三塘湖盆地火山岩地球化学特征及晚古生代大地构造环境

The geochemical features of volcanic rocks and architectonic environment in Neopaleozoic era, Santanghu basin

三塘湖盆地晚古生代火山岩的稀土元素总量变化较大 ,球粒陨石标准化的稀土元素配分形式为右倾的富集型 ,Eu异常不明显 ;过渡金属元素球粒陨石标准化曲线高度一致 ,Ti到Ni总体递进亏损 ,Cr和Ni负异常明显 ;不相容元素中 ,Ba和Pb均具有明显正异常 ,Rb为负异常 ,Nb和P以负异常为主。据此分析 ,这些火山岩可能为同源岩浆演化的产物 ,部分幔源岩浆一定程度受到地壳物质的混染。据玄武岩地球化学特征判别 ,三塘湖盆地晚古生代岩浆活动为板内成因 ,与洋中脊和岛弧玄武岩没有明显相关性。

There were several magmacyclothems in Neopaleozoic era, Santanghu basin. The quota curve in gross quantity of rare earth element, which was normalized by meteorite, had a very weak Eu abnormal ,and a high peak in emerged on the right. There were similar features in different curves of transition metal element, which calibrated by pelmeteorite, namely, Cr and Ni, had obvious negative abnormal, as well as there was progressive depleted from Ti to Ni. On the other hand, the characters of incompatible elements showed that the magma series were polluted partly. These features included the high positive abnormal of Ba and Pb, the negative abnormal of Rb, Nb and P. According to these evidences,it was suggested that these volcanic samples belong to same magma series. Further, the geochemical features of volcanic rocks were compared between the samples in Santanghu basin and the classical basalts from different architectonic environment. The result supported that the magmatisms occurred inside of plate, and had no obvious correlation to the volcanic from mid ocean ridge or island arc.