REE characteristics of Yamato-82162 and -86720 meteorites and their inference to classification

概要

論文の詳細を見る
Abundances of REE, Ba, Sr, Rb, K, Mg, Ca and Fe were determined for Yamato-82162 and -86720 carbonaceous chondrites by mass spectrometric isotope dilution. The CI-normalized REE abundance patterns for Y-82162 are nearly flat (0.9-1.5×CI), but show small negative Ce anomalies. A small fraction of the chondrite shows a clear light/heavy REE fractionation. The REE abundance patterns of Y-86720 are also almost flat (1.4-1.9×CI) and show positive Eu anomalies. The degree of Eu anomaly seems to correlate with the absolute abundance of the REE. For the abundances of elements other than REE, Y-82162 shows enrichments of Fe and Mg and Y-86720 displays depletions of the relatively volatile elements K and Rb. From these results, the following conclusions are obtained : (1) Y-82162 may contain a high temperature component formed in the nebula. (2) Y-82162 is classified as a CI chondrite which has experienced thermal metamorphism. (3) Y-86720 is composed of a refractory-rich component and a refractory-poor component. (4) Y-86720 cannot be strictly classified into any group but is intermediate between CM and CO chondrites.
国立極地研究所の論文