Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The analytical performance of high-resolution multiple-collector inductively coupled plasma mass spectrometry (HR-MC-ICPMS), employing amplifiers with a 10(12) ohm resistor, was examined. HR-MC-ICPMS showed 50 times higher detection efficiency and 100 times better precision for sulfur and S-34/S-32 than the single-collector high-resolution sector field type ICPMS (HR-ICP-SFMS). The 3 sigma detection limits for S-32 and S-34 were 0.2 and 6 ng mL(-1), respectively. No matrix effects were observed, for up to 3000 mu g g(-1) of total dissolved solids (TDS), within 0.6% error. Thus when the isotope dilution (ID) technique is utilized, this method allows analyses of sulfur concentration of seven times smaller, with six times better precision, than the HR-ICP-SFMS methods. To demonstrate the applicability of this ID-HR-MC-ICPMS method, bulk sulfur concentrations in bovine serum albumin, human serum, eight silicate reference materials (JB-2, JB-3, JA-2, JA-3, JP-1, BCR-2, BHVO-1 and AGV-1), and four carbonaceous chondrites (Murchison, Allende, Dal al Gani 521 and 194) were measured.

DOI： 10.1039/c2ja10337k

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The Cretaceous Okhotsk-Chukotka volcanic belt (OCVB) is a prominent subduction-related magmatic province, having the remarkably high proportion of silicic rocks (ca. 53% of the present-day crop area, and presumably over 70% of the total volcanic volume). Its estimated total extrusive volume ranges between 5.5×10 5km 3 (the most conservative estimate) and over 10 6km 3. This article presents a brief outline of the geology of OCVB, yet poorly described in international scientific literature, and results of a geochronological study on the northern part of the volcanic belt. On the base of new and published U-Pb and 40Ar/ 39Ar age determinations, a new chronological model is proposed. Our study indicates that the activity of the volcanic belt was highly discontinuous and comprised at least five main episodes at 106-98Ma, 94-91Ma, 89-87Ma, 85.5-84Ma, and 82-79Ma. The new data allow a semi-quantitative estimate of the volcanic output rate for the observed part of the OCVB (area and volume approximately 10 5km 2 and 2.5×10 5km 3, respectively). The average extrusion rate for the entire lifetime of the volcanic belt ranges between 1.6 and 3.6×10 -5km 3yr -1km -1, depending on the assumed average thickness of the volcanic pile; the optimal value is 2.6×10 -5km 3yr -1km -1. Despite imprecise, such estimates infer the time-averaged volcanic productivity of the OCVB is similar to that of silicic LIPs and most active recent subduction-related volcanic areas of the Earth. However, the most extensive volcanic flare-ups at 89-87 and 85.5-84Ma had higher rates of over 9.0×10 -5km 3yr -1km -1.The main volumetric, temporal and compositional parameters of the OCVB are similar to those of silicic LIPs. This gives ground for discussion about the geodynamic setting of the latters, because the widely accepted definition of a LIP implies a strictly intraplate environment. Considering the genesis of the OCVB and other large provinces of silicic volcanism, we propose that residual thermal energy preserved in the continental crust after a previous major magmatic event may have been one of major reasons for high proportion of felsic rocks in a volcanic pile. In this scenario, underplating of mantle-derived basalts causes fast and extensive melting of still hot continental crust and generation of voluminous silicic magmas. © 2011 Elsevier B.V.

DOI： 10.1016/j.jvolgeores.2011.12.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL ACAD SCIENCES  

Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 mu m, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-mu m-sized craters but also a large number of sub-mu m-to several-mu m-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-mu m-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

DOI： 10.1073/pnas.1116236109

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

DOI： 10.1093/petrology/egr017

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A method for the simultaneous determination of Cd with In, Tl and Bi by isotope dilution-internal standardisation (ID-IS) ICP-QMS using the same aliquot for rare earth element and other trace element determinations was developed. Samples mixed with an enriched 149Sm spike were decomposed using a HF-HClO4 mixture, which was evaporated and then diluted with HNO3. After determination of Sm by ID-ICP-QMS and Cd, In, Tl and Bi concentrations were determined using the 149Sm intensity as an internal standard. The interference of MoO+ on Cd+ was corrected using the MoO+/Mo+ ratio separately measured using a Mo standard solution, and the validity of the externally determined oxide-forming ratio correction was evaluated. The MoO+/Mo+ ratios measured using the standard solution and samples were similar to 0.0002 and < 0.002, respectively. Detection limits for Cd, In, Tl and Bi in silicate samples were at levels of < 1 ng g-1 with a total uncertainty of < 7%. Cadmium in the carbonaceous chondrites, Orgueil (CI1), Murchison (CM2) and Allende (CV3) as well as Cd, In, Tl and Bi in the reference materials, JB-2, JB-3, JA-1, JA-2, JA-3, JP-1 (GSJ), BHVO-1, AGV-1, PCC-1 and DTS-1 (USGS) and NIST SRM 610, 612, 614 and 616 were determined to show the applicability of this method.Une methode pour la determination simultanee du Cd avec l'In, le Tl et le Bi par dilution isotopique a standardisation interne (ID-IS) ICP-QMS utilisant le meme aliquot pour la determination des terres rares et d'autres elements traces a ete developpe. Les echantillons melanges avec un ajout (' spike ') enrichi en 149Sm ont ete decomposes en utilisant un melange HF-HClO4, qui a eteevapore et, enfin, dilue avec HNO3. Apres la determination du Sm par ID-ICP-QMS, les concentrations en Cd, In, Tl et Bi ont ete determinees en utilisant l'intensite du 149Sm comme standard interne. L'interference de MoO+ sur Cd+ a ete corrige en utilisant le rapport MoO+/Mo+ mesure separement a l'aide d'une solution de Mo standard, et la validite de cette correction a eteevalue. Les rapports MoO+/Mo+ mesures a l'aide des solutions standards et des echantillons ont ete respectivement d'environ 0.0002 et inferieurs a 0.002. Les limites de detection pour le Cd, l'In, le Tl et le Bi dans les echantillons de silicate ont etea des niveaux inferieurs a 1 ng g-1 avec une incertitude totale inferieure a 7%. Le cadmium dans les chondrites carbonees : Orgueil (CI1), Murchison (CM2) et Allende (CV3) ainsi que le Cd, l'In, le Tl et le Bi dans les materiaux de reference : JB-2, JB-3, JA-1, JA-2, JA-3, JP-1 (GSJ), BHVO-1, AGV-1, PCC-1, DTS-1 (USGS) et NIST SRM 610, 612, 614 et 616 ont ete determines afin de demontrer l'applicabilite de cette methode.

DOI： 10.1111/j.1751-908X.2010.00054.x

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Precise isotopic determination methods for Hf and Pb at sub-nano gram levels have been undertaken for this contribution utilizing the Neptune multiple collector ICP-MS (MC-ICP-MS) with a newly designed sample cone (the Jet cone) and a new pre-amplifier with a highly-resistive register of 1012 ohm. The Jet cone enhanced sensitivities 1.6 and 3 times for Hf and Pb, respectively. The Jet cone showed no significant improvements in reproducibility of Hf isotope analysis at &gt;1 ng compared to the normal cone, but the reproducibility improved considerably by half when Hf concentration of &lt;1 ng was measured. Thus, 0.3 and 0.8 ng of Hf can yield reproducibility (2SD in epsilon-unit) of 3 and 1.7, respectively. Reproducibility (RSD) of Pb-207/Pb-206, Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 were 0.026, 0.28, 0.33 and 0.36% using total Pb of 0.025 ng, and 0.02, 0.10, 0.10 and 0.08% using 0.05 ng, respectively. Thus, the Jet cone with the new pre-amplifier showed the best performance compared to the normal cone and pre-amplifier and are similar or even better than those obtained by the Pb-202-Pb-205 double-spike TIMS or multi-ion counting ICP-MS techniques.

DOI： 10.1039/c0ja00015a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The standard planetary formation models assume that primitive materials, such as carbonaceous chondrites, are the precursor materials of evolved planetesimals. Past chronological studies have revealed that planetesimals of several hundred kilometers in size, such as the Howardite-Eucrite-Diogenite (HED) parent body (Vesta) and angrite parent body, began their differentiation as early as similar to 3 million years of the solar system formation, and continued for at least several million years. However, the timescale of planetesimal formation in distinct regions of the inner solar system, as well as the isotopic characteristics of the reservoirs from which they evolved, remains unclear. Here we present the first report for the precise (53)Mn-(53)Cr ages of monomict ureilites. Chemically separated phases from one monomict ureilite (NWA 766) yielded the Mn-Cr age of 4564.60 +/- 0.67 Ma, identical within error to the oldest age preserved in other achondrites, such as angrites and eucrites. The (54)Cr isotopic data for this and seven additional bulk ureilites show homogeneous epsilon(54)Cr of similar to-0.9, a value distinct from other achondrites and chondrites. Using the epsilon(54)Cr signatures of Earth, Mars, and Vesta (HED), we noticed a linear decrease in the epsilon(54)Cr value with the heliocentric distance in the inner region of the solar system. If this trend can be extrapolated into the outer asteroid belt, the epsilon(54)Cr signatures of monomict ureilites will place the position of the ureilite parent body at similar to 2.8 AU. These observations imply that the differentiation of achondrite parent bodies began nearly simultaneously at similar to 4565 Ma in different regions of the inner solar system. The distinct epsilon(54)Cr value between ureilite and carbonaceous chondrite also implies that a genetic link commonly proposed between the two is unlikely.

