Lead Isotope Data Research Articles

Reconstructing the trade history: provenance study of Han bronze mirrors in and out of Han China

A rapidly increasing number of bronze mirrors dated to the Chinese Han dynasty (202 BC – AD 220), known for their unique decorative patterns and highly developed alloying techniques, have been widely discovered in both China and beyond, providing fresh materials and scientific data to revisit their geological provenance, production and circulation network along the ancient Silk Road. In this paper, 47 bronze mirrors unearthed in the southeastern provinces of China, including Zhejiang, Anhui and Fujian provinces, have been characterized by typo-chronology, lead isotopic analysis, compositional analysis and metallography. A much wider comparative study is also carried out through a combination of data from China, Japan, Central Asia, and Southeast Asia, leading to a more updated lead isotopic database of the Han mirrors spreading out of China in various directions. Compared with the traditional ‘optimal’ model based on the Han mirrors recovered in Japan, the current study contributes several key changes in the bronze mirror production of the Han dynasty. The systematic analysis of the alloy composition, trace elements and typological studies shows that the bronze mirror industry shifted towards a more standardized production in the middle to late Western Han Dynasty. In contrast to the substantial change of non-mirror bronze productions, the similar distribution of lead isotope data in early and middle to late Western Han mirrors suggests that the ‘official monopoly of salt and iron’ policy was less effective for the management of lead involved in mirror production. Bronze mirrors dated to middle to late Western Han discovered outside Han-China, such as Japan, Thailand, Afghanistan, Xiongnu and the ancient Dian Kingdom, appear to be subjected to a more specific type of lead as a result of the state-centralized policy of the Western Han court.

Lead isotopes of prehistoric copper tools define metallurgical phases in Late Neolithic and Eneolithic Italy.

The diffuse presence of small copper ore deposits in the Alpine area, mostly exploited since Late Medieval times, led most scholars to assume that these deposits may actually be active much earlier and that many of the circulating prehistoric metal objects found in the area were produced with local copper sources. This assumption was recently validated for the Recent Bronze Age through the use of lead isotope tracers, and well supported by the archaeometallurgical evidences found in the South-Eastern Alps. However, the scarcity of available lead isotope data for pre-Bronze Age metals precluded to date the reconstruction of the metal flow through the Late Neolithic and Eneolithic (or Copper Age). Based on 49 new analyses of important archaeological objects from the Alpine region, the Po River Valley and Central Italy, mostly axes dated from the Late Neolithic to the Late Eneolithic, here we show that the diffusion of copper in Northern Italy (approximately 4500-2200 BC) includes three major periods of metal use and/or production, each related to specific ore sources. The South Alpine copper was massively used only starting from the middle of the 3rd millennium BC, in connection or slightly earlier than the Beaker event.

The Bougrine Zn-Pb deposit, the largest salt diapir-related Mississippi Valley-type deposit in the Eastern Maghreb salt diapir province, Tunisia

