Rare Earths, Niobium and Tantalum Minerals in Bayan Obo Ore Deposit and Discussion on Their Genesis

Bayan Obo ore deposit is endowed with and lie hidden in the Proterozoic strata. The localities and occurrences of the minerals in the ore deposit were described. It is obviously that some minerals are strata minerals and some are post strata minerals. The rare earths, niobium and tantalum minerals are exactly the post strata minerals. In these minerals the hydrothermal metasomatic phenomena distinctly reveal their metallogenic characteristics. According to tectonic movement, magma activity, mineral paragenesis, hydrothermal metasomatism, geological age and lasting time scale of metallogenesis, and some other factors, it is supposed that genesis of rare earths, niobium and tantalum minerals in Bayan Obo ore deposit are closely related with hydrothermal metallogenic solution which is differentiated from silica acid and carbonic acid magma and derived from deep seated source, and then intruded into Proterozoic strata and metasomatized. It is recognized that the metallogenesis of Bayan Obo ore deposit is undergoing a long geological period and many episodes.

Trace and Rare Earth Element Geochemistry of Micrite Mound Carbonates and Other Related REE Mineralized Carbonates from Bayan Obo Area in Inner Mongolia

Geochemical study on trace and rare earth element geochemistry was carried out for different carbonates including the very REE-rich ones in the main ore bodies, a carbonatite dyke and two micrite mounds from Heilaobao far away from the Bayan Obo ore deposit, and Xishan in west Beijing. The results show that both carbonatite dyke and REE mineralized carbonates (dolomite and marble) in the main ore bodies and outside ore bodies have similarities to each other, with very extreme positive anomaly of Ba, Th, Nb, La, Ce, Nd, Sm, Pb, medium positive anomaly of Y, Ho, Tb, Er, Yb and negative anomaly of Sc, Ti and Cu. The REE concentration in the mineralized carbonates changes greatly, the total REE content changes from 262×10^(-6) in both east and west ore deposits to 104562 ×10^(-6) (10.46%), which is relatively lower than those samples of carbonatite dyke, whose REE contents vary greatly, from 1% up to 20 % of mass fraction. Light REE in the carbonatites are enriched and highly fractionated relative to heavy REE and there is no Eu anomaly. The REE distribution patterns of both mineralized carbonate and carbonatite dyke are of some similarities. However, the sedimentary carbonate micrite of Salinhudong Group in Heilaobao far outside the ore bodies and the pure carbonates from Xishan in Beijing, central part of North China plate, have the similarities in REE distributions with much lower REE contents, which are significantly different from those of carbonatite dyke and REE mineralized carbonate. In Bayan Obo district, both carbonates in the ore deposit and micrite mound outside the ore deposit underwent widespread metasomatism by fluids that resulted in formation of the superlager Fe-Nb-REE mineralization. It appears that the carbonates represent the evolution products of different geological stages.

Geochemical Characteristics of a Carbonatite Dyke Rich in Rare Earths from Bayan Obo, China

The whole-rock geochemistry of a rare earths rich carbonatite dykes that locates at Dulahala and lies 3 km north-east to the East Ore body of the giant Bayan Obo RE-Nb-Fe deposit was analysed. The dyke cuts cross H1 coarse quartz sandstone and H2 fine quartzite of the Proterozoic Bayan Obo group. RE content in the dyke varies greatly up to 20% (mass fraction), which comprises rich RE ores. Light RE in carbonatites are extremely enriched and strongly fractionated relative to heavy RE, but no Eu anomaly. The carbonatite may be produced by mechanisms as follows: the carbonatite mana is directly formed by very low degree (F <1%) partial melting of enriched lithospheric mantle, leaving residual minerals characterized by abundant garnet; then the magma arises into a chamber within the crust where they will undergo fractional crystallization, which makes RE further concentrated in carbonatite. The RE patterns and spider diagrams of the carbonatite are identical to those fine-grained dolomite marble that is the ore-host rock for the Bayan Obo deposit. However, the carbonatite is calcic, which is different from the fine-grained dolomite marble in major element geochemistry. The difference is suggested to be resulted from that the carbonatite dyke is not affected by a large scale dolomitization, while the fine-grained dolomite marble might be the product of dolomitized carbonatite intrusive body that might set up a hydrothermal system in the region, which transported Mg from the Bayan Obo sediments, especially form the shales to the carbonatite intrusion.

A Geochemical Study of an REE-rich Carbonatite Dyke at Bayan Obo,Inner Mongolia,Northern China

An REE-rich carbonatite dyke was found in Dulahala, close to the Bayan Obo superlarge REE-Nb-Fe mineral deposit in Inner Mongolia, northern China. The REE content in the dyke varies greatly, from 1% up to 20% (wt), which might constitute rich REE ores. Light REEs in the carbonatite are enriched and highly fractionated relative to heavy REEs and there is no Eu anomaly. The REE and trace element distribution patterns of the carbonatite are identical to those of fine-grained dolomite marble which is the host rock of the Bayan Obo REE-Nb-Fe superlarge mineral deposit. This indicates a petrogenetic linkage between the REE-rich carbonatite and the mineralizations in this region.

Geology and mineralization of the Bayan Obo supergiant carbonatite-type REE-Nb-Fe deposit in Inner Mongolia, China: A review

The Bayan Obo supergiant carbonatite-related rare-earth-element-niobium-iron(REE-Nb-Fe) endogenetic deposit(thereafter as the Bayan Obo deposit), located at 150 km north of Baotou City in the Inner Mongolia Autonomous Region, is the largest rare-earth element(REE) resource in the world. Tectonically,this deposit is situated on the northern margin of the North China Craton and adjacent to the Xing’anMongolian orogenic belt to the south. The main strata within the mining area include the Neoarchean Se’ertengshan Group and the Mesoproterozoic Bayan Obo Group. Generally, the rare earth, niobium, and iron mineralization within the deposit are intrinsically related to the dolomite carbonatites and the extensive alteration of the country rocks caused by the carbonatite magma intrusion. The alteration of country rocks can be categorized into three types: contact metasomatism(anti-skarn and skarn alteration), fenitization,and hornfelsic alternation. As indicated by previous studies and summarized in this review, the multielement mineralization at Bayan Obo is closely associated with the metasomatic replacement of siliceous country rocks by carbonatite magmatic-hydrothermal fluids. The metasomatic process is comparable to the conventional skarnification that formed due to the intrusion of intermediate-acid magmatic rocks into limestone strata. However, the migration pattern of Si O2, Ca O, and Mg O in this novel metasomatic process is opposite to the skarn alteration. Accordingly, this review delineates, for the first time, an antiskarn metallogenic model for the Bayan Obo deposit, revealing the enigmatic relationship between the carbonatite magmatic-hydrothermal processes and the related iron and rare earth mineralization.Moreover, this study also contributes to a better understanding of the REE-Nd-Fe metallogenetic processes and the related fluorite mineralization at the Bayan Obo deposit.

The Chemistry of Niobium Mineralisation at Bayan Obo,Inner Mongolia,China:Constraints on the Hydrothermal Precipitation and Alteration of Nb-Minerals

As well as world class Fe and REE resources the Bayan Obo mineral deposits also hosts significant niobium resources(estimated as 2.2 Mt Nb with an average grade of 0.13 wt% Nb).Niobium in this study is primarily hosted in aeschynite-(Ce) and(Nd),but with subsidiary amounts of pyrochlore,fergusonite-(Ce),fersmite and columbite.Here we report on the paragenetic and textural setting of aeschynite,pyrochlore and fergusonite in the main ore bodies and in a carbonatite dyke.Niobium in a carbonatite sample is hosted in a phase tentatively(due to significant Ca,Mn and Ti contents) identified as fergusonite-(Ce).Aeschynite occurs overgrowing foliation in banded ores,in fractures and vugs in aegirine-rich rocks and in calcite veins.The composition in all settings is similar,but some examples in banded ores develop significant zonation in Y,Th and the REE,inferred to relate to buffering of halogen acid species to low levels by dissolution and fluoritisation of calcite,and the preferential precipitation of LREE from solution due to lower mineral solubility products compared to the HREE.Although lower in total concentration the ratios of REE in pyrochlore are similar to those of aeschynite and suggest the same metal source.The crystallisation of pyrochlore probably relates to growth in paragenetic settings where carbonates had already been eliminated and hence the buffering of F-species activities in the hydrothermal fluid was reduced.Both aeschynite and pyrochlore show evidence of alteration.Primary alteration of aeschynite resulted in leaching of A-site cations(Ca,REE,Th) and Nb,addition of Fe,and ultimately replacement by Ba-Ti phases(baotite and bafertisite).Secondary,metamictisation enhanced,possibly supergene alteration of pyrochlore resulted in hydration,leaching of A-site cations leading to the development of lattice vacancies and increases in Si.The presence of hydrothermal Nb resources at Bayan Obo suggests there may be potential for further Nb discoveries in the area,whilst the trends in element mobility during alteration have significant implications for the utility of A-B oxides as components of materials for immobilisation of radionuclides.

