Separation and Precise Measurement of Lithium Isotopes in Three Reference Materials Using Multi Collector-Inductively Coupled Plasma Mass Spectrometry

Lithium separation technique for three reference materials has been established together with precise determination of lithium isotope using a Neptune multi collector-inductively coupled plasma mass spectrometry （MC-ICP-MS）. The solutions of lithium element standard reference materials, potassium, calcium, sodium, magnesium and iron single element, were used to evaluate analytical methods applied. Three separate stages of ion-exchange chromatography were carried out using organic cation-exchange resin （AG 50W-X8）. Lithium was enriched for the three stages using different eluants, which are 2.8 M HCl, 0.15 M HCl and 0.5 M HCl in 30% ethanol, respectively. The columns for the first and second stages are made of polypropylene, and those for the third stage are made of quartz. Total reagent volume for the entire chemical process was 35 mL for three reference materials. The recovery yielded for the three stages is 98.9-101.2% with an average of 100.0%, 97.6-101.9% with an average of 99.9%, and 99.8-103.3% with an average of 100.6%, respectively. The precision of this technique is conservatively estimated to be ±0.72-1.04‰ （2σ population）, which is similar to the precision obtained by different authors in different laboratories with MC-ICP-MS. The δ7 Li values （ 7 Li/ 6 Li relative to the IRMM-016 standard） determined for andesite （AGV-2） and basalt （BHVO-2） are 5.68‰ （n=18）, 4.33‰ （n=18）, respectively. The δ7 Li value （ 7Li/6Li relative to the L-SVEC standard） determined for IRMM-016 is -0.01‰ （n=15）. All these analytical results are in good agreement with those previously reported. In addition, the results for the same kinds of samples analyzed at the MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, are consistent with those obtained at the Plasma Laboratory, University of Maryland, within analytical uncertainty. According to these experiment results, it is concluded that this proposed procedure is a suitable method for determining the lithium isotopic composition of natural samples.

Geochemical behavior of lithium isotopes in a small mountainous river of the Tibetan Plateau:A case study from Niyang River

Lithium(L_(i))and its isotopes are potential tracers of silicate weathering in river basins.However,the relationship between the Li isotopic composition(δ~7Li)in rivers and silicate weathering intensity remains unclear.This study analyzed the Li concentration and isotopic composition in river waters from the Niyang River,southern Tibetan Plateau.The results show that these samples have significantly variable Li concentrations(0.31–7.4μg/L)andδ~7Li values(+7.0–+20.7‰,n=28),and highδ~7Li values are found in several tributaries.Calculations indicate that dissolved Li in river water is predominantly derived from silicate weathering and geothermal water.With the exception of certain tributaries,geothermal water contributes 68%to 85%of the dissolved Li.Geothermal waters have lowδ~7Li values(-0.9–+2.9‰)in the Tibetan Plateau.Differences in the proportional contribution of dissolved Li in river samples from silicate weathering and geothermal water may be the main reason for the spatiotemporal variation in riverineδ~7Li values.The samples have higherδ~7Li values when the dissolved Li in the water samples is mainly derived from silicate weathering contributions,and lower values when the contribution from geothermal waters is high.Furthermore,the interaction of dissolved Li from geothermal water with secondary minerals results in Li isotopic fractionation,which may contribute to variations in river waterδ~7Li.It is accepted that the lower weathering intensity in orogenic(or mountainous)belts compared to floodplains is the main controlling factor for lowerδ~7Li values in the rivers.This study indicates that geothermal water input may cover the Li isotope signal of silicate weathering in river water,which in turn,affects the accurate understanding of the relationship between riverineδ~7Li values and the silicate weathering intensity.Therefore,whether the lowerδ~7Li values of river waters in hydrothermal-rich orogenic belts are mainly controlled by the regional weathering intensity or the input of hot springs(or both)requires in-depth study,and this is the key to accurately establishing the relationship between the Li isotopic composition and silicate weathering intensity in the river basin.

