[meteorite-list] Re: Breccia formation

From: Dave Harris <entropydave_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:44 2004
Message-ID: <00b001c197bc$8f8fdb20$849f0050_at_default>

Bernd,
You are remarkable!
I would love to use your library!
Thinking of moving to Brighton?
:-)


----- Original Message -----
From: "Bernd Pauli HD" <bernd.pauli_at_lehrer1.rz.uni-karlsruhe.de>
To: "Dave Harris" <entropydave_at_ic24.net>
Cc: "metlist" <meteorite-list_at_meteoritecentral.com>
Sent: Monday, January 07, 2002 8:40 PM
Subject: Breccia formation


> Dave Harris wrote:
>
> > So, can I assume that the meteorite, prior to ejection from the parent
> > asteroid was already a brecciated rock lying on the surface or embedded
in
> > the lithosphere, or does brecciation occur when the regolith is pounded
by
> > an impact, fusing together all the different rocks lying around on the
> > surface of the planetoid?
>
> Hello again,
>
> JÄCKEL A. et al. (1998) Textural and mineralogical differences
> between LL-chondritic fragmental and regolith breccias
> (Meteoritics 33-4, 1998, A077, excerpts):
>
> "Essentially, two different types of breccias can be distinguished:
> regolith breccias and the more abundant fragmental breccias. Regolith
> breccias derive from the uppermost surface material of the parent
> bodies, and contain significant concentrations of solar-wind-implanted
> noble gases as well as preirradiated mineral grains. Fragmental breccias
> represent material that was shielded from irradiation, and do not
> contain solar-wind-implanted noble gases."
>
> "The chemical compositions of the matrix olivines in regolith breccias
> vary, unlike the composition of matrix olivines in fragmental breccias.
> The occurrence of clasts showing different olivine compositions
> indicates that equilibrated and unequilibrated lithologies were mixed
> together by impact events after the equilibrated and recrystallized
> fragments were formed by thermal metamorphism."
>
>
> Best wishes,
>
> Bernd
Received on Mon 07 Jan 2002 03:47:42 PM PST