Minerals Report - International Seabed Authority

metals - nickel, cobalt, manganese, copper, zinc, lead, silver and gold. He
demonstrated that most prices had declined since 1980. He attributed the
high cobalt prices in the 1980s to the Zaire disturbances and the increase in
manganese prices after 1974 to the use of ferrosilicon manganese alloys that
replaced ferromanganese alloys. He showed that since 1980 prices of lead,
zinc, copper, manganese, nickel and even gold have shown a general decrease
in trend while silver prices were relatively constant and cobalt prices on
variable.
On technology, he stated that much work has been done for nodule
deposits, and several engineering studies have been carried out for cobalt
crusts. However, in respect of polymetallic sulphides, mining technology was
an open question. The inhibiting parameters for exploitation he noted was
that in the case of polymetallic nodules, deposit depth is around 5,000 metres
as compared with 1,000 metres for cobalt crusts and around 2,500 metres for
sulphides.
On the morphology of deposits, he noted that nodules deposits are a
two-dimensional system, cobalt crusts is more or less a two-dimensional
system but with a factor of thickness that has to be taken into account, while
in the case of sulphides, it is typically a three-dimensional system. On the
range of tonnage, he further noted that for nodule deposits the required size is
in the range of 50 million tonnes whereas cobalt crusts would be around 10
times less and sulphides could be in the range of 8.5 to 10 times less than the
required size for a nodule deposit.
In respect of the technology for lifting the nodules, Dr. Lenoble stated
that the French study demonstrated that the system would be a self-propelled
dredge, crawling on the seafloor with a collector that crushes the nodules and
allows the material to be introduced into a long flexible hose connected to a
rigid pipe. The crushed nodules would then be lifted to the semi-submersible
surface platform, in rigid steel pipes by airlifts or hydraulic lifts. Pumping
them through a flexible hose would carry out the transfer of the nodules from
the platform to the ore carrier. In respect of cobalt crusts, mining would be by
some similar kind of dredge cutter modified in such a way that the first layer
of the crust could be scraped out. The lifting could be by a hydraulic system.
INTERNATIONAL SEABED AUTHORITY 44