淮南二叠纪含煤地层泥质岩地球化学特征及其地质意义  

Geochemical characteristics of argillaceous rocks in Permian coal-bearing strata in Huainan and their geological implications

作　　者：范翔[1] 刘桂建[1] 孙若愚[1] 孙梅[1] 

机构地区：[1]中国科学技术大学地球与空间科学学院中国科学院壳幔物质与环境重点实验室,安徽合肥230026

出　　处：《地学前缘》2015年第4期299-311,共13页Earth Science Frontiers

基　　金：国家自然科学基金项目(41173023;41373110)

摘　　要：淮南煤田地处华北板块东南缘,可能记录了华北和华南板块碰撞过程的重要信息。本文对所采淮南二叠纪煤系地层泥质岩进行了主量元素、微量元素(包括稀土元素)测试和矿物成分分析,并据此讨论了泥质岩的物源区岩石风化程度、母岩性质以及板块的构造特征,为理解华北板块南缘的构造演化提供了地球化学方面的证据。地球化学参数图解lg(SiO2/Al2O3)-lg(Fe2O3-K2O)、La/Sc-Th/Co、Fe2O3-K2O-Al2O和Al2O3-K2O以及XRD分析表明,淮南泥质岩样品中矿物主要是石英和由长石风化的以高岭石、绿泥石等为主的黏土矿物;主量元素(Al2O3/TiO2、K2O/Al2O3和碎屑沉积岩母岩判别函数图)、微量元素(La/Sc、Th/Sc、Cr/Th、V-Ni-La×4三角图和Ni-Cr图)和稀土元素(Eu/Eu*、(La/Yb)N和Eu/Eu*-(Gd/Yb)N图)地球化学参数表明,淮南泥质岩的母岩主要是后太古宙长英质火成岩;极高的CIA、CIW和PIA值以及Al2O3-CaO*+Na2O-K2O-CIA、Al2O3-CaO*-Na2O-CIW图解指示了淮南泥质岩的母岩经历了剧烈的风化作用。根据样品的K2O/Na2O-SiO2图、Th-La-Sc和Sc-Th-Zr/10三角图解,本研究认为淮南煤田二叠纪时期先后经历了活动大陆边缘和被动大陆边缘的以及可能的大陆岛弧的板块构造环境,指示了华北和华南板块在早二叠世可能已经发生了碰撞。Huainan Coalfield located at southeastern margin of North China Block may provide important information on the convergent movement between North China Block and South China Block. The Permian argillaceous rocks from coal-bearing strata in Huainan Coalfield were analyzed for major elements, minor elements （including rare earth elements） and minerals. The source area weathering, provenance and depositional tectonic setting are discussed. According to plots of lg（SiO2/Al2O3 ）-lg（Fe2 O3-K2 O）, La/Sc-Th/ Co, Al2O3-K2O and Fe2O3-K2O-Al2O3, as well as XRD analysis, the mineralogical assemblages in argillaceous rocks are dominated by quartz and residual clays such as kaolinite. Palaeoweathering indices （CIA, CIW and PIA ratios） and Al2O3-CaO＊ ＋Na2 O-K2O-CIA and Al2O3-CaO-Na2O-CIW diagrams suggest that the source rocks were subjected to an intensive weathering. Argillaceous rocks were predominantly derived from post-Archean felsic igneous rocks based on the values of Al2O3/TiO2, K2O/Al2O3, La/Sc, Th/Sc, Cr/Th, Eu/Eu＊ and （La/Yb）N and plots of Ni-Cr, Eu/Eu＊ -（Gd/Yb）N, V-Ni-La× 4, and the discriminant function diagram. Successive active and passive continental margins are the main tectonic settings for Huainan Coalfield, with a possible continental island arc setting, as identified by K2O/Na2O-SiO2, Th-La-Sc and Sc- Th-Zr/10 diagrams, implying the collision of North China Block and South China Block possibly happened during the Early Permian.

关 键 词：泥质岩 地球化学 物源分析 淮南煤田 华北板块 

分 类 号：P534.46[天文地球—古生物学与地层学]