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Re: Glass bombs impactite or tektite


-----Original Message-----
From: Michael Blood <mblood@access1.net>
To: Darryl S. Futrell <futrelds@gte.net>
Cc: Gaetan Cormier - Meteorites & Tektites <shattercone@videotron.ca>;
meteorite-list@meteoritecentral.com <meteorite-list@meteoritecentral.com>
Date: Saturday, March 20, 1999 3:20 AM
Subject: Re: Glass bombs impactite or tektite


Michael,
    I was way too vague with my 1st comment on Ries bombs.
    Did you read my R & G tektite origin article?  There was a stack of free
copies at the tektite party.  If you would, you might better understand what
I was trying to say.  Can send you a copy.
    I never said the Ries bombs (fladle) are tektites.  Of course they are
classified as impact melts, but impact melts can contain varying amounts of
the projectile that made the crater.  (Wabar & Henbury impact melts, for
example, can contain millions or more of microscopic NiFe spherules, and
sometimes even intact fragments of their NiFe projectiles.)  This is missing
at Ries.  Instead, the Ries impact melts can contain varying amounts of
recycled tektite family glasses from the glass projectile that I'm convinced
(for good reason) made the Ries crater.
    The numerous "impact" scientists refuse to accept that any impact
craters could have been formed by "glass" projectiles, but that doesn't mean
it isn't so.  Darwin and Zhamanshin are a few of the others.
   Generally, all natural terrestrial glasses
(obsidians, fulgurites, real impact melts, etc.) devitrify over tens or
hundreds of  thousands of years.  But the Ries has glasses that are still
glassy after 14 million years.  That indicates that they probably contain
some % of tektite glass, as tektite glasses basically don't devitrify
(example, the 367 m.y. old Belgian microtektites) except when they have
become
contaminated by being remelted in a terrestrial impact, or have been through
some other extensive terrestrial reheating event.  Some tektite
glasses have compositions in the "ballpark" with terrestrial andesitic and
granitic glasses (ignoring the trace elements).  So, it's tempting for the
majority to assume certain Ries bombs & glasses mixed in with the breccias
are all melted from the Ries granitic bedrock.  Have a look at the still
very glassy Ries black melt in the March issue of Rock & Gem.  (It should
not have said "high-quality"- someone changed my caption.)  Any purely
terrestrial glasses mixed
in with the breccias in the matrix around the black blob devitrified long
ago.  I believe the black blob contains some % of tektite glass from the
tektite glass projectile.  I feel that any Ries impact melt bombs that are
still truly glassy could contain some % of the same.  I still don't know how
really glassy the Ries bombs can be, as I don't believe I have yet seen the
full range of quality.                Darryl Futrell
>
Darryl,
> I sometimes have Ries Crater Glass Bombs & have ALWAYS heard they were
>impact melt - NOT tektites. I have always thought they LOOK LIKE impact
>melt and NOT tektites - and, I have always sold them as impact melts and
>not tektites.
> As of this time, my opinion has not changed.
> Best wishes, Michael
>
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