β—钕褐钇铌矿(Fergusonite-beta-Nd)

至今,吐界上已经发现的褐钇铌矿族矿物中仅有钛褐钇铌矿、铈褐钇铌矿、铈-钇-褐钇铌矿……等,而未见有矿物中稀土元素以钕为最富的单斜钕褐钇铌矿的报道^[1,4,5]。     

内蒙白云鄂博西矿褐钇铌矿-褐铈铌矿族矿物的初步研究

最近,通过对内蒙白云鄂博西矿物质成份的研究,在岩心人工重砂样品中发现了褐铈铌矿、褐钇铌矿及其中间变种钇褐铈铌矿。 褐钇铌矿-褐铈铌矿族矿物的组合特征,是白云鄂博矿区所特有的。1964年在该矿区东部接触带发现了与硅镁石、金云母、铈磷灰石、方解石及烧绿石等共生的褐铈铌矿。这次钇褐铈铌矿的发现,在我国尚属首次。 本族矿物Nb_2O_5的含量高达40％以上,仅低于铌铁矿、铌钙矿、烧绿石等少数几种富铌矿     

内蒙白云鄂博褐钇铌矿——褐铈铌矿亚族的初步研究

前言褐钇铌岩族矿物属于正铌钽酸盐矿物。矿物的化学组成可以用ABO_4的一般式来表示。在褐钇铌矿族物中存在着两个完全类质同象系列:一个是铌和钽形成的连续完全类质同象系列,即黄钇钽矿一褐钇铌矿亚族(ΣYTaO_4—ΣYNbO_4系列);另一个是钇族和铈族稀土连续完全类质同象系列,即是本文所要介绍的褐钇铌矿——褐铈铌矿亚族(ΣYNbO_4—ΣCaNbO_4系列)。     

内蒙古白云鄂博铁矿西矿区铁铌稀土物质成分及矿床成因的研究

本文对矿床的赋存地层—白云鄂博群Hg层泥质灰岩、白云岩和各类矿石的物质成分作了系统的研究,获得了矿石中铁、铌、稀土元素赋存状态的较全面的数据,在矿区首次发现铀钍矿、菱铁钙铀链矿(?)镁菱铁矿、菱镁铁矿、菱铁镁矿、铁镁菱锰矿、褐钇铌矿、铌锰矿和碳酸铈钠矿,西矿区发现褐帘石、氟碳铈钡矿、褐铈铌矿、钕方铈石和铁钍石,结合矿床地质综合分析,作者认为白云鄂博铁矿的铁质主要来源于原始沉积的前震旦纪含铁碳酸盐岩;铌稀土矿化主要与海西期花岗岩有关;矿床成因属沉积变质—热液交代富集型。     

内蒙某稀土-铌-铁共生矿床中铌矿物的化学富集方法

内蒙某稀土-铌-铁共生矿床中铌的含量较低(平均在0.0x％),但含有多种的铌矿物。已经发现的有铌铁矿、易解石、黄绿石、铌钙矿、钛铁金红石、包头矿、褐钇(铈)铌矿等,其中有几种铌矿物极少,必须从大量试样中富集挑选。在铌矿物定量和物质成分研究中,更需要从大量原始样中把铌矿物进行富集。本文是用化学法进行铌矿物富集的研究。     

白云鄂博褐钇铌矿族矿物的矿物化学与矿物演化

本文在大量矿物化学资料及高温XRD研究基础上提出了褐钇铌矿族矿物的分类命名方案,详细地研究了该族矿物的化学成分、稀土和特殊稀土组成及固溶关系。发现了M-钍褐铈铌矿、T-钛褐钕铌矿、M-钕褐铈铌矿以及T-钇褐钕铌矿等一批新变种矿物。确定了褐钇铌矿族矿物在时间和空间上的分异演化序列,并讨论了主稀土和特殊稀土在演化过程中的基本行为,首次提出了褐钇铌矿族矿物水解共沉淀形成机理新模式,并确认成矿流体多阶段演化过程中因介质物理化学条件不同,稀土元素配合物呈现的稳定性差异是本族矿物时空演化的根本原因。此外,本文还呼吁对白云鄂博西矿区铕等资源进行评介和开发。     

