Li Isotope Research Articles

Effects of lithium isotopes on sodium/lithium co-transport and calcium efflux through the sodium/calcium/lithium exchanger in mitochondria.

The effects of lithium (Li) isotopes and their impact on biological processes have recently gained increased attention due to the significance of Li as a pharmacological agent and the potential that Li isotopic effects in neuroscience contexts may constitute a new example of quantum effects in biology. Previous studies have shown that the two Li isotopes, which differ in mass and nuclear spin, have unusual different effects in vivo and in vitro and, although some molecular targets for Li isotope fractionation have been proposed, it is not known whether those result in observable downstream neurophysiological effects. In this work we studied fluxes of Li+, sodium (Na+) and calcium (Ca2+) ions in the mitochondrial sodium/calcium/lithium exchanger (NCLX), the only transporter known with recognized specificity for Li+. We studied the effect of Li+ isotopes on Ca2+ efflux from heart mitochondria in comparison to natural Li+ and Na+ using Ca2+-induced fluorescence and investigated a possible Li isotope fractionation in mitochondria using inductively coupled plasma mass spectrometry (ICP-MS). Our fluorescence data indicate that Ca2+ efflux increases with higher concentrations of either Li+ or Na+. We found that the simultaneous presence of Li+ and Na+ increases Ca2+ efflux compared to Ca2+ efflux caused by the same concentration of Li+ alone. However, no differentiation in the Ca2+ efflux between the two Li+ isotopes was observed, either for Li+ alone or in mixtures of Li+ and Na+. Our ICP-MS data demonstrate that there is selectivity between Na+ and Li+ (greater Na+ than Li+ uptake) and, most interestingly, between the Li+ isotopes (greater 6Li+ than 7Li+ uptake) by the inner mitochondrial membrane. In summary, we observed no Li+ isotope differentiation for Ca2+ efflux in mitochondria via NCLX but found a Li+ isotope fractionation during Li+ uptake by mitochondria with NCLX active or blocked. Our results suggest that the transport of Li+ via NCLX is not the main pathway for Li+ isotope fractionation and that this differentiation does not affect Ca2+ efflux in mitochondria. Therefore, explaining the puzzling effects of Li+ isotopes observed in other contexts will require further investigation to identify the molecular targets for Li+ isotope differentiation.

Lithium isotopic composition of low-temperature altered oceanic crust and its implications for Li cycling

To investigate the Li fluxes and its isotopic fractionation during low-temperature seafloor alteration, we present the Li isotope compositions of fifty fresh and altered basalts drilled from the Integrated Ocean Drilling Program (IODP) 329 Expedition Sites U1365 and U1368, which show different low-temperature (<150 °C) alteration styles and intensities (i.e., total volume of secondary minerals and degrees of elemental enrichment) with meager sedimentation rates (0.71 and 1.1 m/Myr, respectively). The fresh basalts (δ7Li vary from +2.7 to +6.4) show Li isotope compositions consistent with the published N-MORB (+3.5 ± 1.0‰), whereas the altered basalts exhibit considerably higher δ7Li values (+1.7‰ to +11.6‰). Furthermore, their δ7Li values show positive correlations with alkali elements and loss on ignition and follow a mixing trend between a MORB-like endmember and a Li-rich seawater-derived endmember (+9.2 ± 0.2‰), which indicates the effects of low-temperature seafloor alteration on Li isotopic compositions. Based on previously reconstructed paleo-seawater Li isotope compositions, the Li isotopic fractionation scale between seawater and altered basalts is estimated (+12.6‰ and +18.0‰ for Sites U1365 and U1368, respectively), which further supports previous conclusions that the scale of Li isotope fractionation changes over time. A mass calculation suggests the upper limits of the Li-uptake fluxes during low-temperature seafloor alteration are 14.9 ± 2.2 × 109 mol/year and 3.6 ± 1.3 × 109 mol/year for Sites U1365 and U1368, respectively. In addition, our estimation shows the Li-uptake flux during low-temperature seafloor alteration in the Cretaceous is comparable to the total Li-input flux, whereas, in the Neogene, the Li-uptake flux during low-temperature seafloor alteration is much lower than that of the Li-input flux, which suggests a large diagenetic Li sink may be necessary to maintain the seawater Li budget balance if we assume the seawater Li concentration is roughly constant.

