Neptune Plus Research Articles

Cu isotopes in minerals of the Mikheevskoe gold-copper-porphyry deposit (Southern Urals)

Research subject. Minerals of Cu from the Mikheevskoe gold-copper-porphyry deposit in the Southern Urals. Aim. To obtain preliminary data on the isotopic composition of Сu in minerals of various ore types from the largest porphyry deposit of the Urals followed by their interpretation. Methods. The 65Cu/63Cu isotope ratio values were determined using a multicollector inductively coupled plasma mass spectrometer Neptune Plus at the Research Center “Geoanalytik” (IGG of Ural Branch of the Russian Academy of Sciences). In total, 12 samples of three main technological ore types from this deposit were analyzed. Results. The δ65Cu values in the minerals of sulfide, friable, and oxidized ores ranged from –0.36 to +0.25‰ (chalcopyrite, fahlore), from –0.64 to +0.68‰ (bornite, chalcocite, pyrite), and from –2.14 to +0.30‰ (malachite, azurite), respectively. Conclusions: The absence of wide variations in δ65Cu values indicates the formation of the deposit under the conditions of a limited number of stages of hydrothermal ore formation, associated with the evolution of a single hydrothermal system. The obtained data agree well with the values of δ65Cu in porphyry-type deposits from different regions of the world. The conducted study contributes to the current knowledge on behavior of Cu-isotopes in minerals from ore deposits.

A Catalyst Tube-Equipped Dual-Stage Tube Furnace System for Accurate Hg Isotopic Determination of Ore Samples Using Neptune Plus Multicollector Inductively Coupled Plasma Mass Spectrometry.

Mercury (Hg) isotopes, which display mass-dependent fractionation and mass-independent fractionation, provide a multidimensional tracer to decipher the source of metals in mineral deposits. However, mineral ore samples usually contain abundant interfering elements (e.g., Te) that can cause inaccurate Hg isotopic analysis. Available acid digestion and combustion methods failed to remove these interfering elements, hindering the application of Hg isotopes for metallogenetic tracing. Here, we developed a new dual-stage tube furnace system employing a Mn-containing catalyst tube to pretreat mineral ore samples. This method yielded good Hg recoveries (100.5 ± 3.8%, 1SD, n = 15) and low levels of interfering elements in sample solutions, allowing for accurate analysis of a series of ore standard reference materials (GBW-11108v: coal; GSO-3: Cu-Ag sulfide ore; GBW 07859: Au-Te sulfide ore). The new method was also successfully applied to measure the Hg isotopic composition of magmatic and hydrothermal ore deposits, which yielded a large range in Δ199Hg value (-0.19 to 0.22‰) for ore deposits formed in different geological settings, highlighting the future applications of this method for metallogenic tracing, especially tracing the source of metals in mineral ore deposits.

Implementation and experience of using methods for analyzing the isotopic composition of Sm and Nd, Rb and Sr in rock samples at the Geoanalitik Center for Collective Use

Research subject. AGV-2 and BHVO-2 geochemical reference materials for studying the Sm, Nd and Rb, Sr isotope systems along with various rocks and mineral samples. Materials and Methods. An analysis of the isotopic composition of Sm, Nd and Rb, Sr was carried out using Neptune Plus and Triton Plus mass spectrometers. Aim. To implement analytical techniques for the isotopic composition of Sm and Nd, Rb, and Sr in various rock and mineral samples using two types of multicollector mass spectrometers – inductively coupled plasma NeptunePlus and thermal ionization TritonPlus (Thermo-Fisher), as well as a description of the procedure of processing experimental data and the experience in using techniques at the “Geoanalitik” shared research facilities of the IGG UB RAS for the period 2015-2023. Results. The analytical techniques implemented included (1) column chromatography using various ion-exchange resins, optimised for the ratio of labour costs/quality of analytical results; (2) the measurement of isotope ratios using two types of mass spectrometers; (3) the correction of mass bias of isotope ratios and the determination of Sm and Nd, Rb, and Sr concentrations by the isotope dilution method using 149Sm+150Nd and 85Rb+84Sr spikes. Testing of the techniques was carried out using the AGV-2 and BHVO-2 geochemical reference materials; their metrological characteristics were presented. When using TritonPlus, the reproducibility (BHVO-2, n=60) of measurements of 143Nd/144Nd, 147Sm/144Nd isotope ratios and Sm and Nd concentrations are ±0.000020, ±0.0004, ±1.3 and ±0.4, respectively; indicators of correctness of determining the ratios 143Nd/144Nd and 147Sm/144Nd – 0.001 and 0.25% and concentrations of Sm and Nd – 2%; the reproducibility (BHVO-2, n=63) of measurements of 87Sr/86Sr, 87Rb/86Sr isotope ratios and concentrations (Rb and Sr) are ±0.0025%, ±1.5%, ±2%, respectively. The uncertainty of a single measurement of the 143Nd/144Nd and 87Sr/86Sr isotope ratio, represented by the standard error of the average single measurement in the sample, does not exceed 0.0025%. Conclusions: the results obtained for the geochemical reference materials are in satisfactory agreement with those provided in the GeoReM database, as well as with the certified values provided by the United States Geological Survey (USGS). The described analytical techniques are used at the “Geoanalitik” shared research facilities of the IGG UB RAS to analyse various rock and mineral samples. The work presents a number of experimental results obtained, which are subsequently used in geochronological applications.

