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Using the Rock Canyon Creek carbonate-hosted rare earth element (REE)–F–Ba deposit as an example, we demonstrate the need for verifying inherited geochemical data prior to reinterpretation. Inherited La, Ce, Nd and Sm data obtained by pressed pellet X-ray fluorescence (XRF), and La and Y data obtained by aqua regia digestion inductively coupled plasma atomic emission spectroscopy (ICP-AES) for more than 300 drill-core samples were analysed in 2009 and were subsequently compared to sample subsets re-analysed using lithium metaborate-tetraborate (LMB) fusion ICP mass spectroscopy (ICP-MS), Na2O2 fusion ICP-MS, and LMB fusion-XRF. We determine that LMB ICP-MS and Na2O2 ICP-MS accurately determined REE concentrations in control reference materials (CRM) SY-2 and SY-4, and provided precision of about 10%. Fusion-XRF was precise for La, Ce and Nd at concentrations greater than ten times the lower detection limit; however, accuracy of this method was not established because REE concentrations in SY-4 were below the lower detection limit. Analysis of the sample subset revealed substantial discrepancies for Ce concentrations determined by pressed pellet XRF in comparison to those determined by other methods due to Ba spectral interference. Samarium, present in lower concentrations than other REE that were determined, was consistently underestimated by XRF methods relative to ICP-MS methods. This may be the result of Sm concentrations approaching the lower detection limits of XRF methods, elemental interference or inadequate background corrections. Aqua regia dissolution results, reporting only for La and Y, are underestimated relative to the other methods. We highlight the importance of selecting the most appropriate analytical method and reference materials for determining the REE content of mineralized rock which may be several orders of magnitude higher than that of typical host rock.

Weathered granite of ion-adsorption rare earth elements (REEs) ore collected at Jiangxi Province, China was investigated to identify the minerals abundant in REEs. The analyses of scanning electron microscopy (SEM)-energy dispersive spectrometry (EDS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for individual mineral particles of the weathered granite showed that kaolinitic particles formed by K-feldspar weathering contained large amounts of REEs. Scanning transmission electron microscopy (STEM)-EDS analyses revealed that the kaolinitic particles were mainly composed of kaolinite, illite and hematite. The elemental maps by Nano-SIMS for the kaolinitic particle clarified that La and Y are particularly concentrated in illite. The presence of illite presumably contributes to the formation of the REE accumulation zone in weathered granite. Furthermore, in the in-situ desorption experiment, nearly half the REEs (45.5%) remained in the kaolinitic particle after the treatment with 0.5 M ammonium sulfate solution. The desorption ratio of heavy REEs (HREEs: Gd–Lu) (60.4%) was lower than that of light REEs (LREEs: La–Eu) apart from Ce (69.0%). These results suggest that REEs form inner-sphere complexes on the kaolinitic particle. It can be assumed that the inner-sphere complexation suppresses the extraction ratio of REEs from the ores by ion-exchange treatment.

The analytical efficacy of five gas mixers and five stabilizers on signal stabilization and washout time obtained for laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was evaluated in the present study. In the case of gas mixers examined, a total of 95 patterns of their attitudes as well as different directions of the gas flows were examined, and it was found that the signal variation and the washout time were strongly dependent on these factors. Even in a simple Y-shaped fitting (Y-mixer), signal stability and washout time had large variations with respect to its different attitudes as well as gas flow directions. The shortest washout time for each gas mixer was almost the same ranging from 1.0 to 1.2 s. The signal variations observed were 11-15% of relative standard deviation (RSD) under optimum conditions for each gas mixer. The optimum condition of a Y-mixer for LA-ICPMS represented 11% RSD and 1.0 s for signal variation and washout time, respectively. In the case of stabilizers examined, almost all stabilizers improved signal variations from 11 to 3.0-9.3%, but washout times became longer than those of the only Y-mixer from 1.0 to 1.2-8.9 s. The important thing is that the signal stability and the washout time are trade-off correlations for gas mixers and stabilizers. A suitable gas mixer or a stabilizer on the trade-off line can be selected with respect to different applications. It was also observed that variations of both signal stability and washout time correlated with the volume of stabilizers despite their different inner structures; that is, a stable signal and longer washout time seemed to be observed when the volume of the chamber became larger. This suggested that the signal stabilization obtained by stabilizers was ascribable to not only elimination of larger particles from laser ablation but also particle mixing effect, which compensated signal variation.

