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Geo-Joint: Deep-Sea Mining

Posted on November 11 2014

Deep-Sea Mining

Image: NOAA National Ocean Service Ocean Facts

Bottom trawling fishermen get their haul (and grind up the landscape) on the ocean’s bottom, and some divers collect rare corals down there.  Deepsea drilling rigs poke holes in the sediment under the ocean to find oil and gas, but there is another trove of treasure that has long been known, and only recently targeted.  Close to 40 years ago, in 1977, researchers doing ocean floor studies near the Galapagos Islands discovered geothermal vents.  These plumes of superheated water occur in places where there are fissures between tectonic plates, and ocean water that has percolated into the bottom sediments can come into contact with very hot rocks.  The heated water rises through the cracked and fractured rock, carrying dissolved minerals, and spurts out of structures built up by the deposition of those minerals.  Although there is a lot of sulfer and other harsh chemicals present in the solution, whole suites of animal life have evolved to live around and feed off of these seemingly toxic flows.  It is a strange world existing as if on another planet, with temperatures in excess of 600 degrees F, and thick with chemical compounds not friendly to any previously known creatures.

As the mineral-laden water comes in contact with the cold sea, deposits are built up which form  what are called “black smokers” – pipelike mineral tubes that conduct the cloudy, dark, sulfurous waters from Hell.  (sorry, went a little poetic there).  These rocky conduits can rise to a height of 15 stories!  This alien landscape is more than a curiosity, in the eyes of prospectors.  Besides sulfides, the deposits contain copper, lead, zinc and even some silver and gold.  Perhaps even more important in today’s economy though, are the rare earth minerals they also contain – key ingredients in cell phones and flat-screen TVs.  These “gotta-have” items have forced manufacturing nations to deal with China, which seems to have a corner on terrestrially-sourced rare earth minerals.  If engineers can successfully mine the seafloor, China’s advantage would be severely curtailed.

So there’s money to be made at the bottom of the briny deep, but it’s costly.  Remotely controlled mining equipment has been developed, which you can be sure is far more complicated and expensive than its land-based equivalent.  Systems have been developed for pumping a slurry of the ore to waiting ships at the surface, a mile overhead.  The energy for that operation alone has to be pricey, and then the ore has to be shipped to the nearest (or most economically advantageous and politically cooperative) processing facility.  Mining companies have taken all this into account and feel it is doable and economically viable, but so far no large scale project has been undertaken.  Plans are underway for mining the seafloor off Papua New Guinea but even after sorting out technical and financial problems, difficulties with the location of processing facilities threaten to derail the project.  Moreover, concern is rising over the ecological effects of tearing up these seafloor structures that have never before been touched by man.  Will the animals that colonize the black smokers be able to rebound from other areas?  Can some part of the mining area be left intact to facilitate this?  Should mining be restricted to old vents that have gone inactive and no longer support life?  Who is in charge of monitoring compliance with mining law a mile underwater?  These and other questions pose vexing problems that may curtail the dreams of those seeking riches from the deep.

Image: Earth Magazine

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