鲁东昆嵛山地区宫家辉长闪长岩成因:岩石地球化学、锆石U-Pb年代学与Hf同位素制约  

Petrogenesis of Gongjia gabbro-diorite in the Kunyushan area,Jiaodong Peninsula:Constraints from petro-geochemistry,zircon U-Pb dating and Hf isotopes

作　　者：胡芳芳[1] 范宏瑞[1] 杨进辉[1] 翟明国[1] 谢烈文[1] 杨岳衡[1] 柳小明[2] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]西北大学大陆动力学国家重点实验室,西安710069

出　　处：《岩石学报》2007年第2期369-380,共12页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40625010和40421202)资助

摘　　要：宫家辉长闪长岩是鲁东昆嵛山地区出露面积最大的基性侵入体。锆石LA-ICP-MS U-Pb定年表明,其侵位于113±2Ma。高MgO含量(Mg~#高达56),Hf同位素组成位于华北克拉通地壳演化线之上,说明其地幔来源的特征。在地球化学特征上,富集K、Rb、Ba、Th、U等大离子亲石元素和轻稀土元素,亏损Nb、Ti、P等高场强元素;I_(Sr)为0.70745～0.70812,ε_(Nd)为～15.9～-12.0,Sr、Nd和Pb同位素组成[(^(206)Pb/^(204)Pb)_i=17.108～17.239]与胶东基性脉岩和胶莱盆地青山组火山岩相似;锆石Hf同位素组成比较均一,ε_(Hf)(t)平均值为-16.7,这些特征都暗示其来源于富集的华北岩石圈地幔。地球化学研究表明宫家辉长闪长岩经历了分离结晶作用,是胶东乃至中国东部岩石圈减薄的产物。Abstract Gongjia gabbro-diorite pluton is the biggest outcropped basic intrusion in the Kunyushan area, Jiaodong Peninsula. Zircon LA-ICP-MS U-Pb dating gives that its emplacement age of 113±2Ma. Their low SiO2 and high MgO content （Mg^# up to 56） indicate that the gabbro-diorite was originated from a mantle source. The rocks are enriched in LREEs and LILEs, such as K, Rb, Ba, Th and U, and depleted in HFSEs, such as Nb, Ti and P. They have initial Sr isotopic ratios （ Isr） of 0.70745 ~ 0.70812 and БNd values varying from - 15.9 to - 2.0. Sr and Nd isotope, together with Pb isotope [ （^206 pb/^204 Pb）i = 17.108~17.239 ], of the gabbro-diorite are similar to those of mafic dykes and Cretaceous Qingshan group volcanic rocks in the Jiaolai basin. Zircon Hf isotope composition is relatively homogeneous with an average БHf（t） value of - 16.7, indicating that their parental magmas were derived from an enriched lithospheric mantle beneath the North China, coupled with fractional crystallization. The Gongjia gabbro and diorite pluton was result of lithospheric thinning in the Jiaodong Peninsula and even eastern North China craton in the early Cretaceous.

关 键 词：辉长闪长岩 地球化学 LA-ICP-MS锆石U-PB定年 岩石成因 宫家 鲁东 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]