In this work we analyze chronological data for lunar meteorites with emphasis on the spatial and temporal distribution of lunar mare basalts. The data are mostly from the Lunar Meteorite Compendium (http://www-curator.jsc.nasa.gov/antmet/lmc/contents.cfm cited thereafter as Compendium) compiled by Kevin Righter and from the associated literature

Basilevsky, A.

Neukum, G.

Nyquist, Laurence

NASA Technical Reports Server

THE SPATIAL AND TEMPORAL DISTRIBUTION OF LUNAR MARE BASALTS AS DEDUCED FROM
ANALYSIS OF DATA FOR LUNAR METEORITES. A. T. Basilevsky i °', G. Neukurri' and L. Nyquist 3 . 1-Vernadsky
Institute of Geochernistry and Analytical Chernistry, RAS, Moscow, Russia atbas(iDgeokhi.tu ; 2-Freie Universitaet Berlin,
Berlin, Germany, 3-KR/NASA Johnson Space Center, Houston, Texas 77058, USA.
Introduction: In this work we analyze chronological data
for lunar meteorites with emphasis on the spatial and temporal
distribution of hmar mare basalts. The data are mostly from the
Lunar Meteorite Compendium (htto:i/www-ctirator.isc.iiasa.2ov/
antniet/lnic/contents.cfru cited thereafter as Compendium) com-
piled by Kevin Righter and from the associated literature.
The data: The Lunar Meteorite Compendium currently
lists 54 meteorites represented by 108 specimens (Figure 1). This
collection is large enough that taking in mind the stochastic na-
ture of impacts delivering pieces of lunar rocks to Earth one may
consider these 54 meteorites to be a rather representative random
sampling of the lunar near-surface crust.
In the Compendium, lunar meteorites are subdivided into
three groups: group B — mare basalts and gabbros, group F -
feldspatic (anorthositic) highland breccias, and group M - brec-
ciated mixtures of these two end-members. The latter type has
also been referred to as "mingled". Of the 54 meteorites, 10 be-
long to group B, 30 to group F, and 14 to group M. Breccias of
groups F and M (44 meteorites in total) are presented by 4 varie-
ties: regolith breccias — 19, fragmental breccias — 12, impact-melt
breccias — 10.. and granulitic breccias — 3. The abundances of
these groups and their varieties are a subject of the following
analysis.
Another subject of our analysis is the data for absolute ages
of crystallization of the meteorite basalts. Among the 10 basalts
and gabbros of group B. 9 have been isotopically dated.. and
among 14 mingled breccias, basaltic clasts have been isotopically
dated only in 6. The results of these datings acquired mostly from
the literature cited in Compendium and partly from recent publi-
cations are given in Table 1.
Analysis of the data: We analyze the available data along
the following lines:
I) Relative abmidance of the groups B, F and U. If the ana-
lyzed collection is a representative sample of the near-surface part
of the lunar crust, one should expect that the relative abundances
of basalts/gabbros and feldspatic (anorthositic) breccias in this
sample are proportional to the relative areal abundances of the
lunar maria and highlands. The latter is known to be —1:5. while
the B vs. F abundance is 1:3 differing somewhat from the mare to
highland area ratio. But, if we combine the abundances of groups
F and M, then B vs. F+M is 1:4.4, i.e., close enough to the mare
to highland area ratio.
2) Significance of regolith breccias: Regolith breccias
were formed within the regolith layer [e.g, 1], the thickness of
which as estimated by different techniques varies from 3-5 in
maria to 15-35 in highlands [e.g., 1,2]. Craters ejecting frag-
ments of regolith breccias should not be significantly deeper than
the regolith thickness. If the crater was significantly deeper, then
its ejecta should be dominated not with the regolith breccias but
with the components of bedrock. Regohith breccias compose 35%
(19 of 54) of the considered collection. This means that —1/3 of
the craters from which ejecta are present in the considered collec-
tion. were not significantly deeper than 3-5 to 15-35 m. Taking in
mind that depth of ejection from impact craters is —1/10 of the
crater diameter [3] one can conclude that these craters had diame-
ters not significantly larger than several hundreds of meters. This
agrees with the conclusion of [4] that typical lunar meteorite
source craters are << 3.6 kin in diameter and smaller source cra-
ters are easily possible and with model estimates by [5] which
support the "small impact' scenario with maximum parent crater
of about 0.6-1 km. As an option one may suggest that lunar rego-
lith breccias have been ejected from the Moon by mechanism of
spallation of the surface layer suggested by [6]. However this
mechanism could be effective only in the case of large craters (in
