| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2002: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
The main objective of this research project has been to develop our understandings on surface environment in early Earth by studying paleosols through the behaviors of trace elements and organic matter and through their relationship to biological activity in weathering process. Some of the results from our investigations have been presented at various national and international conferences, and also published in journal and bulletin. The following are brief summary of new findings :
1. For the 2.45 Ga Pronto paleosols on granite, Ontario, Canada which has been questioned if they are true in-situ soils, our investigation, shows that (1) the Pronto profile should be identified as a saprolith formed in situ rather than paleosol, (2) secondary REE phosphate in sericite aggregate, which is a weathering product after primary REE phosphate as apatite, closely relates to iron oxide in sericite aggregate, (3) the comparison with the studies on modern weathering of granite, especially that of apatite would clear the relationship among the behaviors of phosphorus, iron, lanthanide and biological activities during weathering around 2.5 Ga, as microbial controls on phosphate and lanthanide distributions during modern weathering of granite was pointed out (Taunton et al., 2000).
2. The chlorite and sericite zones in 2.77 Ga Mt. Roe basalt near Whim Creek, Pilbara, Western Australia, have been thought as paleosols formed under an anoxic atmosphere. Our study suggest the different explanation that (1) the alteration zones were formed by hydrothermal activity which occurred concurrently with volcanic activity, (2) as the stable isotope ratios of organic carbon extracted from the alteration zones indicate the inhabitation of methanogen, the relationship between the methane bearing reducing hydrothermal solution and methanogen would be challenging research issue for the near-term.
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