Lead Isotope Analysis Research Articles

The genesis of gold mineralisation hosted by orogenic belts: A lead isotope investigation of Irish gold deposits

Lead isotope analyses have been performed on 109 gold and 23 sulphide samples from 34 Irish gold occurrences, including 27 placers, and used to shed light on the sources of mineralising fluids and metals associated with gold mineralisation hosted by orogenic belts. The Pb isotope ratios of lode and placer gold range from 206Pb/204Pb=17.287–18.679, 207Pb/204Pb=15.382–15.661, and 208Pb/204Pb=37.517–38.635, consistent with the Pb isotopic data on previously reported Irish sulphide mineralisation. There is no evidence that gold mineralisation is associated with distinctive source regions, and it appears to have been derived from similar sources to those responsible for the widespread sulphide mineralisation in Ireland. It is inferred that the principal controls on the Au mineralisation are structural and not related to the distribution of Au in their source rocks. The range of Pb isotope ratios favours the interaction of multiple source reservoirs predominantly during the Caledonian Orogeny (c. 475–380Ma). Underlying basement was the primary control on two key sources of Pb. Gold occurrences located to the south-east of the Iapetus Suture are characterised by Pb compositions that derive predominantly from the Late Proterozoic crustal basement or overlying Lower Palaeozoic sediments, whilst those located north-west of the Iapetus Suture are characterised by less radiogenic Pb signatures derived predominantly from Late Proterozoic or older crustal basement. A third source, relatively enriched in radiogenic Pb, also played a role in the formation of a number of Irish gold occurrences, and may have been associated with syn- to post-orogenic intrusives. Magmatic processes may therefore have played an important role in the formation of some orogenic gold occurrences.

Metallurgical characterization of brass objects from the Akko 1 shipwreck, Israel

The Akko 1 shipwreck was a small Egyptian armed vessel or auxiliary naval brig built in the eastern Mediterranean at the beginning of the 19th century. During the underwater excavations, about 230 brass hook-and-eye closures were found, mainly in the bow area. In addition, 158 brass cases were found, mainly between midships and the aft extremity of the shipwreck. Metallurgical non-destructive and destructive characterizations of selected items were performed, including radiographic testing, XRF, lead isotope analysis, optical microscopy, SEM–EDS and microhardness tests. The hook-and-eye closures and the cases were both found to be made of binary copper–zinc alloy (about 30wt.% zinc). While the brass cases were made from rolled sheets, hand-made using simple tools, and joined by tin–lead soldering material, the brass hook-and-eye closures were hand-made from drawn brass wire, and manufactured from commercial drawn brass bars by a cold-working process. The lead isotope analyses suggest different provenances of the raw materials used for making the brass objects, thus the different origins of the ores may hint that the brass wire and sheet were imported to the workshops in which the objects were manufactured.

Variations in lead isotopic abundances in Sprague-Dawley rat tissues: possible reason of formation.

It has been reported in previous research that the lead isotopic composition of blood, urine and feces samples statistically differed from the given lead sources in Sprague-Dawley (SD) rats. However, the reason for this phenomenon is still unclear. An animal experiment was performed to investigate the lead isotope fractionation in diverse biological samples (i.e., lungs, liver, kidneys, bone) and to explore the possible reasons. SD rats were intratracheally instilled with lead acetate at the concentrations of 0, 0.02, 0.2, and 2 mg/kg body weight. Biological samples were collected for lead isotope analysis using an inductively coupled plasma mass spectrometry (ICP-MS). Significant differences are observed in lead isotope abundances among the diverse biological samples. The lead isotope abundances (206Pb, 207Pb and 208Pb) in diverse biological samples show different degrees and directions of departure from the given lead source. The results suggest that differences in enrichment or depletion capacity for each lead isotope in the various tissues might lead to the variation in lead isotopic abundances in tissues. Moreover, a nonlinear relationship between the blood lead level and the lead isotope abundances in liver and bone is observed. When the whole-blood level is higher than 50 ng/mL, the lead isotopic compositions of biological samples tend to be the same. Thus, the data support the speculation of a fractionation functional threshold.

