Deconvolution of Powder ESR Spectra: Ge Centers in Natural Quartz

Abstract

A procedure for the deconvolution of complicated electron spin resonance (ESR) powder spectra into a set of spectral contours of separate paramagnetic centers is applied for the analysis of a polycomponent system of paramagnetic Ge centers in natural silica. The changes in the Ge centers system occurring during the thermal transformation of natural quartz into cristobalite are studied. The annealing at about 1300 K transforms the [GeO4/Li+]0 centers partly into the [GeO4/Na+]0 form in α-quartz and the further temperature increase leads to the capture of both defects by the cristobalite structure. A lag effect of the inheritance of the isomorphic impurities present in the α-quartz by cristobalite is established. The natural metamorphic transformations of vein quartz bodies also stimulate the repartitions of alkaline ion compositions in quartz structure. This can be detected by ESR as corresponding modifications in the compositions of Ge paramagnetic centers. ESR investigations of compositions of paramagnetic Ge centers in quartz from altered bodies reveal the enrichment of the quartz lattice of strained and granulated parts of veins by interstitial sodium. This process is caused by dissolution of sodium-containing fluid inclusions in the quartz lattice.