库车盆地中始新统岩盐氯同位素特征及其成钾指示意义  

Chlorine isotopic characteristics of the Middle Eocene rock salt in the Kuqa basin and their implications for potash formation

作　　者：徐洋 张永明[2] 曹养同[3] XU Yang;ZHANG Yongming;CAO Yangtong(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,Jiangxi 330013,China;Qinghai Institute of Salt Lake,Chinese Academy of Sciences,Xining,Qinghai 810008,China;MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]东华理工大学,核资源与环境国家重点实验室,江西南昌330013 [2]中国科学院青海盐湖研究所,青海西宁810008 [3]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《地质学报》2021年第11期3492-3500,共9页Acta Geologica Sinica

基　　金：中国地质科学院基本科研业务费项目(编号YYWF201716);国家自然科学基金项目(编号41902064、41602100);东华理工大学博士科研启动基金(编号DHBK2018029)联合资助的成果。

摘　　要：评判盐湖卤水蒸发浓缩阶段对指示成钾具有重要的意义,由于库车盆地始新统含盐系地层岩盐溴氯比值很低,导致这种传统的找钾地球化学指标方法受限。然而,得益于近年来稳定同位素的快速发展,氯同位素组成可以很好地指示含盐系的蒸发阶段。本文以库车盆地DZK01钻孔13个原生石盐岩为研究对象,分析结果显示,δ^(37)Cl值均为负值,介于-1.20‰~-0.51‰之间;KCl含量介于0.13%~0.29%之间。在剖面上从下往上,δ^(37)Cl值有升高的趋势,KCl含量有降低趋势,指示了库车盐盆中始新世古卤水经历了一个逐渐淡化的演化过程。早期卤水蒸发浓缩程度较高,并析出钾盐或含钾矿物;晚期卤水蒸发浓缩程度较低,较少发现甚至未发现钾盐或含钾矿物。此外,库车盐盆中始新统蒸发岩系的成盐物质主要为海相来源,且蒸发浓缩程度较高,具有较好的成钾前景。Judging the evaporation concentration stage of salt lake brine is of great significance for indicating potassium formation.The low Br/Cl ratio in the Eocene salt-bearing strata in the Kuqa basin reveals the limitation of this traditional method of finding potassium geochemical indicators.However,thanks to the rapid progress in applications of stable isotopes in recent years,chlorine isotopic composition can be a good indicator of evaporation stage of salt-bearing.This paper takes 13 primary rock salt from core DZK01 of Kuqa basin as the research object.The analysis results show thatδ^(37)Cl values are all negative values,ranging from-1.20‰to-0.51‰and KCl content is between 0.13%and 0.29%.From bottom to top in the section,the values ofδ^(37)Cl tend to increase,and KCl content tends to decrease indicating that the middle Eocene ancient brine in the Kuqa salt basin has undergone a gradual dilution evolution process.The early stage brine had a higher degree of evaporative concentration,and sylvite or potassium-containing minerals were precipitated.The late stage brine had a lower degree of evaporative concentration,and few or no sylvite or potassium-containing minerals arefound.In addition,salt-forming materials of middle Eocene evaporite series in the Kuqa Salt Basin are mainly marine sources,with higher degree of evaporation and concentration indicating a superior prospect for potassium formation.

关 键 词：卤水演化阶段 氯同位素 中始新统 岩盐 库车盆地 

分 类 号：P619.211[天文地球—矿床学]