Assessment of Nanosecond Laser Ablation Multi‐Collector Inductively Coupled Plasma‐Mass Spectrometry for Pb and Sr Isotopic Determination in Archaeological Glass: Mass Bias Correction Strategies and Results for Corning Glass Reference Materials

This work presents an evaluation of various methods for in situ high‐precision Sr and Pb isotopic determination in archaeological glass (containing 100–500 μg g^?1 target element) by nanosecond laser ablation multi‐collector‐inductively coupled plasma‐mass spectrometry (ns‐LA‐MC‐ICP‐MS). A set of four soda‐lime silicate glasses, Corning A–D, mimicking the composition of archaeological glass and produced by the Corning Museum of Glass (Corning, New York, USA), were investigated as candidates for matrix‐matched reference materials for use in the analysis of archaeological glass. Common geological reference materials with known isotopic compositions (USGS basalt glasses BHVO‐2G, GSE‐1G and NKT‐1G, soda‐lime silicate glass NIST SRM 610 and several archaeological glass samples with known Sr isotopic composition) were used to evaluate the ns‐LA‐MC‐ICP‐MS analytical procedures. When available, ns‐LA‐MC‐ICP‐MS results for the Corning glasses are reported. These were found to be in good agreement with results obtained via pneumatic nebulisation (pn) MC‐ICP‐MS after digestion of the glass matrix and target element isolation. The presence of potential spectral interference from doubly charged rare earth element (REE) ions affecting Sr isotopic determination was investigated by admixing Er and Yb aerosols by means of pneumatic nebulisation into the gas flow from the laser ablation system. It was shown that doubly charged REE ions affect the Sr isotope ratios, but that this could be circumvented by operating the instrument at higher mass resolution. Multiple strategies to correct for instrumental mass discrimination in ns‐LA‐MC‐ICP‐MS and the effects of relevant interferences were evaluated. Application of common glass reference materials with basaltic matrices for correction of ns‐LA‐MC‐ICP‐MS isotope data of archaeological glasses results in inaccurate Pb isotope ratios, rendering application of matrix‐matched reference materials indispensable. Correction for instrumental mass discrimination using the exponential law, with the application of Tl as an internal isotopic standard element introduced by pneumatic nebulisation and Corning D as bracketing isotopic calibrator, provided the most accurate results for Pb isotope ratio measurements in archaeological glass. Mass bias correction relying on the power law, combined with intra‐element internal correction, assuming a constant ⁸⁸Sr/⁸⁶Sr ratio, yielded the most accurate results for ⁸⁷Sr/⁸⁶Sr determination in archaeological glasses     

An assessment of solubility profiling as a decontamination procedure for the 87Sr/86Sr analysis of archaeological human skeletal tissue

⁸⁷Sr/⁸⁶Sr of archaeological skeletal tissues are increasingly used to reconstruct residential mobility and migration, but the post mortem preservation of biogenic Sr is often uncertain. Sample pre-treatment regimes, notably ‘solubility profiling’, have been used to remove diagenetic Sr prior to analysis, but doubts remain over their effectiveness. The investigation examines the effectiveness of solubility profiling by comparing the Sr content and ⁸⁷Sr/⁸⁶Sr composition of bone, dentine and enamel from two archaeological juveniles (Blackfriars, UK) before and after attempted decontamination. For both individuals leached samples of cortical bone and dentine had similar ⁸⁷Sr/⁸⁶Sr to those of soil leachates from the burial site, and are therefore thought to represent diagenetic ⁸⁷Sr/⁸⁶Sr. For both individuals samples of treated dental enamel have ⁸⁷Sr/⁸⁶Sr considerably more or less radiogenic than the soil leachates and other tissues. These are considered representative of biogenic Sr, i.e. Sr acquired in vivo. In effect, solubility profiling should have resulted in ⁸⁷Sr/⁸⁶Sr that were similar for all 3 tissues types and close to those of the untreated enamel. Experimental results show that tooth enamel ⁸⁷Sr/⁸⁶Sr remained largely unaffected by solubility profiling, and the process did not significantly alter the final ⁸⁷Sr/⁸⁶Sr of either dentine or cortical bone. It is concluded that the technique was ineffective in facilitating the recovery of biogenic Sr from these tissues.     

