It is well known that the content of trace elements present in archaeological obsidians can give information on the provenance. Their quantitative determination can be obtained by using portable XRF spectrometers; however, x-ray tubes largely used as exciting source can be subjected to energy and intensity fluctuations and frequent calibrations of the systems are required in order to obtain quantitative data. In the present work a portable BSC-XRF spectrometer (Beam Stability Controlled XRF) with a beam stability control, is used to determine the content of some trace elements (Rb, Sr, Y, Zr and Nb) characterizing obsidian samples. The control of the stability is not an electronic device operating on the applied high voltage and current but consists on a direct intervention on the beam emitted by the tube used as x-ray source. The concentration of Rb, Sr, Y, Zr and Nb was determined in 57 obsidian artefacts coming form Milena, an important prehistoric site in the internal region of Sicily; quantitative determination was obtained by a method based on a multi-linear regression approach previously developed by the authors and based on a calibration procedure which used 26 petrologic standards. It should be emphasized that in the case of obsidians, a surface XRF analysis gives meaningful quantitative results since they are composed of an homogeneous matrix. Milena artefacts were found on well defined archaeological layers dated back from the Neolithic to the final Copper age; this aspect is of relevant interest because only few data exists on stratigraphic obsidians in Sicily. Analysed artefacts were randomly sampled in order to well represent the populations in the different periods. Results on compositional data of Rb, Sr, Y, Zr and Nb allowed to identify Lipari and Pantelleria islands as the main sources of the Milena obsidians and to evidence how the samples coming from these sources are distributed from Neolithic to the final Copper age.
Obsidian provenance determination by using the Beam Stability Controlled BSC-XRF spectrometer: the case of milena (sicily)
2006
Abstract
It is well known that the content of trace elements present in archaeological obsidians can give information on the provenance. Their quantitative determination can be obtained by using portable XRF spectrometers; however, x-ray tubes largely used as exciting source can be subjected to energy and intensity fluctuations and frequent calibrations of the systems are required in order to obtain quantitative data. In the present work a portable BSC-XRF spectrometer (Beam Stability Controlled XRF) with a beam stability control, is used to determine the content of some trace elements (Rb, Sr, Y, Zr and Nb) characterizing obsidian samples. The control of the stability is not an electronic device operating on the applied high voltage and current but consists on a direct intervention on the beam emitted by the tube used as x-ray source. The concentration of Rb, Sr, Y, Zr and Nb was determined in 57 obsidian artefacts coming form Milena, an important prehistoric site in the internal region of Sicily; quantitative determination was obtained by a method based on a multi-linear regression approach previously developed by the authors and based on a calibration procedure which used 26 petrologic standards. It should be emphasized that in the case of obsidians, a surface XRF analysis gives meaningful quantitative results since they are composed of an homogeneous matrix. Milena artefacts were found on well defined archaeological layers dated back from the Neolithic to the final Copper age; this aspect is of relevant interest because only few data exists on stratigraphic obsidians in Sicily. Analysed artefacts were randomly sampled in order to well represent the populations in the different periods. Results on compositional data of Rb, Sr, Y, Zr and Nb allowed to identify Lipari and Pantelleria islands as the main sources of the Milena obsidians and to evidence how the samples coming from these sources are distributed from Neolithic to the final Copper age.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
