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Wednesday, July 20, 2016

Geological Mystery Feature: Alluvial Platinum from Russia

          Any guesses as to the origin of this circular geomorphic feature?



    It's not a crater and it's not a volcano. . .




      It is in northeast Russia and it's the source of alluvial (think panning for gold) platinum. . .




     This landform is nearly perfectly circular, with a diameter just under 8 kilometers (5 miles) and a ridge about 600 meters tall. A river has eroded through the lip, draining rainwater and runoff out of the center. The ridge is bare rock, with vegetation growing both inside and outside the ring. 

     Any ideas? Guess now or read on. . .
      
     Kondyor Massif is an igneous intrusion piercing the surrounding sedimentary rock without ever forming a volcano or erupting from a crater. A column originally topped by a dome when it formed, 







the structure has undergone differential erosion so the softer material weathered and eroded first, leaving the harder ring behind with the rest of the column hidden below the surface.




       The Kondyor Massif located in Khabarovsk Krai, Far Eastern Federal District, Russian Federation, roughly 600 km (373 mi) west-to-southwest of Okhotsk, or some 570 km (354 mi) south-east of Yakutsk.  


       Slow cooling produced these valuable platinum specimens which are up to 1.5 cm in diameter. They later weather out of the Massif and are mined alluvially.





       How was you guess; did you use circular reasoning? :-)  Have you ever panned for platinum, silver, or gold?

Steph

20 comments:

  1. When I looked up "Alluvial" on Wikipedia, I was given a link to follow if I was looking for the American Thoroughbred broodmare of that name. Odd, I thought: if you plan to raise a winner, why name it for a placer? (That pun won't get me showered with praise...)

    The diagrams above reminded me of ones I've seen describing Kimberlite pipes. How about a little illumination on why valuable ores and gems are often found with such structures, as opposed to the rest of the planet, which gives rise to the term "dirt poor"?

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    1. It's a wonderful pun, jan! Wish I'd gone there first.

      Indeed, the Massif formation is similar to kimberlite pipes. It's the slowness of crystallization combined with the proximity to surrounding sedimentary rock with produces the platinum, diamonds and other precious materials.

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  2. My other association with the illustrations above, of course, is: Yakutsk, sure, I've conquered that lots of times in Risk. Never noticed anything particularly interesting there.

    My son was in Bergen, Norway, last week, and cousins posted pictures to Facebook of their trip to Reykjavik, and all I could think of was, I wonder if they know how many times I saved them while playing Harpoon 25 years ago?

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    1. Ya, kutsk for sure.

      Hahaharpoon. . .

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  3. Steph wrote:
    " Any ideas? Guess now or read on. . ."

    Before I "read on," my idea was aliens/extraterrestrials/crop-circles!

    LegoCyrclingTheWay-gons...AndThePoly-gons

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    1. Great crop "circles," Lego. The Poly-gons are fun, too.

      Knew the song but not the group. . .

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    2. And I like the "atoms and bonds" structure in the background of The Cyrcles singing. That double guitar is cool. "Red rubber ball" imagery doesn't do it for me (why rubber?!), but the tune is always catchy.

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  4. My parser was done in once again by the new UK PM. The headline read something like "May Flies To Meet Merkel". I thought, "Why does the German leader want to meet insects?"

    In Britain has an equivalent to Air Force One, they should rename it "Ephemeroptera".

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    1. Thank heavens for May; you're really going to have fun during her term, aren't you?

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    2. I may. I wonder if George Will?

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    3. I'm trying to figure out why I'm still sweeping mayflies off the windowsills when it's nearly August. Somebody didn't get the memo?

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  5. Some good ideas in case we get into politics over here. .

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  6. It's not surprising that the Last Universal Common Ancestor lived deep under the sea. We've long known that Luca sleeps with the fishes.

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  7. Cormac McCarthy's post-apocalyptic The Road was depressing, but at least it was paved.

    (I'll bet these cash-strapped towns aren't figuring the cost of wetting down their dirt roads to avoid washboarding.)

    Here in NJ, our governor has shut down road maintenance to avoid raising the gas tax, which hasn't changed in decades.

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    1. Fascinating. I wonder if it will substantially affect the petrichor after rains or wetting down. . .

      And they can't say it's the as phault any longer. . .

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  8. New post on "Hooked on Phononics: Spider Silk Sound and Heat" is now up.

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