Analyse in situ des dessins prehistoriques de la grotte de Rouffignac par fluorescence X et diffraction X portable

The Cave of Rouffignac (Dordogne, France) is a Palaeolithic rock art site which contains numerous black drawings (mammoths, bisons, rhinoceros, horses, ibexes...). Although no direct dating was carried out until now, the artworks of this cave are generally connected with the Magdalenian Culture. A portable system coupling X-ray fluorescence and X-ray daction developed at the C2RNIF in Paris to work in museums or on monuments was used for the first time in a decorated cave. Results obtained with X-ray fluorescence confirm the main constituents of pigments : manganese, iron and barium. They also show the presence of other elements such as silicon, titanium, chromium, zinc and potassium. X-ray diffiaction allowed identifting the presence of pyrolusite (manganese dioxide), romanechite and, eventually, hollandite. These two last compounds are barium manganese oxides. Quartz is also systematically observed in the pigment. This campaign has demonstrated the possibility of poformingX-ray diffiaction in difficult environment (access to walls, temperature, and humidity) and has allowed to achieve the first diffiactogranzs in situ, directly on prehistoric representations. The first results show that the Frieze of the mammoths of the gallery Breuil has a homogeneous chemical composition, in coherence with the stylistic composition. On the other hand, the figures of the Grand Plafond have more variable chemical composition. Mots cle : Fluorescence X (XRF), diffraction X (XRD), Grotte de Rouffignac, art prehistorique, pigments prehistoriques, oxyde de manganese, in situ, systeme portable.