地质学报2017，Vol.91Issue(3)：523-541,19.
青海南山当家寺花岗岩体锆石U-Pb年代学、地球化学及其地质意义
LA-ICP-MS Zircon U-Pb Dating and Geochemistry of the Dangjiasi Granitic Complex in the Qinghai Nanshan Tectonic Zone, and Its Geological Implications
摘要
Abstract
An NW-SE trending Indosinian granitoide belt occurs within the Qinghai Nanshan tectonic zone,and the study of this granite zone has great scientific significance for investigating the transitional relation between the West Qinling and the Qilian orogenic belts in Paleozoic Tethys evolution stage.The Dangjiasi granitic complex consists dominantly of granodiorite pluton and monzogranite pluton.In this paper,a detailed study for the LA-ICP-MS zircon U-Pb dating,petrology and geochemistry characteristics was carried out for the Dangjiasi granitic complex.The results show that the crystallization ages of the Dangjiasi granodiorite and monzogranite are 240.1 ± 2.1 Ma and 241.0 ± 2.6 Ma,respectively,belonging to the Middle Triassic.The whole rock geochemical data show that the Dangjiasi granitic complex is relatively rich in SiO2 (66.37％～73.99％) and K2O (3.37％～4.73％),suggesting that the granitic rocks are metaluminous to weak peraluminous high-K calc-alkaline I-type granite.The rocks are enriched in LREE and depleted in HREE.The REE patterns show rightward incline and moderate negative Eu anomaly (δEu=0.32～0.64).The trace element geochemistry is evidently characterized by positive anomaly of LILE(e.g.Cs,Rb,K)and negative anomaly of HFSE(e.g.Nb,Ta,P,Ti).The Dangjiasi grantic complex originated mainly from the partial melting of lower crustal basic rocks,with minor mantle-derived component.In combination with analyses of regional geological setting,we suggest that the Dangjiasi granitic complex was formed in the stage of the southward subduction of the Zongwulong Oceanic crust.关键词
青海南山/西秦岭北缘/当家寺花岗岩体/锆石U-Pb定年/地球化学/构造环境Key words
Qinghai Nanshan/northern margin of West Qinling/Dangjiasi granitic complex/LA-ICP-MS zircon U-Pb dating/geochemistry/tectonic setting引用本文复制引用
张永明,林广春,裴先治,李佐臣,李瑞保,刘成军,裴磊,陈有炘,陈国超,王盟..青海南山当家寺花岗岩体锆石U-Pb年代学、地球化学及其地质意义[J].地质学报,2017,91(3):523-541,19.基金项目
本文为国家自然科学基金项目(编号41472191、40572121、41172186、40972136)、国家自然科学青年基金项目(编号41502191)、中央高校基本科研业务费专项资金项目(编号CHD2011TD020、2013G1271091、2013G1271092、310827161002、30827161006)和中国地质调查局地质调查项目(青海共和曲什那地区,编号12120114041201)资助的成果. （编号41472191、40572121、41172186、40972136）
