内蒙古西乌旗格尔楚鲁晚三叠世流纹岩年代学、地球化学特征及其地质意义  

Geochronology,Geochemistry and Geological Significance of Late Triassic Rhyolites in Geerchulu,Xi Ujimqin Qi,Inner Mongolia

作　　者：李红英[1] 周志广[1] 张达[1] 李鹏举[2] 柳长峰[1] 陈利贞 陈诚[1] 谷丛楠[4] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]四川理工学院,四川自贡643000 [3]河北省区域地质矿产调查研究所,河北廊坊065000 [4]天津华北地质勘查局,天津300170

出　　处：《矿物岩石地球化学通报》2015年第3期546-555,共10页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局地质调查项目(1212011120700;1212011085490;1212011220465;12120114093901)

摘　　要：为确定西乌旗格尔楚鲁地区的一套浅色流纹岩的形成时代及其成岩构造环境,进而为探讨古亚洲洋闭合时间提供新的证据,本文对其开展了锆石U-Pb年代学、岩石学和地球化学研究。结果表明,流纹岩形成于221±1Ma;岩石富硅碱、贫钙镁、高Ga/Al值,A/CNK>1;轻、重稀土元素分馏不明显,具有显著的Eu负异常;强烈亏损Sr、P、Ti,富集Zr,具有A2型花岗岩的特征,其成因可能是造山后伸展环境下幔源岩浆的底侵和地壳减薄,暗示研究区在三叠纪已经处于伸展背景,古亚洲洋在三叠纪之前已经闭合。研究区三叠纪伸展背景之下的岩浆活动始于早三叠世并一直持续到晚三叠世。To determine the formation time and tectonic setting of rhyolites outcropped in Geerchulu, Xi Ujimqin Qi, chronology, petrology and geochemistry studies were conducted in this paper, aiming at providing new evidence to constrain the closure time of Paleo-Asian Ocean. Zircons U-Pb dating yielded an age of 221±1 Ma. The rhyolites are featured by abundance in silica and alkalis and lacking of calcium and magnesium, with high Ga/Al ratio, A/CNK〉1. The samples showed no obvious fractionation between LREE and HREE, remarkable Eu negative anomalies, depletion of Sr, P and Ti, enrichment of Zr and A2-type granite affinity. These features revealed that the rhylites were generated by the underplating of mantle-derived magmas and the consequent partial melting of the lower crust under an extensional tectonic setting, suggesting the study region was under post-orogenic extensional setting in the Triassic and the Paleo-Asian Ocean had closed before Triassic. Triassic magma activity started from the Early Triassic and lasted till the Late Triassic.

关 键 词：流纹岩 三叠纪 A型火山岩 年代学 地球化学 西乌旗 

分 类 号：P588.141[天文地球—岩石学] P597.3[天文地球—地质学]