东川地区菜园子辉绿岩地球化学及构造特征

Geochemistry and Structural Features of Caiyuanzi Diabase from Dongchuan Area

详细分析了东川菜园子地区辉绿岩的地球化学特征,结果表明稀土元素总量较高;w(SiO2)为39.19%～53.31%;w(La)/w(Sm)和w(LREE)/w(HREE)低,反应轻重稀土元素分馏不明显;w(La)/w(Yb)为1.90～4.34,指示轻稀土轻度富集;Eu基本无异常,说明在成岩过程中无斜长石分离结晶;未见Nb、Ta明显异常,说明原始岩浆受地壳物质混染较少。地球化学显示出明显的洋岛玄武岩特征,其形成时代在早元古代末期—中元古代早期,同期康滇地区大量地幔物质上涌。东川地区辉绿岩墙应是大陆裂谷拉张、大量地幔物质上涌、软流圈上隆的岩石圈伸展构造背景下的产物。

Analyzed the geochemistry features of Caiyuanzi diabase from Dongchuan area and found that： the content of rare erath elements was much higher,w（SiO2）was 39.19%~53.31%;w（La）/w（Sm） and w（LREE）/w（HREE） was low which showed the fractionation of light-heavy rare earth was not obvious;w（La）/w（Yb） was 1.90~4.34 wich showed light enrichment of light rare earth;Eu was no abnormalities which showed no plagioclase fractional crystallization in the diagenetic process;Nb and Ta was no obviously abnormalities which showed less contamination of primitive magma by crust materials.Geochemistry analysis showed obviously ocean island basalts,the formation age was at later Early Proterozoic end-eraly mesoproterozoic,and a large number of mantle matter upwelling.Dongchuan diabase should be product of continental rift extensional,massive upwelling of mantle material,asthenosphere upwelling of lithospheric tectonic background.