四川稀土精矿的稀土元素和微量元素地球化学特征及开发利用意义

产自广东省梅州市玉水铜矿的景文矿,属于含水、重稀土-矾-铝硅酸盐矿物(简写为HREE-V-铝硅酸盐矿物),其化学结构式为Y₂Al₂V₂⁴⁺(SiO₄)₂O₄(OH)₄,该矿物在全球属首次发现,暂未开展相关研究。相对于含轻稀土矿物,含重稀土矿物在电子探针分析过程中,当被高压电子束轰击时,被激发出来的特征X射线线系繁多,线系之间分布更加密集,彼此之间相互重叠的现象也更为严重,要获得理想数据的难度很大,是亟待解决和突破的技术难题。本文对该矿物进行了精细的电子探针定量分析,获得理想的化学成分数据,为新矿物命名提供了理论数据技术支撑。通过对实验方法的探索和总结获得以下结果：①利用15kV加速电压、100nA束流对试样进行全元素扫描,以此确定出17种元素;②在定量分析过程中,对重叠峰进行了剥离;③利用仪器软件中的Zoom-Peak ID程序,选择出17种元素的分析线系、精确的峰位及上下背景值;④选取合适的标样及测试时间等定量分析条件,最终获得理想的定量分析结果(平均总量97.41wt%)。上述四条也是确保获得理想定量分析数据的关键因素。

     

石笋中稀土元素含量的测定及气候环境意义

首次采用经过改良的外标法校正数据的ICP-MS方法对石笋中的稀土元素含量进行了测定。结果表明,该方法可以用于测定石笋中含量很低的稀土元素,尤其是对含量相对较高的轻稀土元素如La、Ce可以获得较精确的数据。对采集于四川东北部诺水河溶洞群的石笋SJ3的分析结果显示,在相对温暖湿润时期的石笋沉积中稀土元素含量明显增加。可能的原因包括:(1)温暖湿润的气候条件有利于土壤和岩石的化学风化及稀土元素的活化;(2)温暖湿润的气候条件下地下水动力加强,使得地下水中稀土元素的载体(有机质、铁锰胶体和颗粒物质等)增多。因此,石笋沉积中的稀土元素可以用于研究上覆土壤和岩石的化学风化和地下水水文演化。     

云南兰坪县金顶铅锌矿床稀土元素特征及意义

通过对金顶矿床稀土元素的分析,显示稀土总量较低,具有轻稀土比较富集、轻重稀土元素具中等分馏的特征。铕(Eu)在铅锌金属矿物和石膏中比较亏损(δEu=0.06~0.76),表现出负异常;而在褐铁矿、天青石中铕(Eu)比较富集(δEu=0.76~14.95),表现出正异常;表明褐铁矿、天青石与其它铅锌矿物不是同一期的产物;暗示金顶铅锌矿床在沉积之后经受了后期热液的改造叠加成矿作用。这对矿床成因研究及勘查具有一定的参考意义。     

贵州瓮福磷矿床大塘矿段稀土元素地球化学特征

大塘矿段位于贵州瓮福磷矿白岩矿区,矿体（层）赋存于震旦系陡山沱组（Pt₃³d）,根据成矿的先后时间,该矿段形成了a矿层（下矿层）、b矿层（上矿层）2个矿层,矿层中间为一白云岩G夹层,是典型的海相沉积碳酸盐岩型磷矿床。为深入研究该矿段磷矿床的稀土元素地球化学特征,文章通过野外地质调查、光学显微镜观察、X射线荧光光谱（XRF）与等离子体质谱（ICP-MS）、扫描电镜与能谱（SEM-EDS）等实验方法对其进行了较系统的分析。研究结果表明,a、b矿层磷矿石的δCe、δEu呈负异常,b矿层较a矿层负异常值更明显,且Y/Ho比值由a矿层到b矿层逐渐升高,同时结合Ce_anom-Nd关系图,均反映出由a矿层到b矿层的形成环境是由相对还原环境转变为相对氧化环境。b矿层稀土元素PAAS标准化模式曲线较为一致,为中稀土元素略富集的帽状形态,反映磷矿形成过程中明显有生物或有机质参与;b矿层形成过程中经历了较强的水动力搬运,沉积速率较高,沉积时间较短,其ΣREY较a矿层低。大塘矿段a、b两个矿层磷矿石中Y等大部分稀土元素都主要以类质同象形式赋存于胶磷矿中。     

