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Earthquakes Deposit Gold In Fault Zones

Posted by samzenpus on from the shake-rattle-and-gold dept.

sciencehabit writes "Gold deposits may be created in a flash—literally. Along fault zones deep within Earth's crust, small cavities filled with fluids rich in dissolved substances such as gold and silicate minerals can expand suddenly to as much as 130,000 times their former size during a major earthquake, a new analysis suggests. In such circumstances, pressure drops accordingly, driving a process the scientists call flash evaporation. And when the pressure in the cavity suddenly drops, so does the solubility of minerals in the water there. Along with substantial quantities of quartz, large earthquakes could deposit as much as 0.1 milligrams of gold along each square meter of a fault zone's surface in just a fraction of a second Typical rates of seismicity along a fault, such as the San Andreas fault zone shown in the main image, could generate a 100-metric-ton deposit of gold in less than 100,000 years."

18 of 55 comments (clear)

  1. I smell a future James Bond plot... by jfalcon · · Score: 4, Funny

    Much like a cross between Goldfinger and View to a Kill.

    --
    boom goes the dynamite....
    1. Re:I smell a future James Bond plot... by Jeremiah+Cornelius · · Score: 5, Funny

      Man to God: What is a million years like to you, God?

      God: A million years? To me that's just like one of your seconds

      Man: I see! Then... What is a million DOLLARS like to you, God?

      God: I'm feeling you, man. You can guess, a million dollars to me is just like one of your pennies.

      Man: OK, God! Can I ask you for a penny, then?

      God: Sure! Just hold for a second...

      --
      "Flyin' in just a sweet place,
      Never been known to fail..."
  2. 1kg a year by RichMan · · Score: 3, Informative

    100 metric tons/ 100,000 years
    1 metric tonne/1000 years
    1000kg /1000 years

    1kg/year

    1. Re:1kg a year by schneidafunk · · Score: 4, Informative

      Which turns out to be worth $51,740 according to today's price of gold.

      --
      Some people die at 25 and aren't buried until 75. -Benjamin Franklin
    2. Re:1kg a year by tgeller · · Score: 3, Informative

      ...over the *entire San Andreas Fault*. So $50,000 isn't enough to survey and extract it all.

      Still: it's interesting in its own right. Congrats to the researchers!

      --
      Tom Geller
    3. Re:1kg a year by ShanghaiBill · · Score: 2

      ...over the *entire San Andreas Fault*. So $50,000 isn't enough to survey and extract it all.

      Why would you only want to extract one year's deposit? The San Andreas Fault has been around for 30 million years. So the total value of gold should be worth about $1.5 trillion. That is about $1.9 billion for each of its 810 miles.

      Of course dumping that much gold on the market may depress prices slightly.

       

  3. Re:Sounds like... by jellomizer · · Score: 5, Funny

    Dude, you found a way to popularize Fracking again!
    Natural Gas and GOLD!!!

    --
    If something is so important that you feel the need to post it on the internet... It probably isn't that important.
  4. So how do they keep the gold from dissolving? by khallow · · Score: 4, Insightful

    There doesn't seem to be much point to the observation since the gold can dissolve again, perhaps even within a few minutes of the end of the earthquake (it is hot down there, especially after a big earthquake).

    1. Re:So how do they keep the gold from dissolving? by PPH · · Score: 2

      Lava? TFA says water. So the approach might be to circulate water through deep strata, dissolve the minerals out and pump them back to the surface. Flash evaporate that and pump the water back.

      It might be interesting to revisit some old oil or natural gas wells that have been injected with water to increase their yield. The water has had time to dissolve minerals, so now we can bring it to the surface and see what settles out.

      --
      Have gnu, will travel.
    2. Re:So how do they keep the gold from dissolving? by khallow · · Score: 2

      unless fluid pressures and temperatures rise considerably

      Let us recall, that was why the gold was there in the first place. It was originally dissolved in solution because of high fluid pressures and temperatures. I'm pretty sure temperature actually increases after an earthquake, so in order for precipitation to occur and stay, either the pressure has to drop and stay dropped, or gold becomes trapped as you claim.

      Even If there is any re-dissolution, it will probably re-precipitate out again shortly and nearby

      Why? Gold is no more likely to precipitate, if it's been in solution for a long time versus a short time. And why wouldn't have done so in the absence of the earthquake?

      Gold can precipitate either if the temperature of the water cools down or its chemistry changes to something more basic in PH. A fault provides opportunities for both. It's a means for water to leak down, dissolve metals, and return to the cooler near surface.

