摘要
对南秦岭封子山岩体进行了锆石U-Pb年代学、岩石地球化学以及Hf同位素的研究,以确定其形成时代、岩体成因及形成时的构造环境.LA-ICP-MS锆石U-Pb定年测试结果表明,该岩体形成于新元古代晚期(716～710Ma).锆石Hf同位素分析显示ε_(Hf)(t)为-3.16～1.17,二阶段模式年龄(TDM2)为1.84～1.52Ga.地球化学特征显示封子山岩体具高硅(62.92%～73.57%)、高钠(3.33%～4.22%),富集轻稀土元素,富集K、Rb、Ba、Th、U等大离子亲石元素,亏损Nb、Ta、Ti、P等高场强元素的特征,Eu显示弱负异常(δEu=0.79～0.95),为准铝质-弱过铝质中钾钙碱性I型花岗岩.结果表明,封子山岩体主要来源于陡岭群片麻岩的部分熔融.封子山岩体形成于裂谷扩张与小洋盆间杂并存的构造环境,是洋壳向陆壳俯冲作用的产物,可能是Rodinia超大陆聚合与裂解事件在该地区作用的响应.
This study presents zircon U-Pb dating,geochemistry and zircon Lu-Hf isotopic data for the Fengzishan granitic intrusion located in South Qinling to constrain its formation age,petrogenesis and tectonic setting.LA-ICP-MS zircon U-Pb dating results suggest that the Fengzishan granitic intrusion was formed in Late Neoproterozoic(716-710 Ma).Zircon Hf isotopic data show theεHf(t)values of-3.16-1.17 and TDM2 values of 1.84-1.52 Ga.Geochemical characteristics show that they are high in silica(62.92%-73.57%)and Na(3.33%-4.22%)contents and relatively enriched in light rare earth elements(LREE)and large ion lithophile elements(LILE)(e.g.K,Rb,Ba,Th,U),poor in high field strength elements(HFSE)(Nb,Ta,Ti,P)and slightly negative Eu anomalies(δEu=0.79-0.95),displaying metaluminous to weak peraluminous and medium potassium calc-alkaline I-type granites.These characteristics suggest that the magma was primarily derived from partial melting of gneiss of the Douling Group.The Fengzishan granitic intrusion was produced by subduction of oceanic crust into continental crust and was formed in the tectonic setting of rift expansion coexisting with small ocean basin.The formation of the Fengzishan granitoid was probably the response to the amalgamation and separation of the global Rodinia supercontinent.
作者
柏治安
时毓
刘希军
黄倩雯
覃康乐
Bai Zhi’an;Shi Yu;Liu Xijun;Huang Qianwen;Qin Kangle(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,China;Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi,Guilin 541004,China;State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210093,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2019年第4期1186-1209,共24页
Earth Science
基金
国家自然科学基金项目(Nos.41562005
41302155)
广西自然科学基金项目(Nos.2016GXNSFAA380001
2017GXNSFBA198167)
广西"八桂学者"团队项目(2013
有色金属成矿理论与勘查技术)
内生金属矿床成矿机制研究国家重点实验室(南京大学)开放基金项目(No.21-16-04)
