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Ca isotope geochemistry has great potential for improving our understanding of magmatic systems and for tracing the deep Earth carbon cycle. There are still many open questions, however, regarding the proper application of this relatively novel proxy to the study of mantle-derived magmas, including (i) the possible effects of pressure on mineral-melt Ca isotope fractionation factors, and (ii) the potential for Ca isotopes to be used as tracers of recycled marine carbonates in mantle-derived magmas. Kimberlites are mantle-derived melts that are highly enriched in CO2 and are the deepest-sourced magmas (>200 km depth) known to erupt at Earth's surface, providing an excellent opportunity to explore these questions. We present Ca isotope data combined with detailed petrographic observations, bulk-carbonate C-O isotope data, and bulk-rock major element analyses, for a suite of 23 well-characterized kimberlite samples from their type-locality (Kimberley, South Africa). These kimberlites have abundant previous evidence for recycled surface materials in their mantle source, including low S isotope and moderately radiogenic Sr isotope compositions, yet display only limited variations in their Ca isotope compositions (δ44CaBSE of −0.08‰ to −0.27‰), with an average of −0.17 ± 0.02‰ (2SE, n = 21). This composition is indistinguishable from average carbonatites [−0.19 ± 0.03‰ (2SE, n = 106)] and OIB from recent studies [−0.16 ± 0.01‰ (2SE, n = 41)], and slightly lower than average MORB [−0.11 ± 0.02‰ (2SE, n = 31)]. Although our samples display a wide range of emplacement styles, alteration conditions, extents of magmatic differentiation, and degrees of mantle-cargo entrainment (i.e., xenocryst accumulation), we find no correlations between Ca isotopes and any of these factors. Instead, we find that low-degree partial melting of the likely kimberlite source lithology (i.e., carbon-bearing garnet lherzolite) yields modelled melt δ44CaBSE values ranging between −0.12‰ and −0.16‰ (at 1400–1500 °C), in agreement with the measured Ca isotope compositions of the Kimberley kimberlites. This observation, and the lack of heavy carbon isotope signatures in the examined samples, indicates that kimberlites do not require subducted carbonates in their mantle sources, despite their very high CO2 contents. Although several recent studies have suggested that equilibrium mineral-melt Ca isotope fractionation factors (e.g., 1000lnαgrt-melt) could be significantly different at higher pressures (i.e., due to pressure-induced changes in Ca[sbnd]O bond lengths and coordinations), our models successfully reproduce the kimberlite data using pressure-independent predictions for mineral-melt fractionations. It remains possible, however, that differences in isotopic fractionation due to the peculiar composition of kimberlite melts (e.g., high CO2, low SiO2) are effectively cancelled out by competing pressure effects, and future work independently targeting these factors will be especially important for our understanding of Ca isotope fractionation in mantle-derived melts and the Ca isotope systematics of Earth's mantle., Geochimica et Cosmochimica Acta, 348, ISSN:0016-7037, ISSN:1872-9533

This work evaluates the use of femtosecond laser ablation multiple collector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS) for Zr isotopic analysis in zircons. The mass fractionation caused by instrumental mass discrimination was corrected by a combination of internal correction using Sr as an internal standard (coming from a NIST SRM 987 standard solution) and external correction using a matrix-matched standard. Several important instrument parameters were investigated, such as the effect of the addition of N2 and “wet” plasma condition, the mass fractionation behaviors between Zr isotopes and Sr isotopes, the position effect in laser ablation cell and the effect of laser ablation parameters (laser spot size and energy density). The Zr isotope compositions of seven zircons (GJ-1, 91500, Plešovice, Rak-17, Paki, Aus and Mala) were determined by the developed fs-LA-MC-ICP-MS and thermal ionization mass spectrometry (TIMS). Our fs-LA-MC-ICP-MS results for Zr isotope compositions agreed with TIMS analyses within analytical uncertainties, indicating the presented method is a suitable tool to resolve isotopic zoning in natural zircons. The results also suggest that GJ-1, 91500, Plešovice, Paki, Aus and Mala had the homogenous Zr isotope composition and could be considered as the potential candidates for the Zr isotope analysis in zircons, except Rak-17 which presented the large Zr isotope variation.