Using lithium isotopes to quantitatively decode continental weathering signal:A case study in the Changjiang(Yangtze River)Estuary

As the key link connecting the earth’s spheres,continental weathering plays an important role in regulating the global biogeochemical cycle and long-term climate change.Siliciclastic sediments derived from large river basins can record continental weathering and erosion signals,and are thus widely used to investigate weathering processes.However,sediment grain size,hydrodynamic sorting and sedimentary recycling complicate the interpretation of sediment weathering proxies.This study presents elemental and lithium isotope compositions of estuarine surface sediments(SS)and suspended particulate matters(SPM)collected from the Changjiang(Yangtze River)Estuary.Based on a simple mass balance model,the proportions of different end-members(i.e.,igneous rocks,modern weathering products and inherited weathering products)in sediments were quantitatively calculated and thus the silicate weathering process can be estimated.Overall,the sediments in the Changjiang Estuary are mainly eroded from un-weathered rock fragments(>60%),while modern weathering products account for less than 40%.The fine-grained SPM contain more shale components(52–66%),and the modern weathering products account for 21–40%.Comparatively,the coarse-grained surface sediments contain more un-weathered igneous rock fragments(63–84%)and less modern weathering products(only 4–18%).The comparison ofδ^(7)Li values with the weathering proxy(Chemical Index of Alteration,CIA)suggests that sediment weathering intensity declines with increasing proportion of un-weathered igneous rock fragments.Additionally,the occurrence of inherited weathering products(i.e.,shale)in modern sediments makes it a challenge to simply use CIA andδ^(7)Li as indicators of weathering intensity.This study confirms that fine-grained particles are more suitable for tracing contemporary weathering process,albeit with the influence of sedimentary recycling.Lithium isotopes combining with the mass balance model can quantitatively constrain the continental weathering processes in large river basins.

Isotope shift calculations for D lines of stable and short-lived lithium nuclei

The isotope shifts（TSs） for the 2s2S（1/2） to 2p2PJ（J = 1/2,3/2） transitions of the lithium nuclei including the stable and short-lived isotopes are calculated based on the multi-configuration Dirac-Hartree-Fock method and the relativistic configuration interaction approach.The results are in good agreement with the previous theoretical and experimental results within a deviation less than 0.05%.The methods used here could be applied to the IS calculations for other heavier Li-like ions and few-electron systems.

Problems of Lithium Isotope Research in Salt Lake Study

Lithium in nature mainly exists in the forms of solid minerals and ionic liquid.More than 150 lithium minerals exist,which are mainly pegmatite mineral including triphane,lithionite and petalite.Liquid lithium mainly

Contrasting sources and enrichment mechanisms in lithium-rich salt lakes:A Li-H-O isotopic and geochemical study from northern Tibetan Plateau

Lithium(Li),a crucial mineral resource for modern high-tech industries,is notably abundant in the northern Tibetan Plateau,primarily within lithium-rich salt lakes.However,the exploration and development of these resources are hindered due to an incomplete understanding of their nature and origin.Here we present results from a comprehensive study on the hydrochemical parameters,whole-rock geochemistry,H-O isotopes,and Li concentrations in surface brine,river water,geothermal springs,and associated rocks from two representative lithium-enriched salt lakes,the Laguo Co(LGC)and Cangmu Co(CMC)in Tibet to understand the genetic mechanisms.Our water-salt balance calculations and H-O isotopic analysis reveal that Li in LGC and CMC primarily originates from the Suomei Zangbo(SMZB,~91%)and Donglong Zangbo(DLZB,~75%)rivers,respectively.It is estimated that the LGC and CMC took a minimum of 6.0 ka and 3.0 ka to accumulate their current lithium resources,respectively.The distinct geological characteristics reflect evolutionary differences between the two lakes,suggesting diverse lithium sources and enrichment processes.The high lithium ion concentration and light lithium isotope composition in the SMZB river waters indicate the genetic relationship with lithium-enriched geothermal springs in the Tibetan Plateau.Our results suggest that lithium in the LGC originates from lithium-enriched geothermal springs and is primarily supplied through the small-scale SMZB river.In contrast,the formation and evolution of CMC are influenced by the northern Lunggar rifts,receiving a prolonged and stable input from the DLZB,resulting in high lithium concentrations and isotopic values.The absence of lithium-enriched geothermal springs and the prevalence of silicate rocks in the CMC catchment suggest that lithium may be sourced from the weathering of silicate rocks,such as granitic pegmatite veins containing lithium-rich beryl,widely distributed in the upstream area of DLZB.The forward modeling approach,quantifying the contribution fractions of different reservoirs(atmospheric precipitation,silicate,carbonate,and evaporite),indicates that the distinct lithium concentrations in the mainstream(>1 mg/L)and tributaries(<0.1 mg/L)are positively correlated with the ratio of silicate contributions to carbonate contributions,suggesting that dissolved lithium in river waters primarily originates from the weathering and dissolution of silicate rocks.The distinct sources and enrichment mechanisms of lithium in these two salt lakes are attributed to various evolutionary processes,topographical features,hydrological factors,fundamental geological settings,and tectonic histories,despite their spatial proximity.Furthermore,our study highlights the significant role of rivers in the formation of young salt lakes,in addition to geothermal springs.