同一岩石试样的Lu-Hf和Sm-Nd快速分离及国家岩石标准物质的Hf-Nd同位素比值精确测定   总被引：1，自引：2，他引：1  

李献华 刘颖杨岳衡  陈福坤涂湘林 祁昌实 《岩石学报》2007,23(2):221-226

本文报道基于Li_2B_4O_7熔融样品、采用AG50W-X8和HDEHP组合或RE和HDEHP组合色谱交换柱,对同一岩石试样快速分离Sm-Nd-Lu-Hf的方法。用这两种方法对国际岩石标准BHVO-2、GSP-2和JB-1进行了Lu-Hf、Sm-Nd分离和~(143) Nd/~(144)Nd、~(176)Hf/~(177)Hf测定,并测定了BHVO-2、JB-1和JB-3的Lu/Hf和Sm/Nd比值,获得的结果在误差范围内与这些样品的参考值一致。同时,我们对国家岩石标准物质GBW07109、GBW07110和GBW07113进行了多次平行分析,首次获得了这些岩石标准的Nd-Hf同位素结果。  相似文献   

新疆东准噶尔花岗岩的全岩Hf同位素研究     

陈娟  唐红峰  灌瑾  王宁 《矿物学报》2014,(2):290-295

在综合对比已有Hf同位素分析方法的基础上,我们选用Ln-Spec(100-150目,H+)特效树脂和多接收器电感耦合等离子体质谱(MC-ICPMS)对4件标准物质和19件岩石样品(新疆东准噶尔的花岗岩及其包体18件、玄武岩1件)进行了全岩Hf同位素研究。所获得的国际标准物质BCR-1、BHVO-2、W-2的176Hf/177Hf比值与文献报道的结果在误差范围内一致,表明所采用的全岩Hf的化学分离和溶液的Hf同位素质谱测定方法是可靠的。本文首次报道了中国花岗岩标样GRS-1的176Hf/177Hf比值,结果为0.282547?07(2?)。依据新疆东准噶尔花岗岩及其包体样品的全岩176Hf/177Hf比值、全岩样品在等离子体质谱(ICP-MS)上测定的Lu、Hf含量和岩石的形成年龄(300 Ma),得到这些样品的全岩εHf(t)。它们与对应样品的锆石εHf(t)在误差范围内总体上的一致性表明,ICP-MS测定的Lu、Hf含量可以用来计算年龄值约300 Ma的全岩初始Hf同位素组成。玄武岩样品QS08-1的全岩εHf(t)与该蛇绿岩套斜长花岗岩的锆石εHf(t)的高度吻合,为利用全岩176Hf/177Hf比值和ICP-MS测定的全岩Lu、Hf含量,研究没有或难以选出锆石的较年轻岩石的Hf同位素组成提供了很好的实例。  相似文献   

锆石Hf同位素组成的LAM-MC-ICPMS精确测定   总被引：23，自引：1，他引：23  

李献华  梁细荣  韦刚健  刘颖 《地球化学》2003,32(1):86-90

在配备了NewWaveMerchantekLUV213型紫外激光探针进样系统的Isoprobe型MC—ICPMS上进行了溶液和锆石单矿物的Hf同位素比值测定，并对^176Yb和^176Lu对^176Hf的同质异位素干扰校正进行了试验。结果表明，由于自然界Lu的丰度远远小于Yb，所以^176Hf的同质异位素干扰主要来自^176Yb。当Yb／Hf较低时，可以通过同质异位素干扰校正直接难确测定出^176Hf／^177Hf比值；当Yb／Hf比值较高时，则需要进行同质异位素干扰校正和外部校正来获得难确的^176Hf／^177Hf比值。因此，用LAM—MC-ICPMS可以难确、快速地测定锆石的Hf同位素组成。  相似文献   

