Lead Isotope Ratios Research Articles

An integrated methodology for improving heavy metal risk management in soil-rice system

The lack of linear correlation between regional soil and rice heavy metal (HM) content aggravates the difficulty of risk management in farmland. Hence, an effective HM contamination risk control strategy is urgently required for rice paddy. Here, a novel integrated spatial interaction and risk identification methodology was proposed. Bivariate local indicators of spatial association (BL-LISA) was used to analyze the spatial interaction between soil and rice HM. The mechanism of the spatial interaction pattern was elucidated with lead isotope ratios and redundancy analysis. The rice HM risk was predicted via a Bayesian decision tree (BDT). The spatial interaction patterns were mainly High-Low and Low-High. Thus, there was antagonism between soil and rice HM. Emission sources and sinks accounted for the observed spatial interaction patterns. The parent material contributed 69% to the soil HM content but only 10.2% to that of rice. Seven risk rules and 13 security rules were identified by BDT. The risk identification accuracy of these rules was 96.8% for the overall sample. BL-LISA mapping was combined with BDT to demarcate and classify the risk zones and project differentiated and refined management modes. The risk, potential risk and clean zones comprised 7.8%, 14.1% and 46.6% of the farmland, respectively. The integrated method was superior to other traditional techniques in terms of farm HM risk management and may enhance decision-making in HM risk management for soil-rice system.

Copper alloy production in the Warring States period (475-221 BCE) of the Shu state: a metallurgical study on copper alloy objects of the Baishoulu cemetery in Chengdu, China

Many bronze objects were unearthed in the capital of the Shu state in present-day Chengdu. However, only a few metallurgical studies have been carried out on those objects. This research attempts to study the alloy techniques and possible ore sources of 28 bronze objects recently excavated from the Baishoulu cemetery in Chengdu. Elemental composition and lead isotope ratios were measured, and metallographic observations were conducted. The results indicate that most objects were copper–tin–lead alloys with variable tin and lead content. The samples showed evidence of casting, as well as cold working and annealing techniques. The lead isotope data indicate that multiple lead sources were used in Baishoulu; however, the exact number is not yet known. Most of the lead sources in Baishoulu are the same as those in Zeng state bronze and Chu state bronze. In addition, some of the bronzes came from sources that were widely used in the Central Plains and surrounding regions. This new information aids in understanding the cultural interactions between Shu and other states. Moreover, some bronzes might have used local lead sources. Copper and tin sources were difficult to determine; however, the different trace elemental patterns between Baishoulu and Bayilu bronzes indicate different copper and tin sources might be used. Additionally, copper and lead may originate from different sources in the Shu state. Systematic data are necessary to disclose a possible metal source exchange network involving the Shu state in the Warring States period.

Modified approach for estimating geogenic Pb isotope ratios in soils for metal source apportionment

Lead (Pb) isotope ratios are commonly used to determine the relative contributions of anthropogenic and geogenic sources to metal contaminations in soils. For successful source apportionment, it is critical to obtain a reliable Pb isotope ratio value for each end member. However, the conventional practice for estimating the geogenic Pb isotope ratio can get affected by the anthropogenic Pb, which might produce misleading results. Therefore, this study proposes a modified approach that enhances the reliability of geogenic Pb isotope ratio estimations. To evaluate the feasibility of the proposed approach, laboratory experiments and field soil sample analyses were conducted. In the laboratory experiments, possible transformation of the metal-binding forms was monitored for a year using soils artificially contaminated with Pb and zinc (Zn). The results indicated that the anthropogenic metals in the soil barely transformed into the residual form, and thus, soil samples without less stable metal forms may better represent the original soil minerals. Field soil samples were collected from a metal-contaminated site near a zinc-smelter and were investigated using both the conventional and modified approaches. The modified method involves collecting multiple soil samples along consecutive depths at a location, chemically leaching out the mobile fractions of metals from the samples and determining the converging value of Pb isotope ratio by comparing subsequent values. The results revealed that the modified method gives the Pb isotope ratios which gradually decrease to a certain depth and then converge to a value. On the other hand, the conventional method shows the irregular vertical distributions of Pb isotope ratios possibly due to the infiltrations of anthropogenic Pb. Finally, the application of the modified approach to the zinc-smelter sites was found to yield more reasonable metal source apportionments.