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.

Here we present Si and Zr isotopic data of SA01 and SA02 zircons via multi-technique analytical methods to evaluate the suitability of the two zircon reference materials for in situ Si and Zr isotopic analysis using femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS). Precise and accurate Si and Zr isotopic compositions were determined by solution nebulization (SN) MC-ICP-MS. Fifteen SN-MC-ICP-MS Si isotopic measurements on two aliquots of SA01 zircon solutions gave consistent results with an average δ30Si (relative to NBS28) value of −0.29 ± 0.08‰ (2SD), whereas a slight inter-grain offset was detected for the SA02 zircon with an average δ30Si value of −0.25 ± 0.16‰ (2SD, n = 12). The mean δ94/90Zr (relative to IPGP-Zr) values were 0.02 ± 0.03‰ (2SD, n = 9) and 0.02 ± 0.04‰ (2SD, n = 9) for SA01 and SA02 zircons, respectively. Extensive homogeneity test of both Si and Zr isotopic compositions was performed on SA01 and SA02 zircons by spot analysis with fs-LA-MC-ICP-MS. The Si and Zr isotopic results for SA01 zircon showed good agreement with our SN-MC-ICP-MS measurements, as did the Zr isotope results of SA02 zircon. In spite of the inter-grain offset in the Si isotopic composition revealed by SN-MC-ICP-MS, intra-grain homogeneity was confirmed for SA02 zircon by the LA-MC-ICP-MS method. In situ analyses of SA01 and SA02 zircons yielded mean δ30Si values of −0.24 ± 0.10‰ (2SD, n = 143) and −0.26 ± 0.12‰ (2SD, n = 135), and mean δ94/90Zr values of 0.03 ± 0.09‰ (2SD, n = 153) and 0.02 ± 0.09‰ (2SD, n = 153), respectively. Both solution and in situ dataset demonstrated the suitability of SA01 for calibrating in situ zircon Si and Zr isotopic analysis. We suggest that SA02 zircon is also a suitable reference material for micro-beam Zr isotopic analysis as well as a monitor for in situ Si isotopic analysis. Furthermore, an analytical approach using the spot mode of fs-LA is presented in this study. In situ Si and Zr isotopic analysis may benefit from it for improving spatial resolution and precision.

A new analytical method for the accurate and precise determination of stable zirconium isotope ratios in geological materials by thermal ionization mass spectrometry (TIMS) is presented. Isobaric interference from Mo was largely eliminated during filament heating and further reduced by off-line Mo interference correction. This methodology allows the complete elimination of Mo interference even with a Mo/Zr ratio up to 1. Separation of Zr from natural sample matrices was achieved by using a single DGA resin column with a small usage of acids (15 mL of 7 mol L−1 HNO3 and 3 mL of 1 mol L−1 HF). A 91Zr–96Zr double spike was admixed with samples before digestion, which enabled the correction of isotope fractionation that could occur during column separation and mass spectrometry measurement. The long-term measurement reproducibility of δ94Zr is generally better than ±0.06‰ (uncertainty represented by two standard deviations, hereinafter referred to as 2 SD), assessed by repeated analyses of Zr standard reference NIST SRM 3169 and eleven geological reference materials. The Zr isotope ratios of geological reference materials BHVO-2 and AGV-2 obtained in this study are consistent with the reported values measured by MC-ICP-MS, confirming the accuracy of the proposed method. This new method greatly simplifies the chemical separation process and is particularly suitable for Zr isotope analysis of complex matrix (especially for high Mo) samples.