茨达碱性花岗岩中褐钇铌矿矿物化学特征

本文研究的褐钇铌矿产自钠闪石花岗岩中。茨达钠闪石花岗岩是典型的碱性花岗岩,具有A型花岗岩的岩石化学特征和特征的矿物组合。褐钇铌矿矿物化学特征不同于一般花岗岩产出者,∑Ce、Nb和Th含量较高,Nb/（Nb+Ta）>98％,U/Th=0.3—0.7（原子比）,属褐钇铌矿-褐铈铌矿系列的矿物。天然样品是晶质的,为α相四方变体和β相单斜变体的两相混合物。类质同象杂质较少,成分相对纯净,因而结构稳定性较高,变非晶质化作用微弱。     

浙江临安石室寺NYF型伟晶岩中稀有稀土金属的矿物学行为与成矿过程

浙江临安石室寺伟晶岩位于河桥岩体西北面,属于典型的Nb-Y-F （NYF） 型伟晶岩,富含大量稀有稀土矿物。本文在野外考察和显微镜观察的基础上,结合电子探针背散射电子图像观察与矿物化学成分分析,系统鉴定了石室寺NYF 型伟晶岩中的稀有稀土矿物,揭示了稀有稀土元素的富集、迁移、结晶与成矿过程。研究结果表明：（1） 石室寺伟晶岩中的稀有稀土矿物有铌钽矿物（铌铁矿、铌锰矿、重钽铁矿、细晶石等）、钇矿物（褐钇铌矿、黑稀金矿）、钨矿物（黑钨矿、 白钨矿、铌钨矿物）、铈矿物（独居石、氟铈矿、氟碳铈矿） 和钍矿物等。（2） 铌钨系列矿物的WO3含量在8.30~70.51 wt%之间呈规律变化,可能为铌铁矿与黑钨矿之间形成的一系列多体矿物。（3） 铌铁矿LA-ICP-MS U-Pb 定年结果显示,石室寺伟晶岩的形成年龄为133±2 Ma,与河桥花岗岩具有成因联系。（4） 石室寺NYF 型伟晶岩中稀有稀土元素的成矿过程与其岩浆的结晶演化密切相关：岩浆阶段,锆石、钍石与独居石等矿物最早晶出;岩浆—热液阶段,黑稀金矿、铌铁矿、褐钇铌矿、氟铈矿等稀有稀土矿物逐渐结晶;热液阶段,黑钨矿、铌钨矿物相继形成,同时早期的独居石、氟铈矿受晚期热液交代形成次生铈矿物。     

浙江临安石室寺NYF型伟晶岩中稀有稀土金属的矿物学行为与成矿过程

浙江临安石室寺伟晶岩位于河桥岩体西北面，属于典型的Nb-Y-F （NYF） 型伟晶岩，富含大量稀有稀土矿物。本文在野外考察和显微镜观察的基础上，结合电子探针背散射电子图像观察与矿物化学成分分析，系统鉴定了石室寺NYF 型伟晶岩中的稀有稀土矿物，揭示了稀有稀土元素的富集、迁移、结晶与成矿过程。研究结果表明：（1） 石室寺伟晶岩中的稀有稀土矿物有铌钽矿物（铌铁矿、铌锰矿、重钽铁矿、细晶石等）、钇矿物（褐钇铌矿、黑稀金矿）、钨矿物（黑钨矿、 白钨矿、铌钨矿物）、铈矿物（独居石、氟铈矿、氟碳铈矿） 和钍矿物等。（2） 铌钨系列矿物的WO3含量在8.30~70.51 wt%之间呈规律变化，可能为铌铁矿与黑钨矿之间形成的一系列多体矿物。（3） 铌铁矿LA-ICP-MS U-Pb 定年结果显示，石室寺伟晶岩的形成年龄为133±2 Ma，与河桥花岗岩具有成因联系。（4） 石室寺NYF 型伟晶岩中稀有稀土元素的成矿过程与其岩浆的结晶演化密切相关：岩浆阶段，锆石、钍石与独居石等矿物最早晶出；岩浆—热液阶段，黑稀金矿、铌铁矿、褐钇铌矿、氟铈矿等稀有稀土矿物逐渐结晶；热液阶段，黑钨矿、铌钨矿物相继形成，同时早期的独居石、氟铈矿受晚期热液交代形成次生铈矿物。     

