Wednesday, December 21, 2011
Mining the Deep Sea: What’s it Worth? by Southern Fried Scientist
The shimmering insides of a vent chimney
In Jules Verne’s 20,000 Leagues Under the Sea*, the iconic Captain Nemo announced that “in the depths of the ocean, there are mines of zinc, iron, silver and gold that would be quite easy to exploit” while predicting that the abundance of marine resources could satisfy human need. If the pace of development for deep-sea mining projects and the estimated value of deep-sea ores is any indicator, it seems as though our misanthropic mariner was wrong on both counts.
In The abundance of seafloor massive sulfide deposits, an international team of geologists attempts to quantify the total available copper and zinc contained in deep-sea massive sulfide mounds. Seafloor massive sulfide mounds are a byproduct of the processes that create deep-sea hydrothermal vents. As super-heated sea water emerges from the vent, it deposits heavy metals and other elements and minerals along the walls of the vent. Over thousands of years, an active vent field can build up a huge mound of metal and mineral rich ore – a massive sulfide mound. In addition to copper and zinc, these mounds can contain gold and silver. Generally, the ore is of much higher quality than its terrestrial counterpart. Over the last few decades, many exploration companies were eyeing these deposits, but it’s only recently that technological developments and economic incentives have aligned to permit potentially profitable deep-sea mining.
Not all hydrothermal vent systems produce massive sulfide mounds, and not all massive sulfide mounds are rich in heavy metals and valuable ore. To determine how much ore really is available in the deep sea, Hannington and his team examined 32 control sites of approximately equal size that broadly represent the geologic conditions of the global seafloor. They discovered 106 ore deposits great than 100 square meters, with many concentrated around neo-volcanic regions (areas of volcanic activity where most hydrothermal vents are found). Based on these samples, they estimated that there are approximately 900 neo-volcanic massive sulfide deposits, but that number could be as low as 500 or as high as 5000.