Genesis of the Ordovician fluorite and its geological significance in central uplift of the Tarim basin, China

Based on analysis of karst fractured-vuggy filling mineralogy and geochemical fluorite in the Hercynian, further research was carried out regarding the formation and significance of fluorite in the Central Uplift of the Tarim Basin. The Hercynian fractured-vuggy and filling succession of fracture-cave minerals were developed under a mixed background of low-temperature magmatic hydrothermal fluid and upper strata brine. An overlapping and associating relationship exists between the generation of fluorite and the buried dissolution or oil and gas migration. The fluorite volume decreased by 26.4 % after the calcite had been metasomatized by fluorite, resulting in plentiful intergranular spaces, which formed an appreciable reservoir space. At the same time, the hydrothermal fluid carried by fluorite eroded adjacent rock through fractures or fissures, forming an irregular fracture-cave system, accompanied by hydrocarbon migration. The hydrocarbon migration and accumulation occurring in the Late Hercynian–Indosinian are closely related to the sedimentation of fluorite and several hydrothermal minerals.