鲁西郗山—关帝庙地区碱性杂岩体微量元素地球化学特征及其意义

Trace Element Geochemical Characteristics and Significance of Alkaline Complex in Xishan-Guandimiao Area in Western Shandong Province

摘要:

本文在详细的岩相学观察基础上，分析研究岩体和矿物的微量元素及稀土元素的特征。结果表明，郗山—关帝庙碱性杂岩体富集Ba、U、Pb、Th及La、Ce，亏损Nb、Ta、Zr、Hf；Nb>Ta，富集轻稀土元素、亏损重稀土元素，轻重稀土分异显著，Ce、Eu无明显异常，关帝庙岩体与郗山岩体的微量元素配分曲线均为右倾型，表明研究区内碱性岩体为同源岩浆，推测初始成岩物质来源于岩石圈地幔部分熔融，其母岩浆为碳酸盐化硅酸岩熔体。郗山岩体发现岩浆型磷灰石和热液型磷灰石，表明郗山岩体的岩浆经历了较强的结晶分异和一定程度的混合作用，并在热液阶段形成大量的轻稀土矿物。

Abstract:

Based on detailed petrographic observations, characteristics of trace elements and rare earth elements in rocks and minerals have been analyzed and studied. It is indicated that Xishan—Guandimiao alkaline complex is enriched in Ba, U, Pb, Th, La, Ce, while depleted in Nb, Ta, Zr and Hf. Nb>Ta. It is enriched in light rare earth elements and depleted in heavy rare earth elements. The differentiation of light and heavy rare earth elements is significant, and there are no obvious abnormalities in Ce and Eu. The trace element distribution curves of Guandimiao and Xishan rocks are similar. It is indicated that the two rock masses are homologous magmas. It is speculated that the diagenetic material initially comes from the product of partial melting of lithospheric mantle, its parent magma is carbonate silicate rock melt. Magmatic and hydrothermal apatite have been found in Xishan rock mass. It is indicated that the magma has experienced strong crystallization differentiation and a certain degree of mixing. A large amount of light rare earth minerals are formed during the hydrothermal stage.