Lu-Hf年代学研究——以大别榴辉岩为例   总被引：3，自引：2，他引：3  

袁洪林高山  罗彦宗春蕾  戴梦宁柳小明 第五春荣 《岩石学报》2007,23(2):233-239

本文利用多接收电感耦合等离子体质谱仪(MC-ICP-MS)进行了同位素稀释法Lu-Hf年代学研究,建立了全岩Lu、Hf的分离条件。分离后Lu溶液中~(176)Lu/~(176)Yb大于30,分离后Hf溶液中Lu和Yb对Hf的干扰(~(176)Lu/~(176)Hf和~(176)Yb/~(176)Hf分别小于2×10~(-6)和2×10~(-4))采用指数法则进行校正。建立了MC-ICP-MS进行Lu、Hf同位素高精度准确测试的校正方法。天然样品中Hf同住素~(176)Hf/~(177)Hf的内部测试精度优于0.0015%,外部精密度优于0.0010%。应用本文建立的方法获得大别双河榴辉岩石榴子石-全岩Lu-Hf等时线年龄为254±16Ma(2σ)。年龄误差稍大与该样品石榴子石中较低的Lu含量(1.1μg/g)和石榴子石-全岩的未充分分开的~(176)Lu/~(177)Hf比值(分别为0.05和0.01)有关。  相似文献   

鲁西新泰孟家屯2.7Ga变质沉积岩与黑云斜长片麻岩锆石Hf同位素特征   总被引：6，自引：0，他引：6  

杜利林  杨崇辉  庄育勋  韦汝征  万渝生  任留东  侯可军 《地质学报》2010,84(7):991-1001

对出露于山东新泰孟家屯2.7Ga的孟家屯岩组中石榴石石英岩(M08)、含十字石石榴石黑云母石英片岩(D242-Y2)和黑云斜长片麻岩(M03)(TTG质片麻岩)进行锆石Lu-Hf同位素分析。石榴石石英岩锆石核部176Lu/177Hf、176Hf/177Hf变化范围为0.001730～0.002546、0.281249～0.281360,锆石变质边部176Lu/177Hf、176Hf/177Hf变化范围为0.000123～0.002070、0.281241～0.281318;含十字石石榴石黑云母石英片岩锆石核部176Lu/177Hf、176Hf/177Hf变化范围为0.001334～0.002169、0.281226～0.281324,锆石变质边部176Lu/177Hf、176Hf/177Hf变化范围为0.000445～0.001375、0.281227～0.281309;黑云斜长片麻岩锆石176Lu/177Hf、176Hf/177Hf变化范围为0.000315～0.000847、0.281186～0.281265。孟家屯岩组石榴石英岩、含十字石石榴石黑去母石英片岩中碎屑(岩浆)锆石和黑云斜长片麻岩中岩浆锆石的εHf(t)分别为3.75～7.26、2.31～7.26和3.21～6.27,同时TDM1与其U-Pb年龄非常接近,表明它们起源于新生地壳的部分熔融。结合区域研究资料认为,2.7Ga是鲁西重要的一期构造岩浆热事件,也可能是华北克拉通重要的构造岩浆活动时期。变质沉积岩中许多变质增生锆石相对于核部岩浆锆石低176Lu/177Hf、高176Hf/177Hf,显示变质作用过程中石榴石的存在对锆石的Lu-Hf同位素体系有很大影响。  相似文献   

磷灰石Lu-Hf同位素年代学研究——以河北矾山磷矿为例     

《吉林大学学报(地球科学版)》2015,(Z1)

磷灰石是广泛出露于三大类岩石中的副矿物,由于磷灰石具有较高的Lu/Hf比值(最高可达约90,而通常用过Lu-Hf定年的石榴石最高只有28),因而是进行高精度Lu-Hf同位素定年的理想矿物。例如在经常缺乏锆石等常规定年矿物的镁铁质岩浆岩中,或者在角闪岩和大理岩等变质岩石中,磷灰石具有常规定年矿物无法替代的优势。但是,磷灰石中极低的Hf含量使得难以获得准确的176Lu/177Hf和176Hf/177Hf比值,阻碍了构筑高精度Lu-Hf矿物等时线。本次研究笔者将AridusⅡ膜去溶与多接收电感耦合等离子体质谱(MC-ICP-MS)联用,有效降低了基体氧化物和氢化物的干扰,提高了仪器信号强度和稳定性,获得了精准的Lu-Hf同位素比值。运用上述方法,我们对采自华北克拉通北缘矾山碱性杂岩体中不同岩带的磷灰石、榍石和辉石获得了高精度的176Lu/177Hf和176Hf/177Hf比值,矿物内部等时线年龄为(226.5±3.6)Ma和(231.3±3.1)Ma。该结果与同一样品中的副矿物(锆石、斜锆石、钙钛矿和榍石)的U-Pb年代学结果一致,不但证明了我们Lu-Hf同位素年代学方法的可行性与可靠性,也进一步限定了矾山杂岩体形成的时代。同时,结合全岩和单矿物的微量元素及Sr-Nd同位素特征,为矾山岩体的演化过程提供了制约条件。  相似文献   

