摘要
北祁连奥陶系阴沟群硅质岩对该地区的沉积环境和构造背景具有重要的指示意义,目前多认为其形成于大陆边缘环境。北祁连西水地区奥陶系阴沟群中的硅质岩w(SiO_2)值、Si/Al值、Al/(Al+Fe+Mn)值、Fe/Ti值、(Fe+Mn)/Ti值、w(∑REE)值等地球化学特征均指示硅质岩为热水沉积成因;Al_2O_3/(Al_2O_3+Fe_2O_3)值、U/Th值、Ti/V值、(La/Ce)_N值、δCe值指示其形成于大陆边缘环境;w(Al_2O_3)值与w(MgO)值、U/Th值、Al_2O_3/TiO_2值均反映硅质岩在形成过程中受到了陆源碎屑的影响;Al_2O_3、TiO_2、Cr、Rb、Ba、Zr质量分数特征及稀土元素配分模式表明硅质岩的形成与岛弧以及弧后盆地有关。综合分析与奥陶系硅质岩伴生的火山岩岩石组合特征以及区域构造演化背景,认为西水地区奥陶系阴沟群硅质岩应属大陆边缘背景下,其弧后盆地靠近岛弧一侧的产物。这为进一步细化研究北祁连奥陶纪沟-弧-盆体系的空间格局提供了重要的沉积学依据。
The Ordovician cherts could indicate sedimentary environment and tectonic background in North Qilian Mountains.Many researchers have done much study on them,and suggest the cherts are formed in continental margin.This paper analyzes the characteristics of sedimentation and geochemistry of the Ordovician cherts collected in Xishui region,North Qilian Mountains.The results show that the value of SiO2,Si/Al,Al/（Al＋Fe＋Mn）,Fe/Ti,（Fe＋Mn）/Ti,and ∑REE indicate the characteristics of hydrothermal origin.The value of Al2O3/（Al2O3 ＋Fe2O3）,U/Th,Ti/V,（La/Ce）/N,and δCe suggests the cherts were formed in continental margin.The value of MgO,U/Th,and Al2O3/TiO2 show that the cherts suffered by terrigenous detrital.The value of Al2O3,TiO2,Cr,Rb,Ba,Zr and the REE pattern indicate that the cherts maybe formed in arc island and arc island basin.Considering the Ordovician volcanic association and tectonic evolution in North Qilian,we propose that the Ordovician cherts should be deposited in deepwater basin near the island arc,which belonged to a continental margin background.It offers important sedimentologic evidence for further studying the trench-arc-basin.
作者
计波
王国强
唐卓
朱涛
罗根根
Ji Bo;Wang Guoqiang;Tang Zhuo;Zhu Tao;Luo Gengen(Xi＇an Center of Geological Survey,Geological Survey of China,Xi＇an 710054,China;Orogen Research Center of China Geological Survey,Xi＇an 710054,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits of Ministry of Land and Resources,Xilan 710054,China)
出处
《地质科技情报》
CSCD
北大核心
2018年第5期21-29,共9页
Geological Science and Technology Information
基金
中国地质调查局地质调查项目"甘肃省肃南县西水乡1:5万三幅矿产地质调查"(DD20160012)
关键词
北祁连
阴沟群
硅质岩
地球化学
构造背景
North Qilian
Yingou Group
chert
geochemisty
tectonic background
