Han Tao, Bao Huiming, Peng Yongbo, Lu Zhitong, Song Yunzhou
State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Nat Commun. 2025 May 30;16(1):5018. doi: 10.1038/s41467-025-60309-z.
The oxygen isotope composition of seawater (δO) is shaped by high- and low-temperature rock-water interactions, reflecting Earth system's dynamics and evolution. The history of δO remains debated due partly to post-depositional imprints to all current mineral proxies. The oxygen atoms in sulfate minerals are among the most inaccessible to later exchange but often not in isotope equilibrium with ambient water. However, the δO may reach a plateau or approach equilibrium with the δO as the corresponding δS increases during microbial sulfate reduction. Here we show 289 paired δO-δS values for sedimentary barite spanning six periods of the Phanerozoic Eon. The δO-δS trajectories point to variable equilibrium δO values for different periods. A ~ 4‰ lower δO value is evident before the Carboniferous than today if assuming the same formation temperature. Utilizing the barite δO-δS trajectory approach, we now have a robust proxy to advance the long-debated issue of seawater δO history.
海水的氧同位素组成（δO）受高温和低温岩石 - 水相互作用的影响，反映了地球系统的动力学和演化。δO的历史仍存在争议，部分原因是所有当前矿物代理指标都存在沉积后印记。硫酸盐矿物中的氧原子是后期交换最难触及的，但通常与周围水体不存在同位素平衡。然而，在微生物硫酸盐还原过程中，随着相应的δS增加，δO可能会达到一个平稳状态或与δO接近平衡。在这里，我们展示了显生宙六个时期沉积重晶石的289对δO - δS值。δO - δS轨迹表明不同时期的平衡δO值存在变化。如果假设形成温度相同，石炭纪之前的δO值明显比现在低约4‰。利用重晶石δO - δS轨迹方法，我们现在有了一个可靠的代理指标来推进长期存在争议的海水δO历史问题。
