TRACING THE RESOURCES OF IRON WORKING AT ANCIENT SAGALASSOS (SOUTH‐WEST TURKEY): A COMBINED LEAD AND STRONTIUM ISOTOPE STUDY ON IRON ARTEFACTS AND ORES*

Lead and strontium isotope analyses were performed by thermal ionization mass spectrometry (TIMS) on Roman to Byzantine iron artefacts and iron ores from the territory of ancient Sagalassos (south‐west Turkey), to evaluate Pb and Sr isotopes for provenance determination of ores for local iron production. It can be demonstrated that for early Roman artefacts and hematite iron ore processed in early Roman times from Sagalassos proper, as well as for magnetite placer sands and early Byzantine raw iron from the territory of the city, Sr isotopes are much less ambiguous than Pb isotopes in providing clearly coherent signatures for ore and related iron objects. Late Roman iron objects were produced from iron ores that as yet remain unidentified. Early Byzantine iron artefacts display more scatter in both their Pb and Sr isotope signatures, indicating that many different ore sources may have been used. Our study demonstrates that iron objects can be precisely analysed for their Sr isotopic composition, which, compared to Pb isotopes, appears to be a much more powerful tool for distinguishing between chronological groups and determining the provenance of raw materials.     

Andean Ores,Bronze Artifacts,and Lead Isotopes: Constraints on Metal Sources in Their Geological Context

With a focus on bronze production in the south-central Andes during the Middle Horizon, this study reports the first archaeological use of lead isotope analysis to investigate metallic ores and metal artifacts in the Andean zone of South America. Because the vast majority of metal deposits in the Andean cordillera formed in a convergent plate boundary setting, lead isotope compositions of most Andean ore sources are not unique. Lead isotope ratios of central and south-central Andean ores define four geographically distinct ore lead isotope provinces, oriented and elongated parallel or sub-parallel to the trend of the Andean cordilleras. Consequently, ore lead isotope ratios vary strongly from west to east along transects through the coast, highlands, and altiplano, but they exhibit much less variation from north to south. The strong west-to-east variation in ore lead isotope signatures allows discrimination between ore bodies, and ultimately between metal artifacts, as a function of macro-ecozone location: coast, junga-qiswa, puna, and altiplano. We present the most up-to-date database of ore lead isotope signatures for the south-central Andes including those determined for ores we sampled over an approximate 250,000-km² region within Bolivia, northern Chile, and northwest Argentina. Lead isotope signatures of Cu-As-Ni bronze artifacts from Tiwanaku (altiplano capital) and San Pedro de Atacama (desert oasis entrepôt) establish that altiplano and high sierra ore bodies provided the metal for both assemblages. Conchopata (Wari) arsenic bronze artifacts exhibit lead isotope ratios compatible with the Julcani (Huancavelica) copper sulfarsenide deposit.     

THE TUNGSTEN AND TIN SIGNATURE OF IRON ORES FROM ELBA ISLAND (ITALY): A TOOL FOR PROVENANCE STUDIES OF IRON PRODUCTION IN THE MEDITERRANEAN REGION

The mineralogy, petrography and major‐ and trace‐element composition of iron ores from Elba Island (Tuscany, Italy), one of the most important iron sources in the Mediterranean area since the first millennium bc , revealed that hematite‐rich ores display prominent enrichments in W and Sn (up to 4950 μg g^?1 and 8400 μg g^?1, respectively). These two elements are hosted by tiny grains of W–Sn mineral phases (ferberite, scheelite and cassiterite) that are disseminated throughout the hematite matrix. A comparison with iron ores from many Italian and European localities (most of which were exploited in ancient times) suggests the uniqueness of the geochemical pattern of Elba Island hematite‐rich ores (i.e., high W and Sn, low Mo and low Cu, Pb and Zn). We suggest that this geochemical signature may represent a new provenance marker not only for discarded ore at smelting/smithing sites, but, possibly, also for metallurgical slag and smelted metal produced in the chaîne opératoire of the iron process.     

