[meteorite-list] Meteorites delivered Earth's gold

From: Mark Bowling <minador_at_meteoritecentral.com>
Date: Sat, 10 Sep 2011 15:50:16 -0700 (PDT)
Message-ID: <1315695016.29500.YahooMailNeo_at_web161421.mail.bf1.yahoo.com>

Carl & all,
From what I understand gold is deposited with quartz because gold rarely occurs as a mineral.? Mineral deposits are formed by mineralized waters and magma. As these solutions move along faults, joints and form veins,?different elements "mate?together" to produce minerals as pressure/temp conditions change.??The remaining solution?will consist of the elements that didn't precipitate our or?combine with the other elements to form a specific mineral.? This is usually excess silica, which comes out as quartz (because there are few things left to combine with and produce silicate minerals) and gold (if it was there to begin with).? I suppose this is how most deposits of native metals/elements occur.? It's?a basic prospector's understanding, but that is what I have come to learn.? Gold and quartz don't have to be together, but they often are.? But that's not because quartz is necessary in the formation of gold.
?
All elements on earth come from space, both gold and silica.? I've never looked into why quartz doesn't occur in meteorites, but I suspect that conditions existed where all the silica was used up to form silicate minerals (that we do find in meteorites) and no excess silica remained to form quartz.? Gold occurs in meteorites in traces because it isn't abundant in the solar system. Gold occurs in commercial deposits on earth because it can be concentrated by weathering processes found on earth.? That doesn't occur in space so it remain as a trace element.
?
I hope the others out there who have a better understanding will chime in and correct me and fill in the gaps of my limited understanding :)
?
Clear skies,
Mark B
Vail, AZ

From: "cdtucson at cox.net" <cdtucson at cox.net>
To: "meteorite-list at meteoritecentral.com" <meteorite-list at meteoritecentral.com>; Paul H. <oxytropidoceras at cox.net>
Sent: Saturday, September 10, 2011 2:36 PM
Subject: Re: [meteorite-list] Meteorites delivered Earth's gold

Paul, List,
It seems to me that much of the Gold found on Earth is accompanied by Quartz.? In fact most of the finest Non-nugget specimens are usually found in quartz.
That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. . Quartz does not seem to be terribly abundant in meteorites.
Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites?
Do these researchers consider the Quartz issue here?
Thanks.
Carl

--
"Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote". 
---- "Paul H." <oxytropidoceras at cox.net> wrote: 
> Young Earth was sprinkled with precious metals
physicsworld.com, Sept. 7, 2011?
http://physicsworld.com/cws/article/news/47116
Where does all the gold come from? University of 
Bristol, ?Sept 7, 2011?
http://www.bristol.ac.uk/news/2011/7885.html
Meteorites delivered Earth's gold, by Leila Battison
BBC News, Sept 8, 2011?
http://www.bbc.co.uk/news/science-environment-14827624
The paper is:
Willbold, M., T. Elliott, and S. Moorbath, 2011, The 
tungsten isotopic composition of the Earth?s mantle 
before the terminal bombardment. Nature. vol. 477,
no. 7363, pp. 195-198. DOI: 10.1038/nature10399
http://www.nature.com/nature/journal/v477/n7363/full/nature10399.html
A related paper is:
Marty, B., and A. Meibom, 2007, Noble gas signature 
of the Late Heavy? Bombardment in the Earth?s
atmosphere. eEarth. vol. 2, pp. 43?49.
PDF file at:
http://hal.archives-ouvertes.fr/docs/00/33/07/83/PDF/ee-2-43-2007.pdf
Yours,
Paul H.
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Received on Sat 10 Sep 2011 06:50:16 PM PDT