The Bougrine Zn-Pb sulfide deposit (5.5 Mt @ 12 % Zn + 2.5 % Pb) in the Eastern Maghreb salt diapir province of Tunisia is located at the northeastern end of the Lorbeus-Bougrine diapir. The several-km large diapir is composed of Triassic evaporite that intruded about 10 km-thick Jurassic and Cretaceous marine sedimentary rocks during the Cretaceous and Tertiary. Mineralization occurs in breccia zones at the contact with the Triassic diapir and in the peridiapiric Cretaceous strata. Most of the ore is stratabound (F2 orebody) with microsphalerite disseminations in organic-rich laminated black limestone of the Cenomanian-Turonian Bahloul Formation, where sphalerite occurs as infill of Globigerina shells, as massive replacement of Globigerina-rich layers, as banded colloform sphalerite and in voids as euhedral, coarse-grained crystals together with skeletal galena and minor marcasite. Abundant degraded oil seepages in the orebodies and their host rocks testify to the existence of a (former) hydrocarbon reservoir.The various sphalerite generations have highly variable Mn and Fe contents; Cd has an average content of 445 ppm; As and Hg contents are in the 200 ppm range; Tl content is about 40 ppm; Ga content is about 10 ppm; and In content is consistently <1 ppm. Fluid inclusions in celestite, coarse-grained late-stage sphalerite and calcite indicate moderate fluid salinities (16 ± 2 wt% NaCl eq.) and moderate temperatures (85 to 146 °C). The empirical trace-element sphalerite geothermometer gives 184 ± 38 °C for the main-stage microsphalerite and the banded colloform sphalerite which have no measurable fluid inclusions.A wide range of δ13C (-13.6 to 5.6 ‰) and δ18O (-19.8 to 33 ‰) values is observed in ore-stage and post-ore calcite. Ore-stage calcite commonly has negative δ13C values reflecting involvement of carbon from organic matter; its δ18O composition with an average of 22.6 ± 2 ‰ (19.7 to 26.0 ‰) may be explained by a moderate-temperature hydrothermal fluid. There is no systematic δ34S variation between and across the different styles of mineralization. The range of δ34S of 6–19 ‰ with a mean of 13 ‰ is close to the δ34S value of local and regional Triassic marine sulfate (δ34S = 16 ‰). Thermochemical reduction of Triassic sulfate, likely mediated by hydrocarbons, is the most probable source for sulfur in the ores. Lead isotope data on galena are within a narrow field of upper crustal signature (206Pb/204Pb = 18.71–18.77; 207Pb/204Pb = 15.66–15.70; 208Pb/206Pb = 38.81–38.97) indicating a homogeneous ore fluid.The major characteristics of the Bougrine ore deposit are typical of Mississippi Valley type Pb-Zn deposits and indicate large-scale fluid circulation likely related to stacking and uplift in the northern Tunisian Nappes Zone during the Miocene. Both the hydraulic load of meteoric water and over-pressured basinal and basement fluids during compressional movements favored southward fluid migration along basement discontinuities and most permeable strata in the Mesozoic-Cenozoic sedimentary pile. Low-pressure domains around salt diapirs in a rifting environment allowed focused upward fluid flow, and the hydrocarbon reservoir of the Bahloul Formation then provided the geochemical trap for efficient base metal deposition.

Lead isotopes in New England (USA) volcanogenic massive sulfide deposits: implications for metal sources and pre-accretionary tectonostratigraphic terranes

Lead isotope values for volcanogenic massive sulfide (VMS) deposits provide important insights into metal sources and the nature of pre-accretionary tectonostratigraphic terranes and underlying basements. Deposits of this type in New England formed in diverse tectonic settings including volcanic arcs and backarcs, a supra–subduction zone arc, a rifted forearc foreland basin, and a rifted continental margin. Following VMS mineralization on or near the seafloor, components of the tectonostratigraphic assemblages—volcanic ± sedimentary rocks, coeval intrusions, sulfide deposits, and underlying basements—were diachronously accreted to the Laurentian margin during the Paleozoic. Lead isotope data for galena show relatively large ranges for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb. Evaluation of potential lead sources, using for comparison Pb-isotope data from modern and ancient settings, suggests that principal sources include the mantle, volcanic ± sedimentary rocks, and deeper basement rocks. Integration of the Pb-isotope values with published data such as Nd isotopes for the volcanic rocks and from deep seismic reflection profiles points to the involvement of several basements, including those of Grenvillian, Ganderian, Avalonian, and West African (and (or) Amazonian) affinity. Clustering of Pb-isotope data for VMS deposits within individual Cambrian and Ordovician volcanic and volcanosedimentary settings, delineated by differences in 206Pb/204Pb and µ (238U/204Pb) values, are consistent with lead derivation from at least four and possibly five different tectonostratigraphic assemblages with isotopically distinct basements. Collectively, our Pb-isotope data for New England VMS deposits provide a novel window into the nature of subarc basement rocks during pre-accretionary sulfide mineralization outboard of Laurentia during early Paleozoic time.

Magma-related origin for Pb–Zn–Ag vein formation at the Aerhada deposit, Inner Mongolia, NE China: Constraints from fluid inclusion, C–H–O–S–Pb isotopic compositions, and geochronological studies

