首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 25 毫秒
1.
Matrix‐matched reference materials are necessary for accurate microbeam U‐Pb dating and Hf isotopic determination. This study introduces the RMJG rutile as a new potential reference material, which was separated from Palaeoproterozoic pelitic granulites collected in Hebei Province, China. LA‐ICP‐MS measurements indicate the RMJG rutile has extremely low Th (< 0.003 ± 0.01 µg g?1) and common Pb contents, but high Hf (102 ± 34 µg g?1), U (61 ± 11 µg g?1), and radiogenic Pb (~ 20 µg g?1) contents. Moreover, the rutile yields relatively constant U‐Pb ages and Hf isotopic data. The LA‐ICP‐MS analyses suggest that this rutile has a concordant U‐Pb age with a statistical mean 206Pb/238U and 207Pb/235U ages of 1749.9 ± 32.1 Ma and 1750.0 ± 26.4 Ma, respectively (2s), which are statistically indistinguishable from its ID‐TIMS ages (1750.6 ± 8.4 and 1750.1 ± 4.7 Ma). Precise determination of the 176Hf/177Hf ratio by MC‐ICP‐MS in solution mode (0.281652 ± 0.000006) is in good agreement with the statistical mean of the LA‐MC‐ICP‐MS measurements (0.28166 ± 0.00018). Therefore, the limited variations of RMJG U‐Pb age and Hf isotopic composition together with its extremely low common Pb and high Hf, U and Pb contents make it an ideal calibration and monitor reference material for LA‐ICP‐MS measurements.  相似文献   

2.
We present multitechnique U‐Pb geochronology and Hf isotopic data from zircon separated from rapakivi biotite granite within the Eocene Golden Horn batholith in Washington, USA. A weighted mean of twenty‐five Th‐corrected 206Pb/238U zircon dates produced at two independent laboratories using chemical abrasion‐isotope dilution‐thermal ionisation mass spectrometry (CA‐ID‐TIMS) is 48.106 ± 0.023 Ma (2s analytical including tracer uncertainties, MSWD = 1.53) and is our recommended date for GHR1 zircon. Microbeam 206Pb/238U dates from laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS) laboratories are reproducible and in agreement with the CA‐ID‐TIMS date to within < 1.5%. Solution multi‐collector ICP‐MS (MC‐ICP‐MS) measurements of Hf isotopes from chemically purified aliquots of GHR1 yield a mean 176Hf/177Hf of 0.283050 ± 17 (2s, n = 10), corresponding to a εHf0 of +9.3. Hafnium isotopic measurements from two LA‐ICP‐MS laboratories are in agreement with the solution MC‐ICP‐MS value. The reproducibility of 206Pb/238U and 176Hf/177Hf ratios from GHR1 zircon across a variety of measurement techniques demonstrates their homogeneity in most grains. Additionally, the effectively limitless reserves of GHR1 material from an accessible exposure suggest that GHR1 can provide a useful reference material for U‐Pb geochronology of Cenozoic zircon and Hf isotopic measurements of zircon with radiogenic 176Hf/177Hf.  相似文献   

3.
A new natural zircon reference material SA01 is introduced for U‐Pb geochronology as well as O and Hf isotope geochemistry by microbeam techniques. The zircon megacryst is homogeneous with respect to U‐Pb, O and Hf isotopes based on a large number of measurements by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS). Chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA‐ID‐TIMS) U‐Pb isotopic analyses produced a mean 206Pb/238U age of 535.08 ± 0.32 Ma (2s, n = 10). Results of SIMS and LA‐ICP‐MS analyses on individual shards are consistent with the TIMS ages within uncertainty. The δ18O value determined by laser fluorination is 6.16 ± 0.26‰ (2s, n = 14), and the mean 176Hf/177Hf ratio determined by solution MC‐ICP‐MS is 0.282293 ± 0.000007 (2s, n = 30), which are in good agreement with the statistical mean of microbeam analyses. The megacryst is characterised by significant localised variations in Th/U ratio (0.328–4.269) and Li isotopic ratio (?5.5 to +7.9‰); the latter makes it unsuitable as a lithium isotope reference material.  相似文献   

