辽宁弓长岭铁矿磁铁富矿的成因研究

Genesis Study of Magnetite-rich Ore in Gongchangling Iron Deposit,Liaoning

在总结辽宁弓长岭铁矿矿床地质特征的基础上,对矿区内磁铁石英岩和磁铁富矿两种矿石的主量元素、微量元素和稀土元素特征进行分析,测试了其氧同位素组成。结果表明：（1）磁铁富矿和磁铁石英岩除了主要成分Fe、S iO2的含量有很大差别外,其他元素的含量并没有太大的差别;（2）磁铁富矿和磁铁石英岩微量元素特征非常地相似,并且二者的稀土配分型式也非常一致,总的稀土配分曲线是稍右倾型或平坦型的,具Eu正异常,显示了二者的一致性和继承性;（3）磁铁石英岩中磁铁矿的δ^18O值变化范围为-4.5‰～1.8‰,包含了磁铁富矿的变化范围,这与磁铁富矿赋存在磁铁石英岩之中的地质产状完全一致,表明富矿是由具负δ^18O值的热液改造磁铁石英岩而形成的;（4）磁铁富矿应该是由区域变质阶段形成的变质水热液（温度在500℃以上,而且氧同位素δ^18O值低,一般为负值）交代条带状磁铁石英岩,通过去硅作用形成的。

Based on the conclusion of the geological characteristics of Gongchangling iron deposit in Liaoning,this study analyzed the characteristics of major elements,trace elements and REE in magnetite quartzite and magnetite-rich ore,and tested their composition of oxygen isotopes.The results show that：（1）the contents of Fe and SiO2 in magnetite-rich ore and magnetite quartzite are much different,while the contents of other elements are less.（2）The characteristics of trace elements in magnetite-rich ore and magnetite quartzite are very similar to each other,the most types of REE distribution are also same,too.The main curves of REE distribution are a little bit right-inclined or just flat,and positive Eu anomaly which express the coherence and inheritability of these two ores.（3）The δ^18O variation range of magnetite is-4.5‰ to 1.8‰ in magnetite quartzite,this range includes that of magnetite-rich ore,which is similar to the geological occurrence of magnetite-rich ore that occurrence in magnetite quartzite.It indicates that magnetite-rich ore is formed by rebuilding the magnetic quartzite by hydrothermal water with negative δ^18O.（4）Magnetite-rich ore should be formed by metasomatism and desilicification of hydrothermal metamorphic water（temperature at 500 ℃ or more and low values of δ^18O,generally negative） with banded magnetite quartzite.