The geographic distribution of strontium isotopes in Danish surface waters - A base for provenance studies in archaeology, hydrology and agriculture

In this paper Sr isotope signatures are reported for 192 surface water (lakes/ponds and rivers/creeks) samples from within Denmark and an isotope distribution map is presented that may serve as a base for provenance applications, including archaeological migration studies, ground water - surface water - seawater interaction/contamination monitoring, and potentially for agricultural applications, including cases of authenticity proof for particular food products. The Sr isotopic compositions of surface waters range from ⁸⁷Sr/⁸⁶Sr = 0.7078 to 0.7125 (average 0.7096 ± 0.0016; 2σ). This average value lies above the range of ⁸⁷Sr/⁸⁶Sr values between 0.7078 and 0.7082 expected from Late Cretaceous to Early Tertiary (Oligocene) limestones which form the dominant bedrock type in a NW-SE trending belt in Denmark. The elevated ⁸⁷Sr/⁸⁶Sr signatures >∼0.7095 are explained by additions to the surface waters of radiogenic Sr predominantly derived from the near-surface weathering and wash-out of Quarternary glaciogenic tills and soils deposited and formed during and after the last two ice age stages (Saale and Weichsel). The Sr isotopic compositions and concentrations of the surface waters can, therefore, best be modeled by a two-component mixing involving carbonaceous bedrock and glaciogenic cover sediments as the two predominant Sr sources. A feasibility study for using Sr isotopic compositions of surface waters as a proxy for bio-available Sr signatures was conducted in a representative test area on Zealand (Land of Legends, Lejre) where there is no use and application of commercial fertilizers. It is demonstrated that the Sr isotopic signatures of lake waters from within this area are slightly higher (but statistically still indistinguishable) from the average value defined by snail shells and soil leachates considered to characterize the true bio-available Sr. In combination with results from other studies, this is interpreted to reflect the wash-out of Sr with a higher ⁸⁷Sr/⁸⁶Sr signature released by weathering in the topsoils into the saturated water tables, a component which is consequently not readily transferred into the shallow-rooting plants and into small herbivores feeding on them. Since drinking water is a likely important source of Sr uptake of humans and larger animals, the contention is that a surface water isotopic composition can potentially characterize the bio-available component relevant for human and carnivorous large animals. Spline functions and ordinary linear kriging were used for modeling the geographic distribution of bio-available Sr isotopes over territorial Denmark. As expected, based on the two-source mixing scenario, the water ⁸⁷Sr/⁸⁶Sr ratio contour maps (with some notable exceptions) neither mirror the pre-Quarternary bedrock geology nor a (Pleistocene) soil-type distribution map of Denmark.As a conservative suggestion, the use of the average ⁸⁷Sr/⁸⁶Sr ratio of 0.7096 ± 0.0015 (2σ) is recommended as an average for bio-available Sr from within Denmark (Bornholm excluded) for human and larger animals and as a confidence band for distinguishing “local” from “non-local” signatures in archaeological provenance studies. The study also reveals that the average ⁸⁷Sr/⁸⁶Sr ratio of ∼0.7088 defined from soil extracts and small herbivores lies approximately 0.15% lower than that defined by the surface waters. The authors recommend using this lower value as a “local”-“non-local” discriminator for food and plant authenticity control in agricultural applications.     

In situ Sr/Sr investigation of igneous apatites and carbonates using laser-ablation MC-ICP-MS

In situ Sr isotopic compositions of coexisting apatite and carbonate for carbonatites from the Sarfartoq alkaline complex, Greenland, have been determined by laser-ablation multicollector inductively coupled plasma mass spectrometry. This study is the first to examine the extent of Sr isotopic homogeneity among coexisting igneous minerals containing high Sr (>3000 ppm) and low Rb (?1 ppm) contents within a single ∼50-μm-thick thin-section mount. This technique is capable of producing measured ⁸⁷Sr/⁸⁶Sr values with analytical precision (∼0.005%, 2σ) approaching those obtained by thermal ionization mass spectrometry but in a much shorter interval of time (100 s vs. >1 h, respectively). The combined total analyses (n = 107) of apatite and carbonate yield ⁸⁷Sr/⁸⁶Sr compositions ranging from ∼0.7025 to ∼0.7031. This relatively large variation in Sr isotopic compositions (∼0.0006) is ∼1 order of magnitude larger than the estimated external reproducibility (∼0.00005, 2σ) of the method. The large range in ⁸⁷Sr/⁸⁶Sr values suggests that apatite and carbonate precipitated predominantly under nonequilibrium conditions. The isotopic variations observed within individual hand specimens may therefore reflect larger (regional) scale open-system processes, possibly involving mixing of carbonatitic melts derived from distinct mantle sources or from a common isotopically heterogeneous mantle.     

