Copper and tin isotopic analysis of ancient bronzes for archaeological investigation: development and validation of a suitable analytical methodology

Although in many cases Pb isotopic analysis can be relied on for provenance determination of ancient bronzes, sometimes the use of “non-traditional” isotopic systems, such as those of Cu and Sn, is required. The work reported on in this paper aimed at revising the methodology for Cu and Sn isotope ratio measurements in archaeological bronzes via optimization of the analytical procedures in terms of sample pre-treatment, measurement protocol, precision, and analytical uncertainty. For Cu isotopic analysis, both Zn and Ni were investigated for their merit as internal standard (IS) relied on for mass bias correction. The use of Ni as IS seems to be the most robust approach as Ni is less prone to contamination, has a lower abundance in bronzes and an ionization potential similar to that of Cu, and provides slightly better reproducibility values when applied to NIST SRM 976 Cu isotopic reference material. The possibility of carrying out direct isotopic analysis without prior Cu isolation (with AG-MP-1 anion exchange resin) was investigated by analysis of CRM IARM 91D bronze reference material, synthetic solutions, and archaeological bronzes. Both procedures (Cu isolation/no Cu isolation) provide similar δ 65Cu results with similar uncertainty budgets in all cases (±0.02–0.04 per mil in delta units, k = 2, n = 4). Direct isotopic analysis of Cu therefore seems feasible, without evidence of spectral interference or matrix-induced effect on the extent of mass bias. For Sn, a separation protocol relying on TRU-Spec anion exchange resin was optimized, providing a recovery close to 100 % without on-column fractionation. Cu was recovered quantitatively together with the bronze matrix with this isolation protocol. Isotopic analysis of this Cu fraction provides δ 65Cu results similar to those obtained upon isolation using AG-MP-1 resin. This means that Cu and Sn isotopic analysis of bronze alloys can therefore be carried out after a single chromatographic separation using TRU-Spec resin. Tin isotopic analysis was performed relying on Sb as an internal standard used for mass bias correction. The reproducibility over a period of 1 month (n = 42) for the mass bias-corrected Sn isotope ratios is in the range of 0.06–0.16 per mil (2 s), for all the ratios monitored

Evaluation of metal mobility in contaminated sediments using a sequential chemical extraction procedure and a multi-isotopic approach (Zn and Cu)

International audienceSignificant levels of trace metals issued from a variety of sources (industries, runoff from urban area, etc.) accumulate within sediments in many freshwater or marine environments. A major environmental risk is the remobilization of the contaminated particles and the increase in dissolved metal contents, getting more bioavailable for biota. In particular, natural events and anthropogenic activities (flood, dredging, etc.) can trigger the sediment resuspension, leading to changes in physico-chemical conditions surrounding solid particles (solid/liquid ratio, pH, redox potential, etc.). The distribution of trace metals between the solid and dissolved phases is then affected by chemical reactions (desorption, dissolution, etc.), sometimes resulting to an increase in dissolved pollutants. In laboratory, sequential chemical extraction (SCE) procedures are commonly applied to simulate the potential modifications of environmental conditions and assess the behavior of metals in sediments. The SCE procedures are based on the use of a series of reagents to extract metals according to their association within the solid phase including the following fractions: exchangeable, bound to carbonates and to pH dependent sites, associated to Fe-Mn oxides, linked to organic matter and sulfides, and silicate minerals. The purpose of this work was to investigate the behavior of metals (arsenic, chromium, cadmium, copper, nickel, lead and zinc) contained in sediments by coupling a SCE procedure, with Zn-zinc and Cu-copper isotopic measurements in each fraction. This study was performed on superficial freshwater sediments with distinct mineralogical compositions, sampled in three rivers impacted by industrial activities in France. The relative sequence of mobility displayed by the elements was distinct for the three sediments, involving distinct metal sources and various trapping mechanisms according to the sediments. The Zn and Cu isotopic compositions measured in bulk samples and in the different fractions showed that the isotopic ratios were strongly impacted by the physico-chemical processes. These first results highlighted that the isotopic measurements in environmental samples can potentially track the chemical reactions, responsible for the metal repartition between sediments and dissolved loads

Geochemical and sulfate isotopic evolution of flowback and produced waters reveals water-rock interactions following hydraulic fracturing of a tight hydrocarbon reservoir

