地质学报2017，Vol.91Issue(5)：1022-1038,17.
北阿尔金白尖山地区花岗闪长岩锆石U-Pb定年、Hf同位素组成及其地质意义
Zircon U-Pb Dating and Hf Isotopic Compositions of the Baijianshan Granodiorite in North Altyn Tagh and Its Geological Significance
摘要
Abstract
The Baijianshan granodiorite,located in the eastern segment of the Hongliugou-Lapeiquan ophiolite belt in North Altyn Tagh,occurs as large stocks intruding into the Lapeiquan Group.The whole-rock geochemical analysis shows that the granodiorite is low in SiO2 (62.58％～65.05％),high in CaO(4.02％～4.98％),characterized with (A/CNK)＜1.0(0.89～0.98),enriched in K,Rb and Ba,depleted in Nb,Ta,Zr and Ti,suggesting it belongs to weakly peraluminous calc-alkaline series and be characteristic of I-type granite.The total REE content of the Baijianshan granodiorite varies from 90.2 to 137.8 ug/g.The chondrite-normalized REE distribution patterns show relative enrichment of LREE with weakly negative Eu anomaly (δEuN =0.84～0.92).There is a large range of εHf (t) from-2.96 to 7.99,which is interpreted to be influenced by magmatic contamination.The geological characteristics and the experimental petrology data jointly show that the granodiorite was formed by partial melting of lower crust rocks and contaminated by the upper crust materals.Zircon LA-ICP-MS dating of granodiorite yields a UPb age of 475.2±2.0 Ma for zircons characterized by oscillatory zoning and Th/U＞0.3,and hence this age can be regarded as the formation age of the granodiorite.Combined with regional geological background,the Baijianshan granodiorite should be an eastern component of early Paleozoic magamatic activity in the Hongliugou-Lapeiquan ophiolite belt,which,together with the Qiashikansayi granodiorite and the Bashikaogong quartz-diorite (from the western Hongliugou area) forms a common island-arc magmatic rock belt.The early Paleozoic subduction-type granitoids,distributed in both northern and southern sides of EW-trending Hongliugou-Lapeiquan ophiolite belt,also shows that the whole North Altyn ocean is characterized by bidirectional subduction.关键词
红柳沟-拉配泉蛇绿混杂岩带/花岗闪长岩/锆石U-Pb定年与Hf同位素/岛弧/下地壳部分熔融/新疆Key words
Hongliugou-Lapeiquan ophiolite belt/granodiorite/LA-ICP-MS U-Pb zircon dating and Hf isotopes/island arc/part-melting of the lower crust/Altyn Tagh/Xinjiang引用本文复制引用
刘锦宏,刘良,盖永升,康磊,杨文强,廖小莹,杨敏..北阿尔金白尖山地区花岗闪长岩锆石U-Pb定年、Hf同位素组成及其地质意义[J].地质学报,2017,91(5):1022-1038,17.基金项目
本文为国家重点基础研究发展计划项目(编号2015CB856103)、国家自然科学基金项目(编号41430209、41421002)、教育部创新团队(编号IRT1281)和西北大学大陆动力学国家重点实验室自主研究重点课题联合资助成果. （编号2015CB856103）