The Aerhada Pb–Zn–Ag deposit is on the western margin of the Great Xing’an Range in NE China. Prior studies on this deposit lack information regarding precise mineralization age and convincing genetic interpretation, which limits both the prospecting at Aerhada and the reconstruction of the regional metallogenic evolution. Based on a detailed field investigation and microscopic observation, in this study, our aim was to determine the origin and evolution of the hydrothermal system and the timing of magmatism and mineralization, as well as to develop a possible metallogenic model, by revealing information regarding the mineralization paragenetic relationship, fluid inclusions, H–O–C–S–Pb isotopes, and sphalerite Rb–Sr and zircon U–Pb ages. Three successive mineralization stages were recognized: stage I quartz-arsenopyrite-pyrite, stage II quartz-sphalerite-galena, and stage III fluorite-calcite-pyrite. Four types of fluid inclusions were also identified in host minerals: CH4-rich two-phase, halite-bearing, vapor-rich two-phase, and liquid-rich two-phase. Fluid inclusion and microthermometric results showed that the homogenization temperatures were 287–341 °C for stage I, 237–291 °C for stage II, and 162–230 °C for stage III, with respective salinities of 1.7–40.2 wt%, 6.7–10.9 wt%, and 4.2–8.8 wt% NaCl equivalent. The δ18Ofluid and δDfluid values of quartz in stage I (δ18Ofluid = 8.6–10.3 ‰, δDfluid = -126.6 to −124.3 ‰) indicated that initial magmatic water interacted with organic strata, while decreasing the values of quartz in stage II (δ18Ofluid = 3.9–6.8 ‰, δDfluid = -129.1 to −127.6 ‰) and calcite in stage III (δ18Ofluid = -3.5 to −1.0 ‰, δDfluid = -115.5 to −113.4 ‰), showing a trend of dilution and cooling by meteoric water. The negative δCfluid values (δCfluid = -15.9 to −12.6 ‰) of quartz fluid inclusions from stages I and II emphasize that organic carbon was added to the hydrothermal system through water–rock interactions. The δ34S values (δ34Ssulfides = 1.2–7.5 ‰) and lead isotope data of sulfides (206Pb/204Pb = 18.153–18.684, 207Pb/204Pb = 15.370–15.750, 208Pb/204Pb = 37.653–39.301), coupled with those of the hidden biotite granite and Devonian strata, indicate that the ore-forming material was primarily derived from magma and wall rocks. The sphalerite samples produced a Rb–Sr isochron age of 154.1 ± 3.5 Ma (2σ, MSWD = 0.82, n = 8), which was like the zircon U–Pb age of biotite granite (156.3 ± 1.4 Ma, 2σ, MSWD = 0.89, n = 14). Combining the alteration pattern, fluid inclusions, and isotopic and geochronological studies, it was concluded that Aerhada is a magma-related hydrothermal Pb–Zn deposit formed under the post-collision extension setting following the Mongol–Okhotsk Ocean closure during the Late Jurassic period. The proposed metallogenic model is expected to assist in the exploration and development of polymetallic mineralization in the Great Xing’an Range.

Origin of Archean Pb isotope variability through open-system Paleoarchean crustal anatexis

Abstract Lead isotopic data imply that thorium and uranium were fractionated from one another in Earth’s early history; however, the origin of this fractionation is poorly understood. We report new in situ Pb isotope data from orthoclase in 144 granites sampled across the Archean Yilgarn craton (Western Australia) to characterize its Pb isotope variability and evolution. Granite Pb isotope compositions reveal three Pb sources, a mantle-derived Pb reservoir and two crustal Pb reservoirs, distinguished by their implied source 232Th/238U (κPb). High-κPb granites reflect sources with high 232Th/238U (~4.7) and are largely co-located with Eoarchean–Paleoarchean crust. The Pb isotope compositions of most granites, and those of volcanic-hosted massive sulfide (VHMS) and gold ores, define a mixing array between a mantle Pb source and a Th-rich Eoarchean–Paleoarchean source. Pb isotope modeling indicates that the high-κPb source rocks experienced Th/U fractionation at ca. 3.3 Ga. As Th/U fractionation in the Yilgarn craton must have occurred before Earth’s atmosphere was oxygenated, subaerial weathering cannot explain the apparent differences in their geochemical behavior. Instead, the high Th/U source reflects Eoarchean–Paleoarchean rocks that experienced prior high-temperature metamorphism, partial melting, and melt loss in the presence of a Th-sequestering mineral like monazite. Archean Pb isotope variability thus has its origins in open-system high-temperature metamorphic processes responsible for the differentiation and stabilization of Earth’s continental crust.

