本期文章导读

正01铌钽元素分析技术新进展作者:李刚,姚玉玲,李婧祎,赵朝辉,罗涛,李崇瑛导读撰文:本刊编辑部近年来,从有关铌、钽元素测定的能力验证和实验室间协作实验数据统计情况来看,与其他元素比较,铌钽测试数据离散明显,钽的分析结果容易出现偏低现象,究其原因,主要是对铌钽的分析特性认识不够全面,样品前处理方法选择不合理,以及对测定方法的实验条件把握存在较大问题。当前,铌钽元素分析     

5-Br-PADAP二波长联合分光光度法同时测定矿石中铌和钽

铌、钽的显色剂很多,但由于两元素性质相近,常互相干扰,特效的光度测定方法却不多,能同时测定的更少。 5-Br-PADAP近年已成功地用于测定铌,测钽时则无法消除铌的干扰,有人     

5-Br-PADAP二波长联合分光光度法同时测定矿石中铌和钽

铌、钽的显色剂很多,但由于两元素性质相近,常互相干扰,特效的光度测定方法却不多,能同时测定的更少。 5—Br—PADAP近年已成功地用于测定铌,测钽时则无法消除铌的干扰,有人     

离子交换快速分离—ICP—AES测定岩石和水系沉积物中痕量钽和铌

铌钽矿物样品经氢氟酸—硫酸分解,可以用ICP-AES直接测定试液中的铌、钽及其它元素。痕量铌可用ICP-AES直接测定,但在某些岩石和水系沉积物中钽的含量往往甚微,(1ppm左右),ICP的灵敏度不够,某些基体元素干扰又较大,因此直接测定痕量钽有困难。 秦光荣等人曾提出过在稀盐酸-酒石酸溶液中,用阳离子交换树脂柱使铌钽与其它元素分离,但流出液体积较大。本文研究了一种快速离子交换分离的新方法。样品经碱溶、浸取、过滤,沉淀及滤     

铌钽元素分析技术新进展

铌钽是发展新兴产业所需的功能性和结构性材料,铌钽矿产是国家重点支持的战略新兴矿产资源,开展相关物料中铌钽的分析技术研究具有重要意义。由于铌和钽的物理化学性质十分相似,彼此难以分离,且易水解,加之地质样品分解困难,因此铌和钽的分析测试一直困扰着分析工作者。本文重点对铌钽元素分析中的样品前处理技术和现代分析测试技术进行综述。样品前处理是铌钽分析的关键环节,结合分析方法和样品特性,选择合理的样品分解和分离富集方法是准确测定铌钽的前提。仪器分析是现代分析测试技术的主流,电感耦合等离子体发射光谱/质谱法(ICP-OES/MS)是目前测定铌钽应用最多的方法,需要解决共存组分的干扰、基体效应和盐类影响等问题。激光剥蚀(LA)技术、X射线荧光光谱法(XRF)和中子活化分析法(NAA)采用固体进样,避免了前期样品处理的繁琐步骤和杂质的引入,是铌钽元素分析发展的方向。     

“孪生元素”铌-钽的地球化学特性和研究进展

因为具有相同的离子电价（+5）及相似的离子半径（~0.064 nm）,铌和钽是地球化学性质非常相似的一对"孪生"元素.作为高场强元素,Nb-Ta通常赋存在金红石、角闪石、铌-钽矿、榍石和云母等矿物中.近20年来特别是21世纪初,Nb、Ta一直是地球化学领域的一个热点,大量的研究关注不同铌-钽矿物的赋存状态、矿物和岩石中铌-钽含量和铌/钽比值、铌-钽矿物与熔/流体之间的元素分配的实验岩石学研究和铌-钽分异的机制及具体地质过程.研究Nb、Ta具有重要的科学意义,涉及到整个地球的元素平衡、大陆地壳的生长机制、含金红石岩石的形成源区等.本文综合了近20年来铌、钽的研究内容,系统地总结了铌、钽在地球化学研究中各方面已经取得的成果,同时展望了未来铌-钽这对高场强元素对在地球科学研究中的潜在应用.      

