[meteorite-list] Diogenite Nomenclature

From: barrat at univ-brest.fr <barrat_at_meteoritecentral.com>
Date: Sat, 15 Sep 2012 20:44:58 +0200
Message-ID: <1347734698.5054ccaa13be6_at_webmail-sdt.univ-brest.fr>

Hi,

the "problem" of the taxonomy of diogenites has been discussed recently in this
paper:

Andrew W. BECK and Harry Y. McSWEEN Jr (2010),Diogenites as polymict breccias
composed of orthopyroxenite and harzburgite, Meteoritics & Planetary Science,
Volume 45, Issue 5, May 2010, Pages: 850?872,
 DOI: 10.1111/j.1945-5100.2010.01061.x

The authors have proposed an adaptation of the classical classification of
terrestrial ultramafic rocks. I agree with their suggestions. Depending of the
proportion of olivine, harzburgitic diogenites and dunitic diogenites can be
defined.

The difficulty of the classification of diogenites is the size of the samples
used by classifiers. These lithologies are often extremely heterogeneous, and it
is often not possible to determine accurately the proportion of olivine using a
single polished section. Anyway, the problem of taxonomy is not a critical
scientific issue. Of course, it is important to determine the abundance of
olivine in a diogenite, but this proportion does not change the interpretation
we have on these rocks. At present, all the diogenites which have been
investigated in depth, are cumulate rocks, certainly coming from a number of
intrusions. These intrusions contain certainly different types of rocks,
including regular diogenites and olivine bearing diogenites. For example, trace
elements indicate that NWA5480 and Tatahouine come probably from the same
intrusion... Not from the mantle of the parent body.

Cheers

Jean-Alix



Selon Greg Hupe <gmhupe at centurylink.net>:

> Dear List Members and fellow diogenite enthusiasts,
>
> I talked with Tony Irving this morning regarding the use of 'Olivine
> Diogenite' in classifications and abstracts. I have been enlightened to the
> ever evolving diogenite classification scheme. Seems a new 'pigeon hole' has
> been created due to new meteorites which are comprised of mostly olivine, the
> Dunite meteorites. Find below Tony's reply and link to an abstract that
> discusses their proposed, and more accurate separation of the Diogenite
> meteorites.
>
> Best Regards,
> Greg Hupe
>
> Begin forwarded message:
>
> > Hi Greg:
> >
> > Here is a link to the abstract for our presentation in London last year.
> Most people seem to like this proposed scheme
> http://www.lpi.usra.edu/meetings/metsoc2011/pdf/5223.pdf ... [NWA 1877, NWA
> 5480 and other similar meteorites] would now be harzburgitic diogenites, but
> olivine diogenite is still OK as a general term. The nature of nomenclature
> is that it evolves with the need to encompass new specimens, and we have
> mostly NWA and private collectors to thank for that.
> >
> > Cheers,
> >
> > Tony
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Received on Sat 15 Sep 2012 02:44:58 PM PDT