Jean Milot

Centre National de la Recherche Scientifique

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Francis Albarède

École Normale Supérieure de Lyon

Janne Blichert‐Toft

Université Claude Bernard Lyon 1

Chloé Malod-Dognin

Université Claude Bernard Lyon 1

G. Scott Davis

Australian Catholic University

Markos Vaxevanopoulos

Université Claude Bernard Lyon 1

Luc Siebenaller

Géosciences Environnement Toulouse

Sandrine Baron

Centre National de la Recherche Scientifique

Vanessa Léa

Travaux et Recherches Archéologiques sur les Cultures, les Espaces et les Sociétés

Philippe Télouk

École Normale Supérieure de Lyon

Patrick Schmidt

University of Tübingen

Cooperative Institutions

Centre National de la Recherche Scientifique

Université Claude Bernard Lyon 1

École Normale Supérieure de Lyon

Laboratoire de Géologie de Lyon : Terre, Planètes et Environnement

Université de Toulouse

Université Jean Monnet

Université Toulouse III - Paul Sabatier

Travaux et Recherches Archéologiques sur les Cultures, les Espaces et les Sociétés

Goethe University Frankfurt

Géosciences Environnement Toulouse

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Potential use of Fe isotopes for ancient non-ferrous metals tracing through the example of a lead-silver production site (Imiter mine, Anti-Atlas, Morocco)

Journal of Archaeological Science (2018)

Jean Milot Sandrine Baron Franck Poitrasson

Radiogenic nuclide

10.1016/j.jas.2018.07.004

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Citations (10)

Narrowing provenance for ancient Greek silver coins using Ag isotopes and Sb contents of potential ores

Journal of Archaeological Science (2022)

Markos Vaxevanopoulos G. Scott Davis Jean Milot Janne Blichert‐Toft Chloé Malod-Dognin

Bullion

10.1016/j.jas.2022.105645

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Citations (11)

The significance of galena Pb model ages and the formation of large Pb-Zn sedimentary deposits

Chemical Geology (2021)

Jean Milot Janne Blichert‐Toft Mariano Ayarzagüena Sanz Nadège Fetter Philippe Télouk

In an attempt to clarify the significance of Pb model ages in Pb-Zn sedimentary deposits, we report high-precision Pb isotopic compositions for 64 galenas and 52 K-feldspars, the former from ores and the latter separated from granites. All samples are from Spain and the French Pyrenees. Lead from galena ores is of unequivocal continental origin. With few exceptions, Pb model ages systematically exceed emplacement ages by up to 400 Ma, a gap which is well outside the uncertainties of ~ 30 Ma assigned to the model. The histogram of the new high-precision Pb isotope data shows prominent peaks of galena Pb model ages at 94 ± 38 Ma and 392 ± 39 Ma. When the data are consolidated with literature data and examined in 3-dimensional Pb isotope space, cluster analysis identifies five groups. The model ages of the peaks occur, in order of decreasing peak intensity, at 395 ± 40 (Middle Devonian), 90 ± 34 Ma (Middle Cretaceous), and 613 ± 42 Ma (Neoproterozoic), with two minor peaks at 185 + 26 Ma (Jurassic) and 313 ± 41 (Upper Carboniferous). To a large extent, the model ages centered around these peaks correspond to distinct localities. The ages of the peaks do not coincide with any of the Betic, Variscan, or Pan-African tectonic events, which are the main tectonic episodes that shaped Iberian geology, but instead match well-known global oceanic anoxic events. It is argued that surges of metals weathered from continental surfaces scorched during anoxic events accumulated and combined in anoxic water masses with unoxidized marine sulfide released by submarine hydrothermal activity to precipitate the primary Pb-Zn stock. Frozen Pb isotope compositions require that galenas from black shales are the source of the final ores. The sulfides were later remobilized by large-scale convective circulation of basinal and hydrothermal fluids. The peaks of K-feldspar Pb model ages are distinct from those of galenas and do not correlate with magmatic emplacement ages. It is suggested that they instead reflect local circulation in Paleozoic sediments surrounding individual plutons. While Pb isotopes can be used as a regional provenance tool, such an approach requires that the data are considered in a fully 3-dimensional space.

Radiogenic nuclide

Devonian

10.1016/j.chemgeo.2021.120444

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Silver isotope and volatile trace element systematics in galena samples from the Iberian Peninsula and the quest for silver sources of Roman coinage

Geology (2021)

Jean Milot Janne Blichert‐Toft Mariano Ayarzagüena Sanz Chloé Malod-Dognin Philippe Télouk

Abstract Silver played a key role in the progressive monetization of early Mediterranean civilizations. We combine Pb and Ag isotopes with volatile trace elements (Bi, Sb, and As) to assess whether, during the Roman occupation of Iberia, galena constituted a significant source of silver. We find that the Pb and Ag isotopic compositions of 47 samples of galena from eight different Iberian mining provinces, many of them exploited during Roman times, are uncorrelated. This indicates that their respective isotopic variabilities depend on different petrogenetic processes. Moreover, the range of Ag isotopic abundances is approximately six times wider than that displayed worldwide by silver coins in general and Roman silver coins in particular. Although galena from the Betics provides the best fit for Pb isotopes with Roman coins, their fit with Ag isotopic compositions is at best sporadic. We suggest that, together with Sb, Bi, and As, silver is primarily derived from fluids boiled off from differentiated mantle-derived magmas. These fluids, in turn, reacted with preexisting galena and functioned as a silver trap. Lead sulfides with ε109Ag of ~0 and unusually rich in Ag, Sb, Bi, and As were the most probable sources of ancient silver, whereas samples with ε109Ag departing significantly from ~0 reflect low-temperature isotopic fractionation processes in the upper crust.

