东秦岭东段五垛山花岗伟晶岩锆石U-Pb年代学和微量元素特征及地质意义  

Zircon U-Pb Geochronology and Trace Element Characteristics of Wuduoshan Granitic Pegmatite in Eastern Part of East Qinling and Its Geological Significance

作　　者：陈孝珍[1,2] 陈国超 李瑞保[2] 张亚峰 季宪军[1] 张晓飞 Chen Xiaozhen;Chen Guochao;Li Ruibao;Zhang Yafeng;Ji Xianjun;Zhang Xiaofei(School of Civil Engineering,Nanyang Institute of Technology,Nanyang 473000,China;Key Laboratory of Western China’s Mineral Resources and Geological Engineering,Ministry of Education,Chang’an University,Xi’an 710054,China;Key Laboratory of Metallogeny and Mineral Assessment,Ministry of Natural Resources,Beijing 100037,China;Shaanxi Center of Mineral Geological Survey,Xi’an 710068,China;Development Research Center,China Geological Survey,Beijing 100037,China)

机构地区：[1]南阳理工学院土木工程学院,河南南阳473000 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]自然资源部成矿作用与资源评价重点实验室,北京100037 [4]陕西省矿产地质调查中心,陕西西安710068 [5]中国地质调查局发展研究中心,北京100037

出　　处：《地球科学》2023年第10期3753-3769,共17页Earth Science

基　　金：国家自然科学基金项目(No.41502191);河南省重点研发与推广专项项目(No.212102310030);自然资源部成矿作用与资源评价重点实验室开放基金项目(No.ZS006);长安大学西部矿产资源与地质工程教育部重点实验室开发基金项目(No.300102261505);南阳理工学院交叉科学研究项目.

摘　　要：东秦岭东段五垛山大型花岗岩基中花岗伟晶岩丰富,关于它的形成时代、岩石成因和地球动力学背景仍不清楚.LAICP-MS锆石U-Pb同位素定年结果显示五垛山花岗伟晶岩的年龄可分为3组:417.4±2.5 Ma,这组为花岗伟晶岩的结晶年龄,与东秦岭造山带花岗伟晶岩的形成时代相一致;429.5±2.1 Ma和450.9±3.3 Ma,这两组与五垛山花岗岩基的年龄相一致,为花岗伟晶岩脉捕获围岩锆石的年龄.花岗伟晶岩中417.4 Ma、429.5 Ma和450.9 Ma这3组锆石的ε_(Hf)(t)值分别为−5.6~−1.9、−8.7~−1.3和−5.3~−3.4,与秦岭岩群部分熔融形成岩浆岩的Hf同位素值近似.以上显示,五垛山花岗伟晶岩可能来自于秦岭岩群的部分熔融.早泥盆世,东秦岭处于原特提斯后碰撞阶段,后碰撞阶段的拉张作用使地幔减压部分熔融形成镁铁质岩浆,这些镁铁质岩浆底侵下地壳变质基底,使其部分熔融形成花岗伟晶岩的原生岩浆,这些岩浆沿着后碰撞拉张作用形成的通道上侵形成了五垛山花岗伟晶岩脉.The granitic pegmatite exposed in Wuduoshan granitic pluton occurs extensively in volume.However,its formation time,petrogenesis and geodynamic background are still unclear.LA-ICP-MS zircon U-Pb dating shows that the zircon U-Pb ages from the granitic pegmatite are 417.4±2.5,429.5±2.1 and 450.9±3.3 Ma,respectively,the first of which represents the crystallization age of granitic pegmatite and the other is consistent with the age of Wuduoshan granite batholith,representing the captured zircons from the surrounding rocks of granitic pegmatite veins.Theε_(Hf)(t)values of granitic pegmatite are−5.6 to−1.9,−8.7 to−1.3,and−5.3 to−3.4,respectively,which are similar to the Hf isotopic values of magmatic rocks derived from partial melting of metasedimentary rocks of the Qinling Group.Together with the regional data,it is suggested that the East Qinling was in the post-collision stage relevant to the proto-Tethys Ocean in the Early Devonian,and it underwent extensional setting and resulting the decompression melting of mantle and generation of mafic magma.The rising high-temperature magma further underplated and heated the lower crust and induced the partial melting of metamorphic basement of the lower crust,ultimately generating the granitic pegmatites along the magmatic conduits which formed in a postcollision-related extensional setting.

关 键 词：东秦岭 花岗伟晶岩 锆石LA-ICP-MS定年 微量元素 岩石学 

分 类 号：P581[天文地球—岩石学]