Lithium Isotopes Research Articles

Isotopic Signatures of Lithium Carbonate and Lithium Hydroxide Monohydrate Measured Using Raman Spectroscopy.

Lithium isotopic ratios have wide ranging applications as chemical signatures, including improved understanding of geochemical processes and battery development. Measurement of isotope ratios using optical spectroscopies would provide an alternative to traditional mass spectrometric methods, which are expensive and often limited to a chemical laboratory. Raman spectra of 7Li2CO3, 6Li2CO3, 7LiOH*H2O, and 6LiOH*H2O have been measured to determine the effect of lithium isotope substitution on the Raman molecular vibrations. Thirteen peaks were observed in the spectrum of lithium carbonate, with discernable isotopic shifts occurring in eleven of the 13 vibrations, two of which have not been previously reported in the literature. The spectrum of lithium hydroxide monohydrate contained nine peaks, with discernable isotopic shifts occurring in eight of the nine vibrations, four of which have not been previously reported in the literature. The Raman spectral data reported here for lithium carbonate and lithium hydroxide monohydrate are in agreement with the previously reported works in the literature, in which the Raman active modes of these molecules were first identified and assigned. However, due to the stability and resolution of the detection system used in this work, isotopic shifts with a magnitude less than one wavenumber have been identified. Principal component regression was used to evaluate the sensitivity to isotopic content of small Raman peak shifts in Li2CO3 and indicates differences greater than 2 atom% could be reliably determined. These measurements add to the body of work on lithium isotope Raman spectroscopy for these two compounds and increases the number of Raman bands which could be used for lithium isotope content analysis.

Testing spin-dependent dark matter interactions with lithium aluminate targets in CRESST-III

In the past decades, numerous experiments have emerged to unveil the nature of dark matter, one of the most discussed open questions in modern particle physics. Among them, the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) experiment, located at the Laboratori Nazionali del Gran Sasso, operates scintillating crystals as cryogenic phonon detectors. In this work, we present first results from the operation of two detector modules which both have 10.46 g LiAlO2 targets in CRESST-III. The lithium contents in the crystal are Li6, with an odd number of protons and neutrons, and Li7, with an odd number of protons. By considering both isotopes of lithium and Al27, we set the currently strongest cross section upper limits on spin-dependent interaction of dark matter with protons and neutrons for the mass region between 0.25 and 1.5 GeV/c2.1 MoreReceived 25 July 2022Accepted 15 November 2022DOI:https://doi.org/10.1103/PhysRevD.106.092008© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle dark matterPhysical SystemsWeakly interacting massive particlesTechniquesCryogenicsDark matter detectorsGravitation, Cosmology & Astrophysics

Oscillator strengths and interstate transition energies involving [formula omitted] and [formula omitted] states of the Li atom

We report high accuracy calculations of the ground and excited doublet S and P states of lithium atom. Overall, 24 states corresponding to dominant electronic configurations 1s2ns and 1s2np (n=2,…,13) are considered in the framework of the Ritz variational method. The nonrelativistic wave function of each of these states is generated in an independent calculation by expanding it in terms of a large number (K=11,000−17,000) of all-electron explicitly correlated Gaussian functions (ECG) whose nonlinear parameters are extensively optimized with a procedure that employs analytic energy gradient determined with respect to these parameters. The Hamiltonian used in the calculations explicitly depends on the mass of the nucleus. The leading relativistic and quantum electrodynamics (QED) corrections to the energy levels are subsequently computed using the perturbation-theory approach and the variational nonrelativistic wave functions as the zeroth-order functions. As these functions are generated in the finite-nuclear-mass (FNM) calculations, the energy corrections include the nuclear recoil effects. The obtained energy levels allow us to determine highly accurate interstate transition frequencies for both the naturally occurring stable lithium isotopes, 6Li and 7Li, and the lithium atom with an infinitely heavy nucleus, ∞Li. The nonrelativistic wave functions are used to compute the transition dipole moments and the corresponding oscillator strengths. These quantities are reported for 144 S–P transitions of each isotope. The data set generated in this work is considerably more accurate and comprehensive than the data available from the previous theoretical calculations. It can be useful in guiding future spectroscopic measurements of the lithium atom.