DOI： 10.1088/0004-637X/720/1/150

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

An investigation of the petrology and geochemistry of peridotites and gabbros in the Horoman massif, Hokkaido, Japan was undertaken to constrain geochemical processes in the upper mantle. Two types of sample were studied: one type comprises peridotites and gabbros forming thin layers varying from a few millimeters to centimeters in scale (thin-layer peridotites and gabbros); the other comprises thick layers (> 1 m scale; massive peridotites and gabbros). There is no clear trace element evidence for metasomatism in the thin-layer peridotites. Instead, they have melt-rock reaction textures interpreted in terms of the formation of secondary pyroxene at the expense of primary porphyroclastic olivine and dissolution of primary porphyroclastic pyroxene to form secondary olivine. The thin-layer gabbros also exhibit no metasomatic effects; they have incompatible element depleted trace element characteristics and mid-ocean ridge basalt (MORB)-like isotopic signatures consistent with the presence of a new type of gabbro that previously has not been described from the Horoman Massif. The whole-rock chemistry of the thin-layer peridotites and thin-layer gabbros can be explained by melt-peridotite reactions between isotopically highly depleted MORB mantle (represented by the thin-layer peridotites) and melt with geochemical affinity to Pacific MORB (represented by the thin-layer gabbros). Sm-Nd and Lu-Hf isotope systematics suggest that these reactions might have occurred at similar to 300 Ma. Some of the plagioclase lherzolites and all of the spinel lherzolites and harzburgites within the massive peridotites show enrichment in incompatible trace elements and more radiogenic Hf-Nd-Pb isotopic compositions than the incompatible-element depleted thin-layer peridotites. The analyzed massive gabbros are interpreted as subduction-related magmas formed in a MORB-source mantle wedge, which have subsequently interacted with a fluid or melt in the Hidaka subduction zone. Hf-Nd-Pb isotope systematics reveal that this interaction may have occurred at an age younger than similar to 50 Ma. Melt- and fluid-related processes occurring in the upper mantle are systematically identified from the samples of the Horoman Massif based on petrography, major and trace element, and Sr-Nd-Pb-Hf isotope geochemistry. These processes occurred in different tectonic settings such as the convecting oceanic mantle and supra-subduction zone mantle wedge and have variably modified the original chemistry of residual mantle protolith, formed by partial melting of a depleted MORB source mantle at similar to 1 Ga.

DOI： 10.1093/petrology/egq024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A method to determine F and Cl in silicate materials by employing pyrohydrolysis and ion chromatography (IC) is described. Pyrohydrolysis involved mixing a pulverised sample (similar to 40 mg) with V2O5 (similar to 160 mg) and heating to 1100 degrees C under a wet oxygen flow in a quartz tube. Recovery yields of F and Cl were similar to 97% using a NaF + NaCl standard solution. Detection limits of the pyrohydrolysis-IC method for silicate samples were 0.36 and 0.69 mu g g-1 for F and Cl, respectively. Fluorine and Cl concentrations were determined in the reference materials JB-2, JB-3 and JA-1 from the GSJ; BCR-2, BHVO-1, BHVO-2, AGV-1 and AGV-2 from the USGS; and NIST SRM 610, 612 and 614 glasses. Precisions (RSD) for determinations of F were 1-13% (except NIST SRM 614) and 2-19% for Cl, and were dependent on the concentration and blank correction. Most results obtained in this study were in good agreement with those of previous studies. In comparison, the Na2CO3 + ZnO fusion method at 900 degrees C showed that the yields of F and Cl by alkaline fusion systematically decreased with fusion duration time. The yields were 84% and 83% for JB-3, inferring that F and Cl were lost in this alkaline fusion.Une methode de determination des teneurs en F et Cl des materiaux silicates par pyrohydrolyse et chromatographie ionique (CI) est decrite. La pyrohydrolyse implique le melange entre un echantillon pulverise (similar to 40 mg) et du V2O5 (similar to 160 mg) et un chauffage a 1100 degrees C sous un flux d'oxygene humide dans un tube de quartz. Les rendements du F et du Cl ont ete d'environ 97% en utilisant une solution standard de NaF + NaCl. Les limites de detection de la methode CI-pyrohydrolyse pour les echantillons silicates ont ete respectivement de 0.36 et 0.69 mu g g-1 pour F et Cl. Les concentrations en F et Cl ont ete determinees dans les materiaux de reference JB-2, JB-3 et JA-1 du GSJ; BCR-2, BHVO-1, BHVO-2, AGV-1 et AGV-2 de l'USGS, et dans les verres de reference NIST SRM 610, 612 et 614. Les precisions (RSD) pour les determinations du F ont variees entre 1 et 13% (sauf pour le NIST SRM 614) et entre 2 et 19% dans le cas de celles du Cl. Elles dependent de la concentration et de la correction du blanc. La plupart des resultats obtenus dans cette etude sont en bon accord avec ceux des etudes precedentes. En comparaison, la methode de fusion utilisant le couple Na2CO3 + ZnO a 900 degrees C montre que les rendements de F et Cl par fusion alcaline diminuent systematiquement avec la duree de fusion. Les rendements ont ete respectivement de 84 et 83% pour JB-3, ce qui sous entend une perte de F et de Cl durant cette fusion alcaline.

DOI： 10.1111/j.1751-908X.2010.00043.x

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A new determination method for Cr, Mn, Fe, Co and Ni in silicate samples by an isotope dilution-internal standardization method (ID-IS)-high resolution (HR)-MC-ICP-MS has been developed. A silicate sample is dissolved into solution, and a Cr-spike solution is added into an aliquot of the sample solution. Then the solution is introduced into HR-MC-ICP-MS without chemical separation. Concentration of Cr is determined by ID, and those of Mn, Fe, Co and Ni are by ID-IS. Matrix effects were examined in detail, and negligible down to a dilution factor (DF; the weight of the sample solution over that of the sample in the solution) of similar to 3000 for basalt, and similar to 10(4) for peridotite and chondrite within an error range of +/-1%. ID-IS-FIR-MC-ICP-MS showed intermediate precision of similar to 1% for basalt and chondrite, which is comparable to ID-TIMS for Cr, Fe and Ni, and >10 times better than HR-ICP-MS, suggesting that this method is suitable for precise Mn-Cr and Fe-Ni chronometers. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemgeo.2010.03.018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The contribution of subducted carbonate sediments to the genesis of the Southwestern Colombian arc magmas was investigated using a comprehensive petrography and geochemical analysis, including determination of major and trace element contents and Sr, Nd, Hf and Pb isotope compositions. These data have been used to constrain the depth of decarbonation in the subducted slab, indicating that the decarbonation process continues into the sub-arc region, and ultimately becomes negligible in the rear arc. We propose on the basis of multi-isotope approach and mass balance calculations, that the most important mechanism to induce the slab decarbonation is the infiltration of chemically reactive aqueous fluids from the altered oceanic crust, which decreasingly metasomatize the mantle wedge, triggering the formation of isotopically different primary magmas from the volcanic front (VF) with relatively high Hf-176/Hf-177, high Sr-87/Sr-86, negative values of epsilon Nd and lower Pb isotopes compared to the rear arc (RA).The presence of more aqueous fluids at the volcanic front may increase the degree of decarbonation into carbonate-bearing lithologies. Moreover, with increasing pressure and temperature in the subduction system, the decrease in dehydration of the slab, leads to cessation of fluid-induced decarbonation reactions at the rear arc. This development allows the remaining carbonate materials to be recycled into the deep mantle. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2009.10.031

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A sequential chemical separation technique for Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial silicate rocks was developed for precise and accurate determination of elemental concentration by the isotope dilution method (ID). The technique uses a combination of cation-anion exchange chromatography and Eichrom nickel specific resin. The method was tested using a variety of matrixes including bulk meteorite (Allende), terrestrial peridotite (JP-1), and basalt (JB-1b). Concentrations of each element was determined by thermal ionization mass spectrometry (TIMS) using W filaments and a Si-B-Al type activator for Cr, Fe, Ni, and Zn and a Re filament and silicic acid-H3PO4 activator for Cu. The method can be used to precisely determine the concentrations of these elements in very small silicate samples, including meteorites, geochemical reference samples, and mineral standards for microprobe analysis. Furthermore, the Cr mass spectrometry procedure developed in this study can be extended to determine the isotopic ratios of Cr-53/Cr-52 and Cr-54/Cr-52 with precision of similar to 0.05 epsilon and similar to 0.10 epsilon (1 epsilon = 0.01%), respectively, enabling cosmochemical applications such as high precision Mn-Cr chronology and investigation of nucleosynthetic isotopic anomalies in meteorites.

DOI： 10.1021/ac901762a

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Language：English   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

In this review, a new classification of elements based on behavior in hydrofluoric acid (HF) solution is presented for the precise quantitative analysis of each element by inductively coupled plasma mass spectrometry (ICP-MS). The elements are divided into 7 groups: (1) "fluorophile" elements; (2) insoluble fluoride-forming elements; (3) "bromophile" or "iodophile" elements; (4) "oxophile" elements; (5) "aquaphile" elements; (6) bare cation elements; and (7) other elements. Especially, the importance of fluorophile and insoluble fluoride-forming elements in elemental analysis is described. Due to the elemental characteristics, these two groups of elements cannot be dissolved simultaneously in the same solution, and thus cannot be measured together. In addition, coprecipitation of the fluorophile elements with the insoluble fluorides occurs in some conditions and hinders accurate analysis. The peculiar conditions when the coprecipitation occurs are discussed, and the "Al-addition" and "Mg-addition" methods for overcoming these problems are described. In addition, some state-of-the-art analytical techniques in ICP-MS are shown, and future directions of the element analysis are presented.

