Hydrodynamic control over shallow ferromanganese crust deposits in the West Rio Grande Rise

The West Rio Grande Rise (WRGR), an oceanic elevation in the Southwestern Atlantic, hosts extensive ferromanganese crust deposits that are rich in critical metals and rare earth elements. These crusts are formed under specific environmental conditions, influenced by factors such as nutrients, oxygen levels, biological and hydrodynamic processes. This study investigates the influence of intense hydrodynamic processes occurring between 5001500 m on the exposure of ferromanganese crusts in the shallower portion of the WRGR. The hydrodynamics in this region is characterized by an intense anticyclonic mean current spanning between 5001500 m, that is generated by nonlinear interactions between strong tidal currents and the southern branch of the South Equatorial Current with the topography. By integrating results from two complementary approaches, a statistical classification model and a coupled hydrodynamicsediment transport model, we test the hypothesis that near-seabed currents play a key role in controlling crust exposure and preservation in the shallower region of the WRGR (5001500 m). Statistical analysis identifies key environmental factors such as conservative temperature, absolute salinity, mean flow speed, and tidal amplitude distinguishing ferromanganese crust from carbonate deposits. Hydrodynamic modeling reveals that strong near-seabed currents inhibit sediment deposition over crust areas, maintaining their exposure. Up to 80% of ferromanganese crust areas can be explained by these hydrodynamic patterns. These findings underscore the role of hydrodynamics in maintaining ferromanganese crust exposure and offer important insight into the modern oceanic processes that govern where crusts remain exposed.