川西卡拉地区晚古生代硅质岩成因及沉积环境  

Petrogenesis and sedimentary environment of silicate in Late Paleozoic in Kala area of Western Sichuan Province

作　　者：刘大明[1,2] 姚虹佑 胡林[1] 余亮 刘仪中 LIU Daming;YAO Hongyou;HU Lin;YU Liang;LIU Yizhong(Northwest Sichuan Geological Team,Sichuan Geology and Mineral Bureau,Mianyang 621000,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]四川省地质矿产勘查开发局川西北地质队,绵阳621000 [2]成都理工大学地球科学学院,成都610059

出　　处：《中国地质调查》2020年第6期68-78,共11页Geological Survey of China

基　　金：国家自然科学基金“川西里伍岩群变质-热事件:年代学证据及构造意义(编号:41603034)”;中国地质调查局“川西稀有金属矿集区综合地质调查(编号:DD20160074)”项目联合资助。

摘　　要：为了研究川西卡拉地区晚古生代沉积环境特征,以该地区下石炭统邛依组和上二叠统卡翁沟组中广泛分布的硅质岩为研究对象,开展了岩石学、地球化学特征等研究。结果表明:研究区古生代硅质岩属纯硅质岩范畴,在沉积过程中有持续的陆源物质供给;Al/(Al+Fe+Mn)平均值0.62,结合Al-Fe-Mn三角图解,显示它们为生物成因硅质岩;Al2O3/(Al2O3+Fe2O3)、Th/U、Th/Sc、(La/Ce)N、(La/Yb)N等特征比值以及构造环境判别图,反映出硅质岩沉积环境为大陆边缘的浅海-斜坡;Ceanom值为-0.04~0.07,从石炭纪—二叠纪逐渐增大,指示水体为缺氧环境,且还原性逐渐增强。结合区域地质演化,认为甘孜理塘洋在石炭纪时期已经打开,并在二叠纪时期持续扩张,区内沉积盆地的海水逐渐变深。In order to study the sedimentary environment characteristics of the Late Paleozoic in Kala area of Western Sichuan Province,the authors have conducted the petrological and geochemical analyses of the widely distributed silicate in Qiongyi Formation of Lower Carboniferous and Kawenggou Formation of Upper Permian.The results show that the silicate in the study area belongs to the pure siliceous rocks,with a continuous supply of land-based materials during the deposition process.The average Al/(Al+Fe+Mn)ratio is 0.62,and the silicate shows a biogenic origin by the Al-Fe-Mn diagram.The ratios of Al 2O 3/(Al 2O 3+Fe 2O 3),Th/U,Th/Sc,(La/Ce)N and(La/Yb)N and tectonic environment discriminant diagram demonstrate that the silicate developed in a shallow-slope depesitional environment in the continental margin.The Ce anom value is-0.04 to 0.07,and it gradually increases from the Carboniferous to the Permian period,indicating the water body is in an anoxic environment with gradually increasing reducibility.The Garz--Litang basin opened in the Carboniferous period,in accordance with the regional geological evolution,and it continued to expand during the Permian period,with the gradually increasing depth of the seawater within the sedimentary basins.

关 键 词：川西卡拉 硅质岩 成因 沉积环境 

分 类 号：P588.244[天文地球—岩石学]