the case of small craters the spallation zone is too small). but
consequence of this should be large amount of launch-paired
meteorites. The latter are present in the collection , but not ftre-
quent [Compendium].
3) Significance of mingled breccias: These breccias contain
clasts of both mare and highland rocks. This implies that each of
the craters from which ejects provided meteorites of group M had
to be formed in targets composed of both mare and highland
materials. It is also necessary to keep in mind that 8 of 14 brec-
cias of group M are regolith breccias. The mingled breccias could
be delivered from three geologic situations: 1) a mare-highland
boundary, 2) the mare areas where the highland material base-
ment is at small enou gh depth, and 3) cryptomare areas, where the
highland material mantles overlie ancient maria. The group M
breccias compose 26% of the considered collection so the mare-
highland boundary (which is narrow) looks unfavorable for pro-
viding such a large fraction of the collection. The mare areas with
shallow highland-material basement also do not look promising..
especially for the cases of regolith breccias. In the latter cases, the
mare layer should be meters to a few tens of meters thick.. which
would lead to very peculiar mare/highland embayrnents not typi-
cal for the Moon. Cryptomaria [7,8] look most promising in this
respect. But, if they are the major supplier of the group M brec-
cias this may mean that cryptomaria are rather abundant in the
lunar highlands (14/(14+30) =-1/3), and that about half of them
are covered with very thin highland material mantles. The mete-
orite launch-pairing may decrease this eatimate. These sugges-
tions can be tested with analysis of images of Lunar Reconnais-
sance Orbiter Camera.
4) Ages of meteoritic mare basalts. As is seen in Table 1 and
Figure 2.. most of the meteoritic mare basalts have been dated by
several techniques. As a mle.. for a given meteorite the age values
determined by Sm-Nd, U-Pb and Rb-Sr techniques are close, but
those determined by K-Ar technique are often lower probably due
to subsequent thermal episode(s). So, for our consideration we
used values determined by the Sm-Nd, U-Pb and Rb-Sr tech-
niques [9-15], and only in one case the K-Ar value [16] because
no other techniques were applied to this meteorite.
Fig 1 shows what has been noted already by other reserarch-
ers [e.g., 10,13,17]: the meteorite mare basalts show a time span
broader than basalts sampled by Apollo and Luna missons. It is
interesting that the meteorite basalts ages fill the gaps in the Apol-
lo/Luna basalt age distribution and generally are in a good agree-
ment with the mare basalt age distribution determined by the
crater count technique [16] that was mentioned earlier by [ 10].
Conclusions: The above analysis shows that the distribution
of lunar meteorites in broad petrologic groups seems to be propor-
tional to the areal distribution of latter, that a significant part of
the lunar meteorite source craters are smaller than hundreds of
meters in diameter, that cryptomaria seem to be rather abundant,
and that the meteorite mare basalt ages fill the gaps in the Apol-
lo/Luna basalt age distribution.
References: [1] Heiken G.H. et al. eds. (1991) Lunar Source
Book. Cambridge Univ. Press. [2] Williehns D.E. (1987) The
Geologic History of the Moon. USGS Prof. Paper 1348. [3] Me-
losh H.J. (1989) Inepact Cratering. Oxford Univ. Press. [4] War-
ren P. (1994) Icarus, 111, 338-363. [5] Artemieva (2006) LPSC
37, #1168. [6] Melosh J. (1984) Icarus, 59, 234-260. [7] Schultz
P.H., Spudis P.D. (1979) LPSC-10 Proc, 2899-2918. [8]
Head J.W.. Wilson L. (1992) GCA, 56,2155-2175. [9] Shih C.-Y.
et al. (2002) LPSC 33, #1344. [10] Nyquist Let al. (2005) LPSC
36, #1374. [11] Nyquist Let al. (2007) LPSC 38, #1702. [12]
Shili C.-Y. et al. (2008) LPSC 39, #2165. [13] Nyquist L. et al
(2009) MPS. 44, A159. [14] Terada K. et al. (2007) Nature, 450.
849-852. [15] Gafiiey A. at al (2008) LPSC 39, #1877. [16] Pol-
nau E, Eugster O. (1998) MPS, 33, 313-319. [17] Korotev R.
(2005) Chemie der Erde 65, 297-346. [18] Hiesinger H. et al.
(2003) JGR, 108, 5065.
https://ntrs.nasa.gov/search.jsp?R=20090037107 2019-08-30T08:10:39+00:00Z
s^	
ti •^: 1 R_
x	 t. r•'A
Yamato 793169, 6,09 g 	 Asuka 881757, 442 g
sit
	nt
Nortwest Africa 479, 156 g La Paz IF 02205, 1226 g
r-'
Dhofar 287, 154 g
Figure 1. Photos of selected hmar meteorite basalts from Lunar Meteorite Compendium (littp://www-curator. isc.naso.gov/antmet/hncicontents.cfru)
Table 1. Isotope age determinations of the lunar ineteorite basalts
Group Meteorite name
B1
	 Yamato 793169
B2
	