大别地体超高压变质岩石锆石Lu-Hf同位素研究   总被引：2，自引：3，他引：2  

陈道公倪涛  谢烈文 《岩石学报》2007,23(2):331-342

对大别山南部超高压变质带双河和黄镇地区的榴辉岩、片麻岩和硬玉石英岩中变质锆石进行了原位LA-MC-ICP- MS的Lu-Hf同位素分析。双河和黄镇的榴辉岩及双河的硬玉石英岩有低~(176)Lu/~(177)Hf和低~(176)Hf/~(177)Hf组成,两地的片麻岩有高~(176)Hf/~(177)Hf比和高且分散的~(176)Lu/~(177)Hf组成。锆石Hf同位素分布主要受变质原岩的形成时代控制,增生锆石基本上继承了原岩锆石的Hf同位素特征,既有增生锆石相对有低~(176)Lu/~(177)Hf和高~(176)Hf/~(177)Hf、继承重结晶锆石相对有高~(176)Lu/~(177)Hf和低~(176)Hf/~(177)Hf的特征,也有二者相互重叠没有区别的,它主要受原岩性质和变质过程中锆石遭受的溶蚀程度控制。增生锆石的低Lu/Hf是锆石在变质过程中Lu含量下降和Hf含量增高造成的,增生锆石的高~(176)Hf/~(177)Hf继承自岩石中其它高Lu/Hf比矿物的长期演化。继承锆石的初始Hf同位素组成ε_(Hf)值和亏损地幔模式年龄T_(DM)示踪表明,各超高压变质原岩的时代和成因是复杂的:双河榴辉岩原岩物质源自25亿年的亏损地幔和至少27亿年以上的古老晚太古地壳混合。双河片麻岩原岩年龄相同,但有不同的壳幔混合物源。黄镇榴辉岩原岩主要源于亏损幔源岩浆形成的初生地壳的重循环,很少的地壳混染。黄镇片麻岩和榴辉岩的物源区年龄相同。两地片麻岩原岩物源主要来自弱亏损地幔,存在古老地壳物质和地幔物质的混合。大别地区超高压变质岩锆石的Lu-Hf同位素特征主要反映了7～8亿年和18～19亿年时扬子克拉通北缘地区的岩浆活动特点和大地构造环境。  相似文献   

西藏拉萨地块松多榴辉岩的锆石Lu/Hf同位素研究及LA-ICPMS U-Pb定年   总被引：7，自引：2，他引：5  

陈松永  杨经绥  徐向珍  李化启  杨岳衡 《岩石学报》2008,24(7)

最近在青藏高原拉萨地块中发现一条榴辉岩带.榴辉岩带位于拉萨北东近200km处的松多乡一带,呈近东西方向延伸,至少长60kin,宽2km～3km.锆石样品选自新鲜的榴辉岩样品,共测了39个数据点,其中前19个数据点仅做Lu-Hf同位素分析,后20个数据点既做了锆石原位Lu-Hf同位素分析,同时也做了锆石原位LA-MC-ICPMS U-Pb定年.结果表明,松多榴辉岩锆石Hf同位素组成比较均一,具有高176Hf/177Hf和低176Lu/177Hf特征,176Hf/177Hf和176Lu/176Hf值分别变化在0.2829651～0.2830295和0.000002～0.000008之间,其可能代表全岩体系在变质作用发生时的平均Hf同位素组成.松多榴辉岩的高176Hf/177Hf和低176Lu/177Hf组成特征可能跟其高压变质作用以及在变质作用过程中形成石榴子石矿物有关.εHf(0)变化于6.8～10.0,表明在其变质过程中,变质流体有亏损地幔物质的加入.LA-ICPMS锆石U-Pb定年,所获得加权平均年龄260Ma±16Ma,为变质年龄.从而进一步确定了松多榴辉岩变质事件发生在二叠纪.  相似文献   

