Isotopic Composition Of Lithium Research Articles

Development of Synthetic Clinopyroxene Reference Materials for In Situ Lithium Isotope Measurement by LA‐MC‐ICP‐MS

The isotopic composition of lithium (Li) in clinopyroxene (Cpx), determined via in situ micro‐analysis, has been employed as a potential geochemical tool for studying various geological processes such as crust‐mantle recycling, silicate weathering and fluid‐rock interaction. To obtain precise and accurate Li isotopic compositions in Cpx by LA‐MC‐ICP‐MS, synthetic Cpx matrix‐matched reference materials (RMs) were prepared in this study. Six Cpx‐matrix RMs were prepared by mixing metallic oxides with GSP‐2 (granodiorite) or pure L‐SVEC solution and melting them into glasses (GSP‐2 + oxide; L‐SVEC + oxide). Two representative synthetic glasses, CPXA01 and CPXB01, were subjected to a series of analyses to investigate the possible qualification of the RMs for in situ Li isotope measurement by LA‐MC‐ICP‐MS, including elemental homogeneity analysis (elemental mapping analysis and spot analysis), Li isotopic homogeneity analysis and accurate Li isotopic determination. The applicability of the synthetic Cpx‐matrix RMs was highlighted by comparing the δ7Li values of three natural Cpx calibrated against the synthetic Cpx‐matrix RMs and other commonly used RMs with different matrices (NIST SRM 612, BCR‐2G, GOR128‐G, StHs6/80‐G, KL2‐G and T1‐G), respectively. Additionally, CPXB01‐05 RMs with the same matrix but different Li contents were prepared to explore the Li content mismatch effect, which is significant for accurate determination of in situ Li isotopic composition by LA‐MC‐ICP‐MS. The results of the cross‐calibration of Li isotopes in CPXA01 and CPXB01 suggested no obvious Li isotopic fractionation between the two types of glasses (GSP‐2 + oxide; L‐SVEC + oxide). Thus, the two methods of producing Cpx‐matrix RMs are suitable for preparing the matrix‐matched RMs for in situ microanalysis for Li isotopes.

Li and Be Isotopes in the PAMELA Experiment from Flight Data for 2006–2014

The results are presented from measuring the isotopic composition of lithium and beryllium nuclei in galactic cosmic rays with energies of up to ~1 GeV/nucleon, obtained with the best statistical and methodical reliability in the PAMELA orbital experiment in 2006–2014. The time-of-flight analysis of nuclei in a scintillation telescope and an analysis of the distributions of ionization losses of the nuclei in the tracker and multilayer calorimeter of the PAMELA magnetic spectrometer with the rigidity known from measuring the path in the magnet gap are used. The analysis uses the results from GEANT4 modeling of the distribution of the time of flight and the ionization losses of nuclear isotopes in the calorimeter with a rigidity step of 0.2 GV, which are in good agreement with the corresponding experimental distributions. Nuclear charges are determined from the scintillation telescope data of the PAMELA magnetic spectrometer. The spectra of 6Li, 7Li, 7Be, 9Be, and 10Be isotopes are obtained, depending on their rigidity, energy, and ratios. The results from measurements are compared to existing experimental and calculated data. Based on new data on the isotopic composition of Li and Be nuclei, the contribution from local light-nucleus sources from recent (~1 million years) nearby (~100 ps) supernova explosions to the intensity of galactic cosmic rays is estimated for the first time.

Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)