4.
A potential zircon reference material (BB zircon) for laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U‐Pb geochronology and Hf isotope geochemistry is described. A batch of twenty zircon megacrysts (0.5–1.5 cm3) from Sri Lanka was studied. Within‐grain rare earth element (REE) compositions are largely homogeneous, albeit with some variation seen between fractured and homogeneous domains. Excluding fractured cathodoluminescence bright domains, the variation in U content for all analysed crystals ranged from 227 to 368 μg g?1 and the average Th/U ratios were between 0.20 and 0.47. The Hf isotope composition (0.56–0.84 g/100 g Hf) is homogeneous within and between the grains – mean 176Hf/177Hf of 0.281674 ± 0.000018 (2s). The calculated alpha dose of 0.59 × 1018 g?1 for a number of BB grains falls within the trend of previously studied, untreated zircon samples from Sri Lanka. Aliquots of the same crystal (analysed by ID‐TIMS in four different laboratories) gave consistent U‐Pb ages with excellent measurement reproducibility (0.1–0.4% RSD). Interlaboratory assessment (by LA‐ICP‐MS) from individual crystals returned results that are within uncertainty equivalent to the TIMS ages. Finally, we report on within‐ and between‐grain homogeneity of the oxygen isotope systematic of four BB crystals (13.16‰ VSMOW).  相似文献   

5.
We report homogeneity tests on large natural apatite crystals to evaluate their potential as U reference materials for apatite fission‐track (AFT) thermochronology by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The homogeneity tests include the measurements of major element concentrations by electron probe microanalysis (EPMA), whereas for U concentration, isotope dilution (ID) ICP‐MS and laser ablation (LA) ICP‐MS were employed. Two apatite crystals are potential reference materials for LA‐ICP‐MS analysis: a 1 cm3 fraction of a Durango crystal (7.5 μg g?1 U) and a 1 cm3 Mud Tank crystal (6.9 μg g?1 U). The relative standard deviation (1 RSD) of the U concentration determined by ID‐ICP‐MS of both apatite crystals was ≤ 1.5%, whereas 1 RSD for the LA‐ICP‐MS results was better than 4%, providing sufficient homogeneity for fission‐track dating. The results on the U homogeneity for two different apatite samples are an important step towards establishing in situ dating routines for AFT analysis by LA‐ICP‐MS.  相似文献   

6.
In both nature and synthetic experiments, the common iron oxide haematite (α‐Fe2O3) can incorporate significant amounts of U into its crystal structure and retain radiogenic Pb over geological time. Haematite is a ubiquitous component of many ore deposit types and, therefore, represents a valuable hydrothermal mineral geochronometer, allowing direct constraints to be placed on the timing of ore formation and upgrading. However, to date, no suitable natural haematite reference material has been identified. Here, a synthetic haematite U‐Pb reference material (MR‐HFO) is characterised using LA‐ICP‐MS and ID‐TIMS. Centimetre‐scale ‘chips’ of synthesised α‐Fe2O3 were randomly microsampled via laser ablation‐extraction and analysed using ID‐TIMS. Reproducible U/Pb and Pb/Pb measurements were obtained across four separate chips (n = 13). Subsequently, an evaluation of the suitability MR‐HFO in constraining U‐Pb data via LA‐ICP‐MS is presented using a selection of natural samples ranging from Cenozoic to Proterozoic in age. The MR‐HFO normalised U‐Pb ratios are more concordant and ages more accurate versus the same LA‐ICP‐MS spot analyses normalised to zircon reference material, when compared with independently acquired ID‐TIMS data from the same natural haematite grains. Results establish MR‐HFO as a suitable reference material for LA‐ICP‐MS haematite U‐Pb geochronology.  相似文献   

