TOWARDS A NEW METHOD OF OBSIDIAN HYDRATION DATING WITH SECONDARY ION MASS SPECTROMETRY VIA A SURFACE SATURATION LAYER APPROACH

Abstract

The obsidian hydration dating (OHD) has undergone a considerable evolution, especially with the use of nuclear analysis techniques to accurately determine the hydration rim. We develop a novel approach to the OHD employing certain mathematics of diffusion and making use of available secondary ion mass spectrometry (SIMS) data on obsidians.Our model is based on the non-steady state concentration-dependent diffusion for semi-infinite medium, where diffusion coefficient varies exponentially during diffusion,and for certain initial and boundary conditions the age equation of the obsidian diffusion dating employing SIMS derives from a differential equation that describes diffusion.An essential factor addressing our model is the surface saturation (SS)plateau level at certain depth, which is the result of the diffusion mechanism in the first 1-2 um, the physicochemical factors that address the formation of a surface saturation plateau, the stereo-chemical structure of obsidian,and certain environmental parameters, naming the method as the obsidian diffusion dating by SIMS(ODDSIMS)- SS approach. The measured data points derive from the H+ concentration-depth profile by SIMS.Application of the present model on available data of well-dated obsidians from the Aegean (Greece),Mexico and USA, provided satisfactory results.