Pb-bearing Cu-(Fe)-sulfides: Evidence for continuous hydrothermal activity in the northern Olympic Cu-Au Province, South Australia

Lead-isotope data were obtained for a population of Pb-chalcogenides (galena, clausthalite and altaite) and Cu-(Fe)-sulfides in Cu-(Fe)-sulfide mineral separates from the Prominent Hill iron-oxide copper gold deposit, Mt Woods Inlier, South Australia. Each mineral displays wide variability in 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios, ranging from moderately radiogenic Pb signatures to strongly radiogenic. Any contribution from non-radiogenic (common) lead at the time of initial deposit formation (1600–1585 Ma) is minor. Lead is overwhelmingly derived from the decay of U, with a minor contribution from the decay of Th also present within the ores. The heterogenous nature of the recorded Pb isotope values suggests a mixing of isotope signatures during repeated cycles of fluid-assisted dissolution, remobilisation and reprecipitation of U- and Pb-bearing phases. Hydrothermal experiments showed that the incorporation of Pb-chalcogenide (galena) occurs rapidly (days) at relatively mild conditions (≤150 °C), via precipitation in reaction-induced porosity formed during coupled dissolution reprecipitation reactions of the host Cu-(Fe)-sulfides. Hence, even minor hydrothermal activity may result in some trapping of radiogenic Pb by pre-existing Cu-(Fe)-sulfides. Construction of Pb-Pb pseudo-isochrons from the data supports these assessments, returning a range of possible (theoretical) ages (0–0.535 Ga) for Pb-chalcogenide formation. An additional (two-stage) Pb evolution model is preserved by the data with separation of each reservoir from the bulk silicate earth at ∼ 830 Ma and mixing of the two reservoirs at ∼ 500 Ma. Although the Pb-isotope data can be interpreted as resulting from a number of discrete events that generated regional-scale fluid flow, near-continuous Pb (re)-mobilisation at the nm- to deposit-scales is an equally valid interpretation, and is also consistent with observations of modern radionuclide mobility in the ores. The observations made within this study should be considered when discussing the mobility of elements within and between mineral phases in ore-forming systems. They show that many mineral phases, particularly the sulphide mineral phases discussed here, should not be considered as closed systems, but potentially, as systems in which chemistry and mineral stoichiometry evolve continuously over geological time.

A Partial Prehistory of the Southwest Silk Road: Archaeometallurgical Networks along the Sub-Himalayan Corridor

Historical phenomena often have prehistoric precedents; with this paper we investigate the potential for archaeometallurgical analyses and networked data processing to elucidate the progenitors of the Southwest Silk Road in Mainland Southeast Asia and southern China. We present original microstructural, elemental and lead isotope data for 40 archaeological copper-base metal samples, mostly from the UNESCO-listed site of Halin, and lead isotope data for 24 geological copper-mineral samples, also from Myanmar. We combined these data with existing datasets (N = 98 total) and compared them to the 1000+ sample late prehistoric archaeometallurgical database available from Cambodia, Laos, Thailand, Vietnam and Yunnan. Lead isotope data, contextualized for alloy, find location and date, were interpreted manually for intra-site, inter-site and inter-regional consistency, which hint at significant multi-scalar connectivity from the late second millennium bc. To test this interpretation statistically, the archaeological lead isotope data were then processed using regionally adapted production-derived consistency parameters. Complex networks analysis using the Leiden community detection algorithm established groups of artefacts sharing lead isotopic consistency. Introducing the geographic component allowed for the identification of communities of sites with consistent assemblages. The four major communities were consistent with the manually interpreted exchange networks and suggest southern sections of the Southwest Silk Road were active in the late second millennium bc.

Composition, raw material provenance, and manufacture of a unique late Roman silver folding stand (quadripus) from Kőszárhegy, Hungary

The late Roman silver quadripus from Kőszárhegy (Fejér County, Hungary) is the only known silver folding stand from the Late Roman Imperial Age, dated to the fourth century AD. Archaeological evidence indicates that the quadripus is closely related to the Seuso Treasure. Elemental composition and lead isotope analyses of samples taken from the various parts of the folding stand were performed by using LA-QICP-MS and MC-ICP-MS methods in order to determine the provenance of raw material used and the production technology. The silver quadripus consists of rather pure silver (92.5–96.5%) intentionally alloyed with copper. The different trace element composition (Bi, Au, Pb) of the various parts (base, lower part, griffin, upper part, finial, cross bands) indicates the use of different silver batches implying that the various parts were made separately, and then soldered together with hard solders. The same parts of the two original feet are very similar regarding their elemental composition and lead isotope ratios suggesting series production. The nearly constant gold and lead contents of the object indicate that not re-used or re-melted, but primary, cupelled silver was used for manufacturing. The lead isotope ratios of the quadripus cover a quite narrow range (206Pb/204Pb = 18.514–18.717; 207Pb/204Pb = 15.645–15.667; 208Pb/204Pb = 38.592–38.817). Comparing our results to the lead isotope data of the European lead-silver ores, and taking into consideration the archaeological evidences, the silver used for manufacturing the quadripus could come from the Balkan region.

