Fig. 3: Cross plot of Post-Archean Australian Shale (PAAS) normalized Ce anomaly (Ce/Ce*_PAAS) and heavy Rare Earth Element (REE) enrichment relative to light REE (HREE/LREE_PAAS) in the surface water (uppermost 3-5 m) of the South Pacific Gyre (170°E-90°W).

The REE data of the collected pumice, Hunga Tonga-Hunga Ha’apai (HTHH) lava⁴², PAAS, Australian dust^81,82, Ocean Island Basalt (OIB)⁴⁰ and coastal seawater of two representative volcanic islands in the Pacific Ocean, Papua New Guinea (PNG)²⁸ and Tahiti³⁸, are included. The calculations for Ce/Ce*_PAAS and HREE/LREE_PAAS are consistent with those in Fig. 2. Australian dust data contains data from various major dust sources from Australia, namely the Murray–Darling Basin⁸¹, Queensland, Paroo, Eyre Peninsula, and Channel Country⁸². The green arrow represents the change in REE patterns from OIB⁴⁰ to Tahitian coastal surface seawater (sample ID: t324)³⁸ and PNG coastal surface seawater near Sepik River mouth (station EUC-Fe-28)²⁸ due to seawater scavenging. The blue arrow indicates the change of REE patterns in surface seawater from eastern to western South Pacific Gyre as a result of volcanic material dissolution. The error bar for HTHH lava represents the standard deviation (SD) of five lava samples, while the error bars for surface water and pumice are derived from the propagation of measurement errors (2 SD) of each element. The dashed blue line and dotted blue lines represent the linear regression of Ce/Ce*_PAAS and HREE/LREE_PAAS in the surface water of the South Pacific Gyre (this study) and the 95% confidence interval of the regression, respectively.