Geochemical characterization of rare earth elements in sediment profiles from the Oualida lagoon(Morocco)

The present work assesses the temporal distribution pattern and geochemical changes of rare earth elements and Yttrium, Scandium, Thorium, and Uranium delivery into the Oualidia lagoon. Two sediment cores were retrieved from the Oualidia lagoon and analyzed using neutron activation analysis. The results indicated that heavy rare earth elements are slightly enriched the sediment cores over light rare earth elements. The highest values of REEs were recorded in the top layers of the cores and depleted with depth, suggesting a possible change in factors controlling their accumulation, including mechanical, chemical, and environmental parameters such as weathering intensity, grain size, and Fe-Mn oxides. The sediments display positive Ce anomalies, which are probably related to the submarine weathering process and detrital input. Noting also the variation of hydrodynamics conditions and confinement of the upstream part of the lagoon played a key role in changing the sediment origins.Thus, further investigation of REEs origin in the Oualidia lagoon sediment is required to identify their sources,provenances, and the factors controlling their spatial and vertical distributions. However, these results provide baseline data of occurring changes in REEs geochemical composition and constitute a typical study case to understand the link between sedimentary and geochemistry processes in a lagoonal ecosystem.

Geochemical characteristics of rare earth elements in Wuhan section of the Yangtze River

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Geochemical Characteristics of Rare Earth Elements in Guposhan Granite Complex and Their Petrogenetic Implication

In this paper the geochemical characteristics of rare earth elements in Guposhan granite complex in Nanling Area,South China,is systematically studied,and the balance of REE distribution in rock-forming minerals, which contain only 21.47～29.71 wt% of total REE in granites,is calculated.The petrogenetic relationship be- tween three different stages of the granites in the complex is discussed,and a geochemical model is suggested for the formation of granitic magma in early stage by partial melting of the crustal basement rocks containing more REE than that in the late stage.It shows that a ion-adsorption type of REE deposit could ocuur in the weath- ering crust on the early stage granite.Rb-Sr isotope isochron dating of the first stage medium-coarse-grained K-feldspar granite shows that its age is 146.5 Ma and initial ^(87)Sr/^(86)Sr ratio is 0.71198.

Geochemical signatures and human health risk evaluation of rare earth elements in soils and plants of the northeastern Qinghai-Tibet Plateau,China

Information on rare earth elements(REEs)in soils and plants of the Qinghai-Tibet Plateau is very limited.Therefore,in this study,we performed field sampling to explore the geochemical signatures and human health risk of REEs in soils and plants of the northeastern Qinghai-Tibet Plateau,China.A total of 127 soil samples and 127 plant samples were collected from the northeastern Qinghai-Tibet Plateau to acquire the geochemical signatures and related human health risks of REEs.The mean total concentrations of REEs in soils and plants of the study area reached 178.55 and 10.06 mg/kg,respectively.The light REEs in soils and plants accounted for 76%and 77%of the total REEs,respectively.REEs showed significantly homogenous distribution in soils but inhomogeneous distribution in plants of the study area.Characteristic parameters indicated that light REEs were enriched and fractionated significantly,while heavy REEs were moderately fractionated in soils and plants.REEs in soils and plants showed significantly negative Europium anomaly.Cerium showed slightly positive anomaly in plants and slight anomaly in soils.The normalized distribution patterns of REEs were generally similar in the analyzed soils and the corresponding plants of the study area.The average bio-concentration factor of REEs ranged from 0.0478(Scandium)to 0.0604(Europium),confirming a small accumulation of REEs by plants.Health risks caused by REEs in soils and plants were negligible,while risks for adults were lower than those for children.This study provides important information on REEs in soils and plants of the northeastern Qinghai-Tibet Plateau.