密闭酸溶-电感耦合等离子体发射光谱/质谱法测定花岗伟晶岩中32种微量元素

花岗伟晶岩富集锂铍铷铯铌钽等稀有金属元素,准确测定其中的大离子亲石元素、高场强元素和稀土等微量元素,可用于判断成矿流体物质来源、成岩构造环境。目前的测试方法研究主要集中在锂铍铷铯铌钽等少数元素,样品消解方法有四酸敞开法、五酸敞开法、密闭酸溶法等,存在难溶矿物分解不完全、锆铪钍铀和稀土等元素回收率偏低等问题。本文对比了盐酸-硝酸-氢氟酸-高氯酸敞开消解法、盐酸-硝酸-氢氟酸-高氯酸-硫酸敞开消解法、硝酸-氢氟酸密闭消解法三种方法的分解效果。结果表明：四酸消解法中,铌钽锆铪钨和重稀土元素结果严重偏低;五酸消解法由于采用硫酸-氢氟酸-过氧化氢体系提取,有效地防止了铌钽的水解,铌钽钨等元素测定结果准确,但锆铪钡铅和轻稀土元素测定结果偏低。硝酸-氢氟酸密闭消解法使用王水代替硝酸进行残渣复溶,促进了铌钽锆铪和稀土等元素的复溶,采用电感耦合等离子体发射光谱和质谱法(ICP-OES/MS)可以准确测定花岗伟晶岩中稀有金属、稀土元素等32种元素,方法检出限为0.004～2.50μg/g,精密度(RSD,n=12)为1.0%～8.3%。将该方法应用于8种花岗岩、伟晶岩及稀有金属矿标准物质和三种类型实际样品...     

铌钽酸盐类矿物微量化学分析

针对复杂铌钽酸盐单矿物微量化学分析研究,本文确定以8N盐酸—2％草酸为试样溶液的稳定介质。为了有效地利用微量试样,选用BPHA(N—苯甲酰苯胲)和PMBP(1—苯基—3—甲基4—苯甲酰吡唑酮—5)为二个组试剂,建立一个合理萃取系统,使铌、钽、锆、钛、铁、钨、钍、铀、希土元素、铅、铝、钙、镁,锰等14个元素     

等离子体发射光谱法同时测定岩石中微量锆、铪、铌和钽等元素

本文介绍了一种快速离子交换分离—ICP-AES法同时测定岩石中微量锆、铪、铌和钽等元素的新方法。样品经碱熔、浸取、过滤,其沉淀连同滤纸放回原烧杯,加入H~+型阳离子交换树脂和少量酒石酸溶液。基体元素(Fe~(3+),Al~(3+),Ca~(2+),Mg~(2+)等)被树脂吸附,锆、铪、铌和钽与酒石酸形成稳定络合物存留在溶液中,经干过滤后,用ICP-AES方法直接测定。欲测元素的样品分析实际检出限分别为:Zr0.2ppm。Hf、Nb、Ta均为0.4ppm。实践证明,本方法不仅步骤简单,分析速度快,而且分析结果或靠,精密度和准确度良好。     

阿尔泰成矿带中蒙边界地区稀有元素铌和钽区域地球化学特征

铌和钽是高科技不可或缺的稀有金属材料,阿尔泰是重要的稀有金属成矿带,开展阿尔泰成矿带铌和钽资源远景优选至关重要。收集了中蒙边界1∶100万铌和钽地球化学数据,探讨其在不同构造单元内的背景值及区域地球化学异常特征。全区铌、钽元素中位值和平均值分别是1380×10-6和1493×10-6、111×10-6和131×10-6,中国境内铌元素中位值(1219×10-6)和平均值(1331×10-6)分别低于蒙古国境内铌元素中位值(1490×10-6)和平均值(1639×10-6);相应地,中国境内钽元素中位值(102×10-6)和平均值(120×10-6)也分别低于蒙古国境内钽元素中位值(120×10-6)和平均值(141×10-6);对于划分的构造单元而言,戈壁阿尔泰弧盆系、阿尔泰南缘弧盆系和阿尔泰构造带铌、钽元素的中位值和平均值分别高于全区中位值和平均值,是铌、钽元素的富集区,且产出大量稀有金属矿床;根据85%累积频率,圈定出13个铌异常区并优选出7个铌地球化学省,同时圈定出13个钽异常区并优选出10个钽地球化学省,根据铌、钽组合异常图为该区寻找稀有金属矿床提供了重要选区。研究填补了阿尔泰成矿带中蒙边界地区铌、钽元素地球化学分布的空白,同时为研究区稀有金属矿床对比提供基础数据。     

