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1.
Geology of Ore Deposits - REE fractionation into cerium Ceg (La–Eu) and yttrium Yg (Gd–Lu) groups, as well as Lasg (La–Pr), Smsg (Nd–Eu), Gdsg (Gd–Dy), and Ybsg (Y,...  相似文献   

2.
The objective of this study is to provide insights into the REE and Y behavior during garnet porphyroblast formation in staurolite-bearing schists as a constituent of Late Paleoproterozoic metapelites of the Ladoga Complex. The MnNCKFMASH P–T pseudosection for a single sample and Grt–Bt thermometry indicate that the garnet core grew at 520°C and under 7.0–7.2 kbar in the Grt–Bt–Pl–Chl–Ms–Zo field, whereas the garnet rim was equilibrated at 590–600°C and under 3.5–4.0 kbar. The measured zoning profiles are strongly depleted in REE + Y in the garnet core containing high Mn and Ca concentrations. The intermediate zone of garnet is enriched in La, Ce, Pr, and Nd (inner LREE + Nd annulus), as well as in Dy, Er, Yb, Lu, and Y (outer HREE + Y + Dy annulus). According to pseudosection analysis, these peaks were probably produced owing to breakdown of epidote-group minerals (allanite, REE-rich epidote) at T < 535°C and P > 6.5 kbar. Towards the rim, the HREE + Y contents gradually decrease, whereas MREE (Sm, Eu, Gd) display an inverse trend. The rim also exhibits a negative Eu anomaly. The former tendency reflects an increase in temperature during garnet crystallization and partitioning of elements between garnet and monazite. It is thought that the latter is linked to oppositely directed change in garnet-monazite partition coefficients for HREE and MREE with increasing temperature.  相似文献   

3.
前寒武纪沉积岩中自生独居石的发现及其意义   总被引：5，自引：1，他引：5  
由于受到葛家屯组中发现自生方铅矿的启发 ,首次于大连前寒武纪震旦系十三里台组泥岩中发现了自生独居石 ,这一发现为在中国北方前寒武纪沉积岩中寻找自生独居石提供了重要的线索。它为进一步探索 U、Th- Pb同位素测年拓展了新的研究领域和提供了可能性。本文列举了中国北方前寒武纪沉积岩中 Ce元素异常以及 REE较高的例证 ,认为上述地区都有可能发现自生独居石。同时介绍了最近又在北京十三陵中元古代的常州沟组和串岭沟组所发现自生独居石的新资料。研究表明 ,自生独居石的电子探针扫描形态 ,与岩浆岩、变质岩及砂矿中截然不同。在地质年代分布上 ,元古宙 REE相对丰度较高 ,特别是 L REE较高的泥质岩多数来自古陆壳上。资料对比结果显示 :在 L a+Ce+Nd、Yb+Y、Sm+Gd+Dy三角图中 ,北京十三陵元古宙泥质岩、大连震旦系十三里台组泥岩和辽南 -辽西中元古代泥质岩都属于近古陆的沉积类型。首次提出 ,中国北方元古宙沉积与南方震旦系磷块岩沉积环境存在明显的不同并反映在三角图中 ,前者离 L a+Ce+Nd端点近 ,而后者由于成因上属于洋流上升沉积物而远离该端点。按照大连震旦系十三里台组沉积环境特点 ,自生独居石应为生物成矿作用的产物 ,含矿物泥岩形成于总体氧化环境中的局部还原亚环境中。基于此 ,建立了  相似文献   

