PII S0016-7037(02)01085-2
History and origin of aubrites
S. LORENZETTI,1,* O. EUGSTER,1 H. BUSEMANN,1 K. MARTI,2 T. H. BURBINE,3 and T. MCCOY3
1Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
2University of California, San Diego, Chemistry, 9500 Gilman Drive, La Jolla, CA 92093-0317, USA
3Smithsonian Institution, Dept. of Mineral Sciences MRC NHB-119, Washington DC 20560, USA
(Received December 11, 2001; accepted in revised form July 29, 2002)
Abstract?The cosmic ray exposure (CRE) ages of aubrites are among the longest of stone meteorites. New
aubrites have been recovered in Antarctica, and these meteorites permit a substantial extension of the database
on CRE ages, compositional characteristics, and regolith histories. We report He, Ne, and Ar isotopic
abundances of nine aubrites and discuss the compositional data, the CRE ages, and regolith histories of this
class of achondrites. A Ne three-isotope correlation reveals a solar-type ratio of 20Ne/22Ne 
 12.1, which is
distinct from the present solar wind composition and lower than most ratios observed on the lunar surface. For
some aubrites, the cosmic ray-produced noble gas abundances include components produced on the surface
of the parent object. The Kr isotopic systematics reveal significant neutron-capture-produced excesses in four
aubrites, which is consistent with Sm and Gd isotopic anomalies previously documented in some aubrites. The
nominal CRE ages confirm a non-uniform distribution of exposure times, but the evidence for a CRE age
cluster appears doubtful. Six meteorites are regolith breccias with solar-type noble gases, and the observed
neutron effects indicate a regolith history. ALH aubrites, which were recovered from the same location and
are considered to represent a multiple fall, yield differing nominal CRE ages and, if paired, document distinct
precompaction histories. Copyright ? 2003 Elsevier Science Ltd
1. INTRODUCTION
The enstatite meteorites have long been of interest because
of their reduced mineral composition and variable metal abun-
dances (e.g., Mason, 1962). The composition of metal, schre-
ibersite, and perryite was studied by Wasson and Wai (1970) to
assess the origins of aubrites (the member name used for
enstatite achondrites) and enstatite chondrites. Watters and
Prinz (1979) concluded that it is not clear whether aubrites
represent nebular condensate or igneous differentiates. They
also noted that the enstatite meteorite Happy Canyon (EL6)
shows compositional similarities to aubrites, including negative
Eu anomalies, which suggest an origin by fractional crystalli-
zation. An igneous history of the aubrite parent asteroid was
inferred from the study of the Norton County meteorite (Okada
et al., 1988), while evidence for an impact origin was found in
Shallowater (Keil et al., 1989). The oxygen as well as nitrogen
isotopic systematics distinguish them from other meteorites
(Clayton et al., 1984; Murty and Marti, 1990). Oxygen isotopic
signatures of enstatite meteorites plot close to the terrestrial
fractionation line (Clayton et al., 1984; Newton et al., 2000)
and document that the source is distinct from chondritic parent
asteroids. The O signatures of enstatite meteorites also plot
close to terrestrial and lunar pyroxenes (Clayton et al., 1984).
Oxygen isotope ratios, recently determined in 14 aubrites by
Newton et al. (2000), confirm signatures close to the terrestrial
fractionation line (TFL), but at least four aubrites have 17O
signatures offset from the TFL, indicating chondritic or other
inclusions. The nitrogen isotopic signatures of aubrites, how-
ever, are distinct from those in indigenous lunar rocks (Mathew
and Marti, 2001). The 35Cl(n,
) neutron-capture reactions
may affect the 36Ar spallation components. Accordingly, 36Ar/
38Ar ratios of 7 were observed in stepped-heating studies of
the enstatite chondrite Abee (Wacker, 1982).
The cosmic ray exposure (CRE) age of Norton County, the
first measured stony meteorite (Begemann et al., 1957), yields
the longest currently known exposure time of a stone meteorite.
Gaffey et al. (1992) suggested a link between aubrites, near-
Earth asteroid 3103, and E-type asteroids of the Hungaria
family, based on spectral matches and orbital dynamics con-
siderations. Moreover, the orbital elements of Apollo object
3103 (Eger) are consistent with long collisional lifetimes.
