Water-rock Reaction Simulation Of The Mesozoic Igneous Rocks In Jitai Basin,Jiangxi Province And Its Implication For Genesis Of Potassium-lithium-rich Brine

The content of potassium chloride in the undergraound brine in Jitai Basin,Jiangxi Province is close to 1%,and the concentration of lithium chloride is over 600mg/L,both are close to or exceed the industrial and has high comprehensive utilization value.Scientific research on the source and enrichment process of ore-forming materials in basin brine is of great significance for establishing the potassium-lithium-rich brine mineralization model and guiding the prospecting work of the same type of of potassium-lithium-rich brine.The Mesozoic magmatic rocks distributed in and around the basin are rich in potassium,lithium,rubidium and bromine,which may be the main source of brine mineralization in the basin.However,the specific metallogenic relationship between them and the enrichment mode of metallogenic materials have not been ascertained yet.On the basis of previous studies,by applying mineralogical,petrological,geochemical,fluid inclusion studies and high-pressure autoclave water-rock reaction simulation experiments on Mesozoics igneous rocks in Jitai Basin and its surrounding areas,we focuse on the effects of time,temperature and fluid concentration on the water-rock reaction of igneous rocks,and its significance for the source and genetic mechanism of potassium-lithium-rich brine.The following conclusions are obtained based on the above studies:?1?The brine in Jitai basin is characterized by high lithium and low magnesium content.The composition of brine is similar to that in adjacent Jiangling Depression and Qianjiang Depression,indicating that the genesis of brine in Jitai basin is also controlled by volcanic activity.?2?The magma of the Jitai Basin has been differentiated to varying degrees,the igneous rocks with strong alteration indicate that the metasomatism of underground hydrothermal fluid to igneous rocks is strong in the study area,and igneous rocks provide material sources for potassium-lithium-rich brine deposits through water-rock reaction.The Mesozoic igneous rocks in Jitai Basin are mainly granite and basalt.The granite is rich silicon,peraluminium and over-alkaline,which is beneficial to the enrichment of lithium,and may provide lithium elements for brine.Basalt is poor in sodium and slightly rich in potassium,which may be the source of potassium in brine.?3?Fluid inclusions in granite are mainly secondary pure liquid phase and rich liquid phase,and the volume of inclusions is small.No salt sub-minerals are found,and it is presumed that the fluid salinity is not saturated.The temperature of fluid activity is relatively high,and the homogenization temperature is concentrated in 170²30°C,and the main source of fluid is atmospheric precipitation.?4?The leaching ability of fluids to elements under heating condition is significantly enhanced compared with that at room temperature,the leaching ability of fluids to K,Li and other elements is stronger than that of Mg,Sr etc.Temperature is the main controlling factor for fluid leaching ability of elements,and high salinity fluids are the main migration carriers of ore-forming elements.?5?The amount of Mg²⁺dissolution in the basin granite is very small under heating condition,which is conducive to the formation of high Li and low Mg brine,indicating that the granite is closely related to the source of Li in brine.The leaching capacity of fluids to K⁺in basalt is about 2 times higher than that of granite,indicating that basalt is the main source of K in brine.?6?The Mg/Li values in surface brine is mainly controlled by original rock composition.Temperature is one of the key factors to control Mg/Li value of fluid in water-rock reaction in autoclave.The formation of lithium-rich brine takes a long time.Water-rock reaction is one of the important processes of brine formation,but it cannot directly form the deposits,surface evaporation and concentration is the main mechanism for brine mineralization.