Minerals Report - International Seabed Authority

hundreds of cores into that deposit to determine size, grade, tonnage and
distribution of mineralised zones. On the seafloor, pointing out that Professor
Herzig was co-chief scientist on the TAG mound drilling expedition, Dr. Rona
stated once again that 17 holes were drilled into that deposit. He informed
participants that overall core recovery was 12 per cent as compared with
nearly continuous recovery of cores that are just spaced metres apart for
ancient massive sulphides on land. They observed that sampling ability for
that type of assessment on the seafloor is limited and would remain like that
for the foreseeable future.
Having presented information on seafloor massive sulphides,
Professor Herzig turned his attention to mineral deposits that may be found
beneath the ocean crust in the upper mantle of the earth. He presented a map
showing the entrance to the Persian Gulf and the coastal State of Oman. He
pointed out that this area had one of the best exposures of ocean crust, thrust
up from the seafloor and exposing the upper portion of the earth’s mantle
between the curst. He pointed out a chromite deposit and said that in future
chromite, platinum and nickel sulphides deposits may be discovered in the
deep ocean.
Dr. Rona said that the ocean lithosphere that is created at the
submerged volcanic mountain ranges in the Atlantic and eastern Pacific
oceans are destroyed at plate boundaries around the Pacific. In this way, the
earth counterbalances the lithosphere that is created at the submerged
volcanic mountain range. He said that where the lithosphere is destroyed,
volcanic island chains are created and behind volcanic island chains, there are
spreading centres very similar to those at ocean ridges. Dr. Rona showed
participants two provinces related to the volcanic island chains in the western
Pacific Ocean; an area in from of the arc and a spreading centre behind the arc
called the ‘back arc basin’. He stated that a new discovery of polymetallic
massive sulphides had been made in front of the arc just south of Japan, in the
Isu Ogasuwara arc, called the sunrise deposit. In relation to back arc basin
deposits, Professor Rona provided an example in the Manus basin called the
Pacmanus deposit that is under development by Nautilus Minerals of
Australia. He expressed his desire to hear more about this deposit from Mr.
Julian Malnic.
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