塔里木盆地古城地区奥陶系鹰三段硅质岩地球化学特征及成因  

Origin and geochemical characteristics of siliceous rocks in the third Member of Yingshan Formation in Gucheng area,Tarim Basin

作　　者：王珊[1] 曹颖辉[1] 张亚金[2] 杜德道[1] 徐兆辉[1] 杨敏[1] 赵一民[1] WANG Shan;CAO Ying-hui;ZHANG Ya-jin;DU De-dao;XU Zhao-hui;YANG Min;ZHAO Yi-min(PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;PetroChina Daqing Oilfield Company,Daqing 163712,China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]大庆油田有限责任公司勘探开发研究院,黑龙江大庆163712

出　　处：《天然气地球科学》2020年第5期710-720,共11页Natural Gas Geoscience

基　　金：中国石油天然气股份有限公司“十三五”专项“古老碳酸盐岩油气成藏分布规律与关键技术”(编号:2019B-04);中国石油重大科技专项“塔东天然气成藏理论及勘探配套技术研究”(编号:2016E-0204)联合资助.

摘　　要：奥陶系鹰三段是塔里木盆地古城地区的主力储集层段,但硅质岩发育,导致储层变差。镜下观察揭示研究区硅质岩主要为残余结构硅质岩;地球化学分析结果显示硅质岩在Al-Fe-Mn三角图中位于热液沉积区域,且Al/(Fe+Mn+Al)值、(Fe+Mn)/Ti值、Y/Ho-Th/U关系、ΣREE值、LREE/HREE值、δCe值及δEu值均与热液成因的硅质岩地球化学指标相吻合;同时Si同位素、O同位素及其相关关系与交代成因的硅质岩和成岩石英的地球化学指标相吻合。以上特征表明,研究区硅质岩为成岩后的热液交代成因。结合区域地质资料,研究区早加里东期发育断穿基底的NE向断裂,为热液流体提供了运移通道。二叠纪末期,塔里木盆地发生大规模的火山活动,为碳酸盐岩的硅化提供了热液和硅质来源。硅质热液沿NE向断裂及其伴生裂缝广泛进入鹰三段与碳酸盐岩发生反应,硅质热液交代碳酸盐岩沉积物并沉淀形成硅质岩。The 3rd Member of Yingshan Formation is a main reservoir section in Gucheng area of Tarim Basin,but the development of siliceous rock destroyed the reservoir to a certain extent.The siliceous rocks in the study area are mainly residual structural rocks.The results of geochemical analysis show that the siliceous rocks are lo⁃cated in the hydrothermal sedimentary area in the Al-Fe-Mn diagram,and the values of Al/(Fe+Mn+Al),(Fe+Mn)/Ti,Y/Ho-Th/U,ΣREE,LREE/HREE,δCe andδEu are consistent with the geochemical index⁃es of hydrothermal sedimentary siliceous rocks.The Si isotopes,O isotopes and their correlation are consistent with the geochemical indexes of metasomatic siliceous rocks and diagenetic quartz.The above characteristics in⁃dicate that the siliceous rocks of the 3rd Member of Yingshan Formation in the study area are formed by hydro⁃thermal metasomatism after diagenesis.Combined with the regional geological data,the NE trending faults that break through the basement developed in Early Caledonian Period,providing a migration channel for the hydro⁃thermal fluid.At the end of Permian,large-scale volcanic activities took place in Tarim Basin,which provided hydrothermal and siliceous sources for silicification of carbonate rocks.The siliceous hydrothermal fluid entered the 3rd Member of Yingshan Formation along NE-trending faults and its associated fractures and reacted with car⁃bonate rocks.The siliceous hydrothermal fluid replaced carbonate sediments and precipitated to form siliceous rocks.

关 键 词：硅质岩 古城地区 鹰三段 地球化学 热液 

分 类 号：TE122.113[石油与天然气工程—油气勘探]