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张昕,吴才来,陈红杰,王楠. 2018. 华北板块南缘伏牛山花岗岩锆石LA-MC-ICP-MS U-Pb定年、Lu-Hf同位素特征及岩石成因. 岩石学报, 34(5): 1517-1538
华北板块南缘伏牛山花岗岩锆石LA-MC-ICP-MS U-Pb定年、Lu-Hf同位素特征及岩石成因
作者单位E-mail
张昕 中国地质科学院地质研究所, 北京 100037  
吴才来 中国地质科学院地质研究所, 北京 100037 wucailai@126.com 
陈红杰 中国地质科学院地质研究所, 北京 100037  
王楠 中国地质科学院地质研究所, 北京 100037  
基金项目:本文受公益性行业科研专项课题(SinoProbe-05-05)、国家自然科学基金项目(41472063)和中国地质调查局项目(1212011120160、12120114079901)联合资助。
摘要:
      伏牛山花岗岩体出露于华北板块南缘,南召县城以北,面积超过4200km2。岩体的岩石组合为花岗岩+花岗闪长岩+石英闪长岩,具有I型花岗岩的特征。花岗岩锆石的LA-MC-ICP-MS U-Pb定年得到145.4±1.0Ma和118.5±0.6Ma,说明岩体形成于燕山期,并经历了至少两期岩浆活动。锆石Hf同位素分析表明,第一期花岗岩的εHft)平均值为-16.53,二阶段模式年龄(tDM2)平均为2216Ma,表明其源岩以壳源物质为主;第二期花岗岩的源岩分为两个部分,一部分花岗岩的εHft)平均值为-13.67,二阶段模式年龄(tDM2)平均为2044Ma,表明其源岩以壳源物质为主,另一部分花岗岩的εHft)平均值为1.61,二阶段模式年龄(tDM2)平均为1073Ma,表明其源岩以新生地壳为主。根据研究结果及区域地质构造分析,认为第一期岩浆作用是由于太平洋板块俯冲导致秦岭造山带断裂构造再活动,发生部分熔融形成小规模的岩浆作用;而第二期岩浆作用是由于太平洋板块俯冲导致岩石圈拆沉,使地幔软流圈的物质上升,形成巨大的热场,引起大陆地壳大规模的部分熔融形成花岗岩浆。最终形成的花岗岩浆沿着华北板块与扬子板块之间的断裂上侵至地壳浅处,形成了伏牛山复式岩体。
英文摘要:
      The granite pluton of Funiu Mountain, which occupies more than 4200km2, is located in the north of Nanzhao City, southern margin of the North China plate. The pluton is comprised of granite, granodiorite and quartz diorite, and has the characteristics of I-type granites. By U-Pb zircon LA-MC-ICP-MS dating, it shows that Funiu plution formed in Yanshanian Period. Moreover, Funiu pluton experienced two magma activities:145.4±1.0Ma and 118.5±0.6Ma. According to Hf isotopes analysis, the source magma of granite formed in the first activity, whose average εHf(t) value is -16.53 and average tDM2 is 2216Ma, is the metaluminous granite magma from continental crust. The source magma of the granite formed in second activity includes two types. The first type of granite, whose average εHf(t) value is -13.67 and average tDM2 is 2044Ma, has the same source magma as the first activity, which is metaluminous granite magma from continental crust. The second type of granite, whose average εHf(t) value is 1.61 and average tDM2 is 1073Ma, has the source magma of composition of juvenile crust and continental crust. Considering the characteristics of geological structure in this area, it can be conducted that the first activity is caused by Pacific plate subduction which leads to a small scale of reactivity of fracture structure in Qinling orogenic belt. The second activity is caused by furthur subduction which leads to subsidence of the lithosphere. It forms granite magma by making materials of the asthenosphere rise, forming a huge thermal field and causing a large scale of partial melting of the continental crust. At the same time, the Yangtze plate and the North China plate experience expansion and form crack. The granite magma follows cracks to surface and form Funiu Mountain pluton.
关键词:伏牛山复式岩体  锆石U-Pb定年  Hf同位素分析  岩石成因
投稿时间:2017-03-02  修订日期:2017-11-01
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