Departamento de Ciência dos Materiais, Faculdade de Ciencias e Tecnologia

Many aspects of bronze production during Late Bronze Age in Western Europe are so far unknown. In the present study selected artefact fragments and metallurgical debris, which include a slag fragment, from the emblematic Late Bronze Age habitat site of Castro da Senhora da Guia de Baiões (Viseu, Portugal) have been studied by optical microscopy, micro-EDXRF, SEM–EDS and XRD. Evidences

An unusual set of metallic artifacts with orientalizing character, attributed to a late period of the Late Bronze Age (LBA), was found in a shelter in Northern Portugal. Conventional and micro-energy dispersive X-ray fluorescence (XRF) analyses have been performed to ...

Studies on cultural metal artifacts can benefit greatly from microscopy techniques. The examination of microstructural features can provide relevant information about ancient manufacturing techniques, as well as about corrosion/degradation processes. In the present work, advantages of the use of multifocus imaging techniques in optical microscopy for the study of archaeological metals are presented. An archaeometallurgical study of a large collection of bronzes demonstrates the possibility of a microstructural study with no need for sample removal, which is a great advantage in the study of cultural objects. In addition, the study of mounted samples illustrates the advantages of the multifocus technique in the examination of particular corrosion features, with the possibility of three-dimensional reconstructions.

ABSTRACT The knowledge of our pre-history and ancient metal artefacts production methods can only be deeply investigated through the multidisciplinary approaches involving different analytical techniques including microscopy techniques. The present study concerns the elemental and microstructural characterization of pre-historic bronze artefacts from the Northwestern Iberia Peninsula. During Bronze Age an increment of metal artefacts production and its typological diversification is observed related to the development of metallurgical technology. Several artefacts have been found during recent excavations at the Bronze Age settlement of Fraga dos Corvos (Macedo de Cavaleiros, Portugal). The analysis of metallurgical remains points out to the existence of local metallurgical activities. Five bronze artefacts previously analysed by micro-EDXRF, an Acebuchal fibula fragment, two pendants and a riveted sheet (probably a fragment of a vessel or cauldron) with average concentration values of 10±1.1% Sn and ~2±0.5% Pb and a droplet (?) with ~5% Sn and ~4% Pb, were selected for optical microscopy (OM) and SEM-EDS analysis.Microscopy observations showed to be very important for the comprehension of pre-historic bronze metallurgy, allowing the identification of different phases, inclusions and thermomechanical processes applied during artefacts production. The fibula and the pendants show an equiaxed and twinned microstructure with slip bands (Figure 1 (a) and (c)). The characteristics observed are related to recrystallized and plastically deformed α-Cu structures. These features indicate that the artefacts were hammered and annealed (thermomechanical cycling), ending with a hammering operation. The pendants only exhibit slip bands near the surface, probably resulting from a finishing operation. Lead and Cu-S inclusions are frequently observed. The riveted sheet has an annealed microstructure with large α-Cu grains, undissolved (α+δ) eutectoid and few annealing twins. Elongated Cu-S inclusions, lead globules and pores were identified by SEM-EDS (Figure 1 (a)). Its microstructure indicates that shaping was obtained by just one or few thermomechanical cycles. The droplet presents a coarse and cored dendritic structure (Figure 1 (b)). Rounded Cu-S inclusions, lead globules and pores were also observed. Those are characteristics of a slow cooled as-cast alloy. Due to its low Sn content the (α+δ) eutectoid is absent. As a final note, microscopy techniques allowed establishing the manufacture processes involved in bronze metallurgy and to conclude that different thermomechanical processes were applied according to the typology of the artefact.Financial support received from the Portuguese Science and Technology foundation under the EarlyMetal project PTDC/HIS-ARQ/110442/2008 and the grants SFRH/BPD/73245/2010 (EF) and SFRH/BD/72369/2010 (EL). Financial support of CENIMAT/I3N through the Strategic Project LA25/2011-2012 (PEst-C/CTM/LA0025/2011) is gratefully acknowledged.