Lunar Surface Resource Exploration: Tracing Lithium, 7 Li and Black Ice Using Spectral Libraries and Apollo Mission Samples

This is an exercise to explore the concentration of lithium, lithium-7 isotope and the possible presence of black dirty ice on the lunar surface using spectral data obtained from the Clementine mission. The main interest in tracing the lithium and presence of dark ice on the lunar surface is closely related to future human settlement missions on the moon. We investigate the distribution of lithium and 7 Li isotope on the lunar surface by employing spectral data from the Clementine images. We utilized visible (VIS–NIR) imagery at wavelengths of 450, 750, 900, 950 and 1000 nm, along with near-infrared (NIR–SWIR) at 1100, 1250, 1500, 2000, 2600 and 2780 nm, encompassing 11 bands in total. This dataset offers a comprehensive coverage of about 80% of the lunar surface, with resolutions ranging from 100 to 500 m, spanning latitudes from 80°S to 80°N. In order to extract quantitative abundance of lithium, ground-truth sites were used to calibrate the Clementine images. Samples (specifically, 12045, 15058, 15475, 15555, 62255, 70035, 74220 and 75075) returned from Apollo missions 12, 15, 16 and 17 have been correlated to the Clementine VIS–NIR bands and five spectral ratios. The five spectral ratios calculated synthesize the main spectral features of sample spectra that were grouped by their lithium and 7 Li content using Principal Component Analysis. The ratios spectrally characterize substrates of anorthosite, silica-rich basalts, olivine-rich basalts, high-Ti mare basalts and Orange and Glasses soils. Our findings reveal a strong linear correlation between the spectral parameters and the lithium content in the eight Apollo samples. With the values of the 11 Clementine bands and the 5 spectral ratios, we performed linear regression models to estimate the concentration of lithium and 7 Li. Also, we calculated Digital Terrain Models (Altitude, Slope, Aspect, DirectInsolation and WindExposition) from LOLA-DTM to discover relations between relief and spatial distribution of the extended models of lithium and 7 Li. The analysis was conducted in a mask polygon around the Apollo 15 landing site. This analysis seeks to uncover potential 7 Li enrichment through spallation processes, influenced by varying exposure to solar wind. To explore the possibility of finding ice mixed with regolith (often referred to as `black ice’), we extended results to the entire Clementine coverage spectral indices, calculated with a library (350–2500 nm) of ice samples contaminated with various concentrations of volcanic particles.

Lithium systematics in the Krafla volcanic system: comparison between surface rhyolites and felsic cuttings from the Iceland deep drilling project -1 (IDDP-1)

The unexpected discovery of felsic magma by the Iceland Deep Drilling Project-1 (IDDP-1) in the Krafla volcanic system (KVS) presents a unique opportunity to investigate pre-eruptive lithium (Li) dynamics and establish a more direct connection between magma reservoirs and volcanic deposits. Our study provides new insights into Li abundances and isotope compositions in bulk-rock, minerals, and groundmass glass from rhyolitic lavas at KVS, encompassing various stages of groundmass crystallisation. Additionally, we examined felsic cuttings retrieved from the IDDP-1 well, comprising crystal-poor obsidian and crystal-bearing to -rich ‘felsite’ particles. Groundmass glasses from surface lavas show limited variability in K/Na, indicating limited secondary hydration of the glasses and that their Li contents seem to not be affected by this post-eruptive process. Lithium inventories in groundmass glasses and minerals within lavas exhibit variations consistent with the cooling history of the deposit, resembling patterns seen in Snake River Plain ignimbrites. Lithium contents of glassy rhyolitic lavas, whether bulk-rock (avg. 27.2 ± 3.1 μg/g) or groundmass glass (average 28.4 ± 4.7 μg/g), and their bulk isotopic compositions (avg. δ7Li =+ 4.4 ± 0.2‰) overlap with those observed in IDDP-1 obsidian cuts (avg. 24.9 μg/g Li in bulk, 28.6 ± 1.5 μg/g in groundmass glass, and δ7Li = 4.5 ± 0.2‰). Glassy lavas lacking spherulites may potentially preserve pristine magmatic Li element and isotope compositions, while areas with extensive groundmass crystallisation reveal Li enrichments in phenocrysts. Plagioclases in slowly cooled parts of the deposit record a two-fold increase in Li contents compared to plagioclase found in glassy counterparts, along with evidence of open-system degassing marked by heavier bulk Li isotope compositions and lower bulk Li contents of the crystallised lava portions (avg. δ7Li = +7.2 ± 0.1‰ and 7 ± 0.8 μg/g Li) relative to bulk glassy lithologies (avg. δ7Li = +4.1 ± 0.1‰ and 28 ± 2 μg/g Li). Partition coefficients derived from IDDP-1 cuts successfully predict Li inventories in vitrophyres of rhyolites on the surface of the KVS. Lithium isotope compositions of the crystal-rich IDDP-1 cuts are significantly heavier (avg. δ7Li = +7.2 ± 0.2‰) than lavas and IDDP-1 obsidian cuts, casting doubt on the notion that the IDDP-1 rhyolitic magma could result from the melting of felsite lenses in the KVS. Lithium contents in groundmass glasses within IDDP-1 crystal-rich cuts show higher Li contents (avg. 55.1–60.7 μg/g), correlating with the higher crystal content and an increase in other incompatible elements (avg. 250 μg/g Rb) relative to obsidian cuttings (avg. 75 μg/g Rb).

