Study On Potassium-rich Mechanism Of Brines In Triassic Of Sichuan Basin

Potassium-salt is an important mineral resource and widly used in industry and agriculture.With the development of China's economy.The demand for potassium has been increasing,and the corresponding exploration has been carried out on a large scale.The Sichuan Basin is a large sedimentary basin with lots of abundant underground potassium-rich brine resources,especially in the Lower and Middle Triassic Jialingjiang Formation and the Leikoupo Formation.Potassium-rich brine is a kind of liquid mineral with great development value.It is of great theoretical and practical significance to analyze the mechanism of potassium enrichment in potassium-rich brine.In this paper,the northeastern Sichuan Basin is taken as an example,the hydrogeochemical characteristics of the Middle and Lower Triassic brine in the Sichuan Basin has been discussed,including the chemical composition of the brine,the characteristics of salinity and conventional components of water chemistry,ion scale coefficient characteristics,hydrogen and oxygen isotope characteristics,and comparison of various conventional components with seawater evaporation curves.based on the collection of the evolution history of the Sichuan Basin,the lithologic changes of the Triassic,the tectonic development and the hydrogeological conditions of the basin.The evolution of salt brine was traced back through the water chemistry characteristics,and the effects of different hydrogeochemical processes on the composition of salt brine were discussed.Finally,the preservation and potassium-rich conditions of potassium ions in potassium-rich brines were investigated.The hydrochemistry type of potassium-rich brine in northeastern Sichuan basin is mostly Cl-Na type,and the potassium ion content is different.The concentration of potassium ion is positively correlated with salinity,sodium ion and chloride ion.Through?Na/?Cl,Br×10~3/C1 plasma proportional coefficient,and?D,?18O isotope characteristics analysis,it is concluded that the potassium-rich brine in northeastern Sichuan basin originated from ancient seawater.Comparing the content of each water chemical component in the brine with the evaporation and concentration curve of seawater,it can be seen that the formation of deep potassium-rich brine is not simply concentrated by evaporation of seawater.In some hot spring waters in northeastern Sichuan,the K~+content in water chemical composition reaches the potassium-containing standard,but K~+is not enriched due to atmospheric precipitation.The evolution of salt brine in northeastern Sichuan can be summarized into three stages.The water-rock reaction occurred in each stage has a great influence on the chemical composition of brine:(1)the stage of primitive sedimentary water formation:evaporation and concentration of ancient seawater,volcanism,freshwater mixing Miscellaneous.(2)Sedimentary water closed burial stage:an important stage in the formation of brine components.During the period,there are mainly leaching desalination,biochemical action,compaction and dehydration,and dolomitization.(3)Post-reformation stage:Part of the strong structural area,the sedimentary water can increase the potassium ion in the brine through the structure,the fracture,etc.,and the potassium-rich minerals in the surrounding salt layer which are dissolved by the salt brine.The enrichment of potassium ions in the potassium-rich brine in northeastern Sichuan mainly includes two stages:one is the evaporation and concentration of paleo-sea water,and the other is the dissolution of potassium-containing minerals in the late stage leaching stage.