济南和邹平辉长岩的Pb-Sr-Nd同位素特征和岩浆源区中下地壳物质贡献  

Pb-Sr-Nd Isotopic Characteristics of the Gabbros from Jinan and Zouping and the Contribution of the Lower Crust to the Magma Source

作　　者：李全忠[1] 谢智[1] 陈江峰[1] 高天山[2] 喻钢[1] 钱卉[1] 

机构地区：[1]中国科学技术大学地球和空间科学学院中科院壳幔物质与环境重点实验室,合肥230026 [2]南京地质矿产研究所,南京210016

出　　处：《高校地质学报》2007年第2期297-310,共14页Geological Journal of China Universities

基　　金：国家自然科学基金青年基金(40203004);国家自然科学基金(40673008)资助

摘　　要：对鲁西晚中生代济南和邹平辉长岩的Pb-Sr-Nd同位素和元素组成的研究,给出(87Sr/86Sr)i=0.7041～0.7056,εNd(t)=-6.0～-13.0,(Pb/204Pb)i=16.545～16.998,(207Pb/204Pb)i=15.242～15.350,(208Pb/204Pb)i=36.488～36.944(除206SD792表现出高放射成因Pb外)。由于辉长岩的堆晶性质,其微量元素组成不能用于指示其物质来源。与EMⅠ型大洋和大陆玄武岩对比,表明济南和邹平辉长岩的源区具有与EMⅠ地幔端元一致的同位素特征,但在Pb同位素图解上有明显的下地壳物质的贡献。下地壳物质的参与可能与拆沉有关。Pb-Sr-Nd isotopic ratios and element compositions of the gabbros from Jinan and Zouping have been studied. We obtain that （^87Sr/^86Sr）i=0.7041～0.7056,ε Nd（t）=-6.0～-13.0,（^206Pb/^204Pb）i=16.545～16.998,（^207Pb/^204Pb）i=15.242～15.350,（^208Pb/^204Pb）i=36.488～36.944 （except for SD792 possessing highly radiogenic Pb isotopic characteristics） . Trace element characters are not indicative of the source of the gabbros because of their cumulate nature. A comparison with typical EM Ⅰ type oceanic and continental basahs suggests that the mantle source of the Jinan and Zouping gabbros shows an isotopic characteristics similar to that of the EM Ⅰ mantle, but with a significant contribution of the lower crust based on Pb isotopic diagrams. The addition of the lower crust into the mantle may be related to the subduction of the Pacific Ocean Plate, which resulted in the lower crust delamination.

关 键 词：济南和邹平辉长岩 Pb-Sr-Nd同位素特征 EMI地幔 下地壳 岩石圈拆沉 

分 类 号：P597[天文地球—地球化学]