7.
LA‐ICP‐MS U–Pb detrital zircon studies typically analyse 50–200 grains per sample, with the consequent risk that minor but geologically important age components (e.g., the youngest detrital zircon population) are not detected, and higher abundance age components are misrepresented, rendering quantitative comparisons between samples impossible. This study undertook rapid U–Pb LA‐ICP‐MS analyses (8 s per 18–47 μm diameter spot including baseline and ablation) of zircon, apatite, rutile and titanite using an aerosol rapid introduction system (ARIS). As the ARIS resolves individual single pulses at fast sampling rates, spot analyses require a high repetition rate (> 50 Hz) so the signal does not return to baseline and mass sweep times (> 80 ms) that span several laser pulses (i.e., major undersampling of the signal). All rapid U–Pb spot analyses employed 250–300 pulses, repetition rates of 53–65 Hz (total ablation times of 4.1–5.7 s) and low fluence (1.75–2.5 J cm?2), resulting in pit depths of ca. 15 μm. Zircon, apatite, rutile and titanite reference material data yield an accuracy and precision (2s) of < 1% for pre‐Cenozoic reference materials and < 2% for younger reference materials. We present a detrital zircon data set from a Neoproterozoic tillite where > 1000 grains were analysed in < 3 h with a precision and accuracy comparable to conventional LA‐ICP‐MS analytical protocols, demonstrating the rapid acquisition of huge detrital data sets.  相似文献   

8.
Zircon crystals in the age range of ca. 10–300 ka can be dated by 230Th/238U (U‐Th) disequilibrium methods because of the strong fractionation between Th and U during crystallisation of zircon from melts. Laser ablation inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) analysis of nine commonly used reference zircons (at secular equilibrium) and a synthetic zircon indicates that corrections for abundance sensitivity and dizirconium trioxide molecular ions (Zr2O3+) are critical for reliable determination of 230Th abundances in zircon. When corrected for abundance sensitivity and interferences, mean activity ratios of (230Th)/(238U) for nine reference zircons analysed on five different days averaged 0.995 ± 0.023 (95% confidence weighted by data‐point uncertainty only, MSWD = 1.6; n = 9), consistent with their U‐Pb ages > 4 Ma that imply equilibrium for all intermediate daughter isotopes (including 230Th) within the 238U decay chain. U‐Th zircon ages generated by LA‐ICP‐MS without mitigating (e.g., by high mass resolution) or correcting for abundance sensitivity and molecular interferences on 230Th are potentially unreliable. To validate the applicability of LA‐ICP‐MS to this dating method, we acquired data from three late Quaternary volcanic units: the 41 ka Campanian Ignimbrite (plutonic clasts), the 161 ka Kos Plateau Tuff (juvenile clasts) and the 12 ka Puy de Dôme trachyte lava (all eruption ages by Ar/Ar, with zircon U‐Th ages being of equal or slightly older). A comparison of the corrected LA‐ICP‐MS results with previously published secondary ion mass spectrometry (SIMS) data for these rocks shows comparable ages with equivalent precision for LA‐ICP‐MS and SIMS, but much shorter analysis durations (~ 2 min vs. ~ 15 min) per spot with LA‐ICP‐MS and much simpler sample preparation. Previously undated zircons from the Yali eruption (Kos‐Nisyros volcanic centre, Greece) were analysed using this method. This yielded a large age spread (~ 45 to > 300 ka), suggesting significant antecryst recycling. The youngest zircon age (~ 45 ± 10 ka) provides a reasonable maximum estimate for the eruption age, in agreement with the previously published age using oxygen isotope stratigraphy (~ 31 ka).  相似文献   

9.
Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was examined as a tool for measuring isotopic variation as a function of ablation depth in unpolished zircon from an Archaean metasediment specimen. This technique was able to identify micrometre‐thin (> 3 μm) isotopically distinct mineral domains characterised by ca. 100 Myr younger 207Pb/206Pb ages associated with 2s age uncertainties as low ~ 0.2%, as well as elevated U content relative to grain interiors (up to an order of magnitude). Our calculated drilling rate suggests that each laser pulse excavated depths of ~ 0.06 μm. Ages resolved through the LA‐ICP‐MS methods overlap the 2s uncertainties of 207Pb/206Pb ages measured using SIMS depth profiling on the same zircon population. The rims were further evinced by the detection of relative enrichment (> 3 orders of magnitude) in REE in the outermost micrometres of the same zircon, measured using a different and independent LA‐ICP‐MS depth profiling technique. We propose a LA‐ICP‐MS U–Pb technique capable of quickly identifying and quantifying rims, which are indication of late, yet geologically significant, fluid events that are otherwise undefined.  相似文献   

