[meteorite-list] NWA 2736 - Aubrite or not??

From: Adam Hupe <raremeteorites_at_meteoritecentral.com>
Date: Sat Feb 25 15:00:58 2006
Message-ID: <08bb01c63a45$4170be20$6401a8c0_at_c1720188a>

I agree with everything you said, David. These are exactly the issues that
are being sorted out. I think Isotope testing will answer several of these
questions. By definition, I don't think anybody could call NWA 2736 a true
Aubrite. Like I said, it is like trying to fit a round peg into a square
hole. A few qualifiers were put into the description of NWA 2736 in order to
make an awkward fit. On others, the authors left them ungrouped in order to
stay away from pigeonholing.

Got to go, take care,

Adam


----- Original Message -----
From: "David Weir" <dgweir_at_earthlink.net>
To: "Adam Hupe" <raremeteorites_at_comcast.net>
Cc: <meteorite-list_at_meteoritecentral.com>
Sent: Saturday, February 25, 2006 11:46 AM
Subject: Re: [meteorite-list] NWA 2736 - Aubrite or not??


> Hey Adam,
>
> If different types of material from a single PB forms a metamorphic
> continuum as has been published recently, what are the exact parameters
> for these different groupings; e.g., chondrite, metachondrite, primitive
> achondrite, achondrite, stony-iron, iron. I have not yet seen the
> particulars for where one stops and the other begins, but a continuum is
> not given to such deterministic lines in the true nature of things.
>
> An aubrite by most definitions would be associated with the achondrite
> (igneously derived) portion of this continuum, but a primitive
> achondrite and even a metachondrite could be close enough that it would
> take in-depth analyses to distinguish between them, and some labs don't
> even recognize all of these metamorphic divisions to begin with. At
> least one aubrite is classified as a stony-iron (Mt. Egerton), and one
> enstatite achondrite is more like an iron (Horse Creek).
>
> I suppose the classification of NWA 2736 as an aubrite may be acceptable
> given the fact that an aubrite is not a term referring to any one
> particular PB; e.g. Shallowater is from a unique aubritic PB, and there
> are several other ungrouped enstatite-related meteorites such as Itqiy,
> Zaklodzie, NWA 1235, and NWA 1839 just to name a few. I think O-isotopic
> composition data is needed for all of these enstatite-related rocks, and
> of course more samples of such meteorites will hopefully be found in
> order to answer some of these PB source questions and to better
> distinguish their petrologic history for an accurate classification
> assignment.
>
> David
Received on Sat 25 Feb 2006 02:54:13 PM PST