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Mineral 'Forest' Found Growing at Bottom of Pacific

May 17, 1987|JANNY SCOTT | Times Staff Writer

SAN DIEGO — A team of ocean researchers has found a "forest" of mineral deposits in a remote corner of the Pacific Ocean that they say vastly expands the area of the ocean floor that may be ripe for commercial exploitation.

Diving at depths of 12,000 feet in the western Pacific near Guam, the Scripps Institution of Oceanography team found itself last month in a strange seascape of mounds and "chimneys" created by boiling water spewing out of the earth through cracks in the sea floor.

Anemones swarmed into the area to feed. There were snails covered with hair to snag passing bacteria and organic matter. In an apparently symbiotic relationship, shrimp appeared to herd the snails into the area, then feed off the materials accumulating on their backs.

'Topless Towers'

"There were so many chimneys that we called this area the 'topless towers' after Marlowe's description in Faust," said Harmon Craig, the professor of geochemistry and oceanography who led the expedition. " . . . The water coming out looks like glycerin, absolutely clear. You could see it shimmering, just like you see air shimmering on the surface of the desert."

In a briefing last week, Craig said the discovery marked the first time sulfide ore deposits had been found in one of the world's so-called "back arc basins," the areas behind the deep trenches and arcs of volcanoes common in the western Pacific.

He said the deposits appear to result from "spreading" on the basin floor, which creates fractures through which sea water is sucked into the earth. There, heat of a magma chamber raises the water temperature to extraordinary levels.

The fluid then percolates through the volcanic rock, extracting and carrying with it metals such as copper, zinc and iron. Finally, it shoots back up through the ocean floor in a hydrothermal spring at temperatures up to 600 degrees Fahrenheit.

"Iron, nickel, silver, copper--all the metals that we want are concentrated," Craig said. "Sea water is essentially a scrubber that does things for us. . . . The ocean does the extraction for us.

"We simply have to figure out how to get down and mine this stuff at 12,000 feet, which is a job for technology."

He described the sulfide deposits as among the most extensive his team had ever seen in its underwater explorations.

Plume of Methane

Craig said he was drawn to the area four years ago when he and others, working in a boat in the area, noticed a plume of methane in the water column. He said the only explanation for the presence of methane was the proximity of hydrothermal vents.

Hydrothermal vents with sulfide chimneys had been seen previously only along the East Pacific Rise and the Mid-Atlantic Ridge, Craig said. There, plates of the earth's crust are spreading apart and new crust is being created by magma welling up from within the earth.

Working on a grant from the National Science Foundation, Craig's team last month returned to the area 186 miles west of the Mariana Trench, bringing with it the submersible research vessel, Alvin. In a basin ringed by two volcanic ridges, they came upon the vents.

"There are just hordes of tall chimneys everywhere--chimney after chimney after chimney, like a huge forest," said Craig, whose team captured the sight on murky videotape from a camera attached to the submersible.

Snails, shrimp and mussels clustered in one area. There were barnacles at depths at which Craig said they had never been found before. The team christened one area "anemone heaven" for the myriad anemones that they followed in order to find the first vent.

Craig described the chimneys as contorted masses of glistening crystals rising in some cases up to 30 feet high. They were covered with barnacles, worms and snails. He said the clear spout of water suggested "100% extraction" of the minerals in the chimneys.

The team descended 10 times to the ocean floor--a trip that takes several hours, one way. On six of the 10 dives they found hydrothermal vents. They also collected sample chimneys that Craig brought back to San Diego.

Miriam Kastner, a professor of geochemistry at Scripps who was on the expedition, said the major metals in a sample displayed Thursday were copper, zinc and iron sulfides. She said the "accessory metals" could include silver, gold, cobalt and arsenic.

Kastner said it appeared that the metals found in the chimneys from the basin could have greater potential economic value than those found along the East Pacific Rise.

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