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

From: rochette <rochette_at_meteoritecentral.com>
Date: Thu Apr 22 10:10:02 2004
Message-ID: <v04003a07bab1f6def18c_at_[193.49.98.39]>

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
Received on Thu 03 Apr 2003 09:42:22 AM PST