Zn Isotope Data Research Articles

Fluid-mediated Cu and Zn isotope fractionation in subduction zones and implications for arc volcanism: Constraints from high pressure veins within eclogites in the Dabie Orogen

High-pressure (HP) veins in eclogites are the products of fluid-rock interaction and provide insight into the composition and evolution of fluids in subduction zones. We here present the Cu and Zn isotope data for different types of HP veins and their host eclogites from Ganghe and Hualiangting in the Dabie Orogen to reveal the behavior of Cu and Zn isotopes during fluid-rock interaction and fluid evolution. The HP veins include omphacite-epidote (Omp-Ep), epidote-quartz (Ep-Qtz), and kyanite-epidote-quartz (Ky-Ep-Qtz) veins. The Omp-Ep veins first crystallized from eclogite-derived, solute-rich fluids with the Ep-Qtz and Ky-Ep-Qtz veins successively crystallizing from the residual fluids after the Omp-Ep vein formation. The early Omp-Ep veins have variably lower δ65Cu (−1.32 to −1.12‰ at Ganghe, −0.70 to −0.66‰ at Hualiangting) but higher δ66Zn (0.36 to 0.38‰ at Ganghe, 0.40 to 0.41‰ at Hualiangting) relative to the host eclogites (δ65Cu: −0.71 vs. 1.84‰, δ66Zn: 0.22 vs. 0.33‰), indicating CuZn isotope fractionation during slab dehydration in subduction zones with the lighter Cu and heavier Zn isotopes preferentially entering the vein-forming fluids from the eclogites. Systematic increase of δ65Cu from the Omp-Ep (−0.70 to −0.66‰) through Ep-Qtz (0.01‰) to Ky-Ep-Qtz veins (0.46 to 0.95‰) can be attributed to isotope fractionation induced by redox changes during the evolution of metamorphic fluids, as revealed by the negative correlations of δ65Cu with redox-sensitive ratios of Fe3+/ΣFe and (Eu/Eu*)N in those veins. Additionally, the higher δ66Zn of the Omp-Ep veins relative to the Ky-Ep-Qtz veins can be explained by equilibrium isotope fractionation between crystallized minerals and evolved metamorphic fluids. Our results thus demonstrate that CuZn isotope fractionation occurred during the evolution of slab-derived metamorphic fluids in subduction zones. Binary mixing calculations show that fluids derived from dehydration of mafic rocks in subducted slabs, represented by the multistage HP veins in the present study, cannot account for the heavier Cu and lighter Zn isotope compositions in most arc magmas than in mid-ocean ridge basalts. This offset can be resolved by addition of forearc serpentinite-derived fluids enriched in heavy Cu and light Zn isotopes into the mantle source of arc magmas.

Copper and zinc isotope compositions of pristine eucrites as analogues for differentiated planetary feedstocks

Preferential enrichment of the heavier isotopes of moderately volatile elements (MVE) in samples from asteroids and the Moon have been attributed to volatile loss during the formation and differentiation of their parent bodies. Analogs for planetary feedstocks include the howardite-eucrite-diogenite meteorites, which originate from a differentiated planetesimal or planetesimals, likely including (4) Vesta. Complications arise in the interpretation of volatile depletion in these meteorites, however, due to post-crystallization processes including metamorphism and later impacts that acted upon them. We present new coupled Cu and Zn isotope data for a suite of eucrites that, when combined with published data, show significant ranges (δ65Cu = -1.6 to +0.9‰; δ66Zn = -7.8 to +13.5‰). Exclusion of eucrites that have been affected by metamorphism, impact contamination or surface condensation of isotopically light Zn and Cu leads to a range of ‘pristine’ compositions (δ66Zn = +1.1 ± 2.3‰; δ65Cu = +0.5 ± 0.5‰; 2 St. Dev.), implying inherent MVE variability within the eucrite parent body. As low-mass differentiated bodies, Vesta and the Moon represent endmembers in planet evolution. For the Moon, extensive volatile loss can be explained by a cataclysmic giant impact origin and later magma ocean crystallization. In contrast the parent body of eucrite meteorites likely heterogeneously lost volatile elements and compounds during differentiation. Vesta as the potential source of eucrite meteorites offers an important endmember composition for likely feedstocks to planets, representing the remaining vestige of what was likely to have been a larger population of differentiated objects in the inner Solar System shortly after nebula accretion. Mixing contributions of non-carbonaceous and carbonaceous chondrites constrained by nucleosynthetic Zn isotope anomalies suggests a significant fraction of Earth's accretion could have come from volatile-poor and differentiated planetary feedstocks that would have had limited effects on the bulk silicate Earth (BSE) Zn isotope composition. Furthermore, volatile-poor feedstocks cannot explain the BSE Cu isotope composition, which instead may have been modified by terrestrial core formation. Pristine eucrites offer key insights into early planetesimal differentiation and the role of volatile loss on small mass bodies within nascent solar systems.

