资源环境科技发展态势分析平台

The oceanic magnesium budget is important to our understanding of Earth鈥檚 carbon cycle, because similar processes control both (e.g., weathering, volcanism, and carbonate precipitation). However, dolomite sedimentation and low-temperature hydrothermal circulation remain enigmatic oceanic Mg sinks. In recent years, magnesium isotopes (未²⁶Mg) have provided new constraints on the Mg cycle, but the lack of data for the low-temperature hydrothermal isotope fractionation has hindered this approach. Here we present new 未²⁶Mg data for low-temperature hydrothermal fluids, demonstrating preferential ²⁶Mg incorporation into the oceanic crust, on average by 蔚_solid-fluid鈥夆増鈥?.6鈥? These new data, along with the constant seawater 未²⁶Mg over the past ~20鈥塎yr, require a significant dolomitic sink (estimated to be 1.5鈥?.9鈥塗mol鈥墆r^鈭?; 40鈥?0% of the oceanic Mg outputs). This estimate argues strongly against the conventional view that dolomite formation has been negligible in the Neogene and points to the existence of significant hidden dolomite formation.