A Flux‐Free Fusion Technique for Rapid Determination of Major and Trace Elements in Silicate Rocks by LA‐ICP‐MS

A simple flux‐free fusion technique was developed to analyse major and trace element compositions of silicate rocks. The sample powders were melted in a molybdenum capsule sealed in a graphite tube to make a homogenous glass in a temperature‐controlled one‐atmosphere furnace. The glass was then measured for both major and trace element concentrations by LA‐ICP‐MS using a calibration strategy of total metal‐oxide normalisation. The optimum conditions (i.e., temperature and duration) to make homogeneous glasses were obtained by performing melting experiments using a series of USGS reference materials including BCR‐2, BIR‐1, BHVO‐2, AGV‐1, AGV‐2, RGM‐1, W‐2 and GSP‐2 with SiO₂ contents from 47 to 73% m/m. Analytical results of the USGS reference materials using our method were generally consistent with the recommended values within a discrepancy of 5–10% for most elements. The routine precision of our method was generally better than 5–10% RSD. Compared with previous methods of LA‐ICP‐MS whole‐rock analyses, our flux‐free fusion method is convenient and efficient in making silicate powder into homogeneous glass. Furthermore, it limits contamination and loss of volatile elements during heating. Therefore, our new method has great potential to provide reliable and rapid determinations of major and trace element compositions for silicate rocks.     

Apatite Chlorine Concentration Measurements by LA‐ICP‐MS

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.     

A New LA‐ICP‐MS Method for Ti in Quartz: Implications and Application to High Pressure Rutile‐Quartz Veins from the Czech Erzgebirge

Experimental determination of the pressure and temperature controls on Ti solubility in quartz provides a calibration of the Ti‐in‐quartz (TitaniQ) geothermometer applicable to geological conditions up to ~ 20 kbar. We present a new method for determining ⁴⁸Ti mass fractions in quartz by LA‐ICP‐MS at the 1 μg g^?1 level, relevant to quartz in HP‐LT terranes. We suggest that natural quartz such as the low‐CL rims of the Bishop Tuff quartz (determined by EPMA; 41 ± 2 μg g^?1 Ti, 2s) is more suitable than NIST reference glasses as a reference material for low Ti mass fractions because matrix effects are limited, Ca isobaric interferences are avoided, and polyatomic interferences at mass 48 are insignificant, thus allowing for the use of ⁴⁸Ti as a normalising mass. Average titanium mass fraction from thirty‐three analyses of low temperature quartz from the Czech Erzgebirge is 0.9 ± 0.2 μg g^?1 (2s) using ⁴⁸Ti as a normalising mass and Bishop Tuff quartz rims as a reference material. The 2s average analytical uncertainty for individual analyses of ⁴⁸Ti is 8% for 50 μm spots and 7% for 100 μm spots, which offers much greater accuracy than the 21–41% uncertainty (2s) incurred from using ⁴⁹Ti as an analyte.     

Simultaneous Determination of Major and Trace Elements in Fused Volcanic Rock Powders Using a Hermetic Vessel Heater and LA‐ICP‐MS

Fused glass prepared without the addition of a flux is generally more homogeneous than a pressed powder pellet and thus ideal for analysis of bulk samples by LA‐ICP‐MS. In this work, a new glass‐making method using a boron nitride crucible was developed to prepare homogenous glass samples from silicate rock powder. The apparatus consisted of a small boron nitride vessel with net volume of about 34 mm³ and two molybdenum strips. Applying the summed metal oxide normalisation technique, both major and trace element contents in the fused glass were measured by LA‐ICP‐MS. Analyses of five geochemical reference materials (spanning the compositional range basalt–andesite–rhyolite) indicated that the measured SiO₂, Al₂O₃ and P₂O₅ contents matched the preferred values to within 5%, and the other major elements generally matched the preferred values to within 8%. Except for the transition metals, the measured trace element contents generally matched the preferred values to within 10%. Compared with the iridium heater method developed by Stoll et al. (2008), element volatilisation during high‐temperature melting was effectively suppressed in our method, but metal segregation caused by reduction of BN may cause loss of Cr, Ni and Cu. Although analysis with a large spot size has the advantage of improving counting statistics, matrix effects induced by mass loading of the ICP may hamper the accurate determination of some elements.     