State of rare earth elements in the rare earth deposits of Northwest Guizhou,China

We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No independent rare earth minerals were detected by scanning electron microscope. Elements detected by the electronic probe for the in situ micro-zone of the sample included: O, Al, Si, Ca, Mg, Fe, Ti, K, Na, S, Cl, C, Cu, Cr, V, and Pt. Rare earth elements were not detected by electron probe. (NH4)₂SO₄, (NH₄)Cl, NaCl, and H₂SO₄ were used as reagents in chemical leaching experiments that easily leached out rare earth elements under the action of 10% reagent, indicating that the rare earth elements in ore are mainly in the ionic state rather than present as rare earth minerals.     

Geochemistry of rare earth elements in oceanic phillipsites

The behavior of rare earth elements (REE) was examined in oceanic phillipsites collected from four horizons of eupelagic clay in the Southern Basin of the Pacific. The REE concentrations were determined in the >50-μm-fraction phillipsite samples by the ICP-MS method. The composition of separate phillipsite accretions was studied using the electron microprobe and secondary ion mass-spectrometry. Rare earth elements in phillipsite-only samples are related to the admixture of ferrocalcium hydroxophosphates. The analysis of separate phillipsite accretions reveals low (<0.1–18.1 ppm) REE (III) concentrations. The Ce concentration varies between 2.7 and 140 ppm. The correlation analysis shows that REE (III) are present as an admixture of iron oxyhydroxides in separate phillipsite accretions. Based on the REE (III) concentration in iron oxyhydroxides, we can identify two generations of phillipsite accretions. Massive rounded accretions (phillipsite I) are depleted in REE, while pseudorhombic (phillipsite II) accretions are enriched in REE and marked by a positive Ce anomaly. Oceanic phillipsites do not accumulate REE or inherit the REE signature of the volcaniclastic material and oceanic deep water. Hence, the REE distribution in phillipsites does not depend on the sedimentation rate and host sediment composition.     

Stabilisation of divalent rare earth elements in natural fluorite

Summary ?The occurrence of divalent rare earth elements (Sm²⁺, Yb²⁺, Tm²⁺, and Ho²⁺) in natural fluorite is evaluated using a suite of 37 samples deriving mainly from Sn–W deposits in the Erzgebirge (Germany), Central Kazakhstan, and the Mongolian Altai. Trace element composition was determined by ICP-AES and ICP-MS. The defect structure of the samples was studied by cathodoluminescence (CL), electron paramagnetic resonance (EPR), and optical absorption spectroscopy. Reduction of cubic Sm³⁺, Yb³⁺, Tm³⁺, and Ho³⁺ under radioactive irradiation produces the corresponding divalent centres. Our data suggest a preferable formation of Sm²⁺ and Yb²⁺ under thorium and of Tm²⁺ and Ho²⁺ under uranium irradiation. Irradiation (indicated by intense brownish (thorium) and deep purple (uranium) coloration of fluorite) gives rise to a population of divalent centres in equilibrium with their decay. However, sporadic radioactive irradiation and stabilisation of the divalent state of the REE by other electron defects were found in most cases. Three models of stabilisation of Sm²⁺, Yb²⁺, Tm²⁺, and Ho²⁺ are discussed. The most effective mechanism for Sm, Yb, Tm, and Ho is coupling with Fe³⁺ centres (REE³⁺+Fe²⁺ → REE²⁺+Fe³⁺). Accordingly, the occurrence of Fe³⁺ centres in natural fluorite is regarded to indicate not an oxidising, but rather a reducing environment during fluorite precipitation. Originally incorporated in the divalent form, Fe²⁺ was converted to Fe³⁺ by radioactive irradiation. Such a conclusion is in agreement with the finding of high contents of interstitial fluorine providing tetragonal local compensation of trivalent REE centres in crystals with high Fe³⁺. If Fe is not present, compensation of divalent Sm, Yb, and Tm is achieved by radiogenic oxidation of Ce(Pr, Tb)³⁺ accompanied by charge transfer (REE³⁺+Ce(Pr, Tb)³⁺ → REE²⁺+ Ce(Pr, Tb)⁴⁺). Ho²⁺ is sometimes stabilised by a hole trapped by an electron localised on a F vacancy (Ho³⁺+e⁻ on □_F → REE²⁺+ self-trapped exciton). Because Sm²⁺ is optically active, the stabilisation by Fe³⁺ (stable up to temperatures above 350 °C) or Ce(Pr, Tb)⁴⁺ (unstable even under visible light) in samples may be determined by careful observations in the field. Institut für Geotechnik, ETH Zürich, ETH-H?nggerberg, Zürich, Switzerland Stanford Linear Accelerator Center, Menlo Park, CA, USA Received January 8, 2002; revised version accepted June 10, 2002     