Electron Scattering from Stable and Exotic Li Isotopes

The nuclear shell model was used to investigate the bulk properties of lithium isotopes (6,7,8,9,11Li), i.e., the ground state density distributions and C0 and C2 components of charge form factors. The theoretical treatment was based on supposing that the Harmonic-oscillator (HO) potential governs the core nucleons while the valence nucleon(s) move through Hulthen potential. Such assumptions were applied for both stable and exotic lithium isotopes. The HO size parameters ( and ), the core radii ( ) and the attenuation parameters ( and ) were fixed to recreate the available empirical size radii for lithium isotopes under study.

Experimental and theoretical constraints on lithium isotope fractionation during brine evaporation and halite precipitation

Marine evaporitic halite, precipitating from the advanced stage of extremely evaporated seawater, is the most common and abundant evaporitic mineral. The extent to which lithium (Li) is incorporated into evaporite halite during geological periods of massive halite deposition, and the mechanisms of incorporation, are both unknown. These are each important, however, for the quantification of the isotope effect of the evaporitic sink on δ7Liseawater, and for the potential use of halite as a recorder of seawater δ7Li. Here, new experimental data are presented for the Li fractionation factor for halite from an isothermal evaporation experiment (25∘C for 100 days) using marine-derived brine. The resultant solids were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm the mineralogy and crystallinity of the product. Our results show that Li isotopes are not constant during the evaporation process implying that there must be a process that fractionates Li isotopes during halite precipitation. We suggest that this results from Li ionic substitution for sodium (Na) in crystalline halite, a scenario supported by ab-initio calculations, but we also show that Li within halite is predominantly present within fluid inclusions. Thus, the Li isotopic composition of halite is controlled by a mixture of Li within the fluid inclusions and Li that is incorporated into the halite crystalline structure. Overall, the brine becomes enriched in Li7 during evaporation due to the preferential incorporation of Li6 into chloride precipitates, and the evolution of δ7Librine is controlled by the precipitated mineral assemblage. The theoretical equilibrium fractionation factor 1000lnαmineral−fluid is -7.8▪ for Li-halite (LiNa26Cl27) at 25 C∘ at equilibrium, which is at the lower limit of Li isotope fractionation factors. Rayleigh fractionation models were fitted to the experimental data yielding a fractionation factor of -25▪3▪. The difference in Li isotope fractionation factor between brine and structurally bound Li may result from kinetic fractionation effects. This study presents a scenario highlighting that extensive halite deposits, formed over geological time in environments with relatively high Li concentration, could potentially impact the δ7Li values of seawater during that period, and place constraints on their utility as an archive for δ7Liseawater.

Lithium isotope fractionation during submarine hydrothermal alteration processes

River water and submarine hydrothermal fluids are the two primary sources of lithium (Li) input to the ocean. However, compared to well-documented weathering processes, the behavior of Li isotopes during hydrothermal alteration processes remains obscure. In this research, we investigated the Li isotopic compositions (δ7Li) of hydrothermally altered sediments from two IODP drilling cores (C0013 and C0014) in the Iheya North Knoll of the middle Okinawa Trough. The sediments, primarily altered from volcanic clasts, exhibit a pristine δ7Li value (5.2 ± 0.7 ‰) similar to that of MORB (3.7 ± 1 ‰). Intense hydrothermal activity led to the complete conversion of primary feldspars into phyllosilicates, predominantly Mg-chlorite, at site C0013 and in the middle and deep parts of C0014. The altered samples showed a depletion of 7Li (ranging in δ7Li from −10.0 ‰ to 4.2 ‰) compared to background sediment, indicating the preferential incorporation of 6Li during the formation of secondary minerals. Furthermore, both drilling sites exhibited increasing trends in δ7Li values with depth, with the deepest samples approaching the pristine δ7Li values of unaltered volcanic rock. These trends were attributed to the significant thermal gradients present at both sites. The temperature-dependent fractionation factor of Li isotopes allowed us to estimate the alteration temperature, which yielded temperature values consistent with those obtained using the δ18O geothermometer. This finding underscores the potential of Li isotopes as a novel geothermometer tool, although further calibration work is required. Based on our research findings, we developed a dissolution-precipitation model (based on mass balance) that establishes a relationship between the δ7Li values of altered solids and hydrothermal fluids, with the aim of elucidating the relatively limited variation observed in global submarine hydrothermal fluids (ranging from 1.6 ‰ to 11.0 ‰, with an averaged value of 5.9 ± 3.0 ‰, mean ± SD). This model quantitatively depicted the strong restriction of the Li concentration in hydrothermal fluids on their isotopic compositions, as high concentrations of Li in the fluids necessitate a substantial release of Li from the solid phase, causing the fluids' δ7Li values to approach that of the bedrock. Additionally, limited fractionation factors at high temperatures further constrain the variations in the fluids' δ7Li values. Model predictions also suggest that the reported δ7Li values of hydrothermal fluids have encompassed the potential δ7Li variation, providing supporting evidence for the assumption that δ7Li values of submarine hydrothermal fluids have exhibited insignificant variations throughout Earth's history.