An abrupt rise in temperature, forced by a massive input of CO2 into the atmosphere, is commonly invoked as the main trigger for Oceanic Anoxic Events (OAEs). Global warming initiated a cascade of palaeoenvironmental perturbations starting with increased continental weathering and an accelerated hydrological cycle that delivered higher loads of nutrients to coastal areas, stimulating biological productivity. The end-result was widespread anoxia and deposition of black shales: the hallmarks of OAEs. In order to assess the role of weathering as both an OAE initiator and terminator (via CO2 sequestration) during the Early Aptian OAE 1a (Selli Event, ∼120 Ma) the isotopic ratio of lithium isotopes was analysed in three sections of shallow-marine carbonates from the Pacific and Tethyan realms and one basinal pelagic section from the Tethyan domain. Because the isotopic composition of lithium in seawater is largely controlled by continental silicate weathering and high- and low-temperature alteration of basaltic material, a shift to lighter δ7Li values is expected to characterize OAEs. The studied sections illustrate this phenomenon: δ7Li values decrease to a minimum coincident with the negative carbon-isotope excursion that effectively records the onset of OAE 1a. A second negative δ7Li excursion occurs coeval with the minimum in strontium isotopes after the event. The striking similarity to the strontium-isotope record argues for a common driver. The formation and destruction (weathering) of an oceanic LIP could account for the parallel trend in both isotope systems. The double-spike in lithium isotopes is probably related to a change in weathering congruencies. Such a chemostratigraphy is consistent with the hypothesis that an increase in silicate weathering, in conjunction with organic-carbon burial, led to drawdown of atmospheric CO2 during the early Aptian OAE 1a.

The Influence of Hydrothermal Activity on the Li Isotopic Signature of Rivers Draining Volcanic Areas

We explore the geochemistry and the isotopic composition of lithium (δ7Li) of rivers draining volcanic islands (Guadeloupe, Iceland, Java, Martinique and Sao Miguel) with a specific focus on continental hydrothermal activity. Our preliminary results reveal a global-scale trend between δ7Li and the elemental ratio Li/Na in rivers draining volcanic islands. We suggest that this trend results from a mixture between waters with low δ7Li and high Li/Na, inherited from high-temperature water rock interactions, and waters with low Li/Na and high δ7Li, in which Li is controlled by the neoformation of clays during low-temperature chemical weathering in basaltic soils. This latter process can be described by a simple isotope fractionation model, consistent with reported values for isotopic fractionation factors between secondary weathering products and water.These data highlight the important potential role of continental high-temperature weathering processes on the oceanic budget of lithium.

A new SIMS study of Li, Be, B and δ7Li in mantle xenoliths from Harrat Uwayrid (Saudi Arabia)

Concentrations of Li, Be and B and the isotopic composition of lithium have been measured in minerals from a suite of dry and metasomatised spinel peridotite and pyroxenite xenoliths from Harrat Uwayrid, a Pliocene–Quaternary volcanic field in the NW part of the Arabian peninsula, developed during formation of the Red Sea. In most peridotites, Li concentrations in pyroxene and olivine grains show significant systematic zoning, with a core-to-rim decrease in pyroxene but a minor increase in olivine. δ 7Li tends to show a rim-ward increase in clinopyroxene, while it is constant or decreases slightly in olivine. These variations indicate a diffusive transfer of Li from clinopyroxene to olivine during cooling, implying that the partition coefficients K Li Ol/Cpx and K Li Ol/Opx are temperature-dependent and increase with falling temperature. K Li Cpx/Opx, stays nearly constant at ∼ 1. δ 7Li values measured in virtually unmodified cores of olivine, orthopyroxene and clinopyroxene from three peridotites are similar within individual xenoliths but vary among the xenoliths, with individual values ranging from + 1.1 to + 9.7‰. In marked contrast to Li, the concentrations of Be and B are nearly constant in mineral grains, and apparent inter-mineral partition coefficients for these elements are independent of concentrations and xenolith equilibration temperature. Concentrations of Li, Be and B in minerals of un-metasomatized peridotites are relatively low and are similar to values reported previously. Relative abundances of the three light elements in minerals of xenoliths affected by metasomatism have been used to constrain the nature of metasomatic agents. A preferential enrichment of both Li and B relative to Be that is observed in some xenoliths suggests metasomatism by a hydrous fluid, well below the critical point of the solvus between hydrous fluid and silicate melt. A uniform enrichment of all three light elements shown by other xenoliths points to either a silicate melt at subcritical conditions or a supercritical liquid as metasomatic agent.

Determination of lithium isotopic composition by thermal ionization mass spectrometry in seawater

The isotopic composition of lithium in seawater has been determined by thermal ionization mass spectrometry (TIMS) based on the use of lithium hydroxide as the ion source. Isotopic measurements in a reference material supplied by IAEA (L-SVEC Li2CO3) were made to check the reproducibility of the method and δ6Li indicates mobilization of light isotope of lithium form the sediment.

