塔里木西北缘乌什南上石炭统索格当他乌组微量稀土元素特征及地质意义
Geological Significance and Characteristics of Rare Earth and Trace Elements from Upper Carboniferous Suogedangtawu Formation of the South of Wushi County in Northwestern Margin of Tarim Basin

摘要： 为探讨塔里木盆地西北缘柯坪地区上石炭统索格当他乌组沉积环境、物源属性和构造背景，在野外地质调查的基础上，对柯坪地区乌什南剖面上石炭统索格当他乌组细碎屑岩进行了系统的地球化学样品采集与测试分析。通过氧化还原敏感元素组合及微量元素特征比值对比，发现研究区索格当他乌组细碎屑岩形成于弱还原环境。再利用Hf-La/Th、La/Sc-Co/Th和REE-La/Yb判别图解、微量元素特征比值(La/Sc、Sc/Th、Cr/Th及Co/Th)，并结合岩石矿物薄片分析，认为索格当他乌组细碎屑岩与上地壳特征相似，母岩以长英质岩石为主，混有部分花岗岩和安山岩。对比不同构造背景下杂砂岩的稀土、微量元素特征，并结合碎屑岩La-Th-Sc、Th-Sc-Zr/10、Th-Co-Zr/10三角图解，认为研究区上石炭统索格当他乌组细碎屑岩源岩具有大陆岛弧、活动大陆边缘、被动大陆边缘多重构造背景。
Abstract: In order to discuss the sedimentary environment,provenance and tectonic settings of Upper Carboniferous Suogedangtawu Formation of Keping area in northwestern margin of Tarim Basin, on the basis of geological investigation, we selected 12 samples to test and analyze trace and rare earth elements. Redox-sensitive elements combination and trace element characteristic parameters reflect that the finegrained detrital rocks form in weak reduction environment. Using Hf-La/Th, La/Sc-Co/Th and REE-La/Yb diagram, trace element ratios(La/Sc, Sc/Th, Cr/Th and Co/Th), combined with microscopic identification, we regard that the sources of sediments are mainly from upper continental crust with felsic rocks. By the contrast of characteristics of REE, combined with La-Th-Sc,Th-Sc-Zr/10,Th-Co-Zr/10 diagram, a conclusion can be drawn that the tectonic settings of the study area are continental island arc, active continental margin and passive continental margin