Pb Isotope Ratios Research Articles

Spatial and temporal trends in δ66Zn and 206Pb/207Pb isotope ratios along a rural transect downwind from the Upper Silesian industrial area: Role of legacy vs. present-day pollution

Transect sampling is an under-exploited tool in isotope studies of atmospheric pollution. Few studies have combined Zn and Pb isotope ratios to investigate whether atmospheric pollution at a receptor site is dominated by a different anthropogenic source of each of these toxic elements. It has been also unclear whether pollution abatement strategies in Central Europe have already resulted in regionally well-mixed background isotope signature of atmospheric Zn and Pb. Zinc and lead isotope ratios were determined in snow collected along a rural transect downwind from the Upper Silesian industrial area (southern Poland). Spatial and temporal gradients in δ66Zn and 206Pb/207Pb ratios at four sites were compared with those of ore and coal collected in eight Czech and Polish mining districts situated at distances of up to 500 km. Snow pollution was extremely high 8 km from Olkusz in 2011 (1670 μg Zn L−1; 240 μg Pb L−1), sharply decreased between 2011 and 2018, and remained low in 2019–2021. Snow pollution was lower at sites situated 28–68 km from Olkusz. Across study sites, mean δ66Zn and 206Pb/207Pb ratios of snow were −0.13‰ and 1.155, respectively. With an increasing distance from Olkusz, the δ66Zn values first increased and then decreased, while the 206Pb/207Pb ratios first decreased and then increased. The δ66Zn values in snow plotted closer to those of Upper Silesian ores (−0.20‰) than to the δ66Zn values of Upper Silesian stone coal (0.52‰), showing predominance of smelter-derived over power-plant derived Zn pollution. The 206Pb/207Pb ratios of Upper Silesian coal (1.171) and Upper Silesian ores (1.180) were higher compared to those of snow. A206Pb/207Pb vs.208Pb/207Pb plot identified legacy pollution from leaded gasoline as the low-radiogenic mixing end-member. Across the transect sites, only the last sampling campaign exhibited a high degree of isotope homogenization for both Zn and Pb.

Pb isotopes reveal intracrustal exhalative hydrothermalism during deposition of the ∼3.43 Ga Strelley Pool Formation

Hydrothermal systems are widely considered to have supported development of Earth's early microbial ecosystems by providing energy and nutrients to surface and subsurface environments. We studied a remarkably extensive and well-preserved hydrothermal dike complex active during deposition of the ∼3.43 Ga Strelley Pool Formation (Warrawoona Group, Pilbara Region, Western Australia). We report field observations, mineralogy, Pb isotope ratios, and selected trace metal concentrations for black, silica-rich dikes at the study site. The majority of the samples fall into two distinct arrays in the common Pb isotope diagram. One group of samples, with many very unradiogenic isotope ratios, defines a slope whose apparent age is roughly coeval with deposition of the Strelley Pool Formation. The other group, containing samples with elevated 206Pb/204Pb ratios and generally low 208Pb/204Pb ratios, has a moderately well-defined slope of apparent Neoarchean age. The original Pb isotope ratios of this latter group were likely disturbed by a combination of Pb isotope memory resetting, Pb-loss, and U-addition. Using the trace metal concentrations of samples associated with Paleoarchean Pb isotope memory, we identify a crustal rather than a mantle source for metals carried in the hydrothermal system. An intracrustal (as opposed to an oceanic ridge) setting is also consistent with local and regional geology. Combined 208/207/206/204Pb systematics of the dike complex reveal a striking similarity to unconformable Pb found in older Pilbara Craton sediment-hosted metal deposits of the Doolena Gap Formation, Apex Basalt, Coppin Gap, and the Dresser Formation. The unusual Pb isotope systematics, plotting far above conformable Pb isotope evolution curves, is currently poorly understood. We discuss the use of Pb isotopes to constrain the timing of geological events including the age of initial deposition, and the loss and resetting of original geochemical signatures. We propose that improving our understanding of early Earth environments influenced by hydrothermalism requires combining geochemical fingerprints with proxies, such as Pb isotopes, which are very sensitive to potential contribution from crustal sources.

