Geophysical and Geochemical Environment of Archean Biosphere

这项研究是由ABDP（太古代生物圈钻探项目）使用西澳大利亚皮尔巴拉克拉通的岩心进行的，以了解太古代生命的演化和包括地磁在内的地球化学环境。古地磁研究表明，地磁发电机可能在3.5Ga左右表现，自由氧水平很低，铁微生物将亚铁氧化为三价铁，使溶解态铁离子失去电荷。含铁大理岩硅质岩中的生物碳在成岩过程中可能发生亏损。另一方面，2.77Ga的高游离氧水平表明蓝细菌和硫酸盐还原菌的生存，但该水平不足以将磁铁矿氧化成铁化合物。有机碳的行为及其同位素比值尚不清楚，应在未来的研究中进行展望。

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.