The ecology of modern and fossil vertebrates revisited by lithium isotopes

The vertebrate fossil record documents a plethora of transitions between aquatic and terrestrial environments but their causes are still debated. Quantifying the salinity of living environments is therefore crucial for precising the sequence of ecological transitions. Here, we measured lithium stable isotope composition of mineralized tissues (δ7Limt) of extant and extinct vertebrates from various aquatic environments: seawater, freshwater/terrestrial, and “transitional environments” (i.e. brackish waters, or seasonal access to freshwater and seawater). We report statistically higher δ7Limt values for seawater vertebrates than freshwater ones, taxonomic groups considered separately. Moreover, vertebrates living in transitional environments have intermediate δ7Limt values. Therefore, we show that δ7Limt values of both extant and extinct vertebrates can discriminate their aquatic habitat.

Asthenospheric mantle metasomatized by subducted marine sediments: Li isotopic evidence from Dagze mafic rocks, southern Tibet

Lithium (Li) isotopes show large isotopic fractionation during low temperature processes and have been widely used to trace subduction components at convergent margins. To identify recycled subducting components in the asthenospheric mantle, we report the lithium concentrations and isotopic compositions of the ca. 90 Ma Dagze mafic rocks from the eastern Gangdese Arc, southern Tibet, along with their corresponding whole-rock analyses and Sr-Nd-Pb isotope data. They mainly comprise basalts and diabases with high MgO (7.2–8.3 wt%) and low K 2 O (0.02–0.68 wt%) contents. These rocks show slightly variable initial 87 Sr/ 86 Sr ratios (0.7048 to 0.7057), relatively low and homogeneous Pb isotope ratios ( 206 Pb/ 204 Pb = 18.2948–18.6462, 207 Pb/ 204 Pb = 15.5587–15.6132, 208 Pb/ 204 Pb = 38.3843–38.8352) and positive ε Nd (t) values (3.0–4.9), similar to ophiolites from the Indus-Yarlung Tsangpo suture (IYTS). However, they are remarkably depleted in high field strength elements (HFSE; such as Nb and Ta) and slightly enriched in light rare earth elements (LREE) [(La/Yb) N = 2.8–4.4], both of which imply their mantle affinities with distinctive arc signatures. The δ 7 Li values of these rocks range from −2.0 to +2.0‰ (average = −0.7‰), with the majority of samples falling outside the depleted mantle range (+3.4 ± 1.4‰). They exhibit high Li contents (13.2 to 34.1 ppm) and Li/Y ratios (0.8 to 2.2), which are comparable with marine sediments. The negative correlation between Li/Y ratios and δ 7 Li values also suggests the addition of subducted marine sediments. The modeling of δ 7 Li values in combination with Pb-Sr-Nd isotopic ratios suggests that ~1 to 5% of marine sediments have been added into the mantle source of the Dagze mafic rocks. Combined with a previous study, we suggest that the Dagze mafic rocks were derived from the upwelling asthenospheric mantle metasomatized by subducted marine sediments. • Reporting the negative δ 7 Li values of the Dagze mafic rocks. • Demonstrating the lithium isotopic heterogeneities in the asthenospheric mantle. • Modeling ~1 to 5% of marine sediments to the mantle source of the Dagze mafic rocks.

Origin of highly variable and unusually low δ7Li in mineral separates from ultramafic intrusive rocks in a convergent tectonic setting in the Tibetan plateau

Lithium isotopes are increasingly used as a tracer for the sources of mafic-ultramafic intrusive rocks, but the validity of such approach has never been evaluated directly. We have addressed this issue by analyzing mineral separates from an arc-type mafic-ultramafic complex (namely Xiarihamu) in the Tibetan plateau for Li isotopes. The Xiarihamu complex consists of a gently-dipping, ultramafic chonolith in the center and older gabbro in the margins. The chonolith was interpreted to be a feeder for olivine-charged magma by previous studies. Our new data show minor to strong isotopic disequilibrium between coexisting minerals in the chonolith, with lower δ7Li in clinopyroxene than in coexisting orthopyroxene by up to 7‰. The total range of δ7Li in the pyroxene and olivine separates together is from 5.0‰ to −16.2‰, which is significantly different from that of known arc lavas in the world (3.6 ± 1.2 ‰). Samples from a subvertical drill core of ∼190 m in length penetrating the chonolith show a concentric decrease of δ7Li in orthopyroxene from −16.2‰ in the middle to +1.5‰ and + 3.8‰ in both ends. The δ7Li values of mineral separates show no correlation with whole-rock SrNd isotopes and incompatible trace element ratios, as well as olivine forsterite contents and orthopyroxene Mg/(Mg + Fe) molar ratios, indicating that the observed great variability of δ7Li in the minerals was not caused by variable subduction inputs or magma differentiation alone. A positive correlation exists between orthopyroxene δ7Li and whole-rock LOI, illustrating that serpentinization-talc alteration caused δ7Li in the residual mineral to increase, contributing to the great variability of δ7Li on the mineral scales. Subducting sediment input during magma generation and crustal contamination together cannot adequately account for the observed extremely low δ7Li (−2 to −16.2‰) in the minerals from many of the rock samples as well as the unusually low average δ7Li (−3.5‰) of all of the samples, because the δ7Li of the crust and subducting sediments are much higher. Kinetic fractionation of Li isotopes in response to a temperature gradient across the chonolith as well as to subsequent diffusion of Li from interstitial melt to the mineral phases is the best explanation. Since the kinetic fractionation is independent of tectonic settings, such effect is inevitably present in all mafic-ultramafic intrusions on Earth, illustrating that the effect of kinetic Li isotope fractionation must be considered before using Li isotopic data to constrain mantle sources and magmatic evolution, especially if mineral rather than whole-rock data are employed.

