胶北晚中生代煌斑岩的岩石地球化学特征及其成因研究  

Geochemical characteristics and petrogenetic investigation of the Late Mesozoic lamprophyres of Jiaobei, Shandong province

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

机构地区：[1]中国科学院地球化学研究所矿床重点实验室,贵阳550002 [2]中山大学地球科学系,广州510275 [3]中国石油化工股份有限公司石油勘探开发研究院,北京100083

出　　处：《岩石学报》2005年第3期947-958,共12页Acta Petrologica Sinica

基　　金：中国科学院知识创新工程重要方向项目(KZCX3-SW-125)领域前沿项目(CJ0403;CJ0406)资助

摘　　要：胶北煌斑岩分别采自龙口、烟台和威海地区。包括拉辉煌斑岩、斜闪正煌岩和角闪煌斑岩。煌斑岩K-Ar全岩年龄变化于89．3-169．5Ma,为晚中生代岩浆活动的产物。在岩石化学组成上,SiO2=42．02％-54．95％,以钙碱性系列为主,岩石以富集大离子亲石元素(LILE)(Ba,U,K,Th)和LREE,亏损高场强元素(HFSE)(Nb,Ta和Ti)为特征,Mg#=33．9- 53．9,Eu／Eu*=0．71-0．89,87Sr／86Sr初始比值0．707642-0．709791,εNd(t)为-17．6--10．4,208Pb／204Pb=37．588- 38．431．207Pb／204Pb=15．423-15．531,206Pb／204Pb=17．204-18．179。表明煌斑岩源自俯冲陆壳(扬子下地壳)在地幔源区发生交代作用时形成的富集型地幔的部分熔融体。考虑到煌斑岩具有大陆边缘弧玄武岩的特征,我们认为煌斑岩在成因上同样与古大洋板块的俯冲作用有关,为碰撞后弧岩浆作用形成的脉岩。The lamprophyres of the Jiaobei are collected from Longkou, Yantai and Weihai, and comprise odinites, hornblende lamprophyres and camptovogesites. K-Ar whole rock ages of the lamprophyres distributed between 89.3Ma and 169.5Ma, showing that the lamprophyres are the result of late Mesozoic magmatism. The contents of SiO2 range from 42.02 % to 54.95 % , they mainly belong to calc-alkaline series. The lamprophyres derived from an enriched lithospheric mantle source, are characterized by Enrichment in large ion lithophile elements （LILE） , such as Ba, U, K, Th , and LREE, depletion in the high field strength elements Nb, Ta and Ti, Mg^# （ 100 × Mg/（ Mg ＋ Fe^2 ＋ ） ） = 33.9 - 53.9, Eu/Eu^＊ = 0.71 - 0.89, （ ^87 Sr/^86 Sr） i = 0. 707642 - 0. 709791, εNd （ t ） = - 17.6 -10.4, ^208Pb/^204Pb = 37. 588 -38.431, ^207Pb/ ^204Pb = 15. 423 - 15. 531, and ^206Pb/ ^204Pb = 17. 204- 18. 179. We interpret that the singular geochemical and isotopic characteristics witness an interaction between the snbducted ancient crust （Yangtze Craton （YC）） and the mantle peridotite. Partial melting of such metasomatized mantle produced the lamprophyres. Taking into consideration the possession of Continent Margin Arc Basalt （CABM） feature, we also advocate that the petrogenesis of the lamprophyres were related with the subduction of the ancient ocean plate, and these rocks were products of post-collision arcmagmatism.

关 键 词：煌斑岩 燕山期 地球化学特征 富集地幔 部分熔融 俯冲作用 

分 类 号：P588.137[天文地球—岩石学]