Isotopic tracers of paleohydrologic change in large lakes of the Bolivian Altiplano

We have developed an ⁸⁷Sr/⁸⁶Sr, ²³⁴U/²³⁸U, and δ¹⁸O data set from carbonates associated with late Quaternary paleolake cycles on the southern Bolivian Altiplano as a tool for tracking and understanding the causes of lake-level fluctuations. Distinctive groupings of ⁸⁷Sr/⁸⁶Sr ratios are observed. Ratios are highest for the Ouki lake cycle (120-95 ka) at 0.70932, lowest for Coipasa lake cycle (12.8-11.4 ka) at 0.70853, and intermediate at 0.70881 to 0.70884 for the Salinas (95-80 ka), Inca Huasi (~ 45 ka), Sajsi (24-20.5 ka), and Tauca (18.1-14.1 ka) lake cycles. These Sr ratios reflect variable contributions from the eastern and western Cordilleras. The Laca hydrologic divide exerts a primary influence on modern and paleolake ⁸⁷Sr/⁸⁶Sr ratios; waters show higher ⁸⁷Sr/⁸⁶Sr ratios north of this divide. Most lake cycles were sustained by slightly more rainfall north of this divide but with minimal input from Lake Titicaca. The Coipasa lake cycle appears to have been sustained mainly by rainfall south of this divide. In contrast, the Ouki lake cycle was an expansive lake, deepest in the northern (Poópo) basin, and spilling southward. These results indicate that regional variability in central Andean wet events can be reconstructed using geochemical patterns from this lake system.     

Strontium isotope geochemistry of groundwater affected by human activities in Nandong underground river system, China

The Nandong Underground River System (NURS) is located in a typical karst area dominated by agriculture in SE Yunnan Province, China. Groundwater plays an important role in the social and economical development in the area. The effects of human activities (agriculture and sewage effluents) on the Sr isotope geochemistry were investigated in the NURS. Seventy-two representative groundwater samples, which were collected from different aquifers (calcite and dolomite), under varying land-use types, both in summer and winter, showed significant spatial differences and slight seasonal variations in Sr concentrations and ⁸⁷Sr/⁸⁶Sr ratios. Agricultural fertilizers and sewage effluents significantly modified the natural ⁸⁷Sr/⁸⁶Sr ratios signature of groundwater that was otherwise dominated by water-rock interaction. Three major sources of Sr could be distinguished by ⁸⁷Sr/⁸⁶Sr ratios and Sr concentrations in karst groundwater. Two sources of Sr are the Triassic calcite and dolomite aquifers, where waters have low Sr concentrations (0.1-0.2 mg/L) and low ⁸⁷Sr/⁸⁶Sr ratios (0.7075-0.7080 and 0.7080-0.7100, respectively); the third source is anthropogenic Sr from agricultural fertilizers and sewage effluents with waters affected having radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.7080-0.8352 for agricultural fertilizers and 0.7080-0.7200 for sewage effluents, respectively), with higher Sr concentrations (0.24-0.51 mg/L). Due to the overlapping ⁸⁷Sr/⁸⁶Sr ratios, it is difficult to distinguish the sources of Sr in groundwater samples contaminated by agricultural fertilizers or sewage effluents based only on their ⁸⁷Sr/⁸⁶Sr ratios. However, ⁸⁷Sr/⁸⁶Sr ratios do provide key information for natural and anthropogenic sources in karst groundwater.     

Resolving archaeological populations with Sr-isotope mixing models

Strontium isotope analysis of tooth enamel is a useful provenancing technique to investigate the childhood origins and residential mobility of ancient people. However, where different geographical target regions have similar biosphere ⁸⁷Sr/⁸⁶Sr it is often difficult to resolve the ⁸⁷Sr/⁸⁶Sr ranges of two different groups of people and establish what constitutes the local range at each site. Here a multi-period study is presented from the Outer Hebrides, Scotland and an investigation of Neolithic and Early Bronze Age populations from the Yorkshire Wolds, NE England. The aim is to demonstrate that, despite complex human dietary strategies, simple mixing systems with only two end-members do occur in archaeological human populations in certain geological provinces and, despite overlapping ⁸⁷Sr/⁸⁶Sr ranges, it is possible to separate two populations based on the structure within the data set.     