Factors controlling lithium accumulation in brines from Upper Cretaceous to Lower Eocene aquifers of a continental evaporite basin

The origin of deep-seated Li-rich brines in a continental evaporite basin remains poorly understood. To clarify hydrogeochemical processes governing the Li enrichment, this study investigated chemical compositions and multi-isotopic (H–O–Li–Sr) features of a set of water samples from Upper Cretaceous to Lower Eocene sedimentary brines, saline groundwaters and oilfield brines, thermal waters and surficial river waters in the Jiangling Basin, central China. Waters from deep reservoirs evolve through multiple hydrogeochemical processes including evaporation, dilution, water-rock reactions and evaporite dissolution. These processes cause a range of Li and Sr contents (5.43–100 mg/L and 32.8–1307 mg/L) and isotope compositions (+8.6 to +19.3‰ and 0.706926–0.712480), indicating contributions from reservoir rock dissolution to δ7Li values and 87Sr/86Sr ratios. Chemical geothermometers applied to brines, saline waters and thermal waters give reservoir temperature values ranging between 70 and 200 °C. Temperature has a distinct effect on advancing host rock-water interactions, while high-temperature waters enhance leaching of Li in rocks compared to the low- and medium-temperature waters. The variable δ7Li values lower than river waters and high Cl/Br ratios in the Upper Cretaceous to Lower Eocene aquifers suggest a result of evaporite dissolution to different degrees, whilst waters in the Upper Cretaceous aquifers have the lowest δ7Li values similar to the thermal waters and the highest Cl/Br ratios suggest a stronger salt dissolution effect. Multi-isotope tracing highlights the role of temperature, reservoir rock types and different hydrogeochemical processes in defining the geochemical and isotopic water composition. Combination of these factors, together with high heat gradients associated with intense volcanic activity eventually results in Li accumulation in deep-seated brines from the Jiangling evaporite basin. Our results contribute to a further comprehensive understanding of hydrogeochemical processes that dominate deep brine formation and Li enrichment in an ancient continental evaporite basin.

Controls on the formation of Mn carbonates in mudrocks of the Datangpo Formation, Northern Margin Rift Basin, Yangtze Block

Deglaciation following the Sturtian Ice Age led to widespread manganese carbonate precipitates within marine mudrocks, reflecting unique climatic and oceanographic changes. The Mn carbonates hold economic importance in the Datangpo Formation, Yangtze Block, South China. Although their genesis in the Nanhua Rift Basin is well understood, little is known regarding their formation mechanism in the North Margin Rift Basin (NMRB). With growing interest in Mn ore exploration in this region, this study examines the weathering trend, climate patterns and watermass conditions using a variety of geochemical proxies. The results reveal two phases of climate variation during the deglaciation. Climate during the early phase (Phase I) was unstable, characterized by fluctuating values of Chemical Index of Alteration (CIA = 65 ± 4) and elevated Li isotope (8.8 ± 3.0‰) patterns. The degree of chemical weathering during the later stage (Phase II) was relatively stable (CIA = 65 ± 1, δ7Li = 5.4 ± 2.7‰), but the weathering intensity increased due to the reduced denudation rate, possibly related to a shift in the basin development. Fe speciation data indicate euxinia prevailing much of the section. However, Mo and U enrichment (> 1) and fluctuating ratios of Mo versus total organic content (0–40) suggest that pulses of freshwater influx associated with climate variation during Phase I caused the fluctuation of the chemocline along the continental shelf, facilitating the formation of Mn carbonates through the particulate Fe-Mn-hydroxide shuttle. With the establishment of stabilized climate, basin tectonics, and watermass circulation during Phase II, the accumulation of Mn carbonates in the sediments became less significant. The accumulation of Mn carbonates in the NMRB conforms to the “bathtub ring model”, distinct from the metallogenic model in the NRB, providing valuable guidance for Mn ore prospecting within this area and elsewhere with similar settings.

