Distributions of alkali, alkaline earth and rare earth elements in component minerals of chondrites

Abstract

The distribution of alkali, alkaline earth and rare earth elements was studied in ordinary chondrites and an enstatite chondrite by means of wet chemical fractionation methods of powdered meteorite samples. An ordinary chondrite, Bruderheim, and a Type I enstatite chondrite, Abee, were studied most extensively. A stepwise fractional dissolution scheme was used to decompose the various main component minerals successively, using water or acetate buffer (pH 5.5), EDTA in an ammoniacal solution, bromine water, HCl, aqua regia and finally HF + HClO 4. The potential of fractional dissolution was critically examined from several points of view. In both types of meteorites, Li, Ba, and rare earths except for Eu were found in readily soluble phases. The behaviour of rare earth and alkaline earth elements in the Type I enstatite chondrite seems to be unique. These data have a bearing on the thermal histories of the chondrites.