DOI： 10.2116/analsci.25.1181

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A method for the determination of Ge, As, Se and Te in silicate samples using isotope dilution-internal standardisation (ID-IS) octopole reaction cell (ORC) ICP-QMS by normal sample nebulisation was developed. The method does not involve either hydride generation or ion exchange. Germanium, Se and Te were determined by isotope dilution (ID), and As was determined by ID-IS. A silicate sample with an added Ge-Se-Te spike was digested with an HF-HNO3-HBr mixture, dried, re-dissolved with HF and the supernatant liquid was directly aspirated into an ORC-ICP-QMS instrument with He or H-2 gas. No matrix effects were observed down to a dilution factor (DF) of similar to 70 for Ge, Se and Te and DF of similar to 1000 for As, which resulted in 3s detection limits in silicates of 2, 1, 0.1 and 4 ng g-1, respectively. Advantages of the method are the simple sample introduction as well as a capability of determining S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by ID-IS-ICP-QMS/SFMS from the same solution. Furthermore, the total sample solution consumption was only 0.253 ml with DF = 2000. Therefore, only a 0.13 mg test portion was required. To demonstrate the applicability of this technique, Ge, As, Se and Te in eight silicate reference materials were determined, as well as S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta in four carbonaceous chondrites.

DOI： 10.1111/j.1751-908X.2009.00014.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN ACAD  

While exposure to fibers and particles has been proposed to be associated with several different lung malignancies including mesothelioma, the mechanism for the carcinogenesis is not fully understood. Along with mineralogical observation, we have analyzed forty-four major and trace elements in extracted asbestos bodies (fibers and proteins attached to them) with coexisting fiber-free ferruginous protein bodies from extirpative lungs of individuals with malignant mesothelioma,. These observations together with patients' characteristics suggest that inhaled iron-rich asbestos fibers and dust particles, and excess iron deposited by continuous cigarette smoking would induce ferruginous protein body formation resulting in ferritin aggregates in lung tissue. Chemical analysis of ferruginous protein bodies extracted from lung tissues reveals anomalously high concentrations of radioactive radium, reaching millions of dines higher concentration than that of seawater. Continuous and prolonged internal exposure to hotspot ionizing radiation from radium and its daughter nuclides could cause strong and frequent DNA damage in lung tissue, initiate different types of tumour cells, including malignant mesothelioma cells, and may cause cancers.

DOI： 10.2183/pjab.85.229

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOCHEMICAL SOC JAPAN  

In view of the requirement of a well-characterized and easily available aquatic sediment reference material, a comprehensive analysis comprising of fifty major, minor and trace elements as well as Sr-Nd-Pb-Hf isotopes were carried out in the stream sediment reference material, JSd-1, issued by the Geological Survey of Japan. The data for marine sediment reference material, MAG-1, issued by U.S. Geological Survey is also obtained for comparison. The elements were divided into two groups: Group I and Group II. Elements in Group I form stable soluble ions in HNO3; and those in Group II form soluble oxo- and fluoro-complexes in HF, such as Zr, Nb, Hf, Ta, etc. For Group I, the sample was decomposed with HF in a tetra fluoro ethylene (TFE) bomb at 245 degrees C for 96 hrs with Mg addition. The elemental concentration was measured by quadrupole type inductively coupled plasma source mass spectrometry (ICP-QMS) and sector field type ICP-MS (ICP-SFMS) using isotope dilution-internal standardization (ID-IS) methods. The aliquot of the sample solution was passed through 3-step column chemistry for isotope ratio determination of Pb by Multiple collector (MC) ICP-MS and thermal ionization mass spectrometry (TIMS), and Sr and Nd by TIMS. For Group II elements, the sample was decomposed with H F in a TFE bomb with the same time and temperature settings. Zr, Mo, Sn, Sb and Hf were determined by I D, and Nb and Ta by ID-IS using ICP-QMS. The original JSd-1 powder showed heterogeneity for Group II elements, indicating insufficient pulverization and distribution. Thus, we further pulverized the powder and measured the concentration, which showed improved homogeneity. The aliquot for the re-pulverized powder was passed through 2-step column chemistry, and the Hf isotope ratio was determined by MC-ICP-MS. Thus a new data on the trace elements as well as Sr-Nd-Pb-Hf isotope ratios is provided for JSd-1 and MAG-1 in this paper.

DOI： 10.2343/geochemj.1.0018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Basalts at mid-ocean ridges are generated by partial melting of the Earth's upper mantle. As a result of this process, the upper mantle has become depleted over time in elements that are preferentially removed by melting(1-3). Although mid-ocean-ridge basalts have traditionally been thought to reflect the chemical composition of such depleted mantle(2-7), recent work has revealed the existence of domains in the upper mantle that are apparently not sampled by the basalts(8). Here we present the lead (Pb), neodymium (Nd) and hafnium (Hf) isotope compositions of peridotites from the Horoman orogenic massif in Japan, which is considered to represent the residues of melting of the upper mantle. These peridotites exhibit the lowest Pb isotope ratios reported from any known mantle material, along with high Nd and Hf isotope ratios. These data suggest that chemical depletion of the peridotites occurred around a billion years ago, and that they represent ancient mantle domains that have escaped convective stirring and homogenization. We suggest that such domains-if abundant in the mantle-may constitute a hitherto unrecognized reservoir with highly unradiogenic lead.

DOI： 10.1038/ngeo363

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We present major and trace element concentrations and Sr-Nd-Hf-Pb isotope data for the c. 13-2 Ma Tertiary lavas from eastern Iceland. Our new geochemical results, together with published geological, geochronological, geochemical and geophysical data, are used to evaluate temporal changes in mantle sources contributing to the Tertiary Icelandic magmatism and the relative roles of these sources in magma productivity. The trace element and radiogenic isotopic compositions clearly distinguish three distinct end-member components in the Tertiary magmatism. Temporal variations in lava geochemistry can be attributed to changes in the relative contributions of these three end-member components to the erupted magmas and correlated with temporal variations in magma productivity. The extrusion of lavas with geochemically and isotopically enriched compositions was particularly pronounced at similar to 13-12 and 8-7 Ma, coincident in time with higher magma productivity. However, the geochemical characteristics of the lavas are different during these two periods: the 13-12 Ma lavas have more radiogenic Hf-176/Hf-177 and less radiogenic Pb-206/Pb-204 than those erupted from 8 to 7 Ma. The eruption of relatively depleted lavas, at around 10 Ma and younger than 6.5 Ma, is coincident with lower magma productivity. The correlation between the composition and productivity of the Tertiary lavas from eastern Iceland is probably due to periodic changes in the involvement of the enriched end-member component, followed by a gradation to periods dominated by the signature of the depleted end-member component and lower magma productivity, at an approximate frequency of 5 Myr.

DOI： 10.1093/petrology/egn029

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The two parallel loci of recent Hawaiian volcanoes, Kea and Loa, have been regarded as the best targets to interpret the chemical structure of an upwelling mantle plume derived from the lower mantle. Here we show that the Sr-Nd-Hf-Pb isotopic data of the shield-building lavas along the Loa locus form a systematic trend from the main shield stage of Koolau (>2.9 Ma) to the active Loihi volcanoes. During the growth of the Koolau volcano, the dominant material in the melting region successively changed from the proposed KEA, DMK (depleted Makapuu), to EMK (enriched Makapuu) components. The proportion of EMK, dominated by a recycled mafic component, is typified by some Koolau Makapuu-stage and some Lanai lavas. Subsequently, the EMK component decreased and LOIHI component increased toward the Loihi lavas. The temporal coincidence between the episodically elevated magma production rate and the abrupt appearance of the typical Loa-type lavas that is restricted to the last 3 Myr should be linked to magma genesis. We suggest that the abrupt appearance of Loa-type magmatism should be attributed to the transient incorporation of the relatively dense recycled material and surrounding less degassed lower mantle material that accumulated near the core-mantle boundary into the upwelling plume. This episodic involvement could have been trigged by episodic thermal pulses and buoyancy increases in the plume. The continuous appearance of Kea-type lavas during the long history of Hawaiian-chain magmatism and the larger magma volume of Kea-type lavas relative to that of the Loa-type lavas in the last 3 Myr indicate that the Kea locus is closer to the thermal centre of the Hawaiian plume relative to that of the Loa locus. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2007.10.035

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOCHEMICAL SOC JAPAN  

A new 3-step sequential separation chemistry for Sr, Nd and Pb from silicate samples, which is suitable for isotope analysis by MC-ICP-MS as well as TIMS, has been developed. The chemistry is designed to minimize the number of evaporation steps, enabling high throughput especially when MC-ICP-MS is employed. The sample solution in 0.5 mol 1(-1) HNO3 after digestion with HF-HCIO4, which is prepared for trace element analysis, can be directly used in the new chemistry. In the first column using Sr resin, Sr and Pb are collected. The recovered solution for Sr can be directly aspirated into MC-ICP-MS. The Pb solution is dried, re-dissolved, separated into two aliquots and measured by double spike MC-ICP-MS. Subsequently, LREEs are collected by the second column packed with cation exchange resin. Finally, Nd was purified from Sm using Ln resin in the third column. The recovered Nd solution can also be directly nebulized into MC-ICP-MS. The Sr and Nd isotope ratios for the standard material JB-3 (basalt) from the Geological Survey of Japan by MC-ICP-MS and TIMS were reported to verify the chemistry and mass spectrometry developed in this study.

