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

From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Sun Mar 5 03:34:59 2006
Message-ID: <28b.6aecf4b.313bfca7_at_aol.com>

Sterling W. writes:

<< I don't know the values for the Nubia Sandstone,
but the range of sandstones is fluorine 180 to 450
ppm and boron about 10 to 85 ppm. The figures
for LDG is fluorine 7 ppm and boron 7 ppm, so
you see how the ratios shift as the content drops.

    As the temperature rises (microsecond by microsecond),
 the fluorine content drops much faster than the boron
 content. At some very high temperature (variable
 for each source rock), both fluorine and boron
 levels become the same, but at a higher level than
 in the final product.
 
     After that point, both are driven out of the melt
 plasma at the same rate, their petty chemical
 differences totally overwhelmed by the energy
 available. So, fluorine goes faster until that point
 is reached, after then, they drop together. >>

Hola Sterling,
Petty chemical differences....hmmmmm.....overwhelmed at moment x when they
behave identically (this is the cartoon "and then a miracle happens and we get
the desired solution")...I hope you can do better than this! This last
paragraph has pegged my bogometer and the needle broke as I see physical laws being
bent to accomodate your interesting and provolking speculations. It's either
the most unfounded, unscientific argument and counterintuitive I've ever heard
you seriously make - or - you speak about this thermometer as if you actually
were there watching the impact and taking notes by the microsecond on how
Boron and Fluorine behave under singular circumstances and states that are poorly
defined to start with! I didn't dispute the use of [F]:[B] to compare
different forms from the same source rock (a reasonable use of the "thermometer"),
that is not what you are doing. I hope you can see how you are pulling numbers
from out of the air which are all over the map and cooking pretty conclusions
out of them. To answer my question, I'd back up and ask for the following
modest data:
1. reference - Where you got moldavites bottoming out at [B]=30 ppm (for
[F]=30 ppm, at least)?
2. Based on how many samples is your "typical" value [F]:[B] of Ivory Coast
tektites and what was the low end for the ratio? Was it a lot less than 1?
How would your physics' scheme explain a value below 0.5 for the ratio....since
you have re-enforced the point I most object to by saying they magically reach
the same concentration and then decrease equally...
3. Without the respective values of F,B in Nubian sandstone near the crater,
my question isn't anywhere near answered:( !!

You mentioned:
 <<It looks like LDG had a very hot forming event,
so the high water content is a real puzzle.>>
It's only a real problem puzzle in this context because you have read too
much into and extrapolated much too far with the halogen thermometer concept.
The water, rather than being a problem to explain, might be telling you that the
F:B interpretation and extrapolations are all wet..., there is also a failure
to consider different resident times for the measureables in the melt as yet
another additional consideration. Not to mention of course the alternative or
coincident possibility that LDG's have that content due to the low or surface
altitude at which they formed...

 And this:
<<ALL terrestrial rocks have a F/B ratio greater
than 5.0 (often 20 or 30). but all impact glasses,
even the weakest dirtiest just barely melted impact
glasses have a F/B ratio less than 5.0 -- the result
of a few thousand degrees of heating.>>

"ALL" is a very encompasing term. Are you sure it wasn't mentioned
principally regarding a total of two dozen tektite samples and three events for which
the craters are known, weighted grossly in favor of Indochinites - rather than
the whole wide world? Sure, 5 quite possibly is the minimum in unimpacted
sediments worldwide but I'd need more than an arbitrary statement to believe it
after reading the other assertations...are we still refering to Dr. Koerbel's
work?

Bedtime, I have a date with a comet in a couple of hours:), 'Night,Doug
Received on Sun 05 Mar 2006 03:34:47 AM PST