吉林省敦化东部地区新生代玄武岩地球化学特征及其地质意义

Geochemical characteristics and geological significance of the Cenozoic basalt in eastern Dunhua area,Jilin Province

吉林省敦化东部地区新生代玄武岩大面积发育,为了解研究区深部地幔源区性质及本区玄武岩形成机制提供了良好的条件。研究区新生代玄武岩岩石学、地球化学特征研究结果表明,玄武岩为稀土元素富集型(LREE为59.56×10^(-6)~211.51×10^(-6)),具有富集大离子亲石元素Rb、Ba、K、P,亏损高场强元素Th、U、Hf的特征,并且Nb(9.49%~49.2%)、Ta(0.56%~3.33%)元素质量分数较高,说明其原始岩浆来源于岩石圈地幔及软流圈地幔的混合,且为在板内张性的构造环境下形成的大陆喷溢玄武岩。

Cenozoic basalts widely occurred in eastern Dunhua area, Jilin Province, which provides an opportunity to identify the nature of deep mantle source and the formation mechanism of basalt in this area. The petrology and geochemistry characteristics showed the Cenozoic basalts of the study area are enriched in light rare earth elements （LREE=59.56×10^-6-211.51×10^-6） and large ion lithophile elements, such as Rb, Ba, K and P. Moreover, they are depleted in high field strength elements, such as Th, U and Hf, and enriched in Nb（9.49%-49.2%）, Ta（0.56%-3.33%）. Then we concluded that the primary magma of the Cenozoic basalts is continental eruption basalts derived from lithospheric mantle and asthenosphere mantle, and formed from inner-plate extensional tectonic environment.