4.3 He Yongsheng

Oxygenation of the paleo-atmosphere by deep carbon freezing of recycled carbonates

Yongsheng He1,*, Xunan Meng1, Shan Ke1, Hongjie Wu1, Chuanwei Zhu1, Fang-Zhen Teng2, Jochen Hoefs3, Jian Huang4, Wei Yang5, Lijuan Xu1, Zhen-hui Hou4, Zhong-Yuan Ren6, Shuguang Li1, 4, *

1, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China.

2, Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA.

3, Department of Geosciences, University of Göttingen, Goldschmidtstr. 1, Göttingen 37077, Germany.

4, CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.

5, State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China.

6, Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.

*Corresponding author: Yongsheng He (heys@cugb.edu.cn);

               Shuguang Li (lsg@ustc.edu.cn)

The evolution of atmospheric oxygen is important for an understanding of ocean chemistry, life evolution and crust-mantle interactions. However, it remains debated how the atmosphere was oxygenated; in particular, whether or not the solid Earth has contributed to the rise of atmospheric O2. Here, we identified an enriched δ56Fe (up to 0.29) melt component in Cenozoic basalts from eastern China, which originates from partial melting of a carbonated peridotitic source with Fe3+/ΣFe ≥ 0.15. Enrichment of Fe3+/ΣFe ratios in the mantle source was coupled with the reduction of recycled carbonates to diamonds in the deep mantle. A Fe3+ enriched mantle being preferentially extracted to Earth’s surface via partial melting may provide an alternative / complementary mechanism to explain oxygenation of the atmosphere. The eruption of oxidizing basalts will affect iron oxide buffer promoting atmospheric oxygen production.