山东胶州大西庄辉石巨晶Sr-Nd同位素组成及其源区性质  

Sr-Nd isotopic characteristics of the pyroxene megacrysts from Daxizhuang of Jiaozhou and their source significance

作　　者：李全忠[1,2] 谢智[1] 陈江峰[1] 高天山[2] 

机构地区：[1]中国科学技术大学地球和空间科学学院壳幔物质与环境重点实验室,合肥230026 [2]中国地质调查局南京地质调查中心,南京210016

出　　处：《地质科学》2009年第1期193-201,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：本文得到国家自然科学基金青年基金项目（批准号：40203004）和国家自然科学基金（批准号：40673008）资助.致谢 对南京大学地球科学系张文兰老师在电子探针测试和中国科学技术大学地球和空间科学学院钱卉老师在样品分析过程中的帮助,夏群科教授在成文之初提出富有启发性的建议和评审人提出宝贵修改意见,一并表示衷心感谢.

摘　　要：胶州大西庄玄武岩（73Ma）中的辉石巨晶与寄主玄武岩具有几乎完全相同的同位素组成，其87Sr/86Sr（t）和εNd（t）分别为0.7033～0.704，1、＋4.5～＋6.5和0.7035～0.7038、＋7.1～＋7.6，暗示辉石巨晶和寄主岩具有相同的地幔源区，即辉石巨晶是玄武岩浆在高压下结晶的产物。亏损的同位素特征表明：在白垩世末期（～73Ma），胶东地区的岩石圈地幔已经由富集转变为亏损，表现出类似于中国东部新生代地幔的同位素特征，即表明当时岩石圈减薄（或置换）已经完成。The pyroxene megacrysts hosted by basalt（73 Ma）at Daxizhuang,Jiaozhou and the host basalts showed uniform isotopic compositions, with ^87Sr/^86Sr（t） =0. 703 3 -0. 704 1 and εNd（t） = ＋4. 5 - ＋ 7.6, respectively, which suggested that they were derived from the same mantle source,and the megacrysts were crystallized from the host basaltic magma under high pressure. Moreover,the dating of 73 Ma of Daxizhuang basalts and hosted megacrysts showed the similar depleted isotopic characteristics with Cenozoic basahs from eastern China, implying that the transformation of the isotopic characters of the lithospheric mantle from enrichment to depletion in Jiaozhou,and also the lithosphere thinning was completed in Late Cretaceous（73 Ma）.

关 键 词：辉石巨晶 SR-ND同位素 亏损地幔 晚白垩世 山东胶州 

分 类 号：P588.1[天文地球—岩石学] P597.3[天文地球—地质学]