Crabb and Anders (1981) found that exposure ages of enstatite
meteorites show a trend, E4  E6  aubrites, while Patzer and
Schultz (2001) conclude that there is no systematic trend in E
chondrites either for subgroups or for petrologic types.
The first systematics on the exposure ages of aubrites were
obtained by Eberhardt et al. (1965a). These workers noted a
cluster of exposure ages at 40 Ma and that some of the
aubrites show the presence of solar wind (SW) gases. In fact,
the high relative occurrence of SW-containing meteorites
among the enstatite achondrites is a major reason for a detailed
examination of a regolith exposure history on their parent
asteroid (Graf and Marti, 1992). Further, the occurrence of
chondritic inclusions in the Cumberland Falls achondrite (Ma-
son, 1962) and the evidence for a planetesimal impact in the
Shallowater meteorite also are indicative of regolith processes.
Thermal neutron fluxes in Norton County and Shallowater were
reported by Bogard et al. (1995). Large isotopic anomalies in
Sm and Gd, due to neutron-capture effects, were reported in
five aubrites (Hidaka et al., 1999). The inferred neutron flu-
ences compare to those observed in lunar samples and indicate
regolith histories. A comprehensive study of CRE histories of
aubrites and of the parent body regolith history appears appro-
priate at this time, since a number of new aubrites have been
* Author to whom correspondence should be addressed
(lorenzetti@phim.unibe.ch).
Pergamon
Geochimica et Cosmochimica Acta, Vol. 67, No. 3, pp. 557?571, 2003
Copyright ? 2003 Elsevier Science Ltd
Printed in the USA. All rights reserved
0016-7037/03 $22.00  .00
557
recovered in Antarctica (ALH 84024, EET 90033, EET 90757,
LEW 87007, QUE 97289, QUE 97348, and Y 793592). A goal
of this work is to integrate CRE ages, SW loading, regolith
data, and other mineralogic or petrologic observations. Prelim-
inary data on the CRE ages reported in this work have been
published in abstracts (Lorenzetti and Eugster, 2000; Lorenzetti
et al., 2001).
2. EXPERIMENTAL METHODS
The investigated samples were crushed in a stainless steel mortar to
a grain size of  750 m to get an uniform mixture and then split in
two parts, one for the chemical analyses, the other one for noble gas
measurements.
2.1. Chemistry
We determined the bulk chemical composition of ALH 84018, ALH
84024, EET 90757, EET 90033, and LEW 87007 by melting a 50-mg
aliquot of each. Samples were melted in a Deltech vertical mixing
furnace at 1550?C for 5 min in a graphite crucible wedged on the end
of a sealed alumina tube. The short run time, graphite crucible, and
sealed container prevented volatilization and/or oxidation of the sam-
ples. The fused beads were quenched in air, resulting in glassy-to-
microcrystalline textures. Compositions were measured by averaging
20 to 40 individual analyses that each used a 40-m rastered beam on
the JEOL JXA-8900R electron microprobe at the Smithsonian Institu-
tion. Oxygen was calculated by stoichiometry for all elements except
Fe, Ni, Cr, and S.
The paired QUE 97289/97348 meteorites are terrestrially weathered,
and we could not use the same technique to derive their bulk compo-
sition. X-ray compositional maps for the QUE samples (QUE 97289
and 97348) were collected for 11 elements (Al, Ca, Cr, Fe, K, Mg, Mn,
Na, P, S, and Si) using the scanning electron microscope. From these,
we computed area percentages for daubre?elite, enstatite, feldspar, me-
tallic iron, and weathering products (assumed to be FeOOH), silica, and
schreibersite. The percentages were averaged for the two thin sections,
and weight percents were calculated using average densities (Keil,
1968). We estimated that 80% of the metallic iron had been converted
to terrestrial FeOOH. The bulk compositions were determined by
multiplying the weight percents of the various minerals, and the com-
positions of each mineral phase were measured using the electron
microprobe.
2.2. Noble Gas Mass Spectrometry
2.2.1. He, Ne, and Ar
All investigated samples were interior chips without fusion crust.
