Unraveling the Enrichment Mechanisms of Rare Earth Elements in Deep‐Sea Sediments: An Environmental Magnetic Perspective

Abstract Deep‐sea rare earth elements and yttrium (REY)‐rich sediments have attracted considerable attention since their discovery in 2011. However, the environmental factors controlling REY enrichment remain poorly understood, largely because paleoceanographic proxies are absent in pelagic clays. This study focused on two sediment cores with an ultra‐enrichment layer of REY (UELR) from the western and southeastern Pacific. Detailed rock magnetic and transmission electron microscope analyses revealed high magnetofossil abundance in the UELR. It is proposed that strong bottom currents triggered intense upwelling, enhancing primary productivity. This, in turn, stimulated both fish and magnetotactic bacteria reproduction, making the strong coupling between magnetofossils and phosphate, mainly from fish bones and teeth, which efficiently absorbed substantial REYs from seawater. Moreover, magnetic parameters related to eolian dust can also indicate REY composition and the enrichment environment. Therefore, environmental magnetism holds significant potential for investigating the mechanisms of deep‐sea REY enrichment.