Standard Rocks Research Articles

Tungsten isotopic analysis on six geochemical reference materials using multiple collector-ICP-mass spectrometry coupled with a rhenium-external correction technique

We have measured 182W/183W, 184W/183W, and 186W/183W ratios for two W standard solutions (NIST-3163 and JMC-22841) and six geochemical reference materials (JB-3, JA-3, JR-1, JCh-1, JMn-1, and HSD), by means of multiple collector-ICP-mass spectrometry (MC-ICP-MS). In this study, a Re-external correction technique was employed to detect possible isotopic fractionations of W through a sample formation sequence. In order to obtain further reliable and traceable isotopic data, we introduced the newly defined mass bias factor (γ) into the exponential law. When the γ value was optimized to 1.151 ± 0.017, resulting 182W/183W, 184W/183W, and 186W/183W ratios were 1.85186 ± 0.00008, 2.14105 ± 0.00008, and 1.987606 ± 0.000002, respectively. Reproducibility in the W isotopic ratio measurements was better than 0.05‰ for all the ratios, demonstrating that no significant deterioration in the analytical uncertainties was found from the data obtained with the conventional correction technique using the exponential law. In order to minimize possible isotopic fractionations through the chemical separation and purification processes, great care must be taken in the recovery of W. We have estimated the total recovery of W through the chemical decomposition and separation procedures by repeating the analysis of W abundance from a rhyolite standard rock sample (JR-1), and the resulting W recovery was 97.8 ± 6.5% (n = 5). Based on the isotopic data obtained through the ion chromatographic separation revealed that the isotopic fractionations of W are less than 0.02‰, and this is almost comparable to the analytical precision achieved here. No significant variation in 182W/183W ratio due to radioactive decay of 182Hf could be found for all the samples analyzed in this study. Despite the absence of radioactive isotopic variation of 182W/183W ratio, resulting 182W/183W, 184W/183W, and 186W/183W ratios for W reagents and geochemical reference materials revealed that W suffered from mass-dependent fractionation through the sample formation. The W isotopic ratios of JMC-22841 were 0.06‰ amu−1 lighter than those of NIST-3163. In contrast, the W isotopic ratios collected from hot spring deposit (HSD) were 0.15‰ amu−1 heavier than those of NIST-3163, which show that the overall degrees of isotopic variations were 0.21‰ amu−1. These data demonstrate clearly that W isotopes can be used as a new tool for stable isotope geochemistry.

Isotopic analysis of lead in sub-nanogram quantities by TIMS using a202Pb–205Pb spike

We present a method for isotopic analyses of Pb in sub-nanogram quantities by thermal ionization mass spectrometry with fractionation correction using a 202Pb–205Pb spike. The procedure is simple, fast, easy to automate, and requires only one analysis of Pb per sample to acquire both fractionation-corrected Pb isotopic ratios and Pb concentration. The procedure is evaluated by analysis of multiple loads of NIST Pb isotopic standards SRM-981 and SRM-982, and Pb separated from USGS standard rock BCR-1 and chondrite Bruderheim, with the amount of Pb per load between 0.05–3.0 × 10−9 g. The data have been corrected using both the double spike (DS) fractionation correction described here, as well as by conventional external normalization (EN) procedures, thus providing a direct comparison between the correction methods on exactly the same analytical runs. The enhancement in precision and reproducibility achieved by DS normalization varies with the quantity of Pb analysed. For amounts of Pb of less than 0.2 ng, the improvement in precision and reproducibility of 207Pb/206Pb ratios is small but becomes more substantial with increasing sample size: 3–10 times lower within-run errors, and 2–3 times better reproducibility are obtained for 0.5–3.0 ng loads. Even greater enhancement in precision and reproducibility is achieved for the 208Pb/206Pb ratios, at twice the relative mass difference between isotopes. The advantage of DS for the 204Pb/206Pb ratio is, however, much smaller. This indicates that factors other than fractionation control precision and accuracy of isotopic ratios measured at the ion beam levels below 2–3 × 10−13 A—the intensity typically observed for 204Pb in all samples smaller than 2–3 ng, and for all Pb isotopes in samples smaller than ca. 0.1 ng. The method described here is applicable to high-precision Pb–Pb and U–Pb dating of milligram quantities of meteorites and their components, and single, microgram-size grains of zircon and other U-bearing minerals. The technique described here had been used for dating early solar system materials (Ca–Al rich inclusions and primitive achondrites) containing 0.01–0.3 ng of Pb per fraction, and yielded Pb–Pb isochrons with the age error of 0.16–0.33 million years, which was previously unattainable for such small samples.