Spherical radioactive caesium (Cs)-bearing microparticles (CsMPs) were emitted during the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March, 2011. The emission source (timing) and formation process of these particles remain unclear. In this study, the isotopic ratios of uranium (235U and 238U) and caesium (133Cs, 134Cs, 135Cs, and 137Cs) isotopes in the five spherical CsMPs (ca. 2 μm in size) sampled at 50 km west of the FDNPP were determined using secondary ion mass spectrometry and laser ablation-ICPMS, respectively. Results showed that the 235U/238U ratios of CsMPs were homogeneous (1.93 ± 0.03, N = 4) and close to those estimated for the fuel cores in units 2 and 3, and that the Cs isotopic ratios of CsMP were identical to those of units 2 and 3. These results indicated that U and Cs in the spherical CsMPs originated exclusively from the fuel melt in the reactors. Based on a thorough review of literatures related to the detailed atmospheric releases of radionuclides, the flow of plumes from the FDNPP reactor units during the accident and the U and Cs isotopic ratio results in this study, we hereby suggest that the spherical CsMPs originate only from the fuel in unit 2 on the night of 14 March to the morning of 15 March. The variation range of the analysed 235U/238U isotopic ratios for the four spherical particles was extremely narrow. Thus, U may have been homogenised in the source through the formation of fuel melt, which ultimately evaporating and taken into CsMPs in the reactor and was released from the unit 2.

The mass transfer of additive elements during the sintering of barium titanate (BaTiO3) ceramic was examined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in the present study. An analytical sample consisting of two pellets of BaTiO3 with different concentrations of additive elements of manganese (Mn) and holmium (Ho) as well as silicon (Si) as a sintering reagent was prepared and measured by LA-ICP-MS with small laser irradiated diameter of 10 μm to evaluate the distributions and concentrations of additive elements in order to examine their mass transfers. As results, enrichments of Mn and Si as an additive element and a sintering reagent, respectively, were observed on the adhesive surface between two BaTiO3 pellets, even though Ho did not show a similar phenomenon. The mass transfers of additive elements of Mn and Ho were also examined, and Mn seemed to show a larger mass transfer than that of Ho during the sintering process for BaTiO3 ceramics. The results obtained in this study shows the effectives of LA-ICP-MS for the future improvement of MLCCs.

This study analyzes the Thermoluminescence (TL) emissions for five emission bands, trace element concentrations and defects in quartz grains extracted from metamorphic rocks and quartz veins in the Sambagawa metamorphic belt, central Shikoku. An emission of 500 nm with 195, 245, and 320–325 °C glow peaks are observed through the lowest to highest grade samples. A 450 nm emission band with intense 195 and 245 °C glow peaks and a 320–325 °C shoulder peak is found in the higher grade samples. A 570 nm emission band with a 170 °C glow peak is observed in the samples derived from the lower grade zones. These characteristics of TL emissions of quartz suggest that they can be an indicator for the identification of rock derived from different metamorphic grades. The higher metamorphic grade samples with 450 nm emission bands in particular show higher intensities of the E1′ center. This relation indicates that the activation of the E1′ center in higher metamorphic conditions possibly contributed to the 450 nm emission band. Also, the 500 nm emission band is generally observed in the samples with the signal intensities of the Aluminum hole center, suggesting that the center is the source of this emission band. We also observed that the lower metamorphic grade samples contain lower signal intensities of the Aluminum hole center, despite higher aluminum concentrations. This inconsistency indicates that the formation of interstitial aluminum ions cause local lattice distortion regions, where self-trapped excitons can be formed and presumably provide the 570 nm emissions.