锆石Hf同位素组成的LA-MC-ICP-MS测定   总被引：48，自引：4，他引：44  

耿建珍  李怀坤  张健  周红英  李惠民 《地质通报》2011,30(10):1508-1513

利用多接收器等离子体质谱仪(MC-ICPMS)和193nm准分子激光器联用技术,对GJ-1、Temora、91500和Mud Tank四个标准锆石的Hf同位素组成进行测试,并通过指数方法进行同质异位素干扰校正,测得它们的176Hf/177Hf比值分别为0.282006±24(n=159, 2SD)、0.282684±46(n=20, 2SD)、0.282305±32(n=20, 2SD)和0.282509±25(n=48, 2SD)。测定结果与文献报道的值在误差范围内一致。  相似文献   

一件可能的Hf同位素测定标准锆石     

周红英  李怀坤  耿建珍  苏文博  相振群  崔玉荣  张健  李惠民 《地质学报》2013,87(4):554-564

陕西省西乡县汉南杂岩望江山岩体辉长岩中含有丰富的锆石——从600kg辉长岩样品中分选出结晶良好、内部结构简单、成因和年龄单一、Hf同位素比值均一的锆石7g,锆石粒度多为0.2-0.3mm。分别在三个不同实验室利用三种方法对该锆石样品进行了U-Pb同位素年龄测定,获得了在误差范围内完全一致的年龄：819.8 ± 2.5 Ma（LA-ICP-MS）、821.7 ± 1.7 Ma（LA-MC-ICPMS）和822.1 ± 4.5 Ma（SHRIMP）。在国内4个权威实验室对该锆石进行了Lu-Hf同位素测定,获得了在误差范围内完全一致的176Hf/177Hf同位素比值——全部421个测试点加权平均值为0.282535 ± 0.000003（2σ）。采样点岩体规模巨大,露头良好,岩石新鲜,交通方便。该锆石样品满足作为Hf同位素测定标样的各方面的指标,可能是一个比较理想的Hf 同位素测定标样。Hf同位素测定标准物质的研制,是测定获得准确可靠的Hf同位素数据的基础,具有十分重要的实用价值和科学意义。  相似文献   

Instrumental Neutron Activation Analysis of Silicate Rock Standards AN-G, BHVO-1, QLO-1, RGM-1, and STM-1     

Karl E. SEIFERT 《Geostandards and Geoanalytical Research》1984,8(1):35-38

Silicate rock standards AN-G, BHVO-1, QLO-1, RGM-1, SDC-1 and STM-1 have been analyzed for 7 REE (La, Ce, Sm, Eu, Tb, Yb and Lu), Na₂O, FeO_t, Sc, Co, Cr, Ta, Hf and Th by instrumental neutron activation analysis. The mean values are compared to those from other studies reported in the literature.  相似文献   

A routine high-precision method for Lu-Hf isotope geochemistry and chronology     

P. J. Patchett  M. Tatsumoto 《Contributions to Mineralogy and Petrology》1980,75(3):263-267

A method for chemical separation of Lu and Hf from rock, meteorite and mineral samples is described, together with a much improved mass spectrometric running technique for Hf. This allows (i) geo- and cosmochronology using the¹⁷⁶Lu→¹⁷⁶Hf+β^? decay scheme, and (ii) geochemical studies of planetary processes in the earth and moon.Chemical yields for the three-stage ion-exchange column procedure average 90% for Hf. Chemical blanks are <0.2 ng for Lu and Hf. From 1 μg of Hf, a total ion current of 0.5×10^?11 Ampere can be maintained for 3–5 h, yielding 0.01–0.03% precision on the ratio¹⁷⁶Hf/¹⁷⁷Hf. Normalisation to¹⁷⁹Hf/¹⁷⁷Hf=0.7325 is used.Extensive results for the Johnson Matthey Hf standard JMC 475 are presented, and this sample is urged as an international mass spectrometric standard; suitable aliquots, prepared from a single batch of JMC 475, are available from Denver.Lu-Hf analyses of the standard rocks BCR-1 and JB-1 are given. The potential of the Lu-Hf method in isotope geochemistry is assessed.  相似文献   

