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posted by chromas on Thursday July 02 2020, @04:30PM   Printer-friendly
from the where-the-mother-lode-gives-birth? dept.

Geologists identify deep-earth structures that may signal hidden metal lodes

If the world is to maintain a sustainable economy and fend off the worst effects of climate change, at least one industry will soon have to ramp up dramatically: the mining of metals needed to create a vast infrastructure for renewable power generation, storage, transmission and usage. The problem is, demand for such metals is likely to far outstrip currently both known deposits and the existing technology used to find more ore bodies.

Now, in a new study, scientists have discovered previously unrecognized structural lines 100 miles or more down in the earth that appear to signal the locations of giant deposits of copper, lead, zinc and other vital metals lying close enough to the surface to be mined, but too far down to be found using current exploration methods. The discovery could greatly narrow down search areas, and reduce the footprint of future mines, the authors say. The study appears this week in the journal Nature Geoscience.

[...] The study found that 85 percent of all known base-metal deposits hosted in sediments-and 100 percent of all "giant" deposits (those holding more than 10 million tons of metal)-lie above deeply buried lines girdling the planet that mark the edges of ancient continents. Specifically, the deposits lie along boundaries where the earth's lithosphere-the rigid outermost cladding of the planet, comprising the crust and upper mantle-thins out to about 170 kilometers below the surface.

Up to now, all such deposits have been found pretty much at the surface, and their locations have seemed to be somewhat random. Most discoveries have been made basically by geologists combing the ground and whacking at rocks with hammers. Geophysical exploration methods using gravity and other parameters to find buried ore bodies have entered in recent decades, but the results have been underwhelming. The new study presents geologists with a new, high-tech treasure map telling them where to look.

Journal Reference:
Mark J. Hoggard, Karol Czarnota, Fred D. Richards, et al. Global distribution of sediment-hosted metals controlled by craton edge stability, Nature Geoscience (DOI: 10.1038/s41561-020-0593-2)

-- submitted from IRC


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  • (Score: 4, Insightful) by Immerman on Thursday July 02 2020, @06:11PM (4 children)

    by Immerman (3985) on Thursday July 02 2020, @06:11PM (#1015471)

    You don't have to lift anything. The raw material is very much "up" from here, and most of that "up" is between Earth's surface and orbit.

    Collect solar energy in the belt to refine ores (large mylar "umbrella" parabolic mirrors would melt things nicely), then form the refined products into inert reentry "capsules" and throw them at Earth. You only need about 1km/s delta-V to reach Earth, and with an industrial base and no atmosphere you don't need wasteful rockets, there's lots of far more efficient options. Maybe you strap on some cheap thrusters to fine-tune its trajectory, that'd be especially useful for landing them exactly where you want them.

    When the capsules reach Earth they aerobrake until they fall out of the sky in a blazing fireball shooting for the big bulls-eye you've painted in the middle of nowhere. Without parachutes, etc. they'd have a nasty impact, but you don't really care because they're just raw materials you're about to melt down and turn into something useful anyway.

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  • (Score: 1, Interesting) by Anonymous Coward on Thursday July 02 2020, @09:02PM (3 children)

    by Anonymous Coward on Thursday July 02 2020, @09:02PM (#1015524)

    With a bit of creativity, you won't even have to refine it in space first. You can use the fireball provided by earth's atmosphere to do some of the melting and splitting for you.

    • (Score: 2) by Immerman on Friday July 03 2020, @03:54AM (2 children)

      by Immerman (3985) on Friday July 03 2020, @03:54AM (#1015669)

      I'd be willing the bet that most anything that melts during reentry would immediately be blown off the surface by the high airspeed, and either be incinerated in the fireball, or condense and rain down across half a continent.

      Besides, the whole point of refining is to separate out the heavy base metals like iron and nickel so that you only have to ship the valuable ores back to Earth. Reducing the mass of your cargo by 90+% saves a bundle on shipping costs. And all that iron will be immensely useful for building stuff in space, while it's basically worthless on Earth.

      • (Score: 1) by khallow on Friday July 03 2020, @12:01PM (1 child)

        by khallow (3766) Subscriber Badge on Friday July 03 2020, @12:01PM (#1015719) Journal

        I'd be willing the bet that most anything that melts during reentry would immediately be blown off the surface by the high airspeed

        It's worth noting that some meteorites have been ice-cold to the touch right after they've fallen. That's how inefficient the process is at heating the meteorite.

        • (Score: 2) by Immerman on Friday July 03 2020, @01:10PM

          by Immerman (3985) on Friday July 03 2020, @01:10PM (#1015735)

          I'm sure it helps that they come with built-in ablative heat shielding.

          Phase transitions consume an enormous amount of energy - as one example it takes almost as much energy to melt ice without heating it (ice at 0C-> water at 0C = 79cal/g), as to heat the resulting water 100C to the edge of boiling (~100 cal/g). Going from liquid to gas consumes dramatically more energy that both, at 539cal/g.

          I don't know the numbers for rock, but I imagine they're pretty high, and most rock doesn't conduct heat well so all the heat absorbed will tend to be shed by vaporizing the surface rather than heating the layers beneath it. I suspect metallic asteroids would tend to warm up a lot more during reentry since metals conduct heat so much better.