New REE and Trace Element Data on Two Kimberlitic Reference Materials by ICP-MS

New REE and Trace Element Data on TwoKimberlitic Reference Materials by ICP-MS

Vol. 31 — N° 3 p . 2 6 1 - 2 7 3

Data on thirty-four minor and trace elements including all rare earth elements (REE) are reportedfor two kimberlitic international reference materials(SARM-39, MINTEK, RSA and MY-4, IGEM, Russia)by inductively coupled plasma-mass spectrometry (ICP-MS), some of them for the first time. Four digestion techniques (open acid, closed vessel acid,microwave and lithium metaborate fusion digestion)were used for the decomposition of samples foranalysis by ICP-MS. Three other reference materials(USGS BHVO-1, CRPG BR-1 and ANRT UB-N) wereanalysed simultaneously using the same analyticalmethodology to assess the precision and accuracyof the determinations. The data obtained in thisstudy compare well with working values whereversuch values are available for comparison. Thoughopen acid digestion was found to be very rapid,effective and convenient for the determination of several trace elements in kimberlitic samples,recoveries for heavy rare earth elements (HREE)were lower than the respective recoveries obtainedby the other decomposition techniques used. Theprecision obtained was better than ± 6% RSD in the majority of cases with comparable accuracy.Chondrite-normalised plots of each RM for all thedigestion techniques were smooth. The new datareported on the two kimberlitic reference materialsmake these samples useful for future geochemicalstudies of kimberlitic rocks.

Keywords: kimberlite reference materials, SARM-39,MY-4, ICP-MS, acid digestion, fusion digestion.

Sont présentées ici les concentrations de trentequatre éléments en trace et mineurs, dont les TerresRares, mesurées sur deux matériaux certifiés deréférence de composition kimberlitique : SARM 39(MINTEK, RSA) et MY-4 (IGEM, Russie), par spectrométrie de masse couplée à une source àplasma induit (ICP-MS), certains éléments étantmesurés pour la première fois. Quatre méthodes de minéralisation ont été utilisées pour la mise ensolution des échantillons avant leur analyse parICP-MS (attaque acide en conteneur ouvert, ou enconteneur clos, attaque par micro-onde et fusionavec du métaborate de lithium). Trois autres matériaux de référence (USGS BHVO-1, CRPG BR-1et ANRT UB-N) ont été analysés en même temps,avec le même protocole analytique, pour contrôlerla précision et la justesse des déterminations. Lesrésultats obtenus au cours de cette étude sont enaccord avec les valeurs de travail, quand celles-cisont données. Bien que l'attaque avec des acidesen conteneur ouvert se soit révélée rapide, efficaceet adaptée à un certain nombre d'éléments en tracedans les échantillons kimberlitiques, le rendementpour les Terres Rares y étaient inférieurs aux rendements obtenus pour les autres méthodes demise en solution. La précision obtenue est meilleureque 6% RSD dans la majorité des cas, avec des justesses toutes du même ordre. Les spectres deTerres Rares normalisés aux chondrites de chaquematériau de référence étaient tous réguliers, quelquesoit la méthode de mise en solution. Ces nouvellesdonnées sur les deux matériaux de référence kimberlitiques en font des matériaux très utiles dans le futur pour toute étude de kimberlites.

Mots-clés : matériaux de référence kimberlitiques,SARM-39, MY-4, ICP-MS, minéralisation avec desacides, minéralisation par fusion.

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0907

Parijat Roy*, Vysetti Balaram, Anil Kumar, Manavalan Satyanarayanan and Thota Gnaneshwar Rao

Geochemistry Division, National Geophysical Research Institute, Uppal Road, Hyderabad-500007, India* Corresponding author. e-mail: [email protected]

© 2007 NGRI (India). Journal compilation © 2007 International Association of Geoanalysts

Received 08 Jan 07 — Accepted 03 May 07

GEOSTANDARDS and

RESEARCHGEOANALYTICAL

Trace and REE data in kimberlites and related rocks,provide valuable information on magmatic processes inthe mantle as these rocks are believed to originate fromvery deep sources (Mitchell 1986). Inductively coupledplasma mass-spectrometry (ICP-MS) is now an establi-shed technique for the determination of trace elementsincluding rare earth elements (REE) (Jarvis et al. 1992).To obtain interference-free, precise and accurate resultsby ICP-MS, it is necessary to use matrix-matched calibra-tors to minimise matrix interferences and reduce drifteffects between sample and calibrator. The accuracy ofthe data is also strongly dependent on the quality andthe uncertainty of the certified values of the referencematerials used as calibrators. Due to the complex andhighly variable chemical composition of geologicalmaterials, it is important to have reference materials withwell-established and reliable data (Chao et al. 1992,Marina et al. 1992). Two kimberlitic reference materialsnamely, SARM-39 (MINTEK, RSA) and MY-4 (IGEM,Russia) are available at present, for which no certifieddata are available for REE and for the majority of thegeochemically significant trace elements (Govindaraju1994). Korotev (1996) presented data for SARM-39 bythe INAA method. To obtain accurate trace elementdata by ICP-MS, it is essential that rock samples arecompletely dissolved (Garbe-Schönberg 1993). This isespecially true in case of kimberlites, since these rocksare mantle-derived and carry various minerals that arehighly resistant, such as garnets, ilmenite, spinel, perovs-kite, zircon and rutile. Hence, complete dissolution ofthese rocks is a problem. Much less work has beendone to better characterise these reference materials,

despite their significance in contributing to an unders-tanding of this important rock type. Therefore, a detailedstudy was undertaken using various dissolution tech-niques including open acid, closed vessel, microwaveand lithium metaborate fusion digestion to provide datafor the REE and several other t race elements forthese two international kimberlitic reference materials.This work will be useful to better constrain the traceelemental abundances in these samples.

Experimental

Three certified reference materials (CRMs), BHVO-1,BR and UB-N were analysed together with the kimber-litic reference materials, MY-4 and SARM-39. Descrip-tions of these RMs are given in Table 1. Three sets oftest portions were prepared for analysis in each case.

Instrumentation

A Perkin Elmer SCIEX, Model ELAN® DRC II ICP-massspectrometer (Toronto, Canada) was used throughoutthis work. The sample introduction system consisted ofa standard Meinhard nebuliser with a cyclonic spraychamber. Instrumental and data acquisition parame-ters, including the oxide and hydroxide formationlevels, are presented in Table 2.