Tracing Subducted Carbonates in Earth's Mantle Using Zinc and Molybdenum Isotopes

AbstractAlthough carbonates are the primary form of carbon subducted into the mantle, their fate during recycling is debated. Here we report the first coupled high‐precision Zn and Mo isotope data for Cenozoic intraplate basalts from western China. The exceptionally high δ66Zn values (+0.39 to +0.50‰) of these lavas require involvement of recycled carbonates in the mantle source. Variable δ98Mo compositions (−0.39 to +0.27‰) are positively correlated with Mo/Ce, best interpreted as mixing between isotopically light Mo from dehydrated oceanic crust and heavy Mo from recycled carbonates, which is also supported by positive coupling between δ66Zn and δ98Mo. Modeling reveals that involvement of ≤5% carbonate‐bearing oceanic crust fully resolves the observed δ66Zn–δ98Mo mantle heterogeneity probed by intracontinental basalts. Our study demonstrates that combined δ66Zn–δ98Mo data sets for mantle‐derived magmas can track recycled surficial carbonates in Earth's interior, providing a powerful geochemical tool for deep carbon science.

Zinc Isotope Measurement by MC‐ICP‐MS in Geological Certified Reference Materials

Here we present an analytical method for Zinc (Zn) isotopic measurements using “standard‐sample bracketing” on a Nu Sapphire multi‐collector inductively coupled plasma‐mass spectrometer. The effects of Zn mass fraction and HNO3 molarity mismatch between the standard and the sample, as well as the presence of matrix elements have been evaluated. Long‐term reproducibility of better than ±0.03‰ for δ66Zn (2s) was routinely obtained. Accurate measurements were achieved when CNi/CZn < 0.001, CTi/CZn < 0.03, CBa/CZn < 0.05, CNa/CZn and CAl/CZn < 0.5, CMg/CZn < 0.1, CFe/CZn < 5 and CCu/CZn as well as CCd/CZn < 10. High‐precision Zn isotopic determination were performed on twenty‐one widely available geological certified reference materials, with an overall range of ~ 0.62‰ (0.15 to 1.07‰), which is nearly twenty times the current analytical precision (0.03), and the results are in agreement with most previously published data within 2s. Among them, δ66ZnJMC 3‐0749L of eleven geological certified reference materials are reported for the first time: 0.22 ± 0.03‰ (dolerite, DR‐N), 0.23 ± 0.02‰ (gabbro, GSR‐10), 0.20 ± 0.04‰ (microgabbro, PM‐S), 0.15 ± 0.02‰ (andesite, GSR‐2), 0.22 ± 0.08‰ (diorite, GSR‐9), 0.19 ± 0.07‰ (syenite, GSR‐7), 0.30 ± 0.06‰ (granite, GSR‐1), 0.25 ± 0.00‰ (rhyolite, GSR‐11), 0.37 ± 0.01‰ (shale, GSR‐5), 0.21 ± 0.03‰ (limestone, GSR‐6) and 0.20 ± 0.03‰ (hornblendite, GSR‐15). The novel Zn isotopic data from these certified reference materials can be used for future interlaboratory comparisons.

An inner solar system origin of volatile elements in Mars

The origin of volatile elements in Mars and whether these elements derive from the inner or outer solar system is unclear. Here we show that Mars exhibits nucleosynthetic zinc (Zn) isotope anomalies similar to those of non‑carbonaceous (NC) but distinct from carbonaceous (CC) meteorites. Like for non-volatile elements, Mars' Zn isotope composition is intermediate between those of enstatite and ordinary chondrites, demonstrating that Mars acquired volatile elements predominantly from its inner solar system building blocks. The Zn isotope data limit the contribution of CI chondrite-like material to Mars to 4% by mass at most and show that Mars accreted less CC material than Earth. The origin of these disparate CC fractions is unclear, but can place constraints on how and when CC-type material was delivered to the inner solar system.

Zinc isotope fractionation during mid-ocean ridge basalt differentiation: Evidence from lavas on the East Pacific Rise at 10°30′N

