Ores from the ocean

Geologists from Canada, the United States and Germany have now attempted to determine whether such deposits are large enough to contribute to covering the worldwide demand for raw materials. For this purpose they selected 106 deposits regarded as representative of all occurrences on the seafloor. They estimated their metal content using several well-studied deposits as a basis and by performing theoretical calculations. Their results revealed a significant discrepancy between the sulphide deposits and the amount of material emitted from the black smokers. The hydrothermal vents release considerably more metals from the bowels of the Earth than is actually found in the deposits on the ocean  floor. Most of the metals are deposited in the surrounding area in highly diluted form and are therefore unavailable for mining. “This factor has been underestimated,” explains Dr. Sven Petersen, a geologist at GEOMAR and co-author of the study. “As a result, the potential of deep-sea mining has often been exaggerated.” “We estimate that around 600 million tons of massive sulphides have been deposited in the immediate vicinity of the world-famous volcanic ridges,” says Petersen. Of this, only around 30 million tons consist of zinc and copper, the two most important metals that can be recovered from the deposits. This means that the area of the seafloor that is accessible to mining contains the same amount of zinc and copper that is mined worldwide in a single year. Given these findings, the authors suggest that costs and potential profits should be carefully analysed. At any rate, says Petersen, “Mines on land cannot be replaced by deep-sea massive sulphide mining.”

GEOMAR/Red.