All quantitative measurements were performedusing instrument software, which used knowledge-driven routines in combination with numerical calcula-tions to perform an automated interpretation of the

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GEOSTANDARDS and



Table 1.Reference materials studied

Name Material Description Source

BE-N Basalt From old volcano near Essey-la-Côte near IWG-GITNancy, France

MY-4 Kimberlite From ultramafic rock composed mainly of Institute of Geology of Ore deposits, of Petrology, serpentine (68%) and calcite (3-29%) Mineralogy and Geochemistry USSR Academy of

Sciences (IGEM), Moscow, USSR

SARM-39 Kimberlite From Kimberley area of the Cape Province, Council for Mineral Technology (MINTEK), Republic of South Africa, consisting of olivine, ilmenite, South Africagarnet, mica and pyroxene which are setin a fine grained micro-crystalline matrix

BHVO-1 Basalt A basaltic lava from Kilauea caldera, Kilauea US Geological Survey (USGS), Denver, USAvolcano, Hawaii

BR Basalt From Essey-la-Côte, near Nancy, France CRPG, France

UB-N Serpentine From the Col des Bagenelles (Vosges), France Association Nationale de la Recherche Technique(ANRT), France

whole spectrum. Several well-known isobaric interfe-rences were programmed and corrections appliedautomatically. An external calibration procedure wasadopted for the analysis.

Materials and reagents

Savillex® pressure decomposition vessels (60 ml),ob ta ined f rom the M/s Sav i l l ex Corpora t ionMinnetonka, MN, USA were used. Electronic grade HF,analytical reagent (AR) grade HClO4, distilled HNO3

and HCl and lithium metaborate (AR grade) wereused during the sample preparation. Millipore purifiedwater (18 MΩ) was used in all investigations. Glassycarbon crucibles (10 ml) were obtained from CARBO-NE of AME, USA for lithium metaborate fusion.

Sample preparation

The following sample preparation procedures wereadopted for the dissolution of samples in the presentinvestigation.

Open acid digestion method: A test portion (0.05g) of the sample was added to PTFE Teflon beakers.Each sample was moistened with a few drops of ultra-pure water. Then, 10 ml of an acid mixture (containing7:3:1 HF-HNO3-HClO4) was added to each sample.Samples were swirled until completely moist. The bea-

kers were then covered with lids and kept overnight fordigestion after adding 1 ml of 5 μg ml-1 Rh solution(to act as an internal standard). The following day, thebeakers were heated on a hot plate at ~ 200 °C forabout 1 hour, the lids were removed and the contentswere evaporated to incipient dryness until a crystallinepaste was obtained. The remaining residues were thendissolved using 10 ml of 1:1 HNO3 and kept on a hotplate for 10 minutes with gentle heat (70 °C) to dissol-ve all suspended particles. Finally, the volume wasmade up to 250 ml with purified water (18 MΩ) andstored in polyethene bottles.

Closed vessel digestion method: A test portion(0.05 g) of sample was added to Savillex® Teflonpressure decomposition vessels. To each sample, 10 mlof an acid mixture (containing 7:3:2 HF-HNO3-HCl)was added. Subsequently, 1 ml of 5 μg ml-1 Rh solu-t ion was added as an internal standard to eachSavillex® vessel. After thorough swirling, the vesselswere tightly closed and kept on a hot plate at ~ 110°C for 48 hours. Following this, the vessels were ope-ned and the contents were evaporated at 200 °C forabout one hour to near dryness. The remaining resi-dues were dissolved by adding 10 ml 1:1 HNO3 andkept on a hot plate for 10 minutes to dissolve all sus-pended particles; the volume was made to 250 mlwith purified water (18 MΩ) and the solution was sto-red finally in polyethene bottles.

Lithium metaborate fusion method: The sample(0.05 g) and 0.25 g of lithium metaborate were wei-ghed together, mixed thoroughly, transferred into aglassy carbon crucible (10 ml), and fused at 1050 °Cfor 30 minutes in a muffle furnace. The crucible wascooled and the separated bead transferred into abeaker with 25 ml of 5% v/v HNO3 solution contai-ning 1 ml of 5 μg ml-1 Rh as internal standard. Thesolution was continuously stirred with a magnetic stirrerfor about 30 minutes for complete dissolution of thebead. The solutions were made up to 250 ml withpurified water (18 MΩ) and filtered to remove anysuspended carbon particles and stored in 60 ml poly-ethene bottles.

Microwave digestion: Test portions (0.05 g) ofsample were transferred into low volume Perfluoro-Alkoxy (PFA) lined vessels that included a safety rupturemembrane. To the sample, 10 ml of an acid mixture(containing 7:3 HF-HNO3) was added along with 1 mlof 5 μg ml-1 Rh to act as internal standard. The vesselswere then closed and mounted in a special outer vessel

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GEOSTANDARDS and



Table 2.Instrumental and data acquisitionparameters of the ICP mass spectrometer

Instrumental parametersRF Power 1100 WArgon gas-flow:

Nebuliser 0.86 l min-1

Auxiliary 1.20 l min-1

Plasma 15 l min-1

Lens voltage 5 VSample uptake rate 0.80 ml min-1

Data acquisition parameters Quantitative modeMeasuring mode Peak hoppingPoint per peak 1Number of sweeps 50Dwell time 50 μsIntegration time 2500 msReplicates 3Internal standard 103Rh a

Oxide and hydroxide formations levels (%)CeO+ 2.046CeOH+ 0.065

a At an overall concentration of 20 ng ml-1.

and placed in the microwave digestion system MARS-5 (CEM Corporation, Matthews, NC, USA). The opera-ting parameters and relevant details are given in Table 2.

After digestion, the contents of each vessel werequantitatively transferred into a Teflon beaker and 1 mlof HClO4 was added to each beaker. The solution wasthen evaporated to incipient dryness. The residue wasthen dissolved in 10 ml 1:1 HNO3 and made to afinal volume of 250 ml with high purity water.

