Multiscale Characterization of a Deep-Sea Ferromanganese Nodule from the Clarion-Clipperton Zone

Ferromanganese nodules from the Clarion-Clipperton Zone (CCZ) located in the eastern Pacific Ocean between Hawaii and Mexico are enriched in a variety of critical metals. Understanding the spatial distribution of different metals, their partitioning between mineral phases, and pore-size distributions within the nodules can provide helpful insights into their formation mechanism. Here, we used a suite of techniques sensitive to the chemistry and texture of the nodule, including laser ablation–inductively coupled plasma–time-of-flight–mass spectrometry (LA-ICP-TOF-MS), Raman spectroscopy, scanning electron microscopy, and X-ray microtomography, to characterize key aspects of a single nodule from the Clarion-Clipperton Zone collected in the 1970s. We observed that parts of the nodules exhibited stratified zones enriched in cobalt (Co), nickel (Ni), copper (Cu), and rare earth elements (REEs) and found that Co, Ni, and Cu are spatially correlated with the distribution of the Mn-rich mineral phases. We also observed a stronger association of Ce and Co with other light REEs compared with heavier REEs. Within the porous rim of the nodule, micron-sized REE-enriched zones were detected, which are surrounded by Si- and Al-bearing phases and are not associated with phosphate phases. The results are consistent with alternating hydrogenetic and diagenetic growth conditions across part of the nodule and reveal heterogeneous REE distributions both within Mn-rich minerals and within distinct, likely inclusion-related phases.