10.
A new natural rutile reference material is presented, suitable for U‐Pb dating and Zr‐in‐rutile thermometry by microbeam methods. U‐Pb dating of rutile R632 using laser ablation ICP‐MS with both magnetic sector field and quadrupole instruments as well as isotope dilution‐thermal ionisation mass spectrometry yielded a concordia age of 496 ± 2 Ma. The high U content (> 300 μg g?1) enabled measurement of high‐precision U‐Pb ages despite its young age. The sample was found to have a Zr content of 4294 ± 196 μg g?1, which makes it an excellent complementary reference material for Zr‐in‐rutile thermometry. Individual rutile grains have homogeneous compositions of a number of other trace elements including V, Cr, Fe, Nb, Mo, Sn, Sb, Hf, Ta and W. This newly characterised material significantly expands the range of available rutile reference materials relevant for age and temperature determinations.  相似文献   

11.
Most monazite reference materials (RMs) for in situ U‐Pb geochronology are rich in Th; however, many hydrothermal ore deposits contain monazite that is low in trace element contents, including Th, U and Pb. Because of potential problems with matrix effects and the lack of appropriate matrix‐matched RMs, such variations can bias dating of hydrothermal deposits. In this paper, we describe a polycrystalline low‐U and low‐Th Diamantina monazite from the Espinhaço Range, SE Brazil. It has a U‐Pb ID‐TIMS weighted mean 207Pb*/235U ratio of 0.62913 ± 0.00079, 206Pb*/238U of 0.079861 ± 0.000088 and 207Pb*/206Pb* of 0.057130 ± 0.000031, yielding a weighted mean 206Pb*/238U date of 495.26 ± 0.54 Ma (95% c.l.). In situ dates acquired with different methods (LA‐(Q, SF, MC)‐ICP‐MS and SIMS) are within uncertainty of the ID‐TIMS data. U‐Pb LA‐(Q, MC)‐ICP‐MS runs, using Diamantina as a primary RM, reproduced the ages of other established RMs within < 1% deviation. The LA‐MC‐ICP‐MS analyses yielded homogeneous Sm‐Nd isotopic compositions (143Nd/144Nd = 0.511427 ± 23, 2s; 147Sm/144Nd = 0.1177 ± 13, 2s) and εNd(495 Ma) of ?18.7 ± 0.5 (2s). SIMS oxygen isotope determinations showed measurement reproducibility better than ± 0.3‰ (2s), confirming Diamantina's relative homogeneity at test portion masses below 1 ng.  相似文献   

12.
Three synthetic reference glasses were prepared by directly fusing and stirring 3.8 kg of high‐purity oxide powders to provide reference materials for microanalytical work. These glasses have andesitic major compositions and are doped with fifty‐four trace elements in nearly identical abundance (500, 50, 5 µg g?1) using oxide powders or element solutions, and are named ARM‐1, 2 and 3, respectively. We further document that sector‐field (SF) ICP‐MS (Element 2 or Element XR) is capable of sweeping seventy‐seven isotopes (from 7Li to 238U, a total of sixty‐eight elements) in 1 s and, thus, is able to quantify up to sixty‐eight elements by laser sampling. Micro‐ and bulk analyses indicate that the glasses are homogeneous with respect to major and trace elements. This paper provides preliminary data for the ARM glasses using a variety of analytical techniques (EPMA, XRF, ICP‐OES, ICP‐MS, LA‐Q‐ICP‐MS and LA‐SF‐ICP‐MS) performed in ten laboratories. Discrepancies in the data of V, Cr, Ni and Tl exist, mainly caused by analytical limitations. Preliminary reference and information values for fifty‐six elements were calculated with uncertainties [2 relative standard error (RSE)] estimated in the range of 1–20%.  相似文献   

