Shaft-hole axes from Caput Adriae: Mineralogical and chemical constraints about the provenance of serpentinitic artefacts

The change of raw materials used to produce stone axes during the Neolithic to Copper Age transition in northeastern Italy, central and western Slovenia and northwestern Croatia (Caput Adriae) has been recently linked to the development of early European metallurgy. Serpentinite shaft-hole axes occur commonly in the archaeological context of this region and their rounded irregular shape suggests that the raw material was mainly sourced from secondary deposits. The aim of the present study is to characterize with multiple analytical methods, including synchrotron radiation, the axes and locate the primary outcrop(s) of raw materials and related secondary exploitation areas. All the analysed artefacts are manufactured from peridotites and probably pyroxenites completely metamorphosed in greenschist facies and characterized by antigorite, diopside and magnetite, sometimes rimmed by penninite. Mineralogical and petrographic data exclude most Eastern Alps outcrops as possible raw material sources, thus limiting the research to the Hohe Tauern. Chemical data reveal a close homogeneity for the peridotite-derived axes and therefore demonstrate a selection of the most suitable raw material for axe production. Provenance from Hohe Tauern and related secondary deposits of the Drava River hydrographical system agrees with previous studies, as this region is rich in copper ore deposits, which have been exploited since prehistory.