新疆库车盆地中始新世成盐演化特征——以KL4钻孔为例  

Salt-forming evolution characteristics of Middle Eocene in the Kuqa basin, Xinjiang: a case study of borehole KL4

作　　者：徐洋 刘成林[2] 曹养同[2] XU Yang;LIU Chenglin;CAO Yangtong(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,Jiangxi 330013,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7期2183-2192,共10页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41902064);东华理工大学博士科研启动基金(编号DHBK2018029);核资源与环境国家重点实验室自主基金(编号2020Z11)资助的成果。

摘　　要：古盐湖成盐演化具有多期次、连续性和淡化—咸化—盐化的周期性特征,系统研究成盐剖面的沉积韵律有利于恢复古盐湖成盐演化特征。本文以库车盆地KL4钻孔含盐系剖面及其74个石盐样品为研究对象,将含盐系剖面划分为4个成盐韵律,在此基础上开展岩相学、石盐元素地球化学以及石盐流体包裹体氢氧同位素分析等工作。结果显示:剖面上部Ⅲ和Ⅳ成盐韵律发育钾石盐、含钾石盐、杂卤石、钾石膏、钾芒硝等盐类矿物;K^(+)含量的分布范围为0.021%~0.158%,平均含量0.051%;石盐原生流体包裹体中氢氧同位素δD和δ~(18)O值范围分别为-78.2‰~-58.7‰和-2.4‰~1.3‰,平均值分别为-66.32‰和-0.80‰。盐湖卤水从早期到晚期蒸发浓缩程度逐渐升高,早期成盐卤水在晚期高浓度卤水的形成过程扮演了预富集的角色,在Ⅲ和Ⅳ成盐阶段发现3次钾盐析出事件。本研究为探讨库车盆地中始新世古盐湖环境、沉积特征以及成盐规律提供了重要依据。The salt-forming evolution of ancient salt lakes has periodic characteristics of multiple phases,continuity,and desalination-salinity-salinization.The systematic study of sedimentary rhythm fromthe salinization section is beneficial for thereconstruction of salt-forming evolution characteristics of ancient salt lakes.This paper investigates the salt-bearing section of borehole KL4 in the Kuqa basin and its 74 halite samples,and divides the salt-bearing section into 4 salt-forming rhythms.On this basis,work on petrographic characteristics,geochemical analysis of halite elements,and hydrogen and oxygen isotopes of halite fluid inclusions are carried out.The results show that(1)ⅢandⅣsalt-forming rhythms in the upper part of the section developed potassium,potassium-bearing halite,polyhalite,syngenite,glaserite and other salt minerals;(2)the distribution range of K^(+)content is 0.021%~0.158%,with an average value of 0.051%;(3)theδD andδ18O values of hydrogen and oxygen isotopes in halite primary fluid inclusions ranged from-78.2‰to-58.7‰and-2.4‰to 1.3‰,respectively,with average values of-66.32‰and-0.80‰,respectively;(4)the degree of evaporation and concentration of salt lake brine gradually increased from early to late,and the early salt-forming brine played a role in the pre-enrichment of the late high-concentration brine;(5)three potassium precipitation events were found in the third and fourth salt-forming stages.The results of this study provide an important basis for discussing the environment,sedimentary characteristics and salt-forming principles of Middle Eocene paleo-saline lake in the Kuqa basin.

关 键 词：地球化学 成盐演化 成盐韵律 中始新世 库车盆地 

分 类 号：P619.211[天文地球—矿床学]