大兴安岭南部晚二叠世沉积岩稀土元素和微量元素地球化学特征  

Geochemical characteristics of the rare earth and trace elements in Late Permian sedimentary rocks of South Daxing’anling

作　　者：黄清华[1] 朱政源 程宏岗[2] 王辉[1] HUANG Qinghua;ZHU Zhengyuan;CHENG Honggang;WANG Hui(Exploration and Development Research Institute of Daqing Oilfield Co Ltd,Daqing 163712,China;Langfang Branch of PetroChina Research Institute of Petroleum Exploration and Development,Langfang 065007,China)

机构地区：[1]大庆油田有限责任公司勘探开发研究院,黑龙江大庆163712 [2]中国石油天然气股份有限公司勘探开发研究院廊坊分院,河北廊坊065007

出　　处：《大庆石油地质与开发》2019年第6期1-11,共11页Petroleum Geology & Oilfield Development in Daqing

基　　金：中国石油天然气股份有限公司重大科技专项“松北深层天然气富集规律、勘探技术研究与规模增储”(2016E-0203)

摘　　要：大兴安岭南部地区晚二叠世林西组分布广泛,暗色泥岩发育,是重要的烃源岩,但长期以来其环境归属存在较大分歧。对林西县官地镇的林西组下部沉积岩进行了系统的稀土元素和微量元素分析。结果显示:灰岩稀土元素w(∑REE)为(13.31~115.1)×10^-6,平均为62.05×10^-6,远小于同期泥岩样品的平均值154.0×10^-6;轻稀土相对于中稀土、重稀土略亏损,灰岩δEu显著正异常(0.93~2.31,平均值1.53)、泥岩δEu弱负异常(0.83~0.96,平均值0.90),灰岩、泥岩δCe均为正异常(灰岩0.99~1.23,平均值1.11;泥岩0.98~1.05,平均值1.01),显示与正常海相和淡水湖泊相不同的稀土元素配分模式;灰岩中微量元素质量分数小,但其变化幅度较暗色泥岩大,灰岩具有Sr富集、Ba亏损的特点, Cu、Zn、Rb、Zr等微量元素质量分数与石英砂屑体积分数呈正相关;灰岩中δEu和δCe正异常,暗示存在热液作用活动和强的还原介质条件;沉积岩中log(δCe)平均值为0.027,远大于氧化-还原环境的判别指标值-0.1,且w(V)/w(Cr)大于5.14、w(V)/w(V+Ni)大于0.90,进一步证实林西组沉积时期主体为强还原环境。Late-Permian Linxi Formation in South Daxing’anling is characterized by wide distribution and abundant dark mudstone, which is the important source rock;however there is long-term serious debate on the sedimentary environment. The systematical analyses were conducted for the rare earth elements and trace elements in Linxi-Formation sedimentary rocks of Guandi Town of Linxi County. The results show that the total concentration of ∑REE in the limestone ranges from 13.31×10^-6 to 115.1×10^-6, with the mean of 62.05×10^-6, much less than the mean of 154.0×10^-6 of the mudstone in the same period;compared with MREE and HREE, LREE deficit was observed, the limestone with the notable positive δEu anomaly ranges from 0.93 to 2.31, the mean is 1.53, the mudstone rock with the weak negative δEu anomaly ranges from 0.83 to 0.96, the mean is 0.90, the positive δCe anomalies for the limestone and mudstone are respectively from 0.99 to 1.23 and from 0.98 and 1.05, their means are respectively 1.11 and 1.01, thus the different distribution patterns are shown from the patterns of the normal marine and freshwater lacustrine facies;the mass fraction of the trace element in the limestone is rather smaller, but the variation range is bigger than that in the dark mudstone, the limestone is characterized by rich Sr and poor Ba, the mass fractions of the trace elements such as Cu, Zn, Rb, Zr and so on are positively correlated with the volume fraction of the quartz detritus;the positive δEu anomaly and positive δCe anomaly in the limestone suggest that the hydrothermal activities and extremely reducing media condition are presented;the mean of log(δCe)in the sedimentary rock is 0.027, this value is far bigger than the identifying index(-0.1) of the oxidizing-reducing environment, and moreover V/Cr(more than 5.14) and V/(V+Ni)( more than 0.90) have further approved that the reducing environment was mainly shown in Linxi-Formation sedimentary period.

关 键 词：稀土元素 微量元素 地球化学特征 沉积岩 还原环境 晚二叠世 大兴安岭南部 

分 类 号：TE121.3[石油与天然气工程—油气勘探]