Disorder and wave-function intermixing effects in the luminescence spectra of LiYF4:Ho in external magnetic fields

On the basis of the high-resolution low-temperature photoluminescence spectra of LiYF4:Ho crystals we discuss spectral manifestations of disorder caused by random distribution of either the lithium isotopes or defects in the crystal lattice. A peculiar discrete spectral structure of a different nature was found in the magnetic-field-dependent spectra. We show that it arises due to mixing of the wave functions at the anticrossings of hyperfine levels in a magnetic field.

Solvent extraction for lithium isotope separation by 4-NO2-B15C5/[BMIm][NTf2] system

The evolution of the nuclear industry is inextricably linked to lithium isotopes. With its distinct benefits, the solvent extraction approach is projected to achieve industrial separation of lithium isotopes. However, the lack of studies on the extraction process conditions and mechanisms has limited the development of multi-stage processes. In this paper, based on the 4-NO2-B15C5/[BMIm][NTf2] system, the process conditions and extraction mechanism of the system were investigated by thermodynamic and kinetic studies. The results indicate that lithium isotope separation is a spontaneous exothermic process controlled by diffusion. In addition, DFT calculations show that the binding sites of crown ether and Li+ are located in the coronary heart of crown ether, and electrostatic and van der Waals forces mainly exist between them. On this basis, a 10-stage cross-flow extraction experiment was carried out using crown ether as the extractant. The aqueous phase feed solution is fully utilized, and the 7Li abundance is increased to 93.29 %. In summary, this research provides a foundation for the development of synergistic multi-stage extraction techniques in the future.

A new technique of lithium isotope extraction and separation: Flotation complexation extraction

Flotation complexation extraction can effectively extract and separate lithium isotopes. The effects of nitrogen flow rate, bubble size, gas holdup, reaction flow pattern, aeration time, and temperature on the separation process were studied. In addition, the complex relationship and separation mechanism of lithium with 10-hydroxybenzoquinoline were discussed. Results show that nitrogen flow rate and bubble size significantly affected the flotation complexation extraction process. With an appropriate flow rate, we obtained a homogeneous regime pattern containing small and evenly distributed bubbles to achieve better separation efficiency and ensure a smooth extraction process. According to the slope method, lithium and 10-hydroxybenzoquinoline were complexed and extracted at a ratio of 1: 2. Compared with the traditional oscillating extraction, the bubble mass transfer mode in the flotation complexation extraction strengthened the complex extraction process and achieved higher extraction rate and separation efficiency.

