Rare gases in a phlogopite nodule and a phlogopite-bearing peridotite in South African kimberlites |
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| Authors: | Ichiro Kaneoka Nobuo Takaoka Ken-Ichiro Aoki |
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| Institution: | Geophysical Institute, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo ,Japan;Department of Physics, Faculty of Science, Osaka University, Toyonaka-shi, Osaka ,Japan;Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Sendai ,Japan |
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| Abstract: | Rare gas isotopes in a phlogopite nodule and a phlogopite-bearing peridotite nodule in South African kimberlites were studied to examine the state of rare gases in the deep interior of the kimberlite region.Within the experimental error of 1 ～ 2%, rare gas isotopic compositions are atmospheric except for radiogenic4He and40Ar. No excess129Xe was observed.In phlogopite, Ne is more depleted, whereas the heavier rare gases are more enriched than the atmospheric rare gases relative to36Ar.Together with other data these results suggest that the state of rare gases in the upper mantle of the South African kimberlite region might have been changed from the typical primitive mantle by a process such as mixing of crustal materials. |
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