Constraining the marine strontium budget with natural strontium isotope fractionations (Sr/Sr∗, δSr) of carbonates, hydrothermal solutions and river waters

We present strontium (Sr) isotope ratios that, unlike traditional ⁸⁷Sr/⁸⁶Sr data, are not normalized to a fixed ⁸⁸Sr/⁸⁶Sr ratio of 8.375209 (defined as δ^88/86Sr = 0 relative to NIST SRM 987). Instead, we correct for isotope fractionation during mass spectrometry with a ⁸⁷Sr-⁸⁴Sr double spike. This technique yields two independent ratios for ⁸⁷Sr/⁸⁶Sr and ⁸⁸Sr/⁸⁶Sr that are reported as (⁸⁷Sr/⁸⁶Sr∗) and (δ^88/86Sr), respectively. The difference between the traditional radiogenic (⁸⁷Sr/⁸⁶Sr normalized to ⁸⁸Sr/⁸⁶Sr = 8.375209) and the new ⁸⁷Sr/⁸⁶Sr∗ values reflect natural mass-dependent isotope fractionation. In order to constrain glacial/interglacial changes in the marine Sr budget we compare the isotope composition of modern seawater ((⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_Seawater) and modern marine biogenic carbonates ((⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_Carbonates) with the corresponding values of river waters ((⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_River) and hydrothermal solutions ((⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_HydEnd) in a triple isotope plot. The measured (⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_River values of selected rivers that together account for ∼18% of the global Sr discharge yield a Sr flux-weighted mean of (0.7114(8), 0.315(8)‰). The average (⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_HydEnd values for hydrothermal solutions from the Atlantic Ocean are (0.7045(5), 0.27(3)‰). In contrast, the (⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_Carbonates values representing the marine Sr output are (0.70926(2), 0.21(2)‰). We estimate the modern Sr isotope composition of the sources at (0.7106(8), 0.310(8)‰). The difference between the estimated (⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_input and (⁸⁷Sr/⁸⁶Sr∗, δ^88/86Sr)_output values reflects isotope disequilibrium with respect to Sr inputs and outputs. In contrast to the modern ocean, isotope equilibrium between inputs and outputs during the last glacial maximum (10-30 ka before present) can be explained by invoking three times higher Sr inputs from a uniquely “glacial” source: weathering of shelf carbonates exposed at low sea levels. Our data are also consistent with the “weathering peak” hypothesis that invokes enhanced Sr inputs resulting from weathering of post-glacial exposure of abundant fine-grained material.     

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.     

87Sr/86Sr isotope composition of bottled British mineral waters for environmental and forensic purposes

Mineral waters in Britain show a wide range of ⁸⁷Sr/⁸⁶Sr isotope compositions ranging between ⁸⁷Sr/⁸⁶Sr = 0.7059 from Carboniferous volcanic rock sources in Dunbartonshire, Scotland to ⁸⁷Sr/⁸⁶Sr = 0.7207 in the Dalradian aquifer of Aberdeenshire, Scotland. The ⁸⁷Sr/⁸⁶Sr composition of the waters shows a general correlation with the aquifer rocks, resulting in the waters from older rocks having a more radiogenic signature than those from younger rocks. This wide range of values means that the Sr isotope composition of mineral water has applications in a number of types of studies. In the modern commercial context, it provides a way of fingerprinting the various mineral waters and hence provides a method for recognising and reducing fraud. From an environmental perspective, it provides the first spatial distribution of bio-available ⁸⁷Sr/⁸⁶Sr in Britain that can be used in modern, historical and archaeological studies.     

Extreme variations in strontium initial ratios in ore-related fluids

Magmato-hydrothermal cassiterite-topaz ore at the Carboniferous East Kemptville (EK) greisenhosted tin deposit (Nova Scotia, Canada) is cross-cut by veins containing apatite, triplite, vivianite and fluorite. Initial ⁸⁷Sr/⁸⁶Sr ratios of these minerals have an extreme range (0.7135 to 0.8284). The initial ratios of the host rocks, EK quartz-topaz rock and Davis Lake biotite monzogranite (0.729±0.001, 0.727±0.004), are also high. The adjacent Meguma Group metasedimentary rocks are more typical of crustal material (0.712–0.719 at 330 Ma). Rb and Sr contents of EK fluorite (max.: 13.0, 1420 ppm) and apatite (max.: 88.1, 6660 ppm) are unusually high and variable. Unexpectedly, high Sr contents correlate positively with the high initial ⁸⁷Sr/⁸⁶Sr ratios. Fluorite and phosphate minerals from the first set of post-greisen veins at East Kemptville reflect the unusual chemistry of a high ⁸⁷Sr/⁸⁶Sr fluid present in the deposit after ore formation. The most extreme composition of this fluid was characterized by ⁸⁷Sr/⁸⁶Sr>0.8284, high Rb/Sr, high P, Rb, Cu, Zn and Fe contents, but low abundances of Ca, Pb and Sn with respect to the Davis Lake monzogranite. Such a fluid could have been derived from the greisen fluid and modified by reaction with the overlying Meguma metawacke. A second alternative, which cannot be well constrained at present, is that an extremely radiogenic fluid entered the deposit after ore formation and mixed with the postore fluid. In either case, the modified fluid subsequently mixed with meteoric water and precipitated the minerals with much lower ⁸⁷Sr/⁸⁶Sr ratios and Rb and Sr contents.     

