Geophysical and Geochemical Environment of Archean Biosphere

点击翻译按钮获取中文摘要

The research was driven using the cores from the Pilbara craton in Western Australia by ABDP (Archean Biosphere Drilling Project), to understand the evolution of Archean life and geochemical environment including geomagnetism. Paleomagnetic study suggests that the geomagnetic dynamo might behave at about 3.5Ga, and that the free oxygen level was very low and iron microbes oxidized ferrous to ferric, bereaving the charge of dissolved hydrion. The carbon from organisms in ferruginous Marble Bar Chert might be depleted during diagenesis. On the other hand, the high free oxygen level of 2.77Ga, is suggested from subsistence of cyanobacteria and sulfate reduction bacteria, but the level was not enough to oxidized magnetite to ferric compounds. The behavior of organic carbon and its isotopic ratio is not known yet, and should be expected in future study.