Results and discussion

Interferences, internalstandard and detection limits

Accuracy of the ICP-MS measurements ultimatelydepends on the calibration of the instrument for indivi-

dual elements as most of them suffer from isobaricinterferences from metal oxides, doubly-charged ionsand other common molecular ion interferences. Theisotopes used for measurement were carefully selectedto avoid all the above possible interferences. The iso-topes used for analysis and the potential polyatomicand doubly-charged ion interferences (Date and Gray1985) are listed in Table 3. The oxide formation levelswere monitored using cerium, as this forms the worstcase of oxide ion interference and measurementconditions were optimised for minimum oxide formationlevels (Table 2). Although some elements may formhydroxide molecules (such as BaOH+), the level offormation of this kind of species was normally found tobe < 10% of the oxide formation rates (Date andHutchinson 1987) causing insignificant interferenceeffects. The doubly-charged ions of some REE, Ba andother elements such as Ta, W, etc., have the potential to

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GEOSTANDARDS and



Table 3.Isotopes selected for determination, detection limits andpotential oxide and doubly-charged ion interferences

Isotope Abundance Oxides, hydroxides and polyatomic ion interfering species Detection limit (ng g-1)*

45Sc 100 90Zr2+ 0.00651V 99.76 35ClO 0.00952Cr 83.76 36ArO,36S 0.00859Co 100 43CaO,118Sn2+ 0.00460Ni 26.1 44CaO,120Sn2+ 0.00863Cu 27.81 47TiO,126Te2+ 0.00966Zn 27.9 132Ba2+ 0.0171Ga 39.892 55MnO,142Ce, 142Nd2+ 0.00385Rb 72.15 69GaO,170Yb2+,170Er2+ 0.00488Sr 82.56 72GeO,176Lu2+,176Yb2+,176Hf2+ 0.00389Y 100 73GeO,178Hf2+ 0.00290Zr 51.46 74GeO, 80Hf2+ 093Nb 100 77SeO,186W2+ 0.001133Cs 100 - 0137Ba 11.23 121SbO 0.008139La 99.911 123SbO 0.003140Ce 88.48 124TeO,124SnO 0.004141Pr 100 125TeO 0.002145Nd 8.29 128TeO 0.003147Sm 15.07 130BaOH 0.003151Eu 47.77 135BaO 0.002157Gd 15.68 141PrO 0.002159Tb 100 143NdO 0163Dy 24.97 - 0.002165Ho 100 - 0166Er 33.41 150NdO 0.001169Tm 100 - 0171Yb 14.31 155GdO, 136Ba35Cl 0.001175Lu 97.4 159TbO 0179Hf 13.629 163DyO 0181Ta 99.988 165HoO 0.001206Pb 25.15 - 0.004232Th 100 197AuCl 0.002238U 99 203TlCl 0.002

* On a whole rock basis.

cause interferences at half the parent mass. However,these elements were not usually present at high levelsin the rock samples under investigation and even theformation levels of these species were found to fallbelow the 2% limit that would cause a significanteffect on the estimation of elements such as Ga, Rb, Zr,etc. For example, 71Ga was used to avoid the overlapof 138Ba2+ on 69Ga. To compensate for signal driftdue to changes in nebuliser efficiency, matrix-inducedsuppressions and enhancement effects (Gray 1986)and to minimise mass discrimination and space-chargeeffects, 103Rh was used as a single internal standardas the concentration of this element was found to beinsignificant (< 30 ng g-1) in the samples investigated.Several studies reveal that a single internal standard issufficient for the accurate measurement of trace and

ultra trace elements in geological samples (Yu et al.2001, Balaram and Gnaneshwar 2003).

Solutions containing > 5% v/v acid result in substan-tial erosion of the cone surface and in the geometry ofthe aperture itself (Brenner et al. 1996). Hence, in thepresent investigations, only solutions of 0.02% m/v TDSand < 2% v/v HNO3 were nebulised. Use of relativelysmall quantities of high purity acids and other reagentsled to lower blank values and resulted in sub-ng g-1

detection limits for almost all elements including REEs.The detection limits for all trace elements and REE werefound to be in the range 0.001 to 0.010 ng g-1 andwere nearly the same for all the digestion methodsexcept in the case of fusion digestion. Here, detectionlimits suffered due to higher blank values (Table 3).

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GEOSTANDARDS and



Table 4.Concentrations of REE and trace elements in SARM-39determined by ICP-MS using different digestion methods

SARM-39 (concentrations in μg l-1)

Analyte Closed Open Fusion Microwave Working INAA+ Best values**digestion digestion digestion digestion values*

Sc 13.89 ± 0.49 13.42 ± 0.47 14.37 ± 0.50 12.93 ± 0.45 - 13.44 13.7V 116.23 ± 3.72 122.34 ± 4.40 108.34 ± 4.3 115.06 ± 3.91 109 - 115.5Cr 1204.8 ± 43.3 1291.7 ± 43.9 1264.0 ± 44.2 1266.8 ± 48.1 1300 1360 1274.2Co 68.70 ± 2.60 65.60 ± 2.49 70.68 ± 2.05 70.90 ± 2.62 77 70.6 69.0Ni 942.8 ± 24.5 920.51 ± 34.98 950.79 ± 27.57 933.2 ± 35.4 994 973 936.8Cu 61.91 ± 1.80 58.13 ± 1.56 56.82 ± 2.22 60.91 ± 1.77 58 - 59.4Zn 75.19 ± 2.71 70.18 ± 2.60 60.23 ± 2.11 72.30 ± 1.74 70 - 69.5Ga 20.26 ± 0.77 19.47 ± 0.74 17.08 ± 0.63 19.45 ± 0.99 10 - 19.1Rb 52.87 ± 2.06 50.14 ± 1.9 47.26 ± 1.80 52.82 ± 2.17 52 51 50.8Sr 1514.3 ± 49.9 1445.9 ± 44.8 1370.0 ± 46.5 1475.2 ± 57.5 1400 1510 1451.4Y 17.20 ± 0.77 15.94 ± 0.69 15.54 ± 0.78 16.85 ± 0.57 17 16.1 16.4Zr 226.65 ± 7.71 185.44 ± 7.51 240.44 ± 6.35 262.62 ± 9.19 239 240 243.2Nb 110.00 ± 3.19 104.00 ± 3.64 113.50 ± 3.97 182.16 ± 4.74 110 - 109.2Cs 2.72 ± 0.11 3.90 ± 0.13 3.46 ± 0.13 3.96 ± 0.11 - 3.54 3.51Ba 1651.0 ± 69.3 1700.9 ± 54.4 1698.0 ± 66.2 1009.5 ± 50.4 1700 1640 1683.3La 87.72 ± 3.073 86.83 ± 3.13 89.87 ± 3.77 92.52 ± 3.24 - 88.6 89.2Ce 189.09 ± 7.19 180.33 ± 6.49 169.82 ± 6.62 192.51 ± 7.51 85 185 182.9Pr 21.50 ± 0.77 21.36 ± 0.81 20.11 ± 0.84 22.89 ± 0.96 - 21 21.5Nd 81.10 ± 2.35 81.57 ± 3.43 80.50 ± 2.90 85.49 ± 3.93 - 78 82.2Sm 12.29 ± 0.36 12.04 ± 0.49 11.53 ± 0.45 13.06 ± 0.51 - 12 12.2Eu 3.18 ± 0.16 3.20 ± 0.09 3.31 ± 0.13 3.38 ± 0.12 - 3.03 3.14Gd 8.70 ± 0.31 8.29 ± 0.32 8.29 ± 0.41 9.01 ± 0.46 - 7.2 8.58Tb 0.98 ± 0.03 0.95 ± 0.03 1.01 ± 0.04 1.00 ± 0.06 - 0.84 0.99Dy 4.18 ± 0.18 4.20 ± 0.17 4.67 ± 0.17 4.20 ± 0.24 - 4 4.23Ho 0.64 ± 2.52 0.58 ± 0.02 0.62 ± 0.03 0.64 ± 0.02 - 0.67 0.62Er 1.57 ± 0.06 1.42 ± 0.08 1.50 ± 0.07 1.59 ± 0.05 - 1.4 1.52Tm 0.19 ± 0.01 0.16 ± 0.01 0.20 ± 0.01 0.18 ± 0.01 - 0.16 0.18Yb 1.04 ± 0.06 0.87 ± 0.04 1.01 ± 0.04 0.96 ± 0.05 - - 0.98Lu 0.12 ± 0.01 0.11 ± 0.01 0.14 ± 0.01 0.12 ± 0.00 - 0.119 0.13Hf 5.68 ± 0.39 4.04 ± 0.21 5.74 ± 0.29 5.60 ± 0.28 - 5.8 5.02Ta 7.46 ± 0.46 3.54 ± 0.17 7.14 ± 0.28 3.63 ± 0.20 - 7.44 7.3Pb 8.38 ± 0.55 4.92 ± 0.25 3.79 ± 0.19 11.58 ± 0.58 - - 9.98Th 10.54 ± 0.59 8.90 ± 0.45 9.82 ± 0.36 10.00 ± 0.32 - 9.1 9.75U 2.55 ± 0.13 2.23 ± 0.11 2.43 ± 0.10 2.88 ± 0.11 - 2.35 2.52

