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We present detailed characterization of Tanz zircon megacrysts for the microbeam determination of U–Pb ages, Zr isotopes, Hf isotopes, O isotopes and trace element mass fractions. This batch of dark brown zircon megacrysts from Tanzania contains 269 ± 103 μg g−1 U (Th/U ∼ 0.154), and its total weight is 9.06 kg. The largest Tanz zircon megacryst in this batch weighs 366 grams. The calculated average accumulated alpha-radiation dosage is 0.54 × 1018 events per g for the Tanz zircon, which correlates with a 'well crystallized' structure. Through a large number of laser ablation ICP-MS, laser ablation MC-ICP-MS and SIMS measurements, it is found that Tanz zircon megacrysts are quite uniform in U–Pb ages, O isotopes and Zr isotopes at scales of tens of microns. The Tanz zircon has chemical abrasion isotope dilution TIMS (CA-ID-TIMS) determined mean isotopic ratio values of 0.09180 ± 0.00013 (2SD, n = 47) for 230Th corrected 206Pb/238U, 0.7473 ± 0.0014 (2SD, n = 47) for 207Pb/235U and 0.059069 ± 0.000067 (2SD, n = 47) for 230Th corrected 207Pb/206Pb. The CA-ID-TIMS method yielded a mean 230Th corrected 206Pb/238U age of 566.16 ± 0.77 Ma (2SD, n = 47). The determined mean δ18OVSMOW and δ94/90ZrSRM3169 values of the Tanz zircon megacrysts are 6.52 ± 0.28‰ (2SD, n = 29) and −0.01 ± 0.06‰ (2SD, n = 35) by gas source mass spectrometry and double spike TIMS, respectively. All of these values are in good agreement with the statistical mean values of microbeam measurements and are proposed as the best reference values for Tanz zircon megacrysts. These features make the Tanz zircon megacrysts suitable as primary U–Pb age and Zr–O isotope reference materials for microbeam analysis. However, our LA-MC-ICP-MS data suggest a relatively wide distribution of Hf isotope compositions in the Tanz zircons (0.281821 ± 0.000042, 2SD, n = 321), which makes Tanz zircons not an ideal Hf isotope reference material for microbeam analysis. We propose the Tanz zircon megacrysts as a potential reference material for the primary external calibration or monitoring of analytical validation for microbeam determination of U–Pb ages and Zr–O isotopes. [ABSTRACT FROM AUTHOR]

MC-ICP-MS has become one of the most powerful analytical methods for Si isotopes in bulk liquid and solid samples in the past decade. Laser ablation provides direct sampling of solid samples, avoiding laborious chemical digestion procedures. As for powder bulk samples, the preparation of stable and homogeneous targets prior to measurements, and strategies to minimize potential matrix effects, are critical for accurate isotopic analysis. In this study, an accurate and precise method for Si isotope ratio measurements by fs-LA-MC-ICP-MS of bulk silicate rock samples was established. A new laser fusion sample preparation technique was developed to achieve fast and homogeneous fusion of silicate rock powders (including granite and granodiorite that contain abundant refractory minerals) into glasses. Compared to the pressed pellet technique, the measurement precision for fused glasses was improved ∼5.7-fold. Matrix effects during Si isotopic analysis were observed when using non-matrix matched calibration protocols under normal dry-plasma instrument conditions with both ns- and fs-laser using a raster ablation mode. Matrix effects were eliminated by the addition of water vapor into the plasma, realizing accurate non-matrix matched calibration. In addition, using a fs-laser provided better measurement precision, with the internal and external precisions being improved ∼1.85 and ∼2.4 fold compared to a ns-laser at nearly equal signal intensities. Five well characterized silicate rock reference materials were analyzed using fs-LA-MC-ICP-MS calibrated against NBS-28 and BHVO-2G. Results obtained for δ29Si and δ30Si for these five reference materials were in agreement with previously reported values, confirming the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

A simple and rapid method using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) for direct multi-element analysis of wine samples without any sample pretreatment is described. Bestowed with its micro-sample consumption, the proposed method offers advantages of direct multi-element analysis in wine samples with high ethanol (1–20%) and salt contents, insignificant carbon deposits, reduced matrix effects, and better analytical performance. External calibration using either the solid reference material NIST 610 glass or aqueous standard solutions in combination with an indium internal standard provides accurate results. This calibration strategy offers a solution to the lack of a multi-element certified wine reference material for matrix-matched calibration. Twenty elements (Li, B, Mg, Al, V, Mn, Co, Cu, Zn, Rb, Sr, Y, Cs, Ba, La, Ce, Pr, Nd, Pb, and U) were determined in the wine samples. The proposed method was validated by a comparison with the conventional solution nebulization ICPMS method, with satisfying results. The detection limits for these elements were 0.01–1 ng mL−1. The proposed method also has great potential for multi-element analysis in other beverages. [ABSTRACT FROM AUTHOR]