太古宙TTG的Nb/Ta变化特征:对“Nb-Ta悖论”的启示

英云闪长岩-奥长花岗岩-花岗闪长岩(TTG)是地球早期大陆地壳最重要的组成部分。TTG的Nb/Ta比值变化不仅与它的成因相关,而且与早期构造环境和地壳分异过程关系紧密。本文选择阴山地块出露的TTG片麻岩及下地壳斜长角闪岩/麻粒岩包体作为研究对象,开展了寄主花岗闪长岩和同源镁铁质包体中的角闪石和黑云母的原位微区矿物的微量元素分析工作,以及TTG与非同源斜长角闪岩包体的全岩主微量元素分析工作。矿物化学研究结果表明,花岗闪长岩和同源镁铁质包体的角闪石具有相似的Mg^#值,但是两者具有明显不同的Nb/Ta比值。镁铁质包体中的角闪石更富Cr、Ta,Nb/Ta比值为30~50;TTG岩石中的角闪石Cr和Ta含量偏低,但具有更高的Nb/Ta比值(38~70)。TTG和镁铁质包体中的角闪石Cr含量与Nb/Ta具有较好的负相关关系。全岩地球化学分析结果揭示,TTG片麻岩的具有高Nb/Ta比值(13~65,平均值31),斜长角闪岩和麻粒岩包体具有变化的Nb/Ta比值(10~56)。太古宙绿岩带中玄武质岩石的Nb/Ta平均值为~15,阴山地块斜长角闪岩和麻粒岩包体具有高的Nb/Ta比值,反映了这些代表基性下地壳的岩石经历了部分熔融作用或后期的交代作用,使其Nb/Ta比值发生改变。研究区具有高Nb/Ta比值的TTG可能来源于高Nb/Ta比值基性下地壳部分熔融,并继承了源区高Nb/Ta比值的特征。通过本文研究揭示,高Nb/Ta比值的TTG并非一定形成于俯冲带洋壳榴辉岩相部分熔融,下地壳富角闪石和黑云母的岩石部分熔融是形成高Nb/Ta比值TTG的一种重要途径。     

江苏省海州式磷矿岩石地球化学特征及成矿背景

本文对苏北地区锦屏组磷矿石及地层样品进行了岩相学及地球化学分析,研究了磷矿初始沉积环境和源区特征。磷矿类微量元素富集Ba、Pb、U、Sr,贫Th、Ta、Nb、Ti;REE配分曲线为LREE富集型,Ce负异常,表明成矿环境为陆缘海,且成矿过程受深海热水沉积和生物作用影响。Sr、Nd同位素初始值判断磷灰岩物质来源为年轻的地壳物质。绿片岩类微量元素富集Rb、Th、K,贫Th、U、Ta、Nb、Sr、Ti;REE配分曲线为LREE富集型,判断其原岩为陆源碎屑岩。（混合）片麻岩类微量元素富集Pb、Th、K,亏损Ba、Ta、Nb、Sr、Ti;REE配分曲线为LREE富集型,具地幔源区特征。     

Trace element geochemistry of scheelite and rutile from metaturbidite-hosted quartz vein gold deposits, Meguma Terrane, Nova Scotia, Canada: genetic implications

Scheelite and rutile from several metaturbidite-hosted gold-bearing quartz vein deposits of the Meguma Terrane of Nova Scotia were analyzed for trace elements including rare earth elements, niobium and tantalum. Scheelites have high concentrations of Sr, Nb, Y and rare earth elements (REE) with bell-shaped chondrite-normalized REE patterns accompanied by both positive and negative Eu anomalies. They also have high Nb/Ta ratios (80–300). Three distinct trace element types of the scheelites are interpreted to reflect chemical differences in the pulses of hydrothermal fluids. Hydrothermal rutiles have high contents of W (up to 4.2 wt.% WO₃), are rich in Ta compared to Nb and have a very low Nb/Ta ratio (~0.3). Hydrothermal fluids which produced both scheelite with a high Nb/Ta and rutile with a low Nb/Ta ratio are an efficient medium for fractionation of this ratio although these two minerals play an important role during the process.     

