Sediment accumulations within the Red Sea central deeps have unique genesis and properties. We piece together
available information to understand their geological setting and formation history, and conduct an extensive
sediment characterization study to assess their geotechnical properties in order to anticipate engineering/mining
implications. The various sediment columns reflect slow-rate background sedimentation (biogenic and detrital
particles – Valdivia deep) and hydrothermal metalliferous sediments that nucleate and grow within the overlying
brine pools (primarily in the Atlantis II, as well as in the Wando deep, and to a lesser extent in Discovery deep).
All sediments are fine-grained silt and clay-size particles; smaller particles tend to have higher specific gravity
and define the metalliferous content. Hydrothermal sediments exhibit extreme properties when compared to
sediments worldwide: they have uncharacteristically large maximum void ratio and compressibility, and their
self-compaction is very different from background Red Sea sediments. Their unique self-compaction trends have
a strong effect on remote acoustic characterization and sampling, and must be carefully accounted for during
field studies and resource assessment. Three distinct properties of hydrothermal metalliferous sediments are
relevant for separation and enrichment: high specific surface area, high specific gravity, and ferromagnetic
signature. Small grains and low-density flocs have low terminal Stokes' velocities and their residency times may
be extended in convective stratified brine pools; this observation affects the environmental analysis of mining
operations and tailings disposal.
