摘要
是否发育有效烃源岩是鄂尔多斯地区中元古界成藏的关键。综合利用野外地质考察、显微薄片鉴定和地球化学分析等研究方法对固阳县北中元古界渣尔泰山群阿古鲁沟组烃源岩地质特征开展研究。研究表明,中元古界烃源岩岩性为低级区域变质作用形成的炭质板岩及片岩,其矿物成分以石英为主,其次为斜长石、钾长石及白云母,还有少量菱铁矿。烃源岩有机碳含量高,变化在0.17%~21.62%之间,平均值为5.53%;有机质类型以Ⅰ型为主,其次为Ⅱ型;Ro变化范围为4.32%~5.09%,Tmax值介于556℃~564℃,处于过成熟阶段。稀土元素体现出LREE富集和轻、重稀土分异明显的特点,δEu介于0.43~0.49之间,表现出Eu的明显负异常;微量元素含量及比值指示阿古鲁沟组烃源岩形成时的沉积环境为水体深度大、水动力条件弱的并且与外海沟通受到限制的贫氧—缺氧的闭塞环境,沉积相类型为温暖潮湿气候条件下淡化泻湖相。
The development of effective source rocks is the key to Mesoproterozoic hydrocarbon accumulation in Ordos area.In this paper,the geological characteristics of source rocks in the Agulugou Formation of the Zhaertaishan Group of Mesoproterozoic Changchengian System in north of Guyang County were studied by means of field geological investigation,microscopic section identification and geochemical analysis.Researches show that the source rock is carbonaceous slate and a small amount of schist with quartz as the main mineral composition,followed by plagioclase,potassium feldspar and muscovite,and a small amount of siderite.The contents of organic carbon in the source rocks are high,and the value ranges from 0.17%to 21.62%,with an average of 5.53%.The type of organic matter isⅠkerogen,and the second isⅡkerogen.The value of Ro ranges from 4.32%to 5.09%,and the Tmax value is from 556℃to 564℃.These results show that the thermal evolution of source rocks is high,and is in the over-mature stage.Their NASC normalized REE patterns of the source rocks are characterized by LREE enrichment with obvious different value between LREE and HREE with distinctive negative Eu anomalies(δEu:0.43~0.49).The content and ratio of trace elements indicate that the sedimentary environment of the source rocks of Agulugou Formation is an oxygen-deficient-anoxic closed environment with large water depth,weak hydrodynamic conditions and limited communication with the open sea and the sedimentary facies are desalinated lagoon facies in warm and humid climate.
作者
冯娟萍
欧阳征健
范萌萌
Feng Juanping;Ouyang Zhengjian;Fan Mengmeng(College of Geology and Environment,Xi'an University of Science and Technology,Xi'an 710054;Geological Research Iinstitute for Coal Green Mining,Xi'an 710054;Bailie School of Petroleum Engineering,Lanzhou City University,Lanzhou 730070)
出处
《地质科学》
CAS
CSCD
北大核心
2020年第4期1044-1055,共12页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金青年项目(编号:41502107)资助。
关键词
固阳县北
中元古界
烃源岩
地质特征
地球化学
North of Guyang County
Mesoproterozoic
Source rocks
Geological characteristics
Geochemistry