Determination of Trace Element Mass Fractions in Ultramafic Rocks by HR‐ICP‐MS: A Combined Approach Using a Direct Digestion/Dilution Method and Preconcentration by Coprecipitation

A procedure is described for the determination of thirty‐seven minor and trace elements (LILE, REE, HFSE, U, Th, Pb, transition elements and Ga) in ultramafic rocks. After Tm addition and acid sample digestion, compositions were determined both following a direct digestion/dilution method (without element separation) and after a preconcentration procedure using a double coprecipitation process. Four ultramafic reference materials were investigated to test and validate our procedure (UB‐N, MGL‐GAS [GeoPT12], JP‐1 and DTS‐2B). Results obtained following the preconcentration procedure are in good agreement with previously published work on REE, HFSE, U, Th, Pb and some of the transition elements (Sc, Ti, V). This procedure has two major advantages: (a) it avoids any matrix effect resulting from the high Mg content of peridotite, and (b) it allows the preconcentration of a larger trace element set than with previous methods. Other elements (LILE, other transition elements Cr, Mn, Co, Ni, Cu, Zn, as well as Ga) were not fully coprecipitated with the preconcentration method and could only be accurately determined through the direct digestion/dilution method.     

Rapid Determination of Trace and Ultra Trace Level Elements in Diverse Silicate Rocks in Pressed Powder Pellet Targets by LA‐ICP‐MS using a Matrix‐Independent Protocol

A simple, single sample preparation involving pressed rock powder pellets was utilised to determine the trace and ultra trace abundances of petrogenetically important elements including high field‐strength elements and REEs by laser ablation‐ICP‐MS. One of the elements predetermined by XRF spectrometry served as an internal standard. The influence of sample preparation parameters (grain size, pellet compactness and amount of binding media) on analytical performance was also investigated, including sample homogeneity issues at the laser sampling scale. Line scanning with a high repetition frequency (20 Hz) and large beam diameter (200 μm) ensured ablation from a larger sample surface area, eliminating issues related to sample heterogeneity. A median grain size of about 10 μm for silicate rock powders was found to be sufficiently representative at this scale of laser sampling. Granitic rocks or samples containing resistant minerals such as zircon needed extra grinding to achieve grain sizes down to < 5 μm for better precision for elements that are concentrated in these phases. Using ¹³⁷Ba as an internal standard, reasonable accuracies within 15–20% for most of the high mass trace elements were achieved; in the case of low mass elements, it may deviate up to 40%. Precision of measurements rarely exceeded 15% RSD.     

Accurate Determination of Sr Isotopic Compositions in Clinopyroxene and Silicate Glasses by LA‐MC‐ICP‐MS

The low‐Sr content (generally < 100 μg g^?1) in clinopyroxene from peridotite makes accurate Sr isotopic determination by LA‐MC‐ICP‐MS a challenge. The effects of adding N₂ to the sample gas and using a guard electrode (GE) on instrumental sensitivity for Sr isotopic determination by LA‐MC‐ICP‐MS were investigated. Results revealed no significant sensitivity enhancement of Sr by adding N₂ to the ICP. Although using a GE led to a two‐fold sensitivity enhancement, it significantly increased the yield of polyatomic ion interferences of Ca‐related ions and TiAr⁺ on Sr isotopes. Applying the method established in this work, ⁸⁷Sr/⁸⁶Sr ratios (Rb/Sr < 0.14) of natural clinopyroxene from mantle and silicate glasses were accurately measured with similar measurement repeatability (0.0009–0.00006, 2SE) to previous studies but using a smaller spot size of 120 μm and low‐to‐moderate Sr content (30–518 μg g^?1). The measurement reproducibility was 0.0004 (2s, n = 33) for a sample with 100 μg g^?1 Sr. Destruction of the crystal structure by sample fusion showed no effect on Sr isotopic determination. Synthesised glasses with major element compositions similar to natural clinopyroxene have the potential to be adopted as reference materials for Sr isotopic determination by LA‐MC‐ICP‐MS.     

Evaluation of Major to Ultra Trace Element Bulk Rock Chemical Analysis of Nanoparticulate Pressed Powder Pellets by LA‐ICP‐MS

An efficient, clean procedure for the measurement of element mass fractions in bulk rock nanoparticulate pressed powder pellets (PPPs) by 193 nm laser ablation ICP‐MS is presented. Samples were pulverised by wet milling and pelletised with microcrystalline cellulose as a binder, allowing non‐cohesive materials such as quartz or ceramics to be processed. The LA‐ICP‐MS PPP analytical procedure was optimised and evaluated using six different geological reference materials (JP‐1, UB‐N, BCR‐2, GSP‐2, OKUM and MUH‐1), with rigorous procedural blank quantification employing synthetic quartz. Measurement trueness of the procedure was equivalent to that achieved by solution ICP‐MS and LA‐ICP‐MS analysis of glass. The measurement repeatability was as low as 0.5–2% (1s, n = 6) and, accordingly, PPP homogeneity could be demonstrated. Calibration based on the reference glasses NIST SRM 610, NIST SRM 612, BCR‐2G and GSD‐1G revealed matrix effects for glass and PPP measurement with NIST SRM 61×; using basalt glasses eliminated this problem. Most significantly, trace elements not commonly measured (flux elements Li, B; chalcophile elements As, Sb, Tl, In, Bi) could be quantified. The PPP‐LA‐ICP‐MS method overcomes common problems and limitations in analytical geochemistry and thus represents an efficient and accurate alternative for bulk rock analysis.     

Trace element geochemistry of primary mantle minerals in spinel‐peridotites from polygenetic MOR–SSZ suites of SW Turkey: constraints from an LA‐ICP‐MS study and implications for mantle metasomatism

Ophiolites exposed across the western Tauride Belt in SW Turkey represent tectonically emplaced fragments of oceanic lithosphere incorporated into continental margin following the closure of the Neotethys Ocean during the Late Cretaceous. The mantle sections of the ophiolites contain peridotites with diverse suites of geochemical signatures indicative of residual origin by melt depletion in both mid‐ocean ridge (MOR) and supra‐subduction zone (SSZ) settings. This study uses a laser‐ablation inductively‐coupled plasma‐mass spectrometry (LA‐ICP‐MS) for in situ measurements of trace elements in primary mantle phases in order to identify the upper mantle petrogenetic processes effective during variable stage of melt extraction in these discrete tectonic settings and to discriminate between the effects of reaction with chemically distinct mantle melts migrating through the solid residues. Trace element signatures in pyroxenes suggest small‐length scales of compositional variations which may be interpreted to be a result of post‐melting petrogenetic processes. Relative distribution of rare earth elements and Li between coexisting orthopyroxene‐clinopyroxene pairs in the peridotites suggests compositional disequilibrium in sub‐solidus conditions, which possibly reflects differential effects of diffusive exchange during melting and melt transport or interaction with subduction melts/fluids. On the basis of Ga abundances and Ga–Ti–Fe⁺³# [Fe⁺³/(Fe⁺³ + Cr + Al)] relationships of chrome‐spinels it is documented that the peridotites have experienced the combined effects of partial melting and variable extent of melt‐solid interaction. The MOR peridotites have spinels with geochemical signatures indicative of melt‐depleted residual origin with subsequent incompatible element enrichment through melt impregnation, while the Ga–Ti–Fe⁺³# relationships of chrome‐spinels in SSZ peridotites indicate that these highly depleted peridotites are not simple melt residues, but have been subject to significant compositional modification by interaction with subduction related melts/fluids. The observed compositional variations, which are related to long‐term tectonic reorganisation of oceanic lithosphere, provide evidence for a time integrated evolution from a mid‐ocean ridge to a supra‐subduction zone setting and may be a possible analogue to explain the coexistence of geochemically diverse MOR–SSZ suites in other Tethyan ophiolites. Copyright © 2011 John Wiley & Sons, Ltd.     

Trace Element Determination by ICP‐AES and ICP‐MS: Developments and Applications Reported During 2006 and 2007

This review describes developments in trace element determination using inductively coupled plasma‐atomic emission spectrometry (ICP‐AES) and inductively coupled plasma‐mass spectrometry (ICP‐MS) that were reported in 2006 and 2007. It focuses on the application of ICP techniques to geological and environmental samples; fundamental studies in ICP‐MS and ICP‐AES instrumentation have largely been ignored. New advances in ICP‐MS and ICP‐AES were incremental over this period, partly because both techniques are now well‐established. A continuing shift towards the hyphenation of low‐flow separation techniques has sparked activity in the development of appropriate low‐flow interfaces, and papers discussing interference removal also contribute significantly to the volume of research for both ICP‐AES and ICP‐MS. Whereas the majority of new ICP publications concerned advances in ICP‐MS analysis rather than ICP‐AES, development for ICP‐AES still occurs in almost all areas, particularly in sample introduction and hyphenated techniques.     

LA‐ICP‐MS Analysis of Small Samples: Carbonate Reference Materials and Larval Fish Otoliths

This article proposes a methodology to analyse the composition of very small carbonate samples such as larval fish otoliths. The chemical composition of otoliths, which are carbonate structures in the inner ear, is often used to explore population dynamics in fishes. Recent advances in laser ablation‐inductively coupled plasma‐mass spectrometry have suggested its potential application to this field. In this study, analyses were performed using a 193 nm ArF Resonetics LA system, coupled to an Agilent 7700X‐ICP‐MS, with the following ablation parameters: a beam diameter of 5 μm, energy of 3 mJ, 2.7 J cm^?2, laser repetition rate of 10 Hz and translation speed of 2.5 μm s^?1. NIST SRM 610 glass was used as the primary calibration material. Performing this protocol, characterisation of a USGS GP‐4 reference material was achieved with suitable precision and accuracy, but the USGS MACS‐3 reference material appeared more heterogeneous under the ablation conditions tested. Calibration was performed using two different beam diameters (5 and 11 μm). Capelin (Mallotus villosus) otoliths measuring between 10 and 20 μm in diameter were tested. Even though a smaller beam diameter and lower energy were used compared with those normally employed to analyse larger otoliths, the method was successful.     

A Practical Approach for Collecting Large‐n Detrital Zircon U‐Pb Data sets by Quadrupole LA‐ICP‐MS

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.     

Characterisation of Apatites as Potential Uranium Reference Materials for Fission‐track Dating by LA‐ICP‐MS

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.     

Speeding Up the Analytical Workflow for Coltan Fingerprinting by an Integrated Mineral Liberation Analysis/LA‐ICP‐MS Approach

Coltan (the African trade name for columbite‐tantalite, a tantalum ore) is one of several raw materials that finance the civil wars in the eastern provinces of the Democratic Republic of the Congo. To improve the transparency along the tantalum trade chain, a ‘certificate of origin’ for so‐called ‘conflict minerals’ has been recommended by the United Nations. Accordingly, the German Federal Institute for Geosciences and Natural Resources (BGR) has developed an analytical fingerprint procedure for coltan. Mineral formation age, modal mineralogy and chemical composition are important fingerprint parameters. The original workflow to obtain these parameters was streamlined and is now based on mineral liberation analysis and LA‐ICP‐MS. The use of an ICP‐MS instrument with a detector system covering an extended linear dynamic range and the application of an internal standard‐independent calibration strategy allowed data for major and trace element determination and mineral formation age estimates to be obtained simultaneously. The analytical results of this new approach were compared with analytical techniques of the original workflow and showed excellent agreement in terms of mineralogical and chemical characterisation and mineral formation age of coltan samples. Within a test, samples of different origin were allocated correctly and simple, binary mixtures were also identified successfully.     