Optical-spectroscopic and isotope-geochemical characteristics of zircons from diamond-bearing placers in Yakutia as indicators of diamond ore bodies

Research subject. Zircon grains from diamond placers of the Molodo and Ebelyakh rivers of the Yakut Arctic. Aim. To study the indicator characteristics of zircon to determine sources of diamonds and ways of their transfer to placers; to analyze optical-spectroscopic and isotope-geochemical parameters of zircon grains, their microelemental, U-Pb, and Lu-Hf isotope composition. Materials and methods. A LA-ICP-MS analysis of the U-Pb isotopic and trace element composition of zircon was carried out using a NexION 300S mass spectrometer with an NWR 213 attachment. An analysis of the Lu-Hf isotope system was carried out using a Neptune Plus mass spectrometer with an NWR 213 attachment, located in a room of cleanliness class 7 ISO at the Geoanalitik Center for Collective Use (IGG Ural Branch of the Russian Academy of Sciences, Ekaterinburg). Raman spectra were obtained using a LabRAM HR800 Evolution confocal spectrometer. CL spectra were obtained using a Jeol JSM6390LV scanning electron microscope equipped with a Horiba H-CLUE iHR500 attachment. Results. The local optical spectroscopic characteristics (Raman spectra and catholuminescence) of zircon grains were established, which made it possible to substantiate the conclusion about their high crystallinity and homogeneity (monochrony), as well as to select international zircon standards with similar characteristics for use in LA-ICP-MS analysis to ensure similar conditions for evaporation of the substance and fractionation parameters of the U and Pb elements. LA-ICPMS data on the microimpurity, U-Pb and Lu-Hf isotopic composition of zircon grains from diamond placers, as well as the dose values of their self-irradiation, are presented. Conclusions. The obtained U-Pb dating contributes to reconstructing a more precise history, character, and sequence of manifestation of kimberlite magmatism, tectonic processes, and migration routes of kimberlite material and diamonds across the Siberian craton, within the Yakut kimberlite province.

Determination of Unbiased δ34S and Δ33S Values by MC‐ICP‐MS Using Down to 30 nmol of Sulfur

The multi‐collector inductively coupled plasma‐mass spectrometer is an instrument suited to measuring sulfur isotopes in all types of samples, from ice cores and river waters to carbonates and Archaean rocks. Its main advantage is the more convenient method of sample preparation, as sulfate does not need to be reduced but purified from the sample through ion exchange. This method allows the measurement of unbiased and precise δ34S values from samples as small as 10‐nmol with a typical intermediate precision of 0.15‰ (2s) at 95% confidence. So far, no attempt has been made to understand at which levels of analytical precision and bias MC‐ICP‐MS could provide ∆33S values. Here, the first standard addition experiment undertaken for ∆33S evaluation shows that measurement results on a Neptune Plus MC‐ICP‐MS allows us to calculate ∆33S values identical to those established by other measurement principles, for samples down to 30 nmol S, with an intermediate precision as good as 0.05‰ (2s). Though this precision is not as good as the analytical precision of data acquired by the SF6 method, the advantages of small sample size and straightforward sample handling make it a very useful tool for investigating past and modern aspects of the sulfur cycle.

