Copper Isotopes

Gold parting enabled the production of very pure gold for various purposes from the sixth century BC onwards, but analytical proof of this pyrotechnical process is difficult. We describe a new analytical approach for the identification of purified gold combining silver and copper isotopic with trace element analyses. Parting experiments were performed with gold-silver-copper alloys using the classical salt cementation process to investigate potential silver and copper isotope fractionation and changes in trace element concentrations. In addition, we provide the first comprehensive dataset of silver isotope ratios of archaeological gold objects from the Mediterranean and Central Europe to test whether or not gold refining can be identified on the basis of isotope systematics. The results show that very heavy silver and copper isotopic compositions are clear evidence for parted gold, but that the application of copper isotopes might be limited.

The origin of chalcocite is explored through a comparison of the copper isotope values of this mineral from supergene enrichment, sedimentary copper/red bed, and high-temperature hypogene mineralization around the world. Data from the literature and the data presented here (n=361) reveal that chalcocite from high-temperature mineralization has the tightest cluster of values of δCu65=0±0.6 in comparison to sedimentary copper/red bed δCu65=-0.9±1.0 and supergene enrichment δCu65=+1.9±1.8. Although the errors of the means overlap, large portions of the data lie in different values, allowing for distinguishing ranges for δCu65 of <−1‰ for sedimentary copper/red bed, between -1 and +1 for high-temperature hypogene, and >+1 for supergene enrichment chalcocite. The copper isotope values of sedimentary copper/red bed and supergene enrichment chalcocite are caused by redox reactions associated with the dissolution and transport of copper, whereas the tighter range of copper isotope val...

The origin of chalcocite is explored through a comparison of the copper isotope values of this mineral from supergene enrichment, sedimentary copper/red bed, and high-temperature hypogene mineralization around the world. Data from the literature and the data presented here (í µí±› = 361) reveal that chalcocite from high-temperature mineralization has the tightest cluster of values of í µí»¿ 65 Cu = 0 ± 0.6 in comparison to sedimentary copper/red bed í µí»¿ 65 Cu = −0.9 ± 1.0 and supergene enrichment í µí»¿ 65 Cu = +1.9 ± 1.8. Although the errors of the means overlap, large portions of the data lie in different values, allowing for distinguishing ranges for í µí»¿ 65 Cu of <−1‰ for sedimentary copper/red bed, between −1 and +1 for high-temperature hypogene, and >+1 for supergene enrichment chalcocite. The copper isotope values of sedimentary copper/red bed and supergene enrichment chalcocite are caused by redox reactions associated with the dissolution and transport of copper, whereas the tighter range of copper isotope values for hypogene minerals is associated with processes active with equilibrium conditions.

Abstract
a,
N.H. Gale
a
a
*, A.P. Woodhead
a
, Z.A. Stos-Gale
b
, A. Walder
b
, I. Bowen
Isotrace Laboratory, Nuclear Physics Building, Keble Road, Oxford OX1 3RH, UK
b
VG Elemental, Ion Path, Road Three, Winsford, Cheshire CW7 3BX, UK Received 4 September 1998; accepted 12 December 1998
Copper isotopic compositions have been measured both in natural copper minerals from supergene/oxidation zones and in some ancient metal artefacts using two different instruments. Measurements were first made using a low temperature thermal ionisation technique with a thermal ionisation mass spectrometer (TIMS); independent data was obtained using a commercial inductively coupled plasma (ICP) magnetic sector multiple collector mass spectrometer. Significant variations of isotopic composition were found in both types of material, suggesting that there may be considerable potential for copper isotope analyses in metal provenance studies, at the least as a supplement to lead isotope studies. For minerals, d values ranging from 21.63 to 17.71 were obtained, whilst archaeological artefacts had d values from 10.22 to 14.32. This study also made a preliminary examination which suggests that fractionation of the isotopic composition of copper does not occur during smelting and fire refining processes thought to have been used in ancient times. (Int J Mass Spectrom 184 (1999) 1–9) © 1999 Elsevier Science B.V.
Keywords: Copper; Isotopes; TIMS; MC-ICP-MS; Anomalies; Provenancing; Archaeometallurgy

Gold parting enabled the production of very pure gold for various purposes from the sixth century BC onwards, but analytical proof of this pyrotechnical process is difficult. We describe a new analytical approach for the identification of purified gold combining silver and copper isotopic with trace element analyses. Parting experiments were performed with gold-silver-copper alloys using the classical salt cementation process to investigate potential silver and copper isotope fractionation and changes in trace element concentrations. In addition, we provide the first comprehensive dataset of silver isotope ratios of archaeological gold objects from the Mediterranean and Central Europe to test whether or not gold refining can be identified on the basis of isotope systematics. The results show that very heavy silver and copper isotopic compositions are clear evidence for parted gold, but that the application of copper isotopes might be limited.

Iron (δ56Fe) and copper (δ65Cu) stable isotope compositions in blood of adult human include a sex effect, which still awaits a biological explanation. Here, we investigate the effect of menopause by measuring blood δ56Fe and δ65Cu values of aging men and women. The results show that, while the Fe and Cu isotope compositions of blood of men are steady throughout their lifetime, postmenopausal women exhibit blood δ65Cu values similar to men, and δ56Fe values intermediate between men and premenopausal women. The residence time of Cu and Fe in the body likely explains why the blood δ65Cu values, but not the δ56Fe values, of postmenopausal women resemble that of men. We suggest that the Cu and Fe isotopic fractionation between blood and liver resides in the redox reaction occurring during hepatic solicitation of Fe stores. This reaction affects the Cu speciation, which explains why blood Cu isotope composition is impacted by the cessation of menstruations. Considering that Fe and Cu sex differences are recorded in bones, we believe this work has important implications for their use as a proxy of sex or age at menopause in past populations. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.

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 +...

R. Lehmann, B. Rasink, A. Lehmann, G. Avraam, Bronzezeitliches Gold aus Niedersachsen – Funktion, Herstellung und Herkunft, F.A.N.-Post Mitteilungsblatt des Freundeskreises für Archäologie in Niedersachsen e.V., Hannover 2018, ISSN 2509-2391, S. 30-33

In der frühen und alteren Bronzezeit Mitteleuropas
belegen monoton zusammengesetzte
Bronze-Horte einen WertmaBstab in
Form von Beilen oder anderen Formen...

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.