[meteorite-list] Galim (a) and Galim(b) question??????

From: Michael L Blood <mlblood_at_meteoritecentral.com>
Date: Thu Apr 22 10:10:02 2004
Message-ID: <BAB1BA17.50B9%mlblood_at_cox.net>

In the words of Rosanna Rosannadanna, "Oh. Never mind." Michael

on 4/3/03 6:42 AM, rochette at rochette_at_cerege.fr wrote:

> Dear dave
> here is the answer:
> Title:
> The Galim LL/EH polymict breccia: Evidence for impact-induced exchange
> between reduced and oxidized meteoritic material
> Authors:
> Rubin, Alan E.
> Journal:
> Meteoritics, vol. 32, pages 489-492
> Publication Date:
> 07/1997
> Origin:
> METIC
> Bibliographic Code:
> 1997M&PS...32..489R
> Abstract
> Galim is a polymict breccia consisting of a heavily shocked (shock stage
> S6) LL6 chondrite [Galim (a)] and an impact-melted EH chondrite [Galim
> (b)]. Relict chondrules in Galim (b) served as nucleation sites for
> euhedral enstatite grains crystallizing from the impact melt. Many of the
> reduced phases typical of EH chondrites (e.g., Si-bearing metallic Fe-Ni;
> Ti-bearing troilite) are absent. Galim (b) was probably shock-melted while
> in contact with a more oxidized source, i.e., Galim (a); during this event
> Si was oxidized from the metal and Ti was oxidized from troilite. Galim (a)
> contains shock veins and recrystallized, unzoned olivine. The absence of
> evidence for reduction in Galim (a) may indicate that the amount of LL
> material greatly exceeded that of EH material; shock metamorphism may have
> taken place on the LL parent body. Shock-induced redox reactions such as
> those inferred for the Galim breccia appear to be restricted mainly to
> asteroids because the low-end tail of their relative-velocity distribution
> permits mixing of intact disparate materials (including accretion of
> projectiles of different oxidation states) whereas the peak of the
> distribution leads to high equilibration shock pressures (allowing
> impact-induced exchange between previously accreted, disequilibrated
> materials). Galim probably formed by a two-stage process: (1) accretion to
> the LL parent body of an intact EH projectile at low relative velocities,
> and (2) shock metamorphism of the assemblage by the subsequent impact of
> another projectile at significantly higher relative velocities.
>
> conclusion: a single fall can be made of different classes. The fall place
> is heavily vegetated so there is no chance that accidentally an older fall
> (b) was found in the strewnfielf of a)...
>
>
> Pierre
>
>
>
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Received on Thu 03 Apr 2003 01:14:48 PM PST