库车盆地始新世盐湖物源及蒸发浓缩程度研究  

Provenance and Degree of Evaporation and Concentration of Eocene Salt Lake in the Kuqa Basin

作　　者：徐洋[1] 曹养同[1] 刘成林[1] 焦鹏程[1] XU Yang;CAO Yangtong;LIU Chenglin;JIAO Pengcheng(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037)

机构地区：[1]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》2018年第8期1617-1629,共13页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划"973"项目(编号2011CB403007)资助成果

摘　　要：古近纪塔里木盆地属于副特提斯海东延部分,而库车次级盆地位于其东北部。它古近纪经历了浅海相—海陆交互相—陆相的沉积演化,并发育了巨厚蒸发岩,是中国油气的重要产区和钾盐重点勘查区,长期以来受到广大地质学家的关注。然而,关于库车盆地始新世盐湖卤水来源及蒸发浓缩成钾的研究尚存在一些争议和不确定性。因此,本文基于岩石学和矿相学观察、X射线衍射和扫描电镜能谱分析以及稳定同位素研究,探讨蒸发岩的沉积环境、补给来源及蒸发浓缩程度。蒸发岩岩相学分析表明:蒸发岩形成于近源泥砾混入的盐湖沉积环境。硬石膏δ^(34)S值指示了具有一定海源补给特征。石盐原生流体包裹体δD和δ18 O值分别为-118.1‰^-95.3‰和2.5‰~5.7‰,蒸发趋势线说明了古卤水蒸发浓缩程度较高。古盐湖演化过程中虽然经历了3次短暂的淡水混入,但随着古盐湖持续的蒸发作用,并没有影响钾镁盐的析出,且在δ18 O值正偏较大时析出相应的钾盐或含钾矿物,推测库车盆地始新统含盐系地层具有良好的成钾潜力。The Tarim basin was the eastern extension of the Paratethys Sea during the Paleogene, with the Kuqa sub-basin located in the northeastern part of this basin. It experienced a sedimentary evolution from shallow marine, marine terrigenous to continent, resulting in deposition of giant evaporites. It has become an important base for oil-gas production and a key exploration area for potash deposits, thus having attracted wide attention from a large number of geologists. However, there are still some controversies and uncertainties about the source and degree of evaporation and concentration of Eocene ancient brine in the Kuqa Basin. Therefore, this study, based on observation of petrology and mineralogy, analysis of XRD and SEM-EDS and stable isotope characteristics, analyzed depositional environment, supply origin and degree of evaporation and concentration of the evaporite. Petrography analyses of evaporite show that it deposited in a salt lake environment mixed with addition of proximal mud. The anhydrite 834S values are characteristic of certain marine source supplement. The 8D and 818 O values of primary fluid inclusions from halite range from --118.1~0 to --95.3%0 and from 2.5X0 to 5.7~0, respectively, and the evaporation trend line indicates that the ancient brine had a high degree of evaporation and concentration. Although experiencing three transient freshwater influxes, the evolution of the ancient salt lakes did not affect the precipitation of potassium and magnesium saline minerals with continuous evaporation of ancient salt lakes, and the corresponding potassium saline minerals were precipitated when the 8180 values were positive. It can be speculated that Eocene salt-bearing series strata in the Kuqa basin has favorable potential for potash formation.

关 键 词：蒸发浓缩程度 稳定同位素 始新世 库车盆地 副特提斯 

分 类 号：P619.211[天文地球—矿床学]