Geochemical Characteristics Of Potassium-rich Brine In Sichuan Basin And Its Genesis

This paper mainly rely on the project of China geological survey “Theenrichment regularity and survey and assessment of favorable area of potassium-richbrine in Triassic,Sichuan”.Potassium-rich brine of Sichuan basin is mainly occurrence in Jialingjiangformation and Leikoupo formation of Triassic,Through the research about The majorand trace elements and element characteristic ratio of reservoir in West Sichuan andmid Sichuan,then conclude the geochemical characteristics of potassium-rich brinereservoir in Sichuan basin;Through the research about The major and trace elementsand element characteristic ratio of potassium-rich brine in West Sichuan, Mid Sichuanand Est Sichuan,then conclude the geochemical characteristics of potassium-rich brineIn different research area.Finally, according to the isotopic characteristics andelement characteristic ratio of potassium-rich brine,we find three kinds of geneticmodels of brine,and then provide the reference for Sichuan Basin potash search.Through the field exploration, the sample collection of the strata rock andbrine,laboratory analysis and calculation, with the following main conclusions:1.the geochemical characteristics of reservoirPotassium of evaporate can relatively judgment the condition of salt forming,thew（K+)of West Sichuan and mid Sichuan are at the same level,w（K+) of FL1well isIncreasing with well depth;w(Mg) and w(Mg)/w(Ca) reflects the degree of originalseawater evaporation,Whether West Sichuan or mid Sichuan,the trend of w (Mg) andw(Mg)/w(Ca) is highly consistent, its value varies with the changes of reservoirtypes,Salt rock reservoir were significantly greater than carbonate reservoir;w（FeO）/w（Fe2O3）can distinguish the climate when seawater concentration,w(FeO)/w(Fe2O3) reflects the climate of West Sichuan was more dry and hot than mid Sichuan;w(MnO)/w(FeO+Fe2O3) is used to determine the corresponding liquid phase salinity，w(MnO)/w(FeO+Fe2O3) values are very small, so the corresponding liquid phase are hypersaline，the salinity of West Sichuan should be slightly higher than mid Sichuan；Finally, we establish the w(FeO)-w(Fe2O3)-w(MnO) identification of sedimentaryenvironment model，According to the w(FeO)-w(Fe2O3)-w(MnO) identification ofsedimentary environment model graph， all the research areas belong to the shallowwater sedimentary environment，West Sichuan has a better salt deposition conditionsbecause of the dry and hot climate.About the correlation of main elements,the K,Na correlation has a big differentbetween West Sichuan and Mid Sichuan,reflecting the sources of K and Na may bedifferent. About the trace elements,Sr/Ba characteristic is obvious, the West Sichuan <1, Mid Sichuan>1; Rb/Sr ratio are very low, reflecting the small rainfall during thedeposition.2.the geochemical characteristics of Potassium-rich brineThe K+of West Sichuan is very high, far beyond the brine K+industrial grade,theK+of East Sichuan and Mid Sichuan are at the same level(except the Chuan25well),and the Br are abnormal high in Mid Sichuan; trace elements B and Rb valueswere generally high, far beyond the value of potassium salt deposition stage witchconcluded from seawater evaporation experiments,Preliminary explain of the originalwater basin concentrated in a relative higher degree.Characteristics of ion coefficient in different parts is obvious different,theBr×103/Cl of West Sichuan and Mid Sichuan are at the same level.all＞10,and thevalue of East≤8,This may be related with the injection of atmosphericprecipitation;about the K×103/Cl,West＞East＞Mid;most of the nNa/nCl of WestSichuan and Mid Sichuan are＜0.87,Their sedimentary types maybe related with thedeposition of the original water；the nMg/nCl of East Sichuan are smaller than Westand Mid,Reflect the leaching characteristics of East Sichuan；The K/Br of WestSichuan is about20，East Sichuan is6—15，Mid Sichuan is1—6，reflecting the WestSichuan rich K and poor Br，Mid Sichuan rich Br and poor K.3.The brine type and establishment of genesis modelAccording to the hydrogen and oxygen isotope and Ion characteristiccoefficient,we divide brine into3types,they are:I.The original water andmetamorphism type brine(West Sichuan).II.Leaching of potassium rich brine(EastSichuan).III.Mixed potassium rich brine(Mid Sichuan),and establish the corresponding genesis model.