Apatite, which is used in the production of phosphorus fertilizers, contains small amounts of rare earth elements (REEs; 0.1–1%). Apatite deposits occur all over the world and thus have the potential to be a secure source of REEs. We investigated a method for recovery of REEs from an apatite sample; specifically, REEs were leached from the sample with an H2SO4 solution, the acid that is most commonly used for fertilizer production. At high H2SO4 concentrations, most of the REEs in the solution were lost to precipitation as insoluble gypsum (CaSO4·2H2O). However, at H2SO4 concentrations of

Geochemical characteristics and rare-earth element (REE)-bearing minerals of calc-alkaline granites in southern Myanmar were investigated to identify the minerals controlling fractionation between light and heavyREE(LREE and HREE) during magmatic differentiation and weathering. The granites were classified on the basis of the mineral assemblages into two contrasting groups: allanite-(Ce)- and/or titanite-bearing granites; and more HREE-enriched granites characterized by hydrothermal minerals including synchysite(Y), parisite-(Ce), bastnäsite-(Ce), xenotime-(Y), monazite-(Ce), Y-Ca silicate, waimirite-(Y) and fluorite. This suggests that allanite-(Ce) and titanite are not stable in differentiated magma and HREE are eventually preferentially incorporated into the hydrothermal minerals. The occurrence of theREE-bearing minerals is constrained by the degree of magmatic differentiation and the boundary of two contrasting granite groups is indicated by SiO2contents of ∼74 wt.% or Rb/Sr ratios of ∼3–8. Fractionation between LREE and HREE during weathering of the granites is influenced by weathering resistance of theREE-bearing minerals, i.e. allanite-(Ce), titanite, theREEfluorocarbonates and waimirite-(Y) are probably more susceptible to weathering, whereas zircon, monazite-(Ce) and xenotime-(Y) are resistant to weathering. Ion-exchangeableREEin weathered granites tend to be depleted in HREE relative to the whole-rock compositions, suggesting that HREE are more strongly adsorbed on weathering products or that HREE remain in residual minerals.

To explore the influence of radioactive heavy minerals on thorium (Th) and uranium (U) contamination in groundwater, we performed geochemical and mineralogical investigations of core samples (from ...

The Ediacaran and Cambrian periods were one of the most important periods for the evolution of life. The biodiversity drastically expanded in the period. However, the origins are still ambiguous because surface environmental changes through the time have not been well understood yet. We conducted in-situ analyses of the phosphorus contents of carbonate minerals with a laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) to estimate the phosphorus contents of seawater from the Ediacaran to the early Cambrian. Carbonate rocks contain not only the carbonate minerals but also detrital and authigenic materials such as silicate and phosphate minerals. Therefore, the whole rock compositions of carbonate rocks are not directly related with seawater composition. To avoid the influence of the involvement of the phosphate minerals, we performed the microscopic observation, elemental mapping of Si, Ca, Mg, Fe, and P contents with an electron probe microanalyzer (EPMA), and investigation of time profiles of signal intensities of Ca, Sr, Mn, P, La and Ba with the LA-ICP-MS. Especially, samples with low Mn/Sr ratios and primary textures such as oolites are suitable to estimate the primary phosphorus contents of the carbonates. The chemostratigraphy of the phosphorus contents of carbonates from the drill core and outcrop samples displays that the phosphorus contents decrease from ca. 400 ppm in the Ediacaran through ca. 200 ppm around the terminal Ediacaran and the beginning of the Cambrian to ca. 50 ppm in the early Cambrian. Previous works on 87Sr/86Sr chemostratigraphy from the Ediacaran to the Cambrian sections suggested relatively high continental influx in the middle Ediacaran, and around the Precambrian–Cambrian (PC/C) boundary. The high phosphorus content in the Ediacaran was possibly due to the high continental flux. On the other hand, previous works on chemostratigraphy of carbon isotope values of carbonate carbon from the Ediacaran to the Cambrian sections showed some large negative anomalies in the Ediacaran and around the Precambrian–Cambrian (PC/C) boundary, and suggested that the negative anomalies were caused by remineralization and respiration of dissolved organic matter. The degradation of the organic matter also accounts for the high phosphorus contents in the Ediacaran. The high phosphorus content of seawater favors enhancement of primary productivity and formation of phosphorites. The high phosphorus contents in the seawater possibly led to the emergence of the large, and motile organism through the enhancement of primary productivity and the consequent increase of oxygen content of the seawater.

