Scripps Team Finds Mineral Deposits in Pacific

A team of ocean researchers from San Diego 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.

“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.”

Heated by Magma

In a briefing Thursday, 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, the heat of a magma chamber raises the water temperature to extraordinary heights.

The water 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 as high as 600 degrees Farenheit.

“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 extensive underwater explorations by submersible.

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. 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 under 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.

Glistening Crystals

“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 to 30 feet high. He said the clear spout of water suggested “100% extraction” of the minerals in the chimneys.

Ten times, the team descended 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. However, she said, the deposits must be mapped and estimated before any commercial exploitation can occur.