Dating Micrometre‐Thin Rims Using a LA‐ICP‐MS Depth Profiling Technique on Zircon from an Archaean Metasediment: Comparison with the SIMS Depth Profiling Method

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.     

Non‐Matrix‐Matched Calibration for the Multi‐Element Analysis of Geological and Environmental Samples Using 200 nm Femtosecond LA‐ICP‐MS: A Comparison with Nanosecond Lasers

LA‐ICP‐MS is one of the most promising techniques for in situ analysis of geological and environmental samples. However, there are some limitations with respect to measurement accuracy, in particular for volatile and siderophile/chalcophile elements, when using non‐matrix‐matched calibration. We therefore investigated matrix‐related effects with a new 200 nm femtosecond (fs) laser ablation system (NWRFemto200) using reference materials with different matrices and spot sizes from 10 to 55 μm. We also performed similar experiments with two nanosecond (ns) lasers, a 193 nm excimer (ESI NWR 193) and a 213 nm Nd:YAG (NWR UP‐213) laser. The ion intensity of the 200 nm fs laser ablation was much lower than that of the 213 nm Nd:YAG laser, because the ablation rate was a factor of about 30 lower. Our experiments did not show significant matrix dependency with the 200 nm fs laser. Therefore, a non‐matrix‐matched calibration for the multi‐element analysis of quite different matrices could be performed. This is demonstrated with analytical results from twenty‐two international synthetic silicate glass, geological glass, mineral, phosphate and carbonate reference materials. Calibration was performed with the certified NIST SRM 610 glass, exclusively. Within overall analytical uncertainties, the 200 nm fs LA‐ICP‐MS data agreed with available reference values.     

U‐Th Zircon Dating by Laser Ablation Single Collector Inductively Coupled Plasma‐Mass Spectrometry (LA‐ICP‐MS)

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).     

A Method for Rapid Determination of Re and Os Isotope Compositions Using ID‐MC‐ICP‐MS Combined with the Sparging Method

A simple, rapid method for the determination of Re and Os concentrations and isotope compositions using isotope dilution multi‐collector inductively coupled plasma‐mass spectrometry (ID‐MC‐ICP‐MS) combined with Carius tube digestion and sparging introduction of Os was developed. For Os measurement, four channeltron ion counters to detect different Os isotopes were used simultaneously, which led to a drastic reduction in the measurement time. Rhenium isotopes were measured by means of eight Faraday cups with solution nebulisation and an ultrasonic membrane desolvator. The representative ¹⁸⁸Os count rate of an Os standard solution containing 50 pg of total Os was approximately 110000–120000 cps at the onset of measurement; the Re intensity of our in‐house 10 pg g^?1 standard solution reached 1820 V/μg g^?1 with a sample uptake rate of 95–99 μl min^?1. These values indicate that the sensitivity of the method was sufficient even for samples with low Re and Os concentrations, such as chert. As the temporal variations of the amplification efficiency of the ion counters differed from one another, we adopted a sample‐calibrator bracketing method to correct the measured Re and Os isotope ratios. The Re and Os concentrations via the isotope dilution method and the ¹⁸⁷Os/¹⁸⁸Os ratios of two sedimentary rock reference materials (JMS‐2 and JCh‐1) on the basis of the isotope ratios determined by the MC‐ICP‐MS and by negative thermal ionisation mass spectrometry (N‐TIMS) were comparable within their ranges. Based on Os isotope measurement of the IAG reference material [Durham Romil Os (DROsS)], the average difference from the recommended value and precision of Os isotope measurements by the sparging method in combination with multi‐ion‐counters were 0.72% and 0.76% [1RSD (%), n = 29], respectively. The precisions in the ¹⁸⁷Os/¹⁸⁸Os ratios [1RSD (%)] of JMS‐2, JCh‐1 and DROsS were 0.35–0.71, 1.56–3.31 and 0.99–1.28%, respectively, which depended on their Os ion intensities. No systematic difference was observed between the Re and Os geochemical compositions of JCh‐1 and JMS‐2 obtained by means of digestion with inverse aqua regia and CrO₃‐H₂SO₄ solutions, suggesting that either acid solution can be used for the sparging method of sedimentary rock samples. As CrO₃‐H₂SO₄ solution is believed to liberate predominantly the hydrogenous Re and Os fraction from organic‐rich sediment, the sparging method combined with CrO₃‐H₂SO₄ digestion and multi‐ion‐counters in the mass spectrometry is expected to be a powerful tool for reconstructing the secular change in marine Os isotope compositions with high sample throughput.     

