Iron Isotopes and their Application in the Evolution of Ancient Oceans

<p indent="0mm">Iron is a redox-sensitive element with multiple valence states, and its forms and isotopes are often used as environmental markers, particularly significant in indicating conditions in both modern and ancient marine environments. This paper summarizes the isotopic composition and fractionation mechanisms of iron in modern and ancient marine environments and reviews the genesis of early iron-bearing minerals to support the view that anaerobic oxidation processes existed in the early Archean. Anaerobic oxidation processes led to the oxidation of part of the dissolved iron in the ocean, which resulted in the enrichment of light iron isotopes in dissolved iron and indirectly contributed to the formation of banded iron formations (BIFs). Studying the genesis of iron-bearing minerals in ancient oceans is extremely challenging due to the difficulty in reproducing the chemical and physical conditions of ancient marine environments in modern settings. The advancement of isotopic techniques has enabled the measurement of iron isotopes in low concentrations, allowing iron isotopes and their fractionation to trace the behavior of iron in ancient oceans and to indicate the marine environment at that time. Therefore, modern research needs to combine laboratory simulations and modern Archean-like environments to resolve the mechanisms of iron isotope fractionation in ancient oceans. Additionally, the use of multi-isotope techniques of other elements to explore the chemical composition and genesis of iron-bearing minerals in ancient oceans is of great significance for the exploration of mineral resources and the study of the life origins.