Number of replicates = 3, ± standard deviation. * Govindaraju (1994). ** Best value from this work.+ Korotev (1996).

Calibration

In order to overcome matrix effects that are gene-ral ly observed during the analys is of geologicalsamples, several methods can be used. Dilution of thesample, use of an internal standard and matrix-mat-ched reference samples for calibration, are some ofthe effective ways for this purpose. Knowledge of thesample composition and the sample dissolution helpsto predict potential spectral interferences. The majorand minor elemental concentrations will affect thesignals of trace elements. The isotopes chosen for mea-suring different elements in this work were free frompotential polyatomic, isobaric and doubly-charged ioninterferences. Hence, BE-N was chosen as a calibratorbecause the major and minor element composition ofBE-N is similar to kimberlitic samples, especially with

respect to Mg, Ca, Mn and Fe. These elements werefound to influence the ICP-MS signals of trace elementsto a significant extent. BE-N was dissolved in the sameway as the other samples.

Different dissolution techniques

Thirty-four trace elements, including all naturallyoccurring REEs, were determined by ICP-MS for the twokimberlitic reference materials, SARM-39 and MY-4together with three additional well-characterised refe-rence materials, BHVO-1, UB-N and BR-1. The resultspresented in Tables 4 to 8 show the mean and stan-dard deviation of triplicate determinations by each ofthe four digestion methods. The measured concentra-tion of each element was compared with availablereference values (Govindaraju 1994, Korotev 1996) for

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GEOSTANDARDS and



Table 5.Concentrations of REE and trace elements in MY-4 determined by ICP-MS by different digestion methods

MY-4 (concentrations in μg l-1)

Analyte Closed Open Fusion Microwave Working Best values**digestion digestion digestion digestion values*

Sc 10.74 ± 0.43 9.02 ± 0.32 10.10 ± 0.39 9.06 ± 0.32 9.1 9.72V 81.06 ± 2.84 85.00 ± 2.98 80.70 ± 2.91 83.13 ± 3.24 47 82.5Cr 673.90 ± 24.26 660.00 ± 25.08 675.0 ± 23.6 663.46 ± 23.22 680 666.5Co 73.07 ± 2.85 71.98 ± 2.45 70.01 ± 2.45 74.07 ± 2.37 73 72.3Ni 1096.6 ± 35.0 1212.0 ± 42.4 1010.2 ± 38.38 1050.98 ± 39.94 1060 1073.8Cu 33.65 ± 1.14 1.88 ± 0.05 36.74 ± 1.18 35.51 ± 1.21 35 34.1Zn 58.10 ± 2.21 52.31 ± 1.88 60.98 ± 2.26 59.14 ± 2.19 63 59.4Ga 5.72 ± 0.23 6.32 ± 0.16 6.32 ± 0.23 5.52 ± 0.23 6.8 5.91Rb 22.61 ± 0.59 17.72 ± 0.51 18.21 ± 0.76 18.41 ± 0.79 - 19.2Sr 266.00 ± 10.37 272.0 ± 9.5 275.02 ± 0.11 286.77 ± 10.04 280 274.9Y 10.42 ± 0.30 8.21 ± 0.31 8.59 ± 0.34 9.43 ± 0.56 9.1 9.16Zr 76.32 ± 3.21 67.44 ± 2.63 80.20 ± 3.21 79.21 ± 2.77 83 78.5Nb 61.67 ± 2.23 65.72 ± 2.76 45.86 ± 1.93 68.64 ± 2.20 38 60.5Cs 0.92 ± 0.03 0.88 ± 0.04 0.85 ± 0.03 0.84 ± 0.02 - 0.87Ba 245.00 ± 9.31 246.7 ± 9.6 254.2 ± 5.3 253.87 ± 6.35 250 249.9La 41.96 ± 1.68 38.85 ± 1.52 41.67 ± 1.75 42.73 ± 1.79 - 41.3Ce 77.74 ± 3.27 72.28 ± 3.69 78.29 ± 3.52 78.77 ± 3.62 - 76.8Pr 8.14 ± 0.46 7.72 ± 0.31 7.52 ± 0.26 8.48 ± 0.33 - 7.97Nd 29.11 ± 1.02 26.46 ± 1.08 28.39 ± 1.02 29.20 ± 1.46 - 28.3Sm 4.33 ± 0.16 4.81 ± 0.20 4.32 ± 0.17 4.29 ± 0.19 - 4.44Eu 1.07 ± 0.05 1.02 ± 0.05 1.04 ± 0.04 1.09 ± 0.05 - 1.06Gd 3.36 ± 0.14 3.68 ± 0.15 3.56 ± 0.16 3.36 ± 0.13 - 3.49Tb 0.43 ± 0.02 0.40 ± 0.02 0.41 ± 0.02 0.41 ± 0.03 - 0.41Dy 2.21 ± 0.12 1.71 ± 0.08 2.23 ± 0.11 2.02 ± 0.14 - 1.98Ho 0.40 ± 0.02 0.35 ± 0.02 0.38 ± 0.02 0.35 ± 0.02 - 0.37Er 0.94 ± 0.05 0.95 ± 0.05 0.99 ± 0.04 0.92 ± 0.05 - 0.95Tm 0.11 ± 0.01 0.10 ± 0.00 0.10 ± 0.00 0.13 ± 0.01 - 0.11Yb 0.61 ± 0.04 0.58 ± 0.03 0.59 ± 0.03 0.61 ± 0.04 - 0.60Lu 0.13 ± 0.01 0.10 ± 0.00 0.12 ± 0. 0.10 ± 0.01 - 0.11Hf 4.69 ± 0.20 1.71 ± 0.09 4.48 ± 0.18 5.49 ± 0.25 - 4.89Ta 2.66 ± 0.11 4.54 ± 0.18 4.98 ± 0.21 4.54 ± 0.18 - 4.69Pb 4.24 ± 0.17 3.62 ± 0.16 1.57 ± 0.06 4.65 ± 0.16 - 4.17Th 7.24 ± 0.26 5.27 ± 0.19 7.21 ± 0.26 7.41 ± 0.25 - 6.78U 2.26 ± 0.09 1.18 ± 0.05 2.31 ± 0.09 2.17 ± 0.09 - 1.98