1600 BC: Fårdrup and Valsømagle-Type Axes and the First Evidence of Southern Alpine Metal

Abstract This article presents the results of a comprehensive investigation of Fårdrup and Valsømagle-type shafthole axes from Denmark and southern Sweden. The combination of artefact style and typology with trace element and lead isotope data in the analysis has provided new insights into the chronological relationship between these two axe types. This way, we open a new window to long-standing debates surrounding these artefact types. Did Fårdrup and Valsømagle type axes evolve parallel, or did they replace each other chronologically in evolutionary progression? The archaeometallurgical dataset presented in this article includes more than 70 axes. Four axes have been analysed for this article. This large set of data is then assessed against a background of metal analyses which trace the long and winding evolution of the use of bronze in Scandinavia c.2300–1400 BC. Combining these two datasets shows the provenance of the metals and, thus, provides insights into metallurgical developments at the onset of the Nordic Bronze Age (NBA, c.1600 BC). In particular, the shafthole axes offer new evidence of the use of a novel type of copper from the East Alpine region based on chalcopyrite ores. The first occurrences of this low-impurity copper in southern Scandinavia appeared around 1700 BC. However, it would eventually become dominant in c.1600 BC, when the local production of shafthole axes began. Significantly, a fraction of the shafthole axes – Fårdrup and Valsømagle-types alike – consist of low impurity copper most likely derived from the Italian Alps (Trentino), which was absent in earlier periods. By NBA II 1500–1300 BC, most metal objects can be related to this northern Italian copper. We interpret this in terms of chronology: Fårdrup (⁓Koszider) and Valsømagle (⁓Tumulus B1) consisted of similar types of copper, which had declined by the onset of NBA II, all indicating that Fårdrup and Valsømagle style objects flourished before the beginning of NBA II (c.1500 BC). The small influx of north Italian copper in the axes indicates that its arrival began before the breakthrough of NBA II. Therefore, while the results of the metal analyses cannot exclude chronological differences between the two shafthole axe types over the 16th century BC, it is probable that their timelines coincided. In summary, our results display correlations between societal developments and thresholds on the one hand and metal provenances and trade routes on the other.

Lead isotope reveals the mineral source change of late Bronze Age bronze mirrors excavated in Hunan Province, Southern China

The late Bronze Age was the first golden period for bronze mirror production in ancient China. In this paper, scientific analysis and research were carried out on 28 late Bronze Age bronze mirrors excavated in Hunan Province, Southern China. All bronze mirrors are Cu-Sn-Pb materials, and their lead isotope data are in line with the characteristics of common lead. Among them, 4 bronze mirrors containing metal bodies all show bronze casting structures with high tin features, and there are some differences in the elemental composition distribution range between them and previously tested bronze mirrors. This paper significantly reveals that the lead mineral source of Hunan bronze mirrors underwent two obvious changes during the late Bronze Age. The Warring States bronze mirrors excavated in Hunan mainly used lead ore from the Nanling region and Northern Hunan region, and Changsha should be the center of mirror-production and mirror-circulation in Southern Chu Kingdom. However, the lead ore consumed by the Western Han bronze mirrors excavated in Hunan primarily came from the East Qinling region, which was close to the core region under the rule of the Western Han government. In the middle and late Eastern Han Dynasty, with the frequent metal production activities in the Nanling region and the prosperity of private mirror-casting industry in Southern China, lead ore from the Nanling region was re-introduced in the production of Hunan bronze mirrors.

S, Pb, and Fe isotope compositions of sulfides in middle and southern Okinawa Trough: Implying the complicated hydrothermal systems in back-arc spreading centers

