金沙江蛇绿岩带蛇纹岩中浅色岩类的成因

浅色岩类的岩石类型包括斜长岩和斜长花岗岩,它们均呈岩块状包裹于蛇纹岩中。浅色岩的正Ｅｕ异常明显,ＲＥＥ参数图解、Ｎｂ／Ｔａ和Ｚｒ／Ｈｆ值等均呈现分离结晶趋势,不相容元素Ｓｒ、Ｂａ、Ｎｂ、Ｔａ、Ｚｒ、Ｈｆ富集,相容元素Ｓｃ、Ｖ、Ｃｏ、Ｎｉ亏损,并与其寄主岩－蛇纹岩形成强烈的互补关系。这些特征表明,浅地是幔源超基性岩浆晚期结晶分异的产物。

Genesis of Leucocratic Rocks in Serpentinite of Jinshajiang River Ophiolite Belt

The leucocratic constituents in serpentinite of Jinshajiang ophilite belt are called leucocratic rocks, which , assuming the massive from, are wrapped in serpentinite. Composed mainly of anorthosite and plagiogranite, the leucocratic rocks show distinct Eu positive anomaly. The REE parametric diagram and variations of Nb/Ta and Zr/Hf values suggest crystallization segregation, characterized by enrichment of incompatible elements such as Sr, Ba, Nb, Ta, Zr and Hf and depletion of Compatible elemelnts like Sr, V, Co and Ni. All of these characteristics are in contrast with their host rock_serpentinite and show that the leucocratic rocks were produced by crystallization differentiation of ultramafic magma.