4.
Using an excimer (KrF) laser ablation ICP-MS system, we studied the distribution of REE in garnets from metapelites and metabasites from Ivrea-Verbano (Western Alps, Italy) and from the Peña Negra Anatectic Complex (Central Iberia), finding systematic variations that correlate well with the metamorphic grade. Chondrite-normalized REE patterns of garnets from amphibolite-grade metapelites have lower-than-chondrite levels from La to Sm, a very small or no Eu anomaly, and a steep rise in the abundance of heavy REE as the atomic number increases. Metapelitic garnets from the amphibolite-granulite transition have a marked Eu negative anomaly and are enriched in MREE such that Sm is 10-15 times chondrite and the pattern is almost flat from Dy to Yb-Lu. In garnets from granulite-grade metapelites, the intensity of the Eu anomaly and the relative concentration of Nd, Sm, Gd and Tb increase, with almost flat chondrite-normalized patterns from Sm to Lu. Garnets from mafic granulites are remarkably similar to those of metapelitic garnets equilibrated at the same pressure, except for the Eu anomaly. The apparent paradox of enhanced uptake of larger REE ions with increasing pressure is attributed to the 3M2+ 2REE3++ vacancy substitution, which produces a net decrease in the dimensions of the unit-cell of garnet. Variations in REE patterns depend essentially on the pressure and have little dependence on either temperature, bulk-composition of garnet, or REE whole-rock composition, so they could represent a new approach for geobarometric studies. The best numerical parameter to express pressure-related variations of REE distribution in garnets is the Gd/Dy ratio which does not seem perceptibly affected by disequilibrium partitioning. The regression equation between GASP pressure and the average Gd/Dygarnet is P = 3.6 + 5.6 Gd/Dy. This equation seems to be reliable for garnets: (1)equilibrated within a pressure range of 4-9 kbar, (2) coexisting with modal monazite; and (3) with unit-cell dimensions under 11.46 Å.  相似文献   

5.
A detailed survey of REE distribution in the xenotime and florencite paragenetic association from quartz veins of Au-REE mineral occurrences of the Nether-Polar Urals revealed maximum contents of Ce, Nd, Sm, Gd, Dy, and Y. Four of these elements form their own minerals: florencite-(Ce), -(Nd), and -(Sm) and xenotime-(Y) containing up to 25% Gd2O3. The compositions of the minerals are isomorphous mixtures of two different groups: Ybpg (Y, Ho, Er, Yb, Lu, Nd, and As) and Gdpg (Gd, Tb, Dy, Eu, and Sm) in xenotime and Lapg (La, Ce, Pr, Eu, and As) and Smpg (Nd, Sm, Gd, Sr, Ca, and S) in florencite. Both minerals display strong heterogeneities in the distribution of isomorphous components and two types of zoning, oscillatory and trend. The crystal cores are enriched in HREE. Variations in the composition of isomorphous mixtures are accompanied by a change in the dominant crystal forms of florencite. Redeposited varieties are distinguished by homogeneous composition, the absence of impurities, and weak correlations between elements. The REE fractionation is interpreted in terms of quantum mechanics.  相似文献   

6.
The rare-earth elements (REE) and yttrium have been determined in 37 international rock and mineral reference materials. Samples were prepared using conventional rock-dissolution techniques, and the REE and yttrium were separated from the other constituents using cation-exchange chromatography. The REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Lu) and yttrium were determined simultaneously by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Results for four well-characterised USGS standard rocks agree favourably with "recommended" values and with REE determinations made previously by workers using ICP-AES, isotope dilution mass spectrometry, instrumental neutron activaton analysis and X-ray fluorescence spectrometry.
Les éléments de terres rares (TR) et yttrium ont été dosés dans 37 échantillons internationaux de réféence. Les échantillons ont été décomposés par dissolution acide et les TR séparés par résine échangeuse de cations. Les TR (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Lu) et yttrium ont été dosés simultanément par la spectrométrie d'émission-plasma inductif. Les résultats obtenus pour quatre échantillons de référence bien charactérisés de I'USGS se comparent favorablement avec ceux obtenus par la spectrométrie d'émission-plasma, la dilution isotopique, I'activation neutronique et par la spectrométrie d'é fluorescence-X.  相似文献   

