Geochronology, Geochemistry and Tectonic Setting of the Bairiqiete Granodiorite Intrusion （Rock Mass） from the Buqingshan Tectonic Mélange Belt in the Southern Margin of East Kunlun

• Published in: 地质学报：英文版 2014, Vol.88 (2), p.584-597
• Main Author: LI Zuochen PEI Xianzhi LI Ruibao PEI Lei LIU Chengjun CHEN Youxin LIU Zhanqing CHEN Guochao XU Tong YANG Jie WEI Bo
• Format: Article
• Language: English
• Subjects: 东昆仑; 元素地球化学特征; 地球化学分析; 岩体; 构造环境; 花岗闪长岩; 锆石U-Pb年代学; 青山
• ISSN: 1000-9515; 1755-6724

This study focuses on the zircon U-Pb geochronology and geochemistry of the Bairiqiete granodiorite intrusion （rock mass） from the Buqingshan tectonic mélange belt in the southern margin of East Kunlun.The results show that the zircons are characterized by internal oscillatory zoning and high Th/U （0.14-0.80）,indicative of an igneous origin.LA-ICP-MS U-Pb dating of zircons from the Bairiqiete granodiorite yielded an age of 439.0 ± 1.9 Ma （MSWD =0.34）,implying that the Bairiqiete granodiorite formed in the early Silurian.Geochemical analyses show that the rocks are medium-K calc-alkaline,relatively high in Al2O3 （14.57-18.34 wt％） and metaluminous to weakly peraluminous.Rare-earth elements have low concentrations （45.49-168.31 ppm） and incline rightward with weak negative to weak positive Eu anomalies （δEu =0.64-1.34）.Trace-element geochemistry is characterized by negative anomalies of Nb,Ta,Zr,Hf and Ti and positive anomalies of Rb,Th and Ba.Moreover,the rocks have similar geochemical features with adakites.The Bairiqiete granodiorite appears to have a continental crust source and formed in a subduction-related island-arc setting.The Bairiqiete granodiorite was formed due to partial melting of the lower crust and suggests subduction in the Buqingshan area of the Proto-Tethys Ocean.