REPRODUCIBILITY OF ELEMENTAL ANALYSES OF BASALTIC STONE ARTEFACTS BY QUADRUPLE ICP–MS USING DIFFERENT SAMPLE SIZES AND DIGESTION METHODS, WITH IMPLICATIONS FOR ARCHAEOLOGICAL RESEARCH

摘要

Using high-precision inductively coupled plasma mass spectrometry (ICP–MS), we measured >40 elements in basalts sampled by diamond micro-drills to evaluate the effectiveness of different digestion methods and the reproducibility of elemental analysis for different sample sizes from 5?mg to 100?mg. The results indicate that those elements that are most suitable for geochemical characterization, such as rare earth elements (REE), high-field strength elements (HFSE) and certain mobile elements (Rb, Sr, Th, U), show excellent reproducibility with an average relative standard deviation (RSD) of 3% between open-beaker and pressured ‘bomb’ digestion methods. This observation rules out the presence of refractory phases such as zircon, which can only dissolve in pressured ‘bombs’, and suggests that the results from open-beaker digestion are reliable. The ICP–MS data for powders of different weights ranging from 10 to 100?mg collected from two fine-grained basalt artefacts display excellent reproducibility, with a RSD of <5% for the most important elements. The reproducibility is reduced when including the 5?mg weight fraction (RSD of ～2–9%), which is still sufficient for archaeological applications. Our results demonstrate the usefulness of 10?mg samples for elemental measurement, which is valuable for geochemical characterization and sourcing of fine-grained basalt artefacts from museum collections that require minimal destructive sampling.