7.
The abundances of 29 elements, including nine REE (La, Ce, Nd, Sm, Eu, Tb, Dy, Yb and Lu), have been determined by instrumental neutron activation analysis in 33 tholeiitic basalts from Mauna Loa, Kohala, Mauna Kea, Lanai and Koolau. These data have been combined with data provided by A. V. Murali et al. on seven basalts from Kilauea for geochemical evaluation.Partial melting models based on the partitioning of the REE and Sc suggest that these basalts can be produced from three distinct source compositions. Thus, the basalts from Mauna Kea, Kohala and Kilauea are generated by 2–10% partial melting of similar source materials in the compositional range 82 ± 4% olivine plus orthopyroxene (ol + opx), 14 ± 3% clinopyroxene (cpx) and 4 ± 1% garnet (gar). Similar amounts of melting of source materials having 74 ± 6% ol + opx, 21 ± 5% cpx and 5 ± 1% gar produce the basalts of Mauna Loa and Lanai. A source material composed of 86 ± 4% ol + opx, 11 ± 2% cpx and 3 ± 1% gar is proposed for the generation of basalts from Koolau.The olivine-crystallization model suggested here requires absolute REE abundances in the preferred Mauna Kea, Kohala and Kilauea source to range from 1.1× (times chondrite) for the LREE (La) to about 1.3× for the HREE; in the Mauna Loa and Lanai source, La is about 1.0× and the HREE are about 1.6×; and in the Koolau source, La is ~0.7× and the HREE are ~0.9×.  相似文献   

8.
Rare earth elements(REE)include the lanthanide series elements(La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy.Ho,Er,Tm,Yb,and Lu)plus Sc and Y.Currently these metals have become very critical to several modern technologies ranging from cell phones and televisions to LED light bulbs and wind turbines.This article summarizes the occurrence of these metals in the Earth’s crust,their mineralogy,different types of deposits both on land and oceans from the standpoint of the new data with more examples from the Indian subcontinent.In addition to their utility to understand the formation of the major Earth reservoirs.multi-faceted updates on the applications of REE in agriculture and medicine including new emerging ones are presented.Environmental hazards including human health issues due to REE mining and large-scale dumping of e-waste containing significant concentrations of REE are summarized.New strategies for the future supply of REE including recent developments in the extraction of REE from coal fired ash and recycling from e-waste are presented.Recent developments in individual REE separation technologies in both metallurgical and recycling operations have been highlighted.An outline of the analytical methods for their precise and accurate determinations required in all these studies,such as,Xray fluorescence spectrometry(XRF),laser induced breakdown spectroscopy(LIBS),instrumental neutron activation analysis(INAA),inductively coupled plasma optical emission spectrometry(ICP-OES),glow discharge mass spectrometry(GD-MS),inductively coupled plasma mass spectrometry(including ICP-MS,ICP-TOF-MS,HR-ICP-MS with laser ablation as well as solution nebulization)and other instrumental techniques,in different types of materials are presented.  相似文献   

9.
ABSTRACT

Three kinds of multicomponent diffusion effects, arising from three distinct physical mechanisms, are evident in stranded diffusion profiles at the rims of partially resorbed garnets from the contact aureole of the Makhavinekh Lake Pluton, northern Labrador. Profiles that display a subtle maximum in Ca concentration are explained by the prevailing ideal mean-field theory of multicomponent diffusion, but models implementing that theory cannot replicate inverted profiles for Li and internal maxima for Nd, Sm, and Eu. The anomalous profiles are quantitatively reproduced, however, by numerical simulations employing a model based on coupled movement of charge-compensating groups during diffusional transport of yttrium and the rare-earth elements (Y+REEs). An alkali-type charge-compensation mechanism for the heterovalent substitution of Y+REEs on dodecahedral sites in garnet produces direct charge coupling between Li+ and (Y+REE)3+ and leads to co-diffusion of Li+-(Y+REE)3+ pairs, with the result that Li profiles closely mimic those for Y+REEs. A menzerite-type charge-compensation mechanism produces indirect charge coupling among all Y+REE components, with the result that the fluxes of low-abundance REEs become partly dependent on the fluxes of Y+REEs present in higher abundance. These findings have implications for the robustness of Li profiles in garnet as monitors of fluid–rock interaction, for geochronology based on the Sm–Nd and Lu–Hf systems, and for future experimental attempts to quantify rates of diffusion in garnet.  相似文献   