Modified ion exchange separation for tungsten isotopic measurements from kimberlite samples using multi-collector inductively coupled plasma mass spectrometry

Tungsten isotope composition of a sample of deep-seated rock can record the influence of core-mantle interaction of the parent magma. Samples of kimberlite, which is known as a carrier of diamond, from the deep mantle might exhibit effects of core-mantle interaction. Although tungsten isotope anomaly was reported for kimberlites from South Africa, a subsequent investigation did not verify the anomaly. The magnesium-rich and calcium-rich chemical composition of kimberlite might engender difficulty during chemical separation of tungsten for isotope analyses. This paper presents a simple, one-step anion exchange technique for precise and accurate determination of tungsten isotopes in kimberlites using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Large quantities of Ca and Mg in kimberlite samples were precipitated and removed with aqueous H(2)SO(4). Highly pure fractions of tungsten for isotopic measurements were obtained following an anion exchange chromatographic procedure involving mixed acids. That procedure enabled efficient removal of high field strength elements (HFSE), such as Hf, Zr and Ti, which are small ions that carry strong charges and develop intense electrostatic fields. The tungsten yields were 85%-95%. Advantages of this system include less time and less use of reagents. Precise and accurate isotopic measurements are possible using fractions of tungsten that are obtained using this method. The accuracy and precision of these measurements were confirmed using various silicate standard rock samples, JB-2, JB-3 and AGV-1.

CHARGED LEPTON-NUCLEUS INELASTIC SCATTERING AT HIGH ENERGIES

The composite model is made to describe inelastic high-energy scattering of muons and taus in standard rock. It involves photonuclear interactions at low Q2 as well as moderate Q2 processes and the deep inelastic scattering (DIS). In the DIS region the neutral current contribution is taken into consideration. Approximation formulas both for the muons and tau energy loss in standard rock are presented for wide energy range.

Iron isotopes in natural carbonate minerals determined by MC-ICP-MS with a 58Fe– 54Fe double spike

We have developed a method for iron isotope analysis by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) using a 58Fe– 54Fe double spike. A 20 min analysis produces mass-bias-corrected iron isotope data with an external reproducibility of ±0.05 (2 SD) on δ 56Fe, which represents a decrease in analysis time compared to sample-standard bracketing techniques. The estimation of external reproducibility is based on replicate analysis of the ETH hematite in-house standard. The double spike method has two advantages. First, matrix effects during MC-ICP-MS analysis are decreased with tests showing that accurate iron isotope data can, in some cases, be obtained even when matrix levels exceed iron concentration (Na/Fe, Mg/Fe, and Ca/Fe up to 5, 2, and 0.1, respectively). Because chemical separation reduces matrix/Fe to levels more than three orders of magnitude lower than this, measured Fe isotope compositions are unlikely to be compromised by matrix effects. Second, it is possible to spike samples before chemical purification, which enables any isotopic fractionation effect because of incomplete recovery of iron from a sample to be accounted for. This may be important where obtaining quantitative iron yields from samples is difficult, such as the extraction of dissolved iron from water samples. Fe isotope data on a set of standard reference materials (igneous rocks, ferromanganese nodules, sedimentary rocks, and ores) are presented, which are in agreement with previously published data considering analytical uncertainties. Mantle-derived standard rock samples that are the source of iron for surficial, (bio)geochemical cycling yield a mean δ 56Fe of 0.041 ± 0.11‰ ( n = 8; 2 SD) with reference to IRMM-14. Hydrothermal and metamorphic calcium carbonate rocks with a relatively low iron content (100–4000 ppm) have δ 56Fe = −1.25 to −0.07‰. Structural Fe(II) in hydrothermal calcites has δ 56Fe = −1.25 to −0.27‰. The light iron in this range of carbonate minerals may reflect the iron isotope composition of the hydrothermal fluids from which the carbonate precipitated, or the presence of Fe(III) and/or organic material in the hydrothermal fluids during calcite precipitation.