Number of replicates = 3, ± standard deviation. * Govindaraju (1994). ** Best value from this work.

the two kimberlitic reference materials as well as forthe three other reference materials.

Alkali fusion with LiBO2 is a useful alternative tech-nique that is capable of the decomposition of refractoryminerals (Potts 1987, Chao et al . 1992, Jarvis et al.1992). In this work, all samples were fused with LiBO2

followed by treatment with HNO3 and further dilutionof the dissolved bead solution to 250 ml to reduce thetotal dissolved solids to less than 0.12% in the finalsolution. This is very effective when the number ofsamples taken in a batch is reasonably small (twelve inthe present study). Although fusion with LiBO2 is apowerful decomposition technique for geological mate-rial by ICP-MS, this method precludes the determinationof volatile elements such as Sn, Sb, Zn, Pb due to thehigh fusion temperature (1050 °C). Jarvis et al. (1992)

and Totland et al. (1992) encountered a similar pro-blem during the analysis of these reference materialsand the recovery of Pb and Zn was very poor in allcases. The error limit when compared with the avai-lable data exceeds ± 84% and ± 13% for Pb and Znrespectively. The use of a high purity fusion flux resultedin extremely low blanks and detection limits did notsuffer much when compared to the other digestiontechniques. However, one major disadvantage of thismethod is that it is not possible to determine Li and B inthe samples for months following the analysis of fusionsolutions by ICP-MS because of the memory effects ofthese elements in the sample nebulisation system.

Closed digestion in Savillex® Teflon beakers on ahot plate is a simple and convenient way to decomposegeological samples for analysis and the results showed

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GEOSTANDARDS and



Table 6.Concentrations of REE and trace elements in UB-N determined by ICP-MS by different digestion methods

UB-N (concentrations in μg l-1)

Analyte Working values* Closed digestion Open digestion Fusion digestion Microwave digestion

Sc 13 13.31 ± 0.67 12.96 ± 0.41 15.00 ± 0.75 15.67 ± 0.70V 75 64.02 ± 2.88 70.14 ± 2.24 82.06 ± 4.10 82.06 ± 2.63Cr 2300 2278.2 ± 79.7 2292.5 ± 52.7 2310.6 ± 90.1 2268.3 ± 72.5Co 100 95.79 ± 93.3 95.57 ± 2.48 94.75 ± 4.71 88.55 ± 2.83Ni 2000 1986.3 ± 93.3 1990.2 ± 49.8 2130.3 ± 74.5 2051.2 ± 80.0Cu 28 27.8 ± 1.0 24.25 ± 0.68 32.12 ± 0.39 27.52 ± 1.07Zn 85 87.39 ± 3.41 82.3 ± 2.8 83.41 ± 4.34 86.26 ± 2.93Ga 3 2.58 ± 0.07 2.25 ± 0.04 3.7 ± 0.16 2.35 ± 0.04Rb 4 5.89 ± 0.14 3.50 ± 0.10 3.4 ± 0.11 4.21 ± 0.08Sr 9 8.23 ± 0.17 8.56 ± 0.14 9.00 ± 0.32 8.27 ± 0.23Y 2.5 2.36 ± 0.05 2.17 ± 0.11 2.50 ± 0.09 2.45 ± 0.07Zr 4 3.01 ± 0.08 2.94 ± 0.16 4.12 ± 0.16 3.00 ± 0.08Nb 0.05 0.1 ± 0.0 0.09 ± 0.00 0.1 ± 0.0 0.09 ± 0.00Cs 10 9.25 ± 0.32 11.09 ± 0.51 10.88 ± 0.23 10.40 ± 0.56Ba 27 26.37 ± 0.74 26.12 ± 0.94 28.43 ± 0.71 30.35 ± 1.73La 0.35 0.3 ± 0.01 0.3 ± 0.01 0.33 ± 0.01 0.34 ± 0.02Ce 0.8 0.9 ± 0.03 0.92 ± 0.03 0.9 ± 0.05 0.83 ± 0.06Pr 0.12 0.15 ± 0.01 0.14 ± 0.00 0.12 ± 0.00 0.13 ± 0.01Nd 0.6 0.65 ± 0.02 0.64 ± 0.02 0.63 ± 0.02 0.55 ± 0.04Sm 0.2 0.27 ± 0.01 0.22 ± 0.01 0.24 ± 0.01 0.23 ± 0.02Eu 0.08 0.08 ± 0.00 0.08 ± 0.00 0.09 ± 0.00 0.08 ± 0.01Gd 0.3 0.27 ± 0.01 0.27 ± 0.02 0.32 ± 0.02 0.30 ± 0.02Tb 0.06 0.07 ± 0.00 0.05 ± 0.00 0.06 ± 0.00 0.05 ± 0.00Dy 0.38 0.41 ± 0.01 0.39 ± 0.03 4 ± 0.26 0.38 ± 0.02Ho 0.09 0.09 ± 0.01 0.09 ± 0.06 0.09 ± 0.01 0.08 ± 0.01Er 0.28 0.28 ± 0.02 0.26 ± 0.02 0.28 ± 0.02 0.27 ± 0.02Tm 0.049 0.05 ± 0.00 0.04 ± 0.00 0.03 ± 0.00 0.04 ± 0.00Yb 0.28 0.29 ± 0.02 0.29 ± 0.17 0.25 ± 0.02 0.28 ± 0.01Lu 0.045 0.05 ± 0.00 0.04 ± 0.00 0.03 ± 0.00 0.04 ± 0.00Hf 0.01 0.05 ± 0.00 0.03 ± 0.00 0.01 ± 0.00 0.02 ± 0.00Ta 0.02 0.06 ± 0.00 0.05 ± 0.00 0.02 ± 0.00 0.01 ± 0.00Pb 13 11.59 ± 0.29 12.23 ± 0.62 4.82 ± 0.23 12.28 ± 0.39Th 0.07 0.09 ± 0.01 0.07 ± 0.00 0.06 ± 0.00 0.08 ± 0.00U 0.07 0.08 ± 0.00 0.05 ± 0.00 0.08 ± 0.00 0.05 ± 0.00

