【作者】 费红彩；

【导师】 肖荣阁；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2005， 博士

【摘要】 白云鄂博稀土、铌、铁矿床是世界上超大型的矿床,是世界稀土元素的重要产地。自丁道蘅教授于1927 发现后的几十年里,中外许多地质学家对其进行了大量的研究,尽管已取得丰硕成果,但由于其多种物质混合、多期构造复合、多种成矿作用叠加等,其真正的成因仍然是未解之迷。系统分析国内外近期研究资料,分析总结出目前仍存在一些的一些没有解决的问题:含矿岩性组成及其成因,即白云岩的岩性与成因、近矿岩石富钾板岩的成因、铁矿建造、成矿时代、矿化期次,以及成矿模式。本论文研究野外地质调查中,对含矿围岩—白云岩、富钾板岩和富钠岩石进行了系统研究。在白云鄂博主东矿的东南部发现火山角砾岩和火山震裂岩,认为含矿白云岩为火山沉积建造;在主东矿区发现富钠岩石,并进行了系统研究,在化学分析的基础上对富钠岩石进行了分类,分析了富钠岩石有火山喷发钠长石岩、钠长石钠闪石火山岩,钠闪石热液岩脉、含钠闪石碳酸岩脉及钠闪石化白云岩等;认为富钾板岩是火山期后热水溶液中结晶沉积形成钾长石硅质岩,这只有在火山期后的高温热水阶段才能有钾长石结晶沉淀;总结含矿白云岩、富钾板岩和富钠岩石三者之间在成因方面的关系,认为其属于同一岩浆起源的碱性岩系。对矿区内外广泛出现的碳酸岩脉进行了研究,依据岩石矿物及化学成分将其划分为富钙方解石型、富镁白云岩型和富钠长石闪石型碳酸岩,认为它们与容矿岩石是同源异相产物。结合白云鄂博矿区内的矿物学特征,根据Fe2O3/FeO 比值,将白云鄂博矿床与国内所有类型的铁矿进行类比,认为具有表生结晶沉积特征。通过与世界两大著名稀土矿床—美国玻斯山稀土矿和澳大利亚澳林匹克坝稀土矿,在含矿地层、成矿时间、建造模式等多方面进行对比,分析其与白云鄂博矿床的共性与差异,稀土矿床与陆缘裂谷环境碱性碳酸岩有重要关系。根据系统研究,论文提出白云鄂博矿床是中元古代陆缘裂谷环境地幔来源岩浆在壳幔边界发生熔离分异形成富钠硅酸岩浆和碳酸岩浆喷发地表形成碱性火山岩系。矿床矿化是岩浆熔离与同生热液交代成矿,加里东期与海西期构造及岩浆热液活动对矿床具有明显的改造作用,使得成矿物质再分配,结构构造发生明显变化。更多还原

【Abstract】 Bayan Obo REE-Nb-Fe ore deposit is the world’s largest deposit and world important producer for rear earth elements. Since discovery by Prof. Ding Daoheng in 1927, many geologists have carried out a great sum of research on it. Although great achievement has been made, its genesis is still unknown owning to mixture of minerals, combination of multiple-stage geologic structures and superposition of various metallogenesis, etc. Through studying on up-dated papers published worldwide, we summarized current problems related to the Bayan Obo deposit: genesis of ore-bearing dolomitite and K-rich slate, formation of iron ore, mineralization stages and ore-forming model. A systematic research, along with reconnaissance, was focused on the ore-bearing country rocks-dolomitite, K-rich slate and Na-rich rocks. Discovery of volcanic breccias and volcanic shatter breccias at southeast of the Main and East Orebodies suggests volcanic sedimentary formation of the dolomitic rock. The fact that Na-rich rocks are common at the Main and East Orebodies further indicates their igneous origin. On the basis of chemical analysis, the Na-rich rocks can be classified into volcanic eruptive albititite, albititite-arfvedsonite volcanic rock, arfvedsonitic hydrothermal dykes, arfvedsonite-bearing carbonatite dykes and arfvedsonatized dolomitite and so on. The analysis suggests that the K-rich slate should be K-feldspar siliceous rock crystallizing from post-volcano hydrothermal solution, only on the condition of which the K-feldpar can deposit. The paper concludes genetic relationship between the ore-bearing dolomitite, K-rich slate and Na-rich slate and believes that they are one alkali rock series of comagmatic origin. Extensive study was concentrated on the carbonatite dykes which are common at the ore area. Mineralogically, they can be divided into three types: Ca-rich, Mg-rich and Na-rich carbonatite dykes, which, along with the ore-bearing rocks, are all believed to be comagmatic products Combined with mineralogical characteristics of Fe minerals at Bayan Obo, the paper compares Fe2O3/FeO ratios of the Bayan Obo deposit with those of all kinds of iron deposits in China. The result reflects that the Bayan Obo deposit is featured by supergenetic crystallization sedimentation. Through comparison between the Bayan Obo deposit with the two world’s famous REE deposits, Mountain Pass REE deposit, US, and Olympic Dam REE deposit, AU on the hosting rocks, ore-forming ages, and genetic models, the dissertation summarizes the similarities and differences between them, as well as the important relation between REE deposits and alkali carbonatite at continental margin rift. Based on our research, the paper proposes that the Bayan Obo ore deposit is one group of the alkali volcanic rocks resulting from mantle-driven magma’s exsolution, which causes separation Na-rich silicate magma from carbonatite magma at the boundary of the mantle and crustal, when magma erupts at mid-Proterozoic continental margin rift. Magmatic exsolution and syngenetic hydrothermal replacement are main characteristics of mineralization of the deposit. Structural and magmatic hydrothermal events at the Caledonian and Hercynian imposed distinct reformation to the deposit and redistributed ore-forming material, and was responsible for change in the structure and texture of the deposit.更多还原