桂西地区上二叠统硅质岩地球化学特征及对本区烃源岩发育潜力的指示意义  

Geochemistry of the Upper Permian chert in the western Guangxi and its impact on forming hydrocarbon source rock

作　　者：邱振[1,2] 王清晨[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国科学院研究生院,北京100049

出　　处：《地质科学》2011年第1期52-67,共16页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究发展计划项目01课题"中国海相碳酸盐岩层系形成与后期演化"(编号:2005CB422101);国家科技重大号项"深层油气成藏规律;关键技术及目标预测"项目01课题(编号:2008ZX05008-01)资助

摘　　要：通过对桂西地区南丹龙王坡11件上二叠统硅质岩样品和平果四塘6件上二叠统硅质岩样品的主量和微量元素分析研究,并结合已发表的崇左东攀剖面大隆组的硅质岩地球化学数据,认为桂西地区上二叠统硅质岩为生物成因,形成于受陆源碎屑影响的大陆边缘沉积环境,其沉积水体为氧化条件。研究区内硅质岩的TOC为0.10%～0.19%,平均为0.15%,与扬子北缘硅质岩(TOC可达18%)相比明显偏低,基本不发育烃源岩。对两地区晚二叠世时期生产力水平和沉积水体的氧化还原条件的对比研究表明,氧化的沉积水体是限制桂西地区上二叠统硅质岩成为烃源岩的主控因素。Based on analyzing major and trace elements of 17 samples from the Upper Permian cherts of the Longwangpo section, Nandan （ 11 samples） and the Sitan section, Pingguo （6 samples） in the Western Guangxi, and combined with the published geochemical data of cherts from the Dalong Formation of the Dongpan section, Chongzuo,the conclusion has been proposed in this paper that the origin of the Upper Permian cherts in the Western Guangxi was biogenic and they were deposited in the continental margin with influence of terrigenous materials and under oxic condition. The total organic concentration （TOC） of cherts study area ranges from 0. 10% to 1. 19% , with an average value 0. 15 % , which is lower than that of cherts from the Northwestern Yangtze block （as high as 18% ）indicating that the Upper Permian cherts in the Western Guangxi are not hydrocarbon source rocks. Comparing the paleoproductivity and paleoredox conditions of the study area with those of the Northwestern Yangtze block,we conclude that oxic depositional condition of the Upper Permian cherts in study area was the major controlled factor limiting them to be hydrocarbon source rocks.

关 键 词：硅质岩 上二叠统 地球化学 烃源岩 桂西地区 

分 类 号：P588[天文地球—岩石学] TE121[天文地球—地质学]