Cinnabar provenance of Chalcolithic red pigments in the Iberian Peninsula: A lead isotope study

AbstractWe report lead isotope data for cinnabar from three Chalcolithic settlements and several ore deposits in the Iberian Peninsula. Lead isotope ratios of cinnabar (vermilion) employed in one Bell Beaker grave at Humanejos (Madrid) plot in the field of the Almaden mining district. Cinnabar from the La Velilla dolmen (Palencia) also plots in the isotopic field of Almaden ores but is also comparable to the closer Miñera de Luna deposit in the Cantabrian Ranges. Cinnabar used in the dolmen of Montelirio (Seville) has an unknown origin, as its new lead isotope ratios obtained do not match with any of the studied ore deposits. We conclude that cinnabar was a well‐known raw material and several ore deposits were mined in the Iberian Peninsula during the Chalcolithic. The societies established at the northern and central parts of the peninsula employed locally sourced cinnabar (<200 km away) in their funerary rituals. The Chalcolithic society settled at the estuary of the Guadalquivir river (south of Spain) employed cinnabar of unknown origin, leaving open the possibility of long‐distance cinnabar trade.

Mapping of atmospheric heavy metal deposition in Guangzhou city, southern China using archived bryophytes

Atmospheric heavy metal contamination is becoming a serious threat to environmental and human health in Chinese megacities. This study evaluated the concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) and Pb isotopic compositions in herbarium and native bryophytes collected from Guangzhou from 1932 to 2018. Relatively low mean metal concentrations were measured for bryophytes collected in the 1930s. The highest mean concentrations of Cd (0.72 ± 0.32 mg/kg), Cu (28.1 ± 9.8 mg/kg), Pb (125.9 ± 62.4 mg/kg) and Zn (273 ± 130 mg/kg) were found in the bryophytes from 1979 to 2000, following the commencement of the Reform and Opening-Up Program in 1978. The mean Pb concentrations (74.7 ± 6.3 mg/kg) decreased sharply from 2001 onwards, following the cessation of leaded petrol across the Chinese mainland in 2000. However, these values are still higher than those in 1950–1978, corresponding to a significant increase in atmospheric Pb emissions from coal combustion, nonferrous metal smelting and motor vehicle petrol consumption in China in the 2000s. The lead isotopic ratios of bryophyte archives (206Pb/207Pb 1.141–1.229, 208Pb/207Pb 2.376–2.482) indicate that lithogenic input and anthropogenic input arising from leaded petrol and industrial emissions have been the main sources of atmospheric heavy metal deposition in the city of Guangzhou over the past 85 years. Herbarium bryophyte can be utilised to reconstruct temporal and spatial shifts in atmospheric heavy metal deposition to better understand and manage the current air quality in Chinese megacities.

Lead isotope evidence of lead supply in ancient Ilduro (second-first centuries B.C.E.)

In this article, we study the provenance of the lead contained in 22 objects found in the excavations conducted since 1998 on the ancient site of Ilduro (Cabrera de Mar, Barcelona), located in the north-east of the Iberian Peninsula. A selection of 12 bronze coins and 10 lead objects recovered from households, workshops, and the public baths of the town were examined by means of Thermal Ionization Mass Spectrometry (TIMS) to document the lead supply and trade networks between, on the one hand, the indigenous peoples known in the classical sources as the Laeetani and, on the other, the Roman provincial administration and the societates that controlled the natural resources, their exploitation, and distribution during the Late Republic (second-first centuries B.C.E.). There is no doubt about Rome’s dependence on the considerable output of the lead and silver from Hispanic mines during this period; however, very little is known on how these mines supplied and affected the lives of the local communities in Hispania over the course of time. This study helps to cover this gap in the existing literature. The results show how all the coins have lead isotope ratios with homogeneous values compatible with an origin in the Spanish mining district of Cartagena-Mazarron. The isotopic composition of the 10 lead objects is not homogeneous, and it is possible to identify three distinct clusters. The samples in cluster 3, which include all the artifacts from the bath complex, can also be attributed to the mining districts of Cartagena-Mazarron, demonstrating that a single mining district supplied the lead required for these two specific initiatives: minting and the construction of the baths. However, the provenance of the lead in the remaining samples (workshops and households) remains unresolved and in some cases might be a consequence of remelting or the direct mixing of leads with different origins. The data from Ilduro points towards the existence of different lead supply patterns in the settlement: directly from the mining exploitations for the public enterprises in contrast to the recycling and mixing practices detected in households and workshops.