DOI： 10.2343/geochemj.42.237

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A new preconcentration technique of Zr, Nb, Mo, Hf, Ta and W has been invented employing coprecipiation with Ti compounds. Silicate samples were digested by HF with addition of Ti. Subsequent drying with HClO4 resulting in complete elimination of fluorine produces Ti compounds (oxide/hydroxides). The sample was then dissolved with dilute nitric acid and centrifuged, and the residual Ti compounds were collected. The Ti compounds forming from 2 mg of Ti without matrix elements concentrate 84-98% of Zr, Nb, Mo, Hf, Ta and W. In 20 mg basaltic and 50 mg peridotitic matrices, the addition of I nig of Ti was appropriate and gave yields of 46-69 and 54-79%, respectively, for Zr, Nb, Mo, Hf, Ta and W. Exploiting this preconcentration, sequential separation protocols of Hf, Pb, Sr, Lu, Nd and Sm for isotope analysis are developed with total blanks of 16, 11, 60, 2.4, 3 and 0.4 pg, respectively. The method is suitable for Lu-Hf system studies with capability of simultaneous separation of Pb, Sr, Nd and Sm from the same sample digest as well as isotopic anomaly studies of Zr, Mo and W. As application examples, accurate Lu-Hf data and Pb isotope ratios were obtained for basalt (JB-3) and peridotite (JP-1) by MC-ICP-MS.

DOI： 10.2343/geochemj.42.199

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A precise method of measuring Ra-228/Ra-226 for Ra-226 determination used in U-series disequilibrium studies has been developed using the total integration method with simultaneous 228Th isobaric interference correction by multicollector ICP- MS with multiple ion counters (MIC). A sample solution of 0.2 ml was separately taken into a test tube, and all Ra-226(+) and Ra-228(+) signals as well as Th-229(+) and (ThO+)-Th-228-O-16 from beginning to end were integrated simultaneously using four channeltrons, IC1, IC3, IC4 and IC5, respectively. Gains between IC1 and IC3 and the mass discrimination factor for Ra-228/ (226) Ra determination were canceled out by measurement of a Ra spike solution with an accurately known Ra isotope ratio determined by TIMS, with which samples were bracketed. The isobaric interferences of Th-228(+) were simultaneously corrected from the signal of (ThO+)-Th-228-O-16 and the oxide forming ratio of Th-228, which was separately determined by simultaneous measurements of Th-229(+) and 2(29)Th(16)O(+) by IC3 and IC5. The gains between IC3 and IC5 for the Th correction were also canceled out. The ion yield of Ra in MIC- ICP- MS was similar to 1.5%. The intermediate precision using 6.6, 3.3, 1.7, 0.83 and 0.41 fg of Ra-226 with Ra-228/Ra-226 similar to 5 was 0.33, 0.93, 0.76, 1.6 and 1.5%, respectively. The Ra-228/Ra-226 ratio showed no systematic change dependent on Th-228/Ra-228 up to 0.25, indicating the validity of the Th-228 correction. At similar amounts of Ra, our method gives intermediate precision values similar to or better than previous MC-ICP-MS and TIMS studies. The precision of the method was verified using another Ra spike with Ra-228/ Ra-226 = similar to 1 determined by TIMS. The analytical performance of the method was further investigated using the silicate samples JB-2 and JB-3 basalts issued by GSJ.

DOI： 10.1039/b807431c

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We present a Sr, Nd, Hf and Pb isotope investigation of a set of garnet clinopyroxenite xenoliths from Malaita, Solomon Islands in order to constrain crustal recycling in the Pacific mantle. Geological, thermobarometric and petrochemical evidence from previous studies strongly support an origin as a series of high-pressure (> 3 GPa) melting residues of basaltic material incorporated in peridotite, which was derived from Pacific convective mantle related to the Ontong Java Plateau magmatism. The present study reveals isotopic variations in the pyroxenites that are best explained by different extents of chemical reaction with ambient peridotite in the context of a melting of composite source mantle. Isotopic compositions of bimineralic gamet clinopyroxenites affected by ambient peridotite fall within the oceanic basalt array, similar to those of Ontong Java Plateau lavas. In contrast, a quartz-gaenet clinopyroxenite, whose major element compositions remain intact, has lower Pb-206/(204) Pb-Nd-143/(144) Nd and higher (87)sr/Sr-86-Pb-207/(204) Pb ratios than most oceanic basalts. These isotopic signatures show some affinity with proposed recycled sources such as the so-called EM-1 or DUPAL types. Constraints from major and trace element characteristics of the quartz-garnet clinopyroxenite, the large extent of Hf-Nd isotopic decoupling and the good coincidence of Ph isotopes to the Stacey-Kramers curve, all indicate that pollution of southern Pacific mantle occurred by the subduction or delamination of Neoproterozoic granulitic lower crust (0.5-1 Ga). This crustal recycling could have taken place around the suture of Rodinia supercontinent, a part of which resurfaced during mantle upwelling responsible for creating the Cretaceous Ontong Java Plateau. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2007.04.034

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We examined the coprecipitation behavior of Ti, Mo, Sn and Sb in Ca-Al-Mg fluorides under two different fluoride forming conditions: at < 70 degrees C in an ultrasonic bath (denoted as the ultrasonic method) and at 245 degrees C using a Teflon bomb (denoted as the bomb method). In the ultrasonic method, small amounts of Ti, Mo and Sn coprecipitation were observed with 100% Ca and 100% Mg fluorides. No coprecipitation of Ti, Mo, Sn and Sb in Ca-Al-Mg fluorides occurred when the sample was decomposed by the bomb method except for 100% Ca fluoride. Based on our coprecipitation observations, we have developed a simultaneous determination method for B, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by Q-pole type ICP-MS (ICP-QMS) and sector field type ICP-MS (ICP-SFMS). 9-50 mg of samples with Zr-Mo-Sn-Sb-Hf spikes were decomposed by HF using the bomb method and the ultrasonic method with B spike. The sample was then evaporated and re-dissolved into 0.5 mol FI HF, followed by the removal of fluorides by centrifuging. B, Zr, Mo, Sn, Sb and Hf were measured by ID method. Nb and Ta were measured by the ID-internal standardization method, based on Nb/Mo and Ta/Mo ratios using ICP-QMS, for which pseudo-FI was developed and applied. When 100% recovery yields of Zr and Hf are expected, Nb/Zr and TAW ratios may also be used. Ti was determined by the ID-internal standardization method, based on the Ti/Nb ratio from ICP-SFMS. Only 0.053 ml sample solution was required for measurement of all 9 elements. Dilution factors of <= 340 were aspirated without matrix effects. To demonstrate the applicability of our method, 4 carbonaceous chondrites (Ivuna, Orgueil, Cold Bokkeveld and Allende) as well as GSJ and USGS silicate reference materials of basalts, andesites and peridotites were analyzed. Our analytical results are consistent with previous studies, and the mean reproducibility of each element is 1.0-4.6% for basalts and andesites, and 6.7-11% for peridotites except for TiO2. (c) 2006 Elsevier B.V All rights reserved.

DOI： 10.1016/j.chemgeo.2006.08.007

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A double-spike multicollector ICP-MS ( DS-MC-ICP-MS) technique for Pb isotope analysis without T1 addition is established and its analytical performance is examined in detail. This simple DS-MC-ICP-MS technique using 20 ng ml(-1) gave averages of 16.9417, 15.4988 and 36.7196 with reproducibilities of 0.007, 0.008 and 0.009% ( RSD, n = 35), respectively, for Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 in NIST 981 solution, corresponding to consumption of 4 ng of Pb in a pair of spiked and non-spiked measurements. The average is consistent with those obtained by previous studies by DS-TIMS and DS-MC-ICP-MS with T1 addition. The reproducibility ( RSD %) of Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 improves from 0.26, 0.54 and 0.69% to 0.0022, 0.0030 and 0.0029% as the Pb consumption during analysis increases from 20 pg to 11 ng. The reproducibility with 11 ng is similar to or even better than those by DS-TIMS, MC-ICP-MS with T1 addition, or with DS-T1 addition. The accuracy of the simple DS-MC-ICP-MS technique for Pb, including the column chemistry, is further confirmed by analysis of actual silicate sample, JB-3.

DOI： 10.1039/b616021b

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Accurate determination methods for U-234/U-238 and Th-230/Th-232 using multiple collector (MC) ICP-MS with a single secondary electron multiplier through a retarding potential quadrupole filter (RPQ-SEM) have been developed. The RPQ-SEM yield and the instrumental mass discrimination were simultaneously corrected by the simple bracketing method which utilizes accurately determined standard solutions measured by TIMS. For the bracketing and as an evaluation of the precision of the method, four standard solutions, NBL-145 U and U-m for U, and Th-I and Th-II for Th, were prepared, and NBL-145 U and Th-I were used as bracketing standards. The U and Th amounts of 0.5-21 ng and 0.6-21 ng used in U-m and Th-II analyses gave intermediate precisions (2RSD) of 0.85-0.06 and 0.88-0.19%, respectively, and vary from TIMS measurements by <0.35 and <1.1%, respectively, which agrees with error values in TIMS analyses. To achieve similar intermediate precisions of 0.2 and 0.6% (2RSD) in the U and Th isotope analyses to that of TIMS, 3 and 2 ng of U and Th are sufficient. When only the isotope analysis is performed, the required amounts of U and Th can be reduced by half. The precision of the isotope analyses, as well as the concentration determinations, were further confirmed by analyses of U and Th separated from the GSJ standard basalt, JB-2.