New insights into Levantine copper trade: analysis of ingots from the Bronze and Iron Ages in Israel

The close association of metal ingots to the smelting operation and hence to the ore deposit makes them good candidates for provenance studies which in turn can be used for reconstructing paths of metal trade. A unique group of ingots from Hazor, Israel and two ingot groups retrieved during underwater explorations off the Carmel coast (Israel) were subjected to microstructure, chemical and lead isotope analysis. Ingots from Timna, Bir Nasib and Deir Alla, previously studied, were also subjected to bulk chemical and lead isotope analysis (LIA). The results enabled us to follow changes in the supply of copper to sites of this part of the Levant between two main copper producers: Cyprus and the Arabah (Timna and Faynan). The analyses showed that two of the ingot assemblages correspond to two different phases of Cypriot copper exportation in the second millennium BCE. The earlier phase, identified here for the first time, dated to the Middle Bronze Age II – Late Bronze Age I, consisted of trade in black copper in the form of relatively small plano-convex ingots, as suggested by the evidence from Hazor. The later phase, dated to the Late Bronze Age II, during which Cypriot copper was traded in the form of large oxhide–shaped ingots, is well-known and is evidenced by oxhide ingots recovered off the Carmel coast. A third assemblage from Neve Yam, off the same coast, consisting of 54 ingots of similar shape and composition, is identified here as the hitherto unknown product of the large-scale operations at Faynan in the Iron Age.

Lead provenance study in medieval metallic materials from Madinat al-Zahra (Medina Azahara, Córdoba)

The objective of this study is to provide insight into the origin of the lead present in the 10th-century. AD Islamic city of Madinat al-Zahra, both as unalloyed metal and as a component of the copper-based alloys, as well as a first approach to technological details related to the production of these materials. Recycling lead is argued to be a common practice but, nonetheless, the lead isotope analysis suggests a single origin for all the lead at the site. Two main options are discussed as lead sources: mines in the Linares district (100 km east) or in Villanueva del Duque (75 km north). Other interesting features are the use of lead-tin solder and fire gilding on a copper–zinc alloy.

Determination of lead isotope ratios in environmental matrices by quadrupole ICP-MS working at low sample consumption rates

Measurement of lead isotope ratios in environmental matrices using inductively coupled plasma-dynamic reaction cell-mass spectrometry at low sample consumption rates was investigated. Two micro-sample introduction systems were evaluated, namely the PFA micronebuliser associated with a low-volume spray chamber, working at 150 μL min−1 and the total-consumption sample introduction system TISIS, operating at 20 μL min−1. In both cases, the dynamic reaction cell pressurised with ammonia was applied to improve the precision by collisional damping. Under optimal operating conditions, 208Pb/207Pb and 206Pb/207Pb ratios were accurately determined with an internal precision of 0.12–0.13% and 0.17–0.18% (%RSD, n = 10, c = 10 μg L−1; t = 10 s). The sample consumption for the assessed sample introduction systems was less than 1.5 mL and 200 μL, allowing the precise analysis of limited-size samples and pre-concentrates. The developed method was characterised in terms of the analytical working range, in-cell interference, and uncertainty estimation. The applicability of the analytical method was demonstrated by the analysis of the lichen reference material CRM 482, as well as those of several environmental samples collected from polar regions, including atmospheric particulate, snow, marine suspended particulate matter and sediment. In particular, by combining a simple pre-concentration procedure with the application of TISIS, it was possible to perform the lead isotope analysis of Antarctic snow samples at the pg g−1 concentration level.

Lead isotope analysis of melt inclusions by LA-MC-ICP-MS

This study provides a method for measuring Pb isotopes of olivine-hosted melt inclusions with diameters larger than 40 micrometers.

