摘要
分析了上石炭统小独山阶—下二叠统紫松阶阿木山组玄武岩地球化学特征,对玄武岩类型、岩石特征、构造环境等进行了探讨,结合前人的研究成果,阐述了石炭纪—二叠纪盆地的基本性质。Zr/TiO2-Nb/Y、SiO2-TFeO/MgO和Zr-Y-Nb图解显示,玄武岩类型主要为亚碱性的拉斑玄武岩;稀土元素球粒陨石配分模式为右倾曲线,(La/Yb)N值较高,轻重稀土元素分馏较强,(Gd/Lu)N值相对较低,重稀土元素分馏较弱,δEu在0.87～1.11之间,无明显Eu异常;N-MORB标准化的微量元素蛛网图显示,K2O、Rb、Ba、Th等不相容元素富集,Hf、Nb、Y等亏损。Zr-Zr/Y和Ta/Hf-Th/Hf构造环境图解表明,该玄武岩产于陆内裂谷,指示晚石炭世—早二叠世额济纳旗及其邻区已进入了陆内演化阶段,为拉张作用下的陆内裂谷(裂陷)盆地。
Based on an analysis of basalt geochemical characteristics of Amushan Formation（western Ganquan Formation） of Upper Carboniferous Xiaodushan Stage-Lower Permian Zisong Stage and the basalt type,this paper deals with the rock characteristics and tectonic environment.Previous studies have already revealed the basic type of Carboniferous-Permian basin.The Zr/TiO2-Nb/Y,SiO2-TFeO/MgO and Zr-Y-Nb diagrams show that the basalt in Ejin Banner and its vicinities is mainly of the sub-alkaline tholeiite series.Chondrite-normalized REE patterns are right-oblique curves;the relatively high（La/Yb）N and low（Gd/Lu）N indicate that light rare earth elements have experienced obvious fractionation,but heavy rare earth elements have been only subjected to week fractionation,and δEu=0.87~1.11,without remarkable Eu depletion;N-MORB-normalized spider diagram shows relatively high abundances of K2O,Rb,Ba,Th and low abundances of Hf,Nb,Y.Through an analysis of Zr-Zr/Y and Ta/Hf-Th/Hf diagrams,it is considered that the basalt in the study area should be of the sub-alkaline tholeiite series occurring in the rift valley,and Ejin Banner and its vicinities entered into an intracontinental evolution period,being a rift basin by tension.
出处
《地质通报》
CAS
CSCD
北大核心
2011年第6期932-942,共11页
Geological Bulletin of China
基金
中国地质调查局国土资源大调查项目《西北地区中小盆地群油气资源远景调查》(编号:1212010733506)
