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

• Main Authors: Hirokazu Fujimaki, Ken-ichi Ishikawa, Ken-ichiro Aoki
• Format: Report
• Language: English
• Published: Institute of Mineralogy, Petrology, and Economic Geology, TohokuUniversity 1992
• Subjects: The ''Y''; Yamato; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4585; http://id.nii.ac.jp/1291/00004585/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4585&item_no=1&attribute_id=18&file_no=1

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.