King Solomon's Silver

Archaeology![Figure][1] CREDIT: WWW.BIBLELANDPICTURES.COM/ALAMY Isotope analysis of archaeological materials can play critical roles in both dating of the artifacts and identification of their origin. Thompson and Skaggs use the lead isotope ratios in silver from silver hoards to investigate trade patterns during a Mediterranean “Dark Age” between 1200 and 800 BCE precipitated by the collapse of palace-based economies in the Near East. Lead isotope analysis of 48 precoinage silver artifacts from what was southern Phoenicia [the region between the Yarkon River and Akko (Acre) in present-day Israel] and dated from 1200 to 800 BCE shows that they have isotope ratios similar to those of galena (the mineral form of lead sulfide) and other lead ores from southern and southwestern Sardinia, and the Iberian Peninsula. These analyses tentatively identify regions in the western Mediterranean as contributing mineral resources to Phoenician precolonial silver trade and production. The results correlate with ancient documentary sources indicating Phoenician precolonial silver trade with Sardinia and Spain and suggest that the Phoenician precolonial expansion into the west may have involved the acquisition of silver. Thompson and Skaggs further support suggestions that the legendary Tarshish region, a possible source of King Solomon's silver, may have been a refinery town, possibly Nora, on Sardinia. Internet Archaeol. 35 , 10.11141/ia.35.6 (2013). [1]: pending:yes

Croig Cave: a Late Bronze Age ornament deposit and three millennia of fishing and foraging on the north-west coast of Mull, Scotland

Activity within caves provides an important element of the later prehistoric and historic settlement pattern of western Scotland. This contribution reports on a small-scale excavation within Croig Cave, on the coast of north-west Mull, that exposed a 1.95 m sequence of midden deposits and cave floors that date between c 1700 BC and AD 1400. Midden analysis indicated the processing of a diverse range of small fish and the collection of shellfish throughout this period, showing a high degree of continuity involving low-risk inshore fishing. At c 950 BC, a penannular copper bracelet and an amber bead were deposited within a small, shallow pit within the cave floor, suggestive of a discrete ritual episode within the cycle of otherwise potentially mundane activities. Lead isotope analysis indicated an Irish origin for the copper ore. A piece of iron slag within later midden deposits, dated to c 400 BC, along with high frequencies of wood charcoal, suggest that smithing or smelting may have occurred within the cave. High zinc levels in the historic levels of the midden c AD 1200 might indicate intensive processing of seaweed.

A 6000-year geochemical record of human activities from Alexandria (Egypt)

Recent multidisciplinary investigations of sediment cores from the ancient marine bay of Alexandria (Egypt) have documented local human activities during the Iron Age (circa 900–1000 B.C.) prior to Alexander the Great's arrival in 331 B.C. (Goiran, 2001; Véron et al., 2006; Stanley et al., 2007, 2010), corroborating the existence of the so-called “Rakhotis” as evoked in previous archaeological literature (Jondet, 1916; Weill, 1919; Chauveau, 1999; Baines, 2003). Lead (Pb) Isotopic Analyses (LIA) from Alexandria Bay indicate a possible anthropogenic imprint as early as circa 2300–2650 (±200) B.C. and, to a lesser extent, 3500–3800 (±170) B.C. (Véron et al., 2006). Here we demonstrate that LIA in sediments from the nearby Maryut Lagoon display isotopic anomalies resulting from the release of contaminant Pb into the Lagoon during the Egyptian Early dynastic (at 2897 ± 187 B.C) and Predynastic (at 3520 ± 145 B.C.) periods that corroborate geochemical data from Alexandria Bay. Pb concentrations in Maryut sediments show enrichments that mirror isotopic findings. The absence of contaminant Pb imprints within the sediments from the nearby Nile Canopic branch confirms that isotopic anomalies found in Alexandria Bay and Maryut Lagoon sediments are local and do not originate from long-distance transport of contaminant Pb associated with Nile suspended material and/or wind-derived aerosols. LIA in Alexandria sediment cores correspond to commonly mined Pb and Cu (copper) ores from Turkey (Black Sea region), Cyprus, Crete and the Oman Gulf. LIA substantiate the use of copper-based relics in the Alexandria region during the Pre and Early dynastic periods, and provide insights into metal trading within the Eastern Mediterranean during the Chalcolithic–Early Bronze Age transition, 6000 years ago.