Content Characteristics of Rare Earth Elements in Stone Coal and Parting in Southern Shaanxi, China

Stone coal is a special resource, because it is associated with a variety of rare metal elements. The elemental geochemical characteristics of stone coal can provide useful information for the study of its formation and evolution history. The content of rare earth elements in stone coal has been the focus of attention. Stone coal is widely distributed in southern Shaanxi province of China. In order to study the content and distribution of rare earth elements in stone coal, and provide a plan for the comprehensive development and utilization of stone coal, this study tested the rare earth elements content of stone coal, parting and coal ash samples, respectively, compared the content of rare earth elements in stone coal, parting, coal ash with the mean value of China coal, the mean value of world coal and the abundance value of upper crust, and discussed the features of rare earth elements content in different types of samples in southern Shaanxi province of China. The average contents of rare earth elements in the samples of stone coal, parting and coal ash were calculated, and the enrichment coefficients of the samples with the mean value of China coal, the mean value of world coal and the abundance value of upper crust were listed. The distribution rules and characteristics of the contents of rare earth elements in different types of samples in southern Shaanxi province of China were summarized.

Fractionation characteristics of rare earth elements(REEs) linked with secondary Fe, Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements(REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs(La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs(LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs(HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs.The substantial fractions of REEs in soils extracted byoxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile(10 %–30 %), which were similar to the mass fraction of Fe(10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.

Geochemical Properties and StratigraphicalCorrelation of Frasnian-Famennian TransitionalStrata in Wuzhishan Section

The qualities of petrology and paleobiology in Wuzhishan Section are studied. Several geo-chemical anomalies are recognized, such as: high rare earth element content, high pyrite content and Ni anomalies. It could be correlated with Nandong Section in Xiangzhou County and the F/F boundary could be determined according to Ni anomalies. The results of the study indicate that the geochemical anomaly plays an important role in stratigraphic correlation in non-fossil stratum.

Geochemistry of rare earth elements and yttrium in Late Permian coals from the Zhongliangshan coalfield, southwestern China

Rare earth elements and yttrium(REY)in coal deposits are considered promising alternative sources for these resources owing to their increasing global demand.This paper reports the geochemical characteristics of REY in the Late Permian coals from an underground K1a seam section of the Zhongliangshan coalfield in Chongqing,southwestern China.The mineralogy,degree of enrichment,distribution patterns,modes of occurrence,and sediment origin of REY were investigated.Compared with the average of world coals,the concentration of REY in the K1a coals were normal,dominated by light REY(LREY),with less medium and heavy REY(MREY,HREY).The fractionation degree of the MREY and HREY are higher than that of LREY in most K1a coal samples,deduced from the mixed enrichment type of REY,mainly including M-H-type,and a few L-M type and H-type.In addition,the combination of anomalies of Ce,Eu,Gd,and Al_(2)O_(3)/TiO_(2) parameters,the terrigenous materials in the K1a coal were derived from the felsic-intermediate rocks at the top of the Emeishan basalt sequence,and the samples were affected by seawater intrusion during early peat accumulation.Although the minerals primarily consist of kaolinite,illite,pyrite,and small amounts of quartz,calcite and anatase,REY are correlated with ash yield,SiO2,and Al_(2)O_(3),revealing that the REY mainly occur in aluminosilicate minerals,especially kaolinite and illite.Meanwhile,REY positively relate to P_(2)O_(5) and Zr,which may exist in phosphate-containing minerals or zircon.Furthermore,most samples in the K1a coal or ash do not reach the cut-off grade for the beneficial recovery of REY.With the exception of central Guizhou,southwestern Chongqing,and the junction of western Guizhou and northeastern Yunnan,the REY content in coals from southwestern China are high,and its by-products are suitable as potential REY sources.

云南勐海地区1∶5万水系沉积物地球化学特征及找矿预测

勐海地区处于临沧-勐海(岩浆弧)Fe-Pb-Zn-Au-Ag-Sn-Sb-Ge-REE矿带,具有较好的找矿前景.在勐海地区1∶5万水系沉积物测量基础上,对区内29种元素分布特征、元素相关性、地球化学参数特征研究,圈定了5个组合异常和13个综合异常.其中,Ce-La-Y-Zr综合异常具有较好找矿前景;Au、As、Sb、Hg、W、P等元素离散程度较高,元素局部较富集,具有成矿的可能性.结合水系沉积物测量成果,圈定找矿远景区2处,为下一步找矿工作提供了地球化学依据.