Before the noble gas analyses, the samples were heated at 100?C for
1 week in the extraction system to remove atmospheric gases. The
noble gases were extracted at 1700?C, and for each sample a second
extraction at 1740?C was made. The samples were measured according
to procedures discussed by Eugster et al. (1993).
2.2.2. Kr
The heavy noble gas Kr has been measured in the aubrites Cumber-
land Falls, Mayo Belwa, Mount Egerton, Norton County, and Shallo-
water. These analyses are part of an extended study on the composition
of the trapped heavy noble gases in achondrites (Busemann and Eug-
ster, 2002). We report the excesses of 80Kr and 82Kr from neutron-
capture in 79Br and 81Br, respectively. The 79Br (n, 
) 80Kr reactions
are predominantly due to epithermal neutrons (Marti et al., 1966).
3. RESULTS
We first provide brief descriptions of the meteorites and then
present the noble gas isotopic abundances in the investigated
meteorites and adopted chemical compositions, which are re-
quired to calculate production rates for cosmogenic noble gases
and to derive radiogenic ages. Most of the measured aubrites
(ALH 84007, ALH 84008, ALH 84011, ALH 84024, Aubres,
Bustee, EET 90033, EET 90757, LEW 87007, Mayo Belwa,
Norton County, Pen?a Blanca Spring, Pesyanoe, and Y 793592)
have roughly similar mineralogy (Watters and Prinz, 1979),
consisting predominately of enstatite (80?95 vol.%) with
minor feldspar, sulfides, metallic iron, diopside, and forsterite.
3.1. Petrographic and Chemical Data
Although most investigated aubrites are breccias, they differ
significantly in the degree of brecciation and shock blackening.
Most of them are finely brecciated (e.g., Khor Temiki), with
clasts typically a few millimeters in diameter. However, coarse
clasts and individual silicate inclusions reaching 45 mm in size
(Mason, 1962) are found in some aubrites; in Pen?a Blanca
Spring, such inclusions reach up to 10 cm (Lonsdale, 1947; this
work). Aubrites also vary significantly in their degree of shock-
blackening. Mayo Belwa, in particular, is extensively shock-
blackened, and approximately one-third of the ALH 84 aubrite
pairing group are shock-blackened.
The following paragraphs give petrologic descriptions of
each of the aubrites studied in this paper. We reference previ-
ous studies for each of the meteorites; however, Smithsonian or
Johnson Space Center samples and thin sections of each me-
teorite (excluding the Japanese ones) were examined to confirm
the descriptions.
Two aubrites (ALH 78113, Cumberland Falls) are known to
contain chondritic clasts (e.g., Neal and Lipschutz, 1981; Kal-
lemeyn and Wasson, 1985; Lipschutz et al., 1988). The matri-
ces of these meteorites are similar to the brecciated aubrites,
consisting of igneous clasts dominated by enstatite. The clasts
are chondrule-bearing, rich in metal and sulfide, and sample a
group of meteorites not otherwise represented in our collec-
tions. The chondritic inclusions in ALH 78113 are much
smaller and much sparser than those found in Cumberland
Falls.
Aubres is a whitish rock and contains 97 vol.% enstatite
(Watters and Prinz, 1979), with minor plagioclase, diopside,
forsterite, troilite, and metallic iron. The enstatite varies from a
fine-grained matrix to grains as large as 1 cm.
Bishopville is similar to the finely brecciated aubrites in most
respects, but is mineralogically unusual in containing a signif-
icantly higher abundance of plagioclase (16 vol.%) relative to
other known aubrites (Watters and Prinz, 1979).
Mt. Egerton is an unbrecciated meteorite composed of cm-
sized enstatite crystals with 21 wt.% metallic Fe, Ni occur-
ring in the interstices between the large enstatite laths
(Casanova et al., 1993). It broke into fragments no larger than
5 cm across on impact with Earth. It is similar in most respects
to aubrites and should probably be classified as an aubrite. It is
unusual in being unbrecciated and containing a far greater
percentage of Fe, Ni metal than other aubrites.
Norton County is the largest recovered aubrite with an esti-
mated mass of 1 ton (Grady, 2000). Norton County is 85 vol.%
enstatite and 10% forsterite (Watters and Prinz, 1979), with
minor diopside, plaglioclase, troilite, and metallic iron. The
enstatite varies from a fine-grained matrix to inclusions as large
as 8 cm (Okada et al., 1988).