Moving metals II: provenancing Scandinavian Bronze Age artefacts by lead isotope and elemental analyses

The first part of this research published previously proved without doubt that the metals dated to the Nordic Bronze Age found in Sweden were not smelted from the local copper ores. In this second part we present a detailed interpretation of these analytical data with the aim to identify the ore sources from which these metals originated. The interpretation of lead isotope and chemical data of 71 Swedish Bronze Age metals is based on the direct comparisons between the lead isotope data and geochemistry of ore deposits that are known to have produced copper in the Bronze Age. The presented interpretations of chemical and lead isotope analyses of Swedish metals dated to the Nordic Bronze Age are surprising and bring some information not known from previous work. Apart from a steady supply of copper from the Alpine ores in the North Tyrol, the main sources of copper seem to be ores from the Iberian Peninsula and Sardinia. Thus from the results presented here a new complex picture emerges of possible connectivities and flows in the Bronze Age between Scandinavia and Europe.

Tracing diffuse anthropogenic Pb sources in rural soils by means of Pb isotope analysis

Knowledge of the cause and source of Pb pollution is important to abate environmental Pb pollution by taking source-related actions. Lead isotope analysis is a potentially powerful tool to identify anthropogenic Pb and its sources in the environment. Spatial information on the variation of anthropogenic Pb content and anthropogenic Pb sources in rural topsoils is remarkably limited. This study presents results of a survey of approximately 350 topsoil samples from rural locations covering the entire Netherlands, for which the bulk geochemical and Pb isotope compositions were determined. The specific aim of this study is to determine the anthropogenic Pb sources in the topsoils from rural areas in The Netherlands. The spatial distribution of anthropogenic Pb in soils in The Netherlands will be explained in terms of land use and pollution sources.Nearly all studied topsoils display Pb contents that exceed the amount expected based on the soil lithology. The range in Pb isotope ratios of the additional Pb fraction in rural Dutch topsoils is established at 1.056–1.199, 2.336–2.486 and 0.452–0.490 for 206Pb/207Pb, 207Pb/208Pb and 206Pb/208Pb, respectively. Five land use types are distinguished (forest, open nature, moor, arable land and grassland) with distinct isotopic compositions for added Pb. Additional Pb in soils of natural areas (forest, open nature and moor) has on average lower 206Pb/207Pb, 208Pb/207Pb and 206Pb/208Pb ratios than the agricultural soils (arable land and grassland). Additional Pb in both natural area soils and agricultural soils is interpreted to be of anthropogenic origin: most likely a mixture of coal/galena, incinerator ashes and gasoline Pb. The dominant sources of additional Pb in the topsoil of open nature areas are most likely incinerator ash and gasoline Pb. In contrast, the on average higher 206Pb/207Pb, 208Pb/207Pb and 206Pb/208Pb ratios of additional Pb in agricultural soils are most likely caused by the presence of animal manure and N–P fertilizers.Several areas are observed with notably high additional Pb contents (26–211mg/kg on an organic matter-free basis) in the topsoil. The largest area is the Randstad area, which has the highest population and traffic density, and hosts a considerable fraction of the Dutch chemical industry. Two other areas with high additional Pb contents in the topsoil are located near the Dutch borders and are most likely influenced by German and Belgian chemical industries. The topsoils in the coastal dunes and southern, central and northern forests are characterized by relatively low additional Pb contents (<10mg/kg on an organic matter-free basis). The population, traffic and chemical industry density is low in these areas and no fertilizers are applied.

An alternative suggestion for the Pliocene onset of major northern hemisphere glaciation based on the geochemical provenance of North Atlantic Ocean ice-rafted debris