13.
We describe an in situ method for simultaneous measurement of U–Pb–Hf isotopes and trace element compositions of zircons using a quadrupole and multiple-collector inductively-coupled-plasma mass spectrometer (Q-ICP-MS and MC-ICP-MS, respectively) connected to a single excimer laser-ablation system. A laser-generated zircon aerosol was split behind the ablation cell into two transport tubes via a Y-shaped connector and simultaneously introduced into the two mass spectrometers. Hafnium isotopes were measured on the MC-ICP-MS instrument, while U–Pb ages and trace element compositions were determined using the Q-ICP-MS. The precision and accuracy of this method was evaluated using six well-known and widely used zircon standards (91500, Temora-2, GJ-1, Mud Tank, BR266 and Monastery). Analyses were carried out using spot sizes of 32, 44 and 60 μm. For the 44 and 60 μm spot, the resulting U–Pb ages, Hf isotopic and rare earth element (REE) compositions of these six zircons agree with recommended/reported values within 2σ error. The difference in relative standard deviations (RSD) of 206Pb/238U ages between split-flow measurements and those obtained separately on the Q-ICP-MS is within ～ 20% for 91500, Temora-2 and GJ-1, and ～ 60% for Mud Tank (due to its lower U and Pb concentrations). Our method provides a precise approach for determining the U–Pb age and the Hf isotopic and trace element compositions of zircon within a single ablation event. This is in particular important for analysis of zircons that are small or contain complicated zoning patterns. Finally, the REE composition of zircon BR266 is more homogeneous than other zircons and could be a suitable standard by which to benchmark new standards for microprobe analyses of zircons.  相似文献   

14.
Sphalerite (ZnS) is an abundant ore mineral and an important carrier of elements such as Ge, Ga and In used in high‐technology applications. In situ measurements of trace elements in natural sphalerite samples using LA‐ICP‐MS are hampered by a lack of homogenous matrix‐matched sulfide reference materials available for calibration. The preparation of the MUL‐ZnS1 calibration material containing the trace elements V, Cr, Mn, Co, Ni, Cu, Ga, Ge, As, Se, Mo, Ag, Cd, In, Sn, Sb, Tl and Pb besides Zn, Fe and S is reported. Commercially available ZnS, FeS, CdS products were used as the major components, whereas the trace elements were added by doping with single‐element ICP‐MS standard solutions and natural mineral powders. The resulting powder mixture was pressed to pellets and sintered at 400 °C for 100 h using argon as an inert gas. To confirm the homogeneity of major and trace element distributions within the MUL‐ZnS1 calibration material, measurements were performed using EPMA, solution ICP‐MS, ICP‐OES and LA‐ICP‐MS. The results show that MUL‐ZnS‐1 is an appropriate material for calibrating trace element determination in sphalerite using LA‐ICP‐MS.  相似文献   

15.
The Lamont‐Doherty Earth Observatory radiogenic isotope group has been systematically measuring Sr‐Nd‐Pb‐Hf isotopes of USGS reference material BCR‐2 (Columbia River Basalt 2), as a chemical processing and instrumental quality control monitor for isotopic measurements. BCR‐2 is now a widely used geochemical inter‐laboratory reference material (RM), with its predecessor BCR‐1 no longer available. Recognising that precise and accurate data on RMs is important for ensuring analytical quality and for comparing data between different laboratories, we present a compilation of multiple digestions and analyses made on BCR‐2 during the first author's dissertation research. The best estimates of Sr, Nd and Hf isotope ratios and measurement reproducibilities, after filtering at the 2s level for outliers, were 87Sr/86Sr = 0.705000 ± 11 (2s, 16 ppm, n = 21, sixteen digestions, one outlier), 143Nd/144Nd = 0.512637 ± 13 (2s, 25 ppm, n = 27, thirteen digestions, one outlier) and 176Hf/177Hf = 0.282866 ± 11 (2s, 39 ppm, n = 25, thirteen digestions, no outliers). Mean Nd and Hf values were within error of those reported by Weis et al. (2006, 2007) in their studies of RMs; mean Sr values were just outside the 2s uncertainty range of both laboratories. Moreover, a survey of published Sr‐Nd‐Hf data shows that our results fall within the range of reported values, but with a smaller variability. Our Pb isotope results on acid leached BCR‐2 aliquots (n = 26, twelve digestions, two outliers) were 206Pb/204Pb = 18.8029 ± 10 (2s, 55 ppm), 207Pb/204Pb = 15.6239 ± 8 (2s, 52 ppm), 208Pb/204Pb = 38.8287 ± 25 (2s, 63 ppm). We confirm that unleached BCR‐2 powder is contaminated with Pb, and that sufficient leaching prior to digestion is required to achieve accurate values for the uncontaminated Pb isotopic compositions.  相似文献   