A high-resolution Os-Nd-Pb isotopic record of a hydrogenous Fe[sbnd]Mn crust from the Northwestern Pacific and its response to plate motion

Ferromanganese crusts are ideal archives of the isotopic composition of ambient deep waters. The cause of the long-term variations of Nd and Pb in the North Pacific deep water has not been well constrained because of a lack of reliable dating method. In this study, we documented the long-term Sr-Os-Nd-Pb isotopic evolution and major elements chemistry of a ferromanganese crust that grew in Northwestern Pacific deep water. The crust was dated using Os isotopic stratigraphy and has a maximum age of 86 Ma. In the early Cenozoic, εNd values increased from −5.3 to −4.0, and the Pb isotope ratios decreased, which can be explained by an input from the margin of South America that contributed both Nd and Pb to the Pacific deep water. The synchronous variations of Nd and Pb isotopic compositions were relate to the reduction of the source. Since Miocene, εNd value trended to more radiogenic values of −4.8 to −3.3 with oscillation owe to the decreased and pulsed input of the southern component water into the Pacific caused by the closure of the Indonesian seaway. The Pb isotope ratios increased after 35 Ma but remained lower than those of central North Pacific crusts. The Pb isotopic compositions did not respond to the one order of magnitude increase in dust flux and increase of Al content along with Pb isotope ratios since 10 Ma, which support that the arc-derived Pb dominated the Pb isotopic signature as the crust moved from the southern to northern Pacific, although Asian dust may have contributed to the Pb budget.

A study to characterize the lead isotopic fingerprint in PM2.5 emitted from incense stick and cigarette burning.

The incense sticks and cigarettes burning are key sources of particulate matter with a diameter of ≤ 2.5μm (PM2.5) in indoor and outdoor air. While lead (Pb) isotope ratios provide valuable insights into the origin of particle pollution, their applicability for investigating these source remains unclear. The Pb isotope ratios in the PM2.5 emitted from these two sources were analyzed, and effects of brands or nicotine contents on the ratios were assessed. In addition, As, Cr, and Pb were analyzed to investigate whether Pb isotope ratios can serve as an indicator for the source investigation of these metals. We found that average ratios of 206Pb/204Pb, 206Pb/207Pb, and 208Pb/207Pb in cigarettes were heavier than those in incense sticks. Scatter plots of Pb isotope ratios indicated an overlap of values for incense sticks or cigarettes linked to different brands, in that ratios for cigarettes with high nicotine content were heavier than for those with low nicotine content. Scatter plots of As, Cr, or Pb concentration against Pb isotope ratios clearly distinguished the effects of cigarette burning versus incense sticks with respect to PM2.5 of these metals. Results indicate that brand differences did not affect the determination of PM2.5 in these two sources. We suggest that Pb isotope ratios can be a useful tool in investigating the influenceof incense sticks and of cigarettes (with high or low nicotine content) burning to PM2.5 and associated metals.

Trace element composition and genesis mechanism of the Fuli Pb-Zn deposit in Yunnan: LA-ICP-MS and in situ S-Pb isotopic constraints

The Fuli Pb-Zn deposit in Yunnan is located in the southeast of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn metallogenic province in South China. Lead and zinc reserves total approximately 0.3 million tons with an average grade of 18.68% Pb+Zn. The stratiform ore occurs in the interlayer fracture zone of the middle Permian Yangxin formation dolomite. The main sulfides of the Fuli Pb-Zn deposit consist of sphalerite, galena, and pyrite, while dolomite and calcite are the main gangue minerals. Mineralization exhibits massive, disseminated, vein and breccia textures. Sphalerites of two colors (black and red) have been identified in the Fuli deposit. LA-ICP-MS analysis revealed that the black and red sphalerites were enriched in Cd, Cu, Ga, and Ge and depleted in Fe, Mn, and In to varying degrees. The aforementioned elements exhibit homogeneous patterns in the LA-ICPMS time resolution profiles, which is consistent with variations in the concentrations of major elements like Zn and S. This indicates that these elements may occur in sphalerite as a result of isomorphous substitution. However, elements such as As, Sb, Pb, and Ag fluctuate greatly in the LA-ICPMS time resolution profiles, suggesting that these elements may exist as fine inclusions. Thus, the different colors of the Fuli sphalerite may be attributed to various elements such as Ni, Cu, and Ga; Ni and Cu result in purple Sp, Cu renders sphalerite red, and Ga imparts a yellow color. The sulfur isotope compositions of the two sphalerites exhibit little variation, with δ34S values ranging from 15.57‰ to 16.91‰, indicating the enrichment of 34S. These results are consistent with the sulfur isotopic compositions of Permian marine sulfates, indicating that thermochemical sulfate reduction was the main source of the reduced sulfur in the hydrothermal fluids. In situ Pb isotopic composition analysis revealed 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb values for galena in the range of 38.5–38.651, 15.666–15.733, and 18.539–19.124, respectively. The in situ Pb isotopic ratios of most galenas plot on the field of the basement metamorphic rocks of the Kunyang Group. These in situ Pb isotopic signatures reveal that the metallogenic metals are mainly derived from crustal basement. The findings of this study suggest that the Fuli Pb-Zn deposit is a MVT Pb-Zn deposit controlled by the interlayer compressional structure with characteristics of carbonate-hosted, epigenetic, simple mineral symbiosis, high Pb-Zn grade, and abundant Cd, Ga, and Ge along with other dispersed elements.

