Rb-Sr features of the impact-melted LL-chondrites from Antarctica:Yamato-790723 and Yamato-790528

概要

論文の詳細を見る
Rubidium and strontium abundances as well as Sr isotopic compositions were analyzed for the impact-melted meteorites (LL-chondrite : Yamato-790723 and -790528) from Antarctica to clarify their Rb-Sr features and to date the impact events. The samples were separated according to the magnetic property. The less magnetic and glass-rich portions of Y-790723 approximate an isochron of 1.27±0.19 Ga. The obtained age should indicate the impact event. The magnetic portions and fine-grained one largely deviate from the isochron. Y-790528 is rather depleted in K_2O and Rb, but not in Na_2O; this may be due to scarcity of the K-rich fragments. The ^<87>Sr/^<86>Sr ratios of the separated portions from Y-790528 are low and less variable. The five less magnetic portions of the Y-790528 chondrite seem to form the isochron of 4.36±0.76Ga as the time of the impact event. The large errors may have derived from local reset of the Rb-Sr chronometer and incomplete separation into the portions.
国立極地研究所の論文