Matrix-independent Fe isotope ratio determination in silicates using UV femtosecond laser ablation

UV femtosecond laser ablation coupled to MC-ICP-MS provides a promising in situ tool to investigate elemental and isotope ratios by non-matrix-matched calibration. In this study, we investigate Fe isotope composition in siliceous matrices including biotite, hornblende, garnet, fayalite and forsterite (San Carlos Olivine), and an oceanic Fe–Mn crust using the iron reference material IRMM-014 for calibration. To test the accuracy of the laser ablation data, Fe isotope compositions were obtained independently by solution ICP-MS after chromatographic separation of Fe. Sample materials with low Cr content, i.e. biotite, hornblende, fayalite and the Fe–Mn crust, reveal δ^56/54Fe and δ^57/54Fe values that agree with those from solution ICP-MS data within the measured precision. For high Cr concentration (⁵⁴Cr/⁵⁴Fe >0.0001), i.e. in the garnet and forsterite sample, δ^56/54Fe and δ^57/54Fe values were derived from ⁵⁷Fe/⁵⁶Fe ratios as correction of the isobaric interference of ⁵⁴Cr on ⁵⁴Fe is unsatisfactory. This approach provides accurate results for both minerals. Moreover, the garnet crystal exhibits isotopic zonation with differences of 0.3‰ in δ^56/54Fe showing that substantial heterogeneities exist in high-temperature metamorphic minerals. Multiple analyses of homogeneous sample materials reveal a repeatability of 0.1‰ (2 SD) for δ^56/54Fe and 0.2‰ (2 SD) for δ^57/54Fe, respectively. This study adds to the observations of Horn et al. (2006) who have shown that the determination of Fe isotope ratios in various matrices including iron alloys, iron oxides and hydroxides, iron sulfide and iron carbonates can be performed with high accuracy and precision at high spatial resolution using UV femtosecond laser ablation ICP-MS. These results demonstrate that femtosecond laser ablation ICP-MS is a largely matrix-independent method, which provides a substantial advantage over commonly employed nanosecond laser ablation systems.     

Reconstructing the migration patterns of late Pleistocene mammals from northern Florida, USA

We used analyses of the strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low ⁸⁷Sr/⁸⁶Sr ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of ⁸⁷Sr/⁸⁶Sr ratios. Some individuals in each taxon displayed low ⁸⁷Sr/⁸⁶Sr ratios that suggest they ranged locally, while other animals had high ⁸⁷Sr/⁸⁶Sr ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower ⁸⁷Sr/⁸⁶Sr ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns.     

Strontium isotope systematics of mixing groundwater and oil-field brine at Goose Lake in northeastern Montana,USA

Groundwater, surface water, and soil in the Goose Lake oil field in northeastern Montana have been affected by Cl⁻-rich oil-field brines during long-term petroleum production. Ongoing multidisciplinary geochemical and geophysical studies have identified the degree and local extent of interaction between brine and groundwater. Fourteen samples representing groundwater, surface water, and brine were collected for Sr isotope analyses to evaluate the usefulness of ⁸⁷Sr/⁸⁶Sr in detecting small amounts of brine. Differences in Sr concentrations and ⁸⁷Sr/⁸⁶Sr are optimal at this site for the experiment. Strontium concentrations range from 0.13 to 36.9 mg/L, and corresponding ⁸⁷Sr/⁸⁶Sr values range from 0.71097 to 0.70828. The local brine has 168 mg/L Sr and a ⁸⁷Sr/⁸⁶Sr value of 0.70802. Mixing relationships are evident in the data set and illustrate the sensitivity of Sr in detecting small amounts of brine in groundwater. The location of data points on a Sr isotope-concentration plot is readily explained by an evaporation-mixing model. The model is supported by the variation in concentrations of most of the other solutes.     