Geochemical and radiogenic isotope records of the Weissert Event in south Tethyan sediments

The Cretaceous marine sedimentary record is characterized by time intervals rich in organic matter correlating with positive carbon isotope excursions, often called oceanic anoxic events. The Weissert Event corresponds to the first such event in the Cretaceous during the Valanginian stage. The associated palaeoenvironmental perturbations, which include increasing marine surface water primary productivity, are hypothesized to have been triggered by volcanic activity from large igneous provinces, and the source of nutrients is not well constrained (continental runoff v. oceanic upwelling). We present isotope ratios of Pb, Sr and Nd, together with concentrations of major and trace elements, for sediments from the central Moroccan margin to test these hypotheses. We demonstrate that the nutrient input was dominated by continental weathering. The source of sedimentary material remained stable during the Valanginian interval and originated from an old source, probably the African Sahara region. The radiogenic isotope signatures do not show a significant contribution of volcanic products from any known Valanginian large igneous province to the geochemical budget of sediments deposited on the central Moroccan margin. Although this does not preclude an impact of volcanic activity on the composition of seawater, it demonstrates that the erupted volumes were not sufficient to affect the deposited sediments. Supplementary material: The Supplementary Table contains three sheets: (1) Central Moroccan Margin, the analytical data generated and analysed during this study; (2) Fig. 8 data, large igneous provinces, the data of known Valanginian large igneous provinces used for comparison; and (3) Fig. 9 and S5 data, source areas, the data of potential surrounding source areas used for comparison, available at https://doi.org/10.6084/m9.figshare.c.6333040 .

Low-cost and sensitive method for Pb isotope determination using a novel β-Si3N4 emitter by thermal ionization mass spectrometry

Thermal ionization mass spectrometry (TIMS) is the workhorse for lead isotopic ratio analysis due to its excellent precision. Silica gel as ionization activator on Re filament is proved to the best emitter that can provide excellent sensitivity even small Pb sample size. However, the price of Re filament is three times that of Ta filament that leads to high experimental cost for TIMS laboratory. Here, we first present a novel silicon nitride (β-Si3N4) emitter on the Ta filament with good sensitivity for Pb isotopic ratio measurements. Hence, the cost of filament material is cut down ∼70%. The β-Si3N4 emitter can yield stable and long-life Pb+ signal, about 2–3 V 208Pb and 0.65–0.90 V 208Pb for 20 ng and 5 ng NIST SRM981 sample size that is applicable to the most geological materials for bulk analysis. A suite of silicate reference materials were analyzed to verify the reliability and accuracy of our method. For 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotope ratios of geological samples, excellent internal precisions (2 SE) of ±0.005%–0.013% are achieved. Replicate digestions and analyses of the basalt standard BCR-2 and coal fly ash standard GBW08401 demonstrate that good external precision is obtainable that is 0.10–0.18% (n = 6, 2 SD) for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios.

Lead isotope measurement of primer gunshot residues and likelihood ratio predictions for forensic cartridge discrimination and individualization in China