DOI： 10.1039/b706907c

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A two-stage column purification method for Hf from Zr and other elements in silicate samples using the extraction chromatographic resin, UTEVA has been developed. In the first column, using an anion-exchange resin, AG 1X8, Hf, Zr and Ti were collected. In the second, using UTEVA, and after eliminating F- by evaporation with HClO4 and re-dissolution with H2O2 HNO3, Hf was purified from Ti and Zr, based on characteristic of the UTEVA resin that Hf distribution coefficient (K-d) decreases from 770 to 40, while Kd of Zr decreases less from 890 to 200, in 9 and 6 mol l(-1) HNO3, respectively. The recovery yield of Hf was B88% and total blank was similar to 4 pg. A MC-ICP-MS Hf isotope ratio determination method was also developed, which uses 179 Hf spike for simultaneous determination of the Hf concentration and Hf-176/Hf-177 ratio. Combining the chemistry and ICP-MS techniques, Hf-176/Hf-177 ratios in silicate reference materials were determined with and without the spike, which gave identical results, showing the applicability of this method.

DOI： 10.1039/b610197f

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A precise and accurate determination method of Os-187/ Os-188, Os-189/Os-188, and Re-185/Re-187 ratios of down to 0.2 pg of Os and 0.08 pg of Re using multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) with multiple ion counting has been developed. Os and Re were introduced into MC-ICPMS as 0.5 mol L-1 HF solutions through the desolvator, and Re-185, Os-187, Os-188, and Os-189 ions were detected simultaneously by four channeltrons. The Os and Re ratios were determined by the standard bracketing method, in which channeltron yields and mass discrimination factors are corrected together. Os and Re memories after 800-s wash were < 0.1% and negligible, typically 0.02 and 0.03%, respectively. Isotope ratios of Os-187/ Os-188, Os-189/Os-188, and Re-185/Re-187 were constant within error in the concentration ranges of 1-100, 1-40, and 0.4-5 pg mL(-1) with reproducibility (1 sigma) of 2.7-0.14, 0.33-0.10, and 0.41-0.19%, respectively. For analysis of larger amounts of Os and Re, the Faraday cup measurement was employed. The precision and reproducibility obtained in this study are comparable to those of N-TIMS and better than MC-ICPMS achieved so far with a capability of higher sample throughput with simpler sample preparation.

DOI： 10.1021/ac060183t

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOSTANDARDS  

A method for the determination of major, minor and trace elements in silicate samples by ICP-QMS and ICP-SFMS applying isotope dilution-internal standardisation (ID-IS) and multi-stage internal standardisation has been developed. Samples with an enriched isotope of Sm-149(spike) were decomposed by a HF/HClO4 mixture and stepwise drying and finally diluted. In ID-IS for trace element analyses by Q-pole type ICP-MS (ICP-QMS), the Sm concentration was determined by ID, while other trace elements (Li, Be, R6, Sr, Y, In, Cs, Ba, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Tl, Pb, Bi, Th and U) were determined using the Sm-149 intensity as an internal standard. Major and minor elements were determined by multi-stage internal standardisation, with Na, Mg, Al, R Ca, V, Mn, Fe and Co measured by sector magnetic field type ICP-MS (ICP-SFMS) at middle resolution (MR; M/Delta M = similar to 3000) using Sr determined by ICP-QMS in the sample as the internal standard. Potassium, Sc, Ni, Cu, Zn and Ga were measured at high resolution (HR; M/Delta M similar to 7500) using the Sr concentration obtained by ICP-QMS or the Mn concentration obtained by ICP-SFMS at MR as internal standard. The merit of ID-IS is that accurate dilution of the sample is not required. Matrix effects on elemental ratios down to a dilution factor (DF) of 600 were not observed in either types of mass spectrometry. Pseudo-flow injection (FI), where transient signals were integrated, was used in ICP-QMS, while conventional continuous sample introduction was used in ICP-SFMS, resulting in total required sample solutions of 0.026 ml and 0.08 ml, respectively. Detection limits were low enough to determine these elements in depleted ultramafic rocks, and typical reproducibilities for basalts were 3% (Li-Be), 11% (Rb-U), 5% (In, Tl and Bi), 7% (Sc-Ga) and 3% (major elements). Carbonaceous chondrites including Orgueil (Cl1), Murchison (CM2) and Allende (CV3), as well as reference materials, JB-1, -2,-3, JA-1, -2,-3 and JP-1 (GSJ), BHVO-1, AGV-1, PCC-1 and DTS-1 (USGS), were analysed to show the applicability of this method.

DOI： 10.1111/j.1751-908X.2006.tb01066.x

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The natural variation of Mg and Ca stable isotopes of carbonates has been determined in carbonate skeletons of perforate foraminifera and reef coral together with Mg/Ca ratios to assess the influence of biomineralisation processes. The results for coral aragonite suggest its formation, in terms of stable isotope behaviour, approximates to inorganic precipitation from a seawater reservoir. In contrast, results for foraminifera calcite suggest a marked biological control on Mg isotope ratios presumably related to its low Mg content compared with seawater. The bearing of these observations on the use of Mg and Ca isotopes as proxies in paleoceanography is considered. © 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bbrc.2004.08.053

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Language：English   Publisher：Japan Association of Mineralogical Sciences  

Simultaneous determination of Li, Be, Rb, Sr, Y, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Th and U by isotope dilution and internal standardization (ID-IS) method by ICP-MS was developed.

DOI： 10.14824/jampeg.2004.0.64.0

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A precise and simple method for the determination of lithium concentrations in small amounts of silicate sample was developed by applying isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS). Samples plus a Li spike were digested with HF-HClO4, dried and diluted with HNO3, and measured by ICP-MS. No matrix effects were observed for 7Li/6Li in rock solutions with a dilution factor (DF) of ≥ 97 at an ICP power of 1.7 kW. By this method, the determination of 0.5 μg g-1 Li in a silicate sample of 1 mg can be made with a blank correction of < 1%. Lithium contents of ultrabasic to acidic silicate reference materials (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR-1 and JR-2 from the Geological Survey of Japan, and PCC-1 from the US Geological Survey) and chondrites (three different Allende and one Murchison sample) of 8 to 81 mg were determined. The relative standard deviation (RSD) was typically < 1.7%. Lithium contents of these samples were further determined by isotope dilution-thermal ionisation mass spectrometry (ID-TIMS). The relative differences between ID-ICP-MS and ID-TIMS were typically < 2%, indicating the high accuracy of ID-ICP-MS developed in this study.

DOI： 10.1111/j.1751-908X.2004.tb00756.x

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A technique for separation of Mg, with 100% yield from low-Mg biogenic carbonates has been developed suitable for high precision analysis of Mg isotopes by multiple-collector inductively coupled plasma mass spectrometry. Two separate stages of ion-exchange chromatography were carried out using cation exchange resin, AG50W-X12 with a Mg recovery >99.9%. The repeatability of the Mg isotope ratio measurement using this technique including chemistry and mass spectrometry is ±0.14‰ on δ26Mg and ±0.09‰ on δ25Mg at 95% confidence. This was demonstrated using a synthetic solution (Na : Mg : Ca : Sr = 2 : 1 : 100 : 1 in weight) over a period of six months. The robustness of the technique was further assessed by replicate analyses of three natural samples, seawater, foraminifera and dolomite. A total variation over 4.5‰ on δ26Mg was observed and the Mg isotope composition of seawater was 2.59 ± 0.14‰ on δ26Mg and 1.33 ± 0.09‰ on δ25Mg which were the highest isotope ratios among the samples measured. © The Royal Society of Chemistry 2003.

DOI： 10.1039/b210977h

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We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca-Al-Mg-HF solution system using two different methods: at <70°C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205°C using a TFE Teflon® bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an 'Al-addition method' was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we found isotopic disequilibria of Zr and Hf between sample and spike without Aladdition for Ca-rich samples, and that the Al-addition method was very effective in achieving isotopic equilibria and full recovery of HFSE, resulting in high accuracy in their determination. © The Royal Society of Chemistry 2003.

DOI： 10.1039/b309948b

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DOI： 10.1039/b309948b

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DOI： 10.1021/ac025962y

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A method using multiple-collector inductively coupled plasma source mass spectrometry for the precise measurement of Ti isotope composition in natural materials has been developed. Instrumental mass discrimination is corrected using a "standard-sample bracketing" approach by expressing the isotope ratios of samples relative to those of the bracketing standard. Variations in 47Ti/46Ti, 48Ti/46Ti, 49Ti/46Ti and 50Ti/46Ti ratios of samples are expressed in ε units which are deviations in parts per 104 from the same isotope ratios of the reference material. The long-term repeatability at the 2 standard deviation level is 0.4, 0.6, 0.7 and 0.8 ε units in terms of 47Ti/46Ti, 48Ti/46Ti, 49Ti/46Ti and 50Ti/46Ti ratio measurements, respectively. The technique reported here makes it possible for the first time that both mass-dependent fractionation and isotope anomalies of Ti isotopes in natural materials can be measured to high precision. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1387-3806(02)00767-4

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A simple and accurate method for the determination of Cr, Ni, Cu and Zn at μg g-1 levels in milligram-sized bulk silicate materials is reported using isotope dilution high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) with a flow injection system. Silicate samples with Cr, Ni, Cu and Zn spikes were digested with HF-HBr and Br2, and subsequently decomposed at 518 K in a Teflon bomb. In this procedure, all sulfides and chromite, major hosts of these elements, were completely decomposed, thus allowing for isotope equilibration between the sample and spike. Magnesium and Al fluorides formed after the digestion of the sample were removed by centrifugation, and the supernatant was directly aspirated into a HR-ICP-MS at a mass resolution of 7500, where interfering oxide ions, ArO +, CaO+, TiO+, CrO+ and VO +, were separated from Cr+, Ni+, Cu+ and Zn+. No matrix effects were observed down to a dilution factor of 50. Detection limits for these elements in silicate samples were < 0.04 μg g-1. The effectiveness of the technique was demonstrated by the analysis of 13 to 40 mg test portions of USGS and GSJ silicate reference materials with a major element composition ranging from andesite to peridotite, in addition to 8-23 mg of the Smithsonian reference Allende. Both the reproducibility and the deviation from the reference value for most reference materials of various rock types were < 9%, and thus confirm that the method gives accurate analytical results for small sample sizes over a wide range of Cr, Ni, Cu and Zn contents. This method is, therefore, suitable for analysing small and/or precious bulk samples, such as meteorites, mantle peridotites and mineral separates, and for the characterisation of silicate and sulfide minerals for use as calibration samples in secondary ion mass spectrometry or laser ablation ICP-MS.