深海稀土分布规律与成矿作用

深海稀土是近年发现的一种富集中-重稀土的新型海洋矿产资源,其资源量远超陆地稀土储量,具有重要的潜在应用价值。中国是继日本之后在国际上第二个开展深海稀土调查研究的国家,2011年以来,先后在中印度洋海盆、东南太平洋和西太平洋深海盆地发现了大面积富稀土沉积区,在全球大洋中初步划分出4个深海稀土成矿带：西太平洋深海稀土成矿带、中—东太平洋深海稀土成矿带、东南太平洋深海稀土成矿带和中印度洋海盆-沃顿海盆深海稀土成矿带。深海富稀土沉积主要发育在深海盆地的沸石粘土和远洋粘土中,属于自生成因;部分发育在洋中脊附近的盆地中,受到热液作用的影响。研究发现,深海粘土中稀土元素主要赋存于生物磷灰石中,海水是稀土元素的主要来源;在早期成岩阶段,稀土元素在深海沉积物中发生转移和重新分配,并最终富集于生物磷灰石中;大水深（CCD面之下）、低沉积速率和强底流活动是深海稀土大规模成矿的主要控制因素。今后需要继续加大深海稀土基础调查,加强深海稀土调查探测技术研发,并开展海陆稀土成矿作用对比研究,揭示深海稀土成矿机制和规律。     

辽宁四道沟热液金矿床中石英的稀土元素的特征及意义

本文用ＩＣＰ－ＭＳ测定了辽宁四道沟金矿矿脉中石英及其中流体包裹体中的稀土元素含量,发现石英的稀土元素配分模式类似于其中流体包裹体的稀土元素配分模式,推断石英中的稀土元素主要赋存于注流体包裹体中,流体包裹体中的稀土元素了石英的稀土元素配分模式,原生包裹中的流体是和石英同源的,其稀土元素指示的是石英形成过程中流体的信息。而次生包裹体中的流体是石英形成后的流体活动产物,其稀土元素指示的是后期流体活动的信     

淮北煤田煤的稀土元素地球化学

采用仪器中子活化分析法（ＩＮＡＡ）测试了淮北煤田６、３煤层１个煤样的稀土元素含量,并探讨了稀土元素地球化学特征,得出以下认识：１１个样吕的平均ΣＲＥＥ为８１．９５３５ｕｇ／ｇ;稀土元素分布模式呈左高右低的、具Ｅｕ负异常的“Ｖ”型曲线。相关分析、聚类分析的结果表明：稀土元素与灰分、陆源碎屑的元素（Ｓｉ、Ａｌ、Ｔｉ、Ｃｒ、Ｃｏ、Ｎｉ、Ｔｈ、Ｔａ、Ｓｃ和Ｒｂ等）的关系密切,而与海相元素（Ｃａ、Ｓｒ等）关     

