Sr Isotope Measurements Research Articles

Delineating population structure of resilient sea/river‐type sockeye salmon

AbstractConserving wild fisheries requires identifying and monitoring distinct populations, yet prevalent genetic approaches often do not integrate habitat data and may not fully delineate these structures. This issue is critical in sea/river‐type sockeye salmon (Oncorhynchus nerka), an ecotype whose specific spawning habitats better define distinct breeding populations. Despite possessing traits that confer greater resilience to climate change and significant contributions to wild fisheries, gene flow among groups dilutes genetic structure, making it difficult to track populations. We focus on sea/river sockeye from one of the Pacific Rim's largest Sockeye fisheries, combining river strontium (Sr) isotope predictions, otolith Sr isotope measurements, and a Bayesian assignment model with a 4‐yr radiotelemetry and genetic dataset (n = 1994) to delineate the geographic structure of spawning habitats. Our results identify four distinct subpopulations with unique natal habitat Sr isotope ratios previously undifferentiated by genetic methods, providing a novel approach to monitor critical groups over multiple years.

Effects of Faraday cup deterioration on Sr and Cr isotope analyses by thermal ionization mass spectrometry.

By comparing data from an extensive set of Sr and Cr isotope measurements performed on two different thermal ionization mass spectrometers (TIMS), using three sets of Faraday cups with different usage histories, we assess the effects of Faraday cup deterioration on high-precision isotope measurements by TIMS. We find that dynamic 84Sr/86Sr and 87Sr/86Sr measurements provide stable and reproducible results over the entire 56 months of this study, regardless of which set of Faraday cups is used. By contrast, static 84Sr/86Sr and 87Sr/86Sr measurements lead to deviant results, drifts over time, and in general exhibit larger scatter. For the most part, these differences can be attributed to changing Faraday cup efficiencies. For the instruments of this study we find that the center cup is most affected, consistent with this cup often receiving the highest ion beam intensities during measurements conducted in our laboratory. For Cr isotopes, we find that the correlation between mass fractionation-corrected 53Cr/52Cr and 54Cr/52Cr ratios observed for static measurements in several prior studies also reflects different Faraday cup efficiencies. Again, the changing efficiency of predominantly the center cup can account for the observed drift and correlation in 53Cr/52Cr and 54Cr/52Cr. Multi-static Cr isotope measurements reduce this drift, but still result in a residual correlation between the two ratios, suggesting this correlation in part also reflects unaccounted mass fractionation effects.

Revealing seasonal woolly mammoth migration with spatially-resolved trace element, Sr and O isotopic records of molar enamel

We investigated the mobility pattern of an Upper Palaeolithic woolly mammoth (Mammuthus primigenius) from the Kraków Spadzista site in southern Poland, one of the largest mammoth bone accumulations in Europe. We conducted in situ laser ablation (MC-) ICPMS Sr isotopic and trace element concentration measurements accompanied by spatially-resolved oxygen isotope measurements of dental enamel on a last upper molar tooth (M6). Our study documents excellent preservation of in vivo geochemical and isotopic records and reveals recurring changes in 87Sr/86Sr that oscillate between two endmembers and correlate with analogous variations in δ18O, as well as U and Sr concentrations. The observed periodicity corresponds to annual cycles of enamel mineralization as revealed by enamel histology and documents up to 11 years of woolly mammoths' life in a single dental plate. The high degree of correlation between the duration of enamel mineralization and the Sr and O isotopic records suggests that the mammoth migrated between two areas of distinct Sr isotopic composition as well as characteristic U and Sr concentrations, presumably forced by seasonal food availability. The mammoth grazed in southern Poland in winter time as indicated by lower δ18O values and likely moved 250–400 km northwards to the Polish midlands during summer. This migration pattern remained stable for at least 12–13 years of the animal's adult life as archived in this molar tooth. Our study documents a fixed mobility behaviour of an adult mammoth some 10,000 years before the Last Glacial Maximum.