This study presents a highly precise and accurate Ca isotope analysis method using laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) in calcium carbonates and calcium phosphates. High-sensitivity cones and nitrogen gas were used to improve the performance of the LA-MC-ICP-MS. The experiment results show that at the N2 mode, the signal intensity of 44Ca+ in the high-sensitivity cones (Jet + X cones) was 5-fold higher than that in the normal cones (S + H cones), while the polyatomic interferences of 40Ar1H1H+ and 40Ar16O+ in the high-sensitivity cones were suppressed by factors of 6.1 and 10.6, respectively, after the addition of 8 ml min−1 N2. The combination of high sensitivity cones and N2 addition did not increase the production of double charged ions. Additionally, the interference correction of doubly charged Sr ions was investigated in detail. The experiment results demonstrate that the concentration ratio of Sr to Ca (represented as I87Sr++/I44Ca+), the 87Sr/86Sr ratio and the mass fractionation factor of Sr (fSr) during the measurement process were key parameters for in situ Ca isotope ratios analysis. The threshold values of these key parameters were evaluated and are recommended to ensure an accurate correction of doubly charged Sr ions. Using the optimized instrumental conditions and correction strategies, an excellent within-run precision (

Determination of the copper (Cu) isotopic composition (δ65Cu) of seawater is difficult due to low Cu concentrations (0.3 to 7.6 nmol kg−1) and high salt content. Here, we present a new procedure for matrix separation and Cu preconcentration based on a combination of a Cu-selective resin column and an AG MP-1M anion exchange resin column. The Cu-selective resin shows a quantitative recovery of 102.3 ± 5.0% (mean, 2SD, n = 5) and high selectivity for Cu over the main cations (Na, Mg, K and Ca) in seawater, efficiently preconcentrating Cu in seawater. Due to the hydrophobic nature of the Cu-selective resin, it was necessary to accelerate the preconcentration process using a peristaltic pump. Subsequently, an anion exchange resin was used to acquire a pure Cu fraction and thus ensure the accurate determination of seawater δ65Cu. Seawater samples can be loaded on the Cu-selective resin column under a wide range of pH conditions (from pH = 4 to 9) instead of the narrow acidic pH range required in previous studies. The whole procedure is simple and has a low blank of 1.28 ± 0.48 ng Cu (n = 4). Results obtained from a series of doping experiments of seawater with an Alfa Cu standard confirmed the accuracy of the proposed method.

Copper (Cu) isotopes can be a useful tool to constrain the interaction of water and the environment, but they have not been widely applied to riverine research in the preceding decades. Isotopically heavy Cu in rivers (global average: about +0.7‰) compared to rocks (at about 0‰) has been attributed to: a) the mobilization of heavy Cu during oxidative weathering, and b) partitioning between an isotopically heavy, organically complexed dissolved pool, and an isotopically light pool adsorbed to particulates. Here, we report Cu concentrations and isotope ratios of the main stream of the Yangtze River and its several tributaries. We find that the Yangtze River exhibits anomalously heavy Cu isotope compositions compared to other rivers: δ65CuNIST 976 of dissolved Cu for the main stream, from Chongqing to Nanjing, ranges from +0.59 to +1.65‰, while the tributaries vary from +0.48 to +1.20‰. A negative correlation is observed between Cu concentrations and Cu isotope compositions. We attribute the anomalous Cu isotope geochemistry of the Yangtze River to two key features of the basin: first, the influence of the Three Gorges Dam (TGD), and second, the presence of extensive Cu sulphide deposits close to the lower reaches of the river. In the upper reaches, downstream towards the TGD, δ65Cu values increase as Cu concentrations decrease, reflecting the preferential adsorption of light Cu by sedimenting particulate phases. δ65Cu values continue to increase to a maximum of +1.65‰ in the middle reaches, at Guangxingzhou. The lower reaches, from Jiujiang to Tongling, are characterized by less positive values of δ65Cu (at about +0.60‰), due to the oxidative weathering of Cu sulphide deposits. The overall Cu-δ65Cu trend in the river reflects mixing of these waters from the lower reaches, influenced by Cu sulphides, with waters from upstream, which have lower Cu concentrations and elevated δ65Cu values.