Stable cerium isotope analysis of geological materials by MC-ICP-MS

We report stable cerium (Ce) isotopic compositions of terrestrial rocks and investigate Ce isotopic fractionation during column chemistry in this study. Cerium was separated from matrix elements by a single-stage extraction technique using Eichrom DGA resin. Ce isotope ratios were measured using a Thermo Scientific Neptune Plus MC-ICP-MS employing a sample–standard combined with a Sm-doping method. The data accuracy and precision of Ce isotope analyses were rigorously examined by two different laboratories. The δ142Ce values of mono-elemental Ce standards (JMC304 and CDUT-Ce) relative to NIST SRM 3110 solution were − 0.005 ± 0.042‰ (2SD, N = 9) and 0.118 ± 0.033‰ (2SD, N = 6), respectively. The δ142Ce of the manganese nodule (NOD-P-1) measured in two laboratories were 0.177 ± 0.035‰ (2SD, N = 7) and 0.172 ± 0.034‰ (2SD, N = 8), respectively; NOD-A-1 were 0.116 ± 0.028‰ (2SD, N = 8) and 0.104 ± 0.028‰ (2SD, N = 9), respectively. The offset between these two manganese nodules could be possibly related with their unique diagenetic environments. The δ142Ce of two USGS standards diabase W-2a was −0.036 ± 0.046‰ (2SD, N = 3), basalt BHVO-2 was −0.019 ± 0.036‰ (2SD, N = 4). Ce isotopic compositions of three Chinese reference standards granite gneiss GBW07121, diabase GBW07123, and stream sediment GBW07301a were 0.039 ± 0.033‰ (2SD, N = 5), 0.068 ± 0.027‰ (2SD, N = 5) and 0.046 ± 0.015‰ (2SD, N = 3), respectively. The reported data will be helpful for quality assurance and inter-laboratory comparison for high-precision Ce isotopic studies.Full recovery is important to achieve high precision and high accuracy data for metal isotopes. To understand Ce isotope behavior during column separation, an experiment with different Ce cuts was conducted. The δ142Ce of JMC304 and NIST SRM 3110 in five different Ce subcuts varied from 0.047 ± 0.020‰ (2SD, N = 3; 0–25% cut) to −0.029 ± 0.047‰ (2SD, N = 5; 45–100% cut), and 0.058 ± 0.047‰ (2SD, N = 4; 0–11% cut) to −0.022 ± 0.033‰ (2SD, N = 4; 32–100% cut), respectively. δ142Ce of these subcuts showed small ranges, but isotopic fractionation of Ce did occur during column chemistry and light isotopes are preferentially retained in the DGA resin.

Determination of Lu and Hf Mass Fractions and 176Hf/177Hf Ratios in Mafic‐Ultramafic Rock Reference Materials by Multi‐Collector Inductively Coupled Plasma‐Mass Spectrometry

Reported data for Lu, Hf mass fractions and 176Hf/177Hf isotopic ratios of mafic‐ultramafic rock reference materials (RMs) are rare at present, hampering the comparison of data quality between difference laboratories. Herein, we measured the Lu and Hf mass fractions and the 176Hf/177Hf isotopic ratios of ten mafic‐ultramafic rock RMs, including OKUM (komatiite), WPR‐1 (serpentinised peridotite), NIM‐N (norite), NIM‐P (pyroxenite), UB‐N (serpentinised peridotite), JP‐1 (peridotite), NIM‐D (dunite), MUH‐1 (serpentinised harzburgite), HARZ01 (harzburgite), DTS‐2b (dunite), which contain extremely low amounts of Lu and Hf (Lu, 2–150 ng g−1; Hf, 5–500 ng g−1). All measurements were conducted on a Neptune Plus multi‐collector inductively coupled plasma‐mass spectrometer employing an Aridus II desolvator inlet system and Jet sample/X skimmer cone configuration. The following RMs, OKUM, WPR‐1, UB‐N, JP‐1, NIM‐D, HARZ01 and DTS‐2b, have 176Hf/177Hf precision of less than 60 ppm (2s) at test portions of 0.06 to 0.3 g, and are good ultramafic RMs for Lu‐Hf systems. In contrast, significant Hf mass fraction and isotopic variability were observed in NIM‐N, NIM‐P and MUH‐1 at test portion masses of 0.1 to 0.3 g. Collectively, our study provides a new database that can be used by the geochemical community for evaluating the Lu‐Hf system of mafic‐ultramafic rocks.

New Analysis Protocol for Stable Isotopes by a Standard Doping Method─An Example of Antimony.

