A new mechanism for magnetite formation in loess
Yifan Hua1, Guiping Ren2, Hua Li3
1School of Earth Sciences, Lanzhou University, Lanzhou 730000, China; State Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; Ministry of Education Key Laboratory of Western China's Environmental Systems, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100029, China.
None:
A comprehensive understanding of magnetic mineral transformation pathways in sediments is critical for reconstructing past climates and geomagnetic field variations. Conventional models of magnetic mineral transformation in well-aerated soil environments agree that magnetite undergoes partial oxidation into maghemite and/or hematite, manifesting as the occurrence of maghemite/hematite along magnetite edges. We report an inverse structure-magnetite growth on hematite edges-in Chinese loess. We replicated this distinctive configuration by reacting hematite with Pseudomonas aeruginosa, a ubiquitous aerobe capable of reducing Fe(III). This reaction is orders of magnitude faster than traditional loess magnetic enhancement pathways, offering a new aerobic pathway of loess magnetic enhancement and new opportunities to reconstruct past geomagnetic field variations at high resolution. The unique magnetite-hematite association is a candidate biosignature, potentially applicable to some hematite-rich Martian sediments.
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