Dating of archaeological flints by fluorine depth profiling: new insights into the mechanism of fluorine uptake

To understand the mechanism underlying fluorination of buried archaeological flints, samples of amorphous silica have been subjected to fluorine incorporation either by aqueous treatment or by ion implantation. The nuclear reaction analysis technique using the resonant 19F(p, αγ)16O reaction at 872 keV has been used to obtain profiles of fluorine with an automated electrostatic energy scanning system. Our results emphasize the role of defects for F uptake and allow us to propose a tentative mechanism for F diffusion. The use of synthetic hydrated silica appears promising to simulate the geochemical weathering of chalcedony. (orig.)