Gunshot residues (GSR), cartridge projectiles, and casings are frequently encountered evidence in gun-related forensic investigations. However, in circumstances where the investigation of striation marks is impossible, such as unrecovered or deformed projectiles and cartridge casings, GSR deposited on the hands or clothes of the shooter and victim-related items can provide information to establish a link between the suspect, the firearms used, and the victim. Since the formula of primers used by all cartridge manufacturers in China is identical, links based on the conventional morphological and compositional analysis of GSR are difficult to establish. However, the abundance of lead isotopes in primer components of lead styphnate varies significantly, and a fundamental understanding of these differences may facilitate the validation of primer (p)GSR evidence in forensic investigations. Here, 44 pGSR samples were characterized by Pb isotope ratios of 206 Pb/204 Pb, 207 Pb/204 Pb, and 208 Pb/204 Pb using laser ablation multicollector inductively coupled plasma mass spectrometry. There was no obvious mass fractionation of the lead isotope ratios of the primers from individual cartridges analyzed before and after the shooting process, thereby establishing a basis for the comparison of pGSR and unfired cartridges. Evaluation of the results using univariate likelihood ratio (LR) computations revealed low rates of misleading evidence (<0.53%) The results demonstrated that lead isotope ratio analysis of pGSR and LR predictions can provide a practicable method for forensic cartridge discrimination and individualization.

Extreme isotopic heterogeneity in impact melt rocks: Implications for Martian meteorites

AbstractLead isotope ratios have been determined in multiple feldspar grains from hand samples of impact melt rock at the Manicouagan and Sudbury impact structures in Canada. The results reveal an extreme range of isotope values. This indicates that melt sheets are not homogeneous with respect to Pb at the millimeter scale. Such heterogeneity is significantly larger than that seen in non-impact-generated igneous rocks. Individual Pb isotope ratios of feldspars from Martian shergottites show a large range in 206Pb/204Pb values within one sample, more similar to the terrestrial impact melt sheets than to nonimpact igneous rocks. We suggest crystallization from impact melt sheets rather than volcanic sources as a petrogenetic model for some of the Martian shergottites.

Dissolved Lead (Pb) Concentrations and Pb Isotope Ratios Along the East China Sea and Kuroshio Transect—Evidence for Isopycnal Transport and Particle Exchange

AbstractLead (Pb) isotopes are widely used in tracing processes that transport Pb within the environment due to the globally spread Pb pollution. In today’s ocean, Pb is mainly sourced from anthropogenic emissions and is removed by particle scavenging. However, recent efforts involving Pb isotopes have started to indicate that sediments at ocean boundary, either suspended or benthic, are a previously underestimated source and sink of Pb to the seawater dissolved pool. To assess the contributions of Pb from seawater‐sediment boundary, we measured the dissolved Pb concentrations and isotopic compositions in seawater from the outer East China Sea (ECS) and along the Kuroshio. Along the Kuroshio, depth profiles exhibit highly similar Pb concentrations across constant density planes, suggesting isopycnal transport. Pb isotope ratios in most of the samples show strong contributions of aerosol Pb, except for seawaters from the ECS and deep Okinawa Trough (&gt;800 m), which show evidences of crustal Pb contribution. The Okinawa Trough deep water has overlapping Pb isotope ratios with ECS water, where the suspended particulate matter is abundant. Our data on Pb isotopes in the ECS and the Okinawa Trough deep water, together with data from previous studies at other continental margins suggest that the seawater‐sediment boundary along the continental shelves may be an important source and sink in marine Pb cycling.

Evolution and origin of the Bairendaba Ag–Pb–Zn deposit in Inner Mongolia, China: Constraints from infrared micro-thermometry, mineral composition, thermodynamic calculations, and in situ Pb isotope

The Bairendaba deposit is a typical large-scale Ag–Pb–Zn vein-type deposit in the Southern Great Hinggan Range, Inner Mongolia, China. Vein-type orebodies are hosted within biotite–plagioclase gneiss and quartz diorite and controlled by EW- and NE-trending faults with extensive hydrothermal alteration. Three primary mineralization/alteration stages have been recognised as the early ore stage, forming ore-barren quartz veins with arsenopyrite and pyrite, the primary ore stage, forming Zn-rich sulphide veins and Pb–Ag-rich sulphide–sulfosalt veins and the late barren stage, characterised by plenty of calcite, muscovite and fluorite veins. Infrared micro-thermometric data and mineral geothermometer show temperatures of ∼300 °C and ∼180 °C for Zn mineralization and Pb–Ag mineralization, respectively. A combination of mineralogical observations and thermodynamic calculations show that Zn mineralization is at pH 5.1 to 7.2 and logfO2 of −39.7 to −35.3, whereas Pb–Ag mineralization is at pH 5.6 to 7.4 and logfO2 of −48.2 to −40.3. The sulfidation state is estimated to be intermediate-low sulfidation. Conductive heat loss and extensive wall rock alteration are inferred to cause the Zn deposition, whereas an influx of meteoric water and wall rock alteration primarily trigger the large-scale Ag deposition. Laser ablation–inductively coupled plasma–mass spectrometry analysis shows that chalcopyrite is anomalously enriched in Sn (>1000 ppm). Sn is hosted in chalcopyrite of Zn mineralization in solid solution, whereas it exists as a stannite group phase in chalcopyrite of Pb–Ag mineralization. The occurrence of stannite group minerals in chalcopyrite of Pb–Ag mineralization might imply the decomposition of the Sn-bearing chalcopyrite at low temperature. In situ Pb isotope ratios of galena (206Pb/204Pb = 18.374–18.399, 207Pb/204Pb = 15.581–15.601 and 208Pb/204Pb = 38.332–38.416) indicate that the ore metals could be derived from the Mesozoic magma. Trace element compositions of sulphides in the Bairendaba deposit share the same characteristics with magma-related systems but differ considerably from non-magmatic and epithermal deposits. These results, combined with geological and isotopic evidence, suggest that the Bairendaba deposit is a magma-related hydrothermal vein-type deposit, indicating further exploration prospects for Sn mineralization near and/or under the Bairendaba mining area.

