[meteorite-list] metachondrite

From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Thu, 21 Oct 2010 20:22:06 +0200
Message-ID: <015601cb714c$df180e60$9d482b20$_at_de>

Well, of course it won't,
(like the PACs are in principle neither a group...)
but chemically and from the isotopes, those 7-PAC-Metas-Howevers are evolved
chondrites of the respective chondrite groups.
Chondrites with no chondrules anymore. But if I hear "achondrite", I'm
thinking to HEDs and meteorites derived from differentiated stuff.
Hence they are neither "ungrouped", we can group them definitely to the Ls,
to the Hs, ect.
And primitive achondrites, well those 7-Meta-PAC-Howevers - they are the
most metamorph, most elquilibrated (former) chondrites, hence quite the
opposite of "primitive".
Traditionally, in my drawer labeled "PAC", there are sitting already the
LOD/ACAP/WIN-boys inside. And they tussle always with those Ls, Hs, LLs,
CVs, which just baked a little longer in their parent bodies, than the
4ers,5ers,6ers.
(Uh and horribile dictu, in these LODs, ACAPs, WINs - called PACs, there are
sometime chondrules and relict chondrules found!).
Quietude into that drawer I could bring, if I put them all inside and would
write "metachondrite" on the label, but always remembering, that each of
them is cut from the cloth of his own group.
(Or to say it else, they are rather ex-chondrites for me, than a-chondrites
:-)
Or to say it else again, for me it's more precise, to call the L-meta,
H-meta, LL-meta ect... than to lump them all together in the bucket labeled
PAC).

But Jeff, you're naturally right - that is all only for my private domestic
use.
And I need simplifications, as the simple mind I am.
As told, we are only laymen.
We're the delivery boys of the very stones - the more weird, the better -
though the papers about, the scientists have to write.

Apropos "weird" - Weir D. gives as always good information about that
complex:
http://www.meteoritestudies.com/

Best!
Martin


-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von Jeff
Grossman
Gesendet: Donnerstag, 21. Oktober 2010 19:39
An: meteorite-list at meteoritecentral.com
Betreff: Re: [meteorite-list] metachondrite

  Even if the term "metachondrite" comes into use, it will not be the
name of a meteorite group. It is semantically similar to the terms
chondrite and achondrite, which are descriptive of the overall texture
of a rock. Each of these terms encompasses objects from many parent
bodies. And please don't think that the term "primitive achondrite" is
incoherent. It is a very well-defined term, with an abundant scientific
literature behind it. In fact, Irving et al. (metsoc abstract) suggest
that metachondrite is essentially a synonym for PAC! Nor is the term
"ungrouped" incoherent. This is a very precise term, meaning that the
meteorite does not belong to an accepted group. If one adopts the term
metachondrite, expect there to be metachondrite-ung classifications
appearing.

Jeff
Received on Thu 21 Oct 2010 02:22:06 PM PDT