Huge copper deposits in seabed off Canada
Wednesday April 1 3:33 PM EST
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DAVIS, Calif., April 1 (UPI) _ Earth scientists studying how metal ores are formed on the seafloor have identified an unexpected lode of copper in the Northeast Pacific Ocean.
The discovery, reported today in the journal Nature, may provide clues to finding rich new sources of copper on land. The finding was made by Robert A. Zierenberg of the University of California at Davis, California and a team of scientists investigating the deposition of ores rich in iron, copper, zinc, and other metals by springs of hot water that well from the seafloor in regions of volcanic activity.
On a 1996 expedition sponsored by the international Ocean Drilling Program, the research vessel JOIDES Resolution drilled cores in an active zone of the seafloor about 150 miles (241 kilometers) west of Vancouver Island, Canada. Initially, the researchers found what they had anticipated.
The cores from the top 300 feet (91 meters) of the Bent Hill sulphide deposit were indeed rich in copper. But as the drill bit pushed beneath the original seabed, it penetrated a second layer of copper ore that was even richer than the first.
About 300 feet (91 meters) beneath the seafloor, the cores revealed a second layer of ore, less than 50 feet (15 meters) thick but containing as much as 16 percent pure copper.
In the Nature article, the researchers estimate that the deposit above the seafloor, one of the largest in the world, contains nearly 9 million tons of copper. And Zierenberg believes that the richer lower layer could double that figure.
''This is definitely one of the largest, possibly the largest, deposit of copper ever discovered,'' said Zierenberg. He speculates that the lower layer was formed as the upwelling of mineral rich water cooled off.
When the mineral rich superheated water hits the cold seawater, various dissolved minerals drop out at particular temperatures. As the temperature of the water fell, the richer layer was deposited in fissures in porous rocks below the seafloor.
Zierenberg does not expect the discovery to trigger a copper rush off the coast of Canada anytime soon. Although an international consortium has announced plans to commence seabed mining off the coast of Papua, New Guinea, that deposit contains higher levels of such valuable metals as gold and silver _ and it is in more protected waters.
Moreover, getting at the newly discovered layer would mean digging more than 600 feet (182 meters) beneath the top of the sulfide deposit and into a seabed that is still spewing hot water from vents.
But Zierenberg believes the finding can be of immense benefit to miners on land. He points out that the big copper deposits that have been mined throughout history were once formed on the seafloor and then uplifted. And the pattern of deposition observed at Bent Hill is probably not unique.
''Many of these metal deposits were originally created on the seafloor and have been pushed up onto the continents as the Earth's plates collide,'' he said.
His suggestion: dig deeper. Huge deposits, such as those in Jerome, Arizona, were thought to be exhausted when miners encountered the rocks of the ancient seabed. But there may be an even richer ''mother lode'' waiting a few hundred feet down. ''This may make the miners go back and take another look,'' Zierenberg said.
(Written by Alan Hall in New York) _- Copyright 1998 by United Press International All rights reserved _- |
