Deposition and termination of Neoproterozoic iron formations (NIFs): New insights from NIFs in China

Abstract

Over the past two decades, advancements in geochronological, sedimentary, and geochemical studies have considerably deepened our understanding of the links between the deposition of Neoproterozoic iron formations (NIFs) and major changes in Earth's surface environment. In China, extensive studies within this period have revealed that NIFs exhibit a wide range of fabrics, lithofacies, and geochemical properties, indicating their deposition occurred in a range of environments. Chinese NIFs can be categorized into four types based on lithofacies associations and depositional settings: (1) syn- and de-glacial NIFs that are associated with glacial deposits in glaciomarine or sub-ice environments; (2) inter-glacial NIFs associated with non-glaciogenic deposits in oceans that lacked sea ice during the Cryogenian; (3) volcanism-related NIFs found with volcanic rocks in extensional basins related to the break-up of the supercontinent Rodinia; and (4) non-glaciogenic and non-volcanogenic NIFs that are intercalated with shales and carbonates, and were likely deposited on the continental shelf. Accordingly, we propose a unified model that emphasizes multiple factors controlling the deposition of NIFs at the global scale. Furthermore, we propose that the termination of NIF deposition was probably related to rising oxygen levels on Earth's surface during the late Neoproterozoic.