The stable isotopes of calcium have tremendous potential for constraining the evolution of the mantle as well as fingerprinting the recycling of carbon in the mantle via subduction. In order to better identify possible contributions of subducted carbonate-bearing materials to upper mantle heterogeneity, we present Ca isotope data for peridotite xenoliths from Fanshi, northern North China Craton. These peridotites have previously been studied for major and trace element, Sr-Nd isotopic compositions. Two metasomatic events in the lithosphere mantle caused by subduction of carbonated sediments from the Pale-Asian oceanic slab, were previously identified: the first by carbonatite melt and the second by carbonate-rich silicate melt. δ44/40Ca (=((44Ca/40Ca)SAMPLE/(44Ca/40Ca)SRM915a − 1) × 1000) of clinopyroxenes (Cpx) in the Fanshi peridotites varies from +0.84‰ to +1.17‰ and δ44/40Ca of orthopyroxenes (Opx) from +0.82‰ to +1.22‰. δ44/40Ca of the clinopyroxenes show a larger variation than that could be attributed to partial melting and display positive and negative trends with (La/Yb)N and Ti/Eu, respectively, suggesting the effect of two distinct metasomatic events. A harzburgite, modified only by the early carbonatite metasomatism, has the highest δ44/40Ca (+1.17‰). The lherzolites affected by the second metasomatic melt show lower Δ44/40CaOpx-Cpx (=δ44/40CaOpx − δ44/40CaCpx, −0.11‰ to 0‰) than the un-metasomatized lherzolites (+0.11‰ to +0.24‰), implying that the second metasomatism triggered Ca isotope disequilibrium between the clinopyroxene and co-existing orthopyroxene. This is consistent with positive trends between δ44/40Ca and 87Sr/86Sr, (La/Yb)N in the clinopyroxenes of the lherzolites, indicating that the second metasomatism also resulted in high δ44/40Ca in the clinopyroxenes of the lherzolites (up to +1.09‰). Furthermore, the harzburgites and lherzolites converge toward the second metasomatic event in diagrams of 87Sr/86Sr versus δ44/40Ca, suggesting an extensive effect of the second metasomatism. The heavy Ca isotope signature in these metasomatic clinopyroxenes applies to both first carbonatite melt and second carbonate-rich silicate melt derived from carbonated sediments (>+1.17‰ and ∼+1.09‰, respectively). However, heavy Ca isotope composition is inconsistent with low δ44/40Ca in carbonated sediments from the Paleo-Asian ocean, but could be the characteristic of an evolved sediment-derived hydrous carbonate melt. This implies significant Ca isotope fractionation during subduction of carbonated sediments. While currently there is plenty of debate regarding the exact significance of Ca isotope heterogeneity in mantle rocks, our results show at a minimum that Ca isotopes are rather heterogeneous in supra-subduction mantle rocks and could be used to deciphering mantle metasomatic models and detecting recycled crustal materials.

Wide application of stable Ca isotopes requires reliable production of high-precision data and in recent years multiple collector inductively coupled plasma mass spectrometers (MC-ICP-MS) have been used as an alternative to traditional thermal ionization mass spectrometers. The main challenges in using MC-ICP-MS to measure stable Ca isotopes are scattered ions and peak tailing of high level 40Ar+ and 40Ca+ ion beams, along with variable interferences. In this study we optimize Ca isotopic measurements on a large geometry high resolution MC-ICP-MS (Nu Plasma 1700) operating in conventional hot Ar-plasma mode. 40Ar+ and 40Ca+ were trapped by a specially designed dummy bucket, to prevent scattering of ions that might affect the Ca isotopic measurement. Strontium and matrix elements in samples were eliminated to blank levels by chemical separation. Instrumental mass bias of Ca isotopes was corrected by a sample-standard bracketing method using a purified sea water Ca isotope standard. Potential effects of Ar-related interferences, Ca-hydride, acid molarity, concentration mismatch and matrix elements were evaluated. The results from both measurements and modeling suggest that 40Ar+ peak tailing and Ca-hydride cause negligible Ca isotopic offset under normal MC-ICP-MS operating conditions. The precision and accuracy were validated using the measurement of twelve well-characterized international reference materials and a pure Ca standard solution. The long-term external precisions are better than ±0.07‰ (2SD) for δ44/42Ca and ±0.10‰ (2SD) for δ43/42Ca. Calcium isotopic compositions of all reference materials measured in this study agree with previously published data within uncertainties.

