http://arxiv.org/ftp/physics/papers/0608/0608014.pdf
----- Original Message -----
From: "Fries, Marc D" <[email protected]>
To: <[email protected]>
Sent: Monday, April 13, 2009 4:57 AM
Subject: Re: [meteorite-list] Black Diamonds: A interesting PBS NOVA article
Wish I¹d seen this one when it came out; I¹d have gladly written a
rebuttal
paper. Not quite sure how they can claim there is a "complete absence of
a
deep Earth fingerprint", especially since they point out the low delta-C13
values in carbonadoes themselves. The same range of values is seen in
reduced carbon from both terrestrial and martian igneous rocks, as other
papers have noted. Nitrogen has been noted in mantle fluids numerous
times
as well and could easily be the source of the nitrogen in carbonadoes.
I've
never seen "planar defect lamellae" in a carbonado, which this paper
mentions but doesn't show. Planar defects can be simply the result of
strain while buried, and only for silicates have the criteria for
distinguishing strain-induced lamellae from shock-derived PDF's been
established. All of the features of carbonadoes can be explained by
formation in a deep-Earth environment from carbonaceous fluids or gases
with
the caveat that it would have to be a very reducing environment. There
are
two comments to be made about that - 1) that very fact has been used to
explain away the possibility that a natural reactor is the source of
carbonadoes, and 2) it would be a rare environment, but that is consistent
with the fact that carbonadoes have basically only been found once in
Earth's historical record. It also only requires a casual perusal of the
mineral record to see examples of extremes of both reducing and oxidizing
environments in the Earth's crust.
Beyond this note, I'm really too busy to get into this. Carbonadoes are
very cool and still mysterious, but I have yet to see a convincing
argument
that they are extraterrestrial. I've examined a few myself and found them
to be a marvelous oddity, but a terrestrial oddity. I certainly wouldn't
evoke an asteroid-sized diamond impactor to explain them.
Cheers,
MDF
On 4/10/09 9:28 PM, "Steve Schoner" <[email protected]> wrote:
Here is the first article by Stephen Haggarty and others:
http://www.garai-research.com/research%20statement/carbonado/carbonado-infrare
d.htm
Looks to be a very compelling argument.
Steve.
[meteorite-list] Black Diamonds: A interesting PBS NOVA article
Paul bristolia at yahoo.com
Fri Apr 10 23:15:49 EDT 2009
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Steve Schoner wrote:
"Here is a very interesting PBS article on carbonados.
http://www.pbs.org/wgbh/nova/diamond/sky2.html "
Also look at:
Kagi, H. and S. Fukura, 2008, Infrared and Raman spectroscopic
observations of Central African carbonado and implications for
its origin. European Journal of Mineralogy. vol. 20, no. 3,
pp. 387-393, DOI: 10.1127/0935-1221/2008/0020-1817
http://eurjmin.geoscienceworld.org/cgi/content/abstract/20/3/387
McCall, G.J.H., 2009, The carbonado diamond conundrum.
Earth-Science Reviews. vol. 93, no. 3-4, pp. 85–91.
http://dx.doi.org/10.1016/j.earscirev.2009.01.002
Yokochi, R., D. Ohnenstetter, and Y. Sano, 2008, Intragrain
Variation in g13C And Nitrogen Concentration Associated
with Textural Heterogeneities of Carbonado. The Canadian
Mineralogist. vol. 46, no. 5, pp. 1283-1296, DOI:
10.3749/canmin.46.5.1283
http://canmin.geoscienceworld.org/cgi/content/abstract/46/5/1283
Diamonds, II: Diamond and Carbonado: Crystal Habits and Surface
Morphology
http://www.turnstone.ca/diamond2.htm
yours,
Paul H.
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