我国大型稀土铌铁矿床中铈-钇-褐钇铌矿的发现

最近,我们在进行内蒙大型稀土铌铁矿床物质成份研究工作时,在人工重砂样品中,遇到一种褐黄色具油脂光泽的微细矿物。经电子探针分析,X光粉晶分析等工作后,我们认为它是褐钇铌矿族物的一个变种——Ce—Y—褐钇铌矿。此矿物在国内未见有人报导,系首次发现。与国外发现的同类矿物在产状上亦完全不同。 Ce—Y—褐钇铌矿赋存于铁矿层底部的白云石型铌、稀土矿石中。与铁白云石、钠闪石、磁铁矿、氟碳铈矿、易解石、钛铣矿、黄铁矿等件生。     

Is the Bayan Obo ore deposit a micrite mound? A comparison with the Sailinhudong micrite mound

The origin of the Bayan Obo ore deposit, the largest REE deposit in the world, has long been debated and various hypotheses have been proposed. Among them is that the Bayan Obo ore deposit is correlated with and has the same origin as the Sailinhudong micrite mound in the southern limb of the Bayan Obo synclinorium. To test this model, the Bayan Obo ore deposit and the Sailinhudong micrite mound are systematically compared for their geological features, elemental geochemistry, and C, O, and Mg isotopic geochemistry. We show that the Bayan Obo ore deposit and the Sailinhudong micrite mound are both calcareous, lens-like in shape, lack bedding features, and are both hosted in a sedimentary formation that consists of clastic sediments and carbonates, unconformably overlying the Archaean–Palaeoproterozoic crystalline basement. However, their geochemical characteristics differ markedly. Compared with the Sailinhudong micrite carbonates, the Bayan Obo ore-hosting dolomite marbles are strongly enriched in LREEs, Ba, Th, Nb, Pb, and Sr, and have very different (PAAS)-normalized REE patterns. Sailinhudong micrite carbonates have higher δ¹³C_PDB and δ¹⁸O_SMOW values, falling into the typical sedimentary field, but the Bayan Obo ore-hosting dolomites are isotopically intermediate between primary igneous carbonatite and typical sedimentary limestone. The δ²⁶ Mg values of the Sailinhudong micrite carbonates are lighter than those of normal Mesoproterozoic sedimentary dolostone, while those of the Bayan Obo ore-hosting dolomite marble are isotopically heavier, similar to δ²⁶ Mg of mantle xenoliths and Bayan Obo intrusive carbonatite. We conclude that the Bayan Obo ore deposit is not correlated with the Sailinhudong micrite mound; it is neither a micrite mound nor an altered micrite mound.     