To overcome the major shortcomings in conventional ICP-MS analysis with sample introduction by nebulization, a new solution sampling method was developed using laser ablation (LA). With this sampling method, water-related interferences were reduced by 1–2 orders of magnitude, the effects of which are similar to those obtained in membrane desolvation ICP-MS. Another important advantage of this method is that the matrix effects became insignificant in the ICP-MS analysis whether employing a matrix with the sample dilution factor varying between 80 and 2000 or an acid matrix ranging from 2% to 30% (v/v) HNO3. Compared with LA-ICP-MS analysis of solids, this sampling method exhibited 70–250 times improvement in signal sensitivity and the detection limits for most elements were two orders of magnitude lower. Unlike solid sample analysis, the commonly observed time-resolved element fractionation during laser ablation was negligible in solution sampling by LA. With the widely used reference material NIST 610 silicate glass as the external calibration standard and indium as the internal standard element, major and trace elements in a series of geological reference materials (ranging from mafic to felsic rocks) were successfully determined: the feasibility was verified with accuracies within 10% for 45 elements, and most of the precisions were reported as RSD better than 7%. Besides, due to the high tolerance of matrix effects, this method is comparatively green and environment friendly because of the minute consumption of acid and ultrapure water during the sample preparation process, which was reduced by 20–100 times compared to that in the conventional nebulization method. Being simple and effective, this method opens up a new prospect for the solution sampling of ICP-MS analysis. [ABSTRACT FROM AUTHOR]

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Abstract: Rutile and zircon in eclogites from the main hole of the Chinese Continental Scientific Drilling (CCSD-MH) were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and electron microprobe (EMP). Both single spot and profile analyses of large matrix rutiles (>60μm) generally demonstrate core–rim variability of Pb, Sr, Zr and U. Pb and Sr show enrichment at the rims, while Zr and U decrease in concentration from the cores to the rims. Correspondingly, temperatures estimated by Zr-in-rutile geothermometers are higher within the cores (mainly in the range of 680–740°C) than at the rims by 10–30°C. We note that estimated temperatures within the cores of matrix rutiles correlate positively with grain diameter. This suggests that the Zr content in rutiles is not only dependent on temperature and pressure, but is also affected by fluid activity and Zr diffusion. Estimated temperatures within the cores of matrix rutiles merely represent lower limits of the peak ultra-high pressure (UHP) metamorphic temperatures. Combined with Th/U and Ce/Lu ratios, rare earth element (REE) patterns and 206Pb/238U ages, Ti-in-zircon geothermometers can be used to distinguish the thermal evolution of eclogites during the UHP metamorphism. Zircons of 745±8.0Ma (2σ, n =3) show evidence of the temperatures at which they crystallized from the original magma. Zircons of 240±7.0Ma (2σ, n =11) with flat HREE patterns suggest a definite temperature range (689±18°C (2σ, n =11)) for the prograde metamorphism. Although 226Ma is generally considered the time of the peak UHP metamorphism for the Dabie–Sulu orogen, except for a few grains with a maximum temperature of 744°C, most of the 226±2.0Ma (2σ, n =12) zircons indicate lower temperatures (average=698±12°C (2σ, n =12)). These data imply that the 226Ma zircons were probably not products of the peak UHP metamorphism, but might instead be associated with the pressure decrease in the post-peak metamorphism. The youngest zircons (<220Ma) provide evidence for temperatures (682±14°C (2σ, n =11)) associated with the retrograde metamorphism. Geothermometers that incorporate both rutile and zircon indicate that there may have been experienced a locally short-lived heating event for eclogites from the CCSD-MH. [Copyright &y& Elsevier]

