Minerals Report - International Seabed Authority

Dr. Corbett gave a brief account of the discovery of diamonds offshore
Namibia, and the regional setting for diamonds in the basins of the Namib
Desert. He explained that the Orange River is largely responsible for the
introduction of diamond in the southwest continental margins of Namibia.
His presentation covered the complex eco-system on the continental shelf of
Namibia that is influenced by the Benguela current and the Orange River. He
explained that the kimberlites were transported by the Orange River onto the
continental shelves. The river system has been in existence for 65-80 million
years transporting kimberlites onto the West Coast. He gave a brief account
of geological features including the Gondwana break-up and the formation of
the Atlantic Ocean. He also elaborated on the physical characteristics of the
diamond deposits and exploration and evaluation techniques used by De
Beers. Dr. Corbett informed participants that De Beers Marine operates two
vessels with sampling capabilities. One of the vessels, the Douglas Bay, is
equipped with a “mega drill” and the second vessel, the Coral Sea, is
equipped with a large-bore “decadrill” system. In addition, De Beers has
operated the Jago submersible from the vessel Zealous for environmental
studies.
Providing an overview of deep-water marine systems, Dr. Corbett
stated that the recovery of diamonds is a very sensitive and complex process.
Once diamonds are recovered by the drilling system, they are not touched by
human hands in the entire processing operation. Diamond recovery, he
further stated, is a non-chemical process, the low density material is
discharged overboard and returned to the seabed while the high density
material is dried prior to X-ray screening to separate the diamonds from nonfluorescent
materials. Dr. Corbett pointed out that extraction is achieved
utilizing dense media separators that are passed through an X-ray sorting
system that identifies the diamonds.
He stated that the overall philosophy of De Beers is to maximize the
time utilized in the mining operations. The objective is to carry out safe
operations for periods of two years or more on ship-based activities, giving
time for scheduled in-port maintenance. Refueling is normally done at sea to
reduce time off station. He stated that the vessel Debmar Pacific with 1027
days holds the record for a vessel remaining at sea.
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