中哈边境伊犁地区中二叠统沉积环境的地球化学判别

发布时间：2018-05-30 22:28

本文选题：伊犁地区 + 铁木里克组　；参考：《地质学报》2017年04期

【摘要】：细粒沉积物中的暗色泥岩是利用地球化学指标进行沉积环境分析的最有利载体之一。中哈边境伊犁地区中二叠世泥岩较为发育,厘定泥岩形成时的沉积环境对其是否可以成为烃源岩和其生成油气潜力十分关键。本次研究主要从暗色泥岩主量元素、微量元素分析、稀土元素分析结果为基础,选用对沉积环境反映比较敏感的元素,分析研究区地层中微量元素含量及其比值与沉积介质环境之间的对应关系,进而探讨伊犁地区中二叠世沉积期的湖盆气候条件、盐度、氧化还原条件等沉积环境特征。研究结果表明:[m(Sr)/m(Ba)]、[m(B)/m(Ga)]和硼质量分数(w(B))共同反映出伊犁地区中二叠世为较咸水—咸水的沉积环境,且从早期的晓山萨依期向晚期的铁木里克期湖盆古盐度逐渐升高;U、Th/U和V/(V+Ni)揭示出伊犁地区中二叠统为缺氧环境下的产物,沉积环境为水体分层不强的厌氧环境—水体分层及底层水体中出现H_2S的厌氧环境的过渡;依据中二叠世泥岩北美页岩标准化分布推测当时沉积应为化学风化作用较弱的较干燥气候,同时水体可能较安静。综上分析认为:伊犁地区中二叠世处于干燥缺氧的咸水环境,且从早到晚沉积环境水体的还原性逐渐增强,盐度逐渐增高。
[Abstract]:Dark mudstone in fine-grained sediments is one of the most favorable carriers for sedimentary environment analysis based on geochemical indicators. The Middle Permian mudstone is relatively developed in the Yili area on the border of China and Kazakhstan. The sedimentary environment of mudstone formation is very important to whether the mudstone can become source rock and its hydrocarbon generation potential. Based on the main elements of dark mudstone, trace element analysis and rare earth element analysis, the elements which are sensitive to sedimentary environment are selected in this study. The relationship between the trace element content and the ratio of trace elements in the strata and the sedimentary medium environment in the study area is analyzed, and the sedimentary environment characteristics of the lake basin climate, salinity, redox conditions and so on during the Middle Permian sedimentary period in Yili area are discussed. The results show that the middle Permian epoch in Yili area is the sedimentary environment of saltwater and brackish water. Moreover, the paleosalinity of the lake basin increased gradually from the early period of Xiaoshan Say to the late period of Fermulik period. It was revealed that the Middle Permian in Yili area was the product of anoxic environment. The sedimentary environment is the anaerobic environment with weak stratification of water body and the transition of the anaerobic environment in which there is H2S in the bottom water. According to the standardized distribution of Middle Permian mudstone and North American shale, it is inferred that the deposition at that time should be a dry climate with less chemical weathering, and the water may be quiet. It is concluded that the middle Permian in Yili area was in a dry and anoxic saltwater environment, and the reduction and salinity of the water body in the sedimentary environment gradually increased from early to late.
【作者单位】：中国地质调查局西安地质调查中心国土资源部岩浆作用成矿与找矿重点实验室中国地质调查局造山带地质研究中心;
【基金】：中国地质调查局地质调查项目(编号:DD20160172、DD20160200) 国家自然科学基金项目(批准号:41502081)共同资助的成果
【分类号】：P618.13;P534.46

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