[meteorite-list] Impact Melt meteorites

From: tett <tett_at_meteoritecentral.com>
Date: Thu Apr 22 09:47:14 2004
Message-ID: <3BFF9113.85CCFC1D_at_bmts.com>

Bernd and List,

Are there any good references which describe the visual characteristics of impact melts? A quick glance through Norton's and McSween's books
show no references in the indices.

I have a few Saharan meteorites which have large gray sections which are very homogeneous showing no visible chondrules. These sections are
boarded by distinct chondrule laden sections. What should I look for to determine if these meteorites are in fact impact melts?

Cheers,

Mike Tettenborn

Bernd Pauli HD wrote:

> Michel Franco a écrit:
>
> > ... was wondering if there are 2 main classes of impact
> > melt meteorites, as one could think Impact melt m. of
> > achondritic origin and impact melt m. of chondritic
> > parent body.
>
> Bonsoir Michel, hello List,
>
> Here is a database survey of 12 Non-Antarctic meteorites that
> are classified as impact melt meteorites. Some new ones may
> still be missing from this list as I am not "on track" with my
> update chores :-(
>
> Best wishes,
>
> Bernd
>
> Calcalong Creek - LUN - impact melt breccia;
> Cat Mountain - L5 - impact melt breccia; vesicles;
> Chico - L6 - impact melt breccia; copper; S6;
> Dar al Gani 241 - imb - impact melt breccia
> Dar al Gani 242 - imb - impact melt breccia
> Dhofar 025 - LUN - anorthositic impact melt regolith breccia;
> Happy Canyon - EL6 - EL6/7 (S2); impact melt breccia(?); vesicles;
> Madrid - L6 - veined; impact melt breccia
> Norton County - AUB - fragmental breccia;
> clastic matrix (igneous and impact melt)
> Roosevelt County 085 - L4 - RC,S4; W2; impact melt
> Sahara 00215 - L - W3/4; impact melt breccia;
> Shaw - L6 - Dodd: L7; complex impact melt breccia;
>
> US-Antarctica:
>
> ALHA81011 - eucritic impact melt breccia
>
> EET 99443: "The section exhibits isolated pyroxene and plagioclase
> grains up to 0.5 mm. The section contains one part in which the
> groundmass is finely comminuted pyroxene and plagioclase grains,
> while the groundmass in the other is a fine-grained, lath-like
> structure suggestive of an i m p a c t m e l t . The meteorite
> is a howardite (AMN 24-1, Feb 2001, p. 11).
>
> MET 00427: "The section shows ...a single millimeter-sized
> i m p a c t m e l t spherule. The meteorite is a howardite
> (AMN 24-2, September 2001, p. 19).
>
> QUE 99059 is almost certainly paired with the trio QUE 94204/
> 97348/97289, ... These meteorites are unusual aubrites or
> enstatite chondrite impact melt rocks (AMN 24-1, Feb 2001, p. 13).
>
> References:
>
> METZLER K. et al. (1994) ALHA81011 - A eucritic impact melt
> breccia formed 350 m.y. ago (abs. Meteoritics 29, 1994, 502-503).
>
> METZLER K. et al. (1995) Impact melt rocks and granulites
> from the HED asteroid (abs. Meteoritics 30, 1995, 547).
>
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Received on Sat 24 Nov 2001 07:22:43 AM PST