Sources of Li isotope bias during SIMS analysis of standard glasses

The 7Li/6Li ratios in fourteen USGS, MPI-DING, and NIST glass reference materials (RMs) were analyzed by LG-SIMS to assess compositional matrix effects, evaluate RM δ7Li homogeneity, and calculate the useful yield of lithium in silicate glasses. The analyzed RMs cover a range of SiO2 contents from 45.5 to 75.6% (komatiite to rhyolite), the largest compositional range yet evaluated for δ7Li matrix effects. We observe a matrix-induced bias (matrix effect) of up to 18‰ over the studied range that has a negative linear correlation with SiO2 content, demonstrating that SiO2 content is a critical factor that must be considered when using silicate glasses to standardize for silicate samples of unknown δ7Li composition. All RMs were found to be sufficiently reproducible to aid in standardization of variable SiO2 contents and appear isotopically homogeneous at the precision of our measurements. Lithium ionizes very efficiently in these RMs, with measurable yields >5% in all fused-rock RMs and > 15% in low SiO2 fused-rock RMs measured at high beam intensities. Fused-rock RMs ionize lithium 2-3× more efficiently than synthetic glass RMs, which may be related to differences in major oxide chemistry and the reduced nature of the synthetic glasses relative to their fused counterparts.

Diffusion-induced lithium isotopic heterogeneity in olivines from peridotites of an oceanized mantle lithosphere at the Yunzhug ophiolite (central Tibet)

This paper reports lithium concentrations and isotopic compositions of olivines in the oceanized subcontinental lithospheric mantle (SCLM) peridotites of the Tibetan Yunzhug ophiolite. The results show systematic Li isotope changes with distance from the rim of olivine grains. δ7Li values of olivine in dunites decrease from + 10.46 to + 1.33‰ with increasing distance to olivine rim from 26.15 to 124.71 μm. A negative correlation of δ7Li and Li content in olivine from dunite and harzburgite indicates recent diffusive ingress of Li into the peridotites. The extremely heavy Li isotopic composition requires the seawater or seawater alteration endmember in the mixing model, and reveals Li diffusion from seawater into olivine. As in dunites, olivines in a harzburgite sample show similar variations in δ7Li as a function of distance from the grain rim (e.g., 6.01 to 1.73 in sample 14YZ13). We suggest that the behavior of Li in the oceanized SCLM peridotites may be controlled by Li diffusion from seawater, as Li activity in the liquid state is higher than the solid state in transporting Li through the olivines in the peridotites. This study supports that seawater Li diffusion is one of the important factors for the heterogeneity of mantle Li isotopes in ophiolites.

Petrogenesis of Mesozoic pegmatites in the Dahongliutan Li-mineralized belt (Western Kunlun, NW China)

The genesis of pegmatite and the associated Li-mineralization mechanism remain debated. The intimate temporal-spatial relationship between the pegmatites in the Dahongliutan Li-mineralized belt (incl. #509 Daoban and Akshay Li-poor pegmatites, and Akshay Li-rich pegmatite) and the Dahongliutan granite pluton allows us to discuss the origin of pegmatite and the Li-mineralization mechanism by conducting detailed geochemical and geochronological investigations on the two rock units in the Western Kunlun orogen (NW China). The Li-poor pegmatites in the Dahongliutan Li-mineralized belt exhibit similar or much lower Li, Rb, and Cs compared to the adjacent granite, and their εNd(t) values (-8.7–-10.0) are significantly lower than those of the granite (-7.5–-8.1) as well. However, the Akshay Li-rich pegmatite shows extremely high Li, Rb, Nb, Ta, and initial Sr isotopic ratios (0.7223–0.7227, obtained from apatite), in contrast to the Dahongliutan granite (ISr = 0.7108–0.7157). The whole-rock δ7Li values of the Dahongliutan granite, pegmatites, and the wall-rock Bayanharshan Group metapelite are + 0.76–+5.67 ‰, +0.8–+14.4 ‰, and −4.2–+2.8 ‰, respectively. Zircon and cassiterite U-Pb dating yielded 206Pb/238U ages of 216 ± 2 Ma and 195 ± 2 Ma for the #509 Daoban Li-poor pegmatite and Akshay Li-rich pegmatite, respectively. Modeling of trace elements and Li isotopes suggests that the pegmatites in the Dahongliutan Li-mineralized belt did not originate from fractional crystallization of granitic magma. Instead, they may have formed through direct anatexis under amphibolite-facies conditions. Abundant Li-rich claystone, occasionally accompanied by evaporite, may exist in the magma source of the Li-rich pegmatite, which is the key factor controlling pegmatitic Li mineralization.