XRF AND INAA DETERMINATIONS OF MAJOR AND TRACE ELEMENTS IN GEOLOGICAL SURVEY OF JAPAN IGNEOUS AND SEDIMENTARY ROCK STANDARDS

Major and trace element analyses have been obtained by wavelength dispersive X-ray fluorescence for the Geological Survey of Japan Igneous rock series and selected samples from the Sedimentary rock series reference samples. Additional trace element data for the Igneous rock series were obtained by instrumental neutron activation analysis. Samples were analyzed multiple times for 10 major elements (with loss-on-ignition) and the following trace elements; As, Ba, Ce, Co, Cr, Cs, Cu, Eu, Ga, Hf, La, Lu, Nb, Nd, Ni, Pb, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, U, V, W, Y, Yb, Zn and Zr.     

小兴安岭二龙山林场堆晶辉长岩地球化学特征及构造环境

小兴安岭北部二龙山林场辉长岩的主量、微量和稀土元素的测试分析结果显示: 二龙山辉长岩为钙碱性系列、偏铝质岩石; δEu 正异常,Sr 元素含量富集明显,具有堆晶辉长岩特征; Rb /Sr、Nb / Ta、LILE/HFSE、Th /Ta、Nb /U 和Nb /La 比值特征均显示,辉长岩岩浆来自受到俯冲流体交代的地幔源区。Nb /Zr、Th /Nb、Th /Ta 和Ta /Hf 比值特征及对Th /Hf --Ta /Hf 构造环境判别图解投点表明,二龙山辉长岩形成于陆内拉张环境。     

TTG岩系Nb-Ta-La分馏特征的地球化学模拟:对太古宙板块俯冲与大陆地壳生长机制的约束

TTG的Nb/Ta比值以及Nb、Ta相对于La(代表LILE)的亏损取决于部分熔融体系中金红石、角闪石作为残留相矿物存在与否.本研究采用金红石和低Mg#角闪石的微量元素分配系数模拟部分熔融过程中Nb-Ta-La的分馏.模拟结果表明:如果与TTG熔体平衡的残留相是不含金红石的石榴角闪岩,熔体Nb/Ta比值低于源岩但Ta含...     

HFSE systematics of rutile-bearing eclogites: New insights into subduction zone processes and implications for the earth’s HFSE budget

The depleted mantle and the continental crust are generally thought to balance the budget of refractory and lithophile elements of the Bulk Silicate Earth (BSE), resulting in complementary trace element patterns. However, the two high field strength elements (HFSE) niobium and tantalum appear to contradict this mass balance. All reservoirs of the silicate Earth exhibit subchondritic Nb/Ta ratios, possibly as a result of Nb depletion.In this study a series of nineteen orogenic MORB-type eclogites from different localities was analyzed to determine their HFSE concentrations and to contribute to the question of whether subducted oceanic crust could form a hidden reservoir to account for the mass imbalance of Nb/Ta between BSE and the chondritic reservoir. Concentrations of HFSE were analyzed with isotope dilution (ID) techniques. Additionally, LA-ICPMS analyses of clinopyroxene, garnet and rutile have been performed. Rutile is by far the major host for Nb and Ta in all analyzed eclogites. However, many rutiles revealed zoning in Nb/Ta ratios, with cores being higher than rims. Accordingly, in situ analyses of rutiles have to be evaluated carefully and rutile cores do not necessarily reflect a bulk rock Nb and Ta composition, although over 90% of these elements reside in rutile.The HFSE concentration data in bulk rocks show that the orogenic eclogites have subchondritic Nb/Ta ratios and near chondritic Zr/Hf ratios. The investigated eclogites show neither enrichment of Nb compared to similarly incompatible elements (e.g. La), nor fractionation of Nb/Ta ratios relative to MOR-basalts, the likely precursor of these rocks. This indicates that during the conversion of the oceanic crust to eclogites in most cases, (1) HFSE and REE have similar mobility on average, possibly because both element groups remain in the down going slab, and (2) no significant fractionation of Nb/Ta occurs in subducted oceanic crust. With an average Nb/Ta ratio of 14.2 ± 1.4 (2s.e.), the investigated eclogites cannot balance the differences between BSE and chondrite. Additionally, as their average Nb/Ta is indistinguishable from the Nb/Ta of MORB, they are also an unlikely candidate to balance the potentially small differences in Nb/Ta between the continental crust and the mantle.     