Zinc (Zn) isotope data for mid-ocean ridge basalts (MORB) are scarce. The possible effects of MORB differentiation and mantle compositional heterogeneity on MORB Zn isotope compositions are poorly understood. In this paper, we report Zn isotope data of MORB lavas from the East Pacific Rise (EPR) at 10°30′N, which are understood to have been derived by a similar extent of melting from a compositionally uniform mantle source but manifest significantly varying extents of magma differentiation (MgO = 7.38–1.76 wt%) to demonstrate unequivocal Zn isotope fractionation during MORB differentiation. These lavas have a small δ66Zn (relative to the JMC-Lyon standard) range of 0.21–0.32‰, with an average of 0.26 ± 0.07‰ (2SD, N = 24), overlapping with literature data. However, δ66Zn values show significant correlations with indices of magma differentiation (e.g., MgO and CaO), with the more differentiated samples having isotopically heavier Zn. We can thus conclude that MORB differentiation can lead to ∼0.1‰ δ66Zn elevation, which is similar to that observed in Hawaiian Kilauea Iki lava lake samples. Fractional crystallization of olivine and clinopyroxene at MgO > ∼3.5 wt% and clinopyroxene and Fe–Ti oxides dominated by ilmenite at MgO < ∼3.5 wt% results in the observed Zn isotope fractionation. The δ66Zn values for primitive N-MORB and MORB source mantle are estimated to be ∼0.22‰ and ∼0.17‰, respectively. Furthermore, we observe a positive correlation between δ66Zn and [La/Sm]N in primitive (MgO = 7.58–9.01 wt%) literature MORB, indicating the existence of possible Zn isotope heterogeneity in the oceanic upper mantle. We thus predict heavy Zn isotope enrichment in mantle sources for E-MORB samples with high [La/Sm]N, which requires future testing.

Investigation of metasomatism using Cu, Zn and Fe stable isotopes: Rodingitization of mafic and ultramafic rocks in ophiolites from northern Greece

Rodingites, a high-Ca content variety of metasomatic rocks, have been found in the Veria-Naousa and Edessa ophiolites, in northern Greece. The rodingites from both areas are characterized by a substantial overprint of primary textures. Coupled field and petrographic observations reveal derivation from ultramafic and mafic protoliths. The mineral phases in the ultramafic-derived rodingites (UDR) include mainly diopside, garnet, chlorite, tremolite, and FeTi oxides whereas mafic-derived rodingites (MDR) contain diopside, garnet, vesuvianite, chlorite and quartz. Here we present, for the first time, whole rock Cu, Zn and Fe isotopic data for the UDR and MDR from the Veria-Naousa and Edessa ophiolites, to investigate the evolution of this peculiar metasomatic lithotype. All the studied rodingites present δ65Cu values varying from −0.17 ± 0.03‰ to +0.62 ± 0.05‰ and δ66Zn ranging from −0.06 ± 0.03‰ to +0.74 ± 0.06‰. 0.0. Copper isotope ratios are systematically heavier in rodingites compared to their respective protoliths whereas Zn shows a diverse behavior with enrichment in its light isotopes (group 1: comprising all the UDR and a MDR sample) or in its heavy isotopes (group 2, the rest MDR samples). The same gabbroic protolith can lead to both group 1 and 2 rodingites with respect to their Zn isotopic ratios. Alkaline conditions of the hydrothermal metasomatic fluids and the inferred sulfide and bisulfide ligands promoted mobility of Cu and Zn and have likely played a major role to their isotopic behavior in the rodingites. In contrast, Fe isotopes have not fractionated during rodingitization. Complex metasomatic processes, such as rodingitization, have a clear impact on stable isotope fractionation, which is decoupled between the Cu, Zn and Fe isotope systems. The lack of correlation between isotope ratios and any mineralogical or elemental indicator highlights the absence of any profound relationship between isotope fractionation and mineral phases, which could reflect the stage and evolution of rodingitization. The consistent isotopic behavior of Cu indicates a promising geochemical tool to distinguish metasomatized and non-metasomatized samples within different observed groups, and define conditions and parameters during Ca-metasomatism, regardless the degree of rodingitization, prior alteration and various protoliths compositions. Additionally, Zn isotopes give a useful insight on the metasomatic conditions for both ultramafic and mafic precursors defining local pH changes coupled with available ligands, HS−, where Cu isotopes alone would not be able to describe.

Sedimentary cycling of zinc and nickel and their isotopes on an upwelling margin: Implications for oceanic budgets and paleoenvironment proxies