Precise measurement of Li isotopes in planktonic foraminiferal tests by quadrupole ICPMS

Precise measurements of the isotopic composition of Li in low-concentration natural carbonate samples is demonstrated for quadrupole ICPMS. Cool plasma conditions result in high sample/background ratios for the measured Li signals even for low concentrations. Quantitative chemical separation of Li prior to the measurement on ICPMS is necessary to avoid the matrix-induced isotopic fractionation and the results have to be externally corrected for mass bias and instrumental fractionation. The isotopic composition of lithium can be measured in samples containing only 5–10 ng Li with a within-run precision better than 0.5‰ (2 standard errors of the mean), and a long term reproducibility that is better that 2.1‰ (2 standard deviations). The method has been successfully used to measure Li isotopic composition of 1–10 mg samples of calcium carbonate tests of Pulleniatina obliquiloculata and Globorotalia tumida that were collected from the sediment–seawater interface and have Li concentrations of about 1 ppm. The isotopic composition of Li in studied calcium carbonate tests of P. obliquiloculata is independent of the size of tests and resembles the lithium isotopic composition of modern seawater, suggesting that this species may provide a record of Li isotope variations in past oceans.

Structural Study of Liquid Lithium Niobate by Neutron Diffraction Role of the Li Atom in the Clustering Near Solidification

Abstract The structure of liquid LiNbO3 has been investigated by neutron diffraction using samples with different isotopic composition of lithium. The intensity scattered by these samples has been measured for momentum transfers 0.4 Å-1 T> 1500 K, which include the undercooling domain. From an analysis of the correlation functions Gij(r) of the atomic pairs Li-Li, Li-Nb, Li-O and their structural evolutions, given by Δ Gi-j (r) = Gi-j(r)1500 -Gi-j(r)1550 made with reference to the crystalline LiNbO3 ferroelectric structure, it was possible to confirm a local ordering similar to that of the crystal. The presence of clusters (groupings of NbO3 octahedra) is confirmed. Both regular and irregular N b06 octahedra are observed in the liquid near solidification. With its high mobil­ity in the melt, the Li atom plays an important role in the clustering: the Li-O and Li-Nb bonds make possible the staking of four octahedra groups into clusters of eight octahedra or more. The Li-Li bonds join these groups. The diameter of the clusters is a least 22 Å in the undercooling regime.

Isotopic Composition of Lithium in Carbonaceous Chondrites Measured by a Modified Type Surface Ionization Mass Spectrometer.

The isotopic ratios of lithium, 7Li/6Li, have been measured by a modified type surface ionization mass spectrometer whose ion source was newly designed. It needs no chemical preparation prior to the ionization, and makes an analysis of small portions of sample possible. We mainly analyzed the Murchison meteorite and compared with terrestrial laboratory standard samples, spodumene and lepidolite. Many kinds of isotope anomalies for Murchison have been reported, and these anomalies are considered to be originated from presolar events. Spallation reactions are thought to be one of the processes that produced lithium isotopes, and to synthesize 7Li and 6Li isotopes as almost the same quantities. If lithium isotopes produced by such reactions in the presolar stage have been maintained in meteorites, there may be an isotopic anomaly of lithium whose ratio, 7Li/6Li, is extremely lower than that for terrestrial standards. The mean isotopic ratio, 7Li/6Li, for one laboratory standard, spodumene, is 10.519±0.0004, and that for another one, lepidolite, is 11.329±0.0009. The discrepancy between these lithium isotopic ratios is estimated to be due to the different fractionation processes of these minerals. The isotopic ratios for Murchison are within a range from 10.056 to 11.356. This range of the scattering for Murchison is within those for previous works. The lithium isotopic ratios for Murchison analyzed so far gave no significant difference from those for terrestrial standards.