内蒙古白云鄂博铁-铌-稀土矿床矿化蚀变矿物组合及流体组成

针对内蒙古白云鄂博铁-铌-稀土矿床是否多期成矿及底板白云岩的成因争论,本文通过光薄片岩矿鉴定和扫描电子显微镜研究,获得如下信息:(1)碳酸岩脉、磁铁矿石、蚀变岩及矿化白云岩中矿化蚀变的矿物组成类似,均以磁铁矿(碳酸岩脉中除外)、独居石、氟碳酸稀土矿物(氟碳铈矿等)、方解石、萤石、磷灰石、富钡矿物(重晶石或毒重石)、黑云母、富钠矿物(钠闪石、霓石)等为主,常见硫化物,显示为同一种富含Fe、REE、Ca、Ba、K、Na、Si及挥发分CO_(2)、P_(2)O_(5)、F、S的流体,岩(矿)石的结构构造也显示出明显的一期成矿特点,支持白云鄂博矿床主体是一期成矿事件的产物。(2)稀土矿化与底板白云岩不是同一流体的产物,稀土矿化与方解石为主的碳酸岩脉有关,有可能为火成碳酸岩或浆液过渡态流体;底板白云岩是稀土矿化的围岩,有更多的沉积成因信息,可能为热水沉积岩,或者为热液改造的沉积碳酸盐岩。(3)磁铁矿化与稀土矿化是同一成矿事件的产物,但碳酸岩中缺乏磁铁矿表明,铁质来源与稀土来源是否相同仍需要进一步研究。

Iron recovery and rare earths enrichment from Bayan Obo tailings using Coal-Ca(OH)2-NaOH roasting followed by magnetic separation

The recovery of iron and enrichment of rare earths from Bayan Obo railings were investigated using Coal Ca（OH） 2 NaOH roasting followed by magnetic separation. The influences of roasting temperature, roasting time, coal content, milling time, Ca（OH）2 dosage and NaOH dosage on the iron and rare earths recovery were explored. The results showed that the magnetic concentrate containing 70.01 wt. % Fe with the iron recovery of 94.34G and the tailings of magnetic separation containing 11.46 wt. % rare earth oxides （REO） with the REO recovery of 98. 19% were obtained under the optimum conditions （i. e. , roasting temperature of 650℃, roasting time of 60 min, coal content of 2.0%, milling time of 5 min, and NaOH dosage of 2.0%）. The Ca（OH）2 dosage had no effect on the separation of iron and rare earths. According to the mineralogical and morphologic analysis, the iron and rare earths of Bayan Obo tailings could be utilized in subsequent ironmaking process and hydrometallurgy process.

CaO-SiO_(2)-La_(2)O_(3)体系中最佳稀土富集相的在线分离与表征

内蒙古白云鄂博矿是世界上最大的铁-铌-稀土多金属共伴生矿床,稀土远景储量位居世界第一。在该矿床开采过程中,稀土等有价元素未能得到有效的提取而进入渣中,形成重要的稀土二次资源。为了回收其中的稀土资源,基于白云鄂博冶金矿渣主组元,以CaO-SiO_(2)-La_(2)O_(3)三元基础体系为研究对象,首先明确了该体系的最佳稀土富集相为Ca_(x)La_(4.67-x)(SiO_(4))3O_(1-0.5 x)相。随后引入超重力场,在G=1000、时间10 min、温度1350℃的条件下对Ca_(x)La_(4.67-x)(SiO_(4))3O_(1-0.5 x)稀土相与渣相进行在线分离,得到了高纯稀土相晶体。最后对得到的稀土晶体进行结构表征和Rietveld精修,明确了其具体化学式为Ca_(1.11)La_(3.56)Si_(3)O_(12.36),并获得了该稀土相的晶体结构、晶体数据等信息,进一步完善了稀土相的基础物理化学数据,为稀土资源的回收利用提供了理论依据。

