Armando , Bernd, & all,
"Porphyritic" is a textural term. In terrestrial
igneous rocks it results from multiple-stage cooling,
but I see no reason why you can't run it backwards
with incomplete melting. If olivine is the common
phenocryst phase, this would make sense in that it has
an extremely high melting point. The glass would
reflect the lower melting point silicates, while the
olivine and magnetite remain, yielding a porphyritic
texture.
Cheers,
Norm
(http://TektiteSource.com)
--- [EMAIL PROTECTED] wrote:
> > What can be the reason for this messages to appear
> with a delay of 32h? AA
>
> > porphyritic? Are you sure? The meteorites cool
> down in a single stage, I believe
>
> Hi Armando and List,
>
> No idea why there is such a delay! Furthermore, I do
> not know for sure about the
> "porphyritic" thing. This was not my personal
> comment but I only quoted from the
> article by Genge and Monica Grady. But Dr. Monica
> Grady is a List member, so,
> time permitting, Dr. Grady might perhaps find some
> spare moments to answer your
> question much more competently than I ever would be
> able to!
>
> Best wishes,
>
> Bernd
>
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