Mathematical Correction for Polyatomic Isobaric Spectral Interferences in Determination of Lanthanides by Inductively Coupled Plasma Mass Spectrometry

The determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is complicated by several spectral overlaps from M+, MO+ or MOH+ ions formed in the ICP. Especially, it is essential to avoid the spectral interferences from lighter lanthanide and Ba polyatomic ions on middle or heavier lanthanides. To tackle this problem, we have developed a mathematical correction method, which reduces all the spectral overlaps from oxide species of Pr, Nd, Ce and Sm over Gd, Tb, Dy and Ho, and Gd, Tb over Yb and Lu. It can also successfully correct the oxide and hydroxide interference of Ba over Eu. The effectiveness of the proposed the mathematical correction scheme is demonstrated for the USGS Standard Rock samples AGV-1 and G-2. The results show that the experimental data obtained by applying the mathematical correction scheme for lanthanides is in good agreement with the reported values, using pneumatic and ultrasonic nebulisation methods, for their ICP-MS analysis.

X-ray Fluorescence Analysis of Rare Earth Elements in Rocks Using Low Dilution Glass Beads

Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan.

Reply to the: Comment on “Pb isotopic analysis of standards and samples using a 207Pb– 204Pb double spike and thallium to correct for mass bias with a double focusing MC-ICP-MS” by Baker et al.

The following Comment addresses the issueconcerning the accuracy of the thallium-corrected Pbisotope data from Theistareykir, NE Iceland (Strackeet al., 2003), and the drill core recovered by theHawaii Scientific Drilling Project (HSDP; Blichert-Toft et al., 2003). Baker et al. (2004) claim that,because of improper mass-spectrometry techniques,these data sets are inaccurate to a degree that by farexceeds the errors reported in these two papers.Baker et al. (2004) dismiss the Theistareykir(Stracke et al., 2003) and HSDP data (Blichert-Toftet al., 2003) and assert that the Pb isotope ratiosproduced in Lyon are more than 3000 ppm offcompared to the claimed reproducibility of less thanabout 500 ppm (Stracke et al., 2003; Blichert-Toft etal., 2003; Albare`de et al., 2004). Baker et al’s. (2004)arguments are based on a comparison of Copenhagenand Lyon data for solution and rock standards and onebcommonQ sample. The Baker et al. (2004) compar-ison is, however, erroneous because,1. The only solution standard (98B) analyzed by boththe Copenhagen and Lyon groups shows anexcellent agreement (103, 109, 174 ppm on

High‐precision Pb‐Sr‐Nd‐Hf isotopic characterization of USGS BHVO‐1 and BHVO‐2 reference materials

The recent development of multiple‐collector inductively coupled plasma mass spectrometry (MC‐ICP‐MS) and increasing use of the technique have created the need for well‐characterized rock standards, especially for isotopic systems where no internal fractionation correction can be applied. This paper presents a careful leaching experiment on the U.S. Geological Survey (USGS) reference materials BHVO‐1 and BHVO‐2 (Hawaiian basalts) and documents the evidence for contamination of the rock powders during processing. This contamination accounts for the difference in Pb isotopic ratios of BHVO‐1 and BHVO‐2 as well as for their lack of homogeneity both in Pb isotopic compositions and in some trace element contents.

Hafnium isotope ratios of nine GSJ reference samples

176Hf/177Hf ratios of nine geochemical reference rocks from the Geological Survey of Japan, together with BIR-1 and BCR-2, were determined using multi-collector inductively coupled plasma mass spectrometry. Our data for BIR-1, BCR-2 and JB-1 are in agreement with those previously reported, demonstrating the appropriateness of the chemical procedure and isotopic measurement employed in this study. The reference rocks have a wide range of 176Hf/177Hf covering the field defined by various volcanic rocks, such as mid-ocean ridge basalts, ocean island basalts, and subduction related volcanic rocks. They are therefore suitable as rock standards for Hf isotope measurement of geological samples.

