山西省早白垩纪碳酸岩元素同位素和锆石U-Pb定年研究(英文)  

Geochemical,Sr-Nd isotope,and zircon U-Pb geochronological constraints on the origin of Early Cretaceous carbonatite dykes,northern Shanxi Province,China

作　　者：刘燊[1] 冯彩霞[1] 胡瑞忠[2] 赖绍聪[1] Ian M Coulson 冯光英[2] 杨毓红[2] 

机构地区：[1]大陆动力学国家重点实验室,西北大学地质学系,西安710069 [2]矿床地球化学国家重点实验室,中国科学院地球化学研究所,贵阳550002 [3]国体地球研究实验室,里贾纳大学地质学系

出　　处：《岩石学报》2014年第2期350-360,共11页Acta Petrologica Sinica

基　　金：supported by the Opening Project(201206)of the State Key Laboratory of Ore deposit Geochemistry;National Natural Science Foundation of China(41373028)

摘　　要：碳酸岩广泛出露在华北克拉通的山西省。此文中,针对研究区的碳酸岩墙,我们给出新的地球化学、Sr-Nd同位素和锆石U-Pb年龄。LA-ICP-MS锆石定年结果显示,该岩墙的侵位年龄为132.9Ma,全岩K-Ar年龄为131.3~132.6 Ma。碳酸岩墙具有非常一致的主量元素组成,富集轻稀土元素和大离子亲石元素(Ba、U、Pb、Sr),以及亏损K和高场强元素(Ta、P和Ti)。另外,该岩墙具有相对一致的(87Sr/86Sr)i(0.7079~0.7083)和负的εNd(t)(-16.7^-15.2)。以上地球化学特征表明,该岩墙为大陆地壳和此大陆岩石圈地幔混合时期,受明显地壳混染的下岩石圈地幔的部分熔融作用。Carbonatite dyke swarms are widespread across the North China Craton（ NCC） in Shanxi Province. Here,we present new geochemical,Sr-Nd isotope,and U-Pb zircon age data for representative samples of the dykes. Laser ablation-inductively coupled plasma-mass spectrometry（ LA-ICP-MS） U-Pb analyses yielded a Cretaceous age of 132. 9 ± 0. 6Ma for zircons extracted from one dyke. Whole rock K-Ar ages for three samples range from 131. 3Ma to 132. 6Ma. The carbonatites have highly uniform major element compositions and are enriched in light rare earth elements and large ion lithophile elements（ LILEs; e. g.,Ba,U,Pb,and Sr）,and depleted in K and high field strength elements（ HFSEs; e. g.,Ta,P,and Ti）. The carbonatite dykes have relatively uniform（87Sr / 86Sr） i values that range from 0. 7079 to 0. 7083,and negative values of ε Nd（ t）（-16. 7 to-15. 2）. These data suggest that the dyke magmas were derived from the partial melting of an enriched region of the lower lithospheric mantle,with evident crustal contamination. The carbonatite dykes within the northern NCC formed during the mixing of the continental crust with sub-continental lithospheric mantle.

关 键 词：白垩纪 碳酸岩墙 山西 华北克拉通北部 

分 类 号：P588.313[天文地球—岩石学] P597.3[天文地球—地质学]