The sulfur isotope is an important geochemical tracer in diverse fields of geosciences. In this study, the effects of three different cone combinations with the addition of N 2 on the performance of in situ S isotope analyses were investigated in detail. The signal intensities of S isotopes were improved by a factor of 2.3 and 3.6 using the X skimmer cone combined with the standard sample cone or the Jet sample cone, respectively, compared with the standard arrangement (H skimmer cone combined with the standard sample cone). This signal enhancement is important for the improvement of the precision and accuracy of in situ S isotope analysis at high spatial resolution. Different cone combinations have a significant effect on the mass bias and mass bias stability for S isotopes. Poor precisions of S isotope ratios were obtained using the Jet and X cones combination at their corresponding optimum makeup gas flow when using Ar plasma only. The addition of 4–8 ml min −1 nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to significantly enlarge the mass bias stability zone at their corresponding optimum makeup gas flow in these three different cone combinations. The polyatomic interferences of OO, SH, OOH were also significantly reduced, and the interference free plateaus of sulfur isotopes became broader and flatter in the nitrogen mode (N 2 = 4 ml min −1 ). However, the signal intensity of S was not increased by the addition of nitrogen in this study. The laser fluence and ablation mode had significant effects on sulfur isotope fractionation during the analysis of sulfides and elemental sulfur by laser ablation MC-ICP-MS. The matrix effect among different sulfides and elemental sulfur was observed, but could be significantly reduced by line scan ablation in preference to single spot ablation under the optimized fluence. It is recommended that the d 90 values of the particles in pressed powder pellets for accurate and precise S isotope analysis should be less than 10 μm. Under the selected optimized analytical conditions, excellent agreements between the determined values and the reference values were achieved for the IAEA-S series standard reference materials and a set of six well-characterized, isotopic homogeneous sulfide standards (PPP-1, MoS 2 , MASS-1, P-GBW07267, P-GBW07268, P-GBW07270), validating the capability of the developed method for providing high-quality in situ S isotope data in sulfides and elemental sulfur. [ABSTRACT FROM AUTHOR]

Despite the large number of successful applications of LA-ICP-MS, elemental fractionation remains the main limitation for many of its applications in the Earth sciences. This limitation is particularly notable for high spatial resolution analysis. Elemental fractionation and mass-load effect in silicate glasses NIST SRM 610 and GSE-1G were investigated by using 193 nm ArF excimer nanosecond (ns) laser and 257 nm femtosecond (fs) laser ablation systems coupled to inductively coupled plasma mass spectrometry. Contrary to those observed in ns-LA-ICP-MS, the most elemental fractionation at the small spot sizes of 16–24 μm are lower than that at the large spot sizes of 44–60 μm in fs-LA-ICP-MS. The significantly different fractionation behaviors of Li, Na, Si, K, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Cs and U between silicate glass materials NIST SRM 610 and GSE-1G observed in 193 nm excimer LA-ICP-MS are eliminated by using 257 nm fs-LA-ICP-MS at high spatial resolution. In addition, the mass load effect and matrix dependent mass load effect are also found to be reduced by using fs-LA-ICP-MS in comparison with ns-LA-ICP-MS. Except for Sb, Pb and Bi, the elemental fractionation is independent on the laser fluence chosen, which is irrespective of ns- or fs-LA-ICP-MS. In this study, a spot size of 24 μm was used to test the capabilities of LA-ICP-MS analysis at high spatial resolution. The agreement between our data and the reference values is better than 10% for most of the elements in MPI-DING, USGS, and NIST glasses by using fs-LA-ICP-MS. For ns laser ablation analysis, the accuracy is highly dependent on the calibration strategies used (conventional external calibration method or 100% oxide normalization method) and the selected external reference materials (NIST SRM 610 or GSE-1G). The much less laser-induced elemental fractionation and matrix effect in fs-LA-ICP-MS in comparison with 193 nm excimer LA-ICP-MS make it more suitable for the analysis of silicate materials at high spatial resolution. [ABSTRACT FROM AUTHOR]

Abstract: A novel signal smoothing device for laser ablation inductively coupled plasma mass spectrometry was developed. The “wire” signal smoothing device consists of a copper cylinder filled with steel wire, with an internal volume of approx. 94cm3. The effectiveness of the “wire” signal smoothing device was evaluated with respect to both signal stability and decay time. With the developed “wire” smoothing device, no oscillation of the signal intensity was observed, even at a repetition rate of 1Hz. This finding indicates that this device is well suited for routine optimization of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The signal stability was improved by a factor of 11 compared to the absence of a signal smoothing device at a repetition rate of 1Hz. Another significant advantage of the “wire” smoothing device is that the signal decay time is similar to that without the signal smoothing device. These properties cause the “wire” smoothing device to be well suited for low repetition rate laser ablation analysis, which provides smaller elemental fractionation and better spatial resolution. The proposed “wire” signal smoothing device has been successfully used for high depth resolution zircon dating. [Copyright &y& Elsevier]