REE, Rb, Sr and Ba Abundances in Yamato (j), (k) and (m) Meteorites

Abstract

Yamato (j), (k) and (m) meteorites were analyzed for rare-earth elements (REE), Rb, Sr and Ba. The Leedey-normalized REE pattern of (k) shows a small discontinuity between Gd and Dy. However, the REE pattern of (m) normalized by (k) exhibits a smooth fractionation with no Gd-Dy gap, except for Eu which is to be dealt with separately on account of its possible divalent state. The smooth fractionation between (m) and (k) suggests a genetically close association in origin. Yamato (j) was investigated for two fractions, j_1 and j_2. The REE abundances in the former are not so smooth as that of the Leedey chondrite, and are lower than in j_2. Meanwhile, the internal abundance ratio pattern of j_2 against j_1 shows a quite smooth one, which can be explained in terms of the melting and subsequent solidification process, the mixing of the products mainly representing the residual melts, and the generally common partitioning function pertaining to the process.