[meteorite-list] Re: CAIs in Allende

From: entropydave <entropydave_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:14 2004
Message-ID: <005b01c0fce9$98911b80$4da989d4_at_default>

Bernd,
You stun me!
Thank you!!
Blimey, you're clever!!!
very best!

--
In gentle decay,
d.
http://www.meteorites.ic24.net/index.html
http://www.thc.u-net.com/davethc1.htm
"I have a proof that x^n+y^n=z^n never has integer solutions for n>2.
However, it won't fit into my signature file...."
----- Original Message -----
From: Bernd Pauli HD <bernd.pauli_at_lehrer1.rz.uni-karlsruhe.de>
To: entropydave <entropydave_at_ic24.net>
Cc: metlist <meteorite-list_at_meteoritecentral.com>
Sent: Sunday, June 24, 2001 8:51 PM
Subject: CAIs in Allende
> Dave wrote:
>
> > I notice that in my Allende slice, some of the CAIs appear to be zoned,
that
> > is they have a roughly central area of a greyer material than the rest
of
> > the CAI that surrounds it.  Can any of you erudite people afford me an
> > explanation as to how the gray inner region varies
chemically/lithologically
> > to the outer portion.
>
> Hi Dave and List,
>
> RUZICKA A.M. et al. (1994) Origin of CAI rims by vaporization and
> metasomatism (abs. Meteoritics 29-4, 1994, 526):
>
> On their margins, most Ca, Al-rich inclusions (CAIs) contain thin "rims"
> comprised of multiple mineral layers. Previous work has shown that the
> bulk composition of the rims can be explained by a combination of
> vaporization during flash heating of the CAIs and a metasomatic event*
> that involved an influx into CAIs of Mg and Si. The layering structure
> of the rims may have formed by a coupled reaction/diffusion process
> during metasomatism, similar to that which produced mineralogically
> zoned olivine coronas in mesosiderites ... Rim layers consist mainly
> of spinel, forsteristic olivine, Ti, Al-rich pyroxene, Al-rich diopside,
> melilite, anorthosite, and lesser amounts of perovskite, Fe-Ni metal,
> and feldspathoids.
>
> * Metasomatism:
>
> A series of metamorphic processes whereby chemical changes occur
> in minerals or rocks as a result of the introduction of material,
> often in hot aqueous solutions, from external sources.
>
>
> Best wishes,
>
> Bernd

Received on Sun 24 Jun 2001 04:09:37 PM PDT