The effects of the source composition on the origin of orthopyroxene-bearing adakitic granitoid in West Qinling, Central China

Orthopyroxene-bearing granodiorite (sometimes referred to as ‘charnockite’) with an adakitic affinity is a rare type of granitoid. It is generally accepted that the stabilization of orthopyroxene in igneous charnockites essentially requires low aH2O and/or high temperatures in a closed system. However, orthopyroxene can be an antecryst in a trans-crustal magmatic system. In this regard, orthopyroxene-bearing granitoids are somewhat analogous to pseudo-charnockites, where the orthopyroxene stems from a mafic reservoir. On the other hand, the source compositions of continental adakites can vary, which is often ignored in the interpretation of their contribution to the adakitic geochemical signature. In this study, we have investigated a rare orthopyroxene-bearing felsic pluton from the Zhuyuan area of West Qinling, Central China. The Zhuyuan pluton was emplaced in the Middle–Late Triassic (222 Ma–217 Ma) and is mainly composed of metaluminous to weakly peraluminous granodiorites belonging to the high-K calc-alkaline series. Moreover, they are characterized by high Mg# values (49.7–60.9) and Sr contents (471–697 ppm), low Y (12.2–15.4 ppm) and Yb (1.03–1.24 ppm) contents, high Sr/Y (33.2–46.2) and (La/Yb)N (15.3–21.4) ratios, and weakly negative Eu anomalies (Eu/Eu* = 0.78–0.89). The Zhuyuan adakitic granodiorites exhibit fairly limited Sr–Nd–Pb isotopic ratios and variable zircon initial Hf isotopes, indicating a major contribution from the Neoproterozoic basement of the Qinling Orogenic Belt. There is no evidence of any formation through high-pressure magmatic processes, and we propose that the adakitic signature of the Zhuyuan pluton could have been inherited from its source rocks (i.e., from the Neoproterozoic basement). The orthopyroxenes in the Zhuyuan granodiorites display poikilitic textures with high MgO, NiO and Cr2O3 contents, indicating that they have an antecrystic origin. Studies of regional tectonic evolution have shown that the Zhuyuan granodiorites formed during the tearing stage of the A'nimaque–Mianlue oceanic subduction slab. Therefore, this study emphasizes the effect of source inheritance on the formation of pseudo-charnockite with an adakitic signature.

Archean Pb isotope variability tracks crust-mantle fractionation, granite production, and ore deposit formation

