High-precision double-spike Cd isotopic measurements of seawater by MC-ICP-MS and its application to seawater affected by hydrothermal vent fluids

Cadmium(Cd)isotopes in seawater have been proven as an important geochemical tool for tracing ocean Cd circulation in the modern ocean.In this study,we evaluated a new method to separate Cd(*60 ng)from seawater using Chelex resin(1.0 g)coupled with AG-MP-1M resin.The results show that the Chelex resin is suffi-cient to remove Cd from Na and Mg matrix with Cd recoveries at 98.3±3.5%(2SD,N=6);while AG-MP-1M resin could separate Cd from the residual Na,Mg,and isobaric inferences.The total Cd recoveries of the method are 96.3±1.5%(2SD;N=4)and the salinity of the samples has no significant impacts on Cd recovery.Cd isotope ratios were measured using a Nu PlasmaⅢMC-ICP-MS and^(111)Cd–^(110)Cd double spike technique.By comparing theδ^(114/110)Cd values(0.00±0.06%)of synthetic seawaters doped with Cd isotope standard(NIST-3108;treated by Chelex+AG-MP-1M resin)and the reference value(-0.00%),no variations were observed.We also analyzed the Cd isotope compositions of three deep seawaters from a column at the Southwest Indian Ocean Ridges(SWIR).Theδ^(114/110)Cd values of the col-umn are decreased from 1.05±0.05%at 3200 m to 0.36±0.05%at 2800 m,differing from reportedδ^(114/110)Cd values of deep seawater in other oceans.Considering the spatial distance between the column and active hydrothermal vents in SWIR(-13 km),we propose that such positiveδ^(114/110)Cd values of deep seawater were likely contaminated by vent fluids,which could provide heavy Cd isotope to deep seawaters.This study demon-strates that Cd isotope is more sufficient to distinguish the impact of plumes on deep seawater.

Cadmium isotopic constraints on metal sources in the Huize Zn–Pb deposit, SW China

The Sichuan–Yunnan–Guizhou(SYG)Zn–Pb metallogenic zone in SW China contains>400 carbonatehosted hydrothermal Zn–Pb deposits.Some of these,such as the Huize,Tianbaoshan,and Daliangzi deposits,are super-large deposits with significant reserves of Cd,Ge,and Ag.However,the sources of these metals remain controversial.This study investigated the Cd isotopic geochemistry of the Huize deposit,the largest Zn–Pb deposit in the SYG area.Sphalerites formed at three stages in the deposit have different colors:black or dark brown(Stage I),red(Stage II),and light-yellow(Stage III).The d^(114/110)Cd values of the sphalerites are in the order Stage III<Stage I<Stage II.Kinetic isotopic fractionation is likely the key factor causing the lower δ^(114/110)Cd values in the early formed Stage I sphalerites than in laterformed Stage II sphalerites,with cooling of ore-forming fluids being responsible for the still lower values of the Stage III sphalerites.In galena,the δ^(114/110)Cd values are inversely correlated with Cd contents and tend to be higher in high-Zn galena.We speculate that Cd isotopic fractionation was significant during the precipitation of sphalerite and galena,with light Cd isotopes being enriched in galena rather than sphalerite.Comparison of the Cd isotopic signatures and Zn/Cd ratios of different endmembers suggests that the δ^(114/110)Cd values and Zn/Cd ratios of sphalerite from the Huize deposit,as well as other largescale deposits from the SYG area,are lie in those range of Emeishan basalts and sedimentary rocks and the mean δ^(114/110)Cd values of these deposits show good negative correlation with 1/Cd,suggesting that the ore-forming materials of these deposits were derived from the mixing of Emeishan basalts and sedimentary rocks.This study demonstrates that Cd isotopes can be useful proxies in elucidating ore genesis in large Zn–Pb deposits.

Application of SYNTAX and its Derivative Scores in the Selection of Revascularization Strategies for Complex Coronary Heart Disease

Complex coronary heart disease(CHD)has become a hot spot in medicine due to its complex coronary anatomy,variable clinical factors,difficult hemodynamic reconstruction,and limited effect of conservative drug treatment.Identifying complex CHD and selecting optimal treatment methods have become more scientific as revascularization technology has improved,and coronary risk stratification scores have been introduced.SYNTAX and its derivative scores are decision-making tools that quantitatively describe the characteristics of coronary lesions in patients based on their complexity and severity.The SYNTAX and its derivative scores could assist clinicians in rationalizing the selection of hemodynamic reconstruction treatment strategies,and have demon-strated outstanding value in evaluating the prognosis of patients with complex CHD undergoing revascularization treatment.The authors in this article summary the practical application of SYNTAX and its derivative scores in complex CHD in order to deepen the understanding of the relationship between the choice of different revascularization strategies and SYNTAX and its derived scores in complex CHD and provide a further reference for clinical treatment of complex CHD.

Ga isotopic fractionation in sulfides from the Yuhuang and Duanqiao hydrothermal fields on the Southwest Indian Ridge

This study examines the Ga isotopic compositions of sulfides in the Yuhuang and Duanqiao hydrothermal fields on the Southwest Indian Ridge,mid-ocean ridge basalts(MORB),and calcareous sediments around the hydrothermal fields.Theδ^(71/69)Ga_(NIST-994) values of theMORB samples vary little(+1.20‰to+1.23‰,with an average of+1.22‰)and are consistent with the δ^(71/69)Ga_(NIST-994) values of two standard basalt samples(BCR-2 and BHVO-2),indicating that Ga isotopes may either not fractionate or fractionate only slightly under high-temperature geological processes;therefore,the δ^(71/69)Ga_(NIST-994) value of oceanic crust may be+1.22‰.The sediments(+1.28‰to+1.47‰,with an average of+1.38‰)are rich in heavier Ga isotopes than the basalts,and the Ga present in the sediments may have originated from soluble Ga present in the seawater that was adsorbed by(Mn,Fe)oxides/hydroxides.The Ga contribution of basaltic debris to the sedimentswas almost negligible.Thus,wespeculate that theδ^(71/69)Ga_(NIST-994) value of seawater in the study area fell within a range from+1.92‰to+2.36‰.Theδ^(71/69)Ga_(NIST-994) values of the sulfides in the Yuhuang hydrothermal field range from+0.99‰to+1.57‰,with an average of+1.25‰,and theδ^(71/69)Ga_(NIST-994) values of the sulfides in the Duanqiao hydrothermal field range from+0.93‰to+1.55‰,with an average of+1.19‰.Theδ^(71/69)Ga_(NIST-994) ranges of the sulfides in the Yuhuang and Duanqiao hydrothermal fields are similar,with the Ga isotopic fractionation reaching 0.58‰and 0.62‰,respectively.The averageδ^(71/69)Ga_(NIST-994) values in the sulfides are close to those in the MORBs.This suggests that Ga within the sulfides in the Yuhuang and Duanqiao hydrothermal fields mainly originated from MORBs,with seawater and sediments making only small contributions.The Ga isotopic fractionation in the sulfides may be related to processes associated with the formation of sulfides,such as rapid precipitation or the admixture of different stages of sulfide.This study is of great significance for understanding the global distribution of Ga isotopes and the Ga cycle in submarine hydrothermal systems.