Study on Composition of Inclusions in Minerals and Simulation Experiment on Hydrothermal Metasomatic Process of the Bayan Obo Iron Deposit

On the basis of the mechanism of formation of mineral inclusions, it may be assumed that a certain relation exists between the compositions of fluid inclusions in various minerals formed at the same stage of hydrothermal activity. In order to study the genetic relationships between different minerals in the Bayan Obo iron deposit, the compositions(K~+, Na~+, Ca~+, Mg~+, F~+, Cl~+, CO_2~(2-), ΣSO_4~(2-) and pH) of inclusions in fluorite(23), hematite(13), magnetite(3), sodium pyroxene(2) and dolomite(5) from the main mine and the eastern mine were determined by using the vacuum decrepitation and leaching methods, and cluster analyses of the data on the compostions were made. The Q-mode cluster analysis indicates that some iron oxide minerals in the deposit are related to dolomite of sedimentary origin, while others are related to fluorite and sodium pyroxene--products of hydrothermal activity. The R-mode cluster analysis shows that the components of the leaching solution may be divided into two groups: one includes CO_2~(2-), Mg~(2+) and H~+(pH), which are obviously associated with dolomite; the other comprises Na~+, K~+, Ca~+, F~+, Cl~+ and SO_4~(2-), which may possibly represent the composition of hydrothermal solutions.The reaction of the Na-F-Cl solution(pH 4.72) with hematite dolomite at 300℃ and 5 × 10~7 Pa and under alternately"static and dynamic" conditions produced large amounts of hematite and fluorite and small amounts of smectite and Na(Fe) silicates, and the hematite-fluorite assemblage accords with the actual geological conditions in the deposit. From a comparison between the compositions of"static" and"dynamic" solution samples, it may be known that the flow reaction facilitates the migration of Fe, F, Ca and other components as well as Na-metasomatism(Na and Si are fixed in a solid phase).The study of the compositions of mineral inclusions and simulation experiments on hydrothermal metasomatism have provided new evidence for the hypothesis of metamorphosed-sedimentary and hydrothermal-remoulding origin of the Bayan Obo deposit, and pointed out emphatically that hydrothermal metasomatism plays an important role in the formation of the mineral deposit, particularly in the main and the east mine.     

钕易解石

易解石为含稀土钛铌钽的复杂氧化物,钕易解石为化学组分中富含钕的易解石。即钛铌钽酸盐类矿物。钕易解石是比较罕见的矿物,它的发现和研究在理论和实用方面均具重要意义。 谢苗诺夫等最先确定出富钕的易解石,而列文星最早指出了命名的原则,谢苗诺夫则认为碱性花岗岩热液脉中或花岗伟晶岩中的易解石富钕。 本文对产自我国内蒙白云鄂博热液交代矿床中的钕易解石进行了分析、研究。     

Chemistry and Evolution of Fergusonite—Group Minerals,Bayan Obo,Inner Mongolia

A new classification scheme of the fergusnoite-group minerals is suggested on the basis of mineral chemistry and high temperature XRD. A number of new varieties such as M-thorian fergusonite-(Ce). M-neodymian fergusonite-(Ce). T-titanian fergusonite-(Nd) and T-yttrian fergusonite-(Nd) have been recognized in the light of detailed chemical studies, particularly with reference to REE, SRE and solid solution relationship. The results indicate strong REE and SRE differentiation and evolution in the fergusonite group, which can be interpretated by differences in the stability of various REE complexes in response to variations in physicochemical conditions during the multi-stage mineralization process in the Bayan Obo ore deposit. The crystallization of the minerals is closely related to hydrolysis of REE and Nb complexes. REE (OH)₃ Nb(OH)₅ coprecipitation, dehydration, polymerization and nucleation.The significance of SRE (Eu)in the western part of the deposit is emphasized. This project was finantially supported by the National Natural Science Foundation of China.     