江西全南县青龙山萤石矿稀土元素地球化学特征及成因分析

本文旨在对江西省全南县青龙山萤石矿床的地球化学特征及成因进行探讨,通过对青龙山萤石矿区矿石和围岩样品进行稀土元素分析,青龙山萤石矿矿石的∑REE平均含量为88.186×10^(-6),δEu为0.23~0.61,δCe为0.78~0.91;围岩的∑REE平均含量为184.52×10^(-6),δEu为0.31~0.69,δCe为0.85~1,萤石矿石和围岩的稀土元素配分模式具有相似性和同步性,呈轻稀土相对富集的右倾型,Eu中等亏损,Ce弱亏损。矿石与围岩的稀土地球化学研究显示,该萤石矿床至少存在两个成矿期次,为岩浆热液成矿,成矿环境为稳定的较还原条件,成矿流体温度在200℃左右。

土壤稀土元素对郧西县核桃矿质元素含量的影响探讨

为研究郧西县典型核桃种植区土壤稀土元素地球化学特征,在连片种植区内共采集20组土壤及果实样品,分析了土壤REE组成特征、配分模式及参数特征,并探讨了土壤稀土元素对核桃果实中主要矿质营养元素的影响。结果表明:研究区土壤中稀土元素平均值为141.86 mg/kg,低于湖北省A层土壤REE背景值。研究区内所有采样点配分模式曲线呈现出右倾的轻稀土富集模式,土壤中表现出较为明显的Eu负异常和较为微弱的Ce负异常。土壤稀土元素与果实中N、K、Ca、Zn、Cu、Mn、Sr、Ni、Mo、Cd、Co等元素具有显著正相关性,与果实中As、Pb具有显著负相关性。

GENESIS OF THE ALKALI-RICH PORPHYRIES IN YUNNAN

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Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

This study presents new major,trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types(siliceous,red clay and their transition zone)in the Central Indian Ocean Basin(CIOB)to address their genetic aspects,classification,growth rate,nature of host sediments and influence of REE in the processes of nodule formation.The nodules from CIOB are mostly either hydrogenetic(metals coming from oxygenated bottom water)and diagenetic(metals coming from suboxic sediment pore water)or a combination of both,depending on the source of supply of metal.However,a number of biogeochemical processes mediate this supply of metals which again changes from time to time,making the nodule growth process highly dynamic.This study suggests that at the initial stage of nodule growth,host sediments do not play much role in controlling the growth processes for which REEs can enter both Mn and Fe oxyhydroxide phases equally.Thus,the bottom water signature is imprinted in these early formed nodules irrespective of their host sediment substrate but with gradual growth and burial in the sediment,the main mode of metal enrichment becomes diagenetic through sediment pore water.This tends to increase the concentration of Mn,Ni and Cu over other elements which are retained in the sediment fraction.Among the REEs,Ce concentration of the nodules shows significant positive anomaly due to variation in redox potential and hence its magnitude can be used to get an idea about the metal enrichment procedure and the genetic type of the nodules.However,based on host sediment only,not much difference is found in the magnitude of Ce anomaly in these nodules.On the other hand,discrimination diagram,based on HFSE and REY chemistry,indicates that most of these nodules are of diagenetic origin under oxic condition with a trend towards hydrogenetic field.Further,the genetic type of the ferromanganese nodules from the CIOB are more effectively differentiated by a combination of their major and trace element concentrations rather than solely based on their REE or HFSE chemistry or host sediment substrate.

