Complementary use of X-ray methods to study ancient production remains and metals from Northern Portugal

Abstract

Archaeological artefacts recovered at Castanheiro do Vento (Northern Portugal) were characterised by integrating macro and micro-energy dispersive X-ray fluorescence spectrometry (EDXRF) and scanning electron microscopy with X-ray microanalysis. The collection includes metallurgical remains (ceramic crucibles, a metallic nodule and a vitrified fragment) and metals (tools and ornaments) whose chronology spans from the Chalcolithic to the Roman Age. The study of production remains was able to identify distinct copper-based metallurgical operations including the smelting of copper ores, the melting of copper and tin and/or the melting of bronze scrap. Micro-EDXRF identified copper and arsenical copper tools as well as bronze and leaded bronze ornaments. The composition of tools (Cu with varying As contents: 0.46–3.6%) reveals an incipient technology, typical of the Chalcolithic till the Middle Bronze Age. On the contrary, ornaments are composed by different alloys – low tin bronze (4.8% Sn), high tin bronze (14.9% Sn) and high tin-leaded bronze (16.5% Sn and 2.4% Pb) − evidencing technological and economic choices that clearly indicate a late period such as the Roman Age. In conclusion, this multiproxy approach was able to study those ancient artefacts with a minimum impact on their archaeological and museological significance while providing important answers to the interpretation of the archaeological settlement and to better understand the metallurgical evolution in the Portuguese territory. Copyright © 2014 John Wiley & Sons, Ltd.