Decomposition of monazite in Bayan Obo rare earth ore by roasting of Na_(2)CO_(3)pellets

To resolve the issue of rotary kiln agglomeration during the sodium carbonate roasting of dolomite rare earth ore,this study introduces an oxidation-sodization pellet roasting method for decomposing mixed rare earth concentrates.The focus of this paper lies in understanding the bonding and roasting mechanism of sodium polyacrylate as a binder to dolomite ore and examining the process index of Na_(2)CO_(3)pellets roasting-acid leaching using X-ray diffraction(XRD),scanning ele ctron microscopy with energy dispersive spectroscopy(SEM-EDS),and zeta potential analysis,The results indicate that sodium polyacrylate facilitates the bonding of sodium carbonate to monazite via adsorption of positive and negative charges,and upon roasting at 750℃for 1.5 h to obtain rare earth oxides.Under conditions of a hydrochloric acid(HCl)concentration of 9 mol/L,a reaction for 60 min,a solid-to-liquid ratio(g:mL)of 1:5,and reaction temperature of 90℃,the leaching rates of rare earth elements and thorium(Th)reached maxima of 85.14%and 95.53%,respectively.The process results in a yield of 47.61%for fluorine(F)and89.25%for phosphorus(P).This research forms a foundation for the sodium carbonate roasting decomposition of mixed rare earth concentrates.

Thermal decomposition mechanism of low-content-fluorite Bayan Obo rare earth concentrate roasted with sodium carbonate and its consequent separation study

Thermal decomposition and phase transformation for the mixture of Bayan Obo rare earth concentrate(BORC)and sodium carbonate(Na2CO3)roasted at different temperatures with weight ratio of 100:20 were studied in detail in our study.The aim of our study is to reveal the nature of roasting reaction between BORC and Na2CO3 and thus providing a new method for processing BORC.The results indicate that BORC can be decomposed completely with Na2CO3 at around 600℃after 3 h.During the calcination process,Ce0.5Nd0.5O1.75,NaF,Na3PO4,and a rare earth double phosphate phase Na3RE(PO4)2 are formed after the decomposition of BORC with Na2CO3.In addition,the thermal decomposition mechanism is determined in the paper.Based on these facts,a clean technique processing BORC was developed.And a CeF3 powder,whose composition was measured and stability was also evaluated,was obtained for some potential application from the new technique.This research is of significance in terms of the Na2CO3-roasting BORC solid reaction study and sheds a light on a potential clean technique for BORC.

In-situ measurement of mineral phase transition and kinetics in roasting process of Bayan Obo mixed rare earth concentrate by sodium carbonate

In this study,the Bayan Obo rare earth concentrates mixed with Na_(2)CO_(3)were used for roasting research.The phase change process of each firing stage was analyzed.The kinetic mechanism model of the continuous heating process was calculated.This study aims to recover valuable elements and optimize the production process to provide a certain theoretical basis.Using X-ray diffraction(XRD),Fourier infrared spectroscopy,scanning electron microscopy with energy dispersive spectrometry,the reaction process and the existence of mineral phases were analyzed.The variable temperature XRD and thermogravimetric method were used to calculate the roasting kinetics.The phase transition results show that carbonate-like substances first decompose into fine mineral particles,and CaO,MgO,and SiO_(2)react to form silicates,causing hardening.Further,REPO_(4)and NaF can directly generate CeF_(3) and CeF_(4)at high temperatures,and a part of CeF_(4)and NaF forms a solid solution substance Na_(3)CeF_(7).Rare earth oxides calcined at a high temperature of 750℃were separated to produce Ce_(0.6)Nd_(0.4)O_(1.8),Ce_(4)O_(7),and LaPrO_(3+x).Then,BaSO_(4),Na_(2)CO_(3),and Fe_(2)O_(3)react to form barium ferrite BaFe_(12)O_(19);the kinetic calculation results show that during the continuous heating process,the apparent activation energy E reaches the minimum in the entire reaction stage in the temperature range of 440-524℃,and the reaction order n reaches the maximum,which indicates that the decomposition product REFO significantly impacts the reaction system and reduces the activation energy.The mechanism function is F(α)=[-In(1-α)]^(1/3).The reaction order n reaches the minimum in the temperature range of 680-757℃,and the apparent activation energy E is large.The difficulty of the reaction increases during the final stage.The reaction mechanism function is F(α)=[1-(1-α)^(1/3)]^(2).Observing the entire reaction stage,the step of controlling the reaction rate changes from random nucleation to three-dimensional diffusion(spherical symmetry).