氟化铵快速分解-电感耦合等离子体质谱法测定地球化学样品中的稀土元素

测定地球化学样品中的微量稀土元素常用混酸分解法或碱熔融法,这些常规方法往往存在耗费试剂量多、基体效应大、操作周期长等缺点。采用氟化铵作熔剂,在旋盖聚四氟乙烯坩埚中220℃熔融样品后,采用2 mL硝酸和0.5 mL高氯酸+硫酸(1+1)在电热板上继续分解,建立了氟化铵分解-电感耦合等离子体质谱法测定岩石、土壤和水系沉积物中15种微量稀土元素的分析方法。方法能快速、有效地分解样品,经三种国家标准物质验证(岩石、土壤、水系沉积物),方法的准确度Δlgc在0.001~0.02,测定值与认定值相符。方法检出限为0.001~0.04μg/g,精密度RSD在1.1%~4.9%,能够满足微量稀土元素的分析要求,方法简单快捷、消耗试剂少、检出限低、精密度与准确度好等特点,适合于地球化学等地质样品微量稀土元素的批量快速分析测定。

稀土、铌在碳酸岩-碱性岩体系中的地球化学行为

稀土、铌是对战略性新兴产业至关重要的关键金属。碳酸岩-碱性岩型是极为重要的稀土、铌成矿类型,其成矿机制一直存在争议,主要在于碳酸岩-碱性岩体系中REE、Nb元素的地球化学性质和行为尚不清楚。本文系统综述了全球碳酸岩-碱性岩型稀土、铌资源的基本情况和分布格局、碳酸岩-碱性岩的成因与成矿机制、REE和Nb元素在碳酸岩-碱性岩体系中的地球化学行为等研究进展,并对碳酸岩-碱性岩成因不明、REE和Nb元素富集沉淀机制不清、元素分配行为不明确、络合物结构和稳定性缺乏实验研究等目前存在的问题进行了梳理。本文旨在通过系统总结碳酸岩-碱性岩体系REE、Nb的超常富集机制和碳酸岩-碱性岩体系稀土、铌成矿理论,为强化我国稀土资源优势,缓解铌资源被“卡脖子”困局提供理论支撑。

豫西南地区胡老庄萤石矿稀土元素地球化学特征及其地质意义

胡老庄萤石矿位于豫西南萤石成矿带内,成矿地质条件优越。本文通过矿床稀土元素地球化学研究,探讨该矿床成矿等方面的问题。研究发现:所有矿石和围岩样品球粒陨石标准化配分模式均具有相同的变化趋势,两者具有相同的物质来源,暗示成矿流体对花岗岩进行了淋滤和萃取,萤石中的稀土特征继承了围岩的稀土特征;萤石样品的δEu和δCe均具有中等到弱的负异常,表明矿床在沉淀时成矿流体处于还原环境,且结晶温度较低(200~250℃),成矿物质主要来源于地壳且有部分地表流体淋滤风化花岗岩中的成矿物质参与成矿;萤石矿Y/Ho-La/Ho关系图显示,萤石矿石的样品主要呈现出近水平分布区,部分样品表现出负相关特征,表明区内萤石矿主要以重结晶作用为主兼有少部分元素迁移形式形成。

板集煤矿地下水稀土元素地球化学特征

稀土元素具有稳定且相似的地球化学性质,被广泛用于研究地下水体与含水层之间的相互作用和地球化学过程。以淮南煤田板集煤矿为研究区,采集了砂岩水、太灰水和采空区混合水等地下水样,并对这些水样的稀土元素含量和常规水化学离子进行了测试分析,以研究矿区地下水的水化学特征、稀土元素含量分布特征以及相关控制因素等方面的内容。研究结果表明:矿区地下水中的Na^(+)+K+、Cl^(-)、HCO_(3)-平均质量浓度分别为669.1、820.3、344.0 mg/L,水质类型主要为Cl-Na、Cl·HCO_(3)-Na、HCO_(3)-Na型。研究区地下水中的稀土元素含量总体处于较低的浓度范围,其中三个混合水样中出现了重稀土的富集现象,大部分水样则呈现轻稀土富集。其中,Eu的含量最高,这是由于Eu与钙矿物的结晶沉淀作用导致其从稀土元素中分离出来。通过相关性冗余分析发现,研究区地下水样中的Eu和Fe存在一定的线性关系,说明Fe氧化物与稀土元素的吸附作用是影响稀土元素含量的重要控制因素之一。本研究对于深入了解淮南煤田板集煤矿地下水体系中的地球化学过程具体重要意义,并为矿区地下水的评价和管理提供了科学依据。

