大阜山金红石矿床含矿岩体的岩石学特征及其地质意义

Petrology Characteristics and Geological Significance of Ore Rocks in Rutile Deposit of Dafushan

大阜山以赋存金红石矿床而闻名,主体为基性变质岩体,以榴闪岩为主。主要矿物石榴子石、角闪石、斜长石、金红石等主要经历了3个发育期次,不同期次具有不同的产状特征。根据野外地质、岩石学、元素地球化学研究分析,结合区域地质背景资料,认为含矿岩体原岩为辉长岩,具正铕异常,低温中高压环境下变质而成。受扬子板块向华北板块俯冲后快速折返的影响,含矿岩体经历了退变质过程,金红石矿床形成。因此,金红石矿床是变质原岩(辉长岩)在区域变质作用下,经构造演化等综合作用的结果。

The rutile deposit is well known in Dafushan,and garnet-amphibolite is the main metamorphite body of the deposit.As the major minerals,garnet,amphibole,plagioclase,rutile and other minrals have three development stages with different characteristics in each stage.Through the analysis of field geology,petrology,geochemical of the elements,and combined with regional geological background information,it could be concluded that the original rock was the gabbro which had positive Eu anomaly,with the metamorphism in low temperature at the medium or high pressure environment.Since the Yangtze Plate and North China Plate occured subduction and rapid exhumation actions,the rutile deposit went through retrograde metamorphism process when the rutile deposit formed.Therefore,the rutile deposit was a combined action resulted in that original rock（gabbro）experienced tectonic evolution by regional metamorphism.