Various geological processes that affect Earth's crust may be encoded into isotopic tracers preserved in rocks and minerals. The enhanced sensitivity of U, Th, and Pb to crustal fractionation processes allows Pb isotopes to complement information from the Nd and Hf isotope systems. However, melt fractionation, crustal contamination and recycling, hydrothermal fluid flow and fluid-rock interaction, and other processes in the continental crust can lead to mixing of Pb isotopic signatures. Here, we report new Pb isotopic data from granite-K-feldspar and integrate these data with published Pb isotope ratios from granite K-feldspar and Pb-rich ores across the Yilgarn Craton in Western Australia. The aim of this study is to explore how the variability of Pb isotope ratios and derivative parameters can be used to gain information on specific geological processes occurring throughout the crustal column. We develop a model that subdivides different sampling media into chemical process groups and links their initial Pb signatures to Pb source regions and fractionation processes at various locations within the crust and upper mantle. Equilibration of Pb signatures with a primary mantle source reservoir (in part represented by volcanic-hosted massive sulfides) is contrasted with granite formation in the mid to lower crust (granite K-feldspar), and mineralization of ore deposits in the mid to upper crust (Pb-rich ores). Spatial trends similar to those in Nd and Hf isotopic data are recorded by Pb isotopic derivative parameters (μ = source 238U/204Pb, ω = 232Th/204Pb, and Δt - the difference between true sample age and Pb model age) calculated for komatiite-hosted Ni sulfide ores, granite K-feldspar, and volcanic-hosted massive sulfide (VHMS) ores. The significance of subtle differences in absolute values of derivative parameters is supported by the diversity of Pb isotope ratios, Pb model ages, and ∆t as tracked by a statistical metric, quantifying the variability of Pb sources involved in the formation of different chemical process groups. Generally greater variety in an older terrane (Youanmi) documents more ancient and recycled continental crust as compared with more homogeneous Pb isotopic signatures in a younger terrane (Eastern Goldfields Superterrane). The Pb signatures are interpreted, in part, to relate to the timing of source fractionation in the upper mantle with a legacy of this source signal preserved through various depths in the lithospheric section. The least radiogenic VHMS ore samples appear to provide a good approximation of mantle Pb signatures, indicated for example by a deficit in 206Pb and 208Pb relative to the other process groups. A significant heterogeneity recorded in Pb isotopic data from Pb-rich gold ores is explained by the interplay of hydrothermal fluids with diverse sources leading to the mineralization of gold deposits (e.g., leaching of Pb from surrounding rocks or fluid mixing). Such gold ore Pb signatures are distinct from other process groups, which together track sources less heterogeneous in age and/or U and Th.

Metallogeny and exploration strategy for volcanic rocks hosting world class Be-U-F mineralization at Spor Mountain, Utah, U.S.A.

We report new geochemical data (major-elements, trace-elements, and Nd-Pb isotopes) for the Spor Mountain Formation (SMF), a volcanic sequence that hosts the largest deposit of beryllium in the world. Understanding the genesis of the deposit is critical for improved recognition of regional exploration targets containing additional volcanic-hosted beryllium resources. The deposit occurs in an area of extensive alkalic rhyolitic ash flow tuffs and calderas underlain by Paleozoic and older limestone, dolomite, shale, and quartzite. The lower fluorite and bertrandite-rich tuff and upper topaz-rich rhyolite of the SMF have overlapping zircon crystallization ages (25.59 + 0.29/−0.45 Ma). Enrichment of Be, U, and F is a key attribute of the SMF inherited from melting heterogeneous source materials and magma hybridization in the continental lithosphere. Two mineralization stages are implicated: magmatic, and hydrothermal/metasomatic. The magmatic stage occurred early, as indicated by the high beryllium content in early-crystallizing zircon. The post-magmatic/hydrothermal stage involved F-rich fluids that reacted with glass and carbonate nodules in the tuff to form bertrandite (and U-rich fluorite and opal) and high-grade mineralization. The rhyolite best displays the magmatic stage of enrichment. The SMF is alkaline. Chondrite-normalized REE patterns for tuff and rhyolite are regular, stacked subparallel, and imply a shared source derivation and evolution. The tuff and rhyolite plot along a sub-vertical array for Pb isotopes and suggest they are cogenetic; both have negative values of εNd. Pb isotopic ratios for SMF do not match the slopes, initial isotopic values, or estimated basement ages of precious and base metal mining districts in Utah; thus, they do not share a source region or evolution. Crustal ages from Nd isotopes (average TDM ~ 2.29 Ga) are older than basement ages obtained by Pb isotopes. The deposit occurs in a transitional area of thinned crust near the boundary between two basement domains, the eastern Great Basin and Colorado Plateau, which have contrasting ages. Many geochemical attributes are shared between SMF and the Ermakovka deposit in Russia: they represent the world's major commercial Be deposits. Rare-metal indices of granite-related mineralization show that SMF resembles other global beryllium-bearing granitic deposits. Despite this coincidence, none of these examples matches the mineralogy, geologic setting, or type of rare metal mineralization at Spor Mountain.