Subsurface weathering signatures in stream chemistry during an intense storm

Long-term relationships between stream chemistry and discharge are regulated by watershed subsurface structure and biogeochemical functioning. The extent to which these mechanisms are expressed and may be explored in the geochemical response of streams during storm events remains an open question. Here, we monitor an intense storm as it infiltrated an upland hillslope draining into a small steep canyon stream that is typified by chemostatic concentration-discharge relationships in rock-derived solutes. Our approach couples a high-frequency record of stable lithium isotope ratios (δ7Li) in the stream with novel sampling of rock moisture within the hillslope. At peak discharge, lithium-sodium ratios (Li/Na) increased from 0.58 μM/mM to 0.82 μM/mM and δ7Li decreased from +28.9±0.1‰ to +26.4±0.4‰ in the stream. Hillslope hydrologic monitoring reveals that the rainwater infiltrated the subsurface, yet attenuated breakthrough of the heavily depleted δD signal of this storm (as low as −86‰) only reached the upper 3-4 meters of the vadose zone. These δD data show that the storm water mixed with previously stored rock moisture and displaced stored fluid to deeper depths, causing an observable rise in the water table. Groundwater 87Sr/86Sr and δ7Li demonstrate consistency in the fluid-rock interactions that occur below the water table prior to and during the storm. In total, these observations indicate that the transfer of fluid and generation of solutes through the interior of the hillslope produce the variability of Li/Na and δ7Li within the stream during the storm, and support application of a previously established 1-D reactive transport model framework developed for the evolution of lithium within the hillslope to this extreme hydrologic event. Based on the model, both Li/Na and δ7Li versus discharge relationships reflect an overall shorter transit time of fluid through the interior of the hillslope. These model results are consistent with our hydrologic observations and indicate that Li from further upslope (where the vadose zone becomes thicker) contributes to stream solute chemistry at the height of the storm. We conclude that in this system, stream lithium isotope signatures record the routing of water and generation of solutes within the hillslope even during intense storm events.

Mineralogy and fluid chemistry controls on lithium isotope fractionation during clay adsorption

Our current understanding of controls on δ7Li variability and fractionation mechanisms is limited, complicating the interpretation of chemical weathering. The role of clay adsorption in Li isotope fractionation during chemical weathering has been confirmed. However, clay assemblage and fluid chemistry are not simple and often variable in weathering settings, potentially modulating Li isotope fractionation on Earth's surface. Here, this research investigated the patterns and processes of Li isotope fractionation during adsorption on kaolinite and smectite with fluid chemistry of 0.001 M NaCl, 0.5 M NaCl, and 0.001 M Na2HPO4. Specifically, the time-dependent experiments with the reaction period up to 15 days revealed that the steady state can be achieved within one day under neutral conditions. The concentration-dependent (initial Li concentration of 2 to 1000 μM) experiments confirmed the accumulation of Li+ in smectite interlayers and adsorption of Li+ only at the external surfaces of kaolinite. Using 0.5 M NaCl solution and the desorption experiments, we hypothesize that outer-sphere Li may exist in the interlayer sites, which can be replaced by excess Na+. In comparison, inner-sphere Li+ (unexchangeable) potentially dominates at the edge surface of clays. The presence of Na2HPO4 increases the binding capacity for Li+ adsorption, in particular for kaolinite. In all cases, 6Li is enriched on clay surfaces and interlayer spaces, consistent with field observations. Fluid chemistry may affect the degree of clay Li adsorption but exerted negligible impacts on isotope fractionation. For kaolinite, a wide variation (up to 30 ‰) in isotopic fractionation between adsorbed and aqueous Li (Δ7Liaq-ad) exists, conforming to a kinetic fractionation mechanism with a constant fractionation factor αad-aq of ~0.992. By contrast, the isotopic fractionation between Li adsorbed on smectite and Li+ left in solutions keeps constant (Δ7Liaq-ad of ~5 ‰), likely following an equilibrium isotope fractionation law with an αad-aq of ~0.995.

Extraction separation of lithium isotopes with Bromobenzene-15-crown-5/ionic liquids system: Experimental and theoretical study

Controlled fusion energy is considered to be one kind of sustainable energy source with clean and green properties. The fusion process requires a large number of lithium isotopes, but the naturally stable lithium isotopes 6Li and 7Li cannot be directly applied to the fusion process and must be further enriched. In this paper, a system for the separation of lithium isotopes by extraction was investigated, which mainly consists of bromobenzene-15-crown-5 and ionic liquids. The effects of ionic liquids, lithium salts, crown ether concentration, and temperature on the separation performance of lithium isotopes were explored. It was found that 6Li was enriched in the organic phase and the single-stage separation factor reached 1.032. It was proved by the temperature experiment that the exchange of lithium isotopes was a spontaneous and exothermic process. The complexation ratio of crown ether and lithium ions was 1:1. The optimized complexation model and the interaction of crown ether and lithium ions were calculated by DFT and Multiwfn. Lithium ions were weakly bonded to the crown ether and strongly bonded to the water molecule as demonstrated by the non-bonded interactions and Mayer bond order of Li-O. Meanwhile, the mechanism of lithium isotope separation with crown ether was clarified by mutual verification of experiment and theoretical calculations.

