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Re: Tektite / Impactite


-----Original Message-----
From: Louis Varricchio <varricch@aero.und.edu>
To: Impactika@aol.com <Impactika@aol.com>;
meteorite-list@meteoritecentral.com <meteorite-list@meteoritecentral.com>
Date: Friday, November 05, 1999 6:32 AM
Subject: Re: Tektite / Impactite


I haven't been able to send or receive emails since last wednesday.
Finally, early this morning, it started working again.  I have one major
change to suggest in the otherwise well worded earlier comments by Louis
Varricchio:
It would take ten HOURS or more of "fining" at high temperatures to get rid
of most of the bubbles to the degree observed in tektite glasses, and in
man-made glasses.  Real terrestrial impact melts are highly vesicular
because they had only a few tens of seconds at high temperatures.  On the
other hand, some layered tektites have bubble-rich layers, sandwiched
between bubble-poor layers.  It is obvious under the microscope that none of
these bubbles have moved more than microns, otherwise, there would be no
relatively bubble-free layers.  These bubbles are all generally less than
200 microns in diameter, and represent the originally angular spaces between
the microtektites that accreted to form the layers.  When you find such
small bubbles that are still angular (in layered tektites), then you know
that that portion of that tektite was never heated to more than about 900
degrees C.  Thorough heating much above that temperature results in
spherical bubbles due to surface tension.  The adjacent bubble-free layers
represent microtektites that accreted at higher temperatures, and were
therefore much more fluid.  Since they accreted on an atmosphere-free
planetary body (except for the propelling volcanic gases), and were more
fluid, they tended to not trap any vacuum spaces between the microtektites,
and formed a rather solid glass.  References?  You want references?  I've
listed a number of references in my past posts.  Has anyone ever taken the
time and effort to check out any of the references I've listed in the past
(besides Bernd)?  I've got a printed list of over 100 related tektite
references that I'd be happy to snail air-mail anyone free.  It can take
hours now for me to come up with a bunch of references (failing eyesight).
So, I'm speaking here from my memory of the tektite facts I've had published
in some 15 papers and abstracts (in several journals including Nature) over
the past  30 plus years, where I DID list numerous references.  If anyone
cares to ask specific questions that can maybe be answered with just a few
references, I'll give it a try.  Well over 2000 tektite papers and abstracts
have been published now, and I've got over 1000 of them in my personal
library.  I used to be able to "run" up to the Caltech libraries when I
didn't have something, but can't do that anymore.              Darryl
Futrell


>Personally, I think much of the mainstream interpretation of tektites
>ignores a huge, well reasoned body of evidence.  Tektites are so distinct
>from "impactites" as to place them in a class by themselves.
>
>To understand the most important argument againts the terrestrial impact
>origin of tektites it is necessary to know that the meaning of the word
>"glass" used by geologists and glass makers.  To a geologist, glass is any
>amorphous material, a silicate.  To a glass maker, glass is a substance
free
>of bubbles  Such a glass is a "good" glass (Type A glass)--just like
>tektites.  "Junk" glass (Type B glass) is made by a meteorite impact--i.e.,
>impactities.  Type A glass simply can't be made rapidly as you'd expect in
>an impact.  It needs time--10 minutes or more--to form.  The bubbles
>disappear in a process called "fining."  It is improbable that you can form
>tektites without a period of prolonged heating (volcano is the perfect
>suspect).
>
>This may sound arrogant, but the vast body of techinical literature since
>the late 1980s cheerfully ignores the physics of glass formation--that's
the
>heart of the tektite debate as I see it and why some researchers simply
>think linking tektites and impactites together is stupid.  They were not
>formed by the same process.  Hence, tektites are most likely not
impactites!
> Also, the volcanic structures observed in Muong Nong (layered) tektites by
>Von Koenigswald, O'Keefe, Futrell, Lowman have yet to be explained by
impact
>processes.
>
>I am hoarse from debating this point, but it will take a long time before
>scientits reexamine this problem.  In the meantime, you have my
perspective.
> The BEST current discussion of this problem is in Hal Povenmire's book
>"Tektites, a Cosmic Paradox" which cab be orded through Michael Blood's
>meteorite Web site and elsewhere.
>
>
>
>LOUIS VARRICCHIO
> Environmental Information Specialist &
> Producer/Writer, "Our Changing Planet"
>  (Visit OCP-TV on the Web at: www.umac.org/ocp)
>  Upper Midwest Aerospace Consortium
>  Odegard School of Aerospace Sciences
>  University of North Dakota
>  Grand Forks, N.D. 58202-9007  U.S.A.
>    Phone: 701-777-2482
>    Fax: 701-777-2940
>    E-mail: varricch@umac.org (in N.D.); morbius@together.net (in Vt.)
>
>"Behind every man alive stand thirty ghosts, for that is the ratio by
>which the dead outnumber the living. Since the dawn of time, a hundred
>billion human beings have walked the planet Earth." -- Arthur C. Clarke
>
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