Source apportionment of potentially toxic elements in street dust of a coal mining area in Chhattisgarh, India, using multivariate and lead isotopic ratio analysis.

Street dust of Korba, Chhattisgarh, an urban industrial hub in one of India's major coal mining areas, has been analysed for profiling and sourcing of Pb and other potentially toxic elements (PTEs). Lead isotopic ratio of dust, coal, diesel, fly ash and human blood of Korba is being reported for the first time in this study. The mean concentrations (in mg/kg) of Al, V, Cr, Fe, Mn, Ni, Cu, Zn, Cd and Pb were higher than World Background soil and Reference soil USA values and decreased in the order of Al (17000) > Fe (7550) > Mn (2740) > Cr (833) > Ni (571) > Zn (231) > Cu (152) > V (145) > Pb (98.6) > U (7.9) > Cd (1.34). About 25% of the sampled dust had Pb Igeo belonging to class IV category of heavy contamination. Dust from industrial areas was highly enriched with Cr, Cu, Pb and Mn, while those from coal mining areas had high mean V concentration. Principal component analysis extracted Al, Fe, Mn, Zn, Pb and U with the highest loading factors in Component 1 indicative of their lithogenic and anthropogenic sources. The lead isotopic ratios of the dust, coal, diesel, fly ash and eight human blood samples clustered linearly in the 207Pb/204Pb vs 208Pb/204Pb and 206Pb/204Pb vs 208Pb/204Pb plots. Airborne lead deposition from diesel-based traffic exhausts and fly ash contributed to the human blood lead level besides coal mining activities. Geospatially, while Pb was mainly concentrated in the residential, industrial and coal-mining areas, Zn and Mn were mainly distributed in the roadside areas of industrial centres.

Petrological evolution of Karlıova-Varto volcanism (Eastern Turkey): Magma genesis in a transtensional triple-junction tectonic setting

A diffuse and voluminous (>1400 km3) Miocene-Quaternary volcanic activity developed around the Karlıova Triple Junction in East Anatolia as a consequence of collisional tectonics among Anatolia, Arabia and Eurasia continental plates. The volcanic rocks of this region are grouped into three phases of activity: 1) Early Phase (Solhan volcanism; ~7.3–4.4 Ma), with emplacement of alkali basalt to trachyte lava flows and pyroclastic successions; 2) Middle Phase (Turnadağ and Varto volcanism; ~3.6–2.6 Ma), mostly with products with the same compositional range plus minor dacites and rhyolites, and 3) Late Phase (Özenç volcanism; ~2.6–0.5 Ma), with emplacement of alkali basaltic, hawaiitic and mugearitic lavas and dykes.Primitive Mantle-normalized patterns of the three rock groups share an enriched LILE and depleted HFSE contents, with overall positive spikes of Pb and mildly fractionated LREE/HREE trends showing more similar affinity to global subducting sediments rather than to magmas emplaced in mid-plate settings (i.e., OIB). Initial Sr isotopic ratios of the least evolved compositions range from values lower than BSE (87Sr/86Sri = 0.7041) to radiogenic compositions (87Sr/86Sri = 0.7050). They reflect either FC-like processes, with 87Sr/86Sri up to 0.7064, or closed system fractional crystallization, with 87Sr/86Sri = 0.7046–0.7049. Initial Nd are higher than ChUR estimate for the most and the least evolved compositions (143Nd/144Ndi = 0.51267–0.51280), indicating provenance from isotopically depleted sources. Lead isotopic ratios are characterized by a remarkable homogeneous 206Pb/204Pb (18.95–19.04), with 207Pb/204Pb (15.65–15.72) and 208Pb/204Pb (38.87–39.21) slightly above the Northern Hemisphere Reference Line, pointing towards the EMII end-member.Geochemical modelling for the least evolved volcanic units indicate the likely generation from an amphibole-bearing spinel-lherzolitic source. P-T calculations for partial melting calculations gave lithospheric pressures for initial magma generation (0.8–1.3 GPa). Possible cause of melting might be related to passive upwelling of asthenosphere as a response to the local extension linked to the development of North Anatolian and East Anatolian Fault Zones. Anyhow, volcanic units from the KTJ display only limited geochemical signatures of garnet-bearing sources, or any HIMU-OIB like characteristics, as instead observed in the other portions of the Eastern Anatolia.The long-lasting complex tectonic evolution of the Eastern Anatolia is responsible for the large geochemical variability of the magmatic products. However, the general characteristics of KTJ volcanic rocks are mainly dominated by subduction-related signatures, with most of the primary magma characteristics having been heavily masked by fractionation and crustal assimilation processes.