Isotopic composition of Yb and the determination of Lu concentrations and Lu/Hf ratios by isotope dilution using MC‐ICPMS

We report Yb isotopic data for the purpose of accurately correcting measurements of Lu and Lu/Hf ratios during Multicollector Inductively Coupled Plasma Mass Spectrometer (MC‐ICPMS) analysis. The Yb isotopic ratios agree with recent results of Chu et al. [2002] and Amelin and Davis [2004], when corrected for mass fractionation to the same reference values. Protocols for Lu measurement involving simultaneous subtraction of Yb interference and application of a fractionation correction based on Yb are described. It is shown that Lu concentrations and Lu/Hf ratios determined by MC‐ICPMS using this methodology are more precise and potentially more accurate than results based on analysis of Lu by Thermal Ionization Mass Spectrometry (TIMS). A number of MC‐ICPMS Lu‐Hf isotopic analyses of standard rocks and other geological samples, previously analyzed by TIMS, are presented. These document reproducibility of Lu/Hf within 0.2%, where most discrepancies can be assigned to the unknown Lu mass fractionation during TIMS analysis.

Pb isotopic analysis of standards and samples using a 207Pb– 204Pb double spike and thallium to correct for mass bias with a double-focusing MC-ICP-MS

A Pb isotope analytical method using a 207Pb– 204Pb double spike (DS) and a double-focusing MC-ICP-MS routinely yields standard and sample data with an external reproducibility <100 ppm for all Pb isotope ratios. With modest increases in analysis times (<10 min), external reproducibility of ≤50 ppm is attainable, e.g., SRM 981— 206Pb/ 204Pb=16.9418±6; 207Pb/ 204Pb=15.5000±6; 208Pb/ 204Pb=36.7265±19 ( n=26; 2 S.D.). This is achievable even when unspiked and spiked runs are analysed sequentially, demonstrating that memory due to use of the DS can be easily overcome by short and careful washout routines coupled with on-peak zeroes measurements. Replicate analyses of three mixtures of SRM 981 and SRM 982, in variable proportions, lie within 42 ppm of a mixing line between SRM 981 and SRM 982 Pb isotope ratios. Coupled use of thallium to correct for mass bias during the same analyses of standards and samples does not produce Pb isotopic data of comparable quality to the DS-corrected analyses. While the approach of Woodhead (A simple method for obtaining highly accurate Pb isotope data by MC-ICP-MS, J. Anal. At. Spectrom., 17 (2002) 1381–1385) allows us to produce accurate thallium-corrected Pb isotopic data, the DS data are at least five times more precise and accurate than those obtained when using thallium to correct for mass bias. Relatively rapid analytical throughput (20–25 samples/day), elimination of differential loading blanks between unspiked and spiked runs, easy optimal spiking and the lack of anomalous 207Pb behaviour as observed sometimes during TIMS analysis make DS analysis by MC-ICP-MS an attractive procedure. New Pb DS data on lavas from the Torfajökull volcanic centre (Iceland) define near-perfect binary mixing within our errors, even over a very small range in 207Pb/ 204Pb (<300 ppm), comparable to or smaller than the reproducibility of thallium-corrected Pb isotopic data. We also show that recently published Pb isotopic data for Theistareykir picrites (Stracke et al., Theistareykir revisited, Geochem. Geophys. Geosyst., (2003) Paper no. 2001GC000201), corrected for mass bias using thallium, are up to 3300 ppm inaccurate compared to our DS data and also that of Thirlwall (Interlaboratory and other errors in Pb isotope analyses investigated using a 207Pb– 204Pb double spike, Chem. Geol., 163 (2000) 299–322) and Thirlwall et al. (Mantle components in Iceland and adjacent ridges investigated using double-spike Pb isotope ratios, Geochim. Cosmochim. Acta., 68, (2004) 361–386). These Icelandic data highlight both the potential and the dangers of Pb isotopic analysis by MC-ICP-MS and demonstrate the need for all MC-ICP-MS Pb isotopic studies to include analyses of well-characterized and isotopically homogeneous rock standards in addition to SRM 981. To this end, we present ca. 100 analyses of international standard reference materials, including the NIST 610–612–614 glasses that are used for in situ Pb isotope analysis by laser ablation ICP-MS and SIMS. While the Pb isotope compositions of some standards show poor reproducibility due to variable contamination during initial preparation, four of the reference materials (JB-2, NOD-A-1, AGV-1, BCR-1) and the NIST 610 and 612 glasses reproduce to <200 ppm. We also note that Pb isotopes are fractionated during normal anion exchange chemical separation of Pb, as collection of Pb in HCl significantly fractionates Pb isotope ratios, with the lighter isotopes preferentially eluted first. Provided a sufficiently large volume of ≥6 M HCl is collected (>10× the resin volume), there is no measurable (<50 ppm) fractionation of the Pb isotopes as the light-isotope-depleted tail is fully stripped from the resin.