DOI： 10.1111/j.1751-908X.2002.tb00622.x

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A new separation method of Ti from silicate materials is presented that is suitable for the determination of natural Ti isotope variations using multi-collector inductively coupled plasma source mass spectrometry (MC-ICP-MS). This method makes possible for the first time the separation of Ti from natural materials, with high purity, high recovery and no introduction of artificial mass fractionation. Following sample decomposition using HF, Ti is separated using a three-column procedure. In the first column using an anion-exchange resin, AG 1X8, major elements and the majority of trace elements are separated. In the second column, after eliminating F- by evaporation with HClO4 and re-dissolution with H2O2-HNO3, Ti is separated from Zr and Hf using a liquid-liquid extraction resin, U/TEVA. In the third column, which is the same as the first column, trace amounts of Al and P are further removed. Recovery yields were almost unity, and no Ti isotope fractionation occurred from the overall chemical processing. The reproducibilities (2σ) of the Ti isotope ratio measurement for a meteorite (eucrite) and a lamproite were <0.5ε for ε47Ti, ε48Ti and ε49Ti, and <1ε for ε50Ti, which were comparable to those for the pure Ti standard solution.

DOI： 10.1039/b204349a

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A new group separation method for Re and PGE (Ru, Pd, Os, Ir, Pt) is described using a novel anion exchange chromatographic resin called TEVA. Re and PGEs are converted into bromo complexes by heating with HF-HBr mixture in a Teflon bomb at 518 K, by in situ-generated Br2 formed by reaction of HBr and HNO3. Distribution coefficients (Kd) of the bromo complexes onto TEVA resin in 0.1 M HBr with heating at 353 K for one night were 2200, 16000, 1600, 5500, 4000, and 17 000 for Ru, Pd, Re, Os, Ir, and Pt, respectively, thus allowing 97% recovery of Re and PGEs in 5 mL of solution by 0.1 mL of resin. These strongly bound Re and PGE bromo complexes are stripped and recovered >90% by the following three steps: (i) addition of 6 M HCI at 353 K and 2.2 M HCI-5 M HBr at 353 K; (ii) heating the resin in 6 M HCI at 353 K to convert the bromo complexes into the chloro complexes with weaker affinities to the resin; and (iii) sequential addition of the HCI-HBr mixture at room temperature and 7 M HI. Neither the elution profile nor the recovery yield for a 0.2-g geological sample showed significant changes, indicating minimal matrix effects for the geological samples. Total blanks were <14 pg for Ru, Pd, and Pt and <10 pg for Re, Os, and Ir. This new technique, therefore, is suitable for simultaneous determination of subnanogram per gram of Ru, Pd, Re, Os, Ir, and Pt and Os isotope analysis in geological, mineralogical, and environmental samples without direct addition of toxic reagents required in distillation/extraction of Os or oxidizing of Ir.

DOI： 10.1021/ac010615u

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We have developed a new, simple, and accurate method for the determination of total sulfur at microgram per gram levels in milligram-sized silicate materials with isotope dilution high-resolution inductively coupled plasma mass spectrometry equipped with a flow injection system. In this method, sulfur can be quantitatively oxidized by bromine into sulfate with achievement of isotope equilibrium between the sample and spike. Detection limits for 32S+ and 34S+ in the ideal solution and silicate samples were 1 and 6 ng mL-1 and 0.07 and 0.3 μg g-1, respectively. The total blank was 46 ng, so that a 40-mg silicate sample containing 10 μg g-1 sulfur can be measured with a blank correction of < 10%. This total blank can be lowered to 8 ng if a low-blank air system is used for evaporations. To evaluate the applicability of this method, we analyzed not only silicate reference materials with sulfur content of 5.25-489 μg g-1 and sample sizes of 13-40 mg but also the Allende meteorite with a sulfur content of 2%. The reproducibility for various rock types was <9%, even though blank corrections in some samples of low sulfur content were up to 24%. This method is suitable for analyzing geological samples as well environmental samples such as soils, sediments, and water samples.

DOI： 10.1021/ac001550i

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An aluminum fluoride, AlF3, forms during HF digestion of felsic rock samples, for trace element and isotope geochemistry, which use a Teflon bomb at high temperature and pressure. The AlF3 incorporates trace elements (Rb, Sr, Y, Cs, Ba, REE, Pb, Th, and U), and can not be decomposed by conventional methods such as evaporation with HClO4. The production of this AlF3 results in lower yields and poor accuracy in analyses of these trace elements by ICP-MS. The formation of AlF3 is controlled by the chemical composition of the rock samples, in particular, AlF3 does not form during decomposition of mafic samples with relatively high (Mg+Ca)/Al ratios. We have developed a new method to suppress the AlF3 formation, in which excess Mg is added to the sample prior to acid digestion in the bomb. This new method makes it possible to accurately determine the trace element compositions of higher-Al rock samples with lower concentrations of Mg and Ca (e.g. rhyolite and granite). In the trace element analyses by TIMS with isotope dilution techniques (ID-TIMS), AlF3 formation hinders the achievement of isotope equilibrium, resulting in erroneous results. However, the Mg-addition method removed this problem by suppression of AlF3 formation.

DOI： 10.2183/pjab.77.13

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We have developed a new, highly precise method for U isotopic analysis using a thermal ionization mass spectrometry (TIMS) by measuring UO+2 ions emitted from a very small amount (100- 10 ng) of U. A new ionization activator, a silicic acid-diluted phosphoric acid solution, was found to be effective not only for producing a strong and stable UO+2 ion beam, but also for keeping the mass fractionation during measurement small and constant. U isotope analysis was carried out by a "dynamic multi collection" method using three Faraday cup collectors and a secondary electron multiplier in ion counting mode with RPQ (RPQ-SEM). For precise isotope analysis, baselines of the Faraday cups and a conversion factor between Faraday cups and the RPQ-SEM were precisely determined simultaneously with U isotope collection. Analytical precision and reproducibility of 234U/238U ratio ranged from 0.10% to 0.38% (2σmean) and from 0.13% to 0.31% (2σ), respectively, for 100-10 ng of U extracted from a natural rhyolitic obsidian. The precision and reproducibility were improved compared with previous studies, and thus, our method is especially useful for samples with very low abundance of U. © 2001 Elsevier Science B. V. All rights reserved.

DOI： 10.1016/S0009-2541(01)00270-4

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An accurate method for the determination of Ti at μg g-1 levels in milligram amounts of silicate materials with isotope dilution high-resolution inductively coupled plasma mass spectrometry equipped with flow injection system (ID-FI-HR-ICP-MS) is presented. The chemical procedure requires HF digestion of the sample with the Ti spike, subsequent evaporation and dissolution of Ti with HF in order to separate from Mg and Ca fluorides formed after the digestion of the sample. A 10 mg silicate sample containing 0.002% TiO2 was measured with a blank correction of <5%. To demonstrate the applicability of this method, peridotite reference materials, PCC-1 and DTS-1, from the US Geological Survey (USGS) and JP-1 from the Geological Survey of Japan (GSJ) were analyzed (12-33 mg), to determine TiO2 content. The reproducibility was 3% for these peridotites with TiO2 contents of 0.003-0.004%. This method also gave TiO2 contents in BCR-1, BHVO-1 and AGV-1 from USGS and JB-1, -2, -3, JA-1, -2, and -3 from GSJ with reproducibility of 1-5% using test portions of 6-18 mg.

DOI： 10.1039/a909020g

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Insoluble fluoride precipitates which form during HF digestion of mafic silicate rocks coprecipitate in their structures the trace elements such as Rb, Sr, Y, Cs, Ba, REE, Pb, Th and U, thus hindering their accurate determination. We have estimated quantitatively the coprecipitation of trace elements into such fluorides, and suggest an effective method of digestion that can suppress completely fluoride precipitation. Conventional acid digestion of three samples of mafic and ultramafic silicate rocks resulted in the precipitation of sticky material and very poor yields of certain trace element in the resultant solution. XRD analysis indicated that the precipitates were composed of fluorides such as CaAlF5, CaMg2Al2F12, Na0.88Mg0.88Al1.12(F,OH)6 · H2O and MgF2, the formation of which depended on the major element composition of the rock sample. Coprecipitation of trace elements appeared to be strongly controlled by both ionic radius and valency of the elements as well as the species of the host fluoride precipitate, resulting in selective losses of the elements into these fluorides. On the other hand, almost 100% of the trace elements were recovered using larger amounts of HCIO4 than is conventionally used and evaporating the sample to dryness in a step-wise fashion. Using this method, white precipitates were formed as oxides of high field strength elements after decomposition of the sample. Coprecipitation of trace elements of interest in this study with the oxides is negligible except for Th for which 0.5-3.2% by weight was coprecipitated probably as the insoluble oxide. As our method also results in negligible blank values, it can be used for both the accurate determination of trace element using ICP-MS as well as isotope analysis using TIMS.