Use of Lead Isotopic Ratios as Geographical Tracer for Lambrusco PDO Wines.

In this study, the lead isotope signature was tested with the aim to verify its potential as geographic tracer for wine production and particularly for the Lambrusco PDO wines of the province of Modena (Italy). A solid phase extraction procedure, for separating lead from the investigated matrices, soil and wine, was optimized. Furthermore, different mathematical models, based on an exponential law and internal or external correction approach, were evaluated for the correction of instrumental mass dependent fractionation. The optimized analytical procedure yielded isotopic ratio data relative to the lead NIST 981 standard, 208Pb/206Pb = 2.16664 and 207Pb/206Pb = 0.914645, in good agreement both with the tabulated values and with the most recent literature data. Measured isotope ratio data highlight the contribute of multiple lead sources in bottled wine but different from the one present in soils.

A ‘match–no match‘ numerical and graphical kernel density approach to interpreting lead isotope signatures of ancient artefacts

A new method for interpreting lead isotope ratios of artefacts is presented: a numerical and graphical ‘match–no match‘ with possible raw materials. By calculating the definite integral under the kernel density estimate plot of different mining districts, using open‐access software and legacy data, the relative probability that an object is made of an ore is indicated. A match with the reference data set may indicate the true origin, while no match indicates an unknown origin, that is, not present in the data set of mineral resources. Likewise, the composite or recycled nature of artefacts can be investigated in a probabilistic manner.

Lead isotopes link copper artefacts from northwestern Botswana to the Copperbelt of Katanga Province, Congo

Copper was highly valued in sub-Saharan Africa for jewellery and as a store of wealth, but was rarely used for tools or weapons. The Central African Copperbelt is one of the world's largest copper deposits, and is known to have been mined since at least 400–600 cal CE, but has seen very little archaeological investigation. We measured lead isotope ratios and trace element concentrations in 20 copper objects, dating between ca. 650 cal CE and ca. 1200 cal CE, from two sites in the Tsodilo Hills in northwestern Botswana. The results show unequivocally that almost all derive from Copperbelt ore deposits in Katanga Province, Democratic Republic of the Congo, at least 1050 km from Tsodilo. Our results are very similar to those recently obtained for a suite of 45 copper ingots, dated between 9th and 18th centuries cal CE, most of which are from cemeteries in the Upemba Depression, about 200 km north of the Copperbelt (Rademakers et al., 2019).

Multi‐isotope fingerprints (O, Sr and Pb) in archaeological animal bone bioapatite: Similarity search and the suitability for provenance analysis in a geologically complex Alpine region

Multi‐isotope fingerprints in the bioapatite of archaeological skeletons are mostly superior over single isotope analyses for provenance studies. Gaussian mixture model (GMM) clustering is a novel tool for a similarity search among multidimensional data sets and at the same time permits the evaluation of the structural importance of particular isotopic ratios in the data set. We applied three GMM clustering experiments on multi‐isotope fingerprints—stable strontium (Sr), lead (Pb) and oxygen (O) isotopic ratios—established in 217 archaeological animal bones excavated along a specific transect across the European Alps. This reference region had been in use since prehistoric times by humans who crossed the Alps from north to south, and vice versa. The resulting clusters permit a spatial assignment of the specimens with a very high probability, in particular with regard to the geological complexity of the region. A combination of Sr with Pb stable isotopes led to an optimal differentiation between the southern and northern Alpine forelands that cannot be distinguished from each other by 87Sr/86Sr ratios alone, while the contribution of δ18O is not particularly high. The isotopic mapping and subsequent cluster analysis is suitable for the analysis of archaeological human finds and the reconstruction of the direction of transalpine mobility and trade.