THE USE OF TRACE ELEMENT ANALYSIS OF ENTRAPPED SLAG INCLUSIONS TO ESTABLISH ORE – BAR IRON LINKS: EXAMPLES FROM TWO GALLO‐ROMAN IRON‐MAKING SITES IN FRANCE (LES MARTYS,MONTAGNE NOIRE,AND LES FERRYS,LOIRET)*

Knowledge of the iron trade in ancient times rests on determining the source of the objects recovered during archaeological excavations. Unfortunately, attributing the origin is not always possible using archaeological tools alone. Trace element data of the ore and the archaeological material (reduction and reheating slags, entrapped slag inclusions from the bloom, bar iron and iron blades) from two Gallo‐Roman iron‐making centres, Les Martys (Montagne Noire) and Les Ferrys (Loiret), were determined using ICP–AES/MS and LA–ICP–MS. The results highlight a continuity of composition that makes it possible to establish a link between the initial ore and the semi‐finished iron products.     

The potential of stable Cu isotopes for the identification of Bronze Age ore mineral sources from Cyprus and Faynan: results from Uluburun and Khirbat Hamra Ifdan

Copper isotope ratios differ between hypogene sulfidic, supergene sulfidic and oxidized ore sources. Traditional lead isotope signatures of ancient metals are specific to deposits, while Cu isotope signatures are specific to the types of ore minerals used for metal production in ancient times. Two methodological case studies are presented: First, the mining district of Faynan (Jordan) was investigated. Here, mainly oxidized copper ores occur in the deposits. The production of copper from Fayan’s ore sources is confirmed by the measurement of the Cu isotope signature of ingots from the Early Bronze Age metal workshop from Khirbat Hamra Ifdan. Based on our results illustrating differences in the Cu isotope composition between the ore mineralizations from Timna (Israel) and Faynan, it is now possible to determine these prehistoric mining districts from which copper artifacts originated by combining trace elements and Pb isotopes with Cu isotopes. The second case study presents data on Late Bronze Age copper production in Cyprus. Oxhide ingots from the shipwreck of Uluburun (Turkey) were tested for their lead isotope signatures and assigned to Cypriot deposits in the recent decades. The oxhide ingots from Uluburun show a Cu isotope signature which we also found for oxidized copper ores from Cyprus, while younger oxhide ingots as well as metallurgical slag from the Cypriot settlements Kition and Enkomi show a different signature which might be due to the use of sulfidic ore sources from a greater depth of deposits. We assert that there could be a chronological shift from oxidized to sulfidic ore sources for the copper production in Cyprus, requiring different technologies. Therefore, Cu isotopes can be used as a proxy to reconstruct mining and induced smelting activities in ancient times.     

Precipitation of lead–zinc ores in the Mississippi Valley‐type deposit at Trèves,Cévennes region of southern France

The Trèves zinc–lead deposit is one of several Mississippi Valley‐type (MVT) deposits in the Cévennes region of southern France. Fluid inclusion studies show that the ore was deposited at temperatures between approximately 80 and 150°C from a brine that derived its salinity mainly from the evaporation of seawater past halite saturation. Lead isotope studies suggest that the metals were extracted from local basement rocks. Sulfur isotope data and studies of organic matter indicate that the reduced sulfur in the ores was derived from the reduction of Mesozoic marine sulfate by thermochemical sulfate reduction or bacterially mediated processes at a different time or place from ore deposition. The large range of δ³⁴S values determined for the minerals in the deposit (12.2–19.2‰ for barite, 3.8–13.8‰ for sphalerite and galena, and 8.7 to ?21.2‰ for pyrite), are best explained by the mixing of fluids containing different sources of sulfur. Geochemical reaction path calculations, based on quantitative fluid inclusion data and constrained by field observations, were used to evaluate possible precipitation mechanisms. The most important precipitation mechanism was probably the mixing of fluids containing different metal and reduced sulfur contents. Cooling, dilution, and changes in pH of the ore fluid probably played a minor role in the precipitation of ores. The optimum results that produced the most metal sulfide deposition with the least amount of fluid was the mixing of a fluid containing low amounts of reduced sulfur with a sulfur‐rich, metal poor fluid. In this scenario, large amounts of sphalerite and galena are precipitated, together with smaller quantities of pyrite precipitated and dolomite dissolved. The relative amounts of metal precipitated and dolomite dissolved in this scenario agree with field observations that show only minor dolomite dissolution during ore deposition. The modeling results demonstrate the important control of the reduced sulfur concentration on the Zn and Pb transport capacity of the ore fluid and the volumes of fluid required to form the deposit. The studies of the Trèves ores provide insights into the ore‐forming processes of a typical MVT deposit in the Cévennes region. However, the extent to which these processes can be extrapolated to other MVT deposits in the Cévennes region is problematic. Nevertheless, the evidence for the extensive migration of fluids in the basement and sedimentary cover rocks in the Cévennes region suggests that the ore forming processes for the Trèves deposit must be considered equally viable possibilities for the numerous fault‐controlled and mineralogically similar MVT deposits in the Cévennes region.     