变基性岩部分熔融过程中榍石的微量元素效应:以南迦巴瓦混合岩为例

南迦巴瓦地区广泛出露的中下地壳变基性岩部分熔融形成的层状混合岩和淡色花岗岩,为研究部分熔融过程中榍石的地球化学行为对熔体的微量元素组成的影响提供了良好的机会。相对于源岩或熔融残留体,淡色体亏损Ti、V、REE、Y、Nb、Ta、U等元素,与混合岩中榍石的微量元素特征互补。混合岩、淡色体和榍石微量元素特征表明南迦巴瓦角闪岩部分熔融形成的淡色体的微量元素特征主要受控于榍石的地球化学行为。角闪岩脱水部分熔融过程中,由于长英质熔体的低Ti溶解度,榍石以未熔残留体形式存在于暗色体中,导致熔体亏损Ti、REE、Nb、Ta、V、U等元素和Sr/Y比值相对升高。关键元素在榍石和熔体之间的配分系数受熔体成分影响明显。角闪岩中变质榍石D_Nb/Ta<1,因此变质榍石残留导致熔体Nb/Ta相对于源岩升高;而高Si-Al花岗质熔体中榍石D_Nb/Ta>1,因此与高Si-Al熔体平衡的榍石的分离（转熔或结晶分异）将导致熔体Nb/Ta比值相对源岩降低。榍石在部分熔融过程中的微量元素效应为理解变基性岩部分熔融产生熔体的地球化学特征提供新的认识。     

法国Beauvoir和Montebras花岗岩中富铌钽锡石的拉曼光谱特征

法国Beauvoir花岗岩和Montebras花岗岩中的锡石都含有较丰富的微量元素,如Nb、Ta,并含有铌钽矿包裹体。将锡石晶体制成光薄片,运用拉曼探针,对不同部位进行的研究表明,锡石的A_(1g)峰的振动频率与其所含的Nb、Ta、Fe、Mn含量成反比。值得指出的是,在富含铌钽包裹体的部分,发现了一个新的拉曼光谱峰(定为An峰),其振动频率为827—830cm~(-1),对其进行的研究表明,该峰的出现与锡石晶格中(Nb,Ta)的过量和铌钽矿包裹体的出溶所造成的晶体结构的变化有关。     

Garnet fractionation,progressive melt loss and bulk composition variations in anatectic metabasites:Complications for interpreting the geodynamic significance of TTGs

Tonalite-trondhjemite-granodiorite(TTG) suites constitute a large proportion of the Archean geological record;however,the geodynamic processes that generated them,and Archean continental crust in general,remain a subject of debate.The concentrations and ratios of Sr,Y,La,Yb,Nb,and Ta in TTGs are commonly used to determine the depth of melting of their metabasic sources.The trace element composition of melt produced by metabasic source rocks during anatexis is strongly affected by the presence and abundance of pressure-sensitive minerals,such as plagioclase(Sr-bearing),garnet(Y-and HREE-bearing),and rutile(Nb-and Ta-bearing).Elevated Sr/Y and La/Yb ratios and low concentrations of Nb and Ta in TTGs are generally considered to indicate melting at high pressures(≥2.0 GPa).The depth of melting is a key factor in determining the origin of TTGs as this provides critical information on the tectonic setting of their generation.We use phase equilibrium and trace element modelling to explore the effects of three potential influences on TTG trace element compositions:fractionation of trace elements into peritectic garnet cores,progressive melt loss from the source,and source bulk composition.We model three different compositions of Archean basalts along thermal gradients of 500℃/GPa,750℃/GPa,and 1000℃/GPa.The models produce maj or and trace element melt compositions that are generally consistent with measured compositions of TTGs.Although Sr/Y,La/Yb,Nb,and Ta exhibit pressure-dependent behaviour,other factors also affect these values.Garnet fractionation causes Sr/Y and La/Yb to reach much greater values and in this scenario,the values also increase with increasing temperature.Source bulk composition has an effect in all scenarios and most strongly influences La/Yb,Nb,and Ta.Overall,these results show that Sr/Y,La/Yb,Nb,and Ta can reach values generally considered to be indicative of high pressure melting at a range of P-T conditions including P 2.0 GPa.Consequently,trace element compositions of TTGs alone may provide a misleading impression of the depth of melting of metabasites and the geodynamic environment of Archean crustal growth and reworking.