Using lead isotope ratios to distinguish between samples of diffrent uranium mines

abstractIn this work, a total of twenty samples selected for investigation originate from South Africa and Namibia uranium mines. The aim of this study was to determine whether the lead ratios measured in particular samples could be used to attribute the uranium sample to the production or reprocessing plant. Measurements were carried out using an inductively coupled plasma mass spectrometer PerkinElmer NexION 2000. The precision obtained for the 208Pb/206Pb ratio, the 207Pb/206Pb ratio and the 204Pb/206Pb ratio values was considerably lower than 0.02% demonstrating the applicability of the technique for Pb isotope ratio studies.

Lead isotope ratios as tool for elucidation of chemical environment in a system of Macrolepiota procera (Scop.) Singer-soil.

The analysis of isotope ratios of lead in the mushrooms and soil, where they were grown, assisted with a principal component analysis, offered a new perspective for understanding possible chemical environment in a real setup of those compartments. The content of lead and its isotope compositions were determined in soil samples and mushroom Macrolepiota procera from unpolluted area of Mountain Goč, Serbia. Sequential extraction procedure based on the Commission of the European Community Bureau of Reference (BCR) was applied on soil samples in order to determine the distribution of lead in the labile and un-labile fractions of the soil. Caps and stipes of mushrooms were subjected to microwave acid-assisted digestion prior to measurements by inductively coupled plasma quadrupole mass spectrometer for determination of lead content and lead isotope ratios. Information about the chemical fractionation of Pb in soil, Pb isotopic data from soil fractions and fruiting bodies allowed a more detailed insight on the uptake mechanisms. Lead was predominantly associated with reducible fraction (~ 60%). Only its small portion (∼ 1%) was present in the exchangeable and acid-extractable fractions suggesting the low mobility of Pb. Lead isotope analysis revealed the presence of anthropogenic lead in the surface soil. Significant lower 206Pb/207Pb compared with other fractions was found in exchangeable and acid-soluble fraction (1.331 ± 0.010), which corresponds to the isotope ratio of European gasoline. The highest 206Pb/207Pb ratio was observed in reducible fraction (1.162 ± 0.007), while in oxidizable and residual fraction, those values were similar (1.159 ± 0.006 and 1.159 ± 0.004, respectively). Distinction of exchangeable and acid-extractable fractions from others was also confirmed, for the first time, by principal component analysis. The analysis of four isotope ratios (206Pb/207Pb, 208Pb/206Pb, 206Pb/204Pb, and 207Pb/204Pb) indicated that the analyzed M. procera accumulates lead from the first two fractions of topsoil layers.

Surface topography, mineralogy, and Pb isotope survey of wheel weights and solder: Source of metal contaminants of roadways and water systems

Wheel weights and solders are among the most important anthropogenic lead sources in modern society. Characterization of size, shape, and stages of degradation of wheel weights and solders by scanning electron microscopy provides fundamental knowledge toward better understanding of processes related to abrasion, dissolution, and transfer of metallic lead to the surface environment. Our studies of wheel weights identified partially abraded and chemically corroded textures, with coatings of reconstituted Pb particles, including litharge (PbO) and/or plattnerite (PbO2), in a matrix of soil components, mainly clays, feldspars, silica, and iron-oxides. Pb oxide particles abraded from wheel weights have a major component of <1 μm-size particles and consist of acicular needles and hair-like crystals are of concern because the size and particle shapes are known to have significant adverse health impacts if ingested, inhaled, or imbedded in the human body.Pb isotope analysis (by TIMS and HR-ICPMS) provides a way to identify the main lead exposure pathways if wide differences in isotopic ratios exist among possible local sources. Lead isotopic ratios for wheel weights from the U.S. plot along narrow arrays in plots of 206Pb/207Pb (~1.130–1.230) vs. 208Pb/207Pb (~2.410–2.470). The apparent trend in the 208Pb/207Pb and 206Pb/207Pb plot implicates a lead source from central U.S. from Mississippi Valley-type deposits, and a less radiogenic endmember which may link to an international lead source, such as from deposits of China. Wheel weights and corresponding leachates are analytically indistinguishable. Degradation of wheel weight particles will influence the Pb isotopic composition of local surface and groundwater regardless of whether the contribution is from solid particles, derived from grain erosion, or from dissolved Pb. The legacy of past and current uses of lead metal in manufactured products will continue to be of global concern for the foreseeable future because Pb-rich products, such as wheel weights and solders, remain commercially available through both primary and secondary global markets.