Pesyanoe is a brecciated aubrite composed almost entirely of
558 S. Lorenzetti et al.
enstatite (90 vol.%) and plagioclase (7%) with accessory diop-
side (1%) and forsterite (1%).
Recently, an unusual clast was discovered in Pesyanoe
(Ivanova et al., 2002). This clast is composed of FeO-rich
olivine (Fa14), orthopyroxene (En83Wo3), pigeonite
(En78Wo9), and Ti-poor troilite (Keil et al., 1989). It is unclear
if this clast is indigenous to the aubrite parent body or has a
foreign origin. One of these clasts is composed of FeO-rich
olivine (Fa14), orthopyroxene (En84 Wo3), pigeonite (En79
Wo9), and Ti-poor troilite. Another clast is composed of a
mixture of plagioclase and silica.
The paired aubrites, QUE 97289 and QUE 97348, exhibit
igneous textures and mineralogies consistent with their inclu-
sion in the enstatite meteorite clan, but the material is believed
to have formed as impact melts from known enstatite chon-
drites (McCoy et al., 1995; Burbine et al., 2000). The QUE
97289/97348 meteorites consist predominately of 1 mm-
sized, rounded enstatite grains with abundant feldspar, metal,
and sulfides, and their bulk compositions are similar to enstatite
chondrites (Table A1).
Shallowater is an unbrecciated aubrite consisting of 80 vol.%
orthoenstatite crystals with monomineralic or polymineralic
inclusions of twinned low-Ca clinoenstatite, forsterite, plagio-
clase, metallic Fe, Ni and troilite (Keil et al., 1989). Keil et al.
(1989) argued that both the history and parent body of Shallo-
water are unique, having formed when a solid enstatite chon-
drite-like planetesimal (the xenolithic inclusions) impacted a
completely molten, enstatite-rich parent body (the enstatite-rich
host).
Y 793592 is a typical aubrite that is predominately enstatite
with minor plagioclase, forsterite, metallic iron, and sulfides
(troilite and daubreelite) (Yanai, 1992). The enstatite varies
from a fine-grained matrix to grains as large as 0.6 cm.
Results on the chemical composition of all aubrites are given
in Tables A1 and A2 and agree well with the range of bulk
aubrite compositions given by Watters and Prinz (1979).
3.2. Noble Gas Data
The results of He, Ne, and Ar analyses are given in Table A3.
The literature data given in Table A4 were taken from the
compilation of Schultz and Franke (2000). To obtain average
values from the various He, Ne, and Ar analyses for the same
meteorite, we proceeded in the following way: (1) In general,
data published before 1965 were not considered because of
uncertainties in the correction for isotopic fractionation effects
of Ne (Eberhardt et al., 1966). (2) Aubrite samples with large
SW components were not considered, except for Pesyanoe
dark. (3) Samples that plot clearly below the 3He/21Ne vs.
22Ne/21Ne correlation line (see below) indicate gas loss and
were not included in the average value. (4) Samples with ratios
22Ne/21Ne  1.05 have uncertainties in the production rates
and were not considered. The results of the Kr analysis are
given in Table A5 and the excesses due to neutron-capture in
Br on isotopes 80Krn and 82Krn in four aubrites (Cumberland
Falls, Mayo Belwa, Shallowater, and Khor Temiki) in Table 1.
3.3. Solar Ne
Six aubrites (Bustee, EET 90033, Khor Temiki, LEW 87007,
Pesyanoe, and Y 793592) contain solar-type light noble gases
(Fig. 1) with relative abundances similar to those inferred for
the Sun (Anders and Grevesse, 1989). To derive the isotopic
signature of solar-type Ne in aubrites, we use the standard
three-isotope correlation plot (Fig. 2) with endmembers of
trapped and cosmogenic composition. Selected data include
only bulk samples and enstatite-rich separates. The observed
correlation yields 20Ne/22Ne 
 12.1  0.2 for the trapped
component, which is considerably lower than SW-Ne and is
closer to solar energetic particle-Ne (SEP-Ne) data (Benkert et
al., 1993). This 20Ne/22Ne ratio is not only distinct from the
modern SW-Ne datum (20Ne/22Ne 
 13.8  0.1; Benkert et al.,
1993), but also differs from long-term average ratios observed
Table 1. Cosmogenic and neutron produced Kr in Aubrites.