Number of replicates = 3, ± standard deviation. * Govindaraju (1994).

good agreement with the available data. Most of thedata demonstrate for SARM-39 an accuracy of ≤ 4%.Compared to Govindaraju (1994), values for Ga, Ceand Pb differed by +102%, +117% and -66% respec-tively, although for Ce our results agreed with INAAresults by Korotev (1996). Zirconium and Hf recoverywas reasonably good by closed digestion. Figures 1and 2 show the deviation of data generated by thedifferent digestion techniques from working values,where available. Overall, closed digestion is quiteeffective for the digestion of kimberlitic samples formost of the trace elements, including REE, for geoche-mical studies of these rocks.

The microwave digestion technique has been usedto digest rock samples in recent years in conjunctionwith ICP-MS (Jarvis et al. 1992, Totland et al. 1995,

Yoshida et al. 1996, Balaram and Gnaneshwar 2003).Compared to closed vessel digest ion, microwavedigestion is rapid, with the digestion completed withinone hour or so. However, Jarvis et al. (1992) found thatmicrowave digestion did not always allow the comple-te recovery of elements such as Zr and Hf, especiallywhen these elements were present in refractory mineralphases. In the present study, microwave digestion gavegood recoveries for Zr – almost 90% for the samplesanalysed. The recoveries of the REEs were acceptablewhen compared with the working values; this may bedue to the high pressure combined with the use of theHF-HClO4-HNO3 acid mixture.

Open acid digestion of rock samples is the mostconvenient method for trace and REE determination.Open acid digestion with HF, HNO3 and HClO4, at an

2 6 8

GEOSTANDARDS and



Table 7.Concentrations of REE and trace elements in BHVO-1 determined by ICP-MS by different digestion methods

BHVO-1 (concentrations in μg l-1)


Sc 31.8 24.32 ± 0.87 29.07 ± 1.19 25.04 ± 0.88 31.29 ± 1.09V 317 314.2 ± 10.9 336.8 ± 5.7 329.1 ± 11.5 298.0 ± 9.5Cr 289 288.3 ± 10.2 299.0 ± 6.2 277.5 ± 10.5 285.5 ± 14.2Co 45 44.04 ± 1.62 43.76 ± 1.53 43.57 ± 1.48 45.00 ± 1.53Ni 121 121.9 ± 3.0 121.9 ± 5.1 201.5 ± 7.9 222.2 ± 7.8Cu 136 132.5 ± 3.4 125.6 ± 3.1 130.0 ± 4.8 136.1 ± 5.2Zn 105 105.8 ± 3.0 107.9 ± 3.8 43.32 ± 1.51 99.11 ± 4.06Ga 0.21 1.02 ± 0.05 0.32 ± 0.01 0.08 ± 0.00 1.7 ± 0.07Rb 11 13.02 ± 0.59 9.5 ± 0.3 9.1 ± 0.3 10.1 ± 0.4Sr 403 375.0 ± 18.0 400.7 ± 15.2 441.1 ± 15.4 397.3 ± 14Y 27.6 27.48 ± 1.42 26.78 ± 0.93 25.21 ± 1.08 27.64 ± 14.69Zr 179 168.3 ± 4.2 154.2 ± 6.9 173.9 ± 8.3 156.7 ± 5.6Nb 19 18.54 ± 0.46 21.00 ± 0.88 16.86 ± 0.94 19.88 ± 0.75Cs 0.13 0.541 ± 0.03 0.12 ± 0.00 0.13 ± 0.00 0.13 ± 0.00Ba 139 104.0 ± 4.0 121.0 ± 3.4 140.3 ± 5.3 118.6 ± 3.0La 15.8 16.55 ± 0.57 15.28 ± 0.59 14.83 ± 0.50 15.98 ± 0.44Ce 39 41.04 ± 1.14 38.30 ± 1.95 35.95 ± 1.36 39.37 ± 1.14Pr 5.7 5.71 ± 0.16 5.40 ± 0.28 5.21 ± 0.23 5.77 ± 0.20Nd 25.2 25.75 ± 0.74 24.37 ± 1.14 23.29 ± 1.11 25.18 ± 1.28Sm 6.2 6.2 ± 0.16 5.93 ± 0.28 5.70 ± 0.12 6.20 ± 0.33Eu 2.06 2.02 ± 0.06 1.94 ± 0.08 1.78 ± 0.05 2.02 ± 0.20Gd 6.4 5.9 ± 0.22 5.37 ± 0.29 6.02 ± 0.32 5.74 ± 1.20Tb 0.96 0.96 ± 0.03 0.90 ± 0.48 0.91 ± 0.04 0.96 ± 0.03Dy 5.2 5.32 ± 0.18 5.13 ± 0.26 4.79 ± 0.24 5.29 ± 0.26Ho 0.99 1.02 ± 0.03 0.97 ± 0.52 0.94 ± 0.04 0.98 ± 0.04Er 2.4 2.46 ± 0.05 2.41 ± 1.29 2.20 ± 0.11 2.41 ± 0.12Tm 0.33 0.34 ± 0.02 0.35 ± 0.01 0.32 ± 0.01 0.36 ± 0.02Yb 2.02 2.151 ± 0.13 1.94 ± 0.09 1.73 ± 0.07 2.02 ± 0.09Lu 0.291 0.27 ± 0.01 0.26 ± 0.01 0.28 ± 0.01 0.29 ± 0.01Hf 4.38 6.16 ± 0.29 4.25 ± 0.17 4.1 ± 0.14 11.18 ± 0.72Ta 1.23 1.21 ± 0.05 2.94 ± 0.12 0.65 ± 0.02 2.26 ± 0.11Pb 2.6 2.00 ± 0.07 3.71 ± 0.08 2.24 ± 0.08 3.27 ± 0.18Th 1.08 1.20 ± 0.04 1.46 ± 0.08 1.34 ± 0.06 1.42 ± 0.05U 0.42 0.60 ± 0.01 0.47 ± 0.02 0.6 ± 0.03 0.47 ± 0.01