Sulfur, lead, and iron isotopic systematics of sulfides from the Iheya North hydrothermal field in middle Okinawa Trough and the Yonaguni Knoll IV hydrothermal field in southern Okinawa Trough were investigated to understand the origin of ore-forming material and isotope fractionation during sulfide precipitation in back-arc spreading centers. The δ34S values (from 8.60‰ to 9.68‰) of sulfide minerals in Iheya North field suggest sulfur was derived from the leaching of basement rocks and the reduction of seawater sulfate. But an additional light sulfur source from the dissolution of biogenic sulfides in sediments is indispensable for the observed low δ34S values (between 4.78‰ and 4.97‰) of Yonaguni Knoll IV sulfides. Lead isotope compositions of all sulfides vary in a relatively wide range (206Pb/204Pb = 18.432 to 18.563, 207Pb/204Pb = 15.579 to 15.671, and 208Pb/204Pb = 38.539 to 38.979, respectively) which involves the mixing of mantle-derived and sediment-derived lead in varying proportions. Unusually high radiogenic lead isotope ratios of Yonaguni Knoll IV sulfides (207Pb/204Pb = 15.628 to 15.671, and 208Pb/204Pb = 38.854 to 38.979) imply the presence of old crustal fragments beneath southern OT. The hydrothermal fluids in OT are characterized by extremely low calculated δ56Fe values (−1.00‰ to −1.32‰) which is attributed to reducing sediments. The paired Fe-isotope compositions of pyrite and chalcopyrite revealed significantly different iron isotope compositions of hydrothermal fluids in study areas and extremely complicated ore-forming processes. Rapid precipitation of pyrite from FeS precursors accompanying iron isotopic disequilibrium moves from FeS-fluid equilibrium to pyrite-fluid equilibrium during pyrite recrystallization. The combination of sulfur, lead, and iron isotopic data suggests that hydrothermal systems in back-arc spreading centers related to plate subduction are generally affected by mantle, overlying sediments as well as potential old continental crust fragments, which results in various hydrothermal fluids and complicated mineralization processes.

Resolving the complex mixing history of ancient Chinese bronzes by Manifold Learning and a Bayesian Mixing Model

Provenance of metals is a major theme in Bronze Age archaeology since it can help to reveal complex cultural and economic entanglements in ancient times. However, where complex societies with diversified trading relationships are concerned, identifying metal provenance has often proved to be challenging due to the frequent mixing of metals from different sources in antiquity. This research addresses this question by developing an innovative method for interpreting lead isotope data of bronze artefacts. Manifold learning and a Bayesian mixing model are combined to reconstruct quantitatively the contribution of metal sources to ancient bronzes. The methodology is employed to resolve the complex metal circulation system in the Zhou period (11th-3rd century BC) of China, and reveals a significant diachronic change of metal resources from North, Central, and South China. The North China metal sources were mainly employed in the Early Western Zhou period (1046–950 BC). In the following ages, the Yangtze River Valley and Qinling Mountains became the major metal sources for Zhou people. The Middle Spring and Autumn period (660 BC-560 BC) witnessed a major shift of dependence between these two sources, demonstrating a fundamental transformation in the metal circulation system. The South China metal sources were exploited throughout the entire Zhou period and probably associated with polymetallic deposits in the Nanling area. This research reveals the long-term patterns of metal exploration and mixing in the Zhou period of China, and also demonstrates the great potential this new methodology promises in addressing the complex metal mixing history in other cultural contexts.

Zinc on the edge—isotopic and geophysical evidence that cratonic edges control world-class shale-hosted zinc-lead deposits

The North Australian Zinc Belt is the largest zinc-lead province in the world, containing three of the ten largest known individual deposits (HYC, Hilton-George Fisher, and Mount Isa). The Northern Cordillera in North America is the second largest zinc-lead province, containing a further two of the world’s top ten deposits (Red Dog and Howards Pass). Despite this world-class endowment, exploration in both mineral provinces during the past 2 decades has not been particularly successful, yielding only two significant discoveries (Teena, Australia, and Boundary, Canada). One of the most important aspects of exploration is to choose mineral provinces and districts within geological belts that have the greatest potential for discovery. Here, we present results from these two zinc belts that highlight previously unused datasets for area selection and targeting. Lead isotope mapping using analyses of mineralized material has identified gradients in μ (238U/204Pb) that coincide closely with many major deposits. Locations of these deposits also coincide with a gradient in the depth of the lithosphere-asthenosphere boundary determined from calibrated surface wave tomography models converted to temperature. Furthermore, gradients in upward-continued gravity anomalies and a step in Moho depth correspond to a pre-existing major crustal boundary in both zinc belts. A spatial association of deposits with a linear mid- to lower-crustal resistivity anomaly from magnetotelluric data is also observed in the North Australian Zinc Belt. The change from thicker to thinner lithosphere is interpreted to localize prospective basins for zinc-lead mineralization and to control the gradient in lead isotope and geophysical data. These data, when combined with data indicative of paleoenvironment and changes in plate motion at the time of mineralization, provide new exploration criteria that can be used to identify prospective mineralized basins and define the most favorable parts of these basins.

