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Minerals Report - International Seabed Authority

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With regard to marine mineral deposits, Dr. Rona stated that marine<br />

metal and non-metal, non-fuel mineral deposits were considered to be<br />

primarily derived from the erosion of continental rocks and carried into the<br />

sea by rivers in solid (sediment) or dissolved phases. The minerals<br />

accumulated as beach and placer deposits of various heavy minerals<br />

containing metals and non-metals of terrigeneous origin. Dr. Rona identified<br />

two provinces for mineral occurrences. First, the province of the continental<br />

margin consisting of the continental shelf, slope and rise and then the deep<br />

ocean basin with the submerged volcanic mountain ridge that runs through<br />

all the ocean basins of the world and the vast abyssal plains.<br />

He noted that in relation to placer deposits which are mechanically<br />

eroded from source rocks on the continent and are deposited in sediments on<br />

the continental margin, it is only the most accessible of these deposits in<br />

particular those that are exposed on or near the sea floor, that we have know<br />

about. He pointed out that placer deposits may also be deeply buried within<br />

the sediments of the continental margin utilizing a global map he showed the<br />

distribution of marine placer deposits around the world. He stated that there<br />

are probably fewer sites of metals and non-metals, fewer than about 20 sites<br />

that have actually been operational. He identified on the map gold placer<br />

sites off Alaska that have been intermittently active depending on the price of<br />

gold. He stated that there is hardly any activity involving marine placer<br />

deposits off South America. He identified locations of offshore coral deposits<br />

off Great Britain and Italy. In relation to Africa, he noted that diamonds have<br />

developed into an important industry and said that the workshop looked<br />

forward to learning more about that from Mr. Corbett. Professor Rona<br />

informed participants that off south East Asia there are a number of metal<br />

sites - chromite sites off in Indonesia and Sulawesi Island, a gold site off New<br />

Zealand, and tin mining sites offshore Thailand and Indonesia With regard to<br />

common materials - sand and gravel he noted that this marine mineral that is<br />

very important for the construction industry and for concrete has represented<br />

nearly half of the offshore hard mineral mining industry. Another important<br />

untapped resource he explained are marine phosphorites which precipitate<br />

from deep sea water rich in phosphate as the deep water up wells in certain<br />

areas of the ocean basins specifically, those areas in the trade wind belts, up to<br />

30 degrees north and south of the equator.<br />

INTERNATIONAL SEABED AUTHORITY 94

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