南アフリカに分布するオンフェルワクト層群の珪質頁岩・チャート中の有機物

概要

論文の詳細を見る
Contents of various forms of carbon and nitrogen in siliceous shale and chert of the Onverwacht Group (Hooggenoeg F. and Theespruit F.), 3300-3500 Ma old, and elemental composition, graphitization degree and ^<13>C/^<12>C ratio of their kerogen have been determined. These rocks contain various quantity of organic carbon (1.84% for the siliceous shale and 0.27-0.43% for the chert), but practically do not contain insoluble nitrogen which consists of organic nitrogen in the kerogen structure and ammonium nitrogen in minerals. δ^<13>C values of their kerogens are -27.7‰ and -35.5‰ for the Hooggenoeg Formation and -17.0‰ and -15.9‰ for the Theespruit Formation. On the other hand, analytical results of carbon and nitrogen contents for the Gunflint chert, 1800-2100 Ma old, which were examined for reference in this study, show that the Gunflint chert contains 8.7ppm insoluble nitrogen in spite of the low organic carbon content (0.06%). The lack of insoluble nitrogen in the Onverwacht siliceous shale and chert is characteristic in comparison with the data of the Gunflint chert and the Phanerozoic siliceous shale and chert which have been determined in a previous study. Taking the δ^<13>C values of the kerogens into consideration, the lack of insoluble nitrogen in the Onverwacht siliceous shale and chert seem to be due to the difficulty of the nitrogen fixation into the kerogen structure (e. g. Simple chemical character of the early life caused the rapid elimination of the nitrogen from the sedimentary organic matter as ammonium ion, and the low rate of sedimentation in Archean time promoted the elimination of the nitrogen from the sediments).
地学団体研究会の論文
1988-01-25

南アフリカに分布するオンフェルワクト層群の珪質頁岩・チャート中の有機物

スポンサーリンク

概要

著者

関連論文

スポンサーリンク