A new, simple and efficient separation method to isolate Mo from complex geological sample matrices for high precision Mo isotope ratio measurements is described. The proposed separation method benefits from the high selectivity and high capacity of the TRU resin, which affords straightforward separation of Mo from complex sample matrices and achieves high yield (∼100%), efficient separation and low blank with the use of only a single mineral acid, HCl (1.5 M for loading and 0.5 M for eluting), and small volumes. As opposed to the commonly used separation protocols, neither redox reagents (e.g., H2O2 and ascorbic acid) nor highly toxic HF is required for the proposed separation protocol, making this separation method straightforward and more environment friendly to operate. Mo isotope ratios were measured by multi-collector inductively coupled plasma mass-spectrometry (MC-ICP-MS) using the 97Mo–100Mo double spike in combination with standard-sample bracketing for mass bias correction. The results obtained for igneous rocks, manganese nodules, shales and seawater samples are in good agreement with previously reported values, confirming that the proposed separation protocol is suitable for complex sample matrices and will further promote its geological applications.

Rivers are the main source of molybdenum (Mo) to the oceans, and estuaries represent an important interface between rivers and oceans within which Mo can be sequestered or isotopically fractionated. Determining the behavior of Mo in estuaries is thus essential for a full understanding of the global Mo cycle. Here, we present a case study of the modern Yangtze Estuary and adjacent East China Sea shelf, generating Mo concentration and isotopic data for both aqueous and solid phases (i.e., suspended particulate matter, or SPM, primarily consisting of clay minerals and Al-Fe-Mn-oxides). Aqueous Mo concentrations increase rapidly from ~13.9 nM (river water) to ~115 nM (seawater) through the mixing zone of the innermost continental shelf. Minor deviations from a salinity-based mixing relationship (positive at

Geochemical analysis of the 14.4-m-thick lacustrine succession of the Lower Cretaceous Yixian Formation (Jehol Group) has yielded new insights concerning vertebrate mass mortality events in the Lake Sihetun volcanic caldera in western Liaoning Province (northeastern China) that produced the Jehol Biota fossil lagerstatten. The long-term evolution of the caldera system resulted in a shift from felsic to mafic magma chemistry, accompanied by a reduced frequency of pyroclastic eruptions, declining hydrothermal activity, and lower lacustrine productivity. The basal Tetrapod Beds exhibit strong hydrothermal influence, as indicated by enrichments of boron (B), certain alkalis (Rb, Cs), rare-earth elements (REEs), yttrium (Y), and many metals (e.g., Co, Cr, Cu, Ge, Mo, Ni, Sb, U, V, and W), and by strongly negative molybdenum isotope compositions (δ98Mo to –2.50‰) that may record large fractionations between molybdate and thiomolybdate species in the Sihetun caldera hydrothermal system. In contrast, the overlying Fish Beds and Non-Fossiliferous Beds have an elemental and Mo-isotopic composition similar to calc-alkaline basalts (δ98Mo = –0.29 ± 0.04‰) in the surrounding watershed, suggesting weathering of Yixian Formation volcanic rocks as the major source of sediment. During its