豫西晚二叠世煤中稀土元素地球化学特征及指示意义

随着稀土金属在医疗、新材料等高科技领域的广泛应用,其战略地位不断提升。为了探究豫西晚二叠世煤中稀土元素的富集程度、赋存状态以及沉积环境,以河南西部慧祥矿区二_(1)煤的20个煤分层样品为主要研究对象,运用电感耦合等离子质谱仪(ICP-MS)、X射线荧光光谱(XRF)的方法对研究区煤分层样品中稀土元素与常量元素进行测试,探讨了研究区煤中稀土元素的含量特征和富集程度;利用相关性分析和特征参数对样品中稀土元素的赋存状态以及沉积环境进行探讨。结果表明:慧祥矿区二_(1)煤中,稀土元素的质量浓度为35.29~133.61μg/g,平均浓度为79.14μg/g,略高于世界煤中稀土元素的平均浓度,但明显低于中国煤中稀土元素的平均浓度,稀土元素含量偏低,且以轻稀土富集为主;慧祥矿区二_(1)煤中稀土元素与灰分(Ad)以及SiO_(2)、Al_(2)O_(3)等主要氧化物呈现明显的正相关,表明稀土元素主要赋存于黏土矿物中;研究区样品中Ce元素和Eu元素负异常,(Gd/Gd)_(N)^(*)的轻微正异常,说明研究区主要受陆源的影响,成煤环境为弱酸性的还原环境。

赛马碱性岩稀有稀土矿地质化学特征及找矿潜力

赛马碱性岩是一个十分独特而复杂的地质体,以其岩石类型多样,矿物种类繁多,富含铀、钍、稀有稀土元素而闻名。本研究通过对赛马碱性岩地区近几年地质勘查项目成果的分析总结,发现赛马碱性岩第二侵入期岩石普遍存在稀有稀土元素矿化,成矿温度为中—低温,矿床类型主要分为残浆交代型和矽卡岩型两种,同时结合1∶20万水系沉积物测量数据和1∶1万原生晕测量数据,对整个碱性杂岩体进行了找矿潜力分析,在赛马碱性岩及其外围圈定出3个成矿预测区:赛马—顾家稀有稀土及放射性元素成矿预测区、爱阳稀有稀土及放射性元素成矿预测区、双山子稀土矿成矿预测区。该研究对赛马碱性岩地区的稀有稀土多金属找矿具有重要意义。

激光诱导击穿光谱结合RFE-GBDT算法定量分析稀土矿石中的Fe和Y

稀土矿组成复杂,对选矿技术要求较高,寻找一种快速检测分析稀土矿石中元素的方法对稀土矿选矿具有重要意义。激光诱导击穿光谱(Laser-induced Breakdown Spectroscopy, LIBS)是检测稀土矿石中元素的一种重要手段,可以进行现场分析,无需制备复杂样品。建立了一种基于LIBS结合递归特征消除(Recursive Feature Elimination, RFE)和梯度提升树(Gradient Boosting Decision Tree, GBDT)算法的模型对稀土矿石中Fe元素和Y元素进行快速定量分析。采用激光诱导击穿光谱仪对25个样品进行光谱采集,将采集的光谱进行预处理后使用5折交叉验证对RFE阈值进行优化,再通过贝叶斯搜索对GBDT模型参数进行优化,构建了RFE-GBDT校正模型,对稀土矿石中的Fe和Y进行了定量分析并与真实值进行对比,结果表明,Fe和Y的预测决定系数(RP2)分别为0.957 1和0.930 7,预测均方根误差(RMSEP)分别为0.072 7和0.022 6,说明该模型具有良好的预测性能,可以实现稀土矿石中Fe和Y的快速定量分析。