10.
An analysis of rare earth elements in various types of supergene phosphorites established the following sequence of increasing average total contents (ppm): phosphorite from Christmas Island in the Indian Ocean, 3.89; spelean coprolitic phosphorite, 21.98; phosphorite from the weathering zone of sedimentary rocks, 27.41; phosphorite from the weathering zone of endogenous rocks, 372.32; and lacustrine coprolitic phosphorite, 461.59. Supergene phosphorites, especially the most common among them from the weathering zone of sedimentary rocks, are significantly depleted relative to marine phosphorites both in average and maximum REE contents. The REE contents of supergene phosphorites are controlled by several factors, including the REE contents in the primary rocks affected by weathering, the physicochemical conditions of phosphorite formation, the presence of a biogenic component in the phosphatogenetic system, and the structural type of the phosphorites. There is a strong positive correlation within the group of light and, in part, middle REEs (La, Ce, Nd, Sm, and Eu) and between the heavy REEs Yb and Lu, whereas the correlation between these two groups is weaker or insignificant. Gd and Tb are well correlated with the elements of both groups.  相似文献   

11.
贵州织金含稀土磷矿床的Sm-Nd同位素年龄及其地质意义   总被引：1，自引：0，他引：1  
施春华  胡瑞忠 《地球科学》2008,33(2):205-209
为探讨贵州织金含稀土磷矿床的形成时间和成矿物源, 利用Sm-Nd同位素稀释法对该矿床磷块岩中6个小壳化石及胶磷矿样品进行了年龄测定.样品的质谱分析测试结果显示, 样品的147Sm/144Nd与143Nd/144Nd构成了一条相关性良好的线性等时线; 计算结果表明织金含稀土磷矿床具有533±22Ma的Sm-Nd等时年龄, εNd (t) 值为-2.44~-2.77, 表明它们具有相同的成因和相近的形成时代, 本次测得年龄代表着真实的成矿年龄; 二阶段Nd的模式年龄为1313~1338Ma.结合前人对该矿床稀土元素地球化学的研究成果表明, 织金含稀土磷矿床的成矿物源有新生地幔物质组分的加入.   相似文献   

12.
Partition coefficients (zircon/meltDM) for rare earth elements (REE) (La, Ce, Nd, Sm, Dy, Er and Yb) and other trace elements (Ba, Rb, B, Sr, Ti, Y and Nb) between zircon and melt have been calculated from secondary ion mass spectrometric (SIMS) analyses of zircon/melt inclusion pairs. The melt inclusion-mineral (MIM) technique shows that DREE increase in compatibility with increasing atomic number, similar to results of previous studies. However, DREE determined using the MIM technique are, in general, lower than previously reported values. Calculated DREE indicate that light REE with atomic numbers less than Sm are incompatible in zircon and become more incompatible with decreasing atomic number. This behavior is in contrast to most previously published results which indicate D > 1 and define a flat partitioning pattern for elements from La through Sm. The partition coefficients for the heavy REE determined using the MIM technique are lower than previously published results by factors of ≈15 to 20 but follow a similar trend. These differences are thought to reflect the effects of mineral and/or glass contaminants in samples from earlier studies which employed bulk analysis techniques.DREE determined using the MIM technique agree well with values predicted using the equations of Brice (1975), which are based on the size and elasticity of crystallographic sites. The presence of Ce4+ in the melt results in elevated DCe compared to neighboring REE due to the similar valence and size of Ce4+ and Zr4+. Predicted zircon/meltD values for Ce4+ and Ce3+ indicate that the Ce4+/Ce3+ ratios of the melt ranged from about 10−3 to 10−2. Partition coefficients for other trace elements determined in this study increase in compatibility in the order Ba < Rb < B < Sr < Ti < Y < Nb, with Ba, Rb, B and Sr showing incompatible behavior (DM < 1.0), and Ti, Y and Nb showing compatible behavior (DM > 1.0).The effect of partition coefficients on melt evolution during petrogenetic modeling was examined using partition coefficients determined in this study and compared to trends obtained using published partition coefficients. The lower DREE determined in this study result in smaller REE bulk distribution coefficients, for a given mineral assemblage, compared to those calculated using previously reported values. As an example, fractional crystallization of an assemblage composed of 35% hornblende, 64.5% plagioclase and 0.5% zircon produces a melt that becomes increasingly more enriched in Yb using the DYb from this study. Using DYb from Fujimaki (1986) results in a melt that becomes progressively depleted in Yb during crystallization.  相似文献   