The onset of abundant ice-rafted debris (IRD) deposition in the Nordic Seas and subpolar North Atlantic Ocean 2.72 millions of years ago (Ma) is thought to record the Pliocene onset of major northern hemisphere glaciation (NHG) due to a synchronous advance of North American Laurentide, Scandinavian and Greenland ice-sheets to their marine calving margins during marine isotope stage (MIS) G6. Numerous marine and terrestrial records from the Nordic Seas region indicate that extensive ice sheets on Greenland and Scandinavia increased IRD inputs to these seas from 2.72 Ma. The timing of ice-sheet expansion on North America as tracked by IRD deposition in the subpolar North Atlantic Ocean, however, is less clear because both Europe and North America are potential sources for icebergs in this region. Moreover, cosmogenic-dating of terrestrial tills on North America indicate that the Laurentide Ice Sheet did not extend to ∼39°N until 2.4 ± 0.14 Ma, at least 180 ka after the onset of major IRD deposition at 2.72 Ma. To address this problem, we present the first detailed analysis of the geochemical provenance of individual sand-sized IRD deposited in the subpolar North Atlantic Ocean between MIS G6 and 100 (∼2.72–2.52 Ma). IRD provenance is assessed using laser ablation lead (Pb) isotope analyses of single ice-rafted (>150 μm) feldspar grains. To track when an ice-rafting setting consistent with major NHG first occurred in the North Atlantic Ocean during the Pliocene intensification of NHG (iNHG), we investigate when the Pb-isotope composition (206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb) of feldspars deposited at DSDP Site 611 first resembles that determined for IRD deposited at this site during MIS 100 (2.52 Ma), the oldest glacial for which there exists convincing evidence for widespread glaciation of North America. Whilst Quaternary-magnitude IRD fluxes exist at Site 611 during glacials from 2.72 Ma, we find that the provenance of this IRD is not constant. Instead, we find that the Pb-isotope composition of IRD at our study site is not consistent with major NHG until MIS G2 (2.64 Ma). We hypothesise that IRD deposition in the North Atlantic Ocean prior to MIS G2 was dominated by iceberg calving from Greenland and Scandinavia. We further suggest that the grounding line of continental ice on Northeast America may not have extended onto the continental shelf and calved significant numbers of icebergs to the North Atlantic Ocean during glacials until 2.64 Ma.

Copper quality and provenance in Middle Bronze Age I Byblos and Tell Arqa (Lebanon)

Forty-four Middle Bronze Age I weapons discovered at the sites of Byblos and Tell Arqa in Lebanon were investigated in order to study their copper quality and provenance. The evaluation of copper qualities is based on quantifying permanent inclusions such as copper sulfide and lead globules. The provenance of copper was studied using lead isotope analyses. For further discrimination between copper groups and sources elemental analyses by PIXE were performed on some of the weapons investigated. The results revealed two copper groups that could be qualified as “dirty” copper and “clean” copper. The former was used in most of the weapon types whereas the latter was reserved for items made of high-tin bronzes (>11 wt%) which underwent heavy hammering during the manufacturing process. Even though several potential copper sources were identified, the data point to Iran and Oman as the most probable areas of origin for the metal used in these weapons. These results contribute to the study of inter-regional exchange networks in the ancient Near East.

Isotopic Composition of Lead in Copper Ores and a Copper Artefact from the La Profunda Mine (León, Spain)

This paper continues the characterization of the lead isotopic fingerprint of ancient copper mines in the north‐west of Spain. In this work, the lead isotopic compositions found in copper ores from the La Profunda mine are presented. Azurites and malachites sampled from this deposit were subjected to lead isotope analysis by multicollector ICP–MS. The results showed a clear radiogenic lead signature compatible with the presence of uranium‐rich minerals (such as zeunerite) in the same mining complex. Moreover, a rare copper artefact, found in the galleries of the mine during its modern exploitation, was also analysed and showed that local mineral was used for its manufacturing.

Cenozoic high-K alkaline magmatism and associated Cu–Mo–Au mineralization in the Jinping–Fan Si Pan region, southeastern Ailao Shan–Red River shear zone, southwestern China–northwestern Vietnam