论内蒙古白云鄂博群和白云鄂博超大型稀土-铌-铁矿床成矿的年代

白云鄂博稀土铌铁矿床具十分独特的地质、地球化学特征,所以多时代成矿是难以置信的。白云鄂博矿床成矿时间势必晚于赋矿白云岩及其下伏地层,而较多的地层古生物证据表明白云鄂博群形成于震旦纪至奥陶纪之间。基于赋矿白云岩是热水沉积形成,碳酸盐脉是同源热液交代变质岩或砂岩等形成的认识,笔者等认为,碳酸盐脉中的锆石可能是变质岩或砂岩中的锆石,它们虽被热液改造,其U-Pb年龄仍可能老于成矿年龄。已报道的白云鄂博矿床Sm-Nd等时线年龄虽然主要集中在1.2～1.6Ga,但也有多个分别为0.4～0.5Ga、0.8～0.9Ga和1.0～1.1Ga的年龄值。笔者等收集了所有已发表的98件白云鄂博矿床矿石、矿物及碳酸岩墙和上覆板岩的Sm-Nd年龄分析数据,用Isoplot程序计算,发现这些数据,除两件异常外,可以拟合成一条直线,相关系数R=0.96325,求得等时线年龄t=1125.8±32.5Ma,εNd=-3.02。这一结果表明在1125.8±32.5Ma白云鄂博Sm-Nd同位素时钟启动,且未再受后来的地质作用扰动,指示成矿作用应晚于或等于1.1Ga,但地质意义尚待研究。若假定Sm-Nd同位素时钟不易被一般地质作用重置,则可以采信白云鄂博矿床辉钼矿的Re-Os模式年龄(439±8Ma)或黄铁矿Re-Os等时线年龄(439±86Ma)为白云鄂博的成矿年龄,这与赋矿地层的古生物化石年代相符。

白云鄂博REE-Fe-Nb矿床稀土氟碳酸盐矿物激光拉曼光谱特征及流体包裹体内稀土子矿物的鉴定

白云鄂博REE-Fe-Nb矿床典型稀土氟碳酸盐矿物都具有碳酸根离子最特征的拉曼振动频率,并普遍出现有氟化物的拉曼光谱振动峰。利用子矿物的激光拉曼谱峰特征,结合矿物晶形和扫描电镜能谱分析结果,可以确定这些子矿物可能为氟碳铈矿和氟碳铈钡矿,说明初始成矿热液中极富含稀土元素。矿脉内多相包裹体中含稀土元素的子矿物是从被包裹体捕获的流体中结晶出来的,是真正的子矿物。激光拉曼光谱仪可以作为鉴定流体包裹体中未知子矿物的较为可靠手段之一。

动态反应池-电感耦合等离子体质谱法精确测定配分差异显著的重稀土元素

采用微波辅助消解样品,以O_2为反应气,动态反应池-ICP-MS（ICP-DRC-MS）法测定样品中Gd、Tb、Dy、Ho、Er、Tm的含量,在选定的工作条件下,除Tm（81.09%）外,其他元素氧化物的产率均在99%以上,轻稀土元素二氧化物离子产率一般都低于0.3%。研究认为,轻稀土元素（Ce、Pr、Nd）二氧化物离子对重稀土（Gd、Tb、Dy、Ho、Er、Tm）氧化物离子的干扰可有效扣除;只有Gd O＋受到未反应的Yb＋的谱线重叠干扰比较严重。白云鄂博稀土矿石样品中Gd元素含量一般比Yb高几十倍,此干扰也可以利用干扰系数校正法扣除。轻、重稀土元素分离后ICP-MS法的测定结果进一步验证了方法的准确性。该法检出限范围为0.002~0.023μg/g,精密度在0.87%~2.18%,完全能够满足白云鄂博稀土矿石样品中重稀土元素的分析要求。