DOI： 10.1016/S0009-2541(98)00206-X

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We have developed a rapid and accurate method for the determination of Mo, Sb and W in geological samples using isotope dilution inductively coupled plasma-mass spectrometry with a flow injection system (ID-FI-ICP-MS). The chemical procedure requires HF digestion of the sample with a Mo-Sb-W mixed spike, subsequent evaporation and dissolution of Mo, Sb and W from Mg and Ca fluorides with HF. Recovery yields of Mo, Sb and W in the extraction were > 94% for samples of peridotite, basalt and andesite composition, with the exception of W in samples of peridotite composition for which recovery was 81%. No matrix effects were observed in the determination of the isotope ratios of Mo, Sb and W in solutions prepared from peridotite, basalt and andesite samples down to a dilution factor of 100. Detection limits of Mo, Sb and W in silicate materials were at the several ng g-1 level. Analysis of the silicate reference materials PCC-1, DTS-1, BCR-1, BHVO-1, AGV-1 from the US Geological Survey and JP-1, JB-1, -2, -3, JA-1, -2, and -3 from the Geological Survey of Japan as well as the Smithsonian reference Allende powder yielded reliable Mo, Sb and W concentrations. The repeatability in the analysis of basalts and andesites was < 9%. This technique requires only 0.2 ml sample solution, and is therefore suitable for analyzing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates.

DOI： 10.1111/j.1751-908X.1999.tb00569.x

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We have developed a rapid and accurate method to determine Zr, Nb, Hf and Ta (denoted as HFSE) in geological samples by inductively coupled plasma-mass spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE coprecipitated with insoluble Mg and Ca fluoride residues formed during the initial HF attack. This HF solution was directly nebulized into an ICP mass spectrometer. An external calibration curve method and an isotope dilution method (ID) were applied for the determination of Nb and Ta, and of Zr and Hf, respectively. Recovery yields of HFSE were, 96% for peridotite, basalt and andesite compositions, apart from Zr and Hf for peridotite (> 85%). No matrix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 and 0.1 ng g-1 for Zr, Nb, Hf and Ta, respectively. This technique required only 0.1 ml of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates. We also present newly determined data for the Zr, Nb, Hf and Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR-1, BHVO-1 and AGV-1, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3, and the Smithsonian reference Allende powder.

DOI： 10.1111/j.1751-908X.1999.tb00555.x

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A new chemical separation technique to isolate Th and U from silicate rocks was established by using two kinds of commercial extraction Chromatographic resins. In the first column procedure, with U/TEVA·spec resin, almost all elements except Th and U were eluted by 4 M HNO3. Th was then separated by using 5 M HC1, and U was finally isolated by successive addition of 0.1 M HNO3. A significant amount of Zr still remained in the Th fraction, which was then further purified in the second column stage using TEVA·spec resin. In the second procedure, Zr was eluted first by using 2 M HNO3, and then Th was collected by 0.1 M HNO3. Both the Th and U fractions obtained by these procedures were sufficiently pure for thermal ionization mass spectrometric (TIMS) analysis. Recovery yields of Th and U exceeded 90%, and total blanks were <19 pg for Th and <10 pg for U. Our method has advantages over previous methods in terms of matrix effects, tailing problems, and degree of isolation. Since Th and U are effectively separated without suffering any matrix interference from coexisting cations and anions, this technique can be used not only for the analysis of igneous rock samples but also for the analysis of soils, marine sediments, carbonates, phosphates and seawater, groundwater, and surface water. © 1998 American Chemical Society.

DOI： 10.1021/ac9805807

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A rapid and precise technique for the determination of boron content in silicate rocks was developed by employing isotope dilution inductively coupled plasma mass spectrometry with a flow injection system (FI-ID-ICPMS). The sample was decomposed with HF and mannitol, dried to remove silicon as gas, and redissolved with HF to extract boron from the fluoride residue. Ultimately, the HF solution was directly aspirated into the ICPMS. The total procedural blank was 0.08-0.36 ng. No matrix-induced mass discrimination was observed in the rock solution for dilution factors of up to 110. The present method is capable of determining 1 μg g-1 boron in a 1 mg silicate rock sample with blank correction of <20%. Replicate analyses of USGS rock standards, PCC-1, BCR-1, and AGV-1, and GSJ rock standards, JB-1, JB-2, JB-3, JA-1, JA-2, and JA-3, yielded reproducibilities (RSD) of <2%. These results were identical with those obtained by ID thermal ionization mass spectrometry within the analytical errors. These results indicate that the present method allows the precise determination of the boron content in a small sample of silicate materials with simple handling, resulting in the extremely low procedural blank of boron.

DOI： 10.1021/ac970383s

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Isotopic compositions of Sr, Nd and Pb and REE concentrations have been determined for samples from "isotopically anomalous" Akagi volcano locating on the volcanic front of Northeast Japan Arc. The Sr isotopic compositions show a large variation with highly enriched isotope character (87Sr/86Sr=0.7060 to 0.7088) compared to those from other volcanoes on the front. The Nd isotopic compositions, ranging from εNd = -0.40 to -8.6, have a negative correlation with the Sr isotopic compositions. The Pb isotopic data along with Sr and Nd isotope systematics clearly indicate that the isotopic variations of Akagi volcano were caused by a two-component mixing between an end member isotopically similar to the primary magma on the volcanic front of Northeast Japan Arc and a lower crustal component. Chondrite-normalized REE patterns of Akagi samples show U-shaped, HREE-depleted pattern with positive Eu anomaly. Such REE features may have been developed by fractionation of amphibole formed by the reaction between a fluid-rich magma and clinopyroxene in granulitic lower crust. The fluid-rich magma could be originated from a highly metasomatized mantle wedge caused by the dehydration of oceanic slabs of the Pacific plate and the overlapping Philippine Sea Plate. Such a unique tectonic setting could result in higher water supply to the source region of magma than normal circumstances and thereby generating fluid-rich magma which could enhance assimilation of lower crust beneath Akagi volcano.

DOI： 10.2183/pjab.73.69

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We found that the suppression of signals for 88Sr, 140Ce and 238U in rock solution caused by rock matrix in ICP-MS (matrix effects) was reduced at high power operation (1.7 kW) of the ICP. To make the signal suppression by the matrix negligible, minimum dilution factors (DF) of the rock solution for Sr, Ce and U were 600, 400 and 113 at 1.1, 1.4 and 1.7 kW, respectively. Based on these findings, a rapid and precise determination method for Rb, Sr, Y, Cs, Ba, REE, Pb, Th and U using Fl (flow injection)-ICP-MS was developed. The amount of the sample solution required for FI-ICP-MS was 0.2 ml, so that 1.8 mg sample was sufficient for analysis with a detection limit of several ng g-1. Using this method, we determined the trace element concentrations in the USGS rock reference materials, DTS-1, PCC-1, BCR-1 and AGV-1, and the GSJ rock reference materials, JP-1, JB-1, -2, -3, JA-1, -2 and -3. The reproducibilities (RSD%) in replicate analyses (n=5) of BCR-1, AGV-1, JB-1, -2, -3, JA-1, -2, and -3 were < 6%, and typically 2.5%. The difference between the average concentrations of this study for BCR-1 and those of the reference values were < 2%. Therefore, it was concluded that the method can give reliable data for trace elements in silicate rocks.

DOI： 10.1111/j.1751-908X.1997.tb00678.x

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Isotope ratios of Ce, Nd and Sr, and light rare-earth elements (La, Ce, Nd and Sm) concentrations were measured for sixteen N-type MORB samples from DSDP Sites 420, 421, 429, 597B and 597C (East Pacific Rise), 504B (Costa Rica Rift), and 395, 519A, 522B, 562 and 564 (Mid Atlantic Ridge). All the samples were confirmed as N-type MORB based on Nd and Sr isotope ratios, and LREE patterns. The Ce isotope ratios ranged from 0.0225616 (ε{lunate}Ce = - 1.6) to 0.0225633 (ε{lunate}Ce = - 1.0). Averages of ε{lunate}Ce and ε{lunate}Nd of N-type MORB were - 1.4 and 9.5, respectively. The average of ε{lunate}Ce is quite different from previous estimates. We propose that ε{lunate}Ce = - 1.4 should be used as the typical MORB Ce isotope ratio in future studies. © 1994.

DOI： 10.1016/0009-2541(94)90166-X

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LREE (La, Ce, Nd and Sm) concentrations, and 143Nd/144Nd and 138Ce/142Ce ratios of two powder aliquots from the bulk Allende meteorite (BAM) were measured to investigate p-isotopic anomalies of Ce. Initial Ce isotope ratios of the two aliquots were calculated assuming an age of 4.56 Ga, identical with ages of other chondrites or eucrites. From the data, we conclude that there are no recognizable p-isotopic anomalies in BAM. This suggests that the existence of p-isotopic anomalies of other REE in BAM is unlikely. Our data can not, however, rule out the possibility that this is only caused by averaging of heterogeneous distribution of p-isotopic anomalies. © 1994, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.