83Krc 80Krn
(80Kr/82Kr)n1012cm3STP/g
Cumberland Falls 1.95 15.3 2.8  0.7
Khor Temiki1) 2.51 0.52 2.4  0.3
Mayo Belwa 3.75 1.5 na
Mt. Egerton bd  0.4 na
Norton County 3.90  0.4 na
Shallowater bd 10.5 1.9  1.5
na - not analyzed; bd - below detection limit. Experimental errors:
noble gases  15% (1); 1) Calculated from data of Eugster et al.
(1969).
Fig. 1. Trapped noble gas concentrations in the six solar gas-con-
taining aubrites.
559History and origin of aubrites
on the lunar surface (20Ne/22Ne 
 12.8  0.2) and either
documents a distinct mix of SEP and SW Ne components
during the irradiation on the aubrite parent body or a different
power law spectrum of the superthermal tail of the solar wind,
if SEP-Ne ratios represent variable range-energy effects (Me-
wald et al., 2001). Trapped 4He/3He ratios obtained for Pesya-
noe, Khor Temiki (3-m sample), and LEW 87007 are higher
(3500) than those observed in the recent solar wind (2350) or
on the lunar surface ( 3200) (cf. Eugster et al., 2001).
3.4. Cosmogenic Noble Gases
In the data for Bustee, Khor Temiki (3-m separate), LEW
87007, Pesyanoe dark, and Y 793592 trapped (tr), 3He was
subtracted from measured 3He, adopting 4Her 
 2000 
108cm3STP/g, (4He/3He)tr 
 3500, and (4He/3He)c 
 5.2,
where (r) is the radiogenic component and (c) the cosmogenic.
For all other samples, we adopt 3Hec 
 total 3He. Most aubrites
contain some trapped Ne; although the ratio (20Ne/36Ar)tr is
generally  1, we assume Netr to be of solar origin and adopt
(20Ne/22Ne)tr 
 12.1 (Fig. 2) and (20Ne/21Ne)tr 
 400. We use
a spallation ratio (20Ne/21Ne)c 
 0.9 to calculate 21Nec abun-
dances. The resulting concentrations are insensitive to these
assumptions, since the correction of 21Netr is always  3%.
Trapped Kr relative isotopic abundances are adopted from
Busemann et al. (2000). Table 2 reports the cosmogenic noble
gas components in all studied aubrites.
4. DISCUSSION
4.1. The 21Ne Production Rate
Reliable CRE ages for aubrites can be obtained either by the
81Kr-Kr method or from 21Nec concentrations and in many
cases from 3Hec. Because of low concentrations and inhomo-
geneous distribution of the elements Ca and Fe, larger uncer-
tainties are encountered with the 38Arc production rate P38, and
CRE ages based on 38Ar are not reported here. The production
rates P3 and P21 depend not only on the chemical composition,
but also on the shielding properties. Since the chemical com-
position of aubrites differs from the meteorites for which
shielding-dependent production rates are available (for chon-
drites, see Eugster, 1988; for HED-meteorites, see Eugster and
Michel, 1995), production rates need to be evaluated here. The
21Ne production rate (P21) is assumed to have the general form:
P21 
 F P	21 [a(22Ne/21Ne)c  b]1 (1)
where F is the ?composition parameter? for average aubritic
chemistry and average shielding conditions, and P21' the pro-
duction rate for a reference composition (Eugster and Michel,
1995). The ?shielding factor? [a(22Ne/21Ne)c-b] is obtained
from the correlation of 3He/21Ne vs. 22Ne/21Ne (Fig. 3).
Table A1 lists the chemical compositions of aubrites. Most
aubrites are Fe-poor and have quite uniform chemical compo-
sition, with average target element abundances given in Table
A1 that yield P	21
 0.462  108cm3STP/g, Ma and F 
 3.78
 0.60. The 3He/21Ne vs. 22Ne/21Ne correlation for Fe-poor
aubrites in Figure 3 (data in Table 2) fits Eqn. 2:
3He/21Ne 
 17.6 (22Ne/21Ne)c  15.9 (2)
Alternatively, the composition parameter F in Eqn. 1 can be
calculated from available 81Kr-Kr ages, T81, (Eugster et al.,
1969; Miura et al., 1999) from Eqn. 3
P21 
 21Ne/T81 
 F P	21[17.6(21Ne/21Ne)c  15.9]1 (3)
and we obtain F 
 3.52  0.30 (uncertainties in T81 included).
