AW: [meteorite-list] Anomalous and Ungrouped Ordinary Chondrites

From: Norbert Classen <trifid_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:32 2004
Message-ID: <NCBBKMGDKLMGIBALJOFCMECEDMAA.trifid_at_timewarp.de>

Hi John, and list,

As to the ungrouped HaH 180, and Deakin 001, it has been suggested
that both represent samples of a new and previously unsampled parent
body. If that holds to be true, they will never get a LL or L
classification. Ungrouped just means that a sample can't be
assigned to any of the established groups, and that means also
that they do most probably represent a unique parent body. Now,
if we find three more meteorites like HaH 180, or Deakin 001,
scientists will most likely create a new group, and then these
samples won't be ungrouped, any longer.

The term "anomalous" is used for meteorites that actually can be
assigned to an existing group, but that differ in some aspects from
the other known members of that group. Thus, HaH 180 isn't anomalous,
it's simply ungrouped.

Short: an ungrouped chondrite most probably stems from an asteroid
that hasn't been sampled so far. An anomalous LL, for example, is
most probably from the LL parent body/asteroid, but it differs from
the other LL members in some respect. The petrologic grades have
nothing to do with that, and of course an ungrouped chondrite can
be a 3.5, or a plain 6.

Hope this helps ;-)

Best,
Norbert

A puzzled John wrote:

> Hello all,
>
> I've always been intrigued but puzzled about the classification of a few
> ordinary chondrites into the black hole of assigned classification
> names...ungrouped and/or anomalous. Some are specified with petrologic
> assignments and others without. Ebay on occasion offers us Hah
> 180 that is classified as an anomalous 3.5 ordinary chondrite and
> Dhofar 535 that is classified as ungrouped, and without a petrologic
> designation in its' description. According to David's site below...Hah
> 180 is similar to Deakin 001. And there maybe others I am not thinking
> of. Oxygen isotopes and weathering seem to be some of the key factors...
> and as stated on David's site they may come from a proximity close to
> where enstatite chondrites were formed, and in my opinion their appearance
> makes them at least look like some of the EL3's out there.
>
> Does anyone know what the latest theory is for these and will
> they one day
> get an official LL3 to 3.5 anomalous label which would finally
> give them a
> home? Seems to me to call them anything else puts them/keeps them in
> classification limbo.
Received on Sun 19 Oct 2003 06:08:03 PM PDT