DOI： 10.2343/geochemj.28.115

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Ce and Nd isotope ratios and REE contents of one carbonaceous chondrite (Murchison), 3 ordinary chondrites (Granès, Holbrook and Barwise) and 4 achondrites (Camel Donga, Juvinas, two pieces of Millbillillie) were measured. For the Ce isotope analysis of meteorite samples the new chemistry for extracting Ce from the gel formed after decomposition of ∼1-g chondrite sample with Mg content of 20% was developed with a recovery yield of 80%. The initial Ce isotope ratio of each meteorite sample was calculated with the assumption that the age of meteorite samples is 4.56 Ga, and the average value was obtained to be 138Ce/142Ce-0.0225321 ± 0.0000007 (2σ), which is considered to be the primordial Ce isotopic composition of the solar system. The average of the present-day Ce isotope ratios of the chondrites of this study and that previously published by Shimizu et al. is 0.0225653, which suggests that the estimation of the Ce isotope ratio of the present-day bulk Earth of 0.0225652 that was published by Makishima and Nakamura is convincing. The Ce isotope ratio of the present-day bulk Earth of 0.0225652 gives the 138La/142Ce ratio of the bulk Earth to be 0.00306 ± 0.00006 (2σ), which corresponds to La/Ce = 0.375 ± 0.007 (2σ). We propose that the La/Ce ratio of 0.375 represents that of the bulk Earth or CHUR. © 1993.

DOI： 10.1016/0009-2541(93)90026-F

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The β-decay constant of 138La has been geochronologically determined using Archean granites from the Yilgarn Block, Western Australia. RbSr and SmNd mineral isochron ages were obtained for the two granite samples, which are nearly identical with the ion microprobe UPb zircon ages. This agreement indicates that the closure date for these samples is the same, within analytical error, making them suitable for geochronological estimation of the β-decay constant for 138La. Applying a new method of Ce isotope analysis, with analytical reproducibility of ±0.008%, LaCe isotope data for the studied samples resulted in precise mineral isochrons. Based on these internal mineral isochrons and ages determined by other geological clocks, the β-decay constant for 138La was estimated to be (2.33 ± 0.24)·10-12a-1 (2σ). © 1993.

DOI： 10.1016/0009-2541(93)90158-F

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The origin of p-isotopes (proton rich isotopes) and their isotopic anomalies are reviewed in this article. The p-isotopes (⁸⁴Sr,¹²⁴Xe, ¹³⁰Ba, ¹⁴⁴Sm, ¹⁹⁶Hg, etc.) are heavy isotopes (A≧74) which cannot be synthesized by s-process or r-process. The p-isotopes are considered to be produced by the transmutation of heavy elements into lighter p-isotopes via a series of (γ, n), (γ, p) and (γ, α) reactions in supernovae. We can constrain the site and the condition of nucleosynthesis in supernovae from abundances of the p-isotopes. The isotopic anomalies of the p-isotopes of Xe, Cd and Sn are found in acid residues of the Allende carbonaceous chondrite. The anomalies of ⁸⁴Sr and ¹⁴⁴Sm are also found in the Allende FUN inclusions. They are considered to be presolar origin. The anomalies of ¹⁹⁶Hg are found, however, their origin still remains enigmatic. The anomaly of Mo isotopic abundances is found in the Sikhote-Alin iron meteorite. The anomaly can be explained by (γ, n) reaction chains of Mo. The further study of the Mo anomaly will give us interesting informations not only about the p-process, but also about the r-process effect on ⁹³Nb, the double β^--decay of ⁹⁶Zr, and the (γ, n) reaction chain of ⁹⁹Tc.

DOI： 10.14934/chikyukagaku.26.41

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Faraday cup efficiencies (FCE's) in the multicollector mass spectrometer were examined with a static multicollcction technique. The relative Faraday cup efficiency (RFCE) was estimated by measurement of Nd-isotopc ratios with five different cup configurations. The application of RFCE correction to the static multicollection technique will increase the reliability of analytical results by eliminating the errors caused by differences in FCE's, and will also enable us to distinguish which Faraday cups are damaged and should be renewed. © 1991, All rights reserved.

DOI： 10.1016/S0009-2541(10)80022-1

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A high-precision analytical method for the measurement of 138Ce/142Ce ratios is reported using static multicollection mass spectrometry. This technique reduced the data acquisition time for 2 hr. for 400 ratios and improved analytical reproducibility to ±0.002% (n = 16) and precision to ±0.002–0.003%. The better precision and reproducibility were established collecting a large ion beam [ 142Ce16O of (2–7 ) · 10−11 A], short data acquisition time and in situ measurement of 18O/16O ratios during the analysis. To reduce the blank effect to the Ce isotope analysis, the chemical procedure for separation of Ce was refined using a small ion-exchange resin bed column (4 cm length × 3 mm diameter) with which the procedural total blank was lowered to 0.04 ng and the recovery yield of Ce from 20 mg BCR-1 was 90%. In order to confirm the reproducibility of this technique including the chemical procedure, six Ce isotope analyses individually separated from the USGS standard BCR-1, were carried out with an analytical reproducibility of ±0.002%. With these analytical precision and reproducibility and normalization to BCR-1 in order to eliminate any inter-laboratory biases, it is now possible to apply the La-Ce isotope system to the terrestrial and extraterrestrial samples combined with other isotope systems, such as Sm-Nd and Rb-Sr. © 1991, All rights reserved.

DOI： 10.1016/S0009-2541(10)80012-9

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The surface oxide layer of additionally oxidized iron particles for magnetic recording in high humidity (90%) and at 60°C was examined by Mossbauer spectrometry. The mechanism of deterioration was concluded to begin with oxidation: the deterioration of the saturation magnetization (Is) of iron particles was caused by a deterioration of the Is of the surface oxide layer; later deterioration was caused by an increase in the amount of the oxide layer. The specific gravity of the surface oxide layer became gradually reduced during the oxidation.

DOI： 10.1246/bcsj.63.3189

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Isotope dilution analysis with inductively coupled plasma mass spectrometry (ICP-MS) was applied to the determination of gallium in pure aluminum. Furthermore, a solvent extraction procedure was combined with isotope dilution analysis as a preconcentration technique in order to determine ultra-trace levels of gallium with high precision. The accuracy and the precision of isotope dilution analysis using ICP-MS were compared with those of conventional standard addition analysis using ICP-MS. Isotope dilution analysis gave more accurate and precise results than did standard addition analysis. Isotope dilution analysis with solvent extraction made it possible to measure 0.029 μg/g gallium in 99.999% aluminum with analytical errors at less than 3%.

DOI： 10.1366/0003702904085840

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The average valency of iron in the oxide layer on iron particles for magnetic recording and the saturation magnetization of the oxide layer were estimated to be 2.8 and 39 emu g-1, respectively, by examining the Debye temperature and the recoilless fraction of oxide layer which were calculated with the Mossbauer parameters.

DOI： 10.1246/bcsj.63.147

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：The Mass Spectrometry Society of Japan  

Tanaka and Masuda¹⁾ first applied lanthanum-cerium isotope systematics to geochronology in 1982, using β-decay of ¹³⁸La. In this systematics, it is necessary to measure cerium isotope ratio (ex. ¹³⁸Ce/¹⁴²Ce) with precision better than 0.01% because of long half life and low abundance of ¹³⁸La. Many studies have been done to improve the precision and accuracy of the Ce isotope analysis. But there are some problems in the analysis, such as long data acquisition time and requirement of large amount of cerium. When the La-Ce systematics is used as a geochemical tracer or in geochronology, β-decay constant of ¹³⁸La is a very important factor. However, the decay constant is still in controversy so that age dating results using the La-Ce isotope systematics are less convinced compared with those of Sm-Nd and Rb-Sr systematics.<br>In this paper, precise measurements of cerium isotope ratios and geochronological applications are reviewed and their problems are pointed out.

DOI： 10.5702/massspec.38.165

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LaCe ages are reported for two sets of Finnish pegmatites, Lövböle and Mustikkamäki, and for an Amîtsoq gneiss, Greenland. When λβ 138La value (2.29 × 10-12 yr-1) obtained by radioactivity measurement [1] is used for the chronological calculation, the LaCe ages (2129, 2325, 3271 Myr) evaluated for these rocks are 18-35% older than the SmNd ages for the same samples. To make the LaCe age fit to the SmNd age for the same sample, a new value of (2.77 ± 0.21) × 10-12 yr-1 is evaluated for λβ 138La. In this calculation, the LaCe and SmNd ages reported for a Bushveld gabbro [2] have been also taken into account together with those for the Lövböle pegmatite and the Mustikkamäki pegmatite, while the Amîtsoq gneiss (GGU110999) has been omitted because of the complicated thermal history of this sample. © 1988.

DOI： 10.1016/0012-821X(88)90119-7

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Mass Spectrometry Society of Japan  

The isotope ratios of cerium and lanthanum are determined precisely by a surface ionization mass spectrometer. ¹³⁸Ce/¹⁴²Ce and ¹⁴⁰Ce/¹⁴²Ce ratios for Ce standard solution are 0.0225762± 0.0000014 (2σ) and 7.9471±0.0003 (2σ), normalized to ¹³⁶Ce/¹⁴²Ce=0.01688, respectively. ¹³⁸La/¹³⁹La ratio is 0.0009025±0.0000005 (2σ). The oxygen isotope ratios in measurements of REE as oxide ions are 0.0003916±0.0000014 (2σ) and 0.002129±0.000010 (2σ) for ¹⁷O/¹⁶O and ¹⁸O/¹⁶O. The isotopic abundances (%) of ¹³⁶Ce, ¹³⁸Ce, ¹⁴⁰Ce and ¹⁴²Ce are calculated to be 0.1878, 0.2512, 88.433 and 11.128, respectively. The isotopic abundances (%) of ¹³⁸La and ¹³⁹La are calculated to be 0.09016 and 99.9098. These isotopic abundances obtained here give the following relation:<br>(¹³⁸La/¹⁴²Ce)_ATOMIC=0.008173×(La/Ce)_WEIGHT.<br>These precise isotopic abundances on Ce and La are fundamental values in a La-Ce geochronometer.

DOI： 10.5702/massspec.35.64

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