The absolute determination of the Cu isotope ratio in NIST SRM 3114 based on a regression mass bias correction model is performed for the first time with NIST SRM 944 Ga as the calibrant. A value of 0.4471 ± 0.0013 (2SD, n = 37) for the 65Cu/63Cu ratio was obtained with a value of +0.18 ± 0.04‰ (2SD, n = 5) for δ65Cu relative to NIST 976. The availability of the NIST SRM 3114 material, now with the absolute value of the 65Cu/63Cu ratio and a δ65Cu value relative to NIST 976 makes it suitable as a new candidate reference material for Cu isotope studies. In addition, a protocol is described for the accurate and precise determination of δ65Cu values of geological reference materials. Purification of Cu from the sample matrix was performed using the AG MP-1M Bio-Rad resin. The column recovery for geological samples was found to be 100 ± 2% (2SD, n = 15). A modified method of standard-sample bracketing with internal normalization for mass bias correction was employed by adding natural Ga to both the sample and the solution of NIST SRM 3114, which was used as the bracketing standard. An absolute value of 0.4470 ± 0.0013 (2SD, n = 37) for 65Cu/63Cu quantified in this study was used to calibrate the 69Ga/71Ga ratio in the two adjacent bracketing standards of SRM 3114, their average value of 69Ga/71Ga was then used to correct the 65Cu/63Cu ratio in the sample. Measured δ65Cu values of 0.18 ± 0.04‰ (2SD, n = 20), 0.13 ± 0.04‰ (2SD, n = 9), 0.08 ± 0.03‰ (2SD, n = 6), 0.01 ± 0.06 (2SD, n = 4) and 0.26 ± 0.04‰ (2SD, n = 7) were obtained for five geological reference materials of BCR-2, BHVO-2, AGV-2, BIR-1a, and GSP-2, respectively, in agreement with values obtained in previous studies.

A detailed geochemical investigation of the Permian–Triassic boundary in a carbonate-ramp setting at Xiakou, South China, provides new insights regarding the role of volcanism in the largest mass extinction in Earth history. The Xiakou section records 9 intervals of volcanic activity, some producing up to 25-cm-thick composite ash layers, during the latest Permian and earliest Triassic. Each volcanic episode coincided with major changes in marine environments. The largest changes occurred in conjunction with volcanic interval VI-4, correlative with the latest Permian mass extinction, during which (1) the oceanic oxygen-minimum zone expanded (as shown by framboidal pyrite flux), (2) marine productivity declined sharply (as shown by multiple productivity proxies), and (3) climate conditions became more humid (as shown by increased clay fluxes). The mechanism by which volcanic eruptions forced marine environmental changes may be inferred from the relationship between ash layer thickness and the magnitude of the associated negative C-isotope excursion. The most likely connection is through volcanogenic methane release to the atmosphere, possibly as a result of magmatic intrusions into the West Siberian Coal Basin, triggering increases in global temperature and humidity. These climate changes in turn resulted in stronger oceanic stratification, oxygen-minimum zone expansion, and a decline in marine productivity. The Xiakou section is important in demonstrating links between volcanism and the marine environment during the Permian–Triassic transition interval.

Calcium isotopic compositions of sixteen Ca-bearing USGS geological reference materials including igneous and sedimentary rocks are reported. Calcium isotopic compositions were determined in two laboratories (GPMR, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan; and CIG, Centre for Isotope Geochemistry, University of California, Berkeley) using the 42Ca-48Ca double-spike technique by thermal ionisation mass spectrometry. As opposed to common cation exchange resin, a micro-column filled with Ca-selective resin (DGA resin) was used in order to achieve high recovery (> 96%) and efficient separation of Ca from the sample matrix. The intermediate measurement precision was evaluated at 0.14‰ (2s) for δ44/40CaSRM915a at GPMR, based on replicate measurements of pure Ca reference material NIST SRM 915a, NIST SRM 915b and seawater. Overall, the measurement uncertainties in both laboratories were better than 0.15‰ at the 2s level. Result validation was carried out for all available data sets. The Ca isotopic compositions of USGS reference materials are not only in agreement between GPMR and CIG, but also in agreement with previously published data within quoted uncertainties. The comprehensive data set reported in this study serves as a reference for both quality assurance and interlaboratory comparison of high precision Ca isotopic study.