New Reference Materials, Analytical Procedures and Data Reduction Strategies for Sr Isotope Measurements in Geological Materials by LA‐MC‐ICP‐MS

Laser ablation multi‐collector mass spectrometry (LA‐MC‐ICP‐MS) has emerged as the technique of choice for in situ measurements of Sr isotopes in geological minerals. However, the method poses analytical challenges and there is no widely adopted standardised approach to collecting these data or correcting the numerous potential isobaric inferences. Here, we outline practical analytical procedures and data reduction strategies to help establish a consistent framework for collecting and correcting Sr isotope measurements in geological materials by LA‐MC‐ICP‐MS. We characterise a new set of plagioclase reference materials, which are available for distribution to the community, and present a new data reduction scheme for the Iolite software package to correct isobaric interferences for different materials and analytical conditions. Our tests show that a combination of Kr‐baseline subtraction, Rb‐peak‐stripping using βRb derived from a bracketing glass reference material, and a CaCa or CaAr correction for plagioclase and CaCa or CaAr + REE2+ correction for rock glasses, yields the most accurate and precise 87Sr/86Sr measurements for these materials. Using the analytical and correction procedures outlined herein, spot analyses using a beam diameter of 100 μm or rastering with a 50–65 μm diameter beam can readily achieve < 100 ppm 2SE repeatability ("internal") precision for 87Sr/86Sr measurements for materials with < 1000 μg g‐1 Sr.

An investigation of factors affecting high-precision Sr isotope analyses (87Sr/86Sr and δ88/86Sr) by MC-ICP-MS

The stable strontium (Sr) isotope system is being increasingly utilized to move forward our understanding of environmental, geological, and cosmological processes. Two analytical techniques are commonly used to measure stable Sr isotopes: 1) double-spike thermal ionization mass spectrometry (DS-TIMS) and 2) Zr-doped sample-standard bracketing multi-collector inductively coupled plasma mass spectrometry (Zr-doped SSB via MC-ICP-MS). Relative to DS-TIMS, Zr-doped SSB via MC-ICP-MS allows simultaneous determination of both 87Sr/86Sr and 88Sr/86Sr ratios, increasing measurement efficiency and sample throughput. However, several factors limit the analytical precision and accuracy of this technique, including matrix effects and potential intra- and inter-session offsets of measured isotope ratios. In this study, we evaluate potential causes for the observed offsets. We performed a series of experiments to assess the effect of different solution matrices and sources of contamination on Sr isotope measurements and to explore potential underlying mechanisms. Our tests show that incomplete Sr recovery during chromatographic separation, mismatches of Sr and Zr concentrations and acid molarity between samples and bracketing standards, and cation contamination all affect the precision and accuracy of Sr isotope measurements. We present evidence that analyses using our recommended updated preparation procedure for Zr-doped SSB via MC-ICP-MS can achieve a long-term reproducibility (2σSD: 87Sr/86Sr = ±0.000015 and δ88/86Sr = ±0.03 ‰) comparable to that of DS-TIMS.

Stable Sr isotope (88Sr/86Sr) fractionation in calcite precious corals

Stable isotope ratios of Sr (88Sr/86Sr) are a novel indicator for identifying terrestrial and oceanic Sr cycling and biological processes. Here we evaluate the temperature dependence of stable Sr isotope ratios (δ88Sr) in the calcite skeletons of precious corals, known as octocorals. High-precision Sr isotope measurements by double spike thermal ionization mass spectrometry were applied to different precious corals (Corallium japonicum, Pleurocorallium elatius, P. konojoi, Corallium sp., Keratoisis sp., and Coralliidae sp.) collected from water depths of 30–1500 m in the Pacific Ocean, corresponding to annual mean water temperatures of 2.5 to 19.5°C. The precious corals showed mean δ88Sr values of 0.101 ± 0.023‰. The magnitude of Sr isotope fractionation between the skeleton and ambient seawater (Δ88Sr) is −0.291 and is about −0.1‰ lower than the value predicted from the precipitation of inorganic calcite. This fractionation is not affected by changes in skeletal Sr/Ca ratio and associated biological effects on δ88Sr are negligible. δ88Sr of precious coral skeleton is an excellent recorder of ambient seawater.