The current analytical methods of stable antimony isotopes are cumbersome and not suitable for rock samples with low antimony content (<1 μg/g). In this study, we propose a new protocol for antimony isotopic analysis with a single column of AG50W-X8 resin and antimony standard doping. This method separates antimony effectively from matrices and then mixes it with the Sb standard. As Te does not affect the accuracy of antimony measurement when the Te/Sb ratio is low, we can obtain an accurate Sb isotope composition of the mixture. Then, we can calculate the antimony isotope composition of natural samples. The error propagation of the mixing and calculation processes was evaluated by the Monte Carlo method, and no significant error was found. The antimony isotope compositions were measured using a Thermo Fisher Scientific Neptune Plus multicollector-inductively coupled-mass spectrometry instrument. The instrumental mass bias of Sb isotopes was corrected with a standard-sample bracketing combined with a Sn internal normalization technique. Using the standard doping method, the measured δ123Sb values of standard solutions (Alfa, SPEX, GSB, and SCP) relative to NIST SRM 3102a were 0.02 ± 0.03‰ (2SD, N = 50), 0.29 ± 0.03‰ (2SD, N = 15), 0.24 ± 0.03‰ (2SD, N = 56), and 0.30 ± 0.03‰ (2SD, N = 15), respectively. The reproducibility for δ123Sb was better than 0.03‰ (2SD) throughout one year. This methodology has been testified by geological samples, yielding δ123Sb identical to the previously reported values. The actual Sb consumption for each sample test is as low as 5 ng. This standard doping method provides new insights into the analytical strategy of stable isotopes.

Permian-Triassic flood basalts in the pre-Jurassic basement of the Arctic zone of the West Siberian platform

Research subject. Permian-Triassic flood basalts in the basement of the Arctic zone of the West Siberian Platform locate mainly in graben-rift structures. Flood basalts in this region remain to be understudied in comparison with other areas of its distribution, mainly due to the significant depth of their occurrence (4–6 km).Materials and methods. 36 core samples from 11 superdeep and deep boreholes were studied. Isotopic ratios were measured on mass spectrometers NEPTUNE PLUS (Nd, Sm) and TRITON PLUS (Rb, Sr). Bitumen were studied using a Raman spectrometer LabRAM HR800 Evolution. The Raman spectra were deconvoluted (“Peak fitting” procedure), and the bitumen conversion temperature was estimated.Results. About half of the samples of volcanic rocks underwent metamorphism of the prehnite-pumpellite and locally greenschist facies or intense low-temperature hydrothermal alteration. The studied basalts are close to typical flood basalts and are somewhat similar to island-arc volcanic rocks in terms of their geochemical characteristics. For the first time, thin inclusions of bitumen were found in the amygdalae of Permian-Triassic basalts in the superdeep borehole Tyumenskaya SG-6 at a depth of 7310.6 m. A high similarity of the studied volcanics by geochemical characteristics and the isotopic composition of Sr and Nd with the flood basalts of the Siberian platform is shown.Conclusions. The presence of a negative Ta, Nb, Ti anomaly, as well as a negative Ce anomaly, in some of the analyzed samples indicates a possible contamination of the basalts by island arc volcanics and volcanogenic-sedimentary rocks. The temperature of transformation of bitumen in inclusions in basalts from the well Tyumenskaya SG-6 according to Raman spectroscopy is estimated at 150–300°C and generally corresponds to the temperature of metamorphism of the host basalts. The presence of bitumen in the amygdalae may indicate the migration of hydrocarbons through the basalts.

Early differentiation processes on Mars inferred from silicon isotopes

Accretion of terrestrial planets involved partial or global melting events such as magma oceans or magma ponds. Mars experienced large-scale differentiation very early in its history, as shown by its 146Sm-142Nd and 182Hf-182W record. The broad variations in ε142Nd and ε142W of SNC meteorites highlight the presence of mantle sources that must have remained isolated, at least partly, after the crystallization of a global magma ocean. In this study, we have investigated whether the crystallization of the martian magma ocean could have generated mantle reservoirs characterized by different silicon isotope signatures, as the fractionation of Si isotopes between minerals and melts is known to depend on pressure. Thus, the goal of this study was to investigate whether there were any relationships between magma ocean crystallisation and possible variations in the Si isotope record of SNC meteorites. High resolution silicon isotope measurements were performed on twelve meteorites from the Shergottite, Nakhlite and Chassignite groups using a Neptune Plus MC-ICP-MS in dry plasma mode. The δ30Si values are in good agreement with previous studies but display a narrower range of variations with a mean value at −0.46 ‰ ± 0.07 (2SD). A magma ocean crystallization model shows that the range of δ30Si in SNCs is consistent with that generated by magma ocean crystallisation. In particular, there is a correlation between calculated 147Sm/144Nd for the moderately depleted mantle sources with δ30Si values; this correlation is consistent with the crystallization model if one includes trapped melt in the cumulates. In contrast, enriched shergottites displayed a very homogenous composition in Sm/Nd ratios, despite significant variability in δ30Si. This observation could be related to either fluid-rock interactions or redox effect during magma differentiation. Altogether, silicon isotope compositions of SNC provide new constraints about magma ocean crystallization processes in Mars.

