The Geochemistry of Unalloyed Copper Metallurgical Group Indicates Copper Ore Sources in the Late Bronze and Early Iron Ages of the Urals

Abstract

Trace elements in copper artifacts from Late Bronze and Early Iron Age sites in the Urals, formerly attributed to the metallurgical group of “chemically pure” copper, were analyzed using the method of laser ablation inductively coupled plasma mass spectrometry. The metal of which artifacts included in this group are made reveals geochemical markers suggesting that “pure” copper actually falls into several subgroups. The PCA analysis of the results identifies 11 clusters corresponding to various sources of copper ores and their mixtures. At least seven principal associations can be linked to copper deposits of different geological types and origin: Au-Te-Bi, Au-Se-Te-Sb, Fe-Co-Ni-As-Sb, Fe-Co-Ni -Zn, Se-Co-Fe, Ag-Pb-Ni, and Sb-Pb-Zn-As. Also, several mixed associations reflect the fusion of copper items and metal scrap initially obtained from different sources: Sn-Pb, Fe-Co-Ni-Zn + Sn, Fe-Co-Ni + Au-Te-Bi-Ag, Fe-Co-Ni + Au-Te-Bi + Sn. A separate association, for which the ore source remains unknown, consists of artifacts characterized by a low content of trace elements, jointly making up less than 0.01 wt%. The largest sample in the Late Bronze Age “pure copper” group falls within the Sn-Pb cluster representing a mixture of local copper and imported Sn-containing copper scrap. Judging by trace elements, the main sources of ore in the “pure copper” group of the Itkul and Sarmatian cultures were the Gumeshki mine and another unidentified source. Both could have been used already in the Final Bronze Age.