Trace element

10.1130/g49690.1

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Citations (19)

From commodity to money: The rise of silver coinage around the Ancient Mediterranean (sixth–first centuries bce)

Archaeometry (2020)

Francis Albarède Janne Blichert‐Toft François De Callataÿ G. Scott Davis Pier Giorgio Debernardi

The reasons why the Western Mediterranean, especially Carthage and Rome, resisted monetization relative to the Eastern Mediterranean are still unclear. We address this question by combining lead (Pb) and silver (Ag) isotope abundances in silver coinage from the Aegean, Magna Graecia, Carthage and Roman Republic. The clear relationships observed between 109Ag/107Ag and 208Pb/206Pb reflect the mixing of silver ores or silver objects with Pb metal used for cupellation. The combined analysis of Ag and Pb isotopes reveals important information about the technology of smelting. The Greek world extracted Ag and Pb from associated ores, whereas, on the Iberian Peninsula, Carthaginians and Republican-era Romans applied Phoenician cupellation techniques and added exotic Pb to Pb-poor Ag ores. Massive Ag recupellation is observed in Rome during the Second Punic War. After defeating the Carthaginians and the Macedonians in the late second century bce, the Romans brought together the efficient, millennium-old techniques of silver extraction of the Phoenicians, who considered this metal a simple commodity, with the monetization of the economy introduced by the Greeks.

Sixth century

10.1111/arcm.12615

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Citations (28)

Formation of Fluid Inclusions during Heat Treatment of Barremo-Bedoulian Flint: Archaeometric Implications

Archaeometry (2016)

Jean Milot Luc Siebenaller Didier Béziat Vanessa Léa Patrick Schmidt

At the end of the fifth millennium bc, the development of a specialized lithic industry in the Chassey societies of south-eastern France and its dissemination as far as Catalonia and Tuscany attest to important socio-economic changes in the Mediterranean Neolithic societies. The lithic production was made on barremo-bedoulian flint that was heat-treated to improve the sharpness of the tools produced. Microscopic observations of archaeological and geological, heated and unheated barremo-bedoulian flint samples allowed us to highlight the heat-induced formation of fluid inclusions. Microthermometry analyses showed that these inclusions contain pure H2O, most probably resulting from the dehydration of length-slow (LS) chalcedony and the closure of narrow pores, according to the model proposed by Schmidt et al. (2012). Our results enable us to estimate the heating temperatures used by Chassey artisans to ≈ 230°C. We also propose the ‘pressure cooker’ model to explain the migration of liquid water in flint nodules heated to 230°C. Then, we discuss the ability of a particular type of flint to be heat-treated, and hence its value for Neolithic society, which depends on: (1) the amount of LS chalcedony that ensures the water release at relatively low temperature; and (2) on the total volume of porosity available to store the dehydration water.

Chalcedony

10.1111/arcm.12256

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Citations (15)

Comment on Mints not Mines: a macroscale investigation of Roman silver coinage by J.R. Wood, M. Ponting, and K. Butcher

Internet Archaeology (2023)

Francis Albarède Janne Blichert‐Toft G. Scott Davis Liesel Gentelli Jean Milot

Wood et al. (2023), hereinafter WPB, unveils a number of historical issues relevant to Roman economy and metallurgy based on trace element and Pb isotope abundance data on a large set of important coins minted during the Roman Empire (Ponting and Butcher 2015). Here, we discuss several points which, in our view, misrepresent the work of other groups, ours included, and bias the overall interpretation of the WPB data set.

Butcher

Roman Empire

10.11141/ia.61.10.comment

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Citations (1)

A miner's perspective on Pb isotope provenances in the Western and Central Mediterranean

Journal of Archaeological Science (2020)

Francis Albarède Janne Blichert‐Toft Liesel Gentelli Jean Milot Markos Vaxevanopoulos