Zinc and Ni are essential micronutrients whose stable isotope systematics in marine sediments represent promising, but still developing, tracers of past ocean chemistry and biology. Sediments from upwelling continental margins have been identified as important sinks for Zn and Ni, driven by high productivity, incorporation of the metals into cells and organic carbon burial. At present, however, our understanding of how Zn and Ni isotope composition of upwelling sediments reflects specific processes in the water column is incomplete. Here, we present coupled Zn and Ni abundance and isotope data for both solid phase and porewater in a series of sediment cores collected on a shelf-to-slope transect across an oxygen minimum zone (OMZ) from the southwest African margin off Namibia.Zinc/Al and Ni/Al ratios in Namibian margin sediments are elevated relative to the lithogenic background, by factors of 1.4–2.4 and 1.7–5.7, respectively. Systematic relationships between solid phase Zn and Ni concentrations and organic carbon accumulation corroborate the view that authigenic Zn and Ni are mainly delivered to these sediments via export production from the photic zone. Corrections for detrital Ni are sometimes substantial, but authigenic δ60Ni values are within uncertainty of the modern deep ocean, at 1.38 ± 0.18 ‰ (mean and 1SD, n = 42). Authigenic δ66Zn is more variable, at −0.09 to 0.50 ‰, at or below the value for the deep ocean average. This latter observation can be attributed to Zn isotope fractionation during sequestration into authigenic ZnS phases in the sediments, either quantitatively, or partially.Porewater systematics are more complex and the profiles do not necessarily reflect the redox state of the sediment-porewater system at the time of sampling, but rather characteristics inherited from more reducing conditions in a temporally heterogeneous system. Porewater zinc concentrations (30–369 nM) are much higher than the deep ocean and increase with depth beneath the sediment–water interface. Despite this prominent increase in Zn concentrations, δ66Zn is rather constant and lighter than the deep ocean average, at 0.18 ± 0.06 ‰ (mean and 1SD, n = 33). These observations are most consistent with the buffering of the small porewater pool by the dissolution of a previously formed sulfide phase. Porewater Ni concentrations are closer to the deep ocean, mostly at 5–15 nM. The lightest porewater isotope compositions (δ60Ni as low as 0.15 ‰) are consistent with a Mn-oxide source of Ni, whereas the heaviest isotope compositions (up to 1.76 ‰) clearly reflect uptake of light Ni into sulfide at depth within the sediment.Our data, for the largest upwelling site in the modern ocean, add to sparse data from the eastern Pacific, and confirm that upwelling margin sediments bury Ni that is close to the deep ocean in isotope composition, but Zn that is generally lighter. The data thus confirm the importance of such margins in setting the heavy isotope composition of oceanic Zn. Sediments from this kind of setting hold significant potential for the construction of records of past oceanic Ni isotopes.

Mg and Zn isotopic data and supplementary information for "Recycled carbonate-bearing silicate sediments in the sources of circum-Mediterranean K-rich lavas: Evidence from Mg-Zn isotopic decoupling".

Mg and Zn isotopic data and supplementary information for "Recycled carbonate-bearing silicate sediments in the sources of circum-Mediterranean K-rich lavas: Evidence from Mg-Zn isotopic decoupling".

Speciation and isotopic analysis of zinc in size-fractionated aerosol samples related to its source and chemical processes

Zinc (Zn) in aerosols plays important roles for biological activity and attracts public attention from the perspective of environmental measures. Because of its high volatility and water solubility, Zn is readily released into the atmosphere by human activities and supplied to natural water. To explore the origin and formation process of Zn in atmospheric aerosols, it is important to investigate isotopic (= δ66Zn) and speciation information of Zn in size-fractioned aerosols. We measured light δ66Zn (e.g., δ66ZnIRMM = −1.32‰ as the lowest value; IRMM-3702 is used for the normalization in this study) mainly for the particles ranging from 0.65 to 4.7 μm for the samples collected at Tsukuba, Chiba, and a motorway tunnel (Yasumiyama Tunnel in Hiroshima) in particular for the samples collected in 2002, but δ66ZnIRMM in the particle sizes increased above −0.8‰ for the samples collected in 2011 and 2016. Zn species in aerosols were estimated based on X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, suggesting that (i) Zn oxalate and sulfate and (ii) Zn oxide, sulfide, and carbonate are main Zn species in fine and coarse particles, respectively. In particular, Zn chloride was found mainly in the middle particle size range (2.1–4.7 μm), which corresponds to the range with light δ66Zn, suggesting that the light δ66Zn was caused by emission of Zn chloride during artificial combustion processes in accordance with other studies. The origins of Zn in aerosols are assumed to have three endmembers; (A) tire and brake wears and road dust, (B) industrial emissions, and (C) vehicular exhaust. Their formation mechanisms are related to vaporization and mixing processes based on the results of combined analysis of atmospheric concentration, speciation, and isotopic composition of Zn with different particle sizes. These trends could be successfully interpreted by species-specific δ66Zn values: component (A) consisting mainly of Zn oxide and sulfide with relatively heavier δ66Zn, component (B) Zn chloride and sulfate secondarily formed in the droplet mode having lightest δ66Zn among all the species, and (C) Zn oxalate with δ66Zn closer to 0‰ due to its emission by the complete combustion in vehicle engines. Species-specific Zn isotope data obtained by the simultaneous application of speciation and isotopic analyses of Zn in size-fractionated aerosols complementary provide novel information on the initial generation and secondary processes for the formation of Zn species in the aerosols.

