TY - JOUR
T1 - Reconstructing the geological provenance and long-distance movement of rectangular, fishtail, and croisette copper ingots in Iron Age Zambia and Zimbabwe
AU - Stephens, Jay
AU - Killick, David
AU - Chirikure, Shadreck
N1 - Funding Information:
The authors JS and DK would like to acknowledge funding received for this project through the National Science Foundation (NSF BCS 1852598, https://www.nsf.gov/awardsearch/showAward?AWD_ID=1852958&HistoricalAwards=false). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank the Livingstone Museum and Museum of Human Sciences for granting access to their collections, and the National Heritage Conservation Committee in Zambia and the National Museums and Monuments board of Zimbabwe for permits issued for export and destructive analysis of these samples. We are similarly thankful to the extremely dedicated work by Livingstone Museum and Museum of Human Sciences staff to preserve these archaeological collections for researchers. In particular, we would like to thank Maggie Katongo, Fortune Munetsi, Rutendo Komborayi, and Nyararai Mundopa for their assistance in these collections. In Arizona, we are thankful to Dr. Joaquin Ruiz for access to his laboratory, Dr. Mark Baker and Dr. Jason Kirk for their invaluable help in the lab and assistance in running the MC-ICP-MS. We thank Dr. Mary Kay Amistadi for her invaluable help and measurement of the trace element concentrations. We thank Stephanie Martin for her work in ArcGis to produce the map figures. We thank ARMI-MBH Analytical for providing materials to evaluate our dissolution procedure. We also thank the three reviewers for their time and comments.
Publisher Copyright:
© 2023 Stephens et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
PY - 2023/3
Y1 - 2023/3
N2 - The southern third of Africa is unusually rich in copper ore deposits. These were exploited by precolonial populations to manufacture wound-wire bangles, other forms of jewelry, and large copper ingots that were used as stores of copper or as forms of prestige. Rectangular, fishtail, and croisette ingots dating between the 5th and 20th centuries CE have been found in many locations in the Democratic Republic of the Congo (DRC), Zambia, and Zimbabwe, with isolated finds in Malawi and Mozambique. Molds for casting these ingots have been found mostly in the Central African Copperbelt, but also around the Magondi Belt copper deposits in northern Zimbabwe. For years, scholars have debated whether these ingots were exclusively made in the Copperbelt or if the molds found in Zimbabwe indicate that local copies were produced from Magondi Belt copper ore (Garlake 1970; Bisson 1976). Before the recent application of lead isotopic and chemical methods to provenance copper in central and southern Africa, there was no way to discern between these hypotheses. Rademakers et al. (2019) and Stephens et al. (2020) showed that copper artifacts from southern DRC (mostly from Upemba) and from northwestern Botswana (Tsodilo Hills) match the lead isotope ratios of ores from the Copperbelt. Building upon these previous studies, we present here the first results from a copper provenance project across the southern third of Africa, from the Copperbelt to northern South Africa. We apply lead isotopic analysis (LIA) and chemical analyses to establish the provenance of 29 croisette ingots recovered in Zimbabwe, 2 fishtail and 1 rectangular ingot recovered from sites in Zambia, and an “X” shaped ingot smelted in an experiment in Zambia in the 1970’s. Our chemistry and lead isotopic results indicate that 16 of these objects were smelted with copper from the Copperbelt, 16 objects source more specifically to the Kipushi deposit within this geological district, and only one HXR ingot sources to the Magondi Belt in Zimbabwe. Taken together, we clearly illustrate that croisette ingots were traveling significant distances to reach their eventual sites of deposition, and that there was also local production of these objects in Zimbabwe.
AB - The southern third of Africa is unusually rich in copper ore deposits. These were exploited by precolonial populations to manufacture wound-wire bangles, other forms of jewelry, and large copper ingots that were used as stores of copper or as forms of prestige. Rectangular, fishtail, and croisette ingots dating between the 5th and 20th centuries CE have been found in many locations in the Democratic Republic of the Congo (DRC), Zambia, and Zimbabwe, with isolated finds in Malawi and Mozambique. Molds for casting these ingots have been found mostly in the Central African Copperbelt, but also around the Magondi Belt copper deposits in northern Zimbabwe. For years, scholars have debated whether these ingots were exclusively made in the Copperbelt or if the molds found in Zimbabwe indicate that local copies were produced from Magondi Belt copper ore (Garlake 1970; Bisson 1976). Before the recent application of lead isotopic and chemical methods to provenance copper in central and southern Africa, there was no way to discern between these hypotheses. Rademakers et al. (2019) and Stephens et al. (2020) showed that copper artifacts from southern DRC (mostly from Upemba) and from northwestern Botswana (Tsodilo Hills) match the lead isotope ratios of ores from the Copperbelt. Building upon these previous studies, we present here the first results from a copper provenance project across the southern third of Africa, from the Copperbelt to northern South Africa. We apply lead isotopic analysis (LIA) and chemical analyses to establish the provenance of 29 croisette ingots recovered in Zimbabwe, 2 fishtail and 1 rectangular ingot recovered from sites in Zambia, and an “X” shaped ingot smelted in an experiment in Zambia in the 1970’s. Our chemistry and lead isotopic results indicate that 16 of these objects were smelted with copper from the Copperbelt, 16 objects source more specifically to the Kipushi deposit within this geological district, and only one HXR ingot sources to the Magondi Belt in Zimbabwe. Taken together, we clearly illustrate that croisette ingots were traveling significant distances to reach their eventual sites of deposition, and that there was also local production of these objects in Zimbabwe.
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U2 - 10.1371/journal.pone.0282660
DO - 10.1371/journal.pone.0282660
M3 - Article
C2 - 36947492
AN - SCOPUS:85150800598
SN - 1932-6203
VL - 18
JO - PloS one
JF - PloS one
IS - 3 March
M1 - e0282660
ER -