A Mesoproterozoic Iron Formation PNAS PLUS
A Mesoproterozoic iron formation PNAS PLUS Donald E. Canfielda,b,1, Shuichang Zhanga, Huajian Wanga, Xiaomei Wanga, Wenzhi Zhaoa, Jin Sua, Christian J. Bjerrumc, Emma R. Haxenc, and Emma U. Hammarlundb,d aResearch Institute of Petroleum Exploration and Development, China National Petroleum Corporation, 100083 Beijing, China; bInstitute of Biology and Nordcee, University of Southern Denmark, 5230 Odense M, Denmark; cDepartment of Geosciences and Natural Resource Management, Section of Geology, University of Copenhagen, 1350 Copenhagen, Denmark; and dTranslational Cancer Research, Lund University, 223 63 Lund, Sweden Contributed by Donald E. Canfield, February 21, 2018 (sent for review November 27, 2017; reviewed by Andreas Kappler and Kurt O. Konhauser) We describe a 1,400 million-year old (Ma) iron formation (IF) from Understanding the genesis of the Fe minerals in IFs is one step the Xiamaling Formation of the North China Craton. We estimate toward understanding the relationship between IFs and the this IF to have contained at least 520 gigatons of authigenic Fe, chemical and biological environment in which they formed. For comparable in size to many IFs of the Paleoproterozoic Era (2,500– example, the high Fe oxide content of many IFs (e.g., refs. 32, 34, 1,600 Ma). Therefore, substantial IFs formed in the time window and 35) is commonly explained by a reaction between oxygen and between 1,800 and 800 Ma, where they are generally believed to Fe(II) in the upper marine water column, with Fe(II) sourced have been absent. The Xiamaling IF is of exceptionally low thermal from the ocean depths. The oxygen could have come from ex- maturity, allowing the preservation of organic biomarkers and an change equilibrium with oxygen in the atmosphere or from ele- unprecedented view of iron-cycle dynamics during IF emplace- vated oxygen concentrations from cyanobacteria at the water- ment.
[Show full text]