The cadmium and zinc isotope compositions of the silicate Earth – Implications for terrestrial volatile accretion

Zinc and Cd isotope compositions are presented for a comprehensive suite of terrestrial rocks to constrain the extent of Zn and Cd isotope fractionation during igneous processes and better define the δ66Zn and δ114Cd values of the silicate Earth (the δ values denote per mille deviations of 66Zn/64Zn from JMC Lyon Zn and of 114Cd/110Cd from NIST SRM 3108 Cd). Analyses of spinel lherzolites provide a bulk silicate Earth (BSE) δ114CdBSE value of –0.06 ± 0.03 ‰ (2SD). For Zn, the peridotite data of the current and previous studies define a mean δ66ZnBSE = 0.20 ± 0.05 ‰ (2SD). Komatiite analyses of this and published investigations yield similar mean values, which suggests that the Zn and Cd isotope compositions of the mantle remained fairly constant since the Archean. Data for loess provide upper continental crust compositions of δ114Cd = 0.03 ± 0.10 ‰ and δ66Zn = 0.23 ± 0.07 ‰. The Zn isotope and abundance data for peridotites and oceanic basalts are in accord with the previous observation of a mantle array, with basalts having higher Zn concentrations and δ66Zn values than the peridotites. To a first order, this reflects slightly incompatible behaviour of Zn during mantle melting and melt differentiation with associated enrichment of heavy Zn isotopes in the melt phase. Cadmium is marginally more incompatible than Zn during igneous processes and the oceanic basalts also display a minor enrichment of heavy Cd isotopes relative to peridotites. However, secondary processes produce significant Cd isotope variability in both mantle melts and peridotites, obscuring the primary igneous array. The δ66ZnBSE estimates of this and previous studies resemble the Zn isotope compositions of CV and CO carbonaceous and some enstatite chondrites. In contrast, the BSE has a lower δ114CdBSE value than enstatite and carbonaceous chondrites. This implies that the Cd isotope composition of the BSE was either fractionated during accretion or that Earth’s Cd inventory was not exclusively acquired from material related to carbonaceous and enstatite chondrites. Importantly, delivery of Zn and Cd to the BSE solely by CI and CM chondrites is not in accord with the meteorite and terrestrial stable isotope data of these elements.

Environmental implications of land use change on the fate of Zn in agricultural soils: A case study of Puding karst soils, southwest China

Land use change threatens food security because it may cause the depletion and/or low bioavailability of micronutrients in agricultural soils. Therefore, it is significant to investigate the fate of micronutrients and predict the potential environmental problems. The zinc isotope technique is of particular interest in interpreting soil processes. In this study, Zn isotopic data of soil samples in five profiles based on different land uses were provided, and Zn behavior in different soils was discussed. The isotopic ratios of soil samples in the abandoned orchard, secondary forest, abandoned cropland, and cropland are similar, with the δ66Zn varying from 0.15 to 0.29‰. However, the samples in shrub grassland show a lower δ66Zn of 0–0.20‰, which may be affected by anthropogenic sources. For the vertical patterns, the non-cultivated long-rooted plants (i.e., abandoned orchard and secondary forest) show no significant difference in the distribution of δ66Zn, but the patterns of cropland and abandoned cropland samples are reversed. The cropland samples show positive correlations between δ66Zn and Fe2O3 (R2 = 0.90) and MnO (R2 = 0.75), indicating that Fe and Mn oxides preferentially adsorb heavy Zn isotopes on the mineral surfaces. The high affinity between Zn and oxides indicated that the concentration of bio-available Zn in cropland soils was getting lower. As a result, the supplies of micronutrients may be deficient and urged from fertilizer. This study provides a better understanding of Zn cycling in agricultural systems and gives improvements in soil management.

Magnesium and zinc isotopic evidence for the involvement of recycled carbonates in the petrogenesis of Gaussberg lamproites, Antarctica

Lamproites are rare mantle-derived peralkaline ultrapotassic rocks, and they are commonly geographically associated with the ultramafic lamprophyres and kimberlites. Their unique geochemistry and mineralogy make determining their mantle source and origin important because of the significance for inferring specific geodynamic processes. In this study, we further examine lamproite petrogenesis using new Mg and Zn isotopic data for the typical Gaussberg lamproites, Antarctica, the source of which were thought to be contributed by recycled crustal materials. Results show that these lamproites have lower δ26Mg (−0.44‰ to −0.39‰) and higher δ66Zn (0.36‰ to 0.39‰) values than terrestrial mantle (δ26Mg = −0.25 ± 0.04‰, δ66Zn = 0.18 ± 0.05‰). The post-magmatic alteration and crustal contamination as well as fractional crystallization and partial melting cannot account for these anomalous Mg and Zn isotopic values. By contrast, the involvement of sedimentary carbonates which are characterized by light δ26Mg (average approximately −2.0‰) and heavy δ66Zn (average ~ +0.91‰) values in their mantle source can explain these Mg and Zn isotopic anomalies. Quantitative modelling suggests that addition of 10–15% subducted dolomite into the source of Gaussberg lamproites can well reproduce their Mg and Zn isotopic values. The source component with light Mg and heavy Zn isotopic compositions can either be sub-continental lithospheric mantle metasomatized by carbonate melts or residue of subducted carbonate-bearing sediments after deep melting in the mantle transition zone. A lithospheric mantle contribution is indeed required to explain their strongly enriched radiogenic isotopic compositions. However, in terms of carbonate component, their positive ZrHf anomalies (Hf/Hf* = 1.28–2.19), and extremely high K/U (~40, 000) and Ba/Th (~400) ratios lead us to favor the latter deep recycling model in which the recycled carbonate-bearing sediments subducted as K-hollandite and majorite underwent partial melting within the mantle transition zone.