Search for the proverbial mantle osmium sources to the oceans: Hydrothermal alteration of mid-ocean ridge basalt

We present Os and Sr isotopes and Mg, Os, and Sr concentrations for ridge-crest high-temperature and diffuse hydrothermal fluids, plume fluids and ridge-flank warm spring fluids from the Juan de Fuca Ridge. The data are used to evaluate the extent to which (1) the high- and low-temperature hydrothermal alteration of mid-ocean ridge basalts (MORBs) provides Os to the deep oceans, and (2) hydrothermal contributions of non-radiogenic Os and Sr to the oceans are coupled. The Os and Sr isotopic ratios of the high-temperature fluids (265-353 °C) are dominated by basalts (¹⁸⁷Os/¹⁸⁸Os = 0.2; ⁸⁷Sr/⁸⁶Sr = 0.704) but the concentrations of these elements are buffered approximately at their seawater values. The ¹⁸⁷Os/¹⁸⁸Os of the hydrothermal plume fluids collected ∼1 m above the orifice of Hulk vent is close to the seawater value (=1.05). The low-temperature diffuse fluids (10-40 °C) associated with ridge-crest high-temperature hydrothermal systems on average have [Os] = 31 fmol kg⁻¹, ¹⁸⁷Os/¹⁸⁸Os = 0.9 and [Sr] = 86 μmol kg⁻¹, ⁸⁷Sr/⁸⁶Sr = 0.709. They appear to result from mixing of a high-temperature fluid and a seawater component. The ridge-flank warm spring fluids (10-62 °C) on average yield [Os] = 22 fmol kg⁻¹, ¹⁸⁷Os/¹⁸⁸Os = 0.8 and [Sr] = 115 μmol kg⁻¹, ⁸⁷Sr/⁸⁶Sr = 0.708. The data are consistent with isotopic exchange of Os and Sr between basalt and circulating seawater during low-temperature hydrothermal alteration. The average Sr concentration in these fluids appears to be similar to seawater and consistent with previous studies. In comparison, the average Os concentration is less than seawater by more than a factor of two. If these data are representative they indicate that low-temperature alteration of MORB does not provide adequate non-radiogenic Os and that another source of mantle Os to the oceans must be investigated. At present, the magnitude of non-radiogenic Sr contribution via low-temperature seawater alteration is not well constrained. If non-radiogenic Sr to the oceans is predominantly from the alteration of MORB, our data suggest that there must be a different source of non-radiogenic Os and that the Os and Sr isotope systems in the oceans are decoupled.     

Input of Sr/Sr ratios and Sr geochemical signatures to update knowledge on thermal and mineral waters flow paths in fractured rocks (N-Portugal)

Strontium isotopes and other geochemical signatures are used to determine the relationships between CO₂-rich thermal (Chaves: 76 °C) and mineral (Vilarelho da Raia, Vidago and Pedras Salgadas: 17 °C) waters discharging along one of the major NNE–SSW trending faults in the northern part of mainland Portugal. The regional geology consists of Hercynian granites (syn-tectonic-310 Ma and post-tectonic-290 Ma) intruding Silurian metasediments (quartzites, phyllites and carbonaceous slates). Thermal and mineral waters have ⁸⁷Sr/⁸⁶Sr isotopic ratios between 0.716713 and 0.728035. ⁸⁷Sr/⁸⁶Sr vs. 1/Sr define three end-members (Vilarelho da Raia/Chaves, Vidago and Pedras Salgadas thermal and mineral waters) trending from rainfall composition towards that of the CO₂-rich thermal and mineral waters, indicating different underground flow paths. Local granitic rocks have ⁸⁷Sr/⁸⁶Sr ratios of 0.735697–0.789683. There is no indication that equilibrium was reached between the CO₂-rich thermal and mineral waters and the granitic rocks. The mean ⁸⁷Sr/⁸⁶Sr ratio of the thermal and mineral waters (0.722419) is similar to the Sr isotopic ratios of the plagioclases of the granitic rocks (0.71261–0.72087). The spatial distribution of Sr isotope and geochemical signatures of waters and the host rocks suggests that the thermal and mineral waters circulate in similar but not the same hydrogeological system. Results from this study could be used to evaluate the applicability of this isotope approach in other hydrogeologic investigations.     

