Geology Reference
In-Depth Information
9
1
1 LAP 02205
2 LAP 02224
3 LAP 02226
4 LAP 02436
5 LAP 03632
6 LAP 04841
N NWA 4734
E NWA 032
F NWA 479
2
N
N
2
1
1
1
1
5
8
N
5
N
4
6
6
3
N
3
5
5
N
2
3
5
2
3
6
2
3
N
6
5
E
4
1
7
3
E
N
E
2
6
E
4
6
F
F
F
F
F
F
6
E
N
E
E
E
4
E
4
E
E
6
N
N
Subsamples of the NNL meteorites
50
52
54
56
Sc (ppm)
58
60
62
64
Figure 6.14.
Each LAP point represents a 35-mg subsample and each NWA point represents a 25-mg subsample, on average. The
six LAP basalts are indistinguishable in composition from each other and from NWA 4734 on any two-element plot such as this.
NWA 032 and NWA 479 are paired. NWA 032/479 is richer in olivine than LAP and, consequently, poorer in Sc and richer in Co
[
Zeigler et al
., 2005]. All data are from the Washington University INAA lab [
Fagan et al
., 2002;
Zeigler et al
., 2005].
12 and 15 basalts (3.1-3.4 Ga) [Table 6 of
S. R. Taylor
,
1982]. The LAP basalt is all but identical, however, in
composition and texture (Figure 6.14) [
Korotev et al.,
2009a;
Fernandes et al
., 2009] as well as crystallization age
[
Korotev et al
., 2009a;
Fernandes et al
., 2009;
Wang and
Hsu
, 2010;
Elardo et al
., 2012, 2013] to 1.37-kg NWA
4734 from Morocco. These data strongly suggest that the
LAP basalts and NWA 4734 are launch paired [
Korotev
et al
., 2009a].
Paired stones NWA 032 and NWA 479 have several
chemical (Figures 6.12, 6.13, and 6.14) and petrograph-
ical features in common with the LAP stones, suggesting
that the two meteorites are launch paired [
Jolliff et al
.,
2004;
Zeigler et al
., 2005]. The crystallization ages are
very similar (Figure 6.8) as are the ejection ages
[
Nishiizumi et al
., 2006]. However, the two meteorites
have very different values of ε
Nd
, making any simple ge-
netic relationship unlikely [
Elardo et al
., 2012, 2013].
Thus, the similarities between LAP and NWA 032/479
may be coincidental.
ulvöspinel, with trace amounts of silica, troilite, baddelyite,
K- and Ba-rich alkali feldspar, and phosphates [
Joy et al
.,
2008;
Liu et al
., 2009]. Pyroxenes are strongly shocked and
all of the plagioclase has been converted to maskelynite
with some recrystallization.
The whole rock TiO
2
concentration of MIL 05035 is
not well constrained. For this work we obtained a mean
of 1.9% ± 1.5% (95% confidence limits) on a 0.42-g
sample (mean of 11 subsamples, Figure 6.13),
Joy et al
.
[2008] obtained 0.9% on a 0.31-g sample, and
Liu et al.
[2009] obtained 1.44% on a 1.9-g sample. The mass-
weighted mean, 1.45%, is listed in Table 6.2. From modal
recombination of the data of
Joy et al
. [2008] and
Liu
et al
. [2009] we estimate 1.6% TiO
2
. Similarly, MgO con-
centrations range from 6.1% (this work) to 7.8% [
Joy
et al
., 2008] among the three laboratories. For comparison,
Thaisen and Taylor
[2009], who note that the composition
of the fusion crust of MIL 05035 is highly variable from
place to place, obtained means and standard deviations
of 2.0% ± 0.9% TiO
2
and 5.8% ± 2.4% MgO from 170
analyses of the fusion crust.
It was recognized in the earliest studies of MIL 05035
that it was very similar in texture, mineralogy, and com-
position to Asuka 881757, collected 2500 km away in
Antarctica, and that the two meteorites were thus likely
launch pairs [
Arai et al
., 2007;
Joy et al
., 2007;
Liu et al
.,
2007;
Korotev and Zeigler
, 2007;
Zeigler et al
., 2007].
Subsequent studies have shown that the crystallization
ages also match (Figure 6.8). Although, as noted above,
6.5.9. Miller Range 05035
MIL 05035 is an unbrecciated low-Ti mare basalt with
a coarse-grained, gabbroic texture (Plate 66). Pyroxenes
range from 2 to 10 mm in size [
Arai et al
., 2010]. Modally,
the meteorite is 54%-62% pyroxene, 25%-36% plagioclase,
6%-7% symplectites, 0.6%-3.5% fayalite, 0.8%-1.0% silica,
0.5%-1.0% ilmenite, 0.5%-0.6% glass, and 0.2%-1.5%
