山东中生代基性脉岩的元素地球化学及其成因  

Geochemistry and petrogenesis of the Mesozoic mafic dikes from Shandong Province

作　　者：刘燊[1] 胡瑞忠[1] 赵军红[2] 冯彩霞[1] 曹建劲[3] 

机构地区：[1]中国科学院地球化学研究所矿床地球化学重点实验室,贵州贵阳550002 [2]香港大学地球科学系 [3]中山大学地球科学系,广东广州510275

出　　处：《地球化学》2005年第4期35-46,共12页Geochimica

基　　金：中国科学院知识创新工程重要方向项目(KZCX3-SW-125)~~

摘　　要：研究区脉岩SiO2含量变化范围为48.63%～56.02%,岩性上以煌斑岩、辉绿岩和辉长岩为主,以富集轻稀土元素(LREE)和大离子亲石元素(LILE)、亏损重稀土元素(HREE)和高场强元素(HFSE)为特征。主元素和微量元素研究表明,基性脉岩源区存在明显的地壳混染作用和少量富碳酸岩交代作用,该交代作用可能与扬子下地壳物质的参与有关。The tectonics of Shandong Province is divided into two parts by a long-lived wrench fault zone—Tancheng-Lujiang Fault. The eastern part is named Jiaodong and the western part is called Luxi. Mesozoic mafic dikes are widely distributed in Luxi (Mengyin and Zichuan) and Jiaodong regions of Shandong Province, China, providing an opportunity of investigating the nature of Mesozoic lithospheric mantle beneath the North China Craton (NCC). This paper presents major and trace elements for some newly reported mafic dikes from Shangdong to decipher the geochemistry and petrogenesis of these mafic dikes. The major elements were analyzed by wet chemical analysis at the Institute of Geochemistry, Chinese Academy of Sciences (IGCAS). Analytical uncertainties are from ±1%to 3%for major elements. The rare earth elements and other trace elements were analyzed by ICP-MS at the Isotope Analysis Center of IGCAS. The analytical accuracy is better than 5%for REE, and 10%for other trace elements. The mafic dikes from the Jiaodong region are mainly lamprophyres (spessartites) and gabbros, and the dikes from the Luxi region are gabbros and diabases. The SiO2 contents of the dikes range from 48.63%to 56.02%. Based on the evidence from major and trace elements, the mafic dikes are characterized by enrichment in LREE and LILE (such as Ba, Sr, Pb and K), and depletion in HREE and HFSE (such as Nb, Ti and P). The dikes were derived from partial melting of metasomatized portions of the subcontinental lithospheric mantle (EMⅠ), followed by fractionation of olivine, clinopyroxenes, plagioclase and Ti-Fe oxide. The mafic dikes are characterized by high Rb/Sr and Nb/Ta and normal Zr/Hf ratios, which indicate an early-stage rutile-rich and phlogopite-rich metasomatism and few carbonatite-rich metasomatism affected the source rocks for the mafic dikes. Moreover, in the sources, there exists evident crustal contamination due to the subduction of Yangtze lower crust.

关 键 词：基性脉岩 元素地球化学 岩石成因论 山东省 

分 类 号：P595[天文地球—地球化学]