The geographic distribution of Sr isotopes from surface waters and soil extracts over the island of Bornholm (Denmark) – A base for provenance studies in archaeology and agriculture

In this paper we report the Sr isotope signatures, and Sr, Al and Na concentrations of 30 surface waters (lakes/ponds and rivers/creeks) and 19 soil sample extracts from the island of Bornholm (Denmark) and present a categorized ⁸⁷Sr/⁸⁶Sr value distribution map that may serve as a base for provenance studies, including archaeological migration and authenticity proof for particular food products. The Sr isotopic compositions of surface waters range from ⁸⁷Sr/⁸⁶Sr = 0.7097–0.7281 (average 0.7175 ± 0.0049; 1σ), whereas 0.1 M HNO₃, 0.05 M HNO₃, and 0.01 M CaCl₂ soil extracts range from ⁸⁷Sr/⁸⁶Sr = 0.7095–0.7197 and define somewhat lower but statistically indistinguishable averages of 0.7125 ± 0.003 (1s). These compositions are lower than the values expected from the Precambrian granitoid basement (⁸⁷Sr/⁸⁶Sr = 0.758–0.944), and from the overlying, mainly clastic Paleozoic sediments. Combined Sr isotope composition vs. Sr, Na and Al concentration relationships of soil extracts imply that lowering of the isotopic composition of leachable Sr on Bornholm results as a consequence of significant admixture to this fraction of Sr deposited as marine salts (aerosols), and that rainwater only has a minor influence on the Sr budget of the surface waters. Positively correlated Al/Na and [1/Sr] vs. ⁸⁷Sr/⁸⁶Sr relationships in soil extracts and surface waters indicate that the surface run-off on Bornholm is characterized by two predominant sources, namely marine aerosols (sea salts) with high Sr and low ⁸⁷Sr/⁸⁶Sr values, and a source with lower [Sr] delivering radiogenic Sr to the surface waters, which we equate with Sr leached from the products of mineral weathering (soils).A feasibility study for using Sr isotopic compositions of surface waters and soil extracts as a proxy for bioavailable Sr signatures was performed with a few samples collected in the vicinity of the eleventh century AD Ndr. Grødbygård cemetery site in SW Bornholm, from where Sr isotope compositions of modern fauna samples and tooth enamel of humans buried in the cemetery have been reported. Waters and soil extracts studied herein from around this site range from ⁸⁷Sr/⁸⁶Sr = 0.7104–0.7166 and correspond to Sr compositions extracted from snail shells in this area which span a range of ⁸⁷Sr/⁸⁶Sr = 0.7095–0.7160. Some human tooth enamel is characterized by more radiogenic values (⁸⁷Sr/⁸⁶Sr up to 0.718) which points to a possible provenance of these humans from the granite–gneiss terrain in the north of the island and/or to immigration of these humans in their childhood from other places (for example from mainland Sweden) to Bornholm. If the total compositional range of ⁸⁷Sr/⁸⁶Sr = 0.709–0.718 (n = 44) recorded in human enamel from the Ndr. Grødbygård site is considered representative for the variation of bioavailable Sr on Bornholm, then our soil leachate and surface water data entirely covers this range. We therefore propose that the combination of Sr isotope analyses of surface waters and soil leachates are an easy, fast and relatively cost efficient way to characterize a local bioavailable ⁸⁷Sr/⁸⁶Sr signature, and consequently propose that the overall average of ⁸⁷Sr/⁸⁶Sr = 0.7153 ± 0.0048 (1σ; n = 50) can be taken as a band for bioavailable Sr fractions suitable to discriminate between local and non-local signatures in provenance studies in the field of archaeology and for food and plant authenticity control in agricultural applications.     

山西省襄汾县陶寺遗址出土动物牙釉质的锶同位素比值分析

锶同位素分析技术已经成为国际考古学界用于探索人和动物迁移活动的主要方法.陶寺遗址位于山西省襄汾县陶寺镇,距今4500～3900年,是目前我国规模最大的、显现文明化程度最高的史前聚落遗址之一.文章通过热电离质谱分析方法对山西襄汾县陶寺镇陶寺遗址龙山晚期出土动物的14个动物牙釉质的锶同位素比值进行了测定.研究结果表明,5个...     

