Deposition of Base Ore and Alloy Elements in the Bronze Age Metal in the Trans-Urals

Abstract

The paper studies the problems of the geochemical specialization of the Bronze Age metal items from the eastern flank of the Ural mining and metallurgical province produced at the end of the third millennium BC — the middle of the second millennium BC in the Abashevo, Sintashta, Koptyakov-Seimino and the Alakul centers. The metal geochemical markers determination was performed by means of a local quantitative chemical composition analysis of 101 solid samples with an electron X-ray microanalyzer. The selection consisted of a representative series of copper and bronze items corresponding to various stages of metallurgical conversion process from the classic archaeological sites of the Trans-Urals. Systematization of the analytical data on the chemistry of items from each metal production center made it possible to identify stable compositions of micro-impurities associated with the base ores and alloys. The Abashevo and the Sintashta culture metal demonstrated a stable correlation of excess arsenic and nickel concentrations, which was partly due to the use of the Trans-Urals ores with a high content of these elements, however, the most significant concentration of arsenic (from 2 to 5 %) was observed in the finished items rather than in refined copper ingots or semi-finished products, which may indicate intentional alloying. Tin alloys in the Sintashta culture were quite rare; they demonstrated the same chemistry as the Seimin-Turbino metallurgical traditions. Large-scale use of tin for refined copper alloying was observed only in the Koptyakov-Seimino and the Alakul series. The Alakul series contained some high-tin alloying compositions close to the ideal tin bronzes (18 % Sn). It is possible that the sources of tin for them were the Kazakhstan and the Central Asia deposits. The only impurity integrating the entire ancient metal series, according to microprobe analysis, was sulfur, due to the sulfide feed stock. Sulfur was deposited in blister from the high-copper (above 20 % Cu) sulfide-silica-carbonate mineral blends that met the Bronze Age metal production criteria. The sources of raw materials were associated with the secondary sulfides of the ophiolite deposits hypergenesis zones in the Trans-Urals.