Geomechanical Models for Clastic Grain Packing

This study proposes a classification of sphere models for grain packing types of coarse grained clastic soft and hard rocks with special emphasis on Permocarboniferous red-beds. The classification covers the range of principal packing types and different cements. Random sphere packing models are derived from ideal symmetric packing models. The study comprises both homogeneous models with equal single grain properties and heterogeneous models with different single grain properties. For each packing type geomechanically relevant parameters like the packing density or coordination numbers are calculated and discussed. The models are correlated with results of image analysing and standard rock engineering experiments that were carried out on a variety of grain mixtures and sedimentary rocks of Permocarboniferous age. The discussion is concerned with the principles of grain packing models and the particular effects of distinct packing types on the petrophysical rock properties and the geomechanical behaviour of the examples presented.

Quantitative Determination of Lead and Uranium from Geological Samples

A separation scheme for lead and uranium is described. Before the separation of lead, uranium was collected using columns with a conventional method, namely, the separation and collection of uranium were conducted using 6 M and 0.5 M hydrochloric acid, respectively. This process separated lead from iron, thallium, and probably bismuth, which would suppress lead ionization in a thermal ionization mass spectrometer (TIMS). For lead separation, columns with a low ratio of height over inner diameter (H 10 mm, i.d. 4 mm) were employed to strip lead quickly from the resin (AG1-X2 and AG1-X8). Furthermore, 7 M nitric acid was adopted as the eluent instead of the commonly used 6 M hydrochloric acid to achieve a quantitative recovery of lead. These improvements enable us to collect lead with only 0.35 mL of 7 M nitric acid for both types of resin. Recoveries using this method obtained by the measurement of GSJ standard rock samples JA-2 and JA-3 were 96.4% and 99.7%, respectively. Total procedure blanks in two separate runs were 13 pg and 15 pg, respectively. It is therefore suggested that this method is suitable for separation and purification of lead for quantitative and isotopic analyses of geological materials.

Precise Isotope Determination of Trace Amounts of Nd in Magnesium-rich Samples

We developed a technique combining mass spectrometry with chemical separation to analyze Sm-Nd isotopic compositions of ultramafic rock samples, which have extremely high Mg and low Nd concentrations and are always difficult to analyze. In the case of ultramafic rocks, abundant Mg forms fluorides during decomposition by HF, and minor amounts of Sm and Nd are strongly partitioned into fluorides, which would be a significant reason of low recovery yields of these elements and obstructed to determine a reliable isotopic ratio of Nd and Sm. We introduced pre-decomposition by HCl prior to the conventional method by HF and HClO4 that made it possible to elevate recovery yield to 85%. On the other hand, replicate measurements of Nd standard solution (La Jolla) by changing the ion current of Nd+ and the amount of Nd indicate that reliable isotopic ratios are measured under the condition of >0.04×10-11 A of 144Nd+ ion current and >2 ng of Nd. By applying our method, we analyzed 143Nd/144Nd ratio and Sm and Nd concentrations of PCC-1, which is an ultramafic standard rock sample of United States Geological Survey. The results of our analysis were 0.512226±0.000026, 0.00551±0.00041, and 0.0278±0.0011 ppm, respectively. These results are the first report of 143Nd/144Nd ratio for PCC-1.

Quantitative Elemental Analysis of Silicate Rocks by Laser-Induced Plasma Spectroscopy

A quantitative elemental analysis of silicate rocks was carried out with a laser microprobe analyzer. A Q-switched Nd: YAG laser (90mJ, 10ns) was focused on rock samples in an argon atmosphere at reduced pressure, and the emission spectra from laser-induced plasma were measured using time-resolved spectroscopy. The experimental results showed that the maximum spectral line intensity was obtained in argon at approximately 200 Torr, whereas the spectral line-to-background ratio were maximized at around 60 Torr, by observing the laser plasma with a time delay of 0.4μs. Furthermore, the results of time-resolved spectroscopy of the plasma produced in argon at 200 Torr and 60 Torr indicated that time-resolved measurement of a spectrum in the initial stage of plasma generation (-1μs) at a pressure of 60 Torr was effective for improving the slope of the calibration curve. Based on the results, standard rock samples were analyzed for aluminum, magnesium, calcium, titanium and iron, and linear calibration curves with a slope of unity were obtained by measuring spectra with a gate width of 0.6μs at a delay time of 0.4μs after the laser pulse in argon at 60 Torr.

