内蒙古黑鹰山富铁矿床磷灰石稀土元素地球化学特征  

Rare Earth Element Features of Apatite Separated from the Heiyingshan High-Grade Iron Deposit, Inner Mongolia

作　　者：聂凤军[1] 江思宏[1] 刘妍[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037

出　　处：《地球学报》2005年第5期435-442,共8页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:40073015);国家地质调查项目(编号:K1.3.32)资助。

摘　　要：笔者首次对内蒙古西部黑鹰山富铁矿床两类铁矿石磷灰石进行了稀土元素含量分析,致密块状铁矿石6件磷灰石样品∑REE含量变化范围为(14 776.86～21 313.18)×10-6,LREE/HREE比值为8.31～9.18,δEu为0.37～0.40.相比之下,脉状铁矿石2件磷灰石样品∑REE含量变化范围为(18 143.05～20 665.82)×10-6,LREE/HREE比值为9.03～9.18,δEu为0.39.所有8件磷灰石稀土元素分配型式均为一组向右倾斜,并且具有明显铕负异常的曲线.黑鹰山铁矿床中磷灰石的最显著特点是稀土元素含量明显高于国内外同类铁矿床磷灰石,为我国宁芜铁矿床和瑞典基鲁纳铁矿床磷灰石的4～10倍.根据磷灰石样品的地球化学特征,并且结合其他岩(矿)相学特征和钐-钕同位素数据,可以推测,磷灰石的形成作用与海西早期构造-岩浆活动有关,富铁矿床很可能是富碱岩浆热液流体喷溢或上侵定位的产物,成矿(岩)物质主要来自以幔源物质为主的壳-幔混源岩浆房.Located at southeastern part of the Hongshishan-Heiyingshan terrane within the Kazakhstanian-Beishan plate, the Hei-yingshan deposit is one of the most important high-grade iron deposits in northwestern China. Iron mineralization occurs within Early Carboniferous dacite, rhyolite, dacitic lava and brecica of Baishan Formation in the forms of massive blocks, stratoid layers, lens and veins. The iron-bearing intermediate-acid volcanic sequences are cut by a number of Hercynian marie and granitoid dykes and controlled by quite a few NE- and EW-trending fracture or fault zones. Individual iron orebodies can be traced along the strike for 115 to 200 m, and downdip for 100 to 200 m, being 4 to 12 m in thickness. Moreover, several independent yttrium orebodies were found within the iron deposit. Although apatite predominates over iron-bearing minerals, no difference has been observed between the iron and yttrium orebodies in geological setting, wall rock, mineral assemblage and attitude. Mineralogical composition of both iron and yttrium ores is relatively simple, consisting of magnetite, hematite and trace amounts of pyrite. Gangue minerals include apatite, quartz, chlorite, and hornblende. Eight apatite separates from the massive and vein type iron ores were selected for REE analysis. The REE content of the eight apatite samples ranges from 14 776× 10^-6 to 21 313 × 10^- 6, four times that of the apatite separates from the Ningwu iron deposit in the lower and middle Yangtze valley and the Kiruna iron deposit in Sweden. LREE/HREE and δEu values of these eight apatite separates are 8.31～9.18 and 0.37～0.40, respectively. All these apatite samples show an overall negative chondrite-normalized REE slope and negative Eu anomalies. Combined with Sm-Nd isotopic data of apatite separates as well as other field and geological evidence, the authors believe that the ore-forming materials of the massive iron ores might have been formed by a mixed source of depleted mantle- and crustal-derived magma or fluids. In contrast, t

关 键 词：富铁矿床 磷灰石 稀土元素 矿床成因 黑鹰山 内蒙古 稀土元素地球化学特征 内蒙古西部 铁矿床 黑鹰 

分 类 号：P619.14[天文地球—矿床学] S759.94[天文地球—地质学]