河北武安矿山村矿田铁矿的稀土元素特征及其地质意义

Rare earth elements characteristics and geological significance of iron deposit in Kuangshancun ore field of Wu’an County, Hebei Province, China

为了解河北武安矿山村矿田两类不同就位环境下的铁成矿差异,对两类铁矿进行了稀土元素地球化学研究;一类为就位于岩体外部接触带的玉石洼型铁矿,另一类为产于岩体内部的五家子型铁矿。前者2件致密块状铁矿样品的∑w(REE)含量变化范围为10.195×10-6～11.615×10-6,w(LREE)/w(HREE)比值为11.639～13.160,δ(Eu)为0.844～0.957;后者3件脉状铁矿石样品∑w(REE)含量变化范围为44.412×10-6～49.840×10-6,w(LREE)/w(HREE)比值为4.387～5.724,δ(Eu)为0.306～0.438。上述5件铁矿样品稀土元素分配型式均为铕异常不明显的右倾曲线,与4件岩体样品稀土特征基本相似,成矿流体与岩浆流体关系密切。五家子磁铁矿稀土总量∑w(REE)较高,具明显铕负异常,轻、重稀土分馏程度低,与典型矽卡岩就位环境下的玉石洼铁矿区别明显。结合矿体产出的野外地质特征,推测除矽卡岩成矿机制外,矿山村矿田内铁矿存在与岩浆关系更密切的成矿机制。

Abstract： In order to clarify metallogenic differences of iron deposit in different locational environments, the contents of rare earth elements of two types of iron ore and wall rock in ore field of Wu＇an County, Hebei Province, China, were analyzed. One is two massive iron ore samples which are from the exterior contact zones of Yushiwa ore deposit （∑w（REE）=10.195×10^-6-11.615×10^-6, w（LREE）/w（HREE）=I 1.639-13.160, d（Eu）=0.844-0.957）. The other is three veinlet iron ore samples inside of Wujiazi ore deposit which are in the form of xenolith （52w（REE）=44.412×10^-6 49.840 N 10^-6, w（LREE）/w（HREE）=4.387-5.724, d（Eu）=0.306-0.438）. The REE distribution of the five samples is right deviation, with slightly negative Eu anomalies, and similar with that of the four rock samples, which show that the origin of ore-forming fluids is closely related with magmatic fluids. In contrast, the total contents of rare earth elements of Wujiazi are high with negative Eu anomalies, and the fractionation of LREE and HREE is weak. Combined with field geological operations, it is speculated that Kuangshancun ore field has certain kinds of ore-forming mechanism closely related with magma expect for skarns ore-forming mechanism.