Characterisation of the raw metal sources used for the production of copper and copper-based objects with copper isotopes

Copper isotopes can be successfully used to determine the origin of copper or bronze artefacts from either primary or supergene sulphide or hydrocarbonate ores. In conjunction with lead isotopes, they provide information on the origin and type of the metal ore. We demonstrate this in this paper from the combination of literature and own data on metal ores and artefacts (coins and ingots). Low-temperature hydrocarbonates (esp. malachite and azurite) do not fractionate the copper isotopes amongst each other and have identical lead isotopes. Substantial fractionation of copper isotopes, however, occurs between copper sulphides and hydrocarbonates (malachite, azurite) such that the ⁶⁵Cu isotope is always enriched in the oxidised relative to the sulphide phase with a clear distinction between the two ore types. Expressed in the δ⁶⁵Cu notation, we assigned supergene sulphides to values less than −0.4‰ down to negative values of −2‰ and more, primary sulphides to a range between −0.4 and +0.3‰ and hydrocarbonates to positive values higher than +0.3‰. We have applied these boundaries to copper coins and ingots from the time of the Roman emperors with known ages from Augustus up to 250 AD. The deposit fields of the metal used for the production of the coins were previously identified from the lead isotope ratios to lie in the Southwest and the Central South of Spain. From the combination of the lead and copper isotopes and the exact time constrains, we could develop a picture of the change in mining activities in Spain involving continued mining sulphide ore deposits and, indicated by positive δ⁶⁵Cu values as proxies for malachite and azurite, the opening of new mines in various time slots. This first application shows that copper isotopes will become the most important tool in archaeometallurgy to distinguish between the exploitation of deeper-seated primary and supergene sulphide ores and shallower, secondary hydrocarbonate ores. This will become especially relevant for archaeometric questions regarding the distinction between occasional and intentionally produced alloys.     

STATISTICAL EVALUATION OF THE PRESENTLY ACCUMULATED LEAD ISOTOPE DATA FROM ANATOLIA AND SURROUNDING REGIONS

Several hundred new stable lead isotope ratio determinations of ore and slag specimens from ancient mining sites throughout Anatolia and of samples of artefacts of the Chalcolithic, Bronze Age and Early Iron Age from museum collections in Turkey and the United States have been combined with the accumulated published isotope determinations of such specimens from throughout the eastern Mediterranean and Aegean regions to form a data base of nearly 1000 analyses. It is the purpose of this paper to evaluate the practical effectiveness of using this now extensive data base to discriminate between the many sources of metals throughout this region and to propose methods to enhance this discrimination. By using the full three-dimensional isotopic data in multivariate statistical treatments and by separating isotopically resolvable source groups within some of the source areas and isolating statistically outlying specimens from them, it has been possible to characterize some ore sources more precisely and compactly and thereby achieve better resolution between ore sources. It has also been possible to isolate isotopically compatible artefact groups which possibly relate to ore sources that, as yet, have not been well defined by isotopic analysis.     