北苏鲁仰口地区变辉长岩中锆石U-Pb定年、微量元素和Hf同位素特征及其地质意义   总被引：5，自引：3，他引：2  

刘福来  刘平华 《岩石学报》2009,25(9):2113-2131

北苏鲁仰口地区出露超高压的变辉长岩.锆石阴极发光图像和其内部矿物包体激光拉曼测试的联合研究结果表明,变辉长岩锆石具有弱发光效应的岩浆韵律环带的核和被改造的强发光效应的边.岩浆韵律环带的核部保存大量而复杂的矿物包体,包括普通辉石(Cpx)+斜方辉石(Opx)+斜长石(P1)+石英(Qtz)+黑云母(Bt)+钛铁矿(Ilm)+磷灰石(Ap);边部保存的矿物包体则相对较少,包括普通辉石(Cpx)+斜方辉石(Opx)+斜长石(Pl)+磷灰石(Ap).尽管岩浆韵律环带核部的稀土元素总合量比被改造的锆石边部明显偏高,但二者稀土元素配分模式具有明显的相似性,主要表现为轻稀土相对亏损,而重稀土明显富集,相应的(La/Yb)N=0.00015～0.00039,并具有明显的负Eu异常(Eu/Eu*=0.20～0.26)、相对明显的正Ce异常(Ce/Ce*=71.5～147.4)和较高的Th/U比值(1.97～2.69).上述特征表明,仰口地区变辉长岩中的锆石均为继承性的岩浆锆石,而没有新生的变质锆石.LA-(MC)-ICP-MS锆石原位U-Pb定年和Lu-Hf同位素分析结果表明,两件锆石样品Y1和Y2的年龄数据所构成的不一致线显示了十分接近的上交点和下交点年龄.其上交点年龄分别为785±15Ma(2σ)和784±12Ma(2σ),应代表原岩的形成时代,表明变辉长岩的原岩与Rodinia超大陆裂解的岩浆事件存在密切的成因关系;而下交点年龄分别为226±24Ma(2σ)和228±26Ma(2σ),与苏鲁其它类型超高压岩石中含柯石英锆石微区记录的变质年龄十分吻合,应代表变辉长岩的超高压变质时代.岩浆结晶锆石的核部具有明显偏高的176Lu/177Hf(0.00044～0.00291)和176Yh/177Hf(0.0165～0.1168)比值,而176Hf/177Hf比值变化于0.281956～0.282048之间,相应的εHf(t)=-8.5～-14.0,tDM2=2.03～2.32Ga,表明仰口地区变辉长岩的原岩起源于古元古代时期的富集地幔或发生部分熔融的下地壳残留体.被改造的岩浆结晶锆石的边部则具有明显偏低的176Lu/177Hf(0.00029～0.00060)和176Yh/177Hf(0.0112～0.0200)比值,而176Hf/177Hf(t)比值变化于0.281953～0.282002之间,相应的εHf(t)=-10.2～-11.9,tDM2=2.12～2.21Ga.与岩浆结晶锆石核部相比,被改造的岩浆锆石边部的176Lu/177Hf、176Yb/177Hf、176Hf/177Hf(t)比值和εHf(t)和tDM2值的变化范围更小,表明中-新三叠纪的超高压变质作用使岩浆结晶锆石边部的Lu-Hf同位素体系发生调整,更趋向于均一化.  相似文献   

Separation of Hf and Lu for high-precision isotope analysis of rock samples by magnetic sector-multiple collector ICP-MS   总被引：35，自引：1，他引：35  