LA‐(MC)‐ICP‐MS Trends in 2006 and 2007 with Particular Emphasis on Measurement Uncertainties

Research in 2006 and 2007 dealing with laser ablation‐(multicollector)‐inductively coupled plasma‐mass spectrometry, LA‐(MC)‐ICP‐MS, involved studies concerned with optimising the technique itself, as well as applying the method to a variety of problems in the Earth sciences. The causes of elemental and isotopic fractionation produced during laser ablation continues to be of considerable interest, with evidence mounting that processes occurring both at the ablation site and in the argon plasma of the ICP are culpable. There is growing excitement in the use of femtosecond lasers for LA‐(MC)‐ICP‐MS, with the hope that they reduce or eliminate melting and non‐congruent volatilisation at the ablation site and thus approach stoichiometric sampling. Ablation chamber design emerged as a serious concern, particularly with respect to achieving the rapid washout needed for fine‐scale compositional mapping of geological objects. LA‐MC‐ICP‐MS provided data for a wide range of isotopic systems, especially hafnium, but also B, S, Mg, Cu, Fe, Sr, Nd, Pb and U. Measurement uncertainties in LA‐ICP‐MS were discussed by several researchers, and are critically reviewed here ‐ total uncertainties for trace element concentration measurements of silicates including errors on the calibration values of common reference materials are ～10% (95% confidence limits), though the precision of individual spot measurements (50 to 100 μm) is much better, ～1% RSD, using a 193 nm laser and a sector field‐ICP‐MS. LA‐ICP‐MS U‐Pb ages for zircon and other U‐rich accessory phases are claimed by most geoanalysts to have 2s uncertainties of ～0.7 and 1.3% respectively but the actual accuracy of the method is probably only as good as ～2% (2s), when uncertainties associated with laser‐induced Pb/U fractionation are included.     

Classical and New Procedures of Whole Rock Dissolution for Trace Element Determination by ICP‐MS

Sample digestion is a critical stage in the process of chemical analysis of geological materials by ICP‐MS. We present a new HF/HNO₃ procedure to dissolve silicate rock samples using a high pressure asher system. The formation of insoluble AlF₃ was the major obstacle in achieving full recoveries. This was overcome by setting an appropriate digestion temperature and adding Mg to the samples before digestion. Sodium peroxide sintering was also investigated and the inclusion of a heating step to the alkaline sinter solution improved the recoveries of thirteen elements other than the lanthanides. The results of these procedures were compared with data sets generated by common acid decomposition techniques. Forty‐one trace elements were determined using an ICP‐QMS equipped with a collision cell. Under optimum conditions of gas flow and kinetic energy discrimination, polyatomic interferences were eliminated or attenuated. The measurement bias obtained for eight reference materials (BCR‐2, BHVO‐2, BIR‐1, BRP‐1, OU‐6, GSP‐2, GSR‐1 and RGM‐1) and intermediate precision (RSD) were generally better than ± 5%. The expanded measurement uncertainties estimated for two certified reference materials were mostly between 7 and 15%. New data sets for the reference materials are provided, including constituents with previously unavailable values and also for the USGS candidate reference material G‐3.