ESCV Membership

The errors in the chemical analyses of a granodiorite rock powder for 6 constituents (K 2O, Na2O, CaO,∑Fe2O3, MgO, and MnO) have been determined by replicate analyses of the whole rock and of a series of different sieved fractions. Sample inhomogeneity is indicated. This is confirmed by analyses of the fused rock powder. Fusion to a glass is therefore recommended for the preparation of geochemical rock standards.

Segmented thermal storage

Standard methods of charging solar thermal energy into rock bed storage for space heating tend to reduce stratification because of decreasing collector temperatures in the afternoon. This creates inaccessible regions of higher temperature rocks and may reduce the amount of energy within the bed. Stratification of the segmented bed has the advantages of supplying the highest temperature air to the dwelling and the lowest temperature air to the collector. A method of preserving the stratification by segmenting the storage bed was numerically studied. Discharging was not studied. Segmenting a standard rock bed and routing the flow to segments cooler than the inlet air during charging was shown to preserve stratification throughout the bed. The simulated segmented bed contained 1% less maximum energy than an otherwise identical standard bed for an approximated solar day. This was a consequence of the segment control temperature locations.

Experiments on the Element Distribution between the Granodiorite JG‐1a and 2M NaCl Hydrothermal Solution at Temperatures of 300 to 800°C and a Pressure of 1 kb

Abstract. The distribution of Na, K, Ca, Mg, Mn and Fe between the granodiorite JG‐la, one of the geochemical standard rocks, and 2M NaCl aqueous solution was experimentally determined at temperatures of 300 to 800d̀C and a pressure of 1 kb using standard cold seal‐type pressure vessels. The solid run products melted partially at 800d̀C. Only K shows a significantly different behavior from the experiments using the basalt JB‐la (Uchida and Tsutsui, 2000) due to the presence of ortho‐clase in the JG‐la. The transition elements tend to be preferably partitioned into the aqueous chloride solutions with increasing temperature. At 800d̀C and 1 kb, the Fe concentration of the aqueous chloride solutions reached up to 5,000 ppm, and the Mn concentration up to 350 ppm. The distribution coefficient, KD, i = Ci, sol/Ci, rock, is in the order of Na&gt;K&gt;Mn&gt;Ca&gt; Fe&gt;Mg at 300d̀C, but changed in the order of Mn&gt;N&gt;K&gt;Fe&gt;Ca&gt;Mg at 800d̀C. The distribution coefficients of the divalent cations for the JG‐la are higher than those for the JB‐1a. The distribution coefficient of the transition elements, Fe and Mn, increases significantly with increasing temperature. The thermodynamic analysis for aqueous speciation revealed that this is attributable to the formation of the tri‐chloro complexes of the transition elements at higher temperatures.

Determination of lanthanides in rock samples by inductively coupled plasma mass spectrometry using thorium as oxide and hydroxide correction standard

Determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) using modified mathematical correction method has been studied. Normally, the ICP-MS analysis of middle and heavier lanthanides becomes difficult by severe spectroscopic overlap of M +, MO + or MOH + ions from lighter lanthanides and Ba. A correction method based on a single element oxide yield measurement, is a simple approach to correct for the above spectroscopic overlaps. But the uncertainty in the oxide and hydroxide yields measurement of lanthanides and barium over a long period of time can lead to inaccurate results even under fixed plasma conditions. To correct this, thorium was adopted as an oxide and hydroxide correction standard. Using a ratio of lanthanide oxide yield to thorium oxide yield, the lanthanide correction factors (LCF) were established and incorporated in the mathematical correction scheme. The same factors were also established for hydroxide correction. The proposed modified correction scheme was applied to the determination of lanthanides by ICP-MS from the USGS Standard Rock samples AGV-1 and G-2. The results are in good agreement with the reported values. The method also proved to be useful in isotopic ratio measurement of lanthanides having severe isobaric overlaps.