| 苏莫查干敖包超大型萤石矿床的稀土元素地球化学特征及其成因意义 |
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| 引用本文：XU DongQing,NIE FengJun,QIAN MingPing, LIU Yan,YUN Fei,ZHANG WanYi.2009.REE geochemistry and genesis of Sumochagan Obo superlarge fluorite deposit[J].Mineral Deposits,28(1):29~41 |
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| 基金项目:中央级公益性科研院所基本业务费项目（K0814）和国家自然科学基金（40573025 |
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| 中文摘要:苏莫查干敖包萤石矿床是位于内蒙古四子王旗北部的一个世界级单一萤石矿床，产出于早二叠世大石寨组火山_沉积岩与早白垩世卫境花岗岩体的外接触带上。萤石的成矿作用分为早、晚2期，早期的萤石主要是纹层状、条带状和细晶块状萤石，晚期的萤石主要呈伟晶状、混合伟晶状；而含硫化物的纹层状、细晶块状萤石含量少且分布局限。不同类型萤石的稀土元素配分模式可以分为3类：A类是早期萤石，其稀土元素配分模式表现为略呈轻稀土元素富集的特点，配分曲线近于平坦，没有Eu异常。B类萤石的稀土元素配分模式不具有普遍性，在其配分曲线中自Tb_Er呈现顶背式突起（roof_like）,并具有明显的Eu正异常，主要为含硫化物的纹层状、细晶块状矿石；C类是晚期萤石，稀土元素配分模式表现为重稀土元素富集的特点，既有Eu正异常，又有Eu负异常。A类萤石的稀土元素配分模式代表了萤石成矿作用的早期热液活动的特征，稀土元素在成矿流体中主要以吸附作用存在和运移，成矿流体主要是岩浆来源的高温、高盐度流体，成矿流体与大石寨组流纹岩、流纹质凝灰岩和大理岩的水岩反应是导致萤石从成矿流体中沉淀的主要机制；C类萤石稀土元素配分模式反映了成矿流体经历了较为长期的演化和分异，稀土元素在流体中主要以络离子形式存在和运移，其成矿流体低温、低盐度，有大气降水的加入，指示该阶段萤石从热液中沉淀结晶的主要机制是2种不同端员流体的混合，即岩浆来源的高盐度、高温流体和以大气降水为主要来源的低温、低盐度流体的混合；B类萤石的稀土元素配分模式反映了一次高含硫化物的局部热液事件，在萤石的成矿作用中不具有普遍意义，稀土元素在流体中是以络离子形式存在和运移的。微量元素研究表明各期次萤石的微量元素变化相似，都具有高的Ni含量，指示成矿物质源区的一致性。在Tb/La_Tb/Ca图解中，所有样品都分布在热液萤石区域，指示矿床属于岩浆热液型矿床。 |
| 中文关键词:地质学 稀土元素配分模式 成矿流体 微量和稀土元素 苏莫查干敖包萤石矿床 内蒙古四子王旗 |
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| REE geochemistry and genesis of Sumochagan Obo superlarge fluorite deposit |
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| Abstract:Located in northern Siziwang Banner of Inner Mongolia and lying in the external contact zone between Early Permian Dashizhai Formation and Early Cretaceous Weijing granite batholith, the Sumochagan Obo fluorite deposit is a world_class monomineral deposit. Metallogeny of the deposit can be divided into two stages. The early stage ores are mainly laminated, banded and fine_grained compact massive ores, whereas the late stage ores are mainly megacrystalline and mingled megacrystalline ores. The sulfide_bearing laminated and fine_grained compact massive ores mainly distributed between 9～21 exploratory lines are not ubiquitous in the deposit. The REE patterns of fluorite ores are very complicated and can be divided into 3 groups. The early stage A_type ores basically have poor_fractionation REE patterns and exhibit low LREE_enrichment with no Eu anomaly. The B_type sulfide_bearing laminated ores exhibit Tb_Er roof_like enrichment with weak positive Eu anomaly. The late stage C_type ores show HREE_enriched REE patterns with weak positive Eu anomaly or negative Eu anomaly. The A_type REE patterns indicate the early hydrothermal event. The ore_forming fluids are magmatic fluids with high temperature and high salinity, with REE elements existent and transported in the adsorption style. The fluorites were precipitated from ore_forming fluids through the fluid_rock interaction between fluids and Dashizhai rhyolite, rhyoltic tuffs and marbles. The C_type REE patterns indicate a long_lived evolution and fractionation of the ore_forming fluids, with the REE elements existent and transported in a complex style. The precipitation of fluorites from ore_forming fluids resulted from the mixing of two end_members of fluids, namely fluids with high_salinity and high temperature from magmas and fluids with lower salinity and lower fluids from meteoric water. The B_type REE patterns reflect a local hydrothermal event with high sulfide contents, with the REE elements existent and transported in a complex style. All fluorite samples exhibit similar trace element distributions characterized especially by high Ni contents, suggesting a common source for fluorite. All fluorite samples are plotted in the hydrothermal field of the Tb/La versus Tb/Ca bi_variable diagram, implying that the Sumochagan Obo fluorite deposit is of the magmatic hydrothermal type. |
| keywords:geology, REE patterns, ore_forming fluids, trace and minor elements, Sumochagan Obo fluorite deposit, Sizhiwangqi Banner of Inner Mongolia |
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