We have conducted geochemical and mineralogical investigations of the rare earth and yttrium (REY)-rich mud from the Minami-Torishima area in the Pacific in order to clarify the concentration of REY and their host-phase in the mud. X-ray diffraction analysis shows that the mud is mainly composed of phillipsite, fluorapatite, quartz, albite, illite and montmorillonite. Whole-rock CaO, P2O5 and total REY contents of the mud are positively correlated. Relative abundance of apatite is also positively correlated to P2O5 and total REY contents. These correlations suggest that apatite is the main host of the P2O5 and REY in the mud. We make in situ compositional analyses of constituent minerals in the REY mud. The results show that the apatite is abundant in REY (9300–32,000 ppm) and is characterized by a negative Ce anomaly and enrichment in heavy rare-earth elements. This abundance and composition of REY of the mud is similar those of fish debris apatites. In contrast, phillipsite is less abundant in REY (60–170 ppm). Therefore we conclude that the main REY host phase of the mud is apatite.

Zircon (ZrSiO4) from Naegi and Ohro granitic pegmatites, Japan and from Saigon alkali basalt, Vietnam, were mineralogically characterized by inductively couples plasma mass spectrometry (ICP-MS), electron-microprobe analysis (EMPA), X-ray powder diffraction, micro-Raman spectroscopy and leaching experiment. The powder XRD and Raman spectra analyses show that the degree of metamictization increases in the following order: Saigon (crystalline), Ohro (partly metamict) and Naegi zircons (fully metamict). Quantitative analytical results by the EMPA indicate that the Naegi and Ohro zircon samples contain a large amount of REE2O3, while REE2O3 contents in Saigon zircon are below detection limit. The leaching experiments using a solvent 1 M-HCl for the present zircons under the condition at a room temperature to 250 °C and retention time of 30 h resulted in about 100%, 50% and 1% recoveries of REE from the Naegi, Ohro and Saigon zircons, respectively. Leaching experiments for the Naegi zircon at different temperatures and retention time 30 h, showed that a significant amount of REE was leached out at the temperature above 150 °C, although REE were hard to be leached at a room temperature (about 25 °C). Therefore, both low crystallinity of zircon and higher leaching temperature are requisite for effective leaching of REE from zircon.

We have developed a new calibration technique for multielement determination and U-Pb dating of zircon samples using laser ablation-inductively coupled plasma mass spectrometry (ICPMS) coupled with galvanometric optics. With the galvanometric optics, laser ablation of two or more sample materials could be achieved in very short time intervals (~10 ms). The resulting sample aerosols released from different ablation pits or different solid samples were mixed and homogenized within the sample cell and then transported into the ICP ion source. Multiple spot laser ablation enables spiking of analytes or internal standard elements directly into the solid samples, and therefore the standard addition calibration method can be applied for the determination of trace elements in solid samples. In this study, we have measured the rare earth element (REE) abundances of two zircon samples (Nancy 91500 and Prešovice) based on the standard addition technique, using a direct spiking of analytes through a multispot laser ablation of the glass standard material (NIST SRM612). The resulting REE abundance data show good agreement with previously reported values within analytical uncertainties achieved in this study (10% for most elements). Our experiments demonstrated that nonspectroscopic interferences on 14 REEs could be significantly reduced by the standard addition technique employed here. Another advantage of galvanometric devices is the accumulation of sample aerosol released from multiple spots. In this study we have measured the U-Pb age of a zircon sample (LMR) using an accumulation of sample aerosols released from 10 separate ablation pits of low diameters (~8 μm). The resulting (238)U-(206)Pb age data for the LMR zircons was 369 ± 64 Ma, which is in good agreement with previously reported age data (367.6 ± 1.5 Ma). (1) The data obtained here clearly demonstrate that the multiple spot laser ablation-ICPMS technique can become a powerful approach for elemental and isotopic ratio measurements in solid materials.