Lithium Isotope Geochemistry in the Barton Peninsula, King George Island, Antarctica

Lithium (Li) has two stable isotopes, 6Li and 7Li, whose large relative mass difference is responsible for significant isotopic fractionation during physico-chemical processes, allowing Li isotopes to be a good tracer of continental chemical weathering. Although physical erosion is dominant in the Polar regions due to glaciers, increasing global surface temperature may enhance chemical weathering, with possible consequences on carbon biogeochemical cycle and nutriment flux to the ocean. Here, we examined elemental and Li isotope geochemistry of meltwaters, suspended sediments, soils, and bedrocks in the Barton Peninsula, King George Island, Antarctica. Li concentrations range from 8.7 nM to 23.3 μM in waters, from 0.01 to 1.43 ppm in suspended sediments, from 9.56 to 36.9 ppm in soils, and from 0.42 to 28.3 ppm in bedrocks. δ7Li values are also variable, ranging from +16.4 to +41.1‰ in waters, from −0.4 to +13.4‰ in suspended sediments, from −2.5 to +6.9‰ in soils, and from −1.8 to +11.7‰ in bedrocks. Elemental and Li isotope geochemistry reveals that secondary phase formation during chemical weathering mainly control dissolved δ7Li values, rather than a mixing with sea salt inputs from atmosphere or ice melting. Likewise, δ7Li values of suspended sediments and soils lower than those of bedrocks indicate modern chemical weathering with mineral neoformation. This study suggests that increasing global surface temperature enhances modern chemical weathering in Antarctica, continuing to lower δ7Li values in meltwater with intense water-rock interactions.

Experimental Investigation of Oxide Leaching Methods for Li Isotopes.

To examine the applicability of different leaching methods used to extract secondary oxides from silicate solids for lithium isotope (δ7Li) measurement, this study has conducted leaching experiments on five different types of silicate solids, including a fresh basalt, two weathered basalts, a Yellow River sediment (loess‐dominated) and a shale. Four factors were assessed in the experiments: the concentration of the leaching reagent hydroxylamine hydrochloride (HH), the leaching temperature (20 °C vs 95 °C), the leaching time and the reagent/solid ratio. Based on elemental concentrations and Li isotopes, 0.04 mol l−1 hydroxylamine hydrochloride (HH) in 25% v/v acetic acid at room temperature for 1 h with 40 ml g−1 reagent/solid ratio is recommended. At high temperatures, low δ7Li and high magnesium/iron ratios indicate that minerals other than secondary oxides are dissolved. With increased leaching time, there is no evidence for Li isotopic fractionation at room temperature. However, longer leaching time or increased reagent/solid ratios may increase the risk of leaching from non‐oxide phases. Meanwhile, results suggest that low concentrations of HH are not sufficient to target the secondary oxides evenly, while high concentrations of HH can leach out more non‐oxides. We also examined the optimal oxide leaching method within a full sequential leaching procedure (i.e., exchangeable, carbonate, oxide, clay and residual phases). Elemental concentrations show that no elements exist exclusively in oxides, so it is essential to analyse multi‐elemental concentrations to verify that the leaching has accessed this phase in a given sample. Comparing secondary oxides with their corresponding solutions, we estimate the isotopic fractionation (Δ7Lioxide‐solution) is −16.8‰ to −27.7‰.

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

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

Multi-mode chemical exchange in seafloor alteration revealed by lithium and potassium isotopes

Elemental exchange during seafloor alteration exerts substantial control on the chemical compositions of seawater and oceanic crust, as well as the global elemental cycling. However, detailed processes and mechanisms for element transport and isotopic exchange remain unclear. Here, we report Li and K isotopic compositions across an altered MORB-like pillow basalt from Mariana Trench. We find large and systematic isotopic variations on a centimeter scale, with δ7Li decreasing from +9.07‰ to +6.21‰ and δ41K increasing from −0.12‰ to +0.33‰ from the rim to the core. The heavier-than-mantle Li and K isotopic compositions in the core likely inherit from an enriched mantle source rather than post-magmatic alteration processes. The low K and high Li isotopic compositions at the outmost rims result from adsorption during seawater-rock interactions. The basin-shaped elemental and isotopic variations were subsequently formed by chemical diffusion and spontaneous seawater penetration from the weathered rind to the interior of pillow basalt sample. This study uses a small-scale sampling approach and provides the first evidence for multi-mode chemical exchange in oceanic basalts and improves our understanding of the seafloor alteration processes.

