广西钦州石夹晚泥盆~早石炭世硅质岩地球化学特征及沉积环境意义  

Geochemical characteristics and sedimentary environment of the Late Devonian-Early Carboniferous siliceous rocks in Shijia,Qinzhou,Guangxi

作　　者：袁琼 周旻玥 韦龙明[1] 田晗钰 白志强[3] YUAN Qiong;ZHOU Minyue;WEI Longming;TIAN Hanyu;BAI Zhiqiang(Guangxi Key Laboratory of Concealed Metal Mineral Exploration,School of Earth Sciences,Guilin University of Technology,Guilin 541006,Guangxi,China;Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Shenzhen Graduate School,Peking University,Shenzhen 518055,Guangdong,China)

机构地区：[1]桂林理工大学、广西隐伏金属矿产勘查重点实验室,地球科学学院,广西桂林541006 [2]中国科学院地质与地球物理研究所中国科学院页岩气与地质工程重点实验室,北京100029 [3]北京大学、深圳研究生院,广东深圳518055

出　　处：《矿产与地质》2018年第5期852-860,共9页Mineral Resources and Geology

基　　金：广西隐伏金属矿产勘查重点实验室开放研究课题(编号:11-031-20-K1);中国地质调查项目(编号:1212011085148)共同资助

摘　　要：通过岩石学及元素地球化学分析方法进行沉积环境恢复。研究表明:广西钦州石夹剖面晚泥盆世～早石炭世硅质岩主要组成矿物为隐晶-微晶质石英颗粒与球状、纤维状玉髓,可见大量放射虫化石,表明硅质岩在强烈的生物作用下形成;SiO_2、Al_2O_3和TiO_2平均含量较高,Fe_2O_3平均含量较低,表明硅质岩含有高的陆源泥质沉积物;Si/(Si+Al+Fe)为0.83～0.97,Al/(Al+Fe+Mn)为0.33～0.82,平均为0.65,Al_2O_3/(Al_2O_3+Fe_2O_3)为0.39～0.87,平均为0.71,表明硅质岩主要为碎屑生物成因。通过主量元素成分投影图解,表明硅质岩沉积环境主要为大陆边缘;多数样品的U/Th比值均小于1,平均为0.84,总体表现出非热水沉积硅质岩的地球化学特征,处于大陆岛弧与大陆边缘过渡区,但在D-C地质界线处遭受过海底热液活动的影响,并经历了先强后弱的变化过程。界线处的灰黑色页岩,是Hangenberg事件及其D-C生物灭绝事件在深水相的石夹水库剖面上的具体表现,推测残留海槽拉张导致的海底火山热液活动是事件发生的影响因素之一。The petrology and elemental geochemical analysis of the siliceous rocks in the Shijia section of Qinzhou,Guangxi,have been used to understand the depositional environment of the area.The study showed that the main mineral composition of the Late Devonian-Early Carboniferous siliceous rocks in the Shijia section are cryptocrystalline-microcrystalline quartz grains,globular and fibrous chalcedony,and a large amount of radioactive fossils are visible.Under biological action,indicating that the siliceous rocks were formed under strong biological action;the average content of SiO 2,Al 2 O 3 and TiO 2 is higher and the average content of Fe 2 O 3 is lower,indicating that siliceous rocks contain high terrigenous muddy sediments;Si/(Si+Al+Fe)is 0.83-0.97,Al/(Al+Fe+Mn)is 0.33-0.82,the average is 0.65,and Al 2 O 3/(Al 2 O 3+Fe 2 O 3)is 0.39-0.87,the average is 0.71,indicating that the siliceous rocks are mainly of detrital biological origin.The graphical analysis of the major elemental elemental projection shows that the siliceous sedimentary environment is mainly continental marginal,and the DC boundary line may be affected by the seabed hydrothermal activity;the U/Th ratio of the sample is less than 1(except for the sample-49-4,6,7,and 9),the average is 0.84,shows the geochemical characteristics of non-hydrothermally deposited siliceous rocks,and the formation environment of siliceous rocks at the geological boundary belongs to the transitional zone between the continental island arc and the continental margin and receives hydrothermal fluids.At the Geological boundary of Devonian-Carboniferous,the degree of influence experienced a change process from strong to weak.The gray black shale developing on the bottom of Late Devonian-Early Carboniferous basin in South China is the pecific performance of Hangenberg event in the deep water facies of Shijia Reservoir.It indicates that seabed volcanic hydrothermal activity is one of the causes of this event.

关 键 词：硅质岩 晚泥盆世~早石炭世 地球化学 沉积环境 钦州 广西 

分 类 号：P588.244[天文地球—岩石学] P595[天文地球—地质学]