ABSTRACT Studies concerning European Proto-historic metallic artefacts can provide important clues about technological transfers during a period of time characterised by diverse cultural interactions. A collection of Proto-historic metallic artefacts from Medronhal (western Iberian Peninsula) composed by rings, bracelets and a fibula related to different cultural affiliations were investigated by micro-EDXRF to provide a major and a minor elemental characterisation. Results show that the Medronhal collection was manufactured in a Cu–Sn alloy (binary bronze) with similar Sn contents among the various types of artefacts and a low impurity pattern. Results of the type and quality of metal were compared to other artefact collections to infer about metallurgical parallels. Strong parallels with indigenous Late Bronze Age Iberian metallurgical productions were found.

Iberian produced metallic artefacts during the Early/Middle Bronze Age (2250-1250 BC) generally follow very conservative models and technologies (namely arsenical copper) that, as time goes by, get farther apart from those in use at Centre-Atlantic Western Europe, till the Late Bronze Age when production of binary bronze finally sees a late generalization. Know-how dispersion to produce binary bronze seems to occur from north to south through Western Iberia, the main role in the process being played by broad edged axes of Bujões/Barcelos type. Early production of binary bronze (1750-1250BC) comes from recent findings in Northern Portugal. This recent evidence and the archaeometallurgical study of ancient finds of axes of the referred types allow the discussion of know-how transmission modalities.

A set of bronzes recovered from Fraga dos Corvos (Macedo de Cavaleiros) archaeological site, located in Northern Portugal, was analyzed to investigate their lead isotope ratios. The studied metallic artefacts have diverse typologies and include two bar fragments, four fibulae, a pendant and fragments of a possible cauldron. Besides these, two metallurgical remains (nodule and droplet) were also analyzed. Elemental analysis by μ-EDXRF showed that bronzes have a Sn content varying between 5.1 and 13.9% and a Pb content from 1.4 to 6.1%, which allowed to select a suitable methodology for lead separation, prior to isotope ratio determinations. In these alloys the Pb isotope determinations (204Pb, 206Pb, 207Pb and 208Pb) are influenced by matrix effects that decrease the sensitivity and the reproducibility of the measurements. Analytical procedure consisted in electrochemical Pb separation by anodic oxidation. The determination of Pb isotope ratios was made by ICP-MS with a quadrupole ma...

Castro de Pragança is located in Estremadura province, in the Portuguese western coast. The site has been identified as a Copper Age fortified settlement by most of Portuguese archaeologists. However it shows evidence of later occupation, during Bronze and Iron Ages. Although most of the metal artefacts found in the site can be dated to Copper and Bronze Ages, an unusual set of nine fibulae was recovered that covers the period from the Iron Age until the Roman conquest. Non-destructive elemental analyses showed they are mostly bronzes alloys with variable lead contents. However, four of the nine fibulae are made both of bronze and iron pointing out to very important archaeological and technological issues. Until the 5th century BC the Portuguese Estremadura was a strategic region where both Mediterranean and Atlantic influences were visible in the material culture, but during the 2nd Iron Age another link increasingly grows its influence – the Continental one.

Fraga dos Corvos (Macedo de Cavaleiros, NE of Portugal) is an archaeological site which revealed a small settlement attributed to the first Bronze Age. Regarding this period, evidences of metallurgical activities like metal artifacts, fragments and nodules, a sandbox, crucible and moulds fragments, as well as vitrified products were found. Elemental analyses made by EDXRF showed that the metal worked at the site was bronze. Being in a tin-tungsten province, tin availability and sourcing is not a major issue, while a lack of copper ore sources is usually assumed for the northeast of Portugal. Yet, two small copper occurrences are known (Junqueira and Ponte do Azibo) within two days walking distance from the archaeological site. Since no Cu isotopic fractionation occurs during metallurgical processes, these two occurrences were investigated as possible Cu sources by measuring their Cu signature by high-resolution Multi-Collector ICP-MS, along with that of some metal artifacts, fragmen...