内蒙古敖包吐萤石矿床地质和地球化学特征  

Geological and Geochemical Characteristics of the Aobaotu Fluorite Deposit in Inner Mongolia

作　　者：许东青[1] 聂凤军[1] 江思宏[1] 张万益[1] 云飞[1] 杨才 张天俊 吕旭光 林日亮 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]内蒙古地质调查院,内蒙古呼和浩特010020 [3]内蒙古华生萤石矿业有限公司,内蒙古四子王旗010111

出　　处：《地球学报》2008年第4期440-450,共11页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:40573025);中央级公益性科研院所基本业务费项目(编号:K0814)联合资助

摘　　要：笔者总结了敖包吐萤石矿床的地质特征,并通过萤石的稀土元素的地球化学和Nd同位素研究,探讨了该矿床的成矿作用和成矿物质来源。敖包吐萤石矿床产出于下二叠统大石寨组火山—沉积岩与燕山中期花岗岩的接触带,为单一萤石矿床。萤石矿石的稀土元素的含量(∑REE)变化范围为(8.04～30.04)×10-6,平均为19.42×10-6;轻重稀土LREE/HREE值0.24～0.65,平均0.52;LaN/YbN为0.07～0.62,平均0.26;δEu为0.42～0.90,平均0.60,具Eu负异常和明显重稀土富集的特征。岩矿石的Nd同位素研究表明,萤石矿石的εNd(t)都表现为很大的负值,以成矿主期年龄138Ma计算的εNd(138Ma)为-7.30～-30.55,具有古陆壳的演化特征,暗示其成矿的物质来源主要是壳源物质。在Moller的Tb/La-Tb/Ca成因判别图解中,敖包吐矿床的萤石的结晶作用表现为重新活化的趋势,反映流体具有混源的特征,既有热液成因,又有沉积成因。二叠世的海相火山活动通过海底喷气和喷流的作用形成了初始矿源层,而燕山中期花岗岩浆的侵位与结晶分异,又对初始矿源层的活化和富集提供了流体和热能的来源。成矿流体在经历了长期的演化后在大石寨组的构造薄弱破碎的的部位沉淀析出,形成敖包吐萤石矿床。This paper has comprehensively summarized geological characteristics of the Aobaotu fluorite deposit and discussed its mineralization and material sources on the basis of studying rare earth elements and Nd isotopes. The Aobaotu fluorite deposit is a monomineral-fluorite deposit occurring at the contact zone between the volcanics-volcanogene sedimentary rocks of Lower Permian Dashizhai Formation and the Middle Yanshanian granitoid. REE contents of fluorite ores range from 8.04 × 10^-6 to 30.04×10^-6, 19.42×10^-6 on average, LREE/HREE ratios range from 0.24 to 0. 65 , 0.52 on average, LaN/YbN ratios range from 0.07 to 0.62, 0.26 on average, and δEu range from 0.42 to 0.90, 0.6 on average. The REE pattern shows a HREE-enriched distribution with an obvious Eu negative anomaly. Nd isotope data show evolutionary characteristics of the palaeocontinental crust, with εNd （138 Ma） ranging from -7.30 to -30.55, suggesting that the crust is the main source of this deposit. It is held that the ore-forming fluid is a mixture of waters from different sources, as evidenced by the discrimination diagram of Tb/La-Tb/Ca that reflects the remobilization crystallization trend of fluorite. The marine volcanism in Permian formed the source bed through exhalative sedimentary mineralization, and the Middle Yanshanian granitoid supplied fluid and heat energy for the remobilization and concentration of the source bed. The ore-forming fluid precipitated in the structural fracture zone of the Dashizhai Formation and formed the Aobaotu fluorite deposit.

关 键 词：单一萤石矿床 重稀土元素 地质特征 ND同位素 四子王旗 内蒙古 

分 类 号：P595[天文地球—地球化学] P758.31[天文地球—地质学]