[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: tektite coloration
Hello Darryl, Calvin, and List,
Let me go on the record as a "neutral" skeptic with regards to the lunar origin of tektites. I believe some of our tektites definitely came from terrestrial target rock. I could better accept a multiple origin position than a single source. That is, we may have lumped together the natural glasses around the word into an "all or nothing category"-- but in reality, we need to allow for the possibility that we have grouped some very similar material, with very different origins, because they have shared the dynamics of atmospheric decent.
Now to my specific points. I an inclined to think that under conditions of high viscosity and low lunar gravity, a magma column would have a hard time differentiating before cooling to the point of solidifying. The process would take so long to sort, I expect to find that lunar glass would form only briefly if at all, before it crystallized into something less amorphous. Would there be someone who would tell me that "yes- but upon earth decent, it remelted and reverted to glass"? Or, are we saying that when the column was disrupted, it shot out like a cannon and incorporated any materials at the top of the column into what ever molten body there was below it?
Do we theorize this release was due to a supernormal, magmatic process under pressure from contraction of the surrounding rock as cooling continued- -or was it released under shock of a nearby large impact? Why would a molten body be so localized or otherwise so close to the lunar surface that is supposed to be thermally in the neighborhood of 20 above to 30 below C? Temperatures well under the melting point of silicates. (I have jumped to the conclusion, that in accordance with current lunar volcanism belief -- most lava flows on the moon ceased over a billion years ago, so a "normal" volcanic eruption would not have been the reason this material was ejected at lunar escape velocity).
Am I on an approach any where near what the lunar theory of tektite origins might hold?
Regards,
Elton Jones
"Darryl S. Futrell" wrote:
> Subject: tektite coloration
>
> Layered tektites contain many structures, both megascopic and microscopic,
> that are impossible to explain in any impact melt event, but are exactly
> what would be expected in the immediate vicinity (here, the pyroclastic
> microtektite-like blobs of glass would be hot enough to weld together) of a
> pyroclastic event on an atmosphere-free planetary body such as our moon.
> LDglasses are all composed of microtektite-sized blobs of silica glass that
> have been welded together. One of the other papers (other than the paper by
> O'Keefe and myself) in SILICA 96 again verifies this. I would be happy to
> send a free reprint of our illustrated LDg paper to anyone furnishing me
> with a snail mail address. It includes many references. Blue streaks in
> LDg represent enriched deposits of trace element volatiles deposited by the
> volcanic gases involved in this very unusual type of pyroclastic eruption.
> (I say very unusual because it may involve a massive deposit of cristobalite
> and/or tridymite xls at the top end of a differentiated magma column,) A
> very careful trace element analysis of this blue streak may show a slight
> enrichment of the guilty party or parties. D Futrell
----------
Archives located at:
http://www.meteoritecentral.com/list_best.html
For help, FAQ's and sub. info. visit:
http://www.meteoritecentral.com/mailing_list.html
----------
References: