吉木萨尔凹陷芦草沟组碳酸盐岩碳氧同位素特征及其古湖泊学意义  

Carbon and Oxygen Isotope Compositions of Carbonatic Rock from Permian Lucaogou Formation in the Jimsar Sag,NW China and Their Paleolimnological Significance

作　　者：曲长胜 邱隆伟[1,2] 杨勇强 陈程[1,2] 汤丽莉 余宽宏 万敏 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,山东青岛266071 [3]中国石油新疆油田分公司勘探开发研究院,新疆克拉玛依834000

出　　处：《地质学报》2017年第3期605-616,共12页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划"973"项目(编号2014CB239002);山东省自然科学基金青年基金项目(编号ZR2014DQ016);中国石油大学(华东)研究生创新工程项目(编号YCXJ2016010)资助成果

摘　　要：吉木萨尔凹陷芦草沟组是准噶尔盆地重要的湖相碳酸盐岩致密油富集区,为明确其沉积时期古湖泊的环境特征,利用磷酸法对吉木萨尔凹陷芦草沟组碳酸盐岩样品进行了测试。测试结果表明,芦草沟组碳酸盐岩δ^(13)C值介于6.80‰~9.70‰之间,平均值为8.30‰;δ^(18)O值介于-11.90‰^-3.50‰之间,平均值为-6.20‰。δ^(18)O和δ^(13)C的特征及变化规律表明,早期古湖泊为淡水短期注入的畅流湖泊环境,后期古湖泊为水体长时间滞留、封闭性强的咸化湖泊体系。由于火山物质带来大量营养物质,有机生物十分繁盛,致使湖相碳酸盐岩δ^(13)C较重,富含低值氧同位素的大气降雨周期性输入引起湖相碳酸盐岩δ^(18)O显著降低。芦草沟组沉积时期古湖水具有咸化程度较高、变化频繁的特点,受大气降雨和强烈蒸发作用的影响,湖泊水位具有高—低—高或高—低的变化规律,受其影响湖泊盐度随之表现为低—高—低或低—高的变化规律。The Lucaogou Formation in the Jimsar sag is the important lacustrine tight oil-bearing accumulation in the Junggar basin. In order to understand the environmental characteristics of the paleolimnological deposition, experiments were carried out by means of phosphoric acid method on the Lucaogou Formation carbonate in the Jimsar sag. Results indicate that δ^13C values of carbonatic rocks range from 6. 8%0 to 9.7%0 with an average of 8. 3-0, and δ^8O from -11. 9‰ to -4. 3‰ with an average of -6. 2‰. Characters and variation of ~80 and δ18 CpDB indicate that paleolakes were characterized by open lake with short periodic fresh water injection during early stage and by highly saline lakes with long hydraulic residence time and high confine during late stage. Massive nourishment carried by volcanic materials gave rise to prosperous growth of organisms, resulting in high δ13C in lacustrine carbonatic rock, and cyclic input of precipitation bearing light oxygen isotope distinctly decreased δ^18O in lacustrine earbonatic rock. During sedimentation of the Lueaogou Formation, the paleolake was featured by high salinity with frequent variation. Influenced by cyclic precipitation and intensive evaporation, water level of paleolake varied from high to low to high or from high to low, and correspondingly, the salinity also varied from low to high to low or from low to high.

关 键 词：吉木萨尔凹陷 芦草沟组 碳酸盐岩 碳氧同位素 古沉积环境 

分 类 号：P618.13[天文地球—矿床学] P597[天文地球—地质学]