Zinc, sulfur and cadmium isotopes and Zn/Cd ratios as indicators of the origin of the supergiant Broken Hill Pb–Zn–Ag deposit and other Broken Hill-type deposits, New South Wales, Australia

AbstractVarious genetic models have been proposed for the supergiant Proterozoic Broken Hill Pb–Zn–Ag deposit largely based on geological and geochronological evidence. Here we present Zn, Cd and S isotope compositions as well as Zn/Cd ratios of sphalerite from Broken Hill and minor Broken Hill-type deposits (Australia) to help constrain these models but focus on syngenetic and magmatic–hydrothermal processes, since epigenetic models can be rejected because the orebodies were deformed and metamorphosed by the Olarian Orogeny. Values of δ34SVCDT, δ66ZnAA-ETHand δ114CdNIST SRM 3108for sphalerite from Broken Hill range from +0.27 to +4.73 ‰, −1.15 to +0.46 ‰ and −0.48 to +0.01 ‰, respectively, while those for the smaller Broken Hill-type deposits range from −5.11 to +1.28 ‰, −0.97 to +0.10 ‰ and −1.02 to +2.59 ‰, respectively. By combining published S isotope data of sulfides from the Broken Hill district with those obtained here, the sources of sulfur via thermochemical sulfate reduction, bacterial sulfate reduction and a magmatic origin cannot be distinguished. However, when the S isotope compositions are considered along with the broad range of Cd and Zn isotope data for sphalerite, which are among the lightest and heaviest yet reported for a sulfide deposit, the isotopic datasets are consistent with low-temperature biogenic processes associated with syngenetic deposition of sulfides. Cadmium isotope compositions when coupled with Zn/Cd ratios of sphalerite have previously been used to classify Pb–Zn deposits, including low-temperature, high-temperature and exhalative ores. However, the Zn/Cd ratios of sphalerite from Broken Hill cannot be used for such classification purposes.

The zinc isotope composition of late Holocene open-ocean marine sediments

The controls on Zn burial fluxes into marine sediments are not well constrained by existing datasets. To address this problem, new Zn-isotope data have been generated from a globally distributed array of late-Holocene age sediments that accumulated in open ocean settings underneath a diverse range of depositional conditions (Namibian margin, West African margin, Arabian margin, Californian margin, Peruvian margin, Southern Ocean, Indian Ocean, North and South Atlantic Oceans, South China Sea). The mean non-detrital isotopic composition of Zn in the whole dataset (δ66/64Zn = 0.37 ± 0.25 ‰, 2. S.D., n = 33) is only slightly lower than the modern deep-ocean composition (0.45 ± 0.14 ‰). Locations with total organic carbon >1 wt% have greater non-detrital enrichments of Zn and higher Zn isotope compositions than organic-poor sites, although the uncertainties overlap. Zinc associated with organic matter burial (using Zn/C ratios) and/or oxyhydroxide burial (using Zn/Fe and Zn/Mn ratios) account for a combined total of ~16–73% of the total non-detrital Zn content of the investigated sediments, therefore requiring an additional burial flux of Zn to balance the sedimentary budget. This flux is probably related to ZnS formation although Zn incorporation into authigenic clays is also possible. The new data indicate that open-ocean marine sediments track the deep-ocean Zn isotope composition to within 0.1–0.2 ‰, except in areas where isotopically distinct Zn fractions dominate the non-detrital Zn budget. The fraction of Zn removed into different sedimentary components is used to calculate Zn residence times ranging from ~2.7 kyr to 13.5 kyr that are within the range of previous estimates based on input fluxes to the ocean.

Zinc isotope constraints on carbonated mantle sources for rejuvenated-stage lavas from Kauaʻi, Hawaiʻi