13.
Rare earth element (REE) and yttrium concentrations of coexisting monazite and xenotime were determined from a suite of seven metapelites from the Variscan fold belt in NE Bavaria, Germany. The metapelites include a continuous prograde, mainly low-P (3–5 kbar) metamorphic profile from greenschist (c. 400 °C) to lower granulite facies conditions (c. 700 °C). The LREE (La–Sm) are incorporated preferentially in monoclinic monazite (REO9 polyhedron), whereas the HREE plus Y are concentrated in tetragonal xenotime (REO8 polyhedron). The major element concentrations of both phases in all rocks are very similar and do not depend on metamorphic grade. Monazite consists mainly of La, Ce and Nd (La0.20–0.23, Ce0.41–0.45, Nd0.15–0.18)PO4, all other elements are below 6 mol%. Likewise, xenotime consists mainly of YPO4 with some Dy and Gd solid solutions (Y0.76–0.80, Dy0.05–0.07, Gd0.04–0.06). In contrast, the minor HREE concentrations in monazite increase strongly with increasing metamorphic grade: Y, Dy and Gd increase by a factor of 3–5 from greenschist to granulite facies rocks. Monazite crystals often show zonation with cores low in HREE and rims high in HREE that is interpreted as growth zonation attained during prograde metamorphism. Similarly, Sm and Nd in xenotimes increase by a factor of 3–4 with increasing metamorphic grade. Prograde zonation in single crystals of xenotime was not observed. The XHREE+Y in monazite and XLREE in xenotime of the seven rocks define two limbs along the strongly asymmetric miscibility gap from c. 400 °C to 700 °C. The empirical calibration of the monazite miscibility gap limb coexisting with xenotime is appropriate for geothermometry. Due to its contents of U and Th, monazite has often been used for U–Pb age determination. The combination of our empirical thermometer on prograde zoned monazite along with possible age determination of zoned single crystals may provide information about prograde branches of temperature–time paths.  相似文献   

14.

By means of X-ray fluorescence with synchroton radiation (XRF-SR), the contents of all 14 rare-earth elements (REEs) and that of Y were determined in 12 monazite samples from different veins in the Ilmen’ Reserve (South Urals). It was found that, in anphibole-micaceous-carbonate mineralized zones within metabasites, monazites were pronouncedly depleted in middle and, especially, in heavy rare-earth elements (HREEs) (from 0.25% and below for Sm, 0.08% or below for Gd, 0.03% for Dy, 0.01% for Er and Tm, below 0.005% for Yb, trace amounts of other odd HREEs, at a Y content of 0.1% or below). Monazites from the veins of granitic pegmatites were characterized by vastly decreased La contents (4–8 compared to 11–13% for the group above), at high values for Pr (to 3%), Nd (to 8%), Sm (to 1.3%), Gd (to 1.1%), Dy (to 0.9%), Er (to 0.2%), Yb (to 0.05%), and Y (from 0.2 to 1.7%). Here, the values for odd REEs are also quite high compared to the group above (to 0.2% for Tb, to 0.08% for Ho, and to 0.1% for Tm).

  相似文献   

15.
《Applied Geochemistry》2001,16(2):231-244
Standard reference water samples (SRWS) were collected from two mine sites, one near Ophir, CO, USA and the other near Redding, CA, USA. The samples were filtered, preserved, and analyzed for rare earth element (REE) concentrations (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) by inductively coupled plasma-mass spectrometry (ICP-MS). These two samples were acid mine waters with elevated concentrations of REEs (0.45–161 μg/l). Seventeen international laboratories participated in a ‘round-robin’ chemical analysis program, which made it possible to evaluate the data by robust statistical procedures that are insensitive to outliers. The resulting most probable values are reported. Ten to 15 of the participants also reported values for Ba, Y, and Sc. Field parameters, major ion, and other trace element concentrations, not subject to statistical evaluation, are provided.  相似文献   