REGIONAL VARIATIONS IN BLOOMERY SMELTING SLAG OF THE IRON AGE AND ROMANO‐BRITISH PERIODS*

This study highlights regional variation in the composition of iron‐smelting slag produced in England prior to the medieval period and attempts to link slag composition to the type of ore smelted. For many sites, the slag compositions were consistent with the use of limonite ore, but there is evidence that siderite ore was smelted at sites in Sussex in the late Iron Age/Romano‐British periods. A compositional comparison of smelting slags and slag inclusions in Iron Age currency bars, using data from Hedges and Salter (1979 ), illustrates the potential of smelting slag compositional data in provenance studies of early iron objects.     

The history of the United States cent revealed through copper isotope fractionation

Copper isotope fractionation in United States cents traces changes in the source of copper and identifies historical events. Application of copper isotopes as a geochemical tracer requires consistent isotopic signatures of the ores and refined metals. Overlapping isotopic signatures of crushed ores, chalcocite and refined metal extracted from Morenci, Arizona indicate modern mining processes that produce distinguishable single ore deposit geochemical signatures. The coincidence of copper isotope ratios in metals and ore deposits also exists within the United States cents analyzed here. Specifically, historical records confirm two different sources for copper in cents from 1800 through 1867. The copper isotope composition of the 1828, 1830, 1836, 1838 and 1843 cents coincides with the Cornwall ores of England, and cents post 1850 (1859, 1862) correspond with the Michigan ores of the United States. Three of the thirty-six post 1867 cents measured possess fractionated copper isotope ratios and indicate the change in source of copper for the United States cent.     

THE POSSIBLE FRACTIONATION OF LEAD ISOTOPES IN ANCIENT METALLURGICAL PROCESSES

The possibility of lead isotope fractionation in ancient lead production is examined. Kinetic theory relating to isotopic fractionation in non-equilibrium evaporation is considered and the feasibility of the alteration of lead isotope abundance ratios in ore roasting and smelting is assessed. Previous experimental work is shown to have been inconclusive and conclusions are drawn on the need for further research to quantify the possible extent of fractionation in practice.     

MINERALOGICAL AND PETROLOGICAL INVESTIGATIONS OF EARLY BRONZE AGE COPPER‐SMELTING REMAINS FROM THE KIECHLBERG (TYROL,AUSTRIA)

The prehistoric settlement on the Kiechlberg hilltop is located a few kilometres to the north‐east of Innsbruck, in the Tyrolean Inn Valley. Despite its rather isolated location, a multiphase settlement between the fifth and the second millennium bc was confirmed by archaeological investigations in 2007 and 2008. Metallurgical artefacts, such as copper ore fragments, copper slag and raw copper, as well as finished copper and bronze artefacts, are concentrated mainly in Late Copper Age to Middle Bronze Age layers. The chemical compositions of the slag and raw metals confirm Fe—Zn tetrahedrite–tennantite (fahlore) smelting. The ore was most probably imported from the 30–50 km distant copper ore deposits (mainly fahlore) of Schwaz–Brixlegg, in the Lower Inn Valley. The small amount of slag and the presence of slagged and thermally altered ceramic fragments suggest copper production in small‐scale workshops. Most probably, sulphide‐rich ores were smelted in crucibles in a hearth fire. The process was relatively reducing below the 2Sb + 1.5O₂ → Sb₂O₃ reaction (?8.5 log fO₂ at 1100°C), producing Sb‐rich (>10 wt% Sb in metal) raw copper. Inhomogeneous slag remains containing high amounts of sulphide and metal inclusions suggest a poor separation of the metal, matte (copper sulphide) and silicate/oxide melt during the smelting process.     

LEAD ISOTOPE ANALYSES OF ISLAMIC POTTERY GLAZES FROM FUSTAT,EGYPT*

Lead isotope analyses have been undertaken on a group of Islamic lead‐glazed pottery artefacts from Fustat, Egypt, spanning the period from the eighth to the 14th century ad , that had previously been the subject of a comprehensive typological, chronological, petrographic and technological study. Comparison of the lead isotope ratios for the glazes with those for lead ores from Egypt, Iran, Tunisia, Anatolia, Greece, Sardinia and Spain provided information on the possible sources of the lead used in the production of the glazes. The results show that the lead used in glaze production by the Islamic potters at Fustat was most probably obtained from distant ore sources in Iran or Tunisia, Sardinia, Spain and the Taurus Mountains. Different ore sources were favoured in different periods and, to a limited extent, for different types of pottery, but at no time did the Fustat potters use the potentially more accessible Egyptian ore sources.     

