鄂尔多斯盆地北缘书记沟中元古界长城系烃源岩地质特征  

Geological characteristics of source rocks of Mesoproterozoic Changchengian System in Shujigou area of the northern margin of Ordos Basin

作　　者：冯娟萍[1,2] 姚韦卓 欧阳征健 李文厚 FENG Juanping;YAO Weizhuo;OUYANG Zhengjian;LI Wenhou(College of Geology and Environment,Xi’an University of Science and Technology,Xi’an 710054,China;Geological Research Institute for Coal Green Mining,Xi’an 710054,China;Bailie School of Petroleum Engineering,Lanzhou City University,Lanzhou 730070,China;Department of Geology,Northwest University,Xi’an 710069,China)

机构地区：[1]西安科技大学地质与环境学院,陕西西安710054 [2]煤炭绿色开采地质研究所,陕西西安710054 [3]兰州城市学院培黎石油工程学院,甘肃兰州730070 [4]西北大学地质学系,陕西西安710069

出　　处：《西北大学学报（自然科学版）》2024年第6期950-960,共11页Journal of Northwest University（Natural Science Edition）

基　　金：国家自然科学基金青年项目(41502107)。

摘　　要：是否发育有效烃源岩是鄂尔多斯盆地中元古界成藏的关键。采用野外地质考察、显微薄片鉴定和地球化学分析等研究方法,对鄂尔多斯盆地北缘书记沟中元古界长城系阿古鲁沟组烃源岩地质特征展开研究。研究表明,阿古鲁沟组烃源岩为黑色含粉砂质泥质碳质板岩及黑色含电气石云母碳质千枚岩,原岩为黑色含砂页岩。烃源岩有机碳含量高,为0.34%~9.56%,平均值为3.3%;有机质类型以Ⅰ型和Ⅱ1型为主;R_(o)变化范围为3.57%~4.68%,平均值为4.09%;T_(max)值为404~562℃,处于以生成干气为主的过成熟阶段。稀土元素配分模式为轻稀土微富集、轻重稀土分异不明显的略微右倾型;δCe值为0.74~0.92,表现出Ce负异常;δEu变化范围比较大,为0.95~4.83,指示阿古鲁沟组烃源岩当时沉积时处于还原-氧化过渡环境。稀土元素、微量元素含量指示阿古鲁沟组烃源岩形成于滨浅海-台后盆地沉积环境。当时,气候温暖潮湿,间或出现短暂偏干热气候变化,水体具有一定深度,能量较小,为与北侧广海沟通有限的较闭塞贫氧-厌氧、咸水-微咸水还原环境,这种条件非常有利于烃源岩的形成。The development of effective source rocks is the key to Mesoproterozoic hydrocarbon accumulation in Ordos area.In this paper,the geological characteristics of the Agulugou Formation source rocks in Shujigou area were studied by means of field geological investigation,microscopic section identification and geochemical analysis.Researches show that the source rocks of Agulugou Formation are carbonaceous slate and phyllite,and the original rocks are black sand-bearing shale.The contents of organic carbon in the source rocks are high,and the value ranges from 0.34%to 9.56%,with an average of 3.3%.The types of organic matter are Ⅰ and Ⅱ1 kerogen.The value of R_(o) ranges from 3.57%to 4.68%,and the T_(max) value is from 404℃ to 562℃.These results show that the thermal evolution of source rocks is high,and is in the over-mature stage.The distribution pattern of rare earth elements is a slightly right-leaning pattern with slight enrichment of LREE and no obvious differentiation of LREE and HREE.The δCe values range from 0.74 to 0.92,showing a negative Ce anomaly,and the δEu range is relatively large,ranging from 0.95 to 4.83,that indicates that the deposit of the source rocks formed in a transitional environment from reduction to oxidation.The content of trace elements indicates that the Agulugou Formation deposited in a back-plateform basin with a water depth of less than 250 m,and the sedimentary facies were fluvial-shore sands,shallow water carbonaceous-argillaceous deposits of the barrier island.Combined with the above research,it shows that the Mesoproterozoic source rocks in the study area are mainly good-excellent source rocks formed in the reduction-oxidation environment,and the hydrocarbon generation geological conditions are favorable.

关 键 词：书记沟 中元古界 烃源岩 地质特征 地球化学 

分 类 号：P618.13[天文地球—矿床学]