Lead in the Levant during the Late Bronze and early Iron Ages

Probably due to its relative scarcity in the archaeological record of the Late Bronze and early Iron Ages, lead is seldom the focus of archaeometallurgical research on these periods. In the current study we turn to legacy lead isotope data in order to provenance lead artifacts from Eastern Mediterranean contexts, dated to the second half of the 2nd millennium BCE. These data shed new light on the circulation of lead in the Eastern Mediterranean prior, during and after the collapse of the Bronze Age global trade systems. We provide further support to the notion that lead from Sardinia was circulating in Eastern Mediterranean markets and reached the Levant already during the Late Bronze Age. We found that this trade was more common in the South-eastern Mediterranean (in comparison to the North-eastern Mediterranean), probably as the result of geopolitical circumstances related to the distinct spheres of influence of Egypt and Hatti at that time. Moreover, it seems that lead from Sardinia was continuously shipped towards the east also in the face of the changing geo-economical dynamics during the transition between the Bronze and Iron Ages. The data were obtained mostly through the OXALID database. The current paper also aims at emphasizing the importance of shared open access databases for lead isotopes in archaeometallurgical research.

Can Isotopes Be Used as Lead Tracers in Shooting-Range Soils?

Lead isotopes have been widely used to assess the sources of Pb in the soil environment since lead isotopes ratios have a specific signature that allows us to use them as environmental tracers. However, some lead sources are difficult to be identified. This article contains the lead isotope data from soils and shot pellets collected in an abandoned shooting range (NW Spain). Twelve soil and three-shot pellet samples were randomly collected and analyzed using MC-ICP-MS. The isotope ratios are shown, and analyses proved that Pb originated predominantly from the used shot pellets. Contaminated soils exhibited an isotopic composition (206Pb/207Pb, 208Pb/204Pb, 206Pb/204Pb and 208Pb/206Pb) close to some shot pellets from different manufacturers. These results offer new, valuable data for other researchers working on lead contamination research and the identification sources of Pb for adjacent areas to shooting-range facilities and for wildlife ecotoxicology. Still, the use of several ammunitions derived from different sources, such as recycled Pb, showed that it is hard to identify the lead source and these kinds of facilities.

Chlorite chemistry, H-O-S-Pb isotopes and fluid characteristics of the Yuhai Cu-Mo Deposit in Eastern Tianshan: Implications for porphyry copper mineralization and exploration

The Yuhai porphyry Cu-Mo deposit, located in the Eastern Tianshan metallogenic belt, northwest China, is a new discovery in the eastern section of Dananhu-Tousuquan arc, hosted mainly by quartz diorite and granodiorite intrusions. Based on alteration and mineralization assemblages as well as crosscutting relationships, three stages of hydrothermal activities have been identified: 1) early mineralization stage characterized by potassic alteration and minor Cu-Mo mineralization; 2) main mineralization stage with phyllic and propylitic alterations and extensive Cu-Mo precipitation; and 3) late mineralization stage forming barren quartz and minor calcite, chlorite, and epidote minerals. Sulfur isotope compositions of the Yuhai chalcopyrite, pyrite, bornite and molybdenite record a narrow range of −3.4 to +0.4 ‰, indicating a deep source of magmatic sulfur. Lead isotope data of sulfides from our previous study display consistent 208Pb/204Pb and 207Pb/204Pb ratios, but distinguishable 206Pb/204Pb ratios from the Yuhai intrusions analysed in this work. Combined sulfur and lead isotopic signatures, we suggest that the ore-forming components (metals and sulfur) were derived from a mantle-derived magmatic reservoir with some crustal components. The δ18O values of quartz, chlorite, calcite, and sericite samples separated from different mineralization stages range from 1.5 to 8.2 ‰ (n = 11), with calculated δ18OH2O values of −2.2 to 4.5 ‰, and the δD values of fluids range from −92.7 to −68.7 ‰ (n = 4), indicating the ore-forming fluids are composed of magmatic fluid and meteoric water. Mineral chemistry of chlorite, fluid inclusions microthermometry, and petrographic evidences reveal that the ore-forming fluids evolved from a high fO2 to relative weak oxidized condition with decreasing temperature, and copper was largely precipitated at temperatures of <320 °C in a weakly oxidized system during main stage. All these observations demonstrate that Yuhai was formed by hydrothermal fluids related to the diorite magma, and that the fO2 and temperature decreasing plays a critical role for abundant depositions of Cu and Mo. The Paleozoic diorite complex formed in a subduction setting is suggested as a significant exploration target for porphyry-style Cu mineralization in the Eastern Tianshan.

