In a review paper published June 23 online in the journal Mineralium Deposita, Cathles, Cornell professor of earth and atmospheric sciences, writes that while land-based deposits may be a dwindling source of valuable minerals, deposits on the ocean floor could power humanity for centuries.
The minerals, including sulfur, copper, zinc, iron and precious metals, are contained in volcanogenic massive sulfide (VMS) deposits that form on the ocean floor where tectonic plates pull apart and allow magma (molten rock) to invade the Earth's 3.7-mile- (6 kilometer-) thick crust. The magma heats seawater to 662 degrees Fahrenheit (350 degrees Celsius) and moves it through the ocean crust via convection; and the seawater deposits the minerals where it discharges along the ridge axis.
Mineralium Deposita - What processes at mid-ocean ridges tell us about volcanogenic massive sulfide deposits
UPDATE - Review of Nautilus Minerals, the first commercial ocean floor gold and copper mining company.
That knowledge, along with the known thickness of the ocean crust, allows researchers to calculate the quantity of dissolved minerals that could be transported over each square meter of ocean floor.
If just 3 percent of the dissolved minerals precipitate -- an estimate based on earlier studies -- the ocean floor would hold reserves vastly greater than those on land, Cathles said.
In the case of copper -- a key component in construction, power generation and transmission, industrial machinery, transportation, electronics, plumbing, heating and cooling systems, telecommunications and more -- calculations show that just half of the total accumulated amount could be enough to bring the world's growing population up to a modern standard of living and maintain it for centuries.
"I think there's a good chance that it's a lot more than 3 percent," Cathles said. "But even just taking 3 percent, if you calculate how long the copper on the ocean floor would last, just half of it could last humanity 50 centuries or more.
With the necessary precautions, extracting the underwater deposits may also be a more environmentally friendly process than mining on land, Cathles said.
And it could provide other benefits, both scientific and psychological. Undersea exploration around ocean ridges could open doors to new research on the fundamental processes behind the formation of Earth's crust, he noted; and a more positive outlook on the future could lead to fewer wars and more positive engagement.
"We are not resource limited on planet Earth. For a human on Earth to complain about resources is like a trillionaire's child complaining about his allowance or inheritance. It just doesn't have much credibility in my view," he said.