鲁西～2．6Ga深熔作用：泰山地区浅色脉体的野外地质和地球化学研究

- 2.6 Ga anatexis in western Shandong： Geology and geochemistry of leucosomes in the Taishan area

泰山地区深熔作用十分发育，是鲁西～2.6 Ga 构造热事件的典型代表。广泛分布的2.6 Ga浅色脉体主要是片麻状英云闪长岩在水不饱和的条件下含水矿物发生脱水熔融形成，在局部地区存在水饱和熔融。根据浅色脉体岩相学和地球化学特征，可将其进一步划分为3种类型：具正Eu异常奥长岩浅色体、无明显Eu异常奥长花岗岩浅色体和具负 Eu 异常 花岗岩浅色体。矿物结晶分异对浅色体组成变化起了很大作用。由于有充足的时间和空间，部分斜长石较早结晶出来并聚集形成具正Eu异常的浅色体。剩余熔体继续运移过程中，斜长石、钾长石及石英近同时结晶，组成近等粒镶嵌结构，形成具负 Eu 异常的花岗岩浅色体。无明显 Eu 异常的浅色体最接近原始熔体。

Anatexis was well developed in Taishan, a typical area of the ～2.6 Ga tectonic-thermal event of western Shandong. Widespread leucosomes are mostly generated by partial melting of gneissic tonalite under water-absent conditions, with water-saturated partial melting locally occurring in some locations such as Caishixi. According to geochemical and petrographic features, the leucosomes can be divided into three types, trondhjemitic vein with positive Eu anomaly, trondhjemitic vein with no obvious Eu anomaly and monzonitic vein with negative Eu anomaly. Mineral crystallization differentiation played an important role in their formation. At early stage, plagioclases were crystallized to form crystalline framework. Their accumulation resulted in formation of trondhjemitic vein with positive Eu anomaly, and the residual melt moved up to form monzonitic vein with negative Eu anomaly, in which plagioclase, K-feldspar and quartz show a synchronous crystallization, marked by equigranular texture. The trondhjemitic vein with no obvious Eu anomaly may approximately represent original melt.