16.
A measurement procedure for the rapid acquisition of U‐Pb dates for detrital zircons by quadrupole LA‐ICP‐MS was developed. The procedure achieves a threefold increase in measurement efficiency compared with the most commonly used methods. Utilising reduced background counting times and a shortened ablation period, a throughput of ~ 130 measurements/h can be achieved. The measurement procedure was characterised and validated using data from thirty‐nine sessions acquired over a twelve‐month period. Systematic measurement error in 206Pb/238U dates for reference materials used for quality control with ages between 28.2 and 2672 Ma was < 1.5%. Average measurement uncertainty, including both random and systematic components, was 1–4% (2s). Interrogation of time‐resolved calculated dates and signal intensities for each measurement allows for the detection and elimination of portions of measurements exhibiting age heterogeneities, zoning, lead loss and contamination by common lead. The measurement procedure diminishes the need to acquire cathodoluminescence imagery for routine detrital zircon applications further increasing throughput and reducing cost. The utility of the measurement procedure is demonstrated by the measurement of samples previously characterised by LA‐MC‐ICP‐MS.  相似文献   

17.
Apatite incorporates variable and significant amounts of halogens (mainly F and Cl) in its crystal structure, which can be used to determine the initial F and Cl concentrations of magmas. The amount of chlorine in the apatite lattice also exerts an important compositional control on the degree of fission‐track annealing. Chlorine measurements in apatite have conventionally required electron probe microanalysis (EPMA). Laser ablation inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) is increasingly used in apatite fission‐track dating to determine U concentrations and also in simultaneous U‐Pb dating and trace element measurements of apatite. Apatite Cl measurements by ICP‐MS would remove the need for EPMA but the high (12.97 eV) first ionisation potential makes analysis challenging. Apatite Cl data were acquired using two analytical set‐ups: a Resonetics M‐50 193 nm ArF Excimer laser coupled to an Agilent 7700× quadrupole ICP‐MS (using a 26 μm spot with an 8 Hz repetition rate) and a Photon Machines Analyte Excite 193 nm ArF Excimer laser coupled to a Thermo Scientific iCAP Qc (using a 30 μm spot with a 4 Hz repetition rate). Chlorine concentrations were determined by LA‐ICP‐MS (1140 analyses in total) for nineteen apatite occurrences, and there is a comprehensive EPMA Cl and F data set for 13 of the apatite samples. The apatite sample suite includes different compositions representative of the range likely to be encountered in natural apatites, along with extreme variants including two end‐member chlorapatites. Between twenty‐six and thirty‐nine isotopes were determined in each apatite sample corresponding to a typical analytical protocol for integrated apatite fission track (U and Cl contents) and U‐Pb dating, along with REE and trace element measurements. 35Cl backgrounds (present mainly in the argon gas) were ~ 45–65 kcps in the first set‐up and ~ 4 kcps in the second set‐up. 35Cl background‐corrected signals ranged from ~ 0 cps in end‐member fluorapatite to up to ~ 90 kcps in end‐member chlorapatite. Use of a collision cell in both analytical set‐ups decreased the low mass sensitivity by approximately an order of magnitude without improving the 35Cl signal‐to‐background ratio. A minor Ca isotope was used as the internal standard to correct for drift in instrument sensitivity and variations in ablation volume during sessions. The 35Cl/43Ca values for each apatite (10–20 analyses each) when plotted against the EPMA Cl concentrations yield excellently constrained calibration relationships, demonstrating the suitability of the analytical protocol and that routine apatite Cl measurements by ICP‐MS are achievable.  相似文献   

