Potential influence of sulphur bacteria on Palaeoproterozoic phosphogenesis

• Published in: Nature Geoscience
• Main Authors: Lepland, Aivo, Joosu, Lauri, Kirsimäe, Kalle, Prave, Anthony R., Romashkin, Alexander E., Črne, Alenka E., Martin, Adam P., Fallick, Anthony E., Somelar, Peeter, Üpraus, Kärt, Mänd, Kaarel, Roberts, Nick M. W., van Zuilen, Mark A., Wirth, Richard, Schreiber, Anja
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDU]Sciences of the Universe [physics]; Northwest Russia
• Online Access: https://insu.hal.science/insu-03581154; https://doi.org/10.1038/ngeo2005

International audience All known forms of life require phosphorus, and biological processes strongly influence the global phosphorus cycle. Although the record of life on Earth extends back to 3.8billion years ago and the advent of biological phosphate processing can be tracked to at least 3.5billion years ago, the earliest known P-rich deposits appeared only 2billion years ago. The onset of P deposition has been attributed to the rise of atmospheric oxygen 2.4-2.3billion years ago and the related profound biogeochemical shifts, which increased the riverine input of phosphate to the ocean and boosted biological productivity and phosphogenesis. However, the P-rich deposits post-date the rise of oxygen by about 300million years. Here we use microfabric, trace element and carbon isotope analyses to assess the environmental setting and redox conditions of the 2-billion-year-old P-rich deposits of the vent- or seep-influenced Zaonega Formation, northwest Russia. We identify phosphatized microorganism fossils that resemble modern methanotrophic archaea and sulphur-oxidizing bacteria, analogous to organisms found in modern seep settings and upwelling zones with a sharp redoxcline. We therefore propose that the P-rich deposits in the Zaonega Formation were formed by phosphogenesis mediated by sulphur bacteria, similar to modern sites, and by the precipitation of calcium phosphate minerals on microbial templates during early diagenesis.