Improvement and integration: scientific analyses of willow-leaf shaped bronze swords excavated from the Shuangyuan Village Cemetery, Chengdu, China

Willow-leaf shaped sword is a kind of exclusive bronze weapon popular only in the states of Ba and Shu during the Eastern Zhou Dynasty (770-256 BC). Its prototype may originate from Central Asia and India and is a typical example of a trans-regional and cross-cultural artifact. Here, we present a scientific study of willow-leaf shaped swords of Shu State from the Shuangyuan Village Cemetery, Chengdu, by pXRF and MC-ICP-MS, and attempted to argue for the improvement and integration of weapon production in Shu by characterizing its elemental composition and lead isotopic signature. The results show that there is a significant difference in the tin content and lead material source between the Ba and Shu bronze swords. This feature can be applied as an important indicator to distinguish willow-leaf shaped swords from Ba and Shu, especially when the appearances are almost confused. The alloy formula of the Shu bronze sword was influenced by the bronze-making technology of Chu and other states. Combining the published lead isotope data of the willow-shaped bronze swords, it can be inferred that Shu State has produced bronze weapons with considerable frequency and in many batches, which was a major motivation for triggering faster progress in its craft.

Tracking the source of lead of medieval glazed pottery of the Meuse valley (Belgium) through lead isotope analyses

Lead isotope analyses (by MC-ICP-MS) have been performed on lead-glazed pottery artefacts from several production and consumption sites in the Meuse basin (Belgium) spanning a long-time period from the 9th to the 16th century CE. Comparison of the lead isotope data of the glazes from three Mosan workshops with those of galenas from Palaeozoic (Variscan) Pb-Zn deposits from both Belgium and Western Germany points to a common Pb source that we identify as the regional Pb deposits hosted in Dinantian limestones of the Ardenno-Rhenish Massif, more specifically in the Namur and Verviers synclines in Belgium and in the Aachen-Stolberg mining district in Germany. The overall similarity of isotopic compositions between the medieval artefacts and the Variscan galenas implies that the Mosan medieval potters used accessible local Pb-Zn ores mined between Namur and Huy. On the consumption sites of Dinant, the slightly different isotopic compositions of some potteries suggest that other regional Pb sources were used to produce the glazes. A comparison with Roman lead objects discovered in north-western Europe (Northern Gaul) shows the very good correspondence of the Pb isotopic compositions with those of the Medieval artefacts which indicates a very long continuity of regional lead supply and consequently of lead ore mining.

Copper-base metal supply during the northern Vietnamese Bronze and Iron Ages: metallographic, elemental, and lead isotope data from Dai Trach, Thành Dên, Gò Mun, and Xuân Lâp

We present the results of metallographic, elemental, and lead isotope analyses of one slag and 27 copper-base artefacts from northern Vietnam. These artefacts come from four sites: Dai Trach, Thành Dên, Gò Mun, Xuân Lâp and are attributed to the Đồng Đậu (ca. 1300–1000 BC), Gò Mun (ca. 1000–700 BC), and Đông Sơn (ca. 700 BC–100 AD) cultures, the two former being Bronze Age (18 samples) and the latter Iron Age (10 samples). Twenty-two of the samples have as-cast microstructures, with one having been quenched, three evidencing working and annealing, and one too corroded to tell. Despite variable corrosion levels, all metal samples are identified as bronzes, rather than copper, though seven are leaded bronzes. All the leaded alloys are Iron Age, which is typical for the region. Lead isotope results were notable, in that none of the study samples is consistent with the known prehistoric Southeast Asian copper production signatures, an unusual occurrence in recent regional provenance research. There is some compatibility with Thai Bronze Age copper-base artefacts, but generally it seems there was only weak overlap in exchange systems between northern Vietnam and southern Mainland Southeast Asia, with northern Laos as a possible frontier zone. Further archaeometallurgical prospection and characterisation in northern Vietnam are needed to identify primary production loci, but sources in the southern Chinese provinces of Yunnan, Guangxi, and Guangdong are also probable.