Minerals Report - International Seabed Authority

4. Technical Requirements
For research and resource assessment of polymetallic massive
sulphides deposits, technological advances are a critical factor. In the present
state of research and commercialisation, information on the depth extent and
therefore the size of the deposit, and the type of mineralisation and alteration
are extremely important. Drilling by the Ocean Drilling Program Leg 158 at
the active TAG hydrothermal mound at the Mid-Atlantic Ridge 4 has indicated
a total tonnage of 2.7 million tonnes of sulphides above, and 1.2 million tonnes
below the seafloor 5 . It was also found that high concentrations of base and
precious metals are confined to the upper few meters of the mound. The
mound itself consists of breccias with varying proportions of pyrites, silica,
and anhydrites that would not be economically recoverable. Initially, it was
thought that the entire mound consists of polymetallic massive sulphides.
Except for the TAG mound, the Middle Valley site at the Juan de Fuca
Ridge, and the Atlantis II Deep in the Red Sea, depth information is not
available for any of the known seafloor sulphides deposits. Research and
resource assessments of these deposits rely on surface samples only. As
drilling of hydrothermal systems by the Ocean Drilling Program will be the
exception rather than the rule, reliable portable drilling and coring devices are
required for research and industry. It has to be demonstrated that these
systems are actually capable of supporting drilling and coring several tens of
meters of massive sulphides and rock at the seafloor. The available
technology is an encouraging start but needs to be further developed in order
for drilling at the seafloor to depths of 50-100 m a routine operation by any
research vessel, and to reveal reliable information on the depth extent of
mound and chimney complexes (Table 4).
INTERNATIONAL SEABED AUTHORITY 310