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View Diary: BREAKING: Meteor airburst over Chelyabinsk (318 comments)

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  •  kinda (1+ / 0-)
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    ivorybill

    99.9999% of the initial metal the earth formed with sank to the core and stayed there, but that was an Event and not a continuous process.

    The earth started out homogenous, because impacts don't generate enough heat to get that much magma to behave like water. It might flow, but it still has structure and behaves like a solid in many situations. Over time radioactive decay heated things up and softened the magma, allowing metal to separate out into big lumps, which had enough mass to start to sink, generating more heat and allowing smaller lumps to sink, etc. until everything was separated out like salad dressing. This happened very fast, and we cooled back down very quickly afterward. Once we did, there was no process capable of creating that kind of precipitation again. So gold from impacts 3.8 billion years ago is still dissolved in rock circulating in the mantle and erupting out of volcanoes.

    Also, veins are a geological thing and don't have anything to do with impact craters, and gold IS pretty evenly distributed. Meteor Crater has an abandoned mine in the center built on the (correct) logic of metal being delivered by asteroid impacts. The problem was the meteorite vaporized and the iron was all over Arizona instead of in the hole.

    •  I didn't say veins were associated with craters. (0+ / 0-)

      Craters on Earth are all young because of all the erosive processes.  Veins are the contiguous bodies of impacts as they've been stretched out and warped over long periods of time by tectonic movement.

      Pour yourself into the future.

      by Troubadour on Fri Feb 15, 2013 at 12:25:38 PM PST

      [ Parent ]

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