elevated temperature fol lowed by evaporation toremove silica and fluoride enabled most concentratedsolutions to be analysed by ICP-MS. The recovery for Zrwas very low. The error limit was more than 20%,which shows the inability of acid attack to recoverquantitatively Zr. Most of the values are in the range ±5% when compared with the available working valuesfor both SARM-39 and MY-4, which shows the efficien-cy of a mixed acid open digestion. However, closedvessel digestion is more effective for recovery of REE,especially, the heavy REE (HREE) (Figure 5).

Precision and accuracy

Overall, an accuracy of better than ± 5% wasobtained for most determinations with a precision ofbetter than ± 6% RSD. The accuracy of the results

presented in this study can be seen in Tables 4-8 andFigures 1-2. However, precision was highly dependenton the abso lu te concen t ra t ion in the mate r ia l .Determinations made close to the ICP-MS detectionlimit gave the poorest precision, as expected, whilemore consistent results were obtained for elements athigher concentrations with many yielding RSDs of bet-ter than ± 5%. Normalising the REE data to chondritemeteorites, emphasises any irregularities in the normalisedpatterns. Figures 3 and 4 show chondrite-normalisedREE plots for all the reference materials by all thedigestion techniques. The overlap of symbols for a fewelements by all the digestion techniques illustrates theexcellent inter-method reproducibility of determinations.Data obtained for both the kimberlitic reference mate-rials matched very well with working values whereveravailable (except for Ce in SARM-39 and V and Nb in

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GEOSTANDARDS and



Table 8.Concentrations of REE and trace elements in BR-1 determined by ICP-MS by different digestion methods (μg l-1)


Sc 25 24.31 ± 0.78 24.23 ± 0.87 22.11 ± 0.77 22.01 ± 0.73V 235 236.2 ± 8.3 231.7 ± 8.1 230.6 ± 8.3 237.5 ± 8.1Cr 380 377.8 ± 14.7 381.9 ± 14.5 376.2 ± 13.2 371.6 ± 8.1Co 52 56.67 ± 1.47 55.22 ± 1.88 50.21 ± 1.91 57.36 ± 1.66Ni 260 265.8 ± 10.4 261.2 ± 10.2 255.3 ± 9.7 268.2 ± 9.1Cu 72 72.04 ± 2.74 67.17 ± 2.82 73.95 ± 2.51 73.71 ± 3.83Zn 160 159.1 ± 7.2 151.2 ± 5.3 152.8 ± 5.8 150.0 ± 6.3Ga 19 18.18 ± 0.69 17.21 ± 0.89 14.60 ± 0.61 17.59 ± 0.62Rb 47 47.13 ± 1.60 46.42 ± 1.63 46.22 ± 2.22 47.62 ± 1.71Sr 1320 1332.6 ± 33.3 1341.9 ± 56.3 1370.0 ± 61.6 1326.4 ± 45.1Y 30 30.43 ± 0.76 29.87 ± 1.34 24.31 ± 1.02 30.25 ± 1.15Zr 260 258.0 ± 7.5 250.6 ± 11.3 259.7 ± 12.0 236.7 ± 9.7Nb 98 103.7 ± 3.7 102.1 ± 3.6 93.81 ± 4.03 219.1 ± 5.5Cs 0.8 0.88 ± 0.03 0.88 ± 0.03 0.67 ± 0.03 0.87 ± 0.03Ba 1050 1042.8 ± 28.5 1079.1 ± 45.3 1088.3 ± 45.3 1057.5 ± 25.4La 82 80.84 ± 2.91 82.13 ± 2.14 71.17 ± 3.14 81.94 ± 3.11Ce 151 151.9 ± 5.8 152.7 ± 4.4 147.7 ± 5.2 153.2 ± 5.9Pr 17 17.29 ± 0.78 17.52 ± 0.67 15.51 ± 0.47 17.52 ± 0.65Nd 65 67.65 ± 3.32 67.37 ± 3.37 58.51 ± 2.05 67.24 ± 0.65Sm 12.2 12.27 ± 0.59 12.20 ± 0.37 11.36 ± 0.40 12.17 ± 3.50Eu 3.6 3.60 ± 0.13 3.65 ± 0.13 3.00 ± 0.10 3.60 ± 0.13Gd 9.7 9.70 ± .037 9.61 ± 0.35 9.23 ± 0.31 9.75 ± 0.33Tb 1.3 1.31 ± 0.05 1.32 ± 0.05 1.10 ± 0.04 1.33 ± 0.07Dy 6.4 6.64 ± 0.37 6.40 ± 0.32 6.1 ± 0.3 6.44 ± 0.42Ho 1.1 1.14 ± 0.06 1.09 ± 0.06 0.99 ± 0.077 1.12 ± 0.08Er 2.56 2.62 ± 0.13 2.60 ± 0.015 2.26 ± 0.15 2.63 ± 0.11Tm 0.34 0.34 ± 0.02 0.34 ± 0.19 0.31 ± 0.02 0.34 ± 0.06Yb 1.8 1.82 ± 0.11 1.85 ± 0.08 1.85 ± 0.09 1.87 ± 0.10Lu 0.25 0.25 ± 0.01 0.24 ± 0.01 0.24 ± 0.01 0.24 ± 0.01Hf 5.6 5.64 ± 0.32 5.67 ± 0.26 5.4 ± 0.3 6.30 ± 0.27Ta 6.2 5.75 ± 0.26 10.71 ± 0.60 6.30 ± 0.26 5.41 ± 0.28Pb 5 4.18 ± 0.26 4.17 ± 0.25 3.16 ± 0.13 5.58 ± 0.34Th 11 11.13 ± 0.40 10.38 ± 0.52 10.69 ± 0.34 10.67 ± 0.35U 2.5 2.50 ± 0.08 2.40 ± 0.12 2.53 ± 0.13 2.50 ± 0.09


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GEOSTANDARDS and



Figure 1. Deviation of values obtained in these studies from the working values.