J. Blichert-Toft  Catherine Chauvel  F. Albarède 《Contributions to Mineralogy and Petrology》1997,127(3):248-260

Potential applications of the Lu-Hf isotope system have long been impeded by the analytical difficulties of obtaining data on a wide variety of geological materials. Many of these limitations will now be eliminated because Hf isotopes can be readily measured with high precision and accuracy on small and/or Hf-poor samples using the newly developed magnetic sector-multiple collector ICP-MS, also known as MC-ICP-MS or the `Plasma 54'. We present here a new method to separate and determine isotopic compositions of both Hf and Lu from various types of geological materials using MC-ICP-MS. The chemical separation of Hf and Lu has been designed to take advantage of the characteristics of this unique instrument. The separation of Hf can be achieved with a straightforward two-step ion-exchange column chemistry, which has a high efficiency (better than 85% recovery) and low blanks (typical total blanks less than 150 pg for the largest samples of 1 g bulk rock). The isolation of Lu is achieved with a single-stage ion-exchange column procedure with near 100% yields and blanks below 20 pg. Hf isotopic compositions can be routinely measured on 50 ng Hf with an internal precision better than 20 ppm in less than 15 min and with an external precision better than 40 ppm. Our value for the ¹⁷⁶Hf/¹⁷⁷Hf ratio of the JMC 475 Hf standard currently is 0.282163 ± 9 (2s). The Lu isotopic ratio is measured rapidly and precisely without isolating Lu from the bulk of Yb, and a mass fractionation correction increases the accuracy of the results compared with TIMS data. Our current reproducibility of the Lu/Hf ratio is ≈1%. Selected Lu-Hf isotope analyses of some modern and ancient geological samples validate the technique we have described here and illustrate the new opportunities for Lu-Hf isotope geochemistry that have opened up with the advent of magnetic-sector ICP mass spectrometry. Received: 12 September 1996 / Accepted: 13 January 1997  相似文献   

A New Digestion and Chemical Separation Technique for Rapid and Highly Reproducible Determination of Lu/Hf and Hf Isotope Ratios in Geological Materials by MC-ICP-MS   总被引：7，自引：0，他引：7  

Martin Bizzarro  Joel A. Baker  David Ulfbeck 《Geostandards and Geoanalytical Research》2003,27(2):133-145

A new digestion procedure and chemical separation technique has been developed for measurement of Lu/Hf and Hf isotope ratios that does not require high‐pressure bombs or use of HF or HClO₄ acids. Samples are digested in dilute HCl or HNO₃ after flux‐fusion at 110 0 °C in the presence of lithium metaborate. High field strength elements (HFSE) and rare earth elements (REE) are separated from this solution by co‐precipitation with iron hydroxide. The dissolved precipitate (in 2 mol l^?1 HCl) is loaded directly onto a standard cation exchange column which separates remaining sample matrix from the heavy REE (Lu+Yb), and the middle‐light REE and HFSE (Hf). The middle‐light REE and individual HFSE are then separated (10.5, 9 and 6 mol l^?1 HCl) using a miniaturized column containing TEVA spec resin which provides a REE‐, Ti‐ and Zr‐free Hf cut. This chemical separation scheme can also be readily adapted for isotopic analysis of the Sm‐Nd system and/or the other HFSE (Ti, Zr). Total procedural blanks for this technique are < 10 0 pg and < 2 pg for Hf and Lu, respectively, even when digesting large (0.5 g) samples. We present data from replicate digestions of international rock reference materials which demonstrate this technique routinely reproduces Lu/Hf ratios to < 0.2% (2s) and ¹⁷⁶ Hf/¹⁷⁷ Hf isotope ratios to < 30 ppm (2s). Moreover, the technique is matrix‐independent and has been successfully applied to analysis of diverse materials including basalts, meteorites, komatiites, kimberlites and carbonatites. The relative simplicity of this technique, coupled with the ease of digestion (and sample‐spike equilibration) of large difficult‐to‐dissolve samples, and the speed (2 days) with which samples can be digested and processed through the chemical separation scheme makes it an attractive new method for preparing samples for Lu‐Hf isotopic investigation.  相似文献   

Hafnium Isotope Characteristics of Palaeoarchaean Zircon OG1/OGC from the Owens Gully Diorite,Pilbara Craton,Western Australia          下载免费PDF全文

Anthony I. S. Kemp  Jeffrey D. Vervoort  Katarina E. Bjorkman  Linda M. Iaccheri 《Geostandards and Geoanalytical Research》2017,41(4):659-673

