Isotope and trace element compositions of silver-bearing ores in the Balkans as possible metal sources in antiquity

Abstract

Ore deposits in the Balkan Peninsula were intensively mined for silver and other metals in the Roman and medieval periods. Coinage mainly issued by tribal groups between the early 5th and the end of the 3rd century BCE provides indirect evidence that silver extraction predates the Roman conquest of the region. However, identification of centers of past metal production and reconstruction of large-scale silver fluxes can only be achieved using a comprehensive geochemical database of potential ores. Here, we present high-precision Pb–Ag–S isotope data and trace element systematics for 128 ore samples from 36 mineralizations from the Balkans as well as one semi-reacted ore from a settlement site (=archaeological sample) and one andesite analyzed as a whole-rock and as a K-feldspar separate. Each ore site was selected for its geological characteristics and documented or assumed historical and/or archaeological significance.The reported data reconstruct the formation of ore bodies from large pre-existing Pb stocks derived from upper crustal sources, modified by tectonic and metasomatic processes, and eventually remobilized by magmatic activity. Lead isotope maps establish distinct isotopic domains which are linked to geological characteristics and enable an enhanced assessment of potential metal sources in provenance studies. Silver isotopes underscore the importance of hypogene ores of hydrothermal origin comprising galena or sulfosalt minerals as the main silver carrier phases and they can circumscribe ore deposits to those actually used as bullion sources of ancient coinage. We show that the Ag isotope signatures and the silver content of the argentiferous galena-rich ores in the Kopaonik and Zletovo districts (Serbia, Kosovo, and North Macedonia), combined with field evidence for historical metal production and geographical considerations, make them the most likely sources of silver which could have been used for coinage issued by mints in the interior of the Balkans.