      It also moves different rock types around. So your gold-bearing igneous rock may end up next to limestone. Then fluids may circulate between the two rock types and slowly transfer gold and other metals to the limestone body.

    3. Re:So how do they keep the gold from dissolving? by khallow · · Score: 2

      It's worth noting that geothermal plants already do this. And as a result, they tend to have a nasty scaling problem in their plumbing. I think it would be interesting to try this, say pump the working fluid through a bed of crushed limestone after the heat has been extracted. Then after a while, cart the results off to a mine and extract whatever metals have been left behind.

    4. Re:So how do they keep the gold from dissolving? by WindBourne · · Score: 2

      Simbol Materials. However, at this time, recovering Au is not profitable enough. BUT, I am going to guess that with enough injections over and over that we will soon see the Au concentration rise to the point where it is profitable to look at it.

      --
      I prefer the "u" in honour as it seems to be missing these days.
    5. Re:So how do they keep the gold from dissolving? by MarkRose · · Score: 2

      There is gold everywhere, but yes, fault lines are a great way to find certain kinds of gold deposits. If you want more information on why gold ends up where it does, I highly recommend a series of videos put out by the Sprott Group on ore deposists.

      --
      Be relentless!
  5. Miners Know by A10Mechanic · · Score: 5, Interesting

    When I was younger, we'd explore the old 1800's silver mines at Alta, Utah. When the old miners hit a fault line (underground), they'd span out and mine that fault for all it was worth. It was pretty neat for us finding a rock face perfectly smooth and straight (the fault), that had been stoped out a hundred years ago, miles underground. It was like going back in time. In hindsight, it was probably dangerous... Ah, youth.

  6. Gold is abundant. So are all other metals. by 140Mandak262Jamuna · · Score: 2

    Sea water contains so much of salt of every metal there is. Thousands of tons of gold exists in the sea water. Just the cost of extraction far outweighs the value of the extracted metal.

    --
    sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
    1. Re:Gold is abundant. So are all other metals. by cusco · · Score: 2

      Sewage is a considerably better source.

      "http://pinktentacle.com/2009/01/gold-mined-from-sewage-sludge/"

      A sewage plant in Japan's Nagano prefecture has started mining gold from sludge, earning a cool 5 million yen ($56,000) in its first month of operation.

      --
      "Think about how stupid the average person is. Now, realise that half of them are dumber than that." - George Carlin
  7. Something for the goldbugs... by Anonymous Coward · · Score: 2, Interesting

    The oceans contain about 20 million tons of gold, dissolved in the seawater and on the seabed, eclipsing the worlds current stock of mined gold by more than 100 times.

    Ironically, those promoting a gold standard for financial stability, would ensure that hyperinflation occurs in the future; as soon as innovations in nanotechnology, make the cost of extracting gold from seawater affordable/cheap, the value of gold itself will then plummet as its availability increases, causing inflation and eventually hyperinflation.

  8. This is what they discovered by Diamonddavej · · Score: 3, Interesting

    Weatherley and Henley investigated a mesothermal gold deposit, the Revenge Mine in Australia (also known as orogenic gold deposits). These gold deposits form deep underground during mountain building events, generally 3 to 20 km deep, where greater hydrostatic pressures normally prevent fluids from boiling. Previously, geologists speculated that mesothermal gold ore was deposited when fluids cooled or interacted with other fluids with a different chemistry, not so it seems. Weatherley and Henley claim that, even at great depths and pressures, fluid pressure in a fault zone can momentarily approach zero during an earthquake, this is a great surprise. Also, the (normal) temperature and pressures during the formation of the Revenge Mine deposit was 1675 to 2075 bars and 425 to 525 C, this suggests the water was a Supercritical Fluid. I wonder if a phase change from supercritical fluid to a gas facilitated the precipitation of gold.

    Also, it should be pointed out that role of Earthquakes in the formation of gold and other mineral deposits has been acknowledged for decades (in particular the near surface epithermal fault hosted gold-silver veins). Epithermal deposits are formed near the surface (generally less than 1 km), the frequent occurrence of breccias, broken rock fragments and voids in the faults attests to vigorous fluid boiling. One famous example of earthquake provoked mineralisation is the San Andreas fault, where hot springs issuing from the fault zone emit more arsenic and mercury after an earthquake, gold is presumably deposited at depth as well e.g.

    Sibson, R.H. 1987. Earthquake rupturing as a mineralizing agent in hydrothermal systems. Geology 15(8), 701-704.