桂北元宝山镁铁超镁铁岩类岩石地球化学及成因研究

Lithogeochemistry and Formation of Mafic-Ultramafic Rocks from Yuanbaoshan Area of Northern Guangxi

桂北元宝山地区镁铁超镁铁质岩主要属于钙碱性和拉斑岩系,岩石的SiO2和MgO含量变化范围较大。在原始地慢标准化曲线上显示右倾特征,Sr,Hf元素中等亏损。元素的稀土配分曲线亦显示右倾,具有Yb正异常特征,这是弧火山岩的明显特征。从主元素及微量元素分析岩石的构造环境并不单一,其成因可能与小型洋中脊闭合有关,即板块会聚岩浆作用的产物,而非地慢柱岩浆作用的产物。

The mafic-ultramafic rocks from northern kaline and tholeiite series. The content of SiO2 and Guangxi have been dominantly ciassified as calc-al- MgO change a wider range. The mafic-ultramafic rocks show steep right-clipping and the depletion of Sr and Hf in primitively mantle normalized patterns. The REE distribution patterns of the rocks also show steep right-dipping and positive Yb anomaly. These show features of island arc volcanic. The rock tectonic environment is analysed. The results show that it is not a single factor. The petrogenesis may be caused by a small median ridge closed and it may be the products of plates convergence rather than derived from mantle plume.