Crustal faulting drives biological redox cycling in the deep subsurface
- Xiao Wu
- Jianxi Zhu
- Hongmei Yang
- Yiping Yang
- Xiaoju Lin
- Xiaoliang Liang
- Mang Lin
- Barbara Sherwood Lollar
- Kurt O. Konhauser
- Hongping He
2025-07-18
In the deep biosphere, where surface-derived substrates are depleted, microbial communities rely on redox pairs generated through water-rock reactions to sustain metabolism. A notable example of this is the production of hydrogen gas (H 2 ) and oxidants from rock fracturing. However, the potential interactions between these initial redox pairs and a key subsurface element—iron (Fe)—remain underexplored. Here, we simulated radical-induced water splitting to investigate the formation and evolution of redox gradients. Our results show that in the presence of Fe, ferrous iron (Fe 2+ ) was marginally oxidized to ferric iron (Fe 3+ ) by low concentrations of oxidants, whereas Fe 3+ was efficiently reduced back to Fe 2+ by reactive hydrogen atoms (•H). We propose that crustal faulting can generate various redox pairs and drive Fe redox cycling, thereby providing a sustained energy source for subsurface life on Earth and potentially on other planetary bodies.