LEAD ISOTOPE CHARACTERISTICS OF THE CYPRUS COPPER ORE DEPOSITS APPLIED TO PROVENANCE STUDIES OF COPPER OXHIDE INGOTS

Nearly 200 new lead isotope analyses of sulphidic and oxidized ores from 26 copper mines on Cyprus show that the mines from different geological regions group in five distinctive isotopic groups, each with a substructure, related to the geological history of the ore formation. Comparison of lead isotope compositions of Bronze Age artefacts with these data can in many cases reveal the actual mines from which the copper for particular artefacts was obtained. The particular case of the provenance of the copper for 78 Late Bronze Age copper ‘oxhide ingots’found in Cyprus, Crete, Greece, Sardinia, Turkey and Bulgaria is discussed. The data show that all oxhide ingots so far analysed, dating to the fourteenth century BC and later, were made of copper consistent isotopically with only one mining region in the geographical north of Cyprus, and especially the Apliki mine. The study provides further evidence which supports the validity of the conventional approach to the use of lead isotope analysis for provenancing metals; this evidence is antithetical to recent suggestions of a model for the production of copper oxhide ingots which involved widespread mixing of copper from a number of ore sources throughout the Mediterranean.     

Application of Kernel Density Estimates to Lead Isotope Compositions of Bronzes from Ningxia,North‐West China

The aim of this paper is to apply kernel density estimates (KDEs) to the visualization and interpretation of lead isotope data from bronze assemblages found along the northern border of central China, here designated as the Arc. New lead isotope analyses of 30 leaded tin–bronze artefacts from the Wangdahu cemetery (c.500–300 bc ) in the Ningxia Hui Autonomous Region, north‐west China, provide the basis for the discussion. By using multivariate KDEs and the calculated likelihood of the overlap, the present work shows that the Wangdahu objects feature a unique linear array of isotope ratios, representing an important element of overall bronzes from the Arc in the first millennium bc . This characteristic isotope signature is fundamentally different from that of Dajing ores in north‐east China, as well from that of early Qin bronzes in Shaanxi and Gansu provinces. This suggests that a variety of metal resources were utilized by peoples living in the Arc. The KDE approach thus proves effective at presenting and comparing lead isotope data.     

A GEOLOGICAL PERSPECTIVE ON THE USE OF Pb ISOTOPES IN ARCHAEOMETRY

Lead isotope ratios in ore bodies and magmatic rocks depend in a complex way on several a priori independent parameters, including the geological age of the tectonic province in which the ores and magmas formed and its U/Pb (μ) and Th/U (κ) ratios, two very sensitive parameters characteristic of metal sources. All these parameters are entangled in hard‐to‐read Pb isotopic ratios. With respect to the commonly used fingerprinting techniques, which rely on the comparison of raw isotope ratios, the main motivation for the present work is to provide a method for making geologically and geochemically educated guesses about metal provenance even in the absence of isotopic data on reference ores. It shows how to unscramble a geological model age and μ and κ information from isotopic measurements. This approach brings to light a new organization of the Pb isotope database and an untapped wealth of information that can be used for provenance studies and other archaeometric purposes. We provide expressions with which to calculate these parameters and, using literature data, demonstrate how Pb isotopes in ores and magmas define clear zones in the silver‐rich provinces of the Central Andes. We further show how the geological model age and μ and κ values fingerprint production areas in 16th–18th century silver coins minted in Mexico and South America. Finally, we use Pb isotopes to illustrate how the Reconquista of the Emirate of Granada (1482–91) and the seizure of the Betic silver mines are reflected in the silver coins of the Catholic Monarchs.     

