EFFECT OF CAESIUM AND STRONTIUM ON REAL STRUCTURE OF FELDSPAR AND CARBONATE MINERALS. V.V.Akimov and V.L.Tauson, Institute of Geochemistry, Irkutsk, 664033, Russia

The processes of the defects generation under mechanical dispergation of minerals are studied using the crystals of potassium feldspars and calcium carbonates from the genetically different deposits. The type and characteristics of dislocation structure are estimated as a function of dispergation time in the ball-mill planetary activator and mineral sample to milling balls mass ratio. It is shown that different channels of relaxation of structural strains are realized depending on chemical composition of samples: the defects formation and their ordering (polygonization of dislocations), and the redistribution of impurities throughout the crystallite accompanied by the formation of their complexes with the dislocations. The physicochemical modelling of the effect of fractionation of impurities into imperfect crystals by computer (Tauson & Akimov, 1992) showed that caesium stabilizes the regular dislocation structures (dislocation walls and nets) in potassium feldspar whereas strontium stabilizes the dislocation defects in carbonates (calcite and dolomite). This is supported by the data on submicroscopical structure obtained by the Fourier analysis of diffraction line profiles. After a lapse of dispergation time, the size of coherently scattering blocks is stabilized and only microstrains are changing. The change in the starting temperature of Cs vapour generation under thermal atomic absorption analysis in graphite furnace also supported the presence of dislocation-assistant Cs in K-feldspar. The data obtained are important for the creation of effective technology of the burial of wastes containing radioactive isotopes of Cs and Sr by use of imperfect mineral crystals in the synrocks.

This study is supported by MacArthur Foundation.

Reference Tauson V.L. & Akimov V.V. (1992) Atomic Energy 72, p.251-255.