Oxidation of Olivines

Abstract

THE alteration of olivines by oxidation is well known in natural processes, and Haggerty and Baker¹ have recently shown that it is primarily responsible for high temperature alteration in lavas. They carried out heating experiments in air on hand picked unaltered grains of composition 20 per cent fayalite (Fe₂SiO₄) at temperatures from 600°–1,000° C. We have made similar investigations on various members of the forsterite–fayalite series over a wider temperature range with a view to defining the structural changes that take place in the oxidative breakdown of an olivine and to establish the atomic mechanisms responsible. Our experiments, using X-ray single-crystal and powder methods, infrared spectroscopy and electron optical and diffraction techniques, reveal complexities not mentioned by Haggerty and Baker.