A Novel, Laser‐Based Microsampling Technique for Texturally Controlled, Combined and Complementary Sr and Nd Isotope Measurements in Silicate Minerals

The limitations of many in situ microsampling techniques, especially when applied to isotopic analyses, may result in lower measurement precision and limit the ability to compare different isotope systems within the same phase or the same isotope system between phases. High‐precision, combined and complementary isotopic measurements are typically limited to whole‐rock samples or mineral separates at the expense of textural context. We demonstrate that laser ablation instruments could offer an effective, non‐mechanical alternative to micro‐milling for delineating and extracting single crystals, interstitial phases, and sub‐crystal scale features from soluble‐resin thick sections for column chromatography and high precision ID‐TIMS measurement. Systematic testing demonstrated that both modern and legacy laser instruments are capable of ablating through plagioclase, pyroxene and fused glass to depths of 200 μm. Modern instruments offer software benefits to identifying optically‐indistinct petrographic features, chemical zoning and avoiding alteration phases by using overlain high‐resolution datasets. Extracting delineated targets of varying geometry was achieved under binocular microscope using common mineral‐separation tools. Analysis of RM glass used as mineral proxies indicate (a) no significant thermal aureole on ablated margins that could affect measured parent‐daughter ratios, (b) no elevated risk of contamination compared with traditional mineral separation techniques, (c) excellent blanks for low‐yield analyses and (d) high‐precision ID‐TIMS results (87Sr/86Sr and 143Nd/144Nd) for sub‐100 ng Sr loads and sub‐10 ng Nd loads.

High-precision Sr and Nd isotope measurements using a dynamic zoom lens-equipped thermal ionisation mass spectrometer

Techniques for the determination of radiogenic strontium (87Sr/86Sr) and neodymium (143Nd/144Nd) isotope ratios by Thermal Ionisation Mass Spectrometry (TIMS) are presented in this study. We have developed a 5 lines acquisition routine for both elements, taking advantage of the 16 Faraday cups available on the Nu Instruments TIMS in conjunction with an efficient zoom lens system. This allows increased flexibility regarding the number of lines in a multidynamic acquisition routine whilst maintaining optimal peak alignment and peak shape for every measurement line despite the fact that the detectors are not movable. The long-term reproducibility obtained for our Sr (NBS 987) and Nd (Rennes-Ames) standard solutions gives a (87Sr/86Sr)multidyn of 0.7102467 ± 0.0000043 (6.0 ppm, 2 s.d., n = 38) and a (143Nd/144Nd)multidyn of 0.5119537 ± 0.0000022 (4.2 ppm, 2 s.d., n = 31), respectively. We also report (87Sr/86Sr)multidyn and (143Nd/144Nd)multidyn for a set of terrestrial rock standards (including 5 basalts (BCR-2, BHVO-2, BIR-1, Be-N and BR-24), one rhyolite (RGM-1) and one andesite (AGV-2)) with the same, or greater, level of precision as for the pure standards solutions. This level of precision is 2 to 3 times better than the literature data for Sr isotope ratios, and comparable to the latest high precision data reported for Nd isotope ratios. This is the first paper reporting such high precisions for radiogenic Sr and Nd data generated using a TIMS from Nu Instruments. Significant statementHigh precision Sr and Nd isotopic measurements are of key importance in the field of Earth Sciences because they are powerful tools to trace sources of materials and to date them. Here, we report the first high-precision data for 87Sr/86Sr and 143Nd/144Nd (external error of 5–6 ppm for Sr and 4–5 ppm for Nd) measured using a Nu Instruments TIMS. Such precisions will open new opportunities in fields such as geochemistry, geochronology, cosmochemistry, archaeology or forensics.

Implications of strontium isotope and trace element variability in New Zealand kauri (Agathis australis)

New Zealand kauri trees are an important dendrochonologic resource in the southern hemisphere due to their long lifespans and the correlation of ring widths to El Niño - Southern Oscillation (ENSO)-events. This study represents the first chronology-constrained dendrochemical investigation of New Zealand kauri. Strontium isotope (87Sr/86Sr) and trace element analyses are combined to determine the potential for provenance (spatial) and environmental (temporal) dendrochemical investigations utilizing the geochemistry of kauri wood. Soil Sr isotopic measurements match 80% of the corresponding analyses from local trees and two of the four study sites have kauri isotopic compositions tightly clustered and distinctive, supportive of provenance investigations. The two sites which record inter-tree isotopic variability, a combination of variables, including geologic, atmospheric (dust and sea spray), and anthropogenic (land-use), all likely influence the isotopic and trace element variations. Discrete annual events or fluctuating conditions are difficult to observe from the isotopic tree ring record, reflecting the potential mobility of Sr within tree rings. However, the preservation of long term geochemical trends suggest processes such as climate change or anthropogenic soil modification may still be preserved in the kauri record.