Lithium isotope fractionation in highly evolved granites and associated magmatic-hydrothermal process: the case of the Xintianling granites in the Nanling Range, South China

ABSTRACT The highly evolved granites are closely associated with rare-metal mineralization. It is still debated whether the enrichment of rare metals is mainly controlled by magmatic or hydrothermal processes. Lithium is a fluid-mobile element that preferentially partitions to the fluid phase when the melt reaches H2O saturation, making the Li isotope system a powerful geochemical tool to record the potential melt-fluid interaction during magma evolution. This study addresses the issue of Li isotope fractionation in highly evolved fine syenogranites (FSGs) from the Xintianling pluton in the Nanling Range, South China. The Xintianling pluton consists of the coarse biotite monzogranites (CBMGs) and evolved FSGs. The identical Nd isotope data of the CBMGs (εNd(t) = -8.2–-8.8) and FSGs (εNd(t) = -7.9–-8.9) suggest that they were derived from the same crustal magma. The FSGs were derived from the highly evolved melts extracted from CBMGs through the fractionation of major rock-forming minerals. This is supported by the compositional shifts and validated by Rb, Sr, and Ba trace element modelling. Li isotopic analysis shows that highly evolved FSGs have heavier Li isotope compositions (δ7Li = 2.6–7.9 ‰) than the CBMGs (δ7Li = 0.1–1.9 ‰). Isotopic modelling, coupled with variations in Li concentrations in FSGs, suggests that diffusive kinetic fractionation by disequilibrium fluid exsolution during the late stage of the granitic magma evolution controls the Li isotope fractionation of the Xintianling granites. Rapid fluid exsolution not only modified the Li isotope composition of the FSGs but also transported the rare metals (e.g. W) and fluxing components (Li, F, and Cl), which resulted in the formation of the large Xintianling W deposits.

Assessment of Chalk as an Archive for the Lithium Isotope Composition of Seawater

AbstractThe understanding of silicate weathering and its role as a sink for atmospheric CO2 is important to get a better insight into how the Earth shifts from warm to cool climates. The lithium isotope composition (δ7Li) of marine carbonates can be used as a proxy to track the past chemical weathering of silicates. A high‐resolution δ7Li record would be helpful to evaluate the role of silicate weathering during the late Cretaceous climate cooling. Here, we assess chalk as a potential archive for reconstructing Late Cretaceous seawater Li isotope composition by comparing Maastrichtian chalk from Northern Germany (Hemmoor, Kronsmoor) to a Quaternary coccolith ooze from the Manihiki Plateau (Pacific Ocean) as a lithological analog to modern conditions. We observe a negative offset of 3.9 ± 0.6‰ for the coccolith ooze relative to the modern seawater Li isotope composition (+31.1 ± 0.3‰; 2SE; n = 54), a value that falls in the range of published offsets for modern core‐top samples and for brachiopod calcite. Further, the negative offset between the Li isotope compositions of Manihiki coccolith ooze and modern planktonic foraminifera is 2.3 ± 0.6‰. Although chalk represents a diagenetically altered modification of pelagic nannofossil ooze, manifested by changes in the composition of trace elements, we observe a consistent offset of Li isotope data between Maastrichtian chalk and Maastrichtian planktonic foraminiferal data (−1.4 ± 0. 5‰) that lies within the uncertainty of modern values. We therefore suggest that chalk can be used as a reliable archive for δ7Li reconstructions.

Source and genesis of Ca-Cl type brines in Qaidam Basin, Qinghai-Tibetan Plateau: evidence from hydrochemistry as well as B and Li isotopes

Ca-Cl brine is a highly mineralized special water body occurring in oceanic ridges or basins. The deep part of the western Qaidam Basin is rich in Ca-Cl brine, which is essential for the formation of (MgSO4-deficient) potash deposits. Previous studies on this type of brine in the Qaidam Basin focused on its source tracing, but different carriers led to different conclusions. Moreover, the genesis of Ca-Cl brines in inland basins still remains unclear. In essence, a solid understanding of the relatively abundant Ca sources for the formation of Ca-Cl brines in inland basins has not been reached. In addition, a metallogenic model for this type of brine has not yet been established. Through hydrochemical analysis as well as Band Li isotope tracing, this study clarified that the main elements (Na and Cl) in these Ca-Cl brines mainly originated from the dissolution of existing evaporites in the inner basin. Further, trace elements in Ca-Cl brines (such as Band Li) mainly originated from lixiviation; atmospheric rainfall infiltrated and interacted with ore-rich mother rocks along the basin-margin fracture system under suitable temperature-pressure conditions; alternatively, they may have originated from mixing with magmatic hydrothermal fluids. This study showed that Ca-Cl brines in the western part of the Qaidam Basin have a typical “binary structure” in terms of their sources. In addition, the sources of Ca in Ca-Cl brines were further discussed based on B and Li isotope data, thus exploring a new genesis of Ca-Cl brines in inland basins. Finally, by integrating the above findings, an ore-forming model of this type of water body in the western part of the Qaidam Basin is proposed. This study is valuable for understanding the genesis mechanism of Ca-Cl brines in inland basins, and also has practical significance for the prediction, exploration, and evaluation of this type of brine resource.

