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胶北早前寒武纪变质基底多期岩浆-变质热事件:来自TTG片麻岩和花岗质片麻岩中锆石U-Pb定年的证据
引用本文:刘建辉,刘福来,刘平华,王舫,丁正江.胶北早前寒武纪变质基底多期岩浆-变质热事件:来自TTG片麻岩和花岗质片麻岩中锆石U-Pb定年的证据[J].岩石学报,2011,27(4):943-960.
作者姓名:刘建辉  刘福来  刘平华  王舫  丁正江
作者单位:1. 中国地质科学院地质研究所,北京,100037
2. 山东省第三地质矿产勘查院,烟台,264000
基金项目:本文受中国地质科学院地质研究所基本科研业务经费 (J1005)、国家杰出青年科学基金 (40725007) 和中国地质调查局地质大调查项目 (1212010811065) 联合资助.
摘    要:本文采用LA-ICP-MS技术,对胶北地体TTG片麻岩和花岗质片麻岩中锆石进行系统原位U-Pb定年和稀土、微量元素的分析,发现研究区早前寒武变质结晶基底存在多期岩浆-变质热事件。4件TTG片麻岩和2件花岗质片麻岩锆石样品记录了2909±13Ma、2738±23Ma、2544±15~2564±12Ma和2095±12Ma 4组岩浆事件年龄,以及2504±16~2513±32Ma和1863±41Ma 2组变质事件年龄。结合以往TTG片麻岩和花岗质片麻岩的地球化学及Nd同位素研究发现,约2738Ma的TTG岩浆事件可能代表胶北地体地壳最主要的生长事件,而2544~2564Ma的岩浆事件则可能代表古老地壳重熔的最强烈岩浆事件,约2095Ma岩浆事件则反映了胶-辽-吉构造带内部在该时期与地壳拉张作用有关的岩浆活动。2504~2513Ma是研究区以及华北克拉通早前寒武基底最主要的一期变质热事件,可能与地幔柱(热点)岩浆的底侵作用有关,而TTG片麻岩记录的约1863Ma的变质年龄与研究区基性和泥质高压麻粒岩相岩石记录的麻粒岩相变质时代一致,暗示TTG片麻岩可能也经历了古元古代高压麻粒岩相变质作用,上述研究进一步表明胶北地体在古元古代的确存在一期陆-陆碰撞的重要造山事件。该项研究成果对于进一步深入探讨胶北乃至华北克拉通早前寒武纪变质基底的形成演化、岩浆-变质热事件序列及其构造背景具有重要的科学意义。

关 键 词:LA-ICP-MS  锆石U-Pb定年  TTG片麻岩和花岗质片麻岩  胶北地体  胶-辽-吉构造带
收稿时间:2010/12/20 0:00:00
修稿时间:2011/2/14 0:00:00

Polyphase magmatic and metamorphic events from Early Precambrian metamorphic basement in Jiaobei area: Evidences from the zircon U-Pb dating of TTG and granitic gneisses.
LIU JianHui,LIU FuLai,LIU PingHu,WANG Fang and DING ZhengJiang.Polyphase magmatic and metamorphic events from Early Precambrian metamorphic basement in Jiaobei area: Evidences from the zircon U-Pb dating of TTG and granitic gneisses.[J].Acta Petrologica Sinica,2011,27(4):943-960.
Authors:LIU JianHui  LIU FuLai  LIU PingHu  WANG Fang and DING ZhengJiang
Institution:Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Exploration institute of Geology and Mineral Resources, Yantai 26400, China
Abstract:Tonalite-trondhjemite-granodiorite (TTG) gneisses and granitic gneisses are widely distributed in the Early Precambrian metamorphic basement of Jiaobei terrane. In this study, we link cathodoluminescence (CL) images, U-Pb ages, and trace element compositions obtained from distinct zircon domains of complex zircons to unravel the origin, polyphase protolith and metamorphic ages of TTG gneisses and granitic gneisses in Jiaobei terrane. Zircons separated from 6 studied samples record four groups of magmatic ages of 2909±13Ma, 2738±23Ma, 2544±15~2564±12Ma and 2095±12Ma, and two groups of metamorphic ages of 2504±16~2513±32Ma and 1863±41Ma. A combined study of previously geochemical and Nd isotope data provides insight into the nature of TTG gneisses and granitic gneisses in the Jiaobei terrane. The TTG magmatic event took place at ~2738Ma may represent the major crust-growth episode. In contrast, the magmatic event took place at 2544~2564Ma may represent the remelting of the older crustal materials, which was the most significantly magmatic event in the North China Craton (NCC). Whereas the magmatic event took place at ~2095Ma may reflect a period of magmatism related to an extension setting along the Jiao-Liao-Ji tectonic belt. A Neoarchean metamorphic event (2504~2513Ma) may be linked to the underplating of large amounts of mantle-derived magmas which are considered to be related to upwelling mantle plumes (hot-spots). A Paleoproterozoic metamorphic event (~1863Ma) recorded in the TTG gneisses, however, is consistent with the timing of high-pressure (HP) granulite facies metamorphism of mafic and pelitic HP granulites in Jiaobei terrane, implying the TTG gneisses also experienced the Paleoproterozoic HP granulite facies metamorphism. These evidences indicate that a significant continent-continent collision event did take place within the Jiaobei terrane at Paleoproterozoic.
Keywords:LA-ICP-MS  Zircon U-Pb dating  TTG gneiss and granitic gneiss  Jiaobei Terrane  Jiao-Liao-Ji tectonic belt
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