An analytical protocol for the accurate and precise determination of the gallium isotope ratio in geological materials is presented for the first time by using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Separation of Ga from natural sample matrices was achieved by using a three-column ion-exchange chromatograph with one anion exchange AG MP-1M column and two cation exchange AG 50W-X8 columns. This approach provides an efficient purification with a low blank and high yield of Ga from an excess amount of Fe existing in geological samples. The instrument mass bias was monitored and corrected by using a model of standard-sample bracketing with internal normalization, and copper was used as an internal standard which was added to both the sample and standard solutions. The long-term external reproducibility of δ71/69Ga obtained is 0.04‰ (2SD). Ga isotopic compositions of geological reference materials including basalt, andesite, rhyolite, granodiorite, soil, sediment, carbonatite and shale were measured using the proposed approach. The 71Ga/69Ga ratio in these geological reference materials spanned over a rather narrow range between 0.74‰ and 0.90‰, relative to NIST SRM 994.

Three important factors, including the choice of an appropriate spike isotope pair, the composition of the double spike, and the ratio of the double spike to the sample, have been proven to have a significant effect on the precision of the double spike technique. Moreover, peak jump (i.e., dynamic) collection mode is frequently used, which could lead to more variable parameters such as cup configurations, ratio combinations and integration times in different jump lines. In order to optimize the above conditions under the peak jump mode, a Monte Carlo method that simulates uncertainties from Johnson noise and counting statistics is applied for the prediction of the precisions of measured results using the double spike technique. As an example, this model was used to predict the possibility of cup configurations and ratio combinations of three double spike pairs of 42Ca–48Ca, 43Ca–48Ca and 46Ca–48Ca, respectively, in two jump lines. Predicted internal precisions improved by 25%, 20% and 25% by using 42Ca–48Ca, 43Ca–48Ca and 46Ca–48Ca double spikes, respectively, under optimized conditions. The theoretically predicted optimum precision was verified by repeatedly measuring two standards of NIST SRM 915a and NIST SRM 915b using the 42Ca–48Ca double spike over several months. The observed internal precisions of δ44Ca in these two standards are in good agreement with the predicted internal precisions, validating the effectiveness of the proposed Monte Carlo technique. The observed external precisions in two standards are 8–9 times poorer than the internal precisions, probably due to an extra uncertainty source. Nevertheless, the optimal ratio combination yields the best external precision. As demonstrated, the proposed Monte Carlo simulation is an effective method to predict the optimal cup configurations, ratio combinations and integration times for the double spike technique using peak jump collection mode.

Aiming at the lack of expert and user participation problems in knowledge consulting, the paper proposes knowledge consulting service based on Hall for workshop of meta-synthetic engineering, and its characteristics, model and analysis of key technology are analyzed in detail, knowledge map provides the knowledge sharing platform of tacit and explicit knowledge, and also improve the process of visualization. In the model the expert and user are introduced and take part in discussion. In discussion, experts have a large number of tacit knowledge in their mind, users can ensure the accuracy and efficiency of the discussion, furthermore, the participation of users and experts can promote the formation of collective intelligence. The model can be applied to any complex knowledge consulting system, and can also improve the expert participating in knowledge sharing. At last a case study show the frame can improve the efficiency of knowledge consulting and meet the users need. Keywords-Knowledge Consulting; knowledge map; visuali zation; Hall for workshop of meta-synthetic engineering; HW ME; knowledge retrieval

Aiming at the problem existing in the current knowledge organization, a model of knowledge organization based on modular ontology is put forward. The model can provide an approach to knowledge organization autonomously and collaboratively, based on which advanced knowledge organization is discussed. To some extent, the model can improve the ability of knowledge reuse and knowledge integration, and reduce the complexity and difficulty of knowledge organization, realize personalized knowledge organization and interdisciplinary knowledge organization.