关键词: 海洋氧化, O-Fe-C-S-Ba循环, 保守元素, Ba同位素, 早期生命

Abstract: The late Neoproterozoic witnessed an increase in the atmospheric and oceanic oxygen levels, namely the Neoproterozoic Oxygenation Event (NOE), likely resulting in the naissance and radiation of metazoans and the establishment of complex ecosystem. Oceanic oxygenation could change oceanic chemistry, such as species and valence states of Fe, C, and S, and the biogeochemical cycle of Ba in the ocean is strongly controlled by the S species and sulfate concentration. This review introduces how the NOE changed the oceanic Ba cycle: (1) Before the NOE, the oceanic sulfate concentration was low and the oceanic Ba cycle was conservative; (2) during the NOE, the oceanic sulfate increase led to excess Ba enrichments in sediments and formation of massive barite deposits; and (3) after the NOE, the ocean kept over-saturated relative to barite until the terminal Paleozoic and the Ba cycle was controlled by biological productivity afterwards. In addition, this review suggests to use Ba isotope system to reconstruct the oceanic Ba concentration, and indirectly to estimate the oceanic sulfate concentration (oxygenation extent) during the late Neoproterozoic.

Key words: oceanic oxygenation, O-Fe-C-S-Ba cycle, conservative element, Ba isotopes, early life