Dev

iatio

n fr

om w

orki

ng v

alu

es (%

)

Figure 2. Deviation of values obtained in these studies from the working values.

Dev

iatio

n fr

om w

orki

ng v

alu

es (%

)

SARM-39

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

Sc V Cr Co Ni Cu Zn GaRb Sr Y Zr Nb Cs Ba La Ce Pr Nd SmEu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

INAA

Closed Digestion

Open Digestion

Fusion Digestion

Microwave Digestion

-10% +10%

Working Values

MY-4

-100

-80

-60

-40

-20

0

20

40

60

80

100

Sc V Cr Co Ni Cu Zn Ga Rb Sr Y Zr Nb Cs Ba La Ce Pr NdSmEu GdTb Dy HoEr TmYb Lu Hf Ta Pb Th U

Closed Digestion

Open digestion Fusion digestion

Microwave digestion

-10% -10%

Working values

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GEOSTANDARDS and



Figure 3. Rock/chondrite

plots for MY-4 and SARM-39

from open digestion, closed

digestion, microwave

digestion and fusion

digestion (chondite values

from McDonough and

Sun 1995).

Rock

/cho

ndri

te

REE

REE

REE

REE

REE

Rock

/cho

ndri

te

BHVO-1

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Certified Values

Closed Digestion

Open Digestion

Fusion Digestion

Microwave Digestion

BR-1

1

10

100

1000


Certified values

Closed digestion

Open digestion

Fusion digestion

Microwave digestion

UB-N

0

0.5

1.0

1.5

2.0

2.5


Closed digestion

Open digestion

Fusion digestion

Microwave digestion

Figure 4. Rock/chondrite

plots of BHVO-1, BR-1 and

UB-N from open digestion,

closed digestion, microwave

digestion and fusion

digestion along with

certified values.

Rock

/cho

ndri

teRo

ck/c

hond

rite

Rock

/cho

ndri

te

MY-4

1

10

100

1000


Closed Digestion

Open Digestion

Fusion Digestion

Microwave Digestion

SARM-39

1

10

100

1000


Closed Digestion

Open Digestion

Fusion Digestion

Microwave Digestion

MY-4). The smooth chondrite-normalised plots obtai-ned for SARM-39 and MY-4 (Figure 3) as well asthe other RMs i.e., BHVO-1, BR and UB-N (Figure 4)further enhance the credibility of the reported datafor SARM-39 and MY-4. Three other data sets forthe mafic-ultramafic rock reference samples BHVO-1(basalt ) , BR (basalt ) and UB-N (serpentini te) arepresented in Tables 6 to 8. Very good agreementexis ts between these data and reference valueswherever available. There is also close agreementwith the values reported by INAA (Korotev 1996,Jochum et al. 2005) for SARM-39. The consistencyof the values obtained by the four different diges-t ion techniques suggests that the t race and REEvalues reported for the two kimberl i t ic referencematerials possess the required accuracy and preci-sion, and are suitable for use in future analyticalgeochemical investigations.

Conclusions

New REE and trace element data are reported inthis study on two kimberlitic reference material, deter-mined by ICP-MS. These data compare well with avai-lable reference values. The error limits were found tobe within 5% for most of the elements by all the diges-tion techniques. The accuracy and precision achieved(< 6% RSD in most cases) suggests that both trace andREE data are suitable for geochemical applications.Results of four different digestion procedures showedthat geological samples should be digested using dif-ferent digestion techniques depending on individualsample compositions. This study illustrates the impor-tance of the dissolution step when analysing geologi-cal materials by ICP-MS. For kimberlitic rocks, closeddigestion is suitable for determining geochemicallyimportant elements. However, no single decomposition

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GEOSTANDARDS and



Recovery Chart for MY-4-25

-20

-15

-10

-5

0

5

10

15


Recovery Chart For SARM-39-25.0

-20.0

-15.0

-10.0

-5.0

0.0

5.0


Figure 5. Recovery chart of REE for MY-4 and SARM-39.

Element

Element

Dev

iatio

n of

op

en f

rom

clo

sed

dig

estio

n

Dev

iatio

n of

op

en f

rom

clo

sed

dig

estio

n

protocol will allow the measurement of all trace ele-ments in all types of geological samples by ICP-MS.These new data will be useful in the study of the geo-chemistry of kimberlites as well as in diamond explora-tion. Results will also contribute to the database uponwhich recommended values can either be updated orassigned, especially for the REE. This work will be use-ful for better constraining elemental abundances inthese important reference materials.

Acknowledgements

The authors are grateful to Dr. V.P. Dimri, Director,National Geophysical Research Institute, for permissionto publish this paper. The first author also thanks CSIRfor provision of a Research Intern Fellowship. Theauthors are grateful to editor in-chief Dr. P.J. Potts andthree anonymous reviewers for their valuable com-ments and suggestions which helped to improve themanuscript.

References

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Chao T. and Sanzolone R.F. (1992)Decomposition techniques. Journal of GeochemicalExploration, 44, 65-106.

Garbe-Schönberg C.D. (1993)Simultaneous determination of thirty-seven trace elementsin twenty-eight international rock standards by ICP- MS.Geostandards Newsletter, 17, 81-97.

Date A.R. and Gray A.L. (1985)Determination of trace element analysis in geologicalsamples by inductively coupled plasma-mass spectrometry. Spectrochim Acta, 40B, 115-122.

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McDonough W.F. and Sun S.S. (1995)The composition of the earth. Chemical Geology, 120,223-253.

Potts P.J. (1987)A handbook of silicate rock analysis. Blackie (London),621pp.

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New REE and Trace Element Data on Two Kimberlitic Reference Materials by ICP-MS

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