U同位素在重建古海洋氧化还原环境中的应用
摘要
U isotope carriers undergo significant fractionation during sedimentation and diagenesis, often leading to misinterpretations of paleoocean redox conditions.This study systematically reviews the fractionation mechanisms of U isotopes, detailing their behavior during the sedimentation and diagenesis of carbonates, black shales, and ferromanganese crusts.It also proposes characteristics of ideal carriers and techniques to mitigate diagenetic effects.Overall, U isotope fractionation mechanisms are diverse, influenced by factors such as reaction rates, electron flux, and ionic strength.Sedimentation and diagenesis in carbonates and black shales typically result in heavier isotope compositions, while ferromanganese crusts exhibit fractionation in the opposite direction.The extent of fractionation is controlled by depositional environments and lithological composition.In practical applications, marine carbonates with low diagenetic alteration and primarily aragonitic mineralogy are recommended.Advanced techniques, such as ion-exchange chromatography, should be employed to accurately reconstruct the redox conditions of paleooceans.