Mechanisms of ionic liquids on the enhancement of interfacial transport of lithium ions in crown ether system

Lithium and lithium isotopes are important for clean energy development. By introducing ionic liquid, the extraction performance of crown ethers for lithium ions can be significantly improved. However, the enhancement mechanism of ionic liquids in the system is not clear, which directly limits the selection of suitable ionic liquids for various applications. In this work, the synergy mechanisms of different ionic liquids with crown ether during the extraction process were investigated by molecular dynamics simulations and verified by experimental results. There were two molecular mechanisms to capture lithium ions for ionic liquids in the crown ether system: co-extraction and assisted extraction. It was generally considered that the cation exchange mechanism was responsible for the extraction of lithium ions in the crown ether-ionic liquids system. Here, a novel perspective was revealed that one [Li·H2O]+ complexed with crown ether and then the chelate cation coordinated with the anion of the ionic liquid to form a neutral molecule based on the simulation of the whole extraction process with molecular dynamics that favored the transport of Li+ from aqueous solution to organic solution. In the system without ionic liquids, Li+-crown ether chelates were distributed only at the interface and did not enter the organic phase which is supported by very low extraction efficiency. It was attributed that charge equilibrium cannot be achieved when Li+-crown ether chelates enter into organic solution in the absence of ionic liquids. Overall, a new insight into the interfacial transport mechanisms of lithium ions was proposed, in which the anion of ionic liquids played a key role in capturing lithium ions at the interface of aqueous solution and organic solution.

Lithium isotope fractionation during magmatic differentiation and hydrothermal processes in post-collisional adakitic rocks

To investigate the behavior of Li isotopes during magmatic differentiation and the petrogenesis of Cu-bearing ore deposits, a suite of post-collisional adakitic rocks from Qulong region, southern Tibet, was studied. Their lithologies range from diorite through granodiorite to granite porphyry with the latter containing giant Cu deposits. Detailed evidence of field observation and geochemical signature suggest that these three sets of rocks were most likely formed by various degrees of partial melting and fractional crystallization from the same source. The dioritic enclave, granodiorite and granite porphyry have δ7Li values ranging from 0.2 to 8.2‰, 3.1 to 6.8‰, and 3.9 to 7.4‰, respectively. Most of these samples are overlapping in Li isotope composition, comparable to other granitoids worldwide, indicating insignificant Li isotope fractionation during partial melting and magma differentiation in adakite-like rocks. By contrast, their Li concentrations are mainly controlled by fractional crystallization as suggested from different modal mineralogy. This process does not lead to further enrichment of Cu although they have initial high concentrations (an average of ∼ 104 ppm). In comparison, granite porphyry has extremely high Cu contents (up to 2000 ppm) and their δ7Li values are positively correlated with Cu content, suggesting the involvement of magmatic fluids that most likely exsolved from deep magma chamber. Such fluids not only modified the Li isotopic compositions of granite porphyries, but also extracted metal elements from the highly evolved magma, eventually resulting in the Cu mineralization. Our work here provides new insight into the formation and evolution of the porphyry Cu-bearing deposit.

Experimental and theoretical investigations of lithium isotopes separation using 10-hydroxybenzoquinoline

Experimental and theoretical investigations of lithium isotopes separation using 10-hydroxybenzoquinoline

Hydrological control of river and seawater lithium isotopes

Seawater lithium isotopes (δ7Li) record changes over Earth history, including a ∼9‰ increase during the Cenozoic interpreted as reflecting either a change in continental silicate weathering rate or weathering feedback strength, associated with tectonic uplift. However, mechanisms controlling the dissolved δ7Li remain debated. Here we report time-series δ7Li measurements from Tibetan and Pamir rivers, and combine them with published seasonal data, covering small (<102 km2) to large rivers (>106 km2). We find seasonal changes in δ7Li across all latitudes: dry seasons consistently have higher δ7Li than wet seasons, by −0.3‰ to 16.4‰ (mean 5.0 ± 2.5‰). A globally negative correlation between δ7Li and annual runoff reflects the hydrological intensity operating in catchments, regulating water residence time and δ7Li values. This hydrological control on δ7Li is consistent across climate events back to ~445 Ma. We propose that hydrological changes result in shifts in river δ7Li and urge reconsideration of its use to examine past weathering intensity and flux, opening a new window to reconstruct hydrological conditions.