Xiangli Wang, Frantz Ossa Ossa, Axel Hofmann, Andrea Agangi, Dora Paprika, Noah J. Planavsky
Xiangli Wang, Frantz Ossa Ossa, Axel Hofmann, Andrea Agangi, Dora Paprika, Noah J. Planavsky
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王祥利、Frantz Ossa Ossa、Axel Hofmann、Andrea Agangi、Dora Paprika、Noah J. Planavsky
DOI：
10.1016/j.epsl.2020.116583
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发表时间：
2020
影响因子：
5.3
通讯作者：
Uranium isotope evidence for Mesoarchean biological oxygen production in shallow marine and continental settings
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文献类型：
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作者：
中村守里也;Uranium isotope evidence for Mesoarchean biological oxygen production in shallow marine and continental settings
大陆岩石的氧化风化作用是海洋中氧化还原敏感元素的主要来源。氧化风化开始的时间仍然有很大的争议。在这里，我们报告新的δ 238 U数据的自生组分保存完好的ca。南非Kaapvaal盆地Mozaan群和自治领群3.07-2.90 Ga海相和湖相页岩。海相页岩的δ 238 U auth值（相对于CRM 112 a为-0.71 ‰ ~-0.21 ‰）低于块状硅酸盐地球（BSE为-0.40 ‰ ~-0.17 ‰），而湖相页岩的δ 238 U auth值（-0.68 ‰ ~ 0.05‰）分散在BSE范围的上下。此外，浅海沉积的海相页岩的δ 238 U auth值明显低于深海沉积的页岩。我们认为，U（VI）被吸附到铁锰氧化物在好氧浅水，然后穿梭到海底。湖相页岩中的U同位素分馏最好解释为沉积物-水界面以下的U（VI）还原为U（IV）。总之，这些观察支持的情况下，一个温和的氧化风化制度已建立在地球表面的3.0 Ga，铺平了道路的有氧代谢在大陆和浅海环境的开始。
Oxidative weathering of continental rocks is the major source of redox-sensitive elements to the ocean. The timing for the initiation of oxidative weathering remains strongly debated. Here we report new δ 238 U data for the authigenic component of well-preserved ca. 3.07–2.90 Ga marine and lacustrine shales from the Mozaan and Dominion groups of the Kaapvaal Craton, South Africa. The δ 238 U auth values in marine shales (− 0.71‰ to− 0.21‰ relative to CRM 112a) are lower than the bulk silicate Earth (BSE,− 0.40‰ to− 0.17‰), while those of lacustrine shales (− 0.68‰ to 0.05‰) scatter above and below the BSE range. In addition, the δ 238 U auth values of marine shales deposited in shallow seawater are significantly lower than those of the shales deposited in deep seawater. We propose that U (VI) was adsorbed onto Fe-Mn oxides in oxic shallow water and then shuttled to the seafloor. The U isotope fractionations in lacustrine shales are best explained by reduction of U (VI) to U (IV) below the sediment-water interface. Together, these observations bolster the case that a mildly oxidative weathering regime had been established at the Earth's surface by∼ 3.0 Ga, paving the way to the onset of aerobic metabolism in both continental and shallow marine environments.