青海同德县和日乡一带黑云母花岗闪长岩年龄、地球化学及其对西秦岭碰撞造山时限的制约  

Chronology and geochemistry of the granitoids in Heri Town,Tongde County,Qinghai Province,and its tectonic significance

作　　者：陈玉科 CHEN Yuke(Integrative Survey Party of Non-ferrous Metals Geological Exploration Bureau,Hohhot 010070,Inner Mongolia,China)

机构地区：[1]内蒙古自治区有色地质勘查局综合普查队,内蒙古呼和浩特010070

出　　处：《地质通报》2020年第7期1015-1024,共10页Geological Bulletin of China

基　　金：中国地质调查局项目《青海省同德县谷芒地区五幅1∶5万区域地质矿产调查》(编号:12120114018217)。

摘　　要：采用LA-ICP-MS锆石U-Pb同位素测年方法,在青海同德县和日乡一带黑云母花岗闪长岩中获得锆石U-Pb年龄为229.7±1.0 Ma。岩石地球化学特征表明,该花岗闪长岩属高钾钙碱性系列,具微弱的负Eu异常和右倾的稀土元素球粒陨石标准化配分特征,是下地壳部分熔融的产物。综合已有的研究成果,认为和日乡黑云母花岗闪长岩侵位时代为晚三叠世,属I型花岗岩类,形成于板块碰撞前的活动陆缘弧构造环境,其成因与阿尼玛卿-勉略洋的向北俯冲消减密切相关,为西秦岭印支期进入碰撞造山阶段提供了年龄上限约束。In this study,the author used LA-ICP-MS zircon U-Pb isotopic dating method and obtained weighted average zircon U-Pb age of 229.7±1.0 Ma from the biotite granodiorite in Heri Town,Tongde County,Qinghai Province.The geochemical characteristics show that it belongs to high-K calcium-alkali series,and resulted from partial melting of crustal components,with weak negative Eu anomalies and right-inclined chondrite-normalized REE patterns.Based on a comprehensive analysis of previous researched,the authors hold that the biotite granodiorite was formed in the Late Triassic,and belonged to I-type granite formed in the active continental margin environment before the plane collision.Its genesis was closely related to the northward subduction of the Ańyemagen-Mianlue Ocean.The results obtained by the authors provide a new age constraint for the entrance of West Qinling into the syn-collision stage in the Indosinian.

关 键 词：花岗闪长岩 锆石U-PB年龄 活动陆缘 西秦岭 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]