Non-ferrous metal of the Bronze Age of Northern Kazakhstan: geochemical characteristics and ore base

Abstract

The chemical composition of 29 copper and bronze artifacts from the sites of the Petrovka and Alakul Cultures located be-tween the Tobol and Ishim Rivers (the burial grounds of Bekteniz and Dzhangildy 5, and the sites of Novonikolskoye 1 and Semioz-ernoye 2; Northern Kazakhstan) were analysed using mass spectrometry with inductively coupled plasma and laser ablation. The sites are 14C dated to the interval between the 19th–17th centuries BC. In the examined sample, the leading metallurgical group with a slight prevalence in both Petrovka and Alakul metals was “pure” copper; the second part of the metal was represented by tin bronzes — low-alloyed (up to 8 wt.% Sn) in the Petrovka, and high-alloyed (Sn up to 21 wt.%) in the Alakul Culture. The statistical analysis of the main components of trace elements in the metal demonstrated a division into six main geochemical groups. Among these, tin bronzes with an uninterpretable copper component (10 specimens), “pure” copper of Ural origin with Fe-Co-Ni-As-Zn correlations (9 specimens), and “pure” copper with polymetallic Sn-Pb-As-Ag-Se specialization (10 copies), corresponding to the ores of copper deposits of the Kokshetau anticlinorium, can be identified. An overview of the tectonic structures of Northern Ka-zakhstan shows the nearby presence of several porphyry copper and skarn deposits with ancient mines (Imantau, Baksinskoye, Akkan-Burlukskoye, etc.), which likely served as sources of copper ore. Closely associated with these are Greisen and quartz-vein-greisen tin deposits, but there is no reliable information about their use in ancient times. According to the composition of tin alloys in the analysed metal, two main types can be distinguished: tin (without correlation with other impurity elements) when using pure cassiterite, and tin-lead (with increased concentrations and correlation of As, Au, Bi, etc.) when using cassiterite-sulfide ores. The data show the association of the Bronze Age sites of Northern Kazakhstan with the ore and raw materials base in this region, and the intensity of trade exchange of metallurgical products between the Ural and Kazakhstan centers of metal production.