Sedimentary carbonates could be transported into Earth's mantle by plate subduction, but the ultimate fate of these carbonates remains unclear. Zinc isotopes can allow the tracing of recycled isotopically heavy Zn-rich sedimentary carbonates (δ66Zn up to 0.91‰) within the mantle. This study presents new whole-rock major- and trace-element geochemical and Sr–Nd–Pb–Hf–Zn isotopic data for a complete series of rejuvenated-stage alkaline samples from Kauaʻi, Hawaiʻi. These samples have high MgO contents (MgO >8.6 wt%) and show a wide range of whole-rock geochemical compositions, with lower SiO2 contents, higher alkali element contents, higher CaO/Al2O3 values at a given MgO content, more depleted Sr–Nd–Hf isotopic compositions, and more radiogenic Pb isotopic compositions relative to shield tholeiites. The trace-element compositions of these samples have some similarities to carbonatites, including large ion lithophile element enrichments and K, Pb, and ZrHf depletions. These samples also have systematically higher δ66Zn values (0.34–0.43‰) than shield tholeiites from the Kauaʻi (0.27 ± 0.04‰) and Kīlauea Iki lava lake (0.26–0.30‰) and normal mantle (0.18 ± 0.05‰). Modeling the elemental and isotopic behavior of Zn indicates that the heavy Zn isotopic compositions of these samples reflect the nature of their mantle source rather than any processes associated with mantle melting and fractional crystallization. The low 87Sr/86Sr and heavy Zn isotopic compositions of these alkaline samples can be replicated by mixing depleted mantle with minor amounts of sedimentary Mg‑carbonates (<5%). A decrease in whole-rock SiO2 contents from the alkaline basalts to the melilitites in this region correlates with increases in the geochemical signature of sedimentary carbonate-bearing enriched components (e.g., high δ66Zn and low εNd and εHf values). The correlation between the δ66Zn and 206Pb/204Pb values of the samples is in concert with the role of recycled carbonates that could elevate the U/Pb ratio of mantle component caused by the carbonated melt. This implies that the studied samples formed from magmas derived from a mixed mantle source at least containing depleted peridotite and sedimentary carbonate-bearing components. The addition of recycled sedimentary carbonates may be a key factor for the high δ66Zn and 206Pb/204Pb values of the Kauaʻi rejuvenated-stage lavas. These findings suggest that the subducted sedimentary carbonates could accompany the whole circle of recycling of oceanic slab and experience a recycle deep-to-lower mantle in the Hawaiian mantle plume.

Early Cambrian highly metalliferous black shale in South China: Cu and Zn isotopes and a short review of other non-traditional stable isotopes

Early Cambrian black shales on the Yangtze Platform host a regionally distributed highly metalliferous sulfide-rich carbonaceous unit which has been the subject of extensive debate. This marker unit, with a few centimeters or tens of centimeters in thickness, displays extreme enrichment in Mo and Ni (wt% range), and in a broad spectrum of other metals such as As, Au, PGE, Re, Cu, Zn, Cd, Ag, Sb, Se, Tl, and Hg, and occurs discontinuously along the western passive margin of the Yangtze Platform. It grades laterally in stratigraphically equivalent meter-thick vanadium-rich shale and tens-of-meter-thick sapropelite (combustible shale). New Cu and Zn isotope data, combined with existing Cd, Cr, Ni, Mo, Hg, and Se isotope and other chemical data, allow to attempt an integrated view on the formation of this intriguing unit of hyper-enriched metalliferous black shale. The authigenic Cu enrichment in the 1000-ppm range has produced no or little Cu isotope fractionation (0.03 ± 0.26 ‰ δ65Cu) beyond the lithogenic background. Heavy zinc and cadmium isotope enrichment in the sulfidic samples (1.11 ± 0.18 ‰ δ66Zn, 0.31 ± 0.10 ‰ δ114Cd) is controlled by sulfide fractionation and contrasts with V-rich and barren shale (0.60 ± 0.18 ‰ δ66Zn, 0.00 ± 0.14 ‰ δ114Cd). The distinctly negative Ni isotope composition of the metalliferous unit (−0.84 ± 0.05 ‰ δ60Ni) with Ni in the percent range has been interpreted as due to hydrothermal activity related to the leaching of mafic rocks and their sulfides. Sorption processes (Fe-oxyhydroxides) and redox cycling in the water column and the bottom sediment with microbial activity could be an alternative interpretation. The extreme metal enrichment can be understood as due to a process chain, from high biological productivity in the oxic photic zone to sulfate reduction in the deeper sulfidic water column and upper sediment layer. Key to the metal enrichment seems to be extremely low clastic sedimentation and advanced carbon destruction by anaerobic oxidation. Hydrothermal input of basinal brines along the rifted margin of the Yangtze Platform was likely a part of this scenario.

Climate influence on zinc isotope variations in a loess–paleosol sequence of the Chinese Loess Plateau

