Obsidian characterization by laser ablation ICP-MS and its application to prehistoric trade in the Mediterranean and the Near East: Sources and distribution of obsidian within the Aegean and Anatolia

For geological studies, interest in mass spectrometry with an inductively coupled plasma as an ion source and its association with laser ablation as a sample introduction technique (LA-ICP-MS) has steadily increased during the past few years and is now being developed in other fields such as archaeology. After a description of the analytical procedure and the calculation method, we show the potential of this technique to characterize, almost non-destructively, archaeological artefacts. Among the 70 elements that could be routinely analysed by LA-ICP-MS with detection limits below the ppm level, we choose to determine the more critical ones in order to evaluate the geochemical models of the magmatic process (major elements, rare earths and some transition elements). A detailed survey of Cappadocian obsidian flows is given, and includes the characterization of nine different sources. Evidence of complex trade activities is clearly shown by the obsidian tools found at different prehistoric sites (from Neolithic to Bronze Age levels) in the Mediterranean and the Near East. New results obtained on some archaeological sites located in Turkey, Syria and Cyprus are presented. They show the importance of Cappadocian sources in obsidian trade. Our results show that LA-ICP-MS allows a non-destructive analysis of archaeological objects and that it combines the advantage of the different classical methods used to characterize obsidian sources (mainly XRF and INAA) with high sensitivity and rapidity. Thus LA-ICP-MS appears to be a very powerful analytical tool and, at this time, this technique is the only one which can non-destructively determine such an important number of elements with such low detection limits.