40Ar-39Ar Ages of L and LL Chondrites from Allan Hills, Antarctica: ALHA77015,77214 AND 77304
^<40>(Ar)-^<39>(Ar) ages have been determined for three chondrites (ALHA77015,77214,77304) from Allan Hills, Antarctica. Although younger ages have been observed at lower and higher temperatures for ALHA77015 (L3), the intermediate plateau-like age indicates a value of 4514±48 (1σ) Ma, t...
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| Format: | Report |
| Language: | English |
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Geophysical Institute, Faculty of Science, University of Tokyo
1980
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| Online Access: | https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1098 http://id.nii.ac.jp/1291/00001098/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1098&item_no=1&attribute_id=18&file_no=1 |
| Summary: | ^<40>(Ar)-^<39>(Ar) ages have been determined for three chondrites (ALHA77015,77214,77304) from Allan Hills, Antarctica. Although younger ages have been observed at lower and higher temperatures for ALHA77015 (L3), the intermediate plateau-like age indicates a value of 4514±48 (1σ) Ma, though the plateau range is relatively narrow about 27% of the total ^<39>(Ar). ALHA77304 (LL3) shows a typical plateau age of 4503±52 Ma at higher temperatures, covering about 46% of the total ^<39>(Ar). Seriously weathered ALHA77214 (L or LL) exhibits a typical stair-case age pattern, increasing from about 1600 Ma up to about 4450 Ma. When coupled with reported data on other chondrites, there may be a rough correlation between the ^<40>(Ar)-^<39>(Ar) age and the degree of metamorphism defined from their petrologic type for unshocked L chondrites. However, such a trend is not clear for H and LL chondrites and a more systematic survey is required to settle the problem. |
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