摘要
为了探讨上扬子北缘米仓山-汉南隆起区下寒武统牛蹄塘组页岩形成环境及其与有机质富集的关系,利用大量野外露头页岩样品,进行微量元素、稀土元素、氩离子抛光-场发射扫描电镜、w(总有机碳)等测试分析.牛蹄塘组稀土元素北美页岩标准化配式比较平坦,轻重稀土元素分异程度较小,且稀土元素总量相对较低;亲氧Sr元素强烈亏损,V、U、Mo等元素共同富集;草莓状黄铁矿粒径较窄且集中分布在2.0?6.0μm;w(U)/w(Th)、w(Ni)/w(Co)、w(V)/w(Cr)偏低,多指示次氧-氧化条件,米仓山-汉南隆起区牛蹄塘组页岩在以深水缺氧沉积环境为主,伴随后期短暂次氧-氧化环境中形成保存.牛蹄塘组页岩中U、V、Mo等指示还原条件的元素以及指示海洋古生产力或有机质通量的w(Ba)、w(Ni)、w(Cu)均与w(总有机碳)呈一定正相关性,揭示深水还原条件以及较高的藻类、微生物等古海洋生产力是牛蹄塘组页岩有机质形成、保存、富集的主控因素.
Based on the shale samples from Niutitang Fonnation in Micangshan-Hannan Uplift,some experiment technical means such as trace elements,rare earth element(REE),argon ion figuring-field emission scanning electron microscope(Ar-FESEM)and total organic carbon(TOC)were carried out to detect and study the paleo-redox conditions of the shale in Niutitang Formation and its effects on organic matter enrichment.The test results showed that the amount of REE in the Niutitang shale was lower than that in North American shale,and North American shale-normalized rare-earth element patterns were flat,meaning the fractionation between light rare earth element and heavy rare earth element was poor.The oxyphilic element Sr was depleted while the V,U and Mo were apparently enriched in the shale of Niutitang Formation.The framboidal pyrite was commonly found in the organic matter by the Ar-FESEM method and the particle size mainly ranged from 2-6μm.Most values of w(U)Av(Th),w(Ni)/w(Co)and w(V)/w(Cr)were very low and indicated a sub-oxidized or oxidized condition of Niutitang Formation.The results above showed that the Niutitang shale in the Micangshan-Hannan Uplift was formed and developed in the main anoxic and reducing condition accompanying a transitory sub-oxidized or oxidized condition at once.U,V,Mo and w(Ba),w(Ni),w(Cu),which signified the condition of reduction and paleo-oceanic productivity/organic carbon flux had a positive correlation with w(TOC),indicating that the conditions of reduction and high paleo-oceanic productivity from algae and microorganism were the main controlling factors for organic matter forming,saving and enrichment in Niutitang Formation.
作者
田涛
付德亮
周世新
杨甫
李靖
Tian Tao;Fu De-liang;Zhou Shi-xin;Yang Fu;Li Jing(Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Natural Resources,Xi'an 710021,China;Lanzhou Center for Oil and Gas Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Lanzhou 730000,China)
出处
《兰州大学学报（自然科学版）》
CAS
CSCD
北大核心
2020年第1期37-47,55,共12页
Journal of Lanzhou University(Natural Sciences)
基金
陕西省重点研发计划资助项目(2017GY-150)
自然资源部煤炭资源勘查与综合利用重点实验室自主课题(ZP2019-2)。
