&#۱۵۷۸;&#۱۵۹۳;&#۱۶۱۰;&#۱۶۱۰;&#۱۶۰۶; &#۱۵۸۱;&#۱۵۷۵;&#۱۶۰۴;&#۱۵۷۸; &#۱۵۷۵;&#۱۶۰۳;&#۱۵۸۷;&#۱۶۱۰;&#۱۵۸۳;&#۱۵۷۵;&#۱۵۸۷;&#۱۶۱۰;&#۱۶۰۸;&#۱۶۰۶;&#۱۵۴۸; &#۱۶۰۳;&#۱۶۰۸;&#۱۵۸۵;&#۱۵۸۳;&#۱۶۱۰;&#۱۶۰۶;&#۱۵۷۵;&#۱۵۸۷;&#۱۶۱۰;&#۱۶۰۸;&#۱۶۰۶; &#۱۶۰۸; &#۱۶۰۶;&#۱۵۸۷;&#۱۵۷۶;

Mِssbauer spectra of ۵۶ biotite specimens from granitic rocks of the Canadian Appalachians are examined to evaluate the oxidation state and site occupancies of Fe cations. Mineral analyses were obtained by wavelength-dispersive X-ray spectrometry using the JEOL ۸۹۰۰ Superprobe.

All room temperature spectra of biotite exhibit remarkable similarity and have three main absorption peaks centered at about  -۰.۱, +۱.۰ and +۲.۳ mm/s, which respectively correspond to ۱) the low-energy lines of both octahedral Fe^۲+ and octahedral Fe^۳+ quadrupole doublets, ۲) the high-energy lines of octahedral Fe^۳+ quadrupole doublets, and ۳) the high-energy lines of octahedral Fe^۲+ quadrupole doublets. None of these spectra shows a shoulder at about +۰.۴ mm/s corresponding to high energy-lines of quadrupole doublets of Fe^۳+ in tetrahedral sites.

In their study of biotite compositions from granitic rocks of the South Mountain batholith of the Canadian Appalachians, MacKenzie and Clarke (۱۹۷۴) determined the Fe^۳+/Fe ratio of biotite by conventional wet-chemical methods and obtained values ranging from ۰.۰۶ to ۰.۳۷ for the ۱۸ specimens. The spread of Fe^۳+/Fe values obtained by Mِssbauer spectroscopy, from ۰.۰۵ to ۰.۲۳, including several specimens of the same batholith is considerably smaller. This reflects the poor precision of conventional wet-chemical determinations as performed in most laboratories. Mِssbauer spectroscopy is far more precise than most commonly-performed oxidimetric wet-chemical methods. In other words, the wet-chemical methods appear to overestimate ferric iron contents, probably because of oxidation of Fe^۲+ during the acid decomposition.