Understanding the rare earths distribution of Geochemistry in Clarion-Clipperton Zone Polymetallic Nodules at the nanoscale

Polymetallic nodules and hardgrounds, spread across vast abyssal plains, rich in Fe, Mn, Ni, Co, Cu, and REE and yttrium (REY), result from metal precipitation in the ocean due to erosion or hydrothermal emissions. Clarion-Clipperton Zone's polymetallic nodules boast concentrations of up to 2800 ppm REY, making them promising alternative sources for rare earth supply. However, uncertainties persist regarding REY enrichment mechanisms resulting in strong variations in Ce anomalies. Biogenic fluorapatite and Fe-Mn oxy-hydroxides are acknowledged Ce scavengers, yet their enrichment mechanisms remain under-explained. These experiments will pioneer μXRF and μXANES measurements, illuminating the distribution of Ce3+ and Ce4+ in Clarion-Clipperton polymetallic nodules. Furthermore, the acquired data will serve as a proxy to subsequently investigate and comprehend the mechanisms underlying the accumulation of Ce and REY in polymetallic nodules and hardgrounds found in Spanish waters.