Analysis of coupled Sr/Ca and Sr/Sr variations in enamel using laser-ablation tandem quadrupole-multicollector ICPMS

We present in this study results obtained with a laser-ablation coupled with both a quadrupole and a multi-collector ICPMS. The simultaneous in situ Sr/Ca and ⁸⁷Sr/⁸⁶Sr measurements along growth profiles in enamel allows the concomitant diet and migration patterns in mammals to be reconstructed. Aliquots of the powdered international standard NIST “SRM1400 Bone Ash” with certified Sr and Ca contents, was sintered at high pressure and temperature and was adopted as the reference material for external reproducibility and calibration of the results. A total of 145 coupled elemental and isotopic measurements of herbivores enamel from the Kruger National Park, South Africa, gives intra-tooth Sr/Ca and ⁸⁷Sr/⁸⁶Sr variations that are well larger than external reproducibility. Sr/Ca profiles systematically decrease from the dentine-enamel junction to the outer enamel whereas ⁸⁷Sr/⁸⁶Sr profiles exhibit variable patterns. Using a simple geometric model of hypsodont teeth growth, we demonstrate that a continuous recording of the ⁸⁷Sr/⁸⁶Sr variations can be reconstructed in the tooth length axis. This suggests that the mobility of a mammal can be reconstructed over a period of more than a year with a resolution of a ten of days, by sampling enamel along growth profiles. Our geometric model of hypsodont teeth growth predicts that an optimal distance between two successive profiles is equal to the enamel thickness. However, this model does not apply to the Sr/Ca signal which is likely to be altered during the enamel maturation stage due to differential maturation processes along enamel thickness. Here, the observed constant decreases of the Sr/Ca ratios in the ungulates of Kruger National Park suggests that they did not changed of diet, while some of them were migrating.     

Sr and Nd isotope data of apatite,calcite and dolomite as indicators of source,and the relationships of phoscorites and carbonatites from the Kovdor massif,Kola peninsula,Russia

A detailed Sr−Nd isotopic study of primary apatite, calcite and dolomite from phoscorites and carbonatites of the Kovdor massif (380 Ma), Kola peninsula, Russia, reveals a complicated evolutionary history. At least six types of phoscorites and five types of carbonatite have been identified from Kovdor by previous investigators based on relative ages and their major and accessory minerals. Isotopic data from apatite define at least two distinct groups of phoscorite and carbonatite. Apatite from the earlier phoscorites and carbonatites (group 1) are characterized by relatively low⁸⁷Sr/⁸⁶Sr (0.70330–0.70349) and¹⁴³Nd/¹⁴⁴Nd initial ratios (0.51230–0.51240) with F=2.01–2.23 wt%, Sr=2185–2975 ppm, Nd=275–660 ppm and Sm=31.7–96.2 ppm. Apatite from the second group has higher⁸⁷Sr/⁸⁶Sr (0.70350–0.70363) and¹⁴³Nd/¹⁴⁴Nd initial ratios (0.51240–0.51247) and higher F (2.63–3.16 wt%), Sr (4790–7500 ppm), Nd (457–1074 ppm) and Sm (68.7–147.6 ppm) contents. This group corresponds to the later phoscorites and carbonatites. One apatite sample from a carbonatite from the earlier group fits into neither of the two groups and is characterized by the highest initial⁸⁷Sr/⁸⁶Sr (0.70385) and lowest¹⁴³Nd/¹⁴⁴Nd (0.51229) of any of the apatites. Within both groups initial⁸⁷Sr/⁸⁶Sr and¹⁴³Nd/¹⁴⁴Nd ratios show negative correlations. Strontium isotope data from coexisting calcite and dolomite support the findings from the apatite study. The Sr and Nd isotopic similarities between carbonatites and phoscorites indicate a genetic relationship between the two rock types. Wide variations in Sr and Nd isotopic composition within some of the earlier carbonatites indicate several distinct intrusive phases. Oxygen isotopic data from calcite and dolomite (δ¹⁸O=+7.2 to +7.7‰ SMOW) indicate the absence of any low-temerature secondary processes in phoscorites and carbonatites, and are consistent with a mantle origin for their parental melts. Apatite data from both groups of phoscorite plot in the depleted quadrant of an ε_Nd versus ε_Sr diagram. Data for the earlier group lie along the Kola Carbonatite Line (KCL) as defined by Kramm (1993) and data from the later group plot above the KCL. The evolution of the phoscorites and carbonatites cannot be explained by simple magmatic differentiation assuming closed system conditions. The Sr−Nd data can best be explained by the mixing of three components. Two of these are similar to the end-members that define the Kola Carbonatite Line and these were involved in the genesis of the early phoscorites and carbonatites. An additional component is needed to explain the isotopic characteristics of the later group. Our study shows that apatite from rocks of different mineralogy and age is ideal for placing constraints on mantle sources and for monitoring the Sr−Nd evolution of carbonatites. Editorial responsibility: W. Schreyer