Geology Reference
In-Depth Information
Polymict eucrite
1425 g
Found January 20, 1977
6.6 × 7.8 × 4.3 cm
Weathering = A
from being near the surface of the asteroid. Clasts can represent a variety
of unrelated basaltic rocks of a broad range of cooling histories. The
matrix contains fragments of all lithologies and can contain glassy regions
and dark fine-grained lithologies. These eucrites are called polymict due
to the presence of multiple igneous lithologies.
4
Diogenite
Howardite
Polymict eucrite
“Brecciated” eucrite
Cumulate eucrite
Other eucrite
B001
L010
Porno
Stan
3
ALH-pairing group
2
L002
1
N240
Y192
Y200
Y032
N461
0
0
4
8
12 6
MgO (wt%)
20
24
28
32
Plate 57
MiNERALogy
SigNiFiCANCE
The ALH polymict eucrites contain clasts of plagioclase-
pigeonite basalt (variety of textures), dark fine-grained
clasts, and mineral fragments of plagioclase and pyroxene.
Clast plagioclase ranges from An
83
to An
92
, and the
pyroxenes are orthopyroxene, pigeonite, and augite with
Mg# between 0.3 and 0.7. Mineral fragments in the
matrix include plagioclase, pyroxene, tridymite, chromite,
ilmenite, and FeNi metal.
The ALH pairing group comprises 14 different samples
with a combined mass of 4.2 kg. it represents a large
well-characterized mass of material that is representative
of the brecciated basaltic crust (left, [427]) of the eucrites'
parent body (asteroid 4 Vesta). The material from this
group helped to shape our understanding of the
differentiation of 4 Vesta. it has been studied by dozens
of scientists using a broad range of analytical techniques
and approaches.
References [413-427]