A rapid method of simultaneous chromatographic purification of Li and Mg for isotopic analyses using MC-ICP-MS

Lithium (Li) and Magnesium (Mg) isotopes have been widely used as valuable tracers to study geological processes. In general, several column separation procedures have been used to separate Li and Mg. In this study, we present an optimized protocol for the rapid and simultaneous purification of Li and Mg, which significantly reduces the separation time, required reagent volume, and procedural blanks compared to previous methods. Samples with small amounts of Li (generally 5 ng Li yielding Mg masses of 1–1200 μg) were separated, with the corresponding yields of Li and Mg being nearly 100%. Lithium and Mg isotope analyses were performed using an MC-ICP-MS (Thermo Scientific NEPTUNE Plus) and only <0.2 ng Li and <150 ng Mg were consumed for each analysis. Matrix-doping experiments reveal that the matrix effect is negligible for the determination of Li and Mg isotopes from a wide array of geological samples using our protocol. The robustness of the protocol has been validated by replicated analyses of standard solutions and geological standards, which yield long-term external 2σ precision better than ±0.6‰ for δ7Li and ±0.08‰ for δ26Mg. Lithium and Mg isotopic ratios of all reference materials measured in this study agreed well with previous data within uncertainties. The method developed in this study allows for the rapid and high-purity separation of Li and Mg and subsequent high-precision isotopic analyses of these elements.

Determination of Sm/Nd and Sr isotopic composition using an ICP-MS Neptune Plus equipped with an NWR 213 attachment for laser ablation

Research subject. The Sm/Nd isotope system was investigated using inter-laboratory natural samples of apatite, titanite, allanite, monazite, as well as intra-laboratory samples of apatite (from carbonatites, Ilmenogorsk massif, Ural), monazite (from pegmatites of the Aduy granite massif and its framing, Middle Urals) and titanite (from calcite veins, Saranov skoye chromite deposit, Middle Urals and from alkaline pegmatite, Shpat mine, Vishnevy mountains, South Urals). The Sr isotope system was investigated using inter-laboratory natural apatite samples and intra-laboratory apatite samples (from the apatite-carbonate vein, Slyudyanogorskoe deposit, Irkutsk region and from carbonatites, Ilmenogorsk massif, Ural).Methods. The research was carried using a Neptune Plus multicollector mass spectrometer with inductively coupled plasma (ThermoFisher) equipped with an NWR 213 (ESI) laser ablation attachment, located in a room of ISO class 7 at the “Geoanalyst” Center for Collective Use (IGG Ural Branch of the Russian Academy of Sciences, Ekaterinburg). Results. The article describes methodological approaches for studying Sm/Nd and Sr isotope systems in natural phosphate and silicate minerals by inductively coupled plasma mass spectrometry with laser ablation, implemented on the equipment of the Center for Collective Use “Geoanalyst” (IGG Ural Branch of the Russian Academy of Sciences, Ekaterinburg). A comparative analysis of the obtained results with those reported in literature showed their satisfactory agreement. The developed analytical approaches were used to study apatite samples (analysis of the Sr isotope system) and those of apatite, monazite, titanite (analysis of the Sr isotope system). Conclusions. The developed approaches to the analysis of Sm/Nd and Sr isotopic systems can be recommended for investigating such minerals, as apatite, titanite, allanite, monazite (analysis of the Sm/Nd isotope system); apatite (analysis of the Sr isotope system). The achieved analysis errors allow the results to be used for interpreting various geochemical processes.

Interferences and Matrix Effects on Iron Isotopic Composition Measurements by 57Fe-58Fe Double-Spike Multi-Collector Inductively Coupled Plasma Mass Spectrometry; the Importance of Calcium and Aluminum Interferences

Multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS) are widely used for Fe isotope measurements. The latter may be perturbed by interferences (notably from Cr and Ni) and matrix effects (notably from major elements), caused by elements remaining in the samples after purification. We quantified some of these perturbations and our ability to correct them whenever possible, using Thermo Neptune and Neptune Plus MC-ICPMS with a 57-58Fe double-spike mass bias correction. 54Cr and 58Ni isobaric interference corrections were found to be extremely efficient up to Cr/Fe=0.12 and Ni/Fe=0.04 (g/g natural Fe). Matrix effects were found negligible up to at least Na/Fe=175, Mg/Fe=10, K/Fe=1.5, and Mo/Fe=75 (g/g natural Fe). 28Si2+ interference was found negligible up to Si/Fe=50. Finally, we found that calcium and aluminum could cause significant interferences (e.g., 40Ca16O and 27Al2+), for Ca/Fe ≥ 2.5 and Al/Fe ≥ 2.5. The perturbation intensity relative to the Ca/Fe ratio was found dependent on the measurement conditions (plateau width). While working with samples with potentially high calcium or aluminum contents (such as calcite minerals or tests, bones and teeth, or marine samples and crustal rocks), we recommend to carefully take into account Ca and Al while tuning the instrument and checking the measurement accuracy with isotopic standards (i.e., doping the isotopic standard with Ca and Al levels comparable to those of the samples).

