Analysis of mica inclusions using LA-ICP-MS: A new approach for sourcing raw material of ceramics

The analytical methods used for determining the origin of archaeological ceramics, such as petrography, X-ray powder diffraction, X-ray fluorescence spectrometry, attain their limits for differentiating bodies of similar composition, especially when they derive from the alteration of granitoid rocks. Our new approach is based on the chemical analysis of biotite inclusions in ceramic bodies using laser ablation-inductively coupled plasmamass spectrometry, and enables us to identify the geological origin of the clay used. Spot analysis of the biotite inclusions contained in ceramics made from clay derived from the alteration of rocks can be linked to the original granitic massif. The thin section or rock analysis of biotite inclusions is relatively fast. The dosage of trace elements, such as lithium and vanadium establishes a filiation between the rocks and ceramics. Using this geochemical base, it is possible to establish a link between a granitic batholite and early ceramics and to propose a circumscribed production area. This article will focus on occupations located on islands from western France.