Lead isotope ratios in Podzol profiles as a tracer of pollution source in the subalpine zone of the Karkonosze National Park, Sudety Mts (south-western Poland)

The Karkonosze National Park (south-western Poland) represent central European medium-elevation mountains. At the end of the twentieth century, an ecological disaster was observed in this nature reserve, resulting in the defoliation of large areas of spruce forest. One of the considered reasons for this phenomenon was contamination with heavy metals. The aim of this study was to determine the origin of lead (lithogenic versus several specific anthropogenic sources) occurring in the soils of the highest located parts of the Karkonosze Mts. Lead concentrations and its isotope ratios were investigated in nine Podzol profiles located in the subalpine zone (1200–1400 m a.s.L.) of the Karkonosze Mts. Concentrations of total lead and its isotopes were measured in particular genetic horizons; then lead isotope ratios were calculated. On the basis of lead isotope signatures known from literature data, different anthropogenic sources of this element have been assessed (emissions from coal combustion, mining, metallurgy, and fuel combustion). The results obtained revealed the highest Pb concentrations (121.0–353.0 mg kg−1) in the surface horizons. The podzolization process, differentiating soil profiles into eluvial (Es) and illuvial (Bh and Bs) horizons, has contributed to different concentration of lead through the profile. The concentrations of this element in eluvial, illuvial Bh, and parent material horizons were 15.5–28.4 mg kg−1, 25.8–55.6 mg kg−1, and 8.7–29.6 mg kg−1, respectively. The Pb isotope composition determined in the ectohumus horizons and eluvial horizons showed that about 86–95% of lead existing in these surface horizons originated from emissions resulting from the burning of coal exploited in Poland and the Czech Republic. The Pb isotope signatures of lead present in the illuvial horizon (Bs) and parent material (C) pointed to the lithogenic origin of this element. The results obtained indicated that higher-elevation areas of the Karkonosze National Park have been contaminated with lead from long distance emissions. Pollution with lead has been limited only to ectohumus and eluvial horizons, although the soil-forming process contributed to translocation of lithogenic lead down the soil profile to the illuvial Bh horizon.

Lead astray: The potentials and pitfalls of lead isotopes in a New Zealand colonial burial context

Lead isotopes can be used to identify migrants in archaeological sites, and are particularly useful when individuals may have migrated from areas of high anthropogenic or environmental lead into lower-lead concentration environments. For this reason they are ideal for identifying first European settlers (coming from a UK Industrial Revolution context) to colonies such as New Zealand. In this study, however, we highlight how ornate Victorian burial practices may introduce lead into the burial environment. This introduced lead masks the in vivo lead isotope ratios, negating its use as an indicator of foreign origins. We show that pressed pewter (tin-lead alloy) coffin strips at the colonial site of St. John’s Milton (SJM) render all individuals isotopically “European”, despite all children at the site having been born in New Zealand.

Geology, geochronology, and S-Pb-Os geochemistry of the Alastuo gold deposit, West Tianshan, NW China

The Alastuo gold deposit, located in the Narati region of the Chinese West Tianshan, is a newly discovered gold deposit within the world-class Tianshan gold belt. The gold mineralization is hosted by an Early Carboniferous granodiorite intrusion and controlled structurally by subsidiary faults of the transcrustal North Narati Fault. The deposit consists of auriferous alteration assemblages and minor vein ores. Field relations and petrographic data suggest four stages of mineralization with gold precipitated coevally with quartz, chlorite, epidote, pyrite, and galena during the second and third stages that are characterized by tectonic transformation from ductile shearing to brittle deformation. The temperature range of gold precipitation is estimated to be 280–330 °C using chlorite geothermometry. Ten auriferous pyrite samples yielded a well-defined Re-Os isochron age of 325 ± 3 Ma and two sericite samples yielded plateau-like 40Ar/39Ar ages of 321.7 ± 3.0 Ma and 321.2 ± 2.8 Ma. These consistent ages suggest that the gold mineralization in the Narati region was emplaced in a transitional regime from subduction to continental collision between the Tarim block and Middle Tianshan terrane (325–310 Ma), rather than during the post-collisional stage as in most part of the Tianshan gold belt. Gold-bearing pyrite has an initial Osi value of 0.7 ± 0.1 and lead isotopes ratios of 17.897 to 18.723 for 206Pb/204Pb, 15.474 to 15.643 for 207Pb/204Pb, and 37.522 to 38.299 for 208Pb/204Pb, while samples of pyrite, galena, and sphalerite have 34SV-CDT of +1.9 to +7.8‰. The isotope data suggest that the sulfur and metals are most likely derived from mixed mantle and crustal sources including metamorphic devolatilization of subducted oceanic slab and overlying sedimentary rocks. The mineralization styles, structural controls, metal and sulfur sources, and the timing of gold mineralization with respect to the orogenic event all suggest that the Alastuo gold deposit represents an orogenic type deposit. This newly recognized Carboniferous orogenic gold mineralization event calls for a re-evaluation of the gold metallogeny in the Middle Tianshan.

