Minerals Report - International Seabed Authority

that these seafloor massive sulphide deposits were the only deposits of this
type to have been evaluated according to mining standards, and represent
the only seafloor massive sulphides where an indication of the resource
potential had been obtained.
Preussag’s work he stated reveals that the Atlantis II Deep has a
surface of about 30 square kilometres. It contains 94 million tonnes of
sulphides, dry and water-free, with an average metal content of 2% zinc, 0.5%
copper, 39ppm silver and 0.5ppm gold. Based on these estimates, he
concluded that the deposit contained approximately 50 tonnes of gold and
about 4,000 tonnes of silver. Noting that the Atlantis II Deep was only one of
21 deeps in the Red Sea, he stated that there was doubt of the significance of
the resource potential of these deeps.
Turning to the sizes and tonnages of the other known seafloor massive
sulphides, Professor Herzig stated that information in this regard was rather
limited. He noted that other than the Atlantis II Deep, information on size and
tonnage were available for only three other deposits: Middle Valley on the
Juan de Fuca Ridge which is about 200 nautical miles west of Vancouver
Island in Canada; a site on the East Pacific Rise located at 13*N, and the TAG
mound at the Mid-Atlantic Ridge. Middle Valley, he informed participants,
was drilled twice under the Ocean Drilling Programme. Drilling indicates
that between 8 and 10 million tonnes of massive sulphides ore covered by
sediments are available at this site. This estimate he pointed out has been
disputed in some circles and placed at about 80 to 100 million tonnes. At the
East Pacific Rise site at 13˚ N, it is estimated that about 5-10 million tonnes of
ore grade material are available while drilling of the TAG mound at the Mid-
Atlantic Ridge in 1994, indicates about 2.7 million tonnes of sulphides ore at
the seafloor and 1.2 million tonnes of sulphide ore below the seafloor, which
amounts to approximately 4 million tonnes.
With respect to the mineralogical composition of the samples taken
from mid-ocean ridges, Professor Herzig said that their mineralogy is quite
simple. The high temperature veins of the deposits are commonly lined by
chalcopyrite or isocubanite, which are high temperature copper minerals. The
outer parts of the deposits contain sphalerite, which is a zinc sulphide, pyrite
an iron sulphide and a couple of other minerals.
INTERNATIONAL SEABED AUTHORITY 151