Study of element distributions in weathered marble crusts using laser ablation inductively coupled plasma mass spectrometry

The authentication of marble objects can often be very difficult. As the presence of a naturally produced weathering crust on an artefact can be used as a means of evaluating its antiquity, techniques to investigate those weathering layers can be very useful in authentication studies. In this study, the depth profiles of Mg, Al, Mn, Fe, Zn, Sr, Ba, La and Pb in weathered marble crusts were obtained using laser ablation inductively coupled plasma mass spectrometry. Ablations were performed in the free-running mode with a focused laser. In order to obtain spatial information, the samples were analysed directly without any sample preparation. Signal drift was corrected by using the ⁴³Ca signal as an internal standard. By plotting the ratios obtained as a function of the depth below the surface, significant trends were found. In order to check if quantitative results can be obtained, standards produced by adding elemental standard solutions to CaCO₃ powder were used. Accurate concentrations in the sampled micro-spots were obtained for both the minor and trace elements in the homogenized synthetic standards and also for the homogeneously distributed minor elements Mg and Sr in the marble samples.