40Ar-39Ar analyses of a lumar meteorite (Yamato-86032) and a few LL3 and LL4 chondrites from Antarctica

^<40>Ar-^<39>Ar analyses were performed for a lunar meteorite (Yamato-86032), two LL3 (Y-790448,Allan Hills-764) and one LL4 (Y-74442) chondrites from Antarctica. The lunar meteorite Y-86032 shows a scattered ^<40>Ar-^<39>Ar age spectrum with anomalously high ages in the higher temperature fractions, indicating a shock effect on the analyzed sample. Among the three LL chondrites analyzed, the sample Y-790448 indicates a plateau ^<40>Ar-^<39>Ar age of 4521±28Ma in the lower temperature fractions (600-800℃). The other two LL chondrites show inverse staircase spectra in the higher temperature fractions. In the LL chondrite group, un-equilibrated chondrites seem to show older ^<40>Ar-^<39>Ar ages compared with equilibrated ones, which may be related to the differences in the thermal history of each portion of their parent body.