Mineralogical control of rare earth elements in acid sulfate soils

Major, trace and rare earth element concentrations were measured in porewater, surface water and sediments at an acid sulfate soil site. The concentrations of La and Ce in porewater are up to 1-3 ppm. There is a strong correlation between REE concentration and acidity, except that the maximum concentrations were consistently found below the horizon of maximum acidity, associated with an increase in pH (to ca. 4) and change in mineralogy from jarosite-dominated to goethite-dominated mottles. Jarosite replacement by goethite is as expected with the rise in pH, which in turn is due to the occurrence of a fossil shell bed just below. The rare earth element patterns in the porewaters are enriched in the MREE with respect to Post-Archaean Australian Shale (PAAS). Measurements and calculations show that this is in accord with experiments on low-degree partial dissolution of jarosite, even when the jarosite itself is highly enriched in LREE. There is a clear fractionation in the patterns between the clay-rich soil matrix, which is slightly depleted in the LREE when normalized to PAAS (La/Yb_PAAS ∼0.5), and the secondary mineral phase jarosite, which is enriched in the LREE (La/Yb_PAAS = 15-50). The REE pattern in the porewater changes with the transition from jarosite- to goethite-rich mottles, becoming relatively more enriched in the LREE compared to the HREE, which is consistent with the incongruent dissolution of jarosite to form goethite and the release of greater amounts of jarosite REE to solution, including proportionately more of the jarosite-compatible LREE.Maximum surface water REE concentrations in acidic water were 100-200 ppb La and Ce. REE patterns in surface water were very similar to the porewater transition zone, enriched in the MREE, but asymmetric, relatively enriched in the LREE compared to the HREE.     

含稀土磷矿稀土元素赋存特性

采用化学分析、X射线衍射分析和MLA矿物自动检测技术等手段,对湖北地区伴生稀土磷矿选矿精矿进行元素赋存特性研究,分析了该矿物的化学成分、矿物组成、稀土元素的赋存状态等理化特征。结果表明,稀土元素Ce、Nd、Sm主要赋存在独居石中,Gd、La全部赋存在独居石中,Dy则全部赋存在磷灰石矿物中,Pr全部赋存在磷灰石和独居石的复合矿物中,Y主要赋存在易解石中。独居石是含有稀土元素最多的矿物。磷灰石与稀土矿物相互交生,独居石主要呈稀疏星散浸染状充填于黑云母、萤石和赤铁矿等脉石矿物的粒间、边缘及孔洞中,多数粒度过于细小而与脉石构成极为复杂的镶嵌关系。     

马坑铁矿床稀土元素地球化学研究

引言七十年代以来,许多研究者对马坑铁矿进行过深入的研究。关于该矿床的形成机制,特别是含矿建造中一套中一基性岩石和矿体底板岩石的成因,以及矿石的形成方式等问题,曾引起研究者们的特别关注,并开展了热烈讨论。笔者曾对该矿床的地质一地球化学特征进行了较为详细的研究,并指出它是与石炭纪海底火山活动有关的喷气-热液沉积矿床,成矿流体来源于地热对流海水与玄武岩的反应。本文是上述研究的继续和深入,目的在于为     

Concentrations of rare earth elements in topsoil from East China

Fifty topsoil samples collected from 12 different regions of East China have been analyzed for rare earth elements (REEs). The average REE concentrations of the 50 topsoil samples are much higher than world average and are characterized by LREE-enrichment, HREE-depletion, Eu-depletion and Ce-enrichment. However, the REE concentration is not strongly affected by the climate of the sampling site; it is controlled mainly by parent materials. The plot of Ce/Eu against Eu/Sm is proved to be useful to distinguish different parent materials of topsoil. Each element in the 50 topsoil has a good correlation with its neighboring element. Seven of the 13 values are above 0.987.     