Single-Stage Extraction Technique for Ce Stable Isotopes and Measurement by MC-ICP-MS

The separation of Ce from other rare earth elements has not been well established because of their similar geochemical properties. In this study, we report a single-stage extraction technique to purify Ce from natural samples with Eichrom DGA resin. This method separates Ce effectively from matrices and interfering elements, such as Ba, La, and Nd. The Ce elution curve would not drift with different Ce loading masses and rock types. The Ce isotope compositions were measured using a Thermo Scientific Neptune Plus multicollector (MC)-inductively coupled plasma (ICP)-mass spectrometry (MS) instrument. The instrumental mass bias of Ce isotopes was corrected with a sample-standard bracketing combined with a Sm-doping method. The δ142Ce values of standard solutions (CDUT-Ce and JMC304) relative to National Institute of Standards and Technology SRM 3110 measured were +0.128 ± 0.028‰ (2SD, N = 30) and 0.005 ± 0.038‰ (2SD, N = 30), respectively. The reproducibility for δ142Ce was better than 0.040‰. The Ce isotopic compositions of nine United States Geological Survey standard rocks, including carbonatite, basalt, andesite, quartz latite, dolerite, rhyolite, and granodiorite, were measured in this study. Our result showed that δ142Ce values of these rocks varied slightly, indicating that insignificant fractionation occurred during igneous processes. The technique proposed in this study is simple and time-efficient, which is beneficial for further studies on Ce isotope geochemistry.

Improved protocols for Zn purification and MC-ICP-MS analyses enable determination of small-scale Zn isotope variations

In this study we show that following a newly proposed protocol for stable Zn isotope ratio measurements on a ThermoFisher Scientific Neptune Plus MC-ICP-MS significantly improves the long-term external reproducibility down to < ± 0.025‰ 2SD on δ66/64ZnJMC-Lyon for a single static analysis with 90 measurement cycles of 4.2 s integration time each. This protocol includes: (i) stable isotope measurements in medium-mass resolution mode (R > 6500) to prevent the influence of any polyatomic interferences; (ii) the use of a double-spike, which in our case was a previously designed 64Zn-67Zn mixture; (iii) Zn purification with a two-column anion exchange method; (iv) thorough pre-run sample Zn purity checks and signal matching between sample and reference standard solutions; and, (v) pre-run adjustment of sample carrier and desolvating nebulizer system (DNS) gas flows such that the oxide formation rate determined on the 140Ce16O+/140Ce+ ratio remains below 1%. Following these routines, we obtain long-term external reproducibilities of 0.290 ± 0.017‰ 2SD for the IRMM-3702 (n = 145) certified Zn isotope amount reference material (RM) and − 9.974 ± 0.025‰ 2SD for the Alfa Aesar (n = 75) in-house Zn standard solution. The averages of sets of five single measurements of the IRMM-3702 RM and the Alfa Aesar standard solution narrow down the external reproducibility to ± 0.006‰ and ± 0.023‰ (both given as two standard deviations; for pooled data referred to as 2SD*), respectively. Alternatively, five-fold numbers of measurement cycles can reach the same external reproducibility for single measurements. The δ66/64ZnJMC-Lyon compositions of certified natural rock reference materials obtained by means of individual digests and analyses accurately reproduce the literature values, but our data also show that different batches of the BHVO-2 can be isotopically heterogeneous and clearly affect the reproducibility (BIR-1a: 0.247 ± 0.023‰, n = 17; BCR-2: 0.268 ± 0.025‰, n = 12; BHVO-2 #3323: 0.323 ± 0.024‰, n = 6; BHVO-2 #0535: 0.353 ± 0.015, n = 5, all 2SD). In cases where no effect of heterogeneity on reproducibility could be determined, we report the lowest uncertainty for replicate RM digests combined with multiple measurements (JB-2: 0.225 ± 0.012‰ 2SD, n = 3, i = 15). Mixtures between solution digests of the BIR-1a and BHVO-2 in combination with data pooling of five single measurements indeed demonstrate a measurement accuracy of < ± 0.010‰ 2SD*, emphasizing the analytical capability of the proposed method to depict small-scale Zn isotope variations. With the overall analytical improvement, we seek a better discrimination between variable, and potentially overlapping processes causing Zn isotope fractionation in various terrestrial reservoirs.