Temporal variation of trace elements, rare earth elements and Pb isotope ratios in sediment core from Kiel Bay, western Baltic Sea

Environmental contextTrace elements in coastal environments represent an environmental concern and their monitoring in sediment cores provides insight into their historical sources. A well-dated core from Kiel Bay, western Baltic Sea, provided trace element data, including lead, cadmium, rare earth elements, mercury and methyl mercury. Lead and mercury isotope ratios were useful for the apportionment of pollution sources, indicating that coal burning was a major contributor. AbstractWe present a comprehensive study on the variation of trace elements (TEs) and rare earth elements (REEs) in a well-dated sediment core from Kiel Bay, western Baltic Sea. Mass fractions of 34 elements (major and trace) together with other relevant parameters, such as organic carbon and grain size, were determined in a 20-cm core that covers the last century. Enrichment factors and geoaccumulation indices were determined to assess the possible influence of anthropogenic inputs on element distribution. The obtained results show that the highest enrichment of TEs occurred in the period 1917–1970 especially for the priority elements as Hg, Cd and Pb. Determination of methylmercury (MeHg) was also performed, as it showed the highest content in surface samples. The MeHg percentages ranged from 0.02 to 1.2% of the total Hg. REEs, which are nowadays considered as new emerging contaminants, did not reveal high enrichment attributable to anthropogenic influences, but provided useful baseline information for future monitoring of the area. The study of the Pb isotopic composition proved to be a valuable tool in determining the Pb pollution source, and revealed Pb in the layers that showed the highest enrichment came mainly from coal burning. Mercury isotopic signatures in the sediment core were used as a tool to identify the sources of Hg pollution. An isotope mixing model based on mass-dependent (MDF) and mass-independent fractionations (MIF) identified coal burning as the most probable dominant source for Hg anthropogenic contamination in the area.

Bronze production in the Ancient Chengdu Plains: A diachronic metallurgical perspective on a separate cultural region

• Novel, diachronic research on bronze production in the Chengdu Plains. • Different lead sources and possibly a single copper source used for 600 years. • New evidence on the origins of Sanxingdui bronze. As one of the most important separate cultural regions in ancient China, the Chengdu Plains provide a unique example to explore the development of bronze production. We analysed 37 bronze objects from the Western Zhou period to the Tang Dynasty in the Chengdu Plains for elemental compositions, microstructure, and lead isotope ratios. We referred to bronze data from the Sanxingdui sacrificial pits to compare results that demonstrated that most samples from the Chengdu Plains were Cu-Pb-Sn alloys with variable tin and lead content. The alloy technique used in the Warring States period bronzes, which were uncovered in the Baishoulu cemetery, differed from the techniques used in other samples. Casting is the major technique used for all types of objects in different periods. The only cold-worked and annealed sample found so far was a Chu-style vessel. Different lead sources and a possible single copper source were constantly used in local bronze production from the Western Zhou Dynasty to the Warring States period (more than 600 years). Some coins in Han and Tang Dynasty potentially also used these same lead sources. Comparison with Sanxingdui bronze suggests that both lead and copper sources of Sanxingdui bronzes are different from the later metal sources. We therefore propose that the Sanxingdui bronze might not have been locally made or was made with outside materials. Our study suggests that diachronic study on bronze production could provide clues to solve more archaeological questions other than the development of bronze production.