Chemical leaching of rare earth elements from highly REY-rich mud

In previous studies of marine sediments, potential host minerals of REY have been identified as iron oxyhydroxides/oxides, manganese oxide, and apatite.Iron oxyhydroxides/oxides from hydrothermal fluids adsorb many elements, including REY, from surrounding seawater, and precipitate as metalliferous sediments (Ruhlin and Owen, 1985; German et al., 1991a, b;Rudnicki and Elderfield, 1992;Feely et al., 1994;Mills and Elderfield, 1995;German and Von Damm, 2007).Marine manganese/ferromanganese oxides such as Mn nodules and Mn crusts are also enriched in many metals of economic interest, including REY, and may represent a future resource for these elements (Hein et al., 2013).Biogenic apatite in pelagic sediment is known to be enriched in REY (Elderfield and Pagett, 1986; Toyoda et al., 1990;Toyoda and Tokonami, 1990).Recently, Kashiwabara et al. (2014) determined by high-energy Xray analysis that lanthanum (La) in REY-rich mud from piston core samples of sites 597 and 75 of the Deep Sea Drilling Project (DSDP) is concentrated in apatite.Kon et al. (2014) demonstrated that the total REY contents of apatite in REY-rich mud from near Minamitorishima Island averaged 21,000 ppm.