Precise determination of lithium isotopic composition by thermal ionization mass spectrometry in natural samples such as seawater

The isotopic composition of lithium in an NIST SRM 924 Li 2CO 3, isotopically enriched 6 Li 2CO 3 supplied by ORNL and in seawater has been determined by using thermal ionization mass spectrometry (TIMS) based on the use of lithium phosphate as the ion source. In order to minimize isotopic fractionation, the 6 Li + / 7 Li + ion ratio was measured by using a triple filament technique. The method produces a stable, high intensity Li + ion beam that allows measurement of ng quantities of lithium for several hours. Lithium was separated from sample matrix and further converted to LiOH by employing a two-column ion exchange process. The mass ratio of LiOH to phosphoric acid was nearly stoichiometric in relation to Li 3PO 4. Lithium isotopes in a reference material supplied by NIST (L-SVEC Li 2CO 3) was measured to check the reproducibility of the method. A comparison was made between two TIMS units equipped with different types of detectors (a Faraday cup and a secondary electron multiplier). This highly sensitive technique can be applied to determine isotopic composition of Li in enriched isotopes as well as in the examination of low concentration Li reservoirs.

Lithium Isotope Compositions Measured by Multi-Collector ICPMS and the Question of Light Isotope Fractionation at High Temperatures

We report on initial efforts to measure the isotopic composition of lithium using a VG Plasma 54-30 multi-collector magnetic sector ICP-MS. Precision of multiple replicate and duplicate measurements for a variety of sample types ranges from +0.98%0 to +2.1%o (2~ population) level, with a mean uncertainty of + 1.6%o. The method allows for the rapid (c. 9 min/sample) analysis of small samples (c. 40 ng Li). The technique has been applied to a suite of basalts from the Kilauea Iki lava lake, Hawaii. The samples, which range from olivine-rich, high-Mg lava to highly differentiated liquids, have 56Li (6Li/7Li relative to the L-SVEC standard) of -4 .6 to -3.0%0. The data indicate, given our current capacity to resolve differences in ~6Li, a lack of Li isotope fractionation concomitant with crystal-liquid fractionation at temperatures greater than 1000~ This conclusion has been tacitly assumed but never demonstrated, and is important to the interpretation of Li isotope results from such geochemically complex situations as island arcs.

Isotopic Composition of Lithium in Seawater

Isotopic Composition of Lithium in Seawater

リチウムの地球・宇宙化学 Ｌｉ同位体のトレーサーとしての可能性と課題

Geochemical and cosmochemical studies on lithium are reviewed and the potential of lithium isotope systematics as a geological tracer is discussed in this article. Lithium, the smallest of the alkaline elements, possesses two stable isotopes, 6Li and 7Li. It also displays the following unique physicochemical characteristics: (1) an extremely high cross-section of the lithium isotope 6Li for thermal neutrons; (2) high incompatibility in the mafic silicate minerals in the magmatic processes; (3) high solubility in fluid phases; and (4) large isotopic variations in the 6Li/7Li ratio of natural samples exceeding 30‰. The content and isotopic composition of lithium in meteoritic and terrestrial materials may provide important clues to understanding nucleosynthesis theories and many geological phenomena including water/rock interactions, metamorphic and magmatic processes. However, the isotopic behavior of lithium in geologic processes is still not well understood, since only a few reliable isotopic measurements of lithium are available for natural samples due essentially to analytical difficulties; derived from the extremely large mass difference between the two isotopes and no internally-derived correction for the mass fractionation in mass spectrometry. In order to apply lithium isotope systematics for understanding geochemical and water-related processes in the Earth and other planets, the development of a high precision technique for lithium isotope analysis is urgently required so as to accumulate the much needed fundamental data set of natural samples.

Lithium isotopic composition in some stone meteorites

The isotopic composition of lithium has been determined in two achondrites and seven chondrites (including two carbonaceous chondrites). No significant variations in the 7 Li/ 6 Li at the 1% level were found. Our results set upper limits of 1 × 10 19 or 3 × 10 20 protons/cm 2 with E p > 5MeV, depending on the model, for the excess irradiations possibly suffered by these meteorites (including Allende) compared to earth.