We report Hf isotope data for 3467 Ma igneous zircons from the Owens Gully Diorite of the Pilbara Craton. These zircons, designated OG1 or OGC, have simple, well‐defined U‐Pb age systematics. Measurements obtained by single crystal dissolution yield a moderate range in ¹⁷⁶Hf/¹⁷⁷Hf (mean 0.280633 ± 34) and ¹⁷⁶Lu/¹⁷⁷Hf (mean 0.00119) that translate into initial (3467 Ma) ¹⁷⁶Hf/¹⁷⁷Hf values that are equivalent within measurement uncertainty (mean 0.280554 ± 7, ε_Hf = +0.6 ± 0.2, 2s). Laser ablation analysis yielded clustered initial ¹⁷⁶Hf/¹⁷⁷Hf ratios (mean 0.280560 ± 20, 2s) indistinguishable from those obtained by solution analysis. The antiquity and moderately high ¹⁷⁶Lu/¹⁷⁷Hf of these zircons result in significant corrections for radiogenic ingrowth of ¹⁷⁶Hf (to 6 ε_Hf units). Depth profiling by concurrent Pb‐Hf isotope determination reveals trends to lower ²⁰⁷Pb/²⁰⁶Pb in several crystals, although these are not accompanied by shifts in ¹⁷⁶Hf/¹⁷⁷Hf. We conclude that zircons from the Owens Gully Diorite are homogeneous for Hf isotopes at the scale of sampling and within the uncertainty limits of the measurement techniques employed. Zircon OG1/OGC would appear to be an ideal quality monitor for laser ablation Hf isotope determination in ancient zircons, and for laser ablation techniques where Hf isotope and age information are determined concurrently or simultaneously.  相似文献   

The Hf isotopic composition of zircon reference material 91500   总被引：2，自引：0，他引：2  

Janne Blichert-Toft   《Chemical Geology》2008,253(3-4):252-257

Ten new single zircon fragments, analyzed by solution chemistry and MC-ICP-MS, of the 91500 zircon standard show no evidence to support a recent claim based on in situ data that this reference material is heterogeneous in terms of its radiogenic Hf isotope composition and as a consequence should be abandoned as a reliable interlaboratory standard. Rather, the larger spread in ¹⁷⁶Hf/¹⁷⁷Hf among in situ data compared with solution chemistry data may reflect the uncertainties resulting from prominent isobaric interference corrections inherent to the in situ analytical protocol. The unweighted mean values of ¹⁷⁶Hf/¹⁷⁷Hf and ¹⁷⁶Lu/¹⁷⁷Hf measured for the ten zircon fragments of this study are 0.282313 ± 0.000008 (2σ) and 0.000311 ± 0.000136 (2σ), respectively. Pooling the mean ¹⁷⁶Hf/¹⁷⁷Hf of this work with those of published solution chemistry studies results in a value of 0.282308 ± 0.000006 (2σ; relative to ¹⁷⁶Hf/¹⁷⁷Hf = 0.282163 for JMC-475), which is recommended here as the currently best estimate of the Hf isotopic composition of this standard. All published studies agree on a value of ~ 0.0003 for the corresponding ¹⁷⁶Lu/¹⁷⁷Hf ratio.  相似文献   

A routine high-precision method for Lu-Hf isotope geochemistry and chronology   总被引：6，自引：0，他引：6  

P. J. Patchett  M. Tatsumoto 《Contributions to Mineralogy and Petrology》1981,75(3):263-267

A method for chemical separation of Lu and Hf from rock, meteorite and mineral samples is described, together with a much improved mass spectrometric running technique for Hf. This allows (i) geo- and cosmochronology using the¹⁷⁶Lu¹⁷⁶Hf+ ^– decay scheme, and (ii) geochemical studies of planetary processes in the earth and moon.Chemical yields for the three-stage ion-exchange column procedure average 90% for Hf. Chemical blanks are <0.2 ng for Lu and Hf. From 1 g of Hf, a total ion current of 0.5×10^–11 Ampere can be maintained for 3–5 h, yielding 0.01–0.03% precision on the ratio¹⁷⁶Hf/¹⁷⁷Hf. Normalisation to¹⁷⁹Hf/¹⁷⁷Hf=0.7325 is used.Extensive results for the Johnson Matthey Hf standard JMC 475 are presented, and this sample is urged as an international mass spectrometric standard; suitable aliquots, prepared from a single batch of JMC 475, are available from Denver.Lu-Hf analyses of the standard rocks BCR-1 and JB-1 are given. The potential of the Lu-Hf method in isotope geochemistry is assessed.  相似文献