Although the agreement between the two F values is good, we
adopt the F value calibrated with the 81Kr-Kr method, which is
composition- and shielding-independent, and obtain the follow-
ing 21Ne production rate for Fe-poor aubrites:
Fig. 2. Neon three-isotope plot for all aubrites with solar gases. Data from this work, except for Khor Temiki (Eberhardt
et al., 1966) and Pesyanoe dark (Mu?ller and Za?hringer, 1966).
560 S. Lorenzetti et al.
P21 
 (3.52  0.30) P	21[17.6(22Ne/21Ne)c  15.9]1, (4)
where P	21 
 1.63 [Mg]  0.6 [Al]  0.32 [Si]  0.22 [S] 
0.07 [Ca]  0.021 [FeNi].
The elemental concentrations are inserted in wt.%, and P21
results in units of 1010cm3STP/g per Ma (Table 3).
4.2. CRE Ages
Published data permit some relevant assessments of expo-
sure histories. The data for Norton County include two mea-
surements by Kirsten et al. (1963) for an interior and an exterior
sample for which 3Hec and 21Nec show differences of 7% and
Table 2. Cosmogenic He, Ne, and Ar in aubrites. Concentrations in 108cm3STP/g.
3He 21Ne 38Ar 22Ne/21Ne References
ALH 78113 35.6 11.5 0.44 1.086 3)
ALH 84007 45.2 14.3 0.19 1.080 4)
ALH 84008 25.9 8.61 0.18 1.095 3)
ALH 84011 36.1 12.2 0.13 1.086 3)
ALH 84024 24.0 8.78 0.12 1.071 5)
Aubres 13.8 5.9 0.12 1.115 3)
Bishopville 91.8 22.4 0.27 1.107 3)
Bustee 88.7 25.8 1.21 1.100 3)
Cumberland Falls Fe-poor 1) 29.0 0.65 1.086 3)
Cumberland Falls Fe-rich 1) 24.5 1.00 1.083 3)
EET 90033 45.0 18.3 0.66 1.064 5)
EET 90757 1) 16.6 0.46 1.105 5)
Khor Temiki enstatite 94.0 24.5 0.19 1.115 3)
LEW 87007 104.5 31.3 1.45 1.073 5)
Mayo Belwa 178 51.8 1.86 1.129 3)
Mt. Egerton 16.3 10.4 0.158 na 6)
Norton County 205 54.4 2.16 1.093 3)
Pen?a Blanca Springs 119 24.9 0.70 1.181 3)
Pesyanoe light 87.9 19.7 0.46 1.092 3)
Pesyanoe dark 8) 12.2 2) 1.38  0.40 3)
Pesyanoe-92 enstatite crystal 1 78.4 21.7 0.26 1.091 5)
Pesyanoe-92 enstatite crystal 2 77.5 20.7 0.37 1.110 5)
Pesyanoe-90,2 84.4 32.9 2.5 1.081 5)
QUE 97289 71.6 19.6 0.97 1.030 5)
QUE 97348 1) 16.6 1.06 1.023 5)
Shallowater 44.0 7.60 2) 1.190 3)
Y 793592 85.3 34.0 1.03 1.064 5)
Typical experimental errors (2 mean) are 4% for 3He and 21Ne, 10% for 38Ar, and 1?2% for 22Ne/21Ne, except where indicated; 1) diffusion loss;
2) trapped Ar contribution too high; 3) calculated from data given in Table A4; 4) average calculated for data given in Tables A3 and A4; 5) calculated
from data given in Table A3; 6) Miura et al. (1999); 7) Mu?ller and Za?hringer (1966); na, not analysed; 8) uncertain.
Fig. 3. 3He/21Ne vs. 22Ne/21Ne diagram for Fe-poor (Fe  2%) aubrites. Aubres shows 3He and 4He loss and is not
plotted.