Determination of isotopic composition of lithium by neutron activation analysis; comparison with mass spectrometry

An activation analysis method is described for routine determination of6Li-abundances in various lithium compounds on the basis of the reaction sequence6Li(n,α)T and16O(t, n)18F and the measurement of18F. Irradiations of diluted equeous solutions of samples containing CrO3 as internal flux monitor were carried out at a thermal neutron flux density of ϕ≤1011 n·cm−2·sec−1. Interferences from variations in neutron self-shielding oxygen concentration and triton range do not exceed 0.5% when using the dilution technique. The results for6Li abundances from 3.52 to 7.60% with standard deviations of 1 to 2.5% were confirmed by mass spectrometric measurements.

Isotopic composition of lithium in the Allende meteorite.

An anomaly in the isotopic composition of lithium has been searched for in the Allende meteorite. White inclusions, a chondrule and the matrix of Allende were analysed and compared with terrestrial standard rocks and with the meteoritic standards of St. Severin, Peace River and Bruderheim. No anomaly of 7Li/6Li was observed in any of the Allende samples.

Determination of lithium and its isotopic composition by activation analysis and measurement of8Li and17N

The non-destructive determination of lithium was performed by using a Cerenkov counter for the detection of the 13 MeV (max) β-particles from the 0.84 sec8Li produced by the reaction7Li(n,γ)8Li. Under optimal conditions for a favorable signal-to-noise ratio, a count rate of about 35 cps/μg lithium at the beginning of the measurement was obtained, with a background of 4.5 cps and a working range of 3–400 μg lithium. The interference of other elements was studied. Several lithium-containing minerals and a sample of Dead Sea water were analyzed. The isotopic composition of lithium in aqueous solutions was determined by the simultaneous measurement of the neutrons produced by the reactions6Li(n,α)t and18O(t,α)17N, and the β-particles emitted by8Li.

Distribution and isotopic abundance of lithium in stone meteorites

The abundances and isotopic composition of lithium were determined in an achondrite and in separated chondrule and matrix fractions from one chondrite of each of the classes LL3, H3, L4 and L6. No significant variations in the 7Li/6Li ratio were found. The lithium abundances in bulk chondrites are between 1.45 and 2.0 ppm. The abundances in the separated chondrule fractions are not significantly different. The lithium concentration in a bulk sample of the Norton County aubrite is 0.33 ± 0.07 ppm, and in separated coarse enstatite crystais, 0.23 ± 0.04 ppm.

Isotopic composition and abundance of lithium in meteoritic matter

The isotopic composition of lithium and its elemental abundance have been measured in the Bjurböle ohondrite and the Essebi carbonaceous chondrite, as well as in chondrules of these meteorites, and in silicate and troilite inclusions of the Odessa octahedrite. The results are compared with those obtained for terrestrial granite G-1 and with the isotope ratio in diabase W-1. The Li 7:Li 8 ratios agree to within 2 %. The lithium contents found for silicates in Odessa (1.3 and 1.9 ppm) are similar to the values measured for chondrites and chondrules. In two troilite samples of Odessa lithium concentrations of about 40 ppb were found. A lithium content of 21.9 ppm was measured in granite G.l.

The isotopic composition of lithium in chondrules

Trace quantities of Li in chondrules from the Bruderheim and Bjurbole meteorites were isolated by chemical procedures that yielded more than 90% of the Li in the sample. The isotopic composition of Li in two samples of Bruderheim chondrules and one sample of Bjurbole chondrules was measured on a 9-inch-radius-of-curvature, single-focusing mass spectrometer. The problem of mass fractionation which occurs during the mass analysis was solved by an integration procedure. The isotopic composition of Li from two samples of ‘whole-rock’ Bruderheim and one sample of the granite G-1 was also measured for comparison. The Li7/Li6 ratios for the chondrules, whole-rock Bruderheim, and G-1 were found to be identical within 3.3% (at the 95% confidence level). The Li content of all the samples was determined by isotope dilution analyses of aliquots of each sample. The contents found were 0.404 ppm for whole-rock Bruderheim, 0.267 ppm for Bruderheim chondrules, 0.089 ppm for a large lath chondrule from Bruderheim, 0.134 ppm for Bjurbole chondrules, and 20.8 ppm for Gr-1. Blanks were less than 0.3% of the sample sizes in our experiments. We are thus unable to confirm a previous report of a 15% excess of Li6 in the Bruderheim meteorite.