Pre-eruption magmatic processes and magma plumbing system at Hachijo-Nishiyama volcano, Izu–Bonin arc, Japan

Nishiyama volcano on Hachijojima Island is an active basaltic volcano located in the Izu–Bonin arc. In this study, petrological and geochemical analyses were conducted on mafic lavas and pyroclastics to understand the magma plumbing system and pre-eruption magmatic processes. Whole-rock major element compositions show significant variations (49.4–54.9 wt.% SiO2), and the samples contain variable amounts of plagioclase phenocrysts (1–40 vol.%). The whole-rock Sr, Nd, and Pb isotopic compositions of samples from the youngest volcanic stage (< 0.7 ka) are homogeneous, whereas some samples from the older stage (3–1 ka) have relatively low Pb isotopic ratios. This observation suggests that the younger magmas were derived from a single parental magma, but another parental magma with distinct geochemical features was involved in the magmatic system before 1 ka. The temporal variation in the FeO*/MgO ratios of the volcanic products is complex and is considered to reflect the intermittent injection of primitive magmas into the main magma chamber in which fractional crystallization occurred. Two-pyroxene geobarometry suggests that the main magma chamber was located at a depth of 9–12 km. The core region of some plagioclase phenocrysts consists of a glass inclusion-free inner core and an inclusion-rich outer mantle, suggesting that some plagioclase crystallized in the main magma chamber, which was followed by overgrowth during magma ascent because of increasing liquidus temperatures due to decompression-induced water exsolution from the melt. The whole-rock compositions of some eruption units with different Al2O3/MgO ratios exhibit distinct plagioclase-controlled trends, which negates the possibility that plagioclase accumulation occurred in a stable magma chamber. In addition, the density of plagioclase was higher than that of the melt during the magma ascent to the surface. From these observations, it is suggested that the accumulation of plagioclase phenocrysts occurred in ascending magmas as the plagioclase settled relative to the surrounding melt. The estimated depth of 9–12 km for the main magma chamber coincides with the depth range over which earthquake swarms occurred in 2002, suggesting that the magma chamber is still active, and that the earthquake swarms may reflect the injection of primitive magma into the magma chamber.Graphical

A PCA-AHC Approach to Provenance Studies of Non-Ferrous Metals with Combined Pb Isotope and Chemistry Data

This paper discusses the applicability of the Principal Component Analysis-Agglomerative Hierarchical Clustering (PCA-AHC) approach to provenance studies of non-ferrous metals using combined Pb isotope and chemistry data. Pb isotopic ratios were converted to the natural abundance of individual isotopes and then to weight units. Next, all relevant variables (Pb isotopes and trace elements) were processed with PCA and AHC to examine the relationships between observations. The method is first verified on three literature-based case studies (1, 2, and 3). It is argued that, as is the case in archaeological iron provenance studies, the PCA-AHC method is also viable for non-ferrous metals. This method can greatly facilitate research, compared to conventional biplots with ratios of Pb isotopes and trace elements. Additionally, PCA-AHC can become part of the initial deposit selection process, and it can help clarify less obvious classification cases. The main problem with a practical application of this approach is insufficient deposit datasets with complete Pb isotopic and chemistry data. In such cases, it is possible to use the PCA-AHC method separately on Pb isotopic and chemistry data and then to compare and contrast results. Alternatively, the proposed approach can be used solely with Pb isotopic data. This application is shown in two additional case studies (4 and 5), which demonstrate the method’s application for tracing artefacts to their parent ores using datasets with a few thousand observations.

Elemental abundances and isotopic composition of Italian limestones: Glimpses into the evolution of the Tethys

Biogenic limestones from three sections (north, central, and south) across peninsular Italy have been analysed for major and trace elements and Nd, Pb, and Sr isotopic ratios. These data are used to monitor the evolution of the Tethys Ocean from the Triassic through to the Miocene. Limestones’ major, trace, and REE elements contents are consistent with their formation in seawater with little sign of crustal, volcanic, or hydrothermal input. V/Cr and Ce/Ce* ratios indicate their deposition in oxygenated waters. Rb-Sr-Ba discrimination diagram, consistent with the immobile trace element distribution, indicates that limestone deposition took place in either marginal or open ocean environments. Ages based on stratigraphy are in good agreement with the chronostratigraphic Sr curves implying that the Tethys ocean, throughout its history, was in contact with the open, global, ocean system. Although the isotopic values of Sr and Nd are relatively restricted, Pb is extremely variable and highly radiogenic. High Pb isotope ratios characterise limestones deposited during the rifting of the southern Tethyan ocean in the Lower Jurassic and in the Lower Cretaceous, suggesting stronger crustal inputs in small basins. The weighted average, present-day, isotope values (AIL = average Italian limestone) for the Italian limestones, excluding anomalous samples, are 87Sr/86Sr = 0.70785, 143Nd/144Nd = 0.51227, and 206Pb/204Pb = 18.94, 207Pb/204Pb = 15.69, 208Pb/204Pb = 38.66. These values are useful in monitoring the fate of limestones during orogenesis and the role that they may have played in magma genesis.