561History and origin of aubrites
11%, respectively, with higher interior production rates, con-
sistent with the large recovered mass (1000 kg), and shielding
dependent production rates for 4-irradiation. On the other
hand, the cosmic ray-produced concentrations of 21Nec in the
light and dark phases of Pesyanoe (Mu?ller and Za?hringer, 1966)
differ by almost a factor of 2 and are not consistent with
shielding effects for 4-irradiation of the rather small Pesyanoe
meteorite. This is amplified by the 21Ne data (Table 3) in
Pesyanoe-90.2, also of the dark phase, which show a 21Nec
concentration that exceeds the one observed by Mu?ller and
Za?hringer (1966) by more than a factor of 2. Furthermore, we
have determined the spallation components in a single large
enstatite and also in a collection of large crystals that yield
consistent results (Tables 2, 3) and also agree with those of the
light phase of Mu?ller and Za?hringer (1966). We discuss the
implications regarding the irradiation history of Pesyanoe later.
The cosmic ray-produced noble gas abundances represent
the integral production by cosmic rays and include all the
components resulting from 2-irradiation on the surface of the
parent body. These effects need to be discussed individually, as
they affect the exposure times in space (transfer times). We will
first consider ?nominal? calculated CRE ages, which are given
in Table 3. 3He exposure ages (T3) are calculated using pro-
duction rates from Eugster and Michel (1995); 21Ne ages (T21)
are obtained using Eqn. 4 and concentrations given in Table 2.
A ?preferred nominal? CRE age (Tpref) is obtained as follows:
(1) Tpref 
 T81 is adopted if the errors in T81 are  15%. (2)
T3 is not used for cases with possible 3He losses, that is, for T3
 0.75 T21. (3) If T3 is included, Tpref 
 1/2 (T3  T21). We
assign experimental uncertainties of 10% in case (3) and 15%
in the other cases.
The nominal calculated CRE ages (Table 3; Fig. 4) show a
non-uniform distribution, as was already observed by Eberhardt
et al. (1965a) based on a limited dataset. A cluster of CRE ages
of 56  6 Ma includes Bishopville, Bustee, Cumberland Falls,
Khor Temiki, Y 793592, and LEW 87007. However, some of
these meteorites (Cumberland Falls, Khor Temiki, Mayo
Belwa, and Shallowater) show neutron-capture effects, and the
nominal CRE ages will be discussed with regard to possible
regolith histories. The CRE ages of Norton County and Mayo
Belwa are similarly long, the longest CRE ages of all stony
meteorites. The ALH aubrites were found in the same location
and for this reason were considered to represent a paired fall
(Grady, 2000). However, their CRE ages differ: Two of these
(ALH 84008 and ALH 84024) have CRE ages of 15  2 Ma,
while three (ALH 78113, ALH 84007, and ALH 84011) have
ages of 23  3 Ma. These data do not rule out possible pairing,
but a model of regolith evolution and precompaction irradiation
would be necessary to explain the data. We note that two
members with ages 23 Ma also reveal small positive 17O
excesses (Newton et al., 2000), indicating the possible presence
of non-aubritic material in these breccias. The CRE age distri-
bution shows that there are no young ( 10 Ma) ages. Thus, the
orbital characteristics of enstatite chondrites differ from those
of aubrites, as suggested previously by Gaffey et al. (1992).
Table 3. Production rates, Pi, CRE ages, Ti, 21Nen, and production rates P(21Nen).
