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Karst spring water dynamic characteristics and its response to atmospheric precipitation are of great significance for water resources utilization under the background of climate change. This paper selects Longzici spring area, North China, as the study area. Based on a long series of spring water flow and precipitation data, the dynamic characteristics of spring flow were analyzed and the numerical simulation of the groundwater flow model was established. The results show that the groundwater kept the sustained decline over the past decades which is in a negative equilibrium state, with a storage variable of − 2.26 million m3/year. The sensitivity of spring flow to precipitation under different precipitation scenarios shows that the water level changes in the recharge and drainage areas are similar about (3–5 cm) and slightly larger than that in the runoff area(1.5 cm) when minimum rainfall (287.24 mm) happens. When the precipitation is at its maximum (867.66 mm), the water level change in the runoff area can reach 95 cm which is much larger than those in the recharge and discharge areas. The results indicate that Longzici karst spring has a relatively good regulation water resource capacity and the runoff area is more sensitive which plays an important role in response to climate change. [ABSTRACT FROM AUTHOR]

This paper studies the mineralization process and the ore-forming setting of the Kantian fluorite deposit in South China through the zircon U-Pb chronology, quartz Rb-Sr dating, whole rock geochemistry, H-O isotope and fluid inclusions. A mineralization model for the Kantian fluorite deposit is proposed as follows: The subduction of the Pacific plate during the late mid-Jurassic and late Jurassic led to the formation of several fault zones. As the subduction gradually decelerated and eventually ceased, continental extension and lithosphere thinning occurred, accompanied by upwelling of the asthenosphere. This asthenosphere upwelling facilitated melting of the lithospheric mantle, resulting in the ascent of magma into the lower crust. Consequently, the intrusion of magma into the lower crust caused substantial heat, triggering partial melting of the lower crust. The molten material then ascended along faults, generating a significant quantity of granites. During the Early Cretaceous period, the Yanshan cycle witnessed another notable phase of magmatic activity. The residual magmatic hydrothermal fluid from this period served as a source of heating, while the pre-existing fault structures provided favorable pathways and storage space. Atmospheric precipitation infiltrated into the depth along these faults, and the deep-seated residual magmatic hydrothermal fluid heated the infiltrated atmospheric water, inducing cyclic upwelling. The upward migration of hydrothermal fluid continuously extracted Ca and F elements from the granites. Ongoing interaction between the fluid and the surrounding rocks led to changes in pH, coupled with alterations in temperature and pressure, ultimately resulting in the precipitation of fluorite with associated alteration zones in the surrounding rocks. [Display omitted] • Ca and F element in the fluorite were derived through the surrounding rocks. • The ore-forming fluids belong to the NaCl-H 2 O system and exhibit characteristics of medium–low temperature, low salinity, and low density, and were derived from meteoric water. • The intrusion age of surrounding rock in Kantian fluorite deposit was 159.4 ± 2.2 Ma, and the ore-forming of fluorite was 135.6 ± 0.7 Ma. • The tectonic setting responsible for the diagenesis and mineralization processes is believed to be an intracontinental stretching environment associated with the subduction of the Pacific plate. The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H 2 O, with minor C 3 H 6. Isotope analysis indicated δD VSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18O VSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H 2 O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit. [ABSTRACT FROM AUTHOR]