School of Oceanography, University of Washington, Seattle, WA, 98195, USA.
Department of Earth and Space Sciences, University of Washington, Seattle, WA, 98195, USA.
Nat Commun. 2019 Sep 25;10(1):4371. doi: 10.1038/s41467-019-12322-2.
The oceanic magnesium cycle is largely controlled by continental weathering and marine authigenic mineral formation, which are intimately linked to long-term climate. Uncertainties in the magnesium cycle propagate into other chemical budgets, and into interpretations of paleo-oceanographic reconstructions of seawater δMg and Mg/Ca ratios. Here, we produce a detailed global map of the flux of dissolved magnesium from the ocean into deeper marine sediments (greater than ∼1 meter below seafloor), and quantify the global flux and associated isotopic fractionation. We find that this flux accounts for 15-20% of the output of magnesium from the ocean, with a flux-weighted fractionation factor of ∼0.9994 acting to increase the magnesium isotopic ratio in the ocean. Our analysis provides the best constraints to date on the sources and sinks that define the oceanic magnesium cycle, including new constraints on the output flux of magnesium and isotopic fractionation during low-temperature ridge flank hydrothermal circulation.
海洋镁循环在很大程度上受大陆风化和海洋自生矿物形成的控制，而这些过程与长期气候密切相关。镁循环中的不确定性会传递到其他化学预算中，并影响对古海洋重建海水 δMg 和 Mg/Ca 比值的解释。在这里，我们制作了一幅详细的全球地图，展示了从海洋进入深海沉积物（海底以下大于约 1 米）的溶解镁通量，并量化了全球通量及其相关的同位素分馏。我们发现，该通量占海洋镁输出的 15-20%，具有约 0.9994 的通量加权分馏因子，可增加海洋中的镁同位素比值。我们的分析为定义海洋镁循环的源汇提供了迄今为止最好的约束条件，包括对低温脊侧翼热液循环过程中镁输出通量和同位素分馏的新约束条件。