Local recipes or distant commodities? Lead isotope and chemical compositional analysis of glaze paints from the Salinas pueblos,New Mexico

For nearly four hundred years, Pueblo potters in the Rio Grande Valley of New Mexico produced technologically innovative glaze-decorated bowls and exchanged them widely among different villages. While potential sources of lead ores used to make glaze paints are found throughout the Rio Grande Valley region, researchers have only recently begun to identify which ore sources potters exploited and to understand the social and economic factors underlying patterns of ore resource use. In this paper we use stable lead isotope and electron microprobe analysis of glaze paints on Rio Grande Glaze Ware made at two Salinas pueblos to identify ore sources and glaze recipes used by their potters. Despite some isotopic overlap of ore sources, the lead isotope data point to regular exploitation of ores from the Socorro area of the southern Rio Grande. Salinas potters apparently used other sources as well, and likely mixed ores from different sources. We also identify four local glaze recipes that appear to incorporate multiple ore sources, suggesting that Salinas potters obtained raw ores rather than finished glaze paints.     

Local mining or lead importation in the Roman province of Africa Proconsularis? Lead isotope analysis of curse tablets from Roman Carthage,Tunisia

This study attempts to determine if there was Roman lead mining in Africa Proconsularis, approximately the area of modern day Tunisia, using lead isotope analysis. Another important aspect of the study is the innovative use of electron microprobe analysis (EMPA) as a screening tool to greatly reduce the number of expensive lead isotope analyses needed for the study. The EMPA X-ray mapping for arsenic, antimony, copper, and silver narrowed the sample of curse tablets to those most likely produced from Tunisian ores; these tablets were then tested using thermal ionization mass spectrometry (TIMS) analysis. A total of 96 Roman lead curse tablets from Carthage, Tunisia were screened with EMPA and twenty selected for TIMS to determine the ore sources of the lead used to manufacture the tablets. Comparing the lead isotope ratios of twelve of the sixteen tablets most likely to be made of Tunisian lead to samples of Tunisian ores suggests that the Romans were mining lead in Africa Proconsularis and were not relying solely on imports.     

秦始皇帝陵园出土彩绘青铜水禽铜矿料来源探索

关于秦始皇帝陵出土彩绘青铜水禽铜矿料来源的研究,对进一步研究秦代的物质文化、青铜器冶铸工艺、装饰工艺以及铜矿来源均具有重要意义。本研究对部分秦始皇帝陵园出土彩绘青铜水禽基体进行了铅同位素分析及微量元素分析。并在此基础之上,与甘肃东部及关中西部出土的部分早期秦文化铜器、国墓地出土的部分铜器、周原李家铸铜作坊出土的部分铜器、山西中条山、江西瑞昌、江西铜岭、安徽铜陵以及湖北大冶铜绿山古铜矿以及秦岭山区的部分现代铜矿的相关数据进行了对比研究。结果发现,秦始皇帝陵园出土的青铜水禽使用了相同的矿料,且与绝大多数早期秦文化铜器所使用的矿料基本相同,但与国墓地以及李家铸铜作坊出土西周铜器的矿料明显有别。秦人使用的铜矿与秦岭山区现代铜矿较为接近,表明秦人的铜矿来源可能与秦岭山区有关。     

ON THE COMPOSITION AND PROVENANCE OF METAL ARTEFACTS FROM POLIOCHNI ON LEMNOS

Summary. The majority of the well-stratified Early Bronze Age metal objects from Poliochni, with the exclusion of one hoard find, was analyzed for their chemical and lead isotope composition. The results show that a major change occurred in the metal used at Poliochni during periods contemporary with Troy I and Troy II. Unalloyed or arsenical copper with relatively high lead contents during the earliest two periods 'azzurro' and 'verde' is gradually replaced and supplemented by tin bronze which, during period 'giallo', i.e., by the end of Troy II, becomes the dominant metal type. Lead isotope abundance ratios in the earlier artefacts are consistent with a derivation of the metal from regional ore sources but the trace element abundance pattern is not. Concurrent with the appearance of tin bronzes is an increase in the diversity of ore deposits exploited; for about one third of the artefacts from period 'giallo' there is as yet no matching ore source in all Anatolia and the Eastern Mediterranean. It is argued that the tin bronzes have been imported as such but that the lead isotope signature does not provide any direct clues to the origin of the tin.