张家界地区志留系岩石地球化学与构造背景  

Geochemical characteristics and tectonic setting of Silurian rocks in Zhangjiajie area

作　　者：梁恩云 刘耀荣 邹光均 魏方辉 刘庚寅 熊苗 

机构地区：[1]湖南省地质调查院,长沙410116

出　　处：《中国地质调查》2017年第6期58-65,共8页Geological Survey of China

基　　金：中国地质调查局"湖南1:5万尹家溪;溪口;三岔村幅区域地质调查(编号:12120114066201)";"扬子工程湘西-鄂西成矿带神农架-花垣地区地质矿产调查(编号:DD20160029)"项目联合资助

摘　　要：张家界地区志留系出露有兰多弗里统及文洛克统,其中兰多弗里统泥岩中SiO_2含量平均61.59%,SiO_2/Al_2O_3值平均3.63,K_2O/Na_2O值平均4.80,Al_2O_3/(K_2O+Na_2O)值平均3.49,∑REE含量平均238.58×10^(-6),LREE含量平均213.89×10^(-6),LREE/HREE值平均8.68,B含量平均98.29×10^(-6),B/Ga值平均3.99,Th/U值平均5.61。通过构造环境判别图解认为:兰多弗里统泥岩以活动大陆边缘物源为主,混入部分大陆岛弧物源,其古老物源则可能来自被动大陆边缘;已经拼合在一起的华夏、扬子陆块,在志留纪时期继续向北西挤压,形成多处隆升(黔中隆起、雪峰隆起等),随着进一步挤压,雪峰隆起升出海面,为张家界地区提供了泥质沉积物,挤压导致岛弧形成并提供了部分物源。Silurian outcrops include Llandovery Series and Wenlock Series in Zhangjiajie area. In the mudstones of Llandovery Series,the contents of different compositions are as follows: the average content of SiO_2 is 61. 59%,the average value of SiO_2/Al_2O_3 is 3. 63,K_2O/Na_2O is 4. 80,Al_2O_3/( K_2O + Na_2O) is 3. 49,the average content of ∑REE is 238. 58 × 10^(-6),the average content of LREE is 213. 89 × 10^(-6),the average value of LREE/HREE is 8. 68,the average content of B is 98. 29 × 10^(-6),the average value of B/Ga is 3. 99 and the average value of Th/U is 5. 61. According to the tectonic setting discrimination diagrams,the authors declared that the mudstones source of Llandovery Series is active continental margin,interfused with some continent island arc. And the older source could be passive continental margin. The authors concluded that after the combination of Cathaysia and Yangtze Plate,the new plate continued to extrude northwest and formed many uplifts( Qianzhong and Xuefeng uplifts). With further extrusion,Xuefeng uplift was raised above the sea level,which provided argillaceous sediment for Zhangjiajie area. The extrusion caused the formation of island arc and provided part source.

关 键 词：志留系 构造背景 岩石地球化学 地球化学特征 张家界 碎屑岩 被动大陆边缘 雪峰隆起 物源区 地层学杂志 前陆盆地 

分 类 号：P534.43[天文地球—古生物学与地层学]