Sr Isotopic Composition of NIES Certified Reference Material No. 28 Urban Aerosols

An interlaboratory study of the National Institute for Environmental Studies (NIES) certified reference material (CRM) No. 28 Urban Aerosols collected from the filters of a central ventilating system in a building in the Beijing city center from 1996 to 2005 was performed to obtain an information value of the Sr isotopic composition. The Sr isotopic composition was measured using multi-collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) to confirm the CRM’s within- and between-bottle homogeneity, and the results showed a 87Sr/86Sr ratio of 0.710227 ± 0.000019 (2SD, n = 18). The Sr isotopic compositions were intercompared using thermal ionization mass spectrometry (TIMS), which showed good agreement with values obtained at NIES. Subsequently, a consistent 87Sr/86Sr ratio was observed between two dissolution (hotplate vs. high-pressure bomb) and Sr separation (Sr spec resin vs. cation exchange resin) methods. To validate and reproduce the accuracy of our analytical methods, the Sr isotopic compositions of secondary reference materials, JB-1b and JA-2, were also measured. Our results showed that NIES CRM No. 28 is appropriate for the quality control of Sr isotope measurements of particulate matter analyses for environmental and geochemical studies.

High-precision multidynamic Sr isotope analysis using thermal ionization mass spectrometer (TIMS) with correction of fractionation drift

High-precision and high-accuracy measurement of the natural mass-independent variations of 84Sr/86Sr using thermal ionization mass spectrometry (TIMS) is crucial for understanding the planetary volatile depletion history and the heterogeneous isotopic reservoirs in the early Solar System. The recently reported μ84Sr values [defined as 106 × (84Sr/86Srsample/84Sr/86Srstandard – 1)] for terrestrial rock samples, however, show a significant discrepancy between static and multidynamic TIMS measurement results, indicating that the data from one or both measurement methods are biased by analytical artefacts. Coupled with this issue, the accurate μ84Sr values of terrestrial samples are also under debate. Here we present high-precision 84Sr/86Sr and 87Sr/86Sr data for a series of natural samples and the standard NIST SRM 987 measured using a new 3-line multidynamic TIMS method, with the aims to: (1) systematically evaluate and correct the fractionation drift effect in multidynamic Sr isotope measurements, (2) investigate the origin of the discrepancy between the μ84Sr values derived from static and multidynamic measurements, and (3) determine the accurate terrestrial μ84Sr value. Our data show that the rapid drift of isotopic fractionation during TIMS measurement can significantly bias the multidynamic 84Sr/86Sr ratio, but has only minor influence on 87Sr/86Sr. The previously observed static vs. multidynamic μ84Sr discrepancy has been reproduced in our study, and can be explained by the positive biases in multidynamic μ84Sr caused by the high fractionation rates of terrestrial samples compared to the standard. After correcting the fractionation drift effect using a linear interpolation method, the average multidynamic μ84Sr value of the terrestrial samples is in complete agreement with the multistatic result. We confirm that the standard NIST SRM 987 possesses an apparent 84Sr enrichment relative to the natural samples from the Earth, and conclude that the terrestrial samples have an average μ84Sr value of −31 ± 8 ppm (2 standard error). The fractionation drift-corrected multidynamic μ87Sr and μ84Sr results of SRM 987 show a pronounced correlation that is likely to be a combined effect of ion counting random error, uncorrected (or overcorrected) fractionation drift effect, and mixing of Sr ions evaporated from variably fractionated sample reservoirs on the filament. The two independent multidynamic 87Sr/86Sr ratios returned by our method exhibit a stable, small but resolvable offset, which most likely reflects systematic errors generated by an insufficient amplifier idle time setting. Our measurement method has also been applied to three standard materials that have been used in the early Solar System 87Sr/86Sr chronology studies from the 1970s till present to examine the reliability of the normalization method used for inter-laboratory comparison and to assure accurate cross-calibrations of these standards.

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 telltale signature of Archean lithospheric mantle in the Paraná continental flood basalts genesis

The origin of the Paraná Continental Flood Basalts (PCFB), which constitute one of largest magmatic provinces in the world, remains a very controversial subject, particularly whether melts are sourced in the mesosphere (deep mantle plume), asthenosphere and/or lithosphere. In an effort to scrutinize those competing hypotheses, new measurements of Os, Nd, Sr and Pb isotopes, along with major and trace elements are presented for low-TiO2 tholeiites from the province. This suite occurs discreetly in the central-north of the province (termed Ribeira magma-type), whose lithospheric structure is characterized by higher P- and S- wave velocities, and high electrical resistivity. The initial 187Os/188Os isotopic compositions in Ribeira lavas, ranging from 0.10660 to 0.12575, are more unradiogenic than the other magma-types of the PCFB, as well as the estimates of the contemporary Depleted Mantle and are lower than any osmium isotopic ratio yet reported for continental flood basalts. These remarkably unradiogenic 187Os/188Os ratios preclude significant continental crust contamination and require the involvement of an ancient subcontinental lithospheric mantle source that evolved in a very low Re/Os environment. The fact that the Ribeira rocks occur on a peculiar lithospheric geophysical structure and have a unique unradiogenic osmium isotope signature reveals for the first time the existence of Archean lithosphere concealed by the Paraná Basin, inserted in the Paranapanema fragmented lithosphere. On the other hand, the other magma-types of the province, whose osmium isotopic signature is similar to the modern fertile mantle, occur close to more electrically conductive lithospheric structures. Thus, osmium isotopic information integrated with recent crustal and upper mantle geophysical soundings provides crucial information about the PCFB mantle sources. To account for the combined Os, Nd, Sr and Pb isotopic compositions of the Ribeira rocks, we propose that the primary melts formed from the heterogeneous lithospheric mantle (including Archean lithosphere fragments) that was variably hybridized by melts derived from recycling of eclogites related to multiple Neoproterozoic-Cambrian suture zones that surround the Paraná Basin and subduction processes.

Sr-Nd-Pb isotope systematics of Australasian tektites: Implications for the nature and composition of target materials and possible volatile loss of Pb

The Australasian tektite (AAT) strewn field is the largest strewn field on the Earth with about ∼10–30% coverage, both land and ocean, but a clearly identified source impact crater is absent despite the young age of AAT of ca. 790 ka. A genetic link between the Australasian tektites and their unequivocal parental materials is therefore largely impossible to establish. Nevertheless, the nature of the parental materials and the extent of volatilization can be constrained using the splash form tektites, carrying the chemical signatures of high-temperature processes, and the layered (so-called Muong Nong-type) tektites, which are less chemically homogenized and exceptionally abundant in the AAT field. New high-precision Sr, Nd and Pb isotopic measurements were obtained for a chemically and petrographically well-characterized suite of AAT, which included the Muong Nong-type (MN-AAT) with precisely known field locations in Laos and splash forms (SF-AAT) from different parts of the strewn field. In addition, optically dark and light zones of the MN-AAT were also separately analyzed. Homogeneous εNd values from −11.8 to −11.2, combined with a narrow range of two-stage Nd model ages from 1.67 to 1.72 Ga for the entire AAT suite, point to a well-mixed source, in terms of REE, of the crustal segment from which the sedimentary material for tektites was ultimately derived. The Sr isotopic data largely overlap for SF-AAT and MN-AAT (87Sr/86Sr = 0.71636–0.72021) and indicate Paleozoic to Mesozoic sedimentary parentage. However, late Neogene to early Quaternary re-deposition and formation of a thick silt-sized sedimentary section with vertical stratification is required to comply with 10Be data. Lead isotope systematics documents at least three different components which can perhaps be represented by different mineral phases, such as feldspar, zircon, organic matter adsorbed on young sediments etc., sorted during fluvial transport and final deposition. In addition, the SF-AAT have systematically lower Pb contents than the MN-AAT, and generally show isotopically heavier Pb isotopic ratios. This is theoretically consistent with a preferential volatilization of lighter Pb isotopes during evaporation and considerably larger Pb loss from SF-AAT when compared to MN-AAT. Nevertheless, further experimental work would be necessary to unambiguously distinguish kinetic fractionation from source mixing.