复杂铌矿高温还原熔炼-炉渣冷却结晶富集铌试验

针对白云鄂博铁铌稀土复杂多金属矿中铌矿相种类多、性质差异大、难以利用的难题,提出了复杂铌矿高温还原熔炼-炉渣控温冷却定向结晶富集铌新工艺,考察了碱度(CaO/SiO_(2)比值)、铁还原率、冷却速度对渣中富铌矿相粒度、形貌与组成的影响。结果表明,铌主要富集于铈铌钙钛矿相,碱度是影响结晶矿相组成的关键因素,而铁还原程度不影响结晶矿相组成。降低冷却速度可以有效提高富铌矿相粒度。

白云鄂博稀土氟碳酸盐矿物的LA-ICP-MS多元素基体归一定量分析方法研究

研究稀土氟碳酸盐矿物的激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)成分分析方法能为认识稀土矿床成因提供新的、简便的技术手段。本文选取白云鄂博产的氟碳铈矿和黄河矿,通过对常规基体归一定量法改进,按照稀土氟碳酸盐矿物的晶格配位模式对Ba、Ca元素以(Ba,Ca)CO_3的形式、轻稀土以REECO_3F的形式进行加和归一计算,获得的成分数据结果与电子探针和内标法结果基本吻合。该方法可在ICP-MS因电离能过高、不能准确测量C、F元素的情况下通过基体归一法实现稀土氟碳酸盐矿物多元素的定量分析,并且可替代繁琐的内标法,简化了LA-ICP-MS测试流程。多尺寸束斑条件数据比对结果表明,5μm小束斑条件下数据质量差,但10μm束斑条件下获得的氟碳铈矿成分与其他大束斑条件下的结果较为接近,基本能够满足小颗粒稀土氟碳酸盐矿物元素成分的测定。

迤纳厂矿床:一个“白云鄂博式”铁-铜-稀土矿床

云南武定迤纳厂铁铜稀土矿床是滇中地区具有代表性的元古宙铁铜稀土矿床之一。矿床中除了铁、铜资源外,还伴生有稀土、稀有(铌)、钇、钼、钴等组分。研究表明:稀土元素含量在条纹条带状矿石和脉状矿石中均较高,ΣREE含量分别高达(1 446.83-11 259.23)×10^-6和(2 020.92-3 415.51)×10^-6,尤其富集La、Ce等轻稀土元素;稀有(铌)元素主要富集在条纹条带状矿石中,含量高达(278.8-529.0)×10^-6。由于矿床的矿物组成非常复杂,并且矿石中稀土、稀有(铌)矿物含量相对较少,矿物结晶粒度细小,用传统的测试技术和方法很难识别鉴定,因此矿床的矿物学特征,尤其是稀土、稀有(铌)矿物的赋存状态特征研究一直以来都较为棘手。论文应用矿物表征自动定量分析系统(AMICS),结合扫描电镜能谱仪(SEM-EDS)显微结构原位分析技术,完成了常规岩矿鉴定手段难以完成的矿物定量识别和鉴定,在矿石中发现了含量可观的氟碳钙铈矿、氟碳铈矿和少量的独居石、褐帘石、铌铁矿、褐钇铌矿、硅钍钇矿、含铌金红石等稀有稀土矿物。其中,氟碳铈矿、独居石、铌铁矿、褐钇铌矿等主要富集于条纹条带状矿石中,与铁氧化物、磷灰石、萤石、菱铁矿和早期黄铜矿、黄铁矿等紧密共生;氟碳钙铈矿、褐帘石、硅钍钇矿、含铌金红石等主要局部富集在脉状矿石中,与石英、方解石、绿泥石和晚期黄铜矿、黄铁矿等紧密共生。显然,在铁氧化物和铜硫化物成矿两个阶段均伴随有稀土成矿作用。结合前人的研究成果,笔者将主矿化期划分为铁氧化物磷灰石稀土成矿阶段(Ⅱ-1)和铜硫化物(金)稀土成矿阶段(Ⅱ-2)。其中,氟碳铈矿、独居石、铌铁矿、褐钇铌矿等主要形成于Ⅱ-1阶段,其成矿作用可能与Columbia超大陆裂谷化裂解有关;氟碳钙铈矿、褐帘石、硅钍钇矿、(含铌)金红石等则主要形成于Ⅱ-2阶段,其成矿作用可能与Rodinia超大陆裂解有关。对比研究发现,云南武定迤纳厂铁铜稀土矿床与白云鄂博超大型铌铁稀土矿床在大地构造背景、成矿元素组合、赋矿岩系、矿物组成、成矿时代、稀土来源等方面均有可对比性,初步确定云南武定迤纳厂铁铜稀土矿床是一个“白云鄂博式”矿床。

