Cu ISOTOPE RATIO VARIATIONS IN THE DIKULUSHI Cu-Ag DEPOSIT, DRC: OF PRIMARY ORIGIN OR INDUCED BY SUPERGENE REWORKING?

Haest, Maarten; Muchez, Philippe; Petit, Jérôme; Vanhaecke, Frank

doi:10.2113/econgeo.104.7.1055

Cited by 35 publications

(8 citation statements)

References 27 publications

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“…It must be emphasised, however, that the available data reflects a variety of base deposits and sulphide minerals only (galena, bornite, chalcocite, digenite, sphalerite, pyrite, chalcopyrite), of various geological ages (Cailteux and De Putter, 2019): LI ratios of the supergene deposits in the Copperbelt have not yet been characterised. These supergene deposits (iron oxides, malachite, chrysocolla and azurite) result from the secondary alteration of earlier diagenetic or hydrothermal sulphide deposits Haest et al, 2009). As discussed below, the croisette copper was most likely obtained from such supergene deposits, for which the LI ratios could differ from those reported here.…”

Section: Broad Trends: Lead Isotope Ratiosmentioning

confidence: 55%

“…Its probable origin is in Paleoproterozoic metasediments from the Kasaï Block and it hence exhibits east-west gradients in the Copperbelt, with cobalt content overall decreasing from the western to the southeastern part of the Copperbelt, including the Zambian deposits (Dewaele et al, 2006;De Putter et al, 2018). By contrast, cobalt is less abundant or absent in "late" hydrothermal Cu-Pb-Zn deposits such as Kipushi (Heylen et al, 2008), Dikulushi (Haest et al, 2009(Haest et al, , 2010 and Kansanshi (Torrealday et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

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Provenancing Central African copper croisettes: A first chemical and lead isotope characterisation of currencies in Central and Southern Africa

Rademakers

Nikis

Putter

et al. 2019

Journal of Archaeological Science

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A B S T R A C TThe Copperbelt is one of the richest copper deposits in the world and has been an important primary metal source for Central African cultures for over a millennium. The technology underlying this exploitation and the trade networks through which copper was exchanged, however, have not yet received much attention in archaeological research. This paper presents the first geochemical dataset for archaeological copper currencies in Central and Southern Africa: croisette ingots. Chemical and lead isotope analysis have been carried out for 45 precolonial copper artefacts with the aim of illuminating their provenance and production technology. The results show that highly pure copper with very low trace element content was produced, indicating the selection, beneficiation and smelting of specific Copperbelt ores. The variable croisette compositions and shapes reflected in burial assemblages support their suggested use as currencies over a large area. This study offers a highly novel contribution to provenance research in Central and Southern Africa, shedding new light on the broader trade networks associated with copper provisioning in these regions. The exploitation of a range of ore sources throughout the 2nd millennium CE has been identified, with a marked shift around the mid-15th century CE largely correlating to croisette typologies. Furthermore, these different geochemical copper signatures can be tentatively related to different Copperbelt zones. Combining these results with archaeological and historical evidence for regional copper production and consumption, this study provides a framework for the future study of copper production and exchange systems in the wider Central and Southern African region.

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Section: Broad Trends: Lead Isotope Ratiosmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Provenancing Central African copper croisettes: A first chemical and lead isotope characterisation of currencies in Central and Southern Africa

Rademakers

Nikis

Putter

et al. 2019

Journal of Archaeological Science

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“…Literature sources that reported chalcocite as the major phase present in the copper isotope analyses were used [16][17][18][19] along with new data from Coates Lake, Copper Mine, Michigan, and Udokan. Data from Kupferschiefer [20], Michigan [21,22], and Coates Lake [23] provide classic examples of sedimentary copper deposits along with the prospect, Coppermine [24].…”

Section: Types Of Chalcocite Considered and Deposits Analyzedmentioning

confidence: 99%

Origins of Chalcocite Defined by Copper Isotope Values

et al. 2018

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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 ( = 361) reveal that chalcocite from high-temperature mineralization has the tightest cluster of values of 65 Cu = 0 ± 0.6 in comparison to sedimentary copper/red bed 65 Cu = −0.9 ± 1.0 and supergene enrichment 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 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.

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“…This method is based on the application of Eq. 1: Fe, 57 Fe, 58 Ni, 62 Ni, 63 Cu, 65 Cu, 64 Zn, 66 Where Rcorr X,sample represents the corrected isotope ratio for the target analyte (Cu or Sn) in the sample (X0M 2 /M 1 , where M 1 and M 2 are the masses of the lighter and heavier isotope, respectively). Rexp X,sample represents the measured isotope ratio for the target analyte in the sample; Rexp IS,sample represents the measured isotope ratio for the internal standard admixed to the sample (i.e., Ni for Cu and Sb for Sn), and Rtheo X corresponds to the theoretical isotope ratio for the target element calculated based on the isotopic abundances given by the IUPAC [39].…”

Section: Instrumentation and Measurementsmentioning

confidence: 99%

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

et al. 2012

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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 65 Cu results with similar uncertainty budgets in all cases (±0.02-0.04 per mil in delta units, k02, n0 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 oncolumn fractionation. Cu was recovered quantitatively together with the bronze matrix with this isolation protocol. Isotopic analysis of this Cu fraction provides δ 65 Cu 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 (n042) 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.

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Cu ISOTOPE RATIO VARIATIONS IN THE DIKULUSHI Cu-Ag DEPOSIT, DRC: OF PRIMARY ORIGIN OR INDUCED BY SUPERGENE REWORKING?

Cited by 35 publications

References 27 publications

Provenancing Central African copper croisettes: A first chemical and lead isotope characterisation of currencies in Central and Southern Africa

Provenancing Central African copper croisettes: A first chemical and lead isotope characterisation of currencies in Central and Southern Africa

Origins of Chalcocite Defined by Copper Isotope Values

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

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