福建晋江中-基性岩墙群的锆石SHRIMP U-Pb定年和岩石地球化学  

SHRIMP U-Pb Dating and lithogeochemistry of basic-intermediate dike swarms from Jinjiang,Fujian Province.

作　　者：董传万[1] 张登荣[1] 徐夕生[2] 闫强[1] 竺国强[1] 

机构地区：[1]浙江大学地球科学系,杭州310027 [2]南京大学地球科学系,南京210093

出　　处：《岩石学报》2006年第6期1696-1702,共7页Acta Petrologica Sinica

基　　金：国家自然科学基金(批准号:40372035);国家杰出青年科学基金(批准号:40125007)资助项目成果之一。

摘　　要：福建晋江晚中生代中-基性岩墙群可分为两期:早期岩墙群,岩性为角闪辉绿岩,近东西走向(N70-85E),锆石SHRIMP U-Pb年龄为90±2Ma;晚期岩墙群,岩性为微晶闪长岩,北东走向(N35～50E),锆石SHRIMP U-Pb年龄为87±2Ma。两期岩墙群沿晚中生代花岗片麻岩的节理侵入。在地球化学上,它们具有轻稀土元素和大离子亲石元素富集、高场强元素亏损等特点,I_(Sr)=0．7045～0．7053,ε_(Nd)(t)=-1．18～-1．97,与金门、小金门岛的镁铁质岩墙群相似,也和闽东南晚中生代基性火成岩(辉长岩、玄武岩)的一致。它们是起源于受消减作用影响的岩石圈地幔部分熔融而产生的玄武岩浆,经岩浆分异作用,在拉张的构造环境中侵入形成。The Jinjiang basic-intermediate dike swarms from southeast Fujian are further divided into two groups. The earlystage dike consist of hornblende diabases. They are distributed approximately along EW direction and are dated at 90±2Ma by the zircon SHRIMP U-Pb method. The late-stage dikes, cutting the early-stage ones, are micro-diorite with NE-SW direction of distribution, and the zircon SHRIMP U-Pb age is 87±2Ma. Two groups of dike intruded always along joints of the late Mesozoic granitic gneiss. Geochemically, they are calc-alkaline series of basalt to andesite compositions with MgO varying from 5.84% to 2.79%. These rocks are enriched in LREE, LILE and depleted in HFSE （especially Ta and Nb）. The Jinjiang basicintermediate dike rocks have limited ranges of Isr values from 0. 7045 to 0. 7053 and εNd（t） values from - 1.18 to - 1.97. The overall elemental and Sr-Nd isotopic characteristics of the Jinjiang basic-intermediate dike swarms are similar to those of mafic dikes from Chinmen and Liehyu islands, and are further consistent with those of the late Mesozoic basic igneous rocks （ gabbros and basalts ） in SE Fujian. It is proposed that the dike swarms were derived from differential basaltic magma produced from partial melting of sub-continental lithospheric mantle which could have been influenced by early subduction processes and formed in the continental extension setting.

关 键 词：锆石SHRIMP U-PB定年 岩石地球化学 中-基性岩墙群 晚中生代 福建晋江 

分 类 号：P588.13[天文地球—岩石学]