International audienceAlthough multistage hydraulic fracturing is routinely performed for the extraction of hydrocarbon resources from low permeability reservoirs, the downhole geochemical processes linked to the interaction of fracturing fluids with formation brine and reservoir mineralogy remain poorly understood. We present a geochemical dataset of flowback and produced water samples from a hydraulically fractured reservoir in the Montney Formation, Canada, analyzed for major and trace elements and stable isotopes. The dataset consists in 25 samples of flowback and produced waters from a single well, as well as produced water samples from 16 other different producing wells collected in the same field. Additionally, persulfate breaker samples as well as anhydrite and pyrite from cores were also analyzed. The objectives of this study were to understand the geochemical interactions between formation and fracturing fluids and their consequences in the context of tight gas exploitation. The analysis of this dataset allowed for a comprehensive understanding of the coupled downhole geochemical processes, linked in particular to the action of the oxidative breaker. Flowback fluid chemistries were determined to be the result of mixing of formation brine with the hydraulic fracturing fluids as well as coupled geochemical reactions with the reservoir rock such as dissolution of anhydrite and dolomite; pyrite and organic matter oxidation; and calcite, barite, celestite, iron oxides and possibly calcium sulfate scaling. In particular, excess sulfate in the collected samples was found to be mainly derived from anhydrite dissolution, and not from persulfate breaker or pyrite oxidation. The release of heavy metals from the oxidation activity of the breaker was detectable but concentrations of heavy metals in produced fluids remained below the World Health Organization guidelines for drinking water and are therefore of no concern. This is due in part to the co-precipitation of heavy metals with iron oxides and possibly sulfate minerals

Evaluation of metal mobility in contaminated sediments using a sequential chemical extraction procedure and a multi-isotopic approach (Zn and Cu)

International audienceSignificant levels of trace metals issued from a variety of sources (industries, runoff from urban area, etc.) accumulate within sediments in many freshwater or marine environments. A major environmental risk is the remobilization of the contaminated particles and the increase in dissolved metal contents, getting more bioavailable for biota. In particular, natural events and anthropogenic activities (flood, dredging, etc.) can trigger the sediment resuspension, leading to changes in physico-chemical conditions surrounding solid particles (solid/liquid ratio, pH, redox potential, etc.). The distribution of trace metals between the solid and dissolved phases is then affected by chemical reactions (desorption, dissolution, etc.), sometimes resulting to an increase in dissolved pollutants. In laboratory, sequential chemical extraction (SCE) procedures are commonly applied to simulate the potential modifications of environmental conditions and assess the behavior of metals in sediments. The SCE procedures are based on the use of a series of reagents to extract metals according to their association within the solid phase including the following fractions: exchangeable, bound to carbonates and to pH dependent sites, associated to Fe-Mn oxides, linked to organic matter and sulfides, and silicate minerals. The purpose of this work was to investigate the behavior of metals (arsenic, chromium, cadmium, copper, nickel, lead and zinc) contained in sediments by coupling a SCE procedure, with Zn-zinc and Cu-copper isotopic measurements in each fraction. This study was performed on superficial freshwater sediments with distinct mineralogical compositions, sampled in three rivers impacted by industrial activities in France. The relative sequence of mobility displayed by the elements was distinct for the three sediments, involving distinct metal sources and various trapping mechanisms according to the sediments. The Zn and Cu isotopic compositions measured in bulk samples and in the different fractions showed that the isotopic ratios were strongly impacted by the physico-chemical processes. These first results highlighted that the isotopic measurements in environmental samples can potentially track the chemical reactions, responsible for the metal repartition between sediments and dissolved loads

American Precious Metals and Their Consequences for Early Modern Europe

An early version of this chapter can be found in: http://www.ehes.org/EHES_174.pdfOver the early modern period and beyond, massive amounts of silver and gold were found and mined in the Americas. This chapter reviews the consequences for the European economies. Some second-order receiver countries such as England benefited in both the short and long run. First-order receivers such as Spain and Portugal also benefited in the short run, but their continued exposure to the arrival of massive quantities of precious metals eventually led to loss of competitiveness and an institutional resource curse.info:eu-repo/semantics/publishedVersio

Geochemistry of Gold ores Mined During celtic times from the north- Western french Massif central

International audienceThe Celtic culture of Western Europe left magnificent gold objects, such as jewellery and weapons from nobility graves and hoarded coins, as well as field evidence of pre-Roman gold mining and metallurgical workshops that attest to the mining of local ores. This is the case of Central France where many precious metallic ores have been mined throughout the ages from the Prehistoric times onwards. One of the lingering problems in assessing the provenance of gold artefacts and coins is the lack of relevant data on the isotope geochemistry and mineralogy of ore sources. Forty gold ores samples were collected and studied from Limousin (French Massif Central), a very significant gold mining district from the Celtic times. Their Pb isotope compositions clearly show a local dichotomy i.e. two distinct groups of ores, one of Late proterozoic to early paleozoic pb model age and another associated to Variscan ages and consistent with field relationships, mineralogy and elemental analyses. The use of Cu and Ag isotopes, and their coupling with Pb isotopes, will refine the tracing of future metal provenance studies, but also highlight some metallurgical practices like deliberate metal additions to gold artefact or debasement of gold coins. The newly acquired Pb, Ag, and Cu isotopic data on gold ores improves our understanding of ore deposits geology and provide clarifications on the provenance of Celtic gold from this area and its economic importance