华北克拉通五台群LA-ICP-MS锆石U-Pb年龄和Hf同位素特征  

LA-ICP-MS zircon U-Pb and Hf isotopic studies of the Wutai Group and their geological significance

作　　者：陈雪[1,2] 陈岳龙[1] 李大鹏[1] 刘烊[2] 魏娟娟[1] 闫家盼[2] 

机构地区：[1]中国地质大学(北京),北京100083 [2]中国人民武装警察部队黄金地质研究所,河北廊坊065000

出　　处：《地质通报》2015年第5期861-876,共16页Geological Bulletin of China

基　　金：国土资源部公益性行业科研专项项目(编号:201011057-3);国家自然科学基金项目(批准号:40973010)

摘　　要：通过对五台群石咀亚群金刚库组4个典型样品的LA-ICP-MS锆石U-Pb年龄和Hf同位素研究,对五台群的形成时代及华北克拉通新太古代-古元古代期间的地壳演化进行了探讨.锆石U-Pb同位素测定结果表明,侵入金刚库组中的片麻状花岗岩锆石的U-Pb年龄为2548Ma,因此五台群的上限年龄约为2.5Ga;金刚库组黑云母石英片岩和片麻状石英闪长岩的原岩锆石U-Pb年龄分别为2663Ma和2636Ma,因此五台群的下限年龄约为2.7Ga.五台群的地质年龄为2.5-2.7Ga,属于新太古代.锆石Hf同位素研究结果表明,黑云母石英片岩和片麻状石英闪长岩的二阶段Hf模式年龄（tDM2）均为2.8Ga左右,指示2.8Ga左右是五台山区乃至整个华北克拉通地壳生长的重要时期;片麻状花岗岩 tDM2平均为2.57Ga,与锆石结晶年龄非常接近,表明2.5Ga左右也是华北克拉通地壳的主要增生期.地壳的增长是幕式的,2.8Ga和2.5Ga都是华北克拉通地壳生长时期.Zircon LA-ICP-MS U-Pb and Hf isotopic studies of four typical samples from the Jingangku Formation in the Wutai Group were carried out in order to investigate the geochronology of the Wutai Group and the crustal evolution of the North China Craton （NCC） from Neoarchean to Paleoproterozoic. Zircon U-Pb isotopic data reveal that the intrusion of gneissic granite into the Jingangku Formation took place at 2548Ma, so the top boundary age of the Wutai Group is about 2.5Ga; the protolith age of the biotite quartz schist is 2663Ma, the protolith age of the gneissic quartz diorite is 2636Ma, so the bottom boundary of the Wutai Group is about 2.7Ga. The geological age is 2.5-2.7Ga, so the Wutai Group was formed in Neoarchean. Hf isotopic data reveal that both the biotite quartz schist and the gneissic quartz diorite have the average two-stage Hf model age （tDM2） of 2.8Ga, which suggests that- 2.SGa was an important period of crustal growth in the Wutai Mountain area and even in the whole NCC. The average tDM2 of the gneissic granite is 2.57Ga, which is very close to zircon U-Pb age representing the timing of zircon growth, suggesting that -2.5Ga was another important period of crustal growth in the NCC. The crust grew in episodic form, and both -2.8Ga and -2.5Ga repre- sented the crustal growth in the NCC.

关 键 词：华北克拉通 五台群 LA-ICP-MS锆石U-PB年龄 HF同位素 地壳生长 

分 类 号：P597.3[天文地球—地球化学]