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Minerals Report - International Seabed Authority

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seawater at the seafloor, but rather from a process where hydrothermal fluids<br />

interact with magmatic fluids that contained high concentrations of gold.<br />

Based on the samples taken from the surface of the deposit, Professor<br />

Herzig provided a summary of the geochemistry of Conical Seamount. The<br />

maximum grade of gold he informed participants, is 230g per tonne, with an<br />

average of 25ppm based on 40 samples. Base metals values he noted,<br />

however, are relatively low and are similar to values being mined at<br />

Ladlolam.<br />

The exploration strategy for Conical Seamount is to drill the deposit in<br />

order to find out whether it was a deposit with a small gold enrichment at the<br />

surface or whether it was indeed a gold deposit. He stated that the research<br />

team had submitted a proposal to the Ocean Drilling Programme to drill<br />

Conical Seamount just after the drilling operation in the Manus Basin.<br />

Returning to his proposal for a pilot mining site for seafloor massive<br />

sulphides, Professor Herzig stated that the advantages of Conical Seamount in<br />

this regard were that it is located very close to the island of Lihir, in the EEZ<br />

of Papua New Guinea, that there is direct access to a gold processing plant on<br />

the Island, that the water is relatively shallow (between 1,050 and 1,650m),<br />

that the gold grade of the deposit is high, and that the site is an inactive<br />

hydrothermal vent and is also sediment free.<br />

While noting that there is currently no technology available for<br />

seafloor massive sulphides mining, Professor Herzig said that the technology<br />

currently being used by De Beers for diamonds offshore Namibia could be<br />

adapted for this purpose. His thoughts included adapting the rotating cutter<br />

heads used in offshore diamond mining for seafloor massive sulphides<br />

mining, airlifting of the ore slurry produced from mining the sulphides to the<br />

mining vessel and then transferring the slurry by cargo vessel to the oxidation<br />

plant at Lihir.<br />

Professor Herzig concluded his presentation by presenting a summary<br />

of it. Firstly, he noted that a majority of the potential seafloor massive<br />

sulphides deposits are located in the exclusive economic zones of various<br />

countries. Secondly, he stated that drilling seafloor massive sulphides<br />

INTERNATIONAL SEABED AUTHORITY 157

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