[meteorite-list] Feldspar minerals in the inclusions in earthly/lunar basalts

From: mafer_at_domafer.com <mafer_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:14 2004
Message-ID: <016401c2879e$f5ae0440$6401a8c0_at_vs.shawcable.net>

Hi Bob
The most probable reason I can think of is that the feldspars that are found
in meteorites are not typically vary large. By that I mean in some fashion,
large enough to see with the unaided eye, while those found in terrestrial
rock are, even when small, distinguishable by the eye. The fizz test is
equally scaled, and so what these labs are most likely saying is that if you
can see it fizz, then the crystals of feldspar are too large and or too
numberous to match the known concentrations of the same in meteoritic
materials. I may be wrong, but this is what I see in meteorites. I'm not a
geo-chemist, just trying for my BA in Geology, but I hope this helps a
little.
Mark


----- Original Message -----
From: Robert Verish <bolidechaser_at_yahoo.com>
To: <bsoerhei_at_online.no>
Cc: Meteorite-list Meteoritecentral <meteorite-list_at_meteoritecentral.com>
Sent: Friday, November 08, 2002 5:17 PM
Subject: [meteorite-list] Feldspar minerals in the inclusions in
earthly/lunar basalts


> --------------- Original Message ---------------
> [meteorite-list] Feldspar minerals in the inclusions
> in earthly/lunar basalts
> Bjørn Sørheim bsoerhei_at_online.no
> Fri, 8 Nov 2002 17:22:40 +0100 (MET)
>
> Hello list,
>
> ++++SNIP!!++++
>
> But the question I have is concerning the feldspar
> inclusions.
> I wonder what span in %-values there is of Albite(Na)
> vs. Anorthite(Ca) in the plagioclase of these
> inclusions in the lunar basalts compared to earthly
> basalts?
> On the practical side (testing) - would a lunar
> basaltic feldspar inclusion fizzle in (cold)
> hydrocloric acid (HCl)?
> Would a (Vesta) eucrite inclusion have the same values
> as its lunar counterpart?
>
> Regards,
> Bjørn Sørheim
> -----------------------------
>
> Good Questions Bjørn,
>
> Regarding your basalt's Ca-rich plagioclase
> phenocrysts
> --
> I just had a specimen turned-down for formal analysis,
> because it failed the very same acid test that you
> described. My immediate question was, How do we know
> those aren't lunar anorthosite grains that have
> undergone a great deal of terrestrial weathering, and
> that have been altered to clays and calcium carbonate?
>
> I'm still waiting for an answer to that question.
>
> So, if there is a geochemist out there on the List
> that knows why an acid test fizzle is [always] a
> diagnostic contra-indication for a plag-bearing
> meteorite, would they please explain to me "why?".
>
> Bob V.
>
>
>
>
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Received on Fri 08 Nov 2002 10:20:30 PM PST