[meteorite-list] New Arizona Meteorite!

From: tracy latimer <daistiho_at_meteoritecentral.com>
Date: Mon Feb 14 20:29:19 2005
Message-ID: <BAY102-F2935DE7D94BED4C180EA89CA6B0_at_phx.gbl>

I can't say this with any definiteness, but I don't believe any "new" (i.e.,
unweathered) chondrules show signs of concentric layering, only ones that
have been exposed to Earth's atmosphere and have suffered degradation from
moisture. I can't point to any example I have seen that shows anything like
growth rings that have definitely formed outside Earth conditions; they all
imply forming at once, rather than in successive buildups. This completely
ignores the question of armored chondrules, however.

Tracy Latimer
>
>ON THE ORIGIN OF CHONDRULES
>Norm and List,
>Please excuse my ignorance for putting forth this question but as a
>relative "newbe" to meteorite collecting, I hope you will entitle me to
>this query.
>I came across the term "accretionary lapilli" also called "volcanic
>pisolites" in Dorothy Ferris Lapidus 1987 edition of "The Facts on File
>Dictionary of Geology and Geophysics.
>If you bear with me I'll quote " these are shperoidal concentrically
>layered pellets composed mainly of vitric dust and ash, usually between 2
>and 10 mm in diameter. They are formed primarily through the accretion of
>ash and dust by condensed moisture in eruption clouds. Formless nuclei of
>coarse particles fall through the fine debris and acquire shells of
>progressively finer ash. These concentric shells indicate the increasiing
>temperature and decreasing humidity of the cloud at lower levels.
>My question is, does the process described above provide any
>anology("something similar but different") to the origin of chondrules.
Received on Mon 14 Feb 2005 08:28:54 PM PST