Minerals Report - International Seabed Authority

3.5. Comparison of the deep-sea mineral deposits
The mean values of the "in-situ" ores are very similar, when discarding
the illusive case of "sulphides (rich)".
The costs of mining and processing can make the difference.
However, mining at depths of 1, 000 m (Co-crusts) to 2 500 m (massive
sulphides) instead of 5, 000 m (nodules) will not necessarily divide the cost of
operations by 2 or 5. A scale effect could be in favour of nodule mining,
which can envisage a higher annual capacity than the other two can. The
energy consumption will be more important for scraping or excavating crusts
and massive sulphides than for harvesting the nodules.
The risk of failure of the mining system is the main concern of the
aspirant deep-sea miner. The more complex the geometry of the deposit, the
more elaborate the bottom collector will have to be. The more sophisticated
the bottom equipment, the less reliable it might be. On that subject, the
different deposits can be classified from relatively easy (nodules) to
moderately difficult (Co-crusts) and more difficult (sulphides) to mine.
The protection of the natural environment is another major concern of
the future deep-sea miners. Most of the massive sulphides deposits have been
discovered in areas of intense biological activity linked to hydrothermal vents.
It seems impossible to admit that mining could be carried out in these areas. It
will destroy most of this very active life. Massive sulphides mining would be
authorized only in areas where biologic activity is extinct. Those areas are
more difficult to find. Currently, exploration is guided by the topography of
ridges, and the temperature and geochemical anomalies of seawater.
However, some "fossil" deposits have been already discovered. They
constitute the actual targets of future mining operations.
For the time being, no commercial operations can be envisaged
because either the knowledge of the deposit is too poor, the technology not
available, or the metal prices too low. For some deposits, the three preceding
conditions are unfortunately combined.
INTERNATIONAL SEABED AUTHORITY 447