INTRACRYSTALLINE DISTRIBUTION OF IRON ION S IN BIOTITES FROM URAL GRANITIC-ROCKS

Mossbauer spectra of 48 biotite samples from Ural granitic and associa ted rocks are carried out. Based on these spectra the estimates of Fe3 + and Fe2+ distribution between nonequivalent structure positions in b iotite are presented. It is established that Fe3+ ion is placed predom inantly at octahedric positions: Fe2+ ion distribution between nonequi valent cis- and transoctahedric positions is variable near its statist ic relations in the crystalline structure of biotite. Dimensional and symmetric parameters of both types of iron ions are greatly variable i n different samples reflecting in the variations of ultrathin NGR spec tra parameters as well as line width. The correlation of these paramet ers and redox conditions of associated granites (ironbearing facies) i s shown.