Lithium Tetraborate as a Neutron Scintillation Detector: A Review

The electronic structure and translucent nature of lithium tetraborate (Li2B4O7) render it promising as a scintillator medium for neutron detection applications. The inherently large neutron capture cross-section due to 10B and 6Li isotopes and the ease with which Li2B4O7 can be enriched with these isotopes, combined with the facile inclusion of rare earth dopants (occupying the Li+ sites), are expected to improve the luminescent properties, as well as the neutron detection efficiency, of Li2B4O7. The electronic structure of both doped and undoped Li2B4O7 were explored, using photoemission and inverse photoemission spectroscopies, optical measurements, and theoretical computational studies such as density functional theory. The scintillation properties are further enhanced because of the wide bandgap, making Li2B4O7 extremely translucent, so that capturing the neutron scintillation output is neither hindered nor diminished. Therefore, in this review, demonstrations of the possible amplification of neutron capture efficiencies, courtesy of rare-earth dopants, along with insights into a significantly large charge production (associated with neutron capture), are presented.

The influence of crystal chemistry on lithium isotopic fractionation in pegmatite minerals

The understanding of lithium (Li) isotopic fractionation controlled by mineral species, especially those containing trace or minor amounts of Li (e.g., a few to tens of ppm), is hindered by lack of knowledge about the crystal chemistry of Li-bearing minerals. In this study, we performed solid-state Nuclear Magnetic Resonance (NMR) experiments, employing the Li7 Magic Angle Spinning (MAS) to investigate the local coordination environments of Li in minerals and their impact on Li isotopic fractionation. Our investigation focused on four coexisting minerals sourced from the Koktokay No. 3 pegmatite dike in the Xinjiang, China, namely quartz, K-feldspar, muscovite, and tourmaline, which has Li content and δLi7 value of 14.6 ppm and 3.90‰, 19.3 ppm and 7.09‰, 430 ppm and − 14.2‰, and 108 ppm and 13.42‰, respectively. Muscovite displayed the lowest δLi7 value, whereas tourmaline exhibited the highest value, and a considerable variation of 27.62‰ in δLi7 value was observed between muscovite and tourmaline. The analysis of Li7 MAS-NMR spectra further revealed distinct Li coordination environments among these minerals. A notable counterintuitive negative correlation exists between the δLi7 value and the chemical shift for the four Li-bearing minerals. This negative correlation contrasts to the expected Li isotopic fractionation under equilibrium conditions, in which enrichment of heavy Li isotopes is accompanied with large chemical shifts in Li-bearing minerals. This unexpected observation can be potentially attributed to nonequilibrium conditions of crystallization of the investigated minerals, coupled with fast diffusion of Li6 in minerals, boasting abnormally high coordination numbers due to weak LiO chemical bonds. Essentially, our study suggests that Li isotopic fractionation among Li-bearing minerals in pegmatite can be significant and is intricately influenced by both crystal chemistry and chemical diffusion.

Geochemical constraints on the origin of the rare metal mineralization in granite-pegmatite, evidence from three-kilometer scientific drilling core in the Jiajika Li deposit, eastern Tibetan Plateau