Геохимическая характеристика источника пород вулкана Дзотол на Юго-Востоке Монголии: финальная генерация расплавов позднего кайнозоя в зоне транстенсии на границе литосферы–астеносферы

The purpose of this study is to establish relationship between a source for final eruptions on the Dzotol volcano and those for the whole preceded Late Cenozoic volcanism in the Dariganga field. Major oxides, trace elements, and Pb isotopic ratios in rocks of the volcanic field are indicative for generation of magmatic melts in a homogeneous mantle region. In final eruptions of the Dzotol volcano, rocks show, on the one hand, intermediate geochemical signatures relative to those of other Dariganga volcanic rocks, and, on the other hand, lower Pb isotope ratios. We infer that Dariganga volcanic rocks were derived due to deep degassing of the about 4.47 Ga protomantle and were dispersed at the asthenospheric–lithospheric boundary affected by transtension. The source for the final Dzotol rocks corresponded in depth to the central part of the magma-generating region and displayed the Pb-isotopic protomantle component, previously designated in rare Quaternary Dariganga rocks.

Contribution to the Serbian coal ranking and fly ash characterization using Pb isotopic ratio

The Republic of Serbia generates the majority of its electricity at the thermal power plants (TE) Nikola Tesla, Kolubara, and Kostolac. Coal is extracted from the Kolubara basin, which produces approximately 70% of lignite (an average of 30 million tons per year), and the Kostolac basin, which produces 30% of lignite. Ash, fly ash, and slag are examples of coal combustion residues. Because of the high content of potentially hazardous elements such as As, Pb, Cd, and Cr, environmental pollution with ash and fly ash has been extensively researched. Stable isotopes of lead can be used to trace lead sources. It is possible to monitor the presence, transformation pathways, and environmental impact of Pb by determining its isotopic composition in coal and fly ash. For the first time, the isotopic composition of selected coal samples from the Kolubara and Kostolac mines, as well as fly ash from the Kolubara (A and B), Kostolac (A and B), and Nikola Tesla (TENT A3, A2, B2) thermal power plants, was investigated in this study. The obtained data for 206Pb/207Pb in coal serve as the foundation for ranking domestic coals, whereas the isotopic ratios 206Pb/207Pb and 208Pb/207Pb in fly ash can be used to monitor and control lead pollution from investigated sources.

Source-oriented ecological risk assessment of heavy metals in sediments of West Taihu Lake, China

The geographical location of West Taihu Lake determines that it is the entrance of the whole Taihu Lake, and the intensive industries around it pose a great threat to the ecology of Taihu Lake. We innovatively combined Pb isotope ratio analysis with ecological risk assessment index to quantify the source-oriented ecological risk of heavy metals (HMs) in the sediments of West Taihu Lake. In this study, the representative HMs Zn, Pb, Cr, and Cd in the surface (0-2cm) sediments of West Tai Lake were determined, and the ecological risk assessment of HM sources was carried out based on the Pb isotope ratio and ecological risk index. The results showed that HMs were significantly enriched in the south and thewest of the study area. The average geo-accumulation index (Igeo) of Pb was unpolluted, Cr and Zn were between unpolluted and moderately polluted, and Cd was moderately polluted. The average ecological risk index (Ei) of Pb, Cr, and Zn was low, and only Cd reached a considerable risk (ECd = 120.7), which accounted for 89.8% of the comprehensive ecological risk index (RI). However, the RI in the whole study area (RI = 134.4) still indicated low risk. There was a significant correlation between Pb and other HMs (P < 0.05). The IsoSource analysis showed that the order of contribution rate was fossil fuels (48.0%) > industrial sources (35.8%) > natural sources (14.9%) > agricultural sources (1.3%). The HM pollution caused by fossil fuel combustion and industrial activities reaches a moderate ecological risk, whereas natural sources and agricultural sources pose a low risk. Overall, the main sources of HM pollution are anthropogenic, which pose moderate ecological risk to the study area and should be paid more attention to.