δ114/110Cd Values of a Suite of Different Reference Materials

The δ114/110Cd values of thirty‐four environmental and geological reference materials, including rocks, sediments, soils and biological samples, were determined on a Neptune Plus MC‐ICP‐MS instrument using a 111Cd‐113Cd double spike technique. An intermediate measurement precision of better than ± 0.074‰ (2s) was achieved with different reference materials (RMs) of highly variable matrices and Cd contents. The uncertainty of δ114/110Cd values was assessed by calculating the 95% confidence interval of the results from this study and the literature using Student's t‐test. Our measurements of nine previously analysed RMs yielded δ114/110Cd values that were indistinguishable from previous results. New reference values for the thirty‐four geological and biological RMs are reported here. The comprehensive data set for these RMs provides guidelines for quality assurance and inter‐laboratory comparison for Cd isotope determination. The large range of δ114/110Cd values in rock (−0.001 to +0.287‰) and biological RMs (−0.806 to +0.142‰) suggests that Cd isotope ratio measurement results are a useful tool to study biogeochemical processes.

Study of Lu/Hf isotopic composition of zircons using a Neptune Plus multicollector inductively coupled plasma mass spectrometer with an NWR 213 laser ablation attachment

A technique of analyzing the isotopic composition of Lu and Hf and for determining the Lu/Hf and Hf/Hf isotopic ratios in zircons is presented using a Neptune Plus (Thermo Scientific) mass spectrometer with inductively coupled plasma with an NWR 213 (ESI) laser ablation attachment. On the example of Mud Tank, GJ-1, 91500, Plesovice and Temora-2 standard zircon samples, the uncertainty of a single measurement of the 176Hf/177Hf ratio has been obtained in the range of 0.002-0.008% in the form of 2σ (with a crater diameter of 50 μm; when it decreased to 25 μm the measurement uncertainty of the 176Hf/177Hf ratio increased by 1.5-2 times). Under the optimum parameters of the NexION 300S with NWR213 with the aim of increasing the locality of the sequential study of U/Pb and Lu/Hf isotope systems, a comparative characteristic of the application of two approaches has been obtained: in adjacent grain areas (approach 1) and in one crater (approach 2). The metrological characteristics of analyzing the isotopic composition of Lu and Hf and for determining the Lu/Hf and Hf/Hf isotopic ratios in zircons have been determined. To establish the application limits of the developed technique, the factor planning of the experiment has been developed. It was established that with a Lu/Hf ratio of 1/50 or more, the technique is not recommended to be applied due to the incorrect allowance of the isobaric effect. The procedures for measuring and calculating the Lu/Hf isotopic ratios of the isotope system in zircon have been tested on zircon grains (samples NP-46 and NP-47) of the Neplyuevsky pluton (South Urals). The data obtained was in satisfactory agreement with the data of the A. P. Karpinsky Russian Geological Research Institute (VSEGEI).

Natural Clinopyroxene Reference Materials for in situ Sr Isotopic Analysis via LA-MC-ICP-MS.

Clinopyroxene is a major host mineral for lithophile elements in the mantle lithosphere, and therefore, its origin is vital for constraints on mantle evolution and melt generation. In situ Sr isotopic measurement of clinopyroxene has been available since the recent development of laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) in the 2000s. Therefore, there is an increasing demand for natural clinopyroxene reference materials for Sr isotope microanalysis. In this contribution, we present six natural clinopyroxene reference materials from South Africa (JJG1424) and China (YY09-47, YY09-04, YY09-24, YY12-01, and YY12-02) for Sr isotope microanalysis. The Sr content of these clinopyroxenes ranges from 50 to 340 μg g−1, which covers most natural clinopyroxene compositions. Homogeneity of these potential reference materials were investigated and evaluated in detail over a 2-year period using 193-nm nanosecond and 257-nm femtosecond laser systems coupled to either a Neptune or Neptune Plus MC-ICP-MS. Additionally, the major and trace element of these clinopyroxenes were examined by electron probe microanalyzer (EPMA) as well as solution and laser ICP-MS. The in situ 87Sr/86Sr values obtained for the six natural clinopyroxene reference materials agree well with data obtained using the thermal ionization mass spectrometer (TIMS) method. The Sr isotopic stability and homogeneity of these clinopyroxenes make them potential reference materials for in situ Sr microanalysis to correct instrumental fractionation or as quality control materials for analytical sessions. The new Sr isotope data provided here might be beneficial for microbeam analysis in the geochemical community.

