pb ages, 307.8 ± 2.7 Ma and 308.5 ± 3.5 Ma, span the Carboniferous-Permian boundary, corresponding to an interglacial period within the Late Paleozoic Ice Age, aligning with the development of salt minerals. Salt minerals have the formation modes of sedimentation, replacement and hydrothermal transformation. Terrestrial weathering products, atmospheric, volcanic and hydrothermal processes, residual seawater, clay mineral transformation, thermal evolution of organic matter and tuffaceous alteration are material sources. The salt-forming fluid has the characteristics of weak acid-alkaline, medium-low temperature and high salinity, and is mainly driven by subduction zone high pressure, magmatic heat and gravity. The burial depth, temperature and CO2 concentration required for the formation of salt minerals were clarified, and the evolution sequence of salt-forming fluids from sedimentation to diagenesis and accompanied by hydrothermal (hot water) activities was summarized. The evolution model of salt minerals controlled by different genesis from the first member to the third member of Fengcheng Formation was established. The research findings are significant for understanding the paleoenvironment of the Fengcheng Formation, the formation mechanisms of high-salinity lakes, and the salt formation models.