[meteorite-list] Largest Crater in the Sahara Desert and LDG

From: Larry Lebofsky <lebofsky_at_meteoritecentral.com>
Date: Sun Mar 5 07:20:38 2006
Message-ID: <1141561232.440ad79078095_at_hindmost.LPL.Arizona.EDU>

Sterling:

Sounds good to me (though I study big rocks that you can see with a
telescope). It sounds like it is time for me to start reading up on tektites
too!

As a novice, would you basically say that tektites come from volatilized
material that has recondensed while an impactite derives from melted material
that never got hot enough to vaporize.

Obviously, you would have ranges of materials (hotter vapor or hotter and more
devolatilized liquid).

Larry

PS Did you see the comet? Never been clear enough and no access to a telescope
where I am.

Quoting "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>:

> Gee, Doug,
>
> For once, I am not creating a crackers theory of my own.
> I am merely explaining how a certain geochemical test procedure
> works. Not being a geo- or a cosmo- chemist, I am taking the
> word of Matthies, D. and Kroeberl, C., Fluorine and Boron
> Geochemistry of Tektites, Impact Glasses, and Target Rocks,
> Meteoritics, 26 (1991), 41-45, both of whom AM geochemists.
> Also, see K. H. Wedepohl, Handbook of Geochemistry (1978).
> Blah, blah.
>
> Think about it. You gotta rock. Mixture of complicated
> crystals. Many elements. Huge heating event. Rock melts.
> Rock vaporizes. Molecules dissociate. Now it's a plasma,
> composed entirely of elements, too hot to form compounds.
> The volatile elements in this plasma escape from the plasma
> faster than the less volatile, which in turn escape faster
> than the "refractory" (who are stubborn and hang around).
> The plasma continues to heat. Volatiles go faster and faster.
> At a high enough temperature, the mean free path of atoms
> and their rate of escape is pretty much totally determined
> by the thermal energy of the plasma and the mass of the atom
> and the chemical characteristics of the substance matter not
> at all. It's physics now, not chemistry. Element 5 (mass 11)
> and element 9 (mass 19) are both moving like there was
> a 38,000 degree plasma on their tail (and there is). They
> now escape at a similar rate. Get the literature. Look at
> the pretty graphs that show how it works. There's some
> chemical reason why this happens about the time they're
> at the same concentration, but I forget it. It's chemistry.
> Me, when I look at things like equilibrium condensation
> diagrams or the reverse of same, my eyes start to glaze
> over... So I just take their word for it. But as a physical
> phenomenon, it fits my intuition. Look at the other light
> atoms. Not many of them hanging around either.
>
> Makes silly hand gestures, points to self. I no chemist.
> Physicist. Like big things (universe, stars, planets, rocks
> the size of countries). Like little things (quarks, leptons,
> cute little bosons, petite atoms). Don't like things inbetween.
> That's why God made chemists and botanists. Let them
> sort it out. They like that sort of thing for some reason...
> In 1962, when the number of "elementary" particles
> officially went over 200, Enrico Fermi, getting old and
> cranky, yelled, "Look at this f***g zoo! If I wanted this
> mess, I'd have become a botanist!" (He was right; how
> can you have more "elementary" particles making up
> elements than there are elements? Maybe it means that
> making elements is hard.)
> Crusty old physicists. Show me String Theory when
> you can put the whole thing on ONE PAGE. Otherwise,
> go back and work on it some more.
>
> Deep breath. The F/B ratios for ALL terrestrial rocks
> comes from Kroeberl and Company (all of this does). That's
> for the bulk compositional analyses of crustal rocks everywhere
> that geologists have made 100,000's of for the last century
> or so. Boring... Boron's just not as common as fluorine. The
> ratios run 10:1, 20:1, 30:1. Earth rock just isn't (in bulk)
> boronic. That crusty stuff in Death Valley doesn't count...
> If boron was common, would they have send Ronald Reagan
> and those 20 mules into Death Valley? (Old TV referrence.)
> If you think this is all hooey, complain to Kroeberl and Co.
> Also Wedepohl, who publishes thick books full of endless
> tables of bulk elemental compsitions. Lemme know what
> happens.
>
> Seriously, I am miffed. I don't think this stuff is whacky
> enough to be one of my whacky notions, and I'm insulted
> that anyone should think so... Obviously, I'm not being
> whacky enough.
>
> I'm quiting. It's late enough that I could go out
> and wave at that comet myself.
>
> Sterling K. Webb
> --------------------------------------------------
>
>
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-- 
Dr. Larry A. Lebofsky
Senior Research Scientist
Co-editor, Meteorite                     
Received on Sun 05 Mar 2006 07:20:32 AM PST


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