The conventional approach to ore provenance studies of ancient silver coins and artifacts has been to first analyze and then try to match them to published data about mining districts, a difficult task given our incomplete knowledge of these. While literary sources are useful to identify possible provenances, they potentially bias interpretations proper because of a variety of limitations of their time. Archeological evidence in the form of mining shafts, galleries, spoil heaps, and tools also provides a tangible and reliable record of mining, but dating such activity can be problematic and the record is inconsistent. Here we propose a new approach driven by Pb isotopic data rather than numismatic groups. Statistical analysis of Pb isotopic data is used to identify ore-defined isotopic clusters. This new method is based on an algorithm that predicts the number of isotopic clusters necessary to fulfill the simple condition that variance within isotopic clusters is minimized whereas inter-cluster variance is maximized. Since each cluster reflects a discrete geological episode within a particular environment broadly datable to a specific Pb model age, it can be identified as a potential source exploited by ancient miners. We explore the potential of this method in two examples using data from coins and ores respectively. In the first example, Roman Republican silver coins form three 'end-member' clusters sourced in mining districts with Cenozoic, Mesozoic, and Paleozoic Pb model ages. The example demonstrates how sources of silver used to mint coinage of the Roman Republic shifted within 50 years of the end of the Second Punic War in 201 BCE. In the second example using Aegean galena samples, Pb isotopes distinguish components with model ages datable to the Hercynian basement, the recent Aegean tectonic province, and Cyprus, noting that significant silver mining districts may remain unidentified in either Spain or the Aegean world. We further clarify a number of potential analytical issues and advocate that users of Pb isotopes for tracing archeological artifacts measure all four lead isotopes and inspect the 12 proposed isotope combinations in order to select those that provide the best representation of the data. We also emphasize that full advantage should be taken of the geologically informed parameters (model age and Th/U/Pb relationships) to identify the geological context of metal sources.

10.1016/j.jas.2020.105194

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Citations (41)

Sampling and combined Pb and Ag isotopic analysis of ancient silver coins and ores

Chemical Geology (2021)

Jean Milot Chloé Malod-Dognin Janne Blichert‐Toft Philippe Télouk Francis Albarède

The combination of Pb and Ag isotopes in silver coins, artefacts, and ores greatly helps identifying ancient metal sources and detecting alteration such as lead addition, ore mixing, and metal recycling. The present study proposes a new set of procedures suitable for high-precision analysis of lead and silver isotopes in Ag-bearing ores and ancient silver coins. The protocols for combined Pb and Ag extraction and purification are based on multi-step ion-exchange and reversed-phase partition chromatography. In addition to conventional drilling, which irreversibly damages the silver object being sampled, a new method was developed to collect metal from silver coins by etching their edges with a solution of hydrogen peroxide and ammonia (H2O2 + NH4OH), either pure or with added dispersed silicon carbide (SiC) to increase etching efficiency, a technique that only damages the coin patina. This technique can also be applied to silver artefacts other than coins with minor modifications to adapt to different object shapes. Multi-collection inductively-coupled plasma mass spectrometry (MC-ICP-MS) was used to measure the isotopic compositions of both Pb and Ag in ores and coins. Variations in Pb and Ag isotopic compositions are uncorrelated for all the material analyzed, whether ores or silver coins, which demonstrate that isotope variability results from physically different processes. Evidence of mixing between different components is observed for ores, while etched and drilled coins show a conspicuous range of Pb and Ag isotopic compositions. The latter is interpreted as resulting from mass-dependent fractionation during surficial alteration under oxidizing burial conditions, and from patina formation. Silver in patina is isotopically light due to the formation of Ag2S, while the layer below the patina is isotopically heavy. Preliminary patina removal followed by H2O2 + NH4OH etching with suspended SiC may be used as an alternative to coin drilling when the latter is not possible such as for rare and precious coins. The present techniques will further help distinguish primary Pb isotopic variability in artefacts and coins from secondary variations due to underground interaction with the water table, weathering from prolonged burial, and curatorial handling.

10.1016/j.chemgeo.2020.120028

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Citations (25)

Investigating the provenance of iron bars from Les Saintes‐Maries‐de‐la‐Mer Roman shipwrecks (south‐east France) with iron isotopes

Archaeometry (2021)

Jean Milot Marie‐Pierre Coustures Franck Poitrasson Sandrine Baron

Abstract Fe isotopes were used to determine the origin of iron bars from Les Saintes‐Maries‐de‐la‐Mer Roman shipwrecks, which was a major archaeological finding at the end of the 20th century in France. Their Fe isotope composition was measured by multi collector‐inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS) after chemical Fe purification. The results allowed us to suggest provenances that were compared with those based on trace element analyses of slag inclusions. For most of the bars, we validate the provenance hypotheses previously proposed. Two bar groups originate from the Montagne Noire metallurgical district (south‐west France), whereas a third group comes from another source, not clearly identified so far. In this context of Roman iron production, we argue for a non‐spatially segmented production, where bars were manufactured close to smelting sites. Combined trace element and Fe isotope analyses on the same objects provide crucial information about the nature of their ore source. The elemental heterogeneity, positive Eu anomaly and Fe isotopic homogeneity of several bars were inherited from gossan‐type ores, whereas the negative Eu anomaly and variable Fe isotopes signature of others most likely correspond to sedimentary iron ores. This study demonstrates that combined trace element and Fe isotopes analyses in a well‐defined archaeological context is a promising approach for provenance studies of iron metals of archaeological interest.

Trace element

10.1111/arcm.12715

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Citations (6)