巴尔哲超大型稀有稀土矿床成矿机制研究

巴尔哲矿床中的矿化和非矿化碱性花岗岩主要造岩矿物均为微斜长石、石英、钠闪石和钠长石,但其相对含量及颗粒大小明显不同,且两类岩石中包裹体的组成特征及锆石的结晶习性也有显著差异.主量元素分析显示,矿化与非矿化碱性花岗岩均以富硅、富碱、贫镁和钙为特征,为较典型的非造山A型花岗岩.尽管矿化碱性花岗岩中K_2O和Na_2O的含量均没有明显的增加,但其Na+K/Al、Na_2O+K_2O/CaO、FeO~*/MgO及K_2O/MgO等岩石化学参数与非矿化碱性花岗岩明显不同.在矿化碱性花岗岩中除了矿化的稀土元素及Nb、Zr强烈富集外,U、Th及Y也明显富集,而Ba、Sr、P、Eu和Ti表现为强烈的亏损.在非矿化碱性花岗岩中除了大离子亲石元素Rb略有富集外,稀土元素、Nb、Zr、U、Th、Ta及Y并无明显富集,虽然Sr、P、Eu和Ti也表现为亏损,但与矿化碱性花岗岩相比其亏损程度明显降低.岩相学、岩石化学及微量元素地球化学特征显示,矿化碱性花岗岩不可能是非矿化碱性花岗岩硅化和钠长石化作用的产物,二者应是同一岩浆体系不同演化阶段熔体固结的产物.K/Rb、Rb/Sr及δEu等地球化学参数显示,矿化碱性花岗岩是高演化A型花岗质熔体固结的产物;而岩石学、包裹体及地球化学特征则显示,这种高演化的A型花岗质熔体已经进入了岩浆一热液过渡阶段.巴尔哲矿床稀有稀土元素的超常富集和成矿与A型花岗岩的高演化过程密切相关.     

黔东南煌斑岩类风化壳中稀土元素富集特征及找矿意义

以往研究认为煌斑岩类及其风化壳因规模小且稀土元素难以高度富集,不易形成稀土元素矿床。然而,本文通过对黔东南麻江隆昌、龙山、大塘、石板寨及和尚坟地区20件风化煌斑岩类中稀土元素进行测试分析发现,风化煌斑岩类中稀土元素含量普遍偏高,ΣREE+Y介于558. 78×10-6~2409.94×10-6(平均1461.21×10-6),其中LREE平均1346.44×10-6,HREE平均53.52×10-6,稀土元素具有高度富集甚至成矿的潜力。其中石板寨、和尚坟煌斑岩风化程度较强,稀土元素富集程度较高,隆昌、龙山等地煌斑岩风化程度相对较弱,稀土元素富集程度相对较低。煌斑岩类风化壳中高度富集轻稀土元素,且以La、Ce、Nd、Pr相对富集为特征。电子探针分析表明,风化煌斑岩类中稀土元素多以稀土独立矿物形式存在,其中以独居石为主。     

陈家山矿煤中微量元素和稀土元素地球化学特征

通过对陈家山煤矿中下侏罗统延安组4^#主采煤层中微量元素和稀土元素的测试分析,发现煤中富集亲花岗岩的钨钼族元素W、Mo、Bi、Sn、Ba、Sr和Li,说明该区煤系形成期间的陆源碎屑主要来自花岗岩和花岗片麻岩等中、酸性岩石。4^#煤中ΣREE平均值为98.2×10^-6,稀土元素分布模式十分相似,呈左高右低的宽缓“V”型曲线,Eu负异常明显,反映出稀土元素与陆源碎屑岩关系密切,成煤期间稀土元素来源一致,陆源物质的供应相对稳定。     

中国南方红壤中稀土元素分布的研究

中国南方红壤中稀土元素总量主要集中在１５０￣２００μｇ／ｇ范围内,且土壤剖面层的底土层含量较高;稀土元素分布模式表明,红壤中轻稀土元素间略有分异,而轻,重稀土元素间以及重稀土元素间没有明显分异,稀土元素含量与红壤中有机质,粘粒含量及阳离子交换量间的相关性很弱,而与红壤中铁锰氧化物及磷酸岩呈显著的正相关关系。