Portable XRF analyzer: new opportunities for identifying stone raw materials and their sources, and assessing validity of using the analysis of raw material units

This article describes analysis of a sample of Paleolithic artifacts made of four main types of stone raw materials typical for the industries from the Northwestern and Central Altai, using an Olympus Vanta M portable X-ray fluorescence spectrometer (pXRF). The analysis of variance confirmed the absence of significant differences in concentrations of the vast majority of chemical elements measured on the ancientflaking surface and on freshly polished areas for siliceous effusive rocks (rhyolites and dacites) from the Anui-2 site, metasediments (metasiltstones and metasandstones) from the Ust-Karakol-1 site, and tuffs from the Kara-Bom site, while significant systematic and non-systematic differences were discovered for microquartzites from the Kara-Tenesh site. The data obtained confirms correctness of using portable XRF spectrometers for identifying stone raw materials of ancient artefacts from the open sites in the Altai as well as validity of direct comparison of data on the composition of ancient flaking surfaces with raw materials from the modern outcrops. The most significant petrochemical indicators are concentration of silicon, aluminum, calcium, and iron among the major elements; strontium, yttrium, and rubidium among the minor elements (for all groups of rocks), as well as their ratios with high field strength elements, such as titanium, zirconium, and niobium. The study has also led to development of new research tools for testing validity of the raw material unit (RMU) method. Previously, in the broad technological context of the Altai industries, the differentiation between the reduction products of individual blocks of raw materials was based on searching and analyzing identical combinations of macro- and microscopically determined petrographic features of artifacts, such as color, texture, features of the flaking surface, etc. The use ofXRF analyzer makes it possible to do this grouping or confirmation on the basis of stable chemical criteria.