Geologists drilling into the Pacific floor to study hot-water vents have made an unexpected discovery: a zone of high-grade copper ore deposited below the seafloor. The finding could point the way to similar valuable deposits on dry land.
Hot-water, or hydrothermal, vents are deep-sea springs where seawater heated by volcanic activity bubbles up through layers of rock and sediment to the seafloor, depositing copper, gold, iron, zinc and sulphur along the way. Sometimes the metals and minerals build hills called massive sulfide deposits, and copper-rich veins often occur just below these hills.
In the new research, UC Davis geologist Robert Zierenberg and international colleagues were profiling a massive sulfide deposit that lies off the coast of Vancouver Island, British Columbia.
Their findings are described in a letter to this Thursday's issue of the journal Nature.
As expected, the researchers found copper-rich veins at the hill's base. But about 180 feet below those veins, they unexpectedly struck a second copper zone. Its ore was up to 16 percent copper, which would be considered high-grade commercially.
"It's possible that copper deposits that have been mined on land may have a similar structure," Zierenberg said. "There may be additional copper ore zones below these deposits that remain to be discovered." However, he cautioned, environmental studies should precede any deep-sea mining.
The Nature letter adds that some of the boreholes into the Bent Hill deposit created new hydrothermal vents. Zierenberg noted that established vents are known to be inhabited by exotic biological communities that live on chemical energy without sunlight, so the new vents might serve as study sites for how those communities develop.
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Nature