16.
We present data for the concentrations of eleven rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu) in eleven international geochemical reference materials obtained by isotope dilution multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We have analysed both rock powders and synthetic silicate glasses, and the latter provide precise data to support the use of these as reference materials for in situ trace element determination techniques. Our data also provide precise measurements of the abundance of mono-isotopic Pr in both glasses and powders, which allows more accurate constraints on the anomalous redox-related behaviour of Ce during geochemical processes. All materials were analysed in replicate providing data that typically reproduce to better than one percent. Sm/Nd ratios in all these materials also reproduce to better than 0.2% and are accurate to < 0.2% and can thus be used as calibrants for Sm-Nd geochronology. Our analyses agree well with existing data on these reference materials. In particular, for NIST SRM 610, USGS BHVO-2, AGV-1 and AGV-2, our measured REE abundances are typically within < 2% (and mostly 1%) of REE concentrations previously determined by isotope dilution analysis and thermal ionisation mass spectrometry, consistent with the higher degree of precision and accuracy obtained from isotope dilution techniques. Close agreement of results between basaltic glass reference materials USGS BHVO-2G and BCR-2G and the BHVO-2 and BCR-2 powders from which they were created suggests that little fractionation, concentration or dilution of REE contents occurred during glass manufacture.  相似文献   

17.
北京怀柔崎峰茶-得田沟金矿田稀土元素地球化学特征   总被引：2，自引：0，他引：2  
崎峰茶-得田沟金矿田位于华北地块东北部,是华北地块北缘巨型EW向金矿带的组成部分。本文研究了该矿田各类岩石的稀土元素特征。通过与含金石英脉和金属硫化物的对比分析,探讨了它们与成矿的关系。结果显示,金属硫化物、含金石英脉及蚀变岩石的稀土元素特征很相似,它们与矿田内的燕山期正长斑岩脉和花岗岩(脉)具有很大相似性,从而确定了它们之间的成因联系,为找矿预测提供了依据。   相似文献   

18.
Three groups of industrial uranium deposits that differ in the distribution of lanthanides in U oxides have been recognized. A dependence of the REE distribution type on the Yttrium content and Yttrium index YI = (La + Ce)/Y that controls the formation of REE phases capable of selective accumulation of lanthanides has been discovered. This indicates the important role of crystal–chemical fractionation in the distribution of lanthanides. Preferable accumulation of Sm–Gd by U oxides has been found to occur at relatively low contents of Y. In Proterozoic uranium deposits, the yttrium specialization of oxides predominates, while in most Phanerozoic deposits the lanthanum–cerium specialization is typical. These results extend the possibilities of using REEs in ores for purposes of study of the genesis of various uranium deposits.  相似文献   

19.
华南花岗岩风化壳中稀土元素地球化学及矿石性质研究   总被引：27，自引：2，他引：27  
池汝安  徐景明 《地球化学》1995,24(3):261-269
华南稀土花岗岩风化壳主要可分为腐值层、全风化层和半风化层。在岩石的风化淋滤过程中，稀土以水合或羟基水合离子吸附在全风化层中的主要矿物埃洛石和高岭石等粘土矿物上。这些层状粘土矿物具有取代结构和断面余键两个吸附活性中心。量子化学计算表明两个吸附活性中心对不同稀土的吸附能力为：Ｌａ＾３＋〉Ｃｅ＾３＋〉Ｐｒ＾３＋〉Ｎｄ＾３＋〉Ｓｍ＾３＋〉Ｅｕ＾３＋〉Ｇｄ＾３＋〉Ｔｂ＾３＋〉Ｄｙ＾３＋〉Ｈｏ＾３＋〉Ｙ＾３＋  相似文献   

20.
The development is described of a mixed-solvent ion-exchange technique for separating trace amounts of rare-earth elements from silicate rocks and minerals. A two-column method is used, bulk separation of rare earths from other elements being accomplished on the first, and separation into three groups for mass-spectrometric analysis on the second. This has been applied to the determination of nine REE (La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb) in standard rock samples. Smooth variation of the chondrite-normalized abundance distributions and comparison with other published results indicate that the accuracy of the method, with the exception of La, is generally ± 2%.  相似文献   

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