Potassium Release from Micas and Characterization of the Alteration Products

Abstract

Abstract Interlayer K from two biotites of different origin was extracted with octadecylammonium chloride (ODA) and sodium chloride/sodium tetraphenylboron (STB) before and after oxidation with saturated bromine water (Br 2 ). Potassium release, Fe oxidation and Fe ejection from octahedra were measured. With ODA and STB the untreated biotites released between 40 and 90% of initial interlayer K, the muscovite less than 5%. After Br 2 treatment, substantially less K was extracted from both biotites. Suppression of K release was caused by the formation of octahedral vacancies formerly occupied by Fe. The extent of Fe ejection was not proportional to the extent of octahedral Fe oxidation. During Br 2 treatment, the biotites transformed into hydrobiotite. The hydrobiotite sample, high in Fe ejection during preceding Br 2 treatment, strongly resisted subsequent K extraction with STB, whereas the sample with minor Fe ejection transformed to vermiculite. Octadecylammonium chloride extracts K more effectively than STB from biotites intermediate between trioctahedral and dioctahedral structure and is considered to be suitable for the distinction between biotite K and muscovite K.