内蒙白云鄂博稀土矿土壤-植物稀土元素及重金属分布特征

白云鄂博是世界最大的稀土矿山,研究白云鄂博矿区土壤及植物等环境介质中的稀土元素和重金属元素的分布特征,可以为调查矿区环境现状提供基础数据,同时为矿山环境修复提供参考依据。本文采集了白云鄂博稀土矿区的土壤、植物,以及背景区本巴台地区的岩石、土壤、牛粪五类样品,采用电感耦合等离子体质谱法(ICP-MS)测定了样品中15种稀土元素(La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y)及8种重金属元素(Cr、Mn、Ni、Cu、Zn、Cd、Pb、As)的含量,研究这些元素地球化学行为及其在空间上的变化规律。结果表明:①矿区土壤和植物样品均显示出明显的轻稀土富集、重稀土亏损的特征。土壤和植物中含量最高的稀土元素均为Ce,分别达到49.95%及48.55%,与白云鄂博稀土矿富Ce的特征高度一致。②铁花植物的稀土元素总量在空间上呈现出主矿>东矿>东介勒格勒矿段的趋势,与三处矿体本身含矿性变化一致,说明该种植物稀土含量基本受矿体含矿性控制,对生长环境中稀土富集程度指示较准确。③矿区土壤中存在一定程度的Zn(465~778mg/kg)、Cd(1.35~2.23mg/kg)、Pb(181~431mg/kg)累积,其中部分点位Cd、Pb存在超出风险管制值的现象。综上,白云鄂博的矿石、土壤、植物样品均表现出富Ce的特征,且植物稀土含量与其所生长处的矿体含矿性强弱高度相关,三者之间稀土含量特征表现出明显继承性。此外,矿区局部点位土壤存在的Zn、Cd、Pb累积需要引起适当关注。

白云鄂博霓石型低品位铁-稀土矿石矿选矿试验研究

针对白云鄂博混合型铁-稀土矿石生产的铁精矿和稀土精矿回收率低、杂质含量高的问题,按照矿石类型进行分类选别。以霓石型低品位铁-稀土矿石为对象,在系统研究其矿石性质的基础上进行回收铁、稀土的选矿试验。研究结果表明,原矿中TFe品位为17.50%,稀土REO品位为8.43%,主要的铁矿物为磁铁矿,氟碳铈矿和独居石是主要的稀土矿物;脉石矿物主要是霓石、重晶石和方解石等;通过磨矿-两段弱磁选-再磨-弱磁选回收铁,在一段磨矿细度-0.074 mm 90%、粗选磁场强度和精选磁场强度分别为112 kA/m和96 kA/m、再磨细度和再磨磁场强度为-0.0454 mm 90%和96 kA/m的条件下获得TFe品位65.83%、TFe回收率69.86%的铁精矿;选铁尾矿在浮选温度60℃、水玻璃用量2.1 kg/t、捕收剂H 205用量1.0 kg/t的条件下经一次粗选、两次扫选的闭路试验可获得REO品位为50.89%,回收率为63.17%的稀土精矿。研究结果为白云鄂博矿的分类选矿提供技术借鉴。