The redox state of Precambrian shallow seas has been linked with material cycle and evolution of the photosynthesis-based ecosystem. Iron is a redox-sensitive element and exists as a soluble Fe(II) species or insoluble Fe(III) species on Earth’s surface. Previous studies have shown that the iron isotopic ratio of marine sedimentary minerals is useful for understanding the ocean redox state, although the redox state of the Archean shallow sea is poorly known. This is partly because the conventional bulk isotope analytical technique has often been used, wherein the iron isotopic record may be dampened by the presence of isotopically different iron-bearing minerals within the same sample. Here we report a microscale iron isotopic ratio of individual pyrite grains in shallow marine stromatolitic carbonates over geological time using a newly developed, near-infrared femtosecond laser ablation multicollector ICP-MS technique (NIR-fs-LA-MC-ICP-MS). We have determined that the grain-scale iron isotopic distribution of pyrite from coeval samples shows a bimodal (2.7 and 2.3 Ga) or unimodal pattern (2.9, 2.6, and 0.7 Ga). In particular, pyrite from the 2.7 Ga Fortescue Group shows a unique bimodal distribution with highly positive (+1.0‰ defined as Type 1) and negative δ56Fe values (−1.8‰ defined as Type 2). Type 1 and 2 pyrites occasionally occur within different siliceous layers in the same rock specimen. Layer-scale iron isotopic heterogeneity indicates that the iron isotopic ratios of the two types of pyrite are not homogenized by diagenesis after deposition. Some cubic pyrites have a core with a positive δ56Fe value (1‰) and a rim with a crustal δ56Fe value (0‰). The observed isotopic zoning suggests that the positive δ56Fe value is a primary signature at the time of stromatolite formation, while secondary pyrite precipitated during diagenesis. The positive δ56Fe value of Type 1 and the large iron isotopic difference between Type 1 and 2 (2.8‰.) suggest partial Fe(II) oxidation in the 2.7-Ga shallow sea, i.e., pyritization of 56Fe-enriched ferric oxyhydroxide (Type 1) and 56Fe depleted Fe2+aq in seawater (Type 2). Type 2 pyrite was probably not produced by microbial iron redox cycling during diagenesis because this scenario requires a higher abundance of pyrite with δ56Fe of 0‰ than of −1.8‰. Consequently, the degree of Fe(II) oxidation in the 2.7-Ga shallow sea can be estimated by a Fe2+aq steady-state model. The model calculation shows that half the Fe2+aq influx was oxidized in the seawater. This implies that O2 produced by photosynthesis would have been completely consumed by oxidation of the Fe2+aq influx. Grain-scale iron isotopic distribution of pyrite could be a useful index for reconstructing the redox state of the Archean shallow sea.

A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of (57)Fe, obtained from iron sulfide (FeS(2)), demonstrated that the resulting signal intensity of (57)Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm(2)). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the (206)Pb/(238)U (f(Pb/U)) and (238)U/(232)Th (f(U/Th)) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of (56)Fe and the isotopic ratios ((57)Fe/(54)Fe and (56)Fe/(54)Fe) have been measured on a natural pyrite (FeS(2)) sample. Repeatability in signal intensity of (56)Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in (57)Fe/(54)Fe and (56)Fe/(54)Fe ratio measurements could be improved by the fs-laser ablation system. The data obtained here clearly demonstrate that, even with the fundamental wavelength (NIR operating at 780 nm), the fs-laser ablation system has the potential to become a significant tool for in-situ elemental and isotopic analysis of geochemical samples including heavy minerals and metallic materials.

Laser ablation in liquid (LAL) is widely used for the micro fabrications or production of nano-particles of various materials. In this study, we have evaluated the analytical capability of the LAL as a new sampling technique for elemental and isotopic analysis of solid samples. The solid sample was set into the deionized water, and the laser ablation was carried out within the water using a Ti:S femtosecond laser operating at fundamental wavelength (780 nm). The laser-induced sample particles were directly trapped and collected in the ambient water with high efficiency. We have investigated the possible elemental and isotopic fractionation during the LAL sampling. Five isotopic ratios (208Pb/238U, 238U/232Th, 208Pb/206Pb, 56Fe/54Fe and 57Fe/54Fe) were measured on the resulting sample particles obtained with various ablation conditions (fluence and repetition rate) using ICP-mass spectrometry (ICP-MS). Series of experiments revealed that either with the higher fluence (>200 J cm−2) or with higher repetition rate (>250 Hz), the resulting 208Pb/238U ratios varied significantly (>1%) from those obtained with source materials (hence, NIST SRM 610). For the 238U/232Th, 208Pb/206Pb, 56Fe/54Fe and 57Fe/54Fe ratios, the measured values did not vary measurably (