Geology Reference
In-Depth Information
L6 chondrite
2361.43 g
Found December 13, 1985
15.0 × 10.0 × 11.5 cm
Weathering = A
one of the most common meteorite types in world collections are L6
chondrites, thought to be from an S-type asteroid parent body that had
undergone metamorphism to near 900 °C. Many L chondrites show
evidence for shock events and shock heating, so a more in-depth under-
standing of shock effects would be relevant to most equilibrated ordinary
chondrites.
,O
,I
ICM
ALH85017
80
10
4
Fujiwara et al.
4.78
×
10
6
erg/g
8.23
×
10
6
erg/g
2.28
×
10
7
erg/g
6.46
×
10
7
erg/g
Particulate targets
Lunar basalt 75035, <45
μ
m
Lunar basalt 75035, <45-75
μ
m
Lunar basalt 75035, <100 -150
μ
m
Dunite, 10 0-150
μ
m
Bronzite/plagioclase, 100-150
μ
m
L6 chondrite ALH85017, 120-250
μ
m
70
60
10
3
50
Massive targets
Lunar basalt 75035
Lonar lake basalt
Dunite
40
10
2
30
9
6
20
10
1
10
2
5
7
8
To tal
3
1
4
0
0
10
0
10
-6
10 0 0 0
Shock stress, GPa
50
60
70
80
90
100
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
Fragment mass/M
s
Plate 6
MiNERALogy
SigNiFiCANCE
ALH 85017 is a polymict breccia containing lithic and
monomineralic clasts, set in a fine-grained matrix of
~15% of the rock. The lithic clasts are commonly poly-
mict, clastic breccias of varying grain sizes and modes.
There are also irregular fragments of metal and sulfide,
and a few relict chondrules. olivine is Fa
24
, orthopyrox-
ene is Fs
20
, clinopyroxene is En
47
Fs
7
Wo
46
, feldspar is An
14
,
and there is minor Fe-Ni metal (4%), troilite (3%),
chromite, and apatite.
A detailed study of the fragmentation dynamics of ALH
85017 was carried out in the high-velocity impact facility
at JSC. A 500-g sample was fragmented by multiple
impacts down to a grain size of 125-250 μm fines (right,
[27]), which were subsequently subjected to reverberation
shock stresses of 14.5-67 gPa to understand the melting
behavior of porous, unconsolidated, chondritic asteroid
surfaces during meteorite impact (left, [28]). The results
have implications for both shock melting and the produc-
tion of nano-phase iron during space weathering.
References [27, 28]
