大别山地区鸡公山岩体锆石U-Pb年龄、Sr-Nd-Hf同位素特征及其地质意义  

Zircon U-Pb age and Sr-Nd-Hf isotopic characteristics of the Jigongshan granite in the Dabie Mountains and their geological significance

作　　者：唐相伟[1] 杨泽强[1] 周雷强 许德忠 郭跃闪 种凯琳 TANG Xiang-wei;YANG Ze-qiang;ZHOU Lei-qiang;XU De-zhong;GUO Yue-shan;ZHONG Kai-lin(No.3 Institute of Geological&Mineral Resources Survey of Henan Geological Bureau,Zhengzhou 450000,China)

机构地区：[1]河南省地质矿产勘查开发局第三地质矿产调查院,河南郑州450000

出　　处：《岩石矿物学杂志》2022年第6期1047-1060,共14页Acta Petrologica et Mineralogica

基　　金：中国地质调查局地质调查项目(DD2016005237,DD20190570-2020-02);河南省两权价款地质科研项目;河南省财政地质勘查项目。

摘　　要：鸡公山花岗岩是桐柏-大别山造山带的一处重要岩基。为探讨鸡公山花岗岩的岩石成因和动力学背景,指导区域找矿,对鸡公山岩体开展了锆石U-Pb定年、岩石地球化学和Sr-Nd-Hf同位素研究。岩石地球化学分析结果显示,岩体具准铝质-弱过铝质花岗岩特征,属于高钾钙碱性系列;副矿物有少量角闪石,为分异I型花岗岩。锆石U-Pb定年测得岩体年龄值为141.8±0.8 Ma(n=26,MSWD=1.15),表明鸡公山岩体形成于早白垩世。全岩Sr同位素(^(87)Sr/^(86)Sr)i为0.70775~0.70818,εNd(t)值为-19.21~-17.63,两阶段模式年龄为2.49~2.36 Ga。锆石^(176)Hf/^(177)Hf值为0.281845~0.282083,εHf(t)为-29.67~-21.31,两阶段模式年龄为3.07~2.54 Ga。Sr-Nd-Hf同位素特征暗示形成鸡公山岩体的岩浆可能是扬子板块中下地壳新太古代大别表壳岩物质重熔形成。岩体具较高的(La/Yb)_(N)、Sr/Y值,铕负异常不明显,与大别山埃达克型花岗岩特征类似,形成于构造伸展机制下,为尚未发生拆沉的加厚下地壳部分熔融产物。鸡公山岩体可能是岩体内伟晶岩脉的母体花岗岩。Jigongshan granite is an important batholith in Tongbai-Dabie orogenic belt.In order to discuss the petrogenesis and dynamic background of the Jigongshan granite and guide regional prospecting,this paper has carried out zircon U-Pb dating,rock geochemistry and Sr-Nd-Hf isotope studies on the Jigongshan granite.The results show that the pluton is a paraaluminous-weak peraluminous granite,belonging to the high-potassium calc-alkaline series and fractionated I-type granite,accessory mineral includes minor hornblende.Zircon U-Pb dating shows that the age of the Jigongshan pluton is 141.8±0.8 Ma(n=26,MSWD=1.15),indicating that the Jigongshan pluton was formed in the Early Cretaceous.The(^(87)Sr/^(86)Sr)i,εNd(t)values and the two stage model age of whole rock are 0.70775~0.70818,-19.21~-17.63 and 2.49~2.36 Ga,respectively.The^(176)Hf/^(177)Hf,εHf(t)values and the two stage model age of zircon are 0.281845~0.282083,-29.67~-21.31 and 3.07~2.54 Ga,respectively.Sr-Nd-Hf isotopic characteristics suggest that the Jigongshan pluton may be formed by the remelting of Neoarchean middle-lower crust of the Yangtze plate.The granite has high(La/Yb)_(N),Sr/Y values,and inapparent Eu negative anomalies,similar to the adakite-type granite in the Dabie Mountains.The granite formed in extensional structure,as the product of partial melting of the thickened lower crust that has not yet been delaminated.Jigongshan pluton may be the parent granite of pegmatite vein in the pluton.

关 键 词：大别山 锆石年代学 SR-ND-HF同位素 鸡公山岩体 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]