Zinc (Zn) is an essential micronutrient, and its isotopes are increasingly applied to understand trace metal biogeochemical cycling. Atmospheric deposition from anthropogenic or natural origins can perturbate the nutrient supply globally. However, our understanding on Zn isotope variations in natural mineral dust and during dust–climate interaction is still rare. This study presents Zn isotope data and leaching experiments with ammonium acetate buffering solution (pH = 5) on a loess–paleosol profile (S0–L3) from the Yimaguan section in the central Chinese Loess Plateau. The loess–paleosol sequence records the contributions from Asian mineral dust accumulation and chemical weathering, and the response to glacial–interglacial climate changes. Bulk loess–paleosol samples display limited Zn/Al (3.5 × 10-4 – 4.5 × 10-4) and δ66Zn variations (0.17–0.30‰). The mean δ66Zn of paleosol (0.19 ± 0.01‰, 2SD/√n, n = 11) is slightly lower than that of loess (0.24 ± 0.01‰, 2SD/√n, n = 13). Correlations with magnetic susceptibility and grain size distribution suggest that bulk δ66Zn variations between loess and paleosol are not sensitive to glacial–interglacial source fluctuations or wind sorting, but could result from loess pedogenesis.The leachable Zn fractions have high δ66Zn values (0.80–1.29‰) and display good positive correlations with Ca, Sr, Mg, Fe and Mn (r > 0.7), suggesting that carbonates are enriched in heavy Zn isotopes. Although Zn contents in carbonates are low (<3%) and dissolution of carbonates alone cannot explain the bulk Zn/Al variations (∼7% of Zn loss), significant carbonate weathering and biotic activities during loess pedogenesis could modify soil conditions (pH) and provide dissolved bicarbonate ions and organic ligands, which may facilitate the transport of heavy Zn isotopes by soil liquids. Conversely, the bulk δ66Zn of loess developed during glacial times were not modified by the low degree of chemical weathering, and thus the mean value of 0.24‰ for loess can be regarded as the average composition of the upper continental crust.

Zinc Isotopes of the Mariana and Ryukyu Arc‐Related Lavas Reveal Recycling of Forearc Serpentinites Into the Subarc Mantle

AbstractMantle source heterogeneity of arc‐related magmas was traditionally thought to be predominantly affected by slab‐derived components. However, the role of forearc serpentinites in causing subarc mantle heterogeneity remains poorly constrained. Here, we present the first Zn isotope data for lavas from the Mariana and Ryukyu subduction zones. Notably, the δ66Zn values of basaltic lavas from the Mariana arc (0.16–0.18‰) and southern Okinawa Trough (0.15–0.17‰) are generally lower (∼0.10‰) than those of the mid‐ocean ridge basalts (MORB) (0.27 ± 0.05‰). Since mantle melting and magmatic differentiation respectively induce heavy Zn isotope enrichment in primary and evolved magmas, while melt extraction yields the limited Zn isotope fractionation in the mantle, lavas with low δ66Zn values thus potentially indicate the addition of subducted components. The negative correlation between the δ66Zn values and the Ba/La ratios of the basaltic lavas suggests the involvement of isotopically light fluids in their mantle sources. Forearc serpentinites are typically characterized by extremely light Zn isotope compositions. Such forearc materials were likely dragged downward to subarc depths and released isotopically light Zn in fluids to modify the overlying mantle wedge, thereby producing low δ66Zn values in arc‐related magmas. Beyond subarc depths, forearc serpentinites are broken down completely, so light Zn isotope fluids are absent. Accordingly, the basalts from the middle Mariana and Okinawa Trough display MORB‐like δ66Zn values. Collectively, Zn isotope provides new insights into the role of the recycling of forearc serpentinites in generating chemical heterogeneity in the mantle source of subduction‐related magmas.

Multi-isotope signatures (Cu, Zn, Pb) of different particle sizes in road-deposited sediments: a case study from industrial area

Road-deposited sediments (RDS) are major sources of heavy metal contamination in urban areas and adversely affect surrounding environments and human health. Multi-isotope combinations (Cu, Zn, and Pb), which serve as environmental tracers, enable the identification and management of metal contaminants in RDS. Here, we present Cu, Zn, and Pb isotopic data for the first time in size-fractionated RDS samples collected from industrial areas to describe the relationship between the RDS and total suspended solids (TSS) in runoff, and to explore the feasibility of using multi-isotopes to identify sources of metal contamination. RDS in the industrial study areas had high concentrations of Cu, Zn, and Pb, and their δ65CuAE647, δ66ZnIRMM3702, and 206Pb/207Pb values ranged from − 0.33 to + 0.73‰, − 0.36 to + 0.01‰, and 1.1418 to 1.1616, respectively. The variation in δ65CuAE647 (δ65Cumax-min) was larger than that of δ66ZnIRMM3702 (i.e., δ66Znmax-min), and the isotope values of Zn and Pb (206Pb/207Pb) tended to increase with the concentrations of these elements. Meanwhile, the fine RDS particles (< 63 µm) had similar Cu, Zn, and Pb isotopic compositions to those of TSS. Hierarchical cluster analyses revealed that the < 63 µm RDS fractions were associated with the TSS. Our results also showed that a combination of Pb and either Cu or Zn could be used to distinguish between RDS and non-exhaust emissions (e.g., brake pads, tires, etc.). Multi-isotope approaches utilizing Cu, Zn, and Pb and more robust isotopic data on individual sources of metal contamination could be useful for identifying pollution sources and understanding their environmental impacts.