Asuka 881757
B3
	 NWA 032, 479
B4
	 NEA 003
B5
	 NWA 773, 2700 9 2727, 2977, 3160
B6
	 Dhofar 287
B7
	 La Paz IF 02205.. 02224, 02226, 02436
B8
	 Miller Range 05035
B9
	 NWA 4898
M1
	 Yamato 793274, 981031
M2
	 Elephant Moraine 87521, 96008
M4
	 Queen Alexandra Range 94281
M5
	 Kalahari 008.. 009
M7
	 Meteorite Hills 01210
M8
	 Sayln al Uliayrnir 169
Short description
Unbrecciated basalt
Gabbro
Unbrecciated basalt
Unbrecciated basalt (with basaltic breccia)
Gabbro (with basalt and breccia)
Unbrecciated basalt (with basaltic breccia)
Unbrecciated basalt
Unbrecciated basalt
Unbrecciated basalt
Anorthosite-bearing basaltic regolith breccia
Basaltic or gabbroic fragmental breccia
Anorthosite-bearing basaltic regolith breccia
Anorthositic regolith / basaltic fragmental breccias
Anorthosite-bearing basaltic fragmental breccia
Basalt-bearing anorthositic regolith breccia
Absolute age, Ga
3.8-3.9 U-Th-Pb, 3.43 Sm-Nd, 1.64 K-Ar
3.94 U-Th-Pb, 3.84 Rb-Sr, 3.87 Sm-Nd„ 3.75 K-Ar
2.85 Rb-Sr, 2.69 Sm-Nd, 2.75-2.73 Ar-Ar
3.09 Sm-Nd, 2.38 Ar-Ar
3.10 Sm-Nd, 2.67-2.94 Ar-Ar
3.35 U-Pb, 3.46 Sm-Nd
2.93 U-Pb, 2.99 Rb-Sr, 3.15 Sm-Nd, 2.94 Ar-Ar
3.90 Rb-Sr, 3.80 Sm-Nd
3.58 Rb-Sr
3.5 U-Pb IM mare, 4-4.1 U-Pb anorthosite
3.53-3.69 U-Pb (accept 3.6), 3.23-3.30 At-Ar
3.77 K-Ar
4.35 U-Pb IM, 4.3 Sm-Nd, 4.29 Lu-Hf, 2.67 Ar-Ar
3.8-3.9 U-Pb accept 3.85
3.91 U-Pb, 3.8 Ar-Ar
Lunar mare basalt meteorite isotope ages
q 	 q 	 q 	 q 	
°qSm-Nd Rb-Sr U-Pb K-Ar
	 q q 	 q®	 ®E	 IQ0 DOE q 	 n
0	 1	 2	 3	 4
40 Apollo & Luna mare basalt isotope ages
U
rN
°' Lunar mare basalt cratering ages
LL -	 20 Modified from Hiesinger et al., 2003
i
0
0	 1	 2	 3	 4
Age (Ga)
Figure 2. Lunar meteorite mare basalt ages of crystallization in comparison with Apollo/Luna mare basalt ages and ages
detennined by crater count technique [ 16].


The Spatial and Temporal Distribution of Lunar Mare Basalts As Deduced From Analysis of Data for Lunar Meteorites

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