Investigation of the weathering effect on the 40Ar-39Ar ages of Antarctic meteorites

• Main Author: Kaneoka, Ichiro
• Language: English
• Published: 1983
• Subjects: Antarctic; Antarc*; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/record/1565/files/KJ00000012198.pdf; https://nipr.repo.nii.ac.jp/records/1565

P(論文) In order to examine the weathering effect on ^<40>(Ar)-^<39>(Ar) ages of Antarctic meteorites, the ^<40>(Ar)-^<39>(Ar) age patterns were compared for the outer and inner portions of two Antarctic meteorites (ALH-761,ALH-77288). The results indicate that the oxidized outer portions show anomalously old ^<40>(Ar)-^<39>(Ar) ages which exceed 4600Ma in the intermediate temperature fractions of around 800-1000℃. These old ^<40>(Ar)-^<39>(Ar) ages are accompanied by the increase of ^<36>(Ar), which is regarded to be mostly of atmospheric ^<36>(Ar). This might be explained by the incorporation of atmospheric Ar in hematite which was produced from goethite during neutron irradiation. The inner relatively fresh portions show the following plateau ages : ALH-761,64,4487±50Ma; ALH-77288,63,4497±40Ma. departmental bulletin paper