The Jinping–Fan Si Pan (JFP) Cenozoic magmatic and Cu–Mo–Au metallogenic belt in the southeastern part of the Ailao Shan shear zone host the Tongchang, Chang′an, Habo, and Chinh Sang Cu–Mo–Au deposits. These deposits form an integrated epithermal-porphyry regional mineralization system associated with 40–32Ma high-K alkaline magmatism. The magmatic rocks in the belt have relatively low TiO2 (<0.73wt%), P2O5 (<0.29wt%), and FeO* (<4.99wt%), and high Na2O (2.86–4.75wt%) and K2O (4.01–7.98wt%). They also have high contents of incompatible trace elements, and are enriched in LILE (Rb, Ba, K, Sr) and LREE. They have marked Nb, Ta, Ti and P depletion in primitive mantle-normalized spidergrams, and plot close to the EMII mantle field in the Sr–Nd isotopic diagram. These characteristics are similar to those of the Eocene high-K alkaline rocks along the northern Ailao Shan belt, eastern Tibet plateau. The sulfur and lead isotope analyses of sulfide minerals from both the ores and related magmatic rocks confirm the involvement of a magmatic ore fluid. The Cenozoic alkaline intrusions and Cu–Mo–Au mineralization in the JFP were formed prior to the initiation of left-lateral shearing along the Ailao Shan shear zone. The magmas appear to have been derived from enriched mantle, possibly with mixing of materials from the buried Tethyan oceanic lithosphere, and/or crust.

Coupling lead isotope analysis and petrography to characterize fabrics of storage and trade containers from Hala Sultan Tekke (Cyprus)*

Lead isotopes, thin‐ and sherd‐section analyses are coupled on pottery‐vessel fragments excavated from the Late Bronze Age site of Hala Sultan Tekke (south‐east Cyprus) and representing fabrics used for the production of storage and trade containers. The fabrics of the sherds are first described according to general macroscopic observations. Based on the different fabrics identified, a petrographic analysis is carried out on thin sections and compared to lead isotope results on the same samples. This study shows that a specific fabric corresponds to a specific lead isotopic composition and proposes different sources for the various groups of associated sherds/fabrics. It also demonstrates the compatibility and complementarity of petrography and lead isotopes within pottery provenance study.

Copper, lead, and silver isotopes solve a major economic conundrum of Tudor and early Stuart Europe

The unrelenting economic inflation of A.D. 1515–1650 in Europe has been variously explained by the influx of silver from Mexico and the Viceroyalty of Peru (now Bolivia), the growth of the European population, and the decline of the silver market price. Silver, copper, and lead isotope analyses of A.D. 1550–1650 English coinage show a dominance of silver from Europe and Mexico, contrasting with a spectacularly small contribution from the Viceroyalty of Peru. This observation contrasts with the registration of metal production in the mines of the Spanish Americas. Hence the question: Where did Potosi silver go? This novel observation indicates that silver from Mexico was exported eastward, whereas Potosi silver flowed westward. However, aware of the Pacific route of the silver trade, scholars never agreed upon the volumes transported. Our work demonstrates that there was a Potosi-China route, and that it was largely disconnected from the Mexico-Europe routes.

Solution and laser ablationMC-ICP-MS lead isotope analysis of gold

A new approach is presented for the analysis of lead isotopes in gold using solution and laser ablation multi-collector inductively-coupled plasma mass-spectrometry (MC-ICP-MS). Repeat analyses of two gold reference materials (RAuGP3: 34.1 ± 0.5 ppm Pb and RAuGP5: 129 ± 4 ppm Pb, from SPEX CertiPrep Ltd) yield an external reproducibility of 20. Instrumental mass bias is corrected by standard sample bracketing, using NIST SRM981 for solution analyses and NIST SRM610 for laser ablation analyses. Both techniques agree within error, and they have been further demonstrated through the analyses of both geological and archaeological samples: multiple grains from two Irish alluvial gold deposits and samples of two Early Bronze Age Irish gold lunulae. The applicability of these techniques to studies concerning the sources and age of gold mineralisation, and the identification of gold sources exploited in antiquity, is highlighted.

The silver of the South Iberian El Argar Culture: A first look at production and distribution

More than 700 silver objects are known from the Middle Bronze Age El Argar culture, which contrasts significantly with the rest of Bronze Age Europe, where silver is mostly rare. This has traditionally been explained by the difficulties of extracting silver from complex ores by cupellation and the relative abundance of easily accessible occurrences of native silver and silver chlorides in the south of the Iberian peninsula. However, until now in the Iberian Bronze Age the use of native silver has only been inferred by the absence of evidence of cupellation. The results of trace element analysis of a series of silver objects from several Argaric settlements reveal for the first time positive evidence for the use of native silver. Lead isotope analyses show that hardly any of the objects were made of silver from known and characterised mining districts.