[meteorite-list] Allende inclusion help!!!

[bernd.pauli at paulinet.de]

Hi Tom, McCartneyTaylor, and List,

> Hey List, this Allende has an inclusion and I really would like to know 
> what it is so I am sending this ebay link, not to show you this neat
> meteorite, but to try to find out what you all think this inclusion could
> be, I am dieing of curiosity!

> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3239&item=6523135359&
> rd=1

It is either a carbonaceous inclusion, a CO3 - a CO3 carbonaceous chondrite
within a CV3 carbonaceous chondrite. Maybe you remember the piece that the
Hupes offered on EBay until a few days ago and/or the pieces Eric Olson sold
in February/March 2004.

.. or, as McCartneyTaylor just wrote: an Allende "dark inclusion".

> Still, I have no idea what the real mineralogy is...

HEYMANN D. et al. (1987) Carbon in dark inclusions of the
Allende meteorite (Meteoritics 22, 1987, 3-15, excerpt, p.3):

Dark inclusions (DI's) are among the major petrographic components of the
Allende meteorite; the others being: a fine-grained matrix of predominantly
olivine, chondrules, and irregular inclusions. DI's have also been called fine-
grained xenoliths. Their dimensions can be millimeters, and even centimeters.

The larger DI's can usually be recognized easily on cut surfaces of the Allende
meteorite because they appear darker than their surrounding areas, and are
often poor in chondrules or large irregular inclusions. 

Fruland, Clanton, and Walton (1977) recognized three types of DI's:

(1) a black fine-grained matrix with few clasts and rare chondrules,
(2) a discontinuous, black, fine-grained matrix with abundant clasts
    and chondrules, and
(3) densely packed clasts and chondrules with a small percentage
    of discontinuous interstitial matrix. 

Fruland (1978) reports SEM petrography on two lensoidal DI's: both display
sharp boundaries with the lighter Allende matrix; one has an approximately
60 µm wide, but discontinuous rim of Ca-rich silicates. Fruland notes that
these two DI's *consist primarily of silicates, metal, and sulfides*, with
grain sizes up to about 40 µm; hence, *coarser than matrix*. Fruland also
notes: "Many clasts have a *dark 'accretionary' halo*." 


Best wishes,

Bernd