Fast offline data reduction of laser ablation MC-ICP-MS Sr isotope measurements via an interactive Excel-based spreadsheet ‘SrDR’

We present SrDR, an Excel-based easily accessible and interactive data reduction spreadsheet for the fast correction of Sr isotope measurements by LA-MC-ICP-MS done on different target materials and with different instruments.

Improved methodology for identification of Göktepe white marble and the understanding of its use: A comparison with Carrara marble

The provenance of marbles used for ancient statuary and architecture is of utmost importance for archaeologists, art historians and archaeometrists. The aim of this paper is to provide a comprehensive characterisation of the white marble exploited in antiquity in Göktepe (Muğla Province, Turkey) to increase the reliability for identifying this marble in ancient artefacts. A campaign of interdisciplinary archaeological and geological fieldwork undertaken by the Marmora Asiatica project is based on a multi-method approach and on a representative set of samples used for the archaeometric analyses. Petrographic investigation showed that the Göktepe marble is more variable with regard to fabrics and grain size than previously suggested, whereas it is generally non-luminescent and dolomite-free. Stable C and O isotope and elemental analyses confirmed the results reported so far. We also report, for the first time for Göktepe white marble, the results of Sr isotope measurements, which in combination with elemental ratios, e.g. Sr/Mg and Mn/Sr, and δ18O values, greatly improve the discrimination among Göktepe, Carrara and other fine-grained white marbles. Applicability of these proxies was tested on artefacts from Hadrian's Villa, for which Carrara and Goktepe provenance had been proposed. The paper also reports new archaeological findings and results of estimates of stone extracted from the quarries, which allowed for a recontextualization of the significance of quarries at Göktepe. High-resolution topographic measurements, performed for the first time with the use of a 3-D laser scanner, combined with geological field study, allowed for precise calculation of the volume of the white variety extracted in antiquity. Estimates of 17000 m3 is almost a half less than previously suggested. Moreover, a careful study of the existing literature showed that in some instances assignment of white marble artefacts to the Göktepe quarries may not be accurate. Verification of provenance for those problematic artefacts and a more reliable identification of Göktepe marbles in the future can be achieved by application of the set of analyses proposed in this work, which has a higher discrimination potential.

NanoSr – A New Carbonate Microanalytical Reference Material for In Situ Strontium Isotope Analysis

The in situ measurement of Sr isotopes in carbonates by MC‐ICP‐MS is limited by the availability of suitable microanalytical reference materials (RMs), which match the samples of interest. Whereas several well‐characterised carbonate reference materials for Sr mass fractions > 1000 µg g−1 are available, there is a lack of well‐characterised carbonate microanalytical RMs with lower Sr mass fractions. Here, we present a new synthetic carbonate nanopowder RM with a Sr mass fraction of ca. 500 µg g−1 suitable for microanalytical Sr isotope research (‘NanoSr’). NanoSr was analysed by both solution‐based and in situ techniques. Element mass fractions were determined using EPMA (Ca mass fraction), as well as laser ablation and solution ICP‐MS in different laboratories. The 87Sr/86Sr ratio was determined by well‐established bulk methods for Sr isotope measurements and is 0.70756 ± 0.00003 (2s). The Sr isotope microhomogeneity of the material was determined by LA‐MC‐ICP‐MS, which resulted in 87Sr/86Sr ratios of 0.70753 ± 0.00007 (2s) and 0.70757 ± 0.00006 (2s), respectively, in agreement with the solution data within uncertainties. Thus, this new reference material is well suited to monitor and correct microanalytical Sr isotope measurements of low‐Sr, low‐REE carbonate samples. NanoSr is available from the corresponding author.

