Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for spatially resolved trace analysis of early-medieval archaeological iron finds

The suitability of laser ablation TCP-MS for minor and trace analysis of ar chaeological iron finds, produced by a direct reduction process in a 'bloom ery' furnace, is reported. The analysis of elemental impurities in the iron can provide useful archaeometallurgical information on the production proc ess and the provenance of the iron. Since, even after refinement, the iron resulting from this process may contain many inclusions (slag, charcoal, ho les, etc.), a method should be used with sufficient spatial resolution to p reclude the inclusions from the analysis. The ablation parameters are selec ted such that ablation craters of approx. 100 mu m in diameter are obtained . The method is validated with low alloy steel and cast iron standard refer ence materials and by a comparative analysis with electron probe microanaly sis (EPMA). The precision is limited mainly by the homogeneity of the iron: rather than by instrumental reproducibility. The advantages and drawbacks of the method are briefly compared with EPMA. Preliminary results from the analysis of archaeological iron samples from excavations at Develier-Courte telle (Canton Jura, CH), Neftenbach (Canton Zurich, CH), Wartau (Canton St Gallen, CH) and Mont Chemin (Canton Valais, CH) are given.