Although the metallogenic mechanism of the Jiajika super-large Li deposits in the eastern Tibetan Plateau has been proposed closely linked to development of the Majingzi granite pluton, the petrogenesis and evolutionary linkages between granite–pegmatites and Li mineralization still remain controversial. Here we investigated Li-Nd isotopes together with major and trace elemental data from a 3-km scientific drillcore and surface samples (including the Li-rich/poor pegmatites, the associated two-mica granite and the metasedimentary rocks) to reveal the magmatic evolution and Li-enrichment mechanism of the Jiajika deposit. In the drillcore, the Li-poor pegmatites overall exhibit low Li isotope values (δ7Li = −1.38 ‰ to +1.98 ‰, mean of +0.34 ‰) and low Li contents (67 to 45 ppm), while the Li-rich pegmatites show slightly higher δ7Li values (+0.9 ‰ to +1.1 ‰) and high Li contents (3078 to 6012 ppm). Additionally, the Li-poor pegmatites have εNd(t) values of −17.1 – −2.5 (mean of −10.34) and low Nd concentration (<10 ppm), similar to the two-mica granite (εNd(t)avg = −11.18 and Ndavg = 7.08 ppm), whereas the schists and calc-silicate rocks in the drillcore have relatively higher εNd(t) values (−11.9 to −2.4 with a mean of −7.3) and Nd contents (>20 ppm). These data, together with consistently low Nb/Ta、Zr/Hf of the deep-drilled pegmatites and two-mica granites, suggest that the Jiajika pegmatites are not directly derived from low degrees of partial melting of the Triassic metasediments (e.g., biotite shists or calc-silicate rocks), but more likely from extreme magmatic fractional crystallization of the Majingzi two-mica granite pluton. For the surface samples, the δ7Li values of the surface Li-poor pegmatite samples (−0.61 ‰ to +2.56 ‰ with a mean of +0.36 ‰) are slightly higher than that of the Li-rich pegmatites (−0.52 ‰ to −0.27 ‰ with a mean of −0.39 ‰), and the two-mica granites samples show relatively variation in δ7Li (−1.25 ‰ to +3.33 ‰ with a mean of +0.73 ‰). The surface granites and pegmatites are characterized by high A/CNK values (>1.1) and low K/Rb values (<200), and particularly, the degree of REE tetrad effect gradually increases from granites to pegmatites. We suggest that the Majingzi two-mica granites exposed by the Jiajika gneiss dome is analogous to the deeper granitic sheet implied by the 3 km deep drilling, which both are strongly peraluminous S-type granites with a highly fractionation. Based on the degree of evolution of the Li-rich, Li-poor pegmatites and the two-mica granites and other geochemical evidence, we used a Rayleigh fractionation model to reproduce Li isotope variations in different types of rocks around the Jiajika deposit, suggesting an extreme magmatic differentiation without significant fluid exsolution as the origin for Li enrichments in pegmatites.

Lithium Isotope Determination in Spodumene by fs‐LA‐MC‐ICP‐MS with Non‐Matrix‐Matched Calibration: Insights into ICP Operating Conditions and Data Evaluation

Lithium isotope measurement in spodumene by femtosecond LA‐MC‐ICP‐MS was investigated and the influence of plasma operating conditions and data reduction strategy on accuracy and precision was studied. It was found that “hot” plasma conditions led to an unstable baseline signal and substantial variations in the Li isotope ratios. By adding a constant amount of water to the carrier gas, a stable baseline was achieved and isotope ratios became reproducible and were consistent with data from solution‐based MC‐ICP‐MS. The resulting biases were within ± 0.51‰ and the reproducibility was better than 0.09‰. Comparison of Li isotope ratios resulting from different data evaluation schemes showed that the mean of the transient intensity ratios, integration of the entire or a user‐defined period of the ion signals resulted in good agreement with solution‐based data, while linear regression underestimated the Li isotope ratios. It was also found that “cool” plasma operation produced a stable baseline signal, but the Li isotope results were biased by up to ‐4.3%, irrespective of water introduction and the data evaluation scheme. With the optimised “hot‐wet” conditions, the Li isotope ratios in eleven spodumene materials were determined which successfully allowed distinguishing regional deposits and partially veins of the available samples.

Composition and constraints of lithium isotopes in cryoconite from various remote glacier areas of the Tibetan Plateau

Lithium isotope is one of the most promising indicators for the study of continental silicate weathering, and lithium concentrations and its isotopic compositions in earth surface can provide a better understanding of the geochemical behavior and isotopic fractionation during weathering and erosion. This work focused on the composition and distribution of Li isotope in cryoconite deposited on various glacier areas in a large range of the Tibetan Plateau and surroundings, as well as its implications for cryoconite dust provenances. Results showed that δ7Li in cryoconite varied within the same order of magnitude (−2.14 ‰-7.74 ‰), which is characterized by geographic distribution of higher δ7Li value of cryoconite in northern glaciers (e.g. Yuzhufeng Glacier), and lower δ7Li value in southern glaciers. In comparison with other global materials, the cryoconite dust shows a lighter δ7Li isotopic composition due to constraints of climatic conditions and land surface weathering intensity. Compared with dust materials in the surrounding Asian dust sources (e.g. large deserts and Gobi), we find that, the primary sources of Li isotope in cryoconite of the northern locations were from both local dust/soils of the TP surface and the surrounding large deserts. Moreover, the products of anthropogenic activities (e.g. coal-burning) may also influence the isotopic composition of the cryoconite dust, and Li isotope may serve as potential tracers of anthropogenic source activities. Therefore, this work provides a complete view of the composition and distribution of Lithium isotopes in cryoconite from various glacier areas of the Tibetan Plateau, and the research significance of its transport processes and source constraints of Li isotopes in cryoconite is proposed.