Significant contribution of seamounts to the oceanic rare earth elements budget

The rare earth elements (REEs) are a crucial resource and frequently used as proxies for reconstructing paleomarine environmental conditions. However, many details concerning the marine REE cycling, including relationship between benthic diffusion of REEs and seamounts, remain unclear. Here we present REE and trace elements data of porewater and seawater from the seamounts area and abyssal plain, respectively. Our results evidence that dissolved porewater REE, Mn and Al in sediments near seamount are much higher than those at abyssal plain, which lead to a substantial benthic source of REE to ocean at regions with seamounts. The REE enrichment processes in porewater at uneven seafloor are mainly based on re-suspension associated with the strong currents and/ or partial dissolution of detrital from seamounts. We suspect this process to occur in other world regions with seamounts and infer that these sediments can account for a significant contributor to the oceanic REE budget.

稀土元素（Rare Earth Elements, REEs）是一类关键战略资源，常被用作重建古海洋环境条件的代用指标。然而目前学界对海洋稀土元素循环的诸多细节仍不甚明晰，例如稀土元素的底栖扩散与海山之间的关联机制。本研究分别获取了海山区孔隙水与深海平原区海水的稀土元素与微量元素数据。研究结果证实，海山附近沉积物中的溶解态孔隙水稀土元素、锰（Mn）与铝（Al）含量远高于深海平原区，这表明海山周边区域存在显著的稀土元素从底栖环境向海洋释放的源汇过程。不平坦海底环境下孔隙水中的稀土元素富集过程，主要依托于强水流驱动的再悬浮作用，以及/或海山来源碎屑物质的部分溶解。我们推测该过程同样存在于全球其他海山分布区域，并推断这类沉积物可作为海洋稀土元素收支的重要贡献来源。