⁵⁷Fe Mössbauer spectroscopy and x-ray diffraction study of some complex metamict minerals

Abstract

Metamict minerals are a class of natural amorphous materials which were initially crystalline but self-radiation damage mainly from alpha decays of ²³⁸U and ²³²Th series inside the structure can produce partially or fully amorphization (metamictization) of these minerals. This paper reports the results of ⁵⁷Fe Mössbauer spectroscopy, gamma-ray spectrometry and X-ray diffraction (XRD) study of some complex metamict minerals like: davidite-(La), gadolinite, steenstrupine-(Ce), vesuvianite and comparatively epidote. The absorbed α-dose for these minerals varies in wide range from 1.9 × 10¹⁴ α-decay/mg (epidote) to as high as 2.7 × 10¹⁶ α-decay/mg (steenstrupine). The Mössbauer spectra show decreasing IS values (except steenstrupine) for Fe²⁺ components with absorbed α-dose. Rather unexpected feature of these spectra is a noticeable decrease of the spectral line widths with increasing absorbed α-dose both Fe²⁺ and Fe³⁺ components in gadolinite, davidite and steenstrupine.