18.
There is currently a lack of well‐characterised matrix‐matched reference materials (RMs) for forensic analysis of U‐rich materials at high spatial resolution. This study reports a detailed characterisation of uraninite (nominally UO2+x) from the Happy Jack Mine (UT, USA). The Happy Jack uraninite can be used as a RM for the determination of rare earth element (REE) mass fractions in nuclear materials, which provide critical information for source attribution purposes. This investigation includes powder X‐ray diffraction (pXRD) data, as well as major, minor and trace element abundances determined using a variety of micro‐analytical techniques. The chemical signature of the uraninite was investigated at the macro (cm)‐scale with micro‐X‐ray fluorescence (µXRF) mapping and at high spatial resolution (tens of micrometre scale) using electron probe microanalysis (EPMA) and laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) analyses. Based on EPMA results, the uraninite is characterised by homogeneous UO2 and CaO contents of 91.57 ± 1.49% m/m (2s uncertainty) and 2.70 ± 0.38% m/m (2s), respectively. Therefore, CaO abundances were used as the internal standard when conducting LA‐ICP‐MS analyses. Overall, the major element and REE compositions are homogeneous at both the centimetre and micrometre scales, allowing this material to be used as a RM for high spatial resolution analysis of U‐rich samples.  相似文献   

19.
Chalcopyrite is an important sulfide mineral in many types of ore deposits, but matrix‐matched chalcopyrite reference materials for microanalysis are lacking. A new natural chalcopyrite‐bearing specimen (HTS4‐6) was analysed in this study to investigate its potential as a reference material for microbeam sulfur isotope ratio measurement. Detailed textural examination and major element determination showed that the HTS4‐6 chalcopyrite grains have no growth rim or zoning. A total of 607 sulfur isotope ratio spot measurements with secondary ion mass spectrometry (SIMS) conducted on the cruciform sections, and over 120 randomly selected grains yielded highly consistent sulfur isotope ratio. The intermediate measurement precision for four measurement sessions of the 34S/32S measurement results was better than 0.39‰ (2s). Randomly selected chalcopyrite grains of HTS4‐6 were further analysed by LA‐MC‐ICP‐MS, which gave a mean δ34S value of +0.58 ± 0.38‰ (2s, n = 95). The maximum variance (expressed as intermediate precision from SIMS and LA‐MC‐ICP‐MS measurements) is not worse than 0.39‰ (the SIMS value), indicating that HTS4‐6 chalcopyrite is a potential reference material for in situ microbeam sulfur isotope measurements. The mean δ34S value determined by gas source isotope ratio mass spectrometry (GS‐IRMS) is +0.63 ± 0.16‰ (2s, n = 23), consistent with that derived by LA‐MC‐ICP‐MS, and can represent the recommended value for this potential reference material.  相似文献   

20.
A combined geochronological and geochemical investigation for the same domain of zircon provides valuable information on timing and genesis, particularly in the case of multi‐growth metamorphic zircon. A high spatial resolution concurrent analytical method for zircon U‐Pb age and rare earth element content was successfully achieved in this study, using a multi‐collector secondary ion mass spectrometer (SIMS) at a ~ 8 μm diameter scale. Special instrument parameters were employed, including a high mass resolution of approximately 15000 applied to replace the previous energy filter method, and a dynamic multi‐collector mode used to reduce the measurement time to 18 min per analysis. Six zircon reference materials yielded precise and accurate 206Pb/238U ages, which are comparable to those obtained by the ordinary mono‐collector method, but with 2–3 times higher spatial resolution. All zircon grains measured in this study showed enriched heavy‐REE (HREE) contents consistent with previously reported values determined by LA and solution ICP‐MS methods. The light‐REE (LREE) mass fractions measured using both SIMS and LA‐ICP‐MS methods in this study, although with quite different volume, show consistent results within uncertainties.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号