摘要
西昆仑奥东布拉克地区阿羌岩组火山岩平均含量Si O2为49.49%,Ti O2为1.07%,Al2O3为14.96%,ALK均值为3.38%,Na2O/K2O均值为1.46,表明岩石属于钙碱性向碱性(偏碱性)系列过渡的岩石类型。稀土元素配分模式图显示岩石轻稀土元素(LREE)相对富集,重稀土元素(HREE)相对亏损,具有弱正Eu异常,指示岩浆没有经历明显的分异作用。微量元素显示,岩石富集Rb、Ba、K等大离子亲石元素,而相对亏损Ta、Nb、Hf等活动性弱的高场强元素,指示岩石形成于岛弧的构造环境。锆石U-Pb定年结果显示火山岩锆石206Pb/238U加权平均年龄为474.2±4.3 Ma,表明阿羌岩组火山岩形成于奥陶世而不是前人认为的石炭纪。
The study area Aodongbulake is situated in the West Kunlun Mountains.On average,the chemical composition of the Aqiang Formation volcanics is Si O249.49%,TiO21.07%,Al2O314.96% ALK 3.38%,Na2O/K2O4.3,which shows the rocks belong to calc-alkaline to alkaline series rock.Chondrite-normalized REE patterns shows that the content of LREE is ratively enriched to HREE with weak positive Eu abnormal,which suggests that the magama has not experienced differentiation obviously.Trace element composition patterns show that the rocks are enriched in large ion lithophile elements（LILE）（Rb、Ba、K）and depleted in high field strength elements（Nd、Ta、Hf）,displaying that the rocks formed in the island arc environment.Zircon U-Pb dating indicated that the206Pb/238 U weighted average age of zircon from volcanic is 474.2 ± 4.3 Ma,indicating that Aqiang Formation volcanics may be formed in the Ordovician instead of Carboniferous.
出处
《地质调查与研究》
2015年第1期10-17,共8页
Geological Survey and Research
基金
中国地质大调查项目:新疆西昆仑J44E021022
J44E022022等四幅区域地质调查项目(1212011220636)
关键词
西昆仑
火山岩
地球化学
锆石U-PB定年
West Kunlun
Aqiang Formation
volcanics
geochemistry
zircon U-Pb dating
