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Tektite Questions



The following is paraphrased from the late D.R. Chapman of NASA's 1971
paper on tektites--

Age data from both K-Ar and fission track methods indicate that two
craters may have formed with two tektite showers--the Ries crater in
Germany (with the moldavites) 15 million years ago and the Bosumtwi
crater in Ghana (with the Ivory Coast tektites) 1 million years ago.
The notion of terrestrial origin for these tektites conflicts with
aerodynamic and trajectory evidence of the australasian tektites (where
no crater has been found so far).  

Rocks with the same major and minor element composition as Ivory Coast
tektites have not been found at Bosumtwi; likewise rocks of moldavite
composition have not been found at Ries crater.  More devistating to the
idea of a terrestrial origin for Ivory Coast tektites is the discovery
of Ivory Coast microtektites in deep-sea deposits 1300 km from Bosumtwi.
This distance is too short to have produced any ablation droplets of
tektite glass, yet is much too far for these objects to have traveled
through the earth's atmosphere either by winds or by ballistic
trajectories; the Bosumtwi impact is too small to have temporarily
removed the earth's atmosphere.

How could tektites possibly come from the Moon?  

Chapman believed tektites to be ejecta from lunar impacts (not volcanic
ejecta as others claim); using computers, he traced the australasian
strewn field entry patterns back to the crater Tycho's extensive Rosse
ray.  

The idea of tektites coming from the Moon's highlands is not
incompatible with Chapman's lunar impact hypothesis: though comprised of
mainly basic material, the highlands may contain acidic intrusions.
Maybe there's a "missing link" rock type on the Moon--not readily found
and far from Apollo's narrow landing sites--which is somewhere in
composition between highland anorthosite and the high calcium australite
tektites?  How so?  Well, chemically, there's a hint that you could
eventually get australite tektites made from anorthosites since the SiO2
content of australites drops from 80% to 60% with a trend downward into
the anorthosite range (46% SiO2)! 



> -----Original Message-----
> From:	ALMitt@kconline.com [SMTP:ALMitt@kconline.com]
> Sent:	Friday, August 07, 1998 4:38 AM
> To:	meteorite-list@meteoritecentral.com
> Subject:	Re: Tektite textures
> 
> Hi to all,
> 
> The tektite discussion is an interesting one and one I know little
> about. Some 
> of the information I have picked up and that has lead me to believe
> they are an 
> artifact from the Earth are these arguments below. Keep in mind that I
> will 
> consider anything that seems logical or makes sense.
> 
> The idea of the lunar origin was dropped primarily because of a lack
> of silica 
> on the moon and the lack of tektites found there.
> 
> Some moldivites found in czechoslovakia have material sampling Ryes
> (sp?) 
> Crater in Germany, suggesting it is the source of those tektites.
> 
> Air found in a number of tektites samples the Earths atmosphere or
> show a 
> signature that the gases trapped inside are from Earth. How did it get
> there?
> 
> No doubt these glasses have been through our atmosphere but do we
> really 
> understand the dynamics of how they are created? Could they be the
> result of a 
> double impact event on Earth?
> 
> Just another log for the fire.
> 
> --AL
> 
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