A comparison of sulfur isotope measurements of geologic materials by inductively coupled plasma and gas source mass spectrometry

Sulfur isotope measurements by multi collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) require up to one hundred times less sulfur than traditional measurements via elemental analyzer isotope ratio mass spectrometry (EA-IRMS). Here, we report an improved MC-ICP-MS protocol for measuring δ34S values in different natural samples, specifically, calcium-sulfate minerals, carbonate associated sulfate, and dissolved sulfate in water. Sample preparation and subsequent anion exchange chromatography quantitatively recovers sulfur as sulfate. However, for samples with high and complex anion budgets, such as meteoric water, a stronger retention of sulfate on the anion exchange resin is observed relative to samples that contain sulfur as pure sulfate such as calcium-sulfate minerals and carbonate associated sulfate. An extended elution scheme with HNO3 is therefore required to achieve full recovery of sulfur, and thus accurate and reproducible δ34S values for the different materials investigated. Sulfur isotope measurements were performed on a Neptune Plus MC-ICP-MS coupled to an Apex-Ω desolvator, resulting in a “dry” plasma, negligible level of isobaric interferences, a sensitivity of >40 V ppm−1 sulfur, and a precision of 0.2‰ (2 S.D.) for δ34S for as little as 70 ng sulfur of a pure sulfate solution. The accuracy of the procedure was tested against duplicate δ34S EA-IRMS measurements for eleven different geologic samples. The EA-IRMS and MC-ICPMS values generally agree well within analytical uncertainty. However, procedural blank levels are on the order of a few tens of nanogram sulfur, and are thus the main limiting factor for accurate low-level sulfur isotope measurements with MC-ICP-MS.

Isotopic composition of lead from dikes and ores of the Vorontsovkoe gold deposit (Northern Urals)

Research subject . The Vorontsovskoe deposit belongs to gold deposits, in which gold is disseminated finely across carbonate-terrigenous rocks (Carlin-type). This study was aimed at identifying the sources of lead in various ore types (in skarn, jasperoid, tuff-sandstone and limestone breccia) and evaluating the role of magmatic rocks (apophises of Auerbakh intrusions and dykes of medium-basic composition) in the mineralization. M aterials and methods . Ore and rock samples for isotopic analysis were collected in the northern quarry of the deposit, as well as were retrieved from exploration holes. The lead isotopic composition was studied in the analytical centre Geoanalytic , Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences, using a mass spectrometer Neptune Plus on the basis of the TL N MC ICP MS method. Results. The lead isotopic composition of ores and igneous rocks indicates mixed mantle-crustal sources. The primary lead isotopic composition of igneous rocks corrected for the age of 400 Ma is characterized by a linear trend with wide variations in 207 Pb/ 204 Pb (15.6824–15.5182) and 206 Pb/ 204 Pb (18.1973–17.7707). The lamprophyre dykes feature the least radiogenic lead located between the evolutionary curves for the mantle and orogen in the Doe–Zartman model. The most radiogenic lead is typical of the granodiorite of the Auerbakh intrusion apophises. The analysis points of diorite porphyrite, gabbro-diorite and diorite dykes are located between the orogen and upper crust curves. The sulphide ores are characterized by lower variations in the primary lead isotopic composition compared to igneous rocks – 207 Pb/ 204 Pb (15.6009–15.5421) and 206 Pb/ 204 Pb (18.0434–17.8404). The most productive ores in tuff-sandstones and limestone breccias are characterized by a significant predominance of the crustal component over the mantle component. Their points in the diagram 207 Pb/ 204 Pb– 206 Pb/ 204 Pb are located between the curves for the orogen and the crustal source with µ 2 ( 238 U/ 204 Pb) = 9.74. Conclusion. Mantle lead in the dykes under study appears to reflect the nature of their parent magmas and may have been partially extracted by melts from the footwall mafic rocks containing pyrite ores. However, crustal lead is likely to have resulted from assimilating host rocks when magmatic melts reached the upper crust level. Crustal lead migrated with the metamorphic fluid formed by the heat action of the Auerbakh intrusion on sulphide-bearing volcano-sedimentary rocks. Mantle lead might have been transported by the fluid flow from a deepseated magmatic chamber.