Geochemical constraints on the genesis of the Bayan Obo Fe-Nb-REE deposit in Inner Mongolia, China

Trace element and isotopic compositions of carbonate from ore bodies, country rock which hosts the ore bodies (H8 dolomite), a carbonatite dyke exposed in Dulahala near Bayan Obo, and rare earth element (REE)-rich dolomite in Bayan Obo have been determined to understand the genesis of the Bayan Obo Fe-Nb-REE ore deposit, the world’s largest resource of REE. The REE and trace element distribution patterns of samples from the REE-rich carbonatite dykes are identical to those of mineralized carbonate rocks, indicating a genetic linkage between the REE-rich carbonatite and mineralization in this region. By contrast, carbon and oxygen isotopes in the mineralized carbonate varied significantly, δ¹³C = −7.98‰ to −1.12‰, δ¹⁸O = 8.60-25.69‰, which are distinctively different from those in mantle-derived carbonatite. Abnormal isotopic fractionations between dolomite and calcite suggest that these two minerals are in disequilibrium in the carbonatite dyke, ore bodies, and H8 marble from Bayan Obo. This isotopic characteristic is also found in mineralized sedimentary marine micrite from Heinaobao, ∼25 km southeast of the Bayan Obo Fe-Nb-REE ore deposit. These facts imply that the carbonate minerals in the Bayan Obo deposit have resulted from sedimentary carbonate rocks being metasomatised by mantle-derived fluids, likely derived from a REE-enriched carbonatitic magma. The initial Nd isotope values of ore bodies and carbonatite dykes are identical, indicating that ore bodies, carbonatite dykes and veins may have a similar REE source.     

新矿物中华铈矿Ba2Ce(CO3)3F

新近发现一种含钡和稀土的氟碳酸盐矿物,经电子探针、矿物化学、X-射线粉品、X-射线能谱、电子衍射、扫瞄电予显微镜和透射电子显微镜等分析,偏光显微镜和反光显微镜光性鉴定,差热分析以及显微硬度、比重和其他物理性质测定,确定是一种新矿物。     

http://www.sciencedirect.com/science/article/pii/S1674987115001310

Bayan Obo ore deposit is the largest rare-earth element(REE) resource,and the second largest niobium(Nb) resource in the world.Due to the complicated element/mineral compositions and involving several geological events,the REE enrichment mechanism and genesis of this giant deposit still remains intense debated.The deposit is hosted in the massive dolomite,and nearly one hundred carbonatite dykes occur in the vicinity of the deposit.The carbonatite dykes can be divided into three types from early to late:dolomite,co-existing dolomite-calcite and calcite type,corresponding to different evolutionary stages of carbonatite magmatism based on the REE and trace element data.The latter always has higher REE content.The origin of the ore-hosting dolomite at Bayan Obo has been addressed in various models,ranging from a normal sedimentary carbonate rocks to volcano-sedimentary sequence,and a large carbonatitic intrusion.More geochemical evidences show that the coarse-grained dolomite represents a Mesoproterozoic carbonatite pluton and the fine-grained dolomite resulted from the extensive REE mineralization and modification of the coarse-grained variety.The ore bodies,distributed along an E-W striking belt,occur as large lenses and underwent more intense fluoritization and fenitization.The first episode mineralization is characterized by disseminated mineralization in the dolomite.The second or main-episode is banded and/or massive mineralization,cut by the third episode consisting of aegirinerich veins.Various dating methods gave different mineralization ages at Bayan Obo,resulting in long and hot debates.Compilation of available data suggests that the mineralization is rather variable with two peaks at~1400 and 440 Ma.The early mineralization peak closes in time to the intrusion of the carbonatite dykes.A significant thermal event at ca.440 Ma resulted in the formation of late-stage veins with coarse crystals of REE minerals.Fluids involving in the REE-Nb-Fe mineralization at Bayan Obo might be REE-F-C02-NaCI-H20 system.The presence of REE-carbonates as an abundant solid in the ores shows that the original ore-forming fluids are very rich in REE,and therefore,have the potential to produce economic REE ores at Bayan Obo.the Bayan Obo deposit is a product of mantle-derived carbonatitic magmatism at ca.1400 Ma,which was likely related to the breakup of Columbia.Some remobilization of REE occurred due to subduction of the Palaeo-Asian oceanic plate during the Silurian,forming weak vein-like mineralization.     

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.