Nucleosynthetic Sr–Nd Isotope Correlations in Chondrites: Evidence for Nebular Thermal Processing and Dust Transportation in the Early Solar System

Abstract We conducted high-precision Sr and Nd isotopic measurements in bulk chondrites using a complete sample digestion technique. Our new data indicate that enstatite and ordinary chondrites possess uniform and small, but resolvable, Sr and Nd isotopic deviations from terrestrial rocks. In contrast, the Sr isotope ratios varied across different classes of carbonaceous chondrites (CM, CO, and CV). The deviation of data from the s-process mixing line in Sr–Nd isotopic space likely resulted from the incorporation of calcium-aluminum-rich inclusions (CAIs) into carbonaceous chondrite parent bodies. Planetary-scale Sr and Nd isotopic heterogeneities among terrestrial rocks, enstatite, ordinary chondrites, and CAI-subtracted carbonaceous chondrites suggest a heterogeneous distribution of s-process-enriched materials in the early solar system, probably caused by nebular thermal processing. The observed Sr and Nd isotopic variation across the CAI-subtracted carbonaceous chondrites cannot be explained solely by nebular thermal processing, but is likely attributable to s-process-depleted silicate grains that repeatedly circulated among the early solar system. These grains were transferred and incorporated at varying degrees into the formation region of the parent bodies of individual carbonaceous chondrites.

Chemical weathering of mafic rocks in boreal subarctic environment (northwest Russia) under influence of glacial moraine deposits

Chemical weathering of mafic rocks represents substantial sink of atmospheric CO2 yet the mechanismes of this process in high-latitude regions are poorly understood. This work addresses geochemical migration and partitioning of major and trace elements between rock, soil and surface waters during chemical weathering of mafic rocks and soil formation under the influence of a glacial moraine in the northwestern Russian subarctic. We used multidisciplinary approach which included major and trace element chemical analysis, Sr isotopic measurements, and mineralogical structural and microscopic investigations. Quaternary (Pleistocene) deposits were observed even in the deepest horizons of soil profiles and confirm a strong moraine influence as most soils showed podzolic features. Chemical and Sr isotopic analyses revealed a strong impact of the moraine on soil chemistry and mineralogy. Mineralogical studies showed the presence of non-aeolian quartz and zircon in soils which were not linked to the nature of the parental rocks (i.e. mafic and felsic). At the same time, we observed the presence of etch pit corrosion on the surface of zircons and feldspars, and a newly-formed matter adjacent to the surface of primary phases. The chemical index of alteration (CIA) showed weak or no weathering of rocks within the soil profile and the weathering intensity scale confirmed the “felsic” chemical composition of soils developed over mafic and ultramafic rocks. Analysis of Sr radiogenic isotopes demonstrated preferential removal of easily weatherable and less radiogenic minerals over the full depth of soil profile and a more radiogenic signature of the granitic moraine compared to mafic and felsic bedrocks. The composition of most surface waters reflected the weathering of silicate rocks but did not allow for distinguishing purely mafic source. The chemical weathering rates of ultramafic rocks were calculated to be higher than those for the granitic till, but the moraine depositions which dominate this region hide evidence of the real weathering process. This could be due to retention of Mg and Ca in soil due to precipitation of secondary phases such as Mg-vermiculite or divalent cation adsorption on mineral, organic or organo-mineral phases. As a result, weathering rates estimated for the olivinite rock appear to be lower than the weathering rates of mafic rocks reported in other boreal and subarctic regions. Overall, the felsic moraine deposits are capable to sizably decrease the weathering intensity of mafic rocks which should be taken into account for chemical weathering modelling of high-latitude regions subjected to glaciation in the past.

High-Precision In Situ 87Sr/86Sr Analyses through Microsampling on Solid Samples: Applications to Earth and Life Sciences.

An analytical protocol for high-precision, in situ microscale isotopic investigations is presented here, which combines the use of a high-performing mechanical microsampling device and high-precision TIMS measurements on micro-Sr samples, allowing for excellent results both in accuracy and precision. The present paper is a detailed methodological description of the whole analytical procedure from sampling to elemental purification and Sr-isotope measurements. The method offers the potential to attain isotope data at the microscale on a wide range of solid materials with the use of minimally invasive sampling. In addition, we present three significant case studies for geological and life sciences, as examples of the various applications of microscale 87Sr/86Sr isotope ratios, concerning (i) the pre-eruptive mechanisms triggering recent eruptions at Nisyros volcano (Greece), (ii) the dynamics involved with the initial magma ascent during Eyjafjallajökull volcano's (Iceland) 2010 eruption, which are usually related to the precursory signals of the eruption, and (iii) the environmental context of a MIS 3 cave bear, Ursus spelaeus. The studied cases show the robustness of the methods, which can be also be applied in other areas, such as cultural heritage, archaeology, petrology, and forensic sciences.