粤北牛岱辉绿岩脉的地球化学特征及其成因研究  

Geochemical Characteristics and Genesis of Niudai Diabase Dykes in Northern Guangdong Province

作　　者：曹豪杰 黄乐真 沈渭洲[2] 凌洪飞[2] 黄国龙 邓平[3] 朱捌 

机构地区：[1]核工业290研究所,广东韶关512026 [2]南京大学地球科学与工程学院,江苏南京210093 [3]中国地质科学院地质研究所,北京100037

出　　处：《东华理工大学学报（自然科学版）》2011年第4期323-331,共9页Journal of East China University of Technology(Natural Science)

基　　金：内生金属矿床成矿机制研究国家重点实验室研究项目(2008-I-04);教育部科学研究重大项目(306007)

摘　　要：牛岱辉绿岩脉位于粤北诸广岩体南部。牛岱辉绿岩具有低SiO2(45.04%～48.64%)、高TiO2(2.02%～3.23%)和TFeO含量(17.00%～19.80%)、富集K,Rb,Ba等大离子亲石元素和La,Nd,Eu,Tb等稀土元素、Nb-Ta亏损轻微、稀土总量较高(112.1×10-6～132.7×10-6)、轻稀土富集和未见负Eu异常等特征,与洋岛玄武岩的地球化学特征相似;Zr/Ba,La/Nb,La/Ta,Ti/Y,Ba/Nb,Th/Nb和Th/La等不相容元素比值可与OIB相比较,在构造环境判别图上位于OIB区域。铅(206Pb/204Pb=18.153～18.594,207Pb/204Pb=15.713～15.730,208Pb/204Pb=39.184～39.206)和钕(εNd(t)=3.1～4.3)同位素组成十分相似于OIB值。研究认为,牛岱辉绿岩侵位于地幔物质底辟上涌导致该区岩石圈拉张减薄的构造环境中;其源区具有亏损地幔(DMM)和富集地幔(EMⅡ)两端员混合特征,表明牛岱辉绿岩是由地幔柱和亏损软流圈部分熔融后产生集聚混合形成原始岩浆通过快速侵位而形成。The Niudai diabase dykes, located in the south of Zhuguang pluton of North Guangdong Province, are characterized with low SiO2 （45.04% - 48.64% ）, high TiO2 （2.02% - 3.23% ） and TFeO （ 17.00% - 19.80% ）, enrichment in LILE （ Rb, Ba） and LREE, relatively high ∑REE （ 112.1 × 10^-6 - 132.7 × 10^-6 ）, slightly depletion in Nb and Ta,without negative Eu anomaly. All informations are similar to the basalt from asthenospheric mantle sources. Elements＇ ratios of incompatible elements, such as Zr/Ba, La/Nb, La/Ta, Ti/Y, Ba/Nb, Th/ Nb and Th/La of Niudai diabase are close to the ratios of OIB. The tectonic discrimination diagrams show that the diabases all fall into the range of OIB. The Niudai diabases have Pb isotope （206Pb/204Pb = 18. 153 - 18. 594, 207pb/204Pb = 15.713 - 15. 730,208 Pb/204pb = 39. 184 - 39. 206） and its εNd （t） ranges from 3.1 to 4.3, close to the scope of OIB. The geochemical characteristics indicate that the origin of Niudai Diabase had both ends of members of mixed characteristics of asthenospher mantle and lithosphere mantle, and the hybrid were related to the melts of overlying lithosphere mantle as asthenospher mantle upwelling. The Niudai diabases are formed while the fast invaded of magma in the tectonic environment that lithospher thinning leaded by asthenosphere mantle upwelling.

关 键 词：元素地球化学 Nd—Sr—Pb同位素 洋岛玄武岩 牛岱辉绿岩 粤北 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]