广东大坝岩体基性脉岩地球化学特征及成因

Geochemical Characteristics and Genesis of the Mafic Dikes in Daba Rock Mass in Guangdong Province

广东大坝岩体内的基性脉岩主要呈NWW向、近EW向展布,经岩石取样分析,详细讨论了其地球化学特征及成因。研究表明:主量元素显示其属于板内拉斑玄武岩、钙碱系列;微量元素明显具有富集大离子亲石元素K、Rb、Th,亏损Ba、Sr、Zr、Nb、Ti等特征;样品中稀土元素分馏不明显,轻稀土轻微富集,基本无Eu异常,相似于板内玄武岩;TiO_2含量与岩石圈地幔来源玄武岩值非常接近;微量元素含量比值显示其源自相对富集的地幔源区;岩石成因类型为板块俯冲后在原有薄弱构造带的基础上伸展形成的产物。

The mafic dikes in Guangdong Daba Rock Mass is distributed with NWW trending and near EW trending. Based on rock sampling analysis results of the study area, the geochemical characteristics and genesis of the mafic dikes in Dam Rock Mass in Guangdong Province are studied in detail. The study results show that：the main elements of the mafic dikes show that it is belongs to intraplate tholeiite and calc -alkali series;the trace elements are rich in large ionic lithophile elements K, Rb and Th, and lack of Ba, Sr, Zr, Nb and Ti;the fractional distillation characteristics of rare earth elements in rock sam- ples is not obvious, the light rare earth element is slightly enriched, Eu anomaly is not existed basically, which is similar to intraplate basalt ; the TiO2 contents of the mafic dikes is closely similar to the one of ba- salt of lithospheric mantle ; the ratio of trace element elements show that trace elements is derive from the mantle source region that the trace elements is enriched relatively;the rock genesis is belongs to the stretching production of weak tectonic belts after plate subduction.