地质科学2018，Vol.53Issue(2)：615-637,23.DOI:10.12017/dzkx.2018.034
北秦岭烟镇岩体的锆石U-Pb定年、地球化学特征及构造背景
Zircon U-Pb dating and geochemical features of Yanzhen granitic body in northern Qinling Mountains, and its tectonic implications
摘要
Abstract
Yanzhen granitic body is one of Yanshanian acid intrusions in northern Qinling Mountains.It is significant to find new constrains on regional tectonic evolution based on petrogenesis and deep process of Yanzhen granitic body.The LA-ICP-MS dating sample YZ04 is biotite monzonitic granite,and the results of 23 zircon spots in total 30 spots are concordia with 207pb/235U-206Pb/238U trendline.The U-Pb age of 23 spots are clustered in 2 421 Ma,1 821 Ma,1 063 Ma,942.6 Ma,817.6 Ma,～ 145.0 Ma and～ 131 Ma.Zircon age spectrum of Yanzhen granitic body from Proterozoic to Early Cretaceous has formed,which recorded the corresponding regional magmatic events.The weighted average 206pb/238U age of 14 zircon spots from 129.7±1.1 Ma to 133.9±1.5 Ma is 131.3±0.6 Ma (MSWD =0.99),and it is the formation age of Yanzhen granitic body.Yanzhen granitic body is characterized by higher SiO2 and alkali,and lower MgO and CaO.Compositional spots of Yanzhen granitic body fall into high-K calcalkaline series in the SiO2-K2O diagram.Samples from Yanzhen granitic body are enriched in large ion lithophile elements and depleted in high field-strength elements,which has formed troughs of Nb,Ta,P and Ti in spider diagram.In chondrite-normalized REE distribution pattern diagram,Yanzhen granitic body samples have shown the characteristics of LREE enrichment and HREE depletion without obvious Eu negtive anomaly,whose (La/Yb)N ratios are from 7.97 to 49.19.The spots trend of Yanzhen granitic body in LaN-(La/Yb)N diagram has suggested that their compositional change is controlled mainly by source compositon and degree of partial melting.Samples of Yanzhen granitic body are higher Sr content and lower Y content,which has suggested that it belongs to adakite.Yanzhen granitic body originated from partial melting of the thickened lower crust,and its residual phases of partial melting source included garnet,rutile,and no plagioclase.Yanzhen granitic body is product of lithosphere delamination occurred in ～ 131 Ma,and it is deep process of forming Yanzhen zircon age spectrum.It suggests that lithosphere thinning of north China craton in Yanshanian has affects northern Qinling Mountains.关键词
烟镇岩体/锆石定年/年龄谱/埃达克岩/岩浆(流体)混合/岩石圈拆沉/北秦岭Key words
Yanzhen granitic body/Zircon dating/Age spectrum/Adakite/Magma (fluids) mixing/Lithosphere delamination/Northern Qinling Mountains分类
天文与地球科学引用本文复制引用
梁涛,卢仁..北秦岭烟镇岩体的锆石U-Pb定年、地球化学特征及构造背景[J].地质科学,2018,53(2):615-637,23.基金项目
国家自然科学基金项目(编号:U1504405)、河南省科技计划项目(编号:162300410065)和河南省国土资源厅科技攻关项目(编号:2014-06,2016-08)资助. （编号:U1504405）
