海洋铪同位素演化及其对大陆物源与洋流变化的启示

尽管海洋铪(Hf)同位素早在20世纪80年代就有报道,但直到最近几年随着分析测试技术的发展,它作为示踪陆源风化输入和洋流循环改变的新指标才越来越受到关注。综述了全球大洋Hf同位素现代分布以及新生代演化特点,其中最重要的现象是Nd-Hf同位素投影图上海水与岩石具有不一致的趋势线。在这些观测资料的基础上着重讨论了围绕海洋Hf同位素物源争议的一系列问题,阐述了海洋热液系统、大陆差异风化、洋岛陆架沉积物溶解等对海洋Hf的贡献以及Hf,Nd存留时间不一致等对海洋Hf同位素的影响等。弄清Hf的海洋地球化学行为,对深入认识海洋Hf的循环以及古海洋演化具有着重要的意义。

Marine hafnium isotopic evolution and its implications for continental sources and ocean circulation changes

Although marine Hf isotope have been reported since the 1980s,they are not paid much attention to as a new proxy in tracing continental weathering and oceanic circulation until recently with the developments of analytical technology.The modern distribution of global seawater Hf isotopes and their Cenozoic evolution are reviewed.The most important phenomenon is that the seawater Nd-Hf isotopic compositions display a well-defined correlation,which clearly offsets from the terrestrial array.Based on these observations,the controversial issues on the sources of marine Hf isotopes are discussed,including the contributions of marine hydrothermal systems,continental incongruent weathering,dissolution of shelf and oceanic island sediments,and effect of different resident times between Hf and Nd.Clarifying the geochemical behavior of marine Hf is crucially important for better understanding the marine Hf cycling and paleoceanic evolution.