P3 P21 T3 T21 T81 Tpref 21Nen P(21Nen)
108cm3STP/g,Ma Ma 108cm3STP/g 108cm3STP/g,Ma
ALH 78113 1.755 0.522 20.3 22.0 ? 21.1  2.0 9.0 0.0180
ALH 84007 1.758 0.542 25.7 26.4 ? 26.0  2.5 11.4 0.0186
ALH 84011 1.755 0.523 30.6 23.3 ? 22.0  2.0 9.6 0.0185
ALH 84008 1.751 0.498 14.8 17.3 ? 16.0  1.6 6.6 0.0175
ALH 84024 1.767 0.571 13.6 15.4 ? 14.5  1.5 7.2 0.0210
Aubres 1.742 0.448 ? 12.6 ? 12.6  2.0 4.2 0.0142
Bishopville 1.747 0.441 52.5 50.9 521)  5 52.0  5.0 16.4 0.0147
Bustee 1.744 0.475 50.8 54.4 ? 52.6  5.0 19.4 0.0160
Cumberland Falls Fe-poor 1.756 0.510 ? 56.8 451)  22 60.9  6.0 22.8 0.0161Cumberland Falls Fe-rich 1.634 0.377 ? 64.9 ? 19.4 0.0200
EET 90033 1.766 0.580 25.5 31.6 ? 28.5  3.0 15.4 0.0237
EET 90757 1.751 0.462 ? 35.9 ? 35.9  5.0 12.2 0.0149
Khor Temiki 1.743 0.439 53.9 55.8 522)  17 53.9  5.5 16.5 0.0134
LEW 87007 1.748 0.548 59.8 57.1 ? 58.5  6.0 25.6 0.0194
Mayo Belwa 1.738 0.407 102.4 127.4 1171)  18 116  12 35.1 0.0135
Mt. Egerton 1.628 0.387 10.0 26.9 ? 26.9  4.0 ? ?
Norton County 1.749 0.523 117.4 104.2 ? 111  11 41.8 0.0151
Pen?a Blanca Springs 1.713 0.333 69.5 74.7 ? 72.1  7.0 13.6 0.0083
Pesyanoe light 1.756 0.543 50.0 36.3 ? 43.2  7.0 15.1 0.0135
Pesyanoe dark 1.7594) 0.4974) ? 24.5 ? 24.5  5.0 ? ?
Pesyanoe-92 enstatite crystal 1 1.759 0.520 44.5 41.7 ?
43.5  4.0
16.7 0.0195
Pesyanoe-92 enstatite crystal 2 1.759 0.474 44.0 43.7 ? 15.0 0.0142
Pesyanoe-90.2 1.759 0.520 48.0 63.2 ? 55.6  8.0 26.2 0.0195
QUE 97289 1.6243) 0.4463) 44.1 43.9 ? 44.0  4.5 17.1 0.0256
QUE 97348 1.6243) 0.4463) ? 37.2 ? 37.2  5.5 14.5 0.0256
Shallowater 1.628 0.280 27.0 27.1 ? 27.0  2.5 4.0 0.0075
Y 793592 1.759 0.554 48.5 61.4 ? 55.0  7.0 28.6 0.0243
1) Miura pers. comm. (2001); 2) Eugster et al. (1969); 3) the production rates were calculated with (22Ne/21Ne)c 
 1.05, as limit for P3 and P21;
4) average production rates of Pesyanoe-92 enstatite crystal 1 and 2 adopted.
562 S. Lorenzetti et al.
4.3. Neutron-Induced Excesses in Ne and Kr
The depth-dependent ratio of neutron-induced (n) 21Ne to
total 21Nec was determined by Michel et al. (1991) for several
meteorites with known geometry. The concentrations of 21Nen
are calculated following Eugster et al. (1993):
21Nen 
 21Nec [3.5  2.5(22Ne/21Ne)c], (5)
and results are listed in Table 3.
Cumberland Falls, Khor Temiki, Mayo Belwa, and Shallo-
water indicate neutron-capture-produced components of 80Kr
and 82Kr (Figs. 5a,b). The concentrations of 80Krn and 82Krn
(Table 1) are calculated by subtracting pure spallation (s)
contributions based on (80Kr/83Kr)s 
 0.560  0.036 and
(82Kr/83Kr)s 
 0.764  0.023. These spallation ratios were
obtained by (1) adopting Kr data to represent mixtures of
spallation and trapped components (for those lacking neutron
effects) and by extrapolating isotopic correlations to the spal-
lation endmember ratio (86Kr/83Kr)s 
 0.015; and (2) by sub-
traction of the adopted trapped component based on 86Krtr. The
estimated errors include the uncertainties of spallation and
trapped datasets. Subtraction of the trapped and cosmogenic
concentrations from measured data yields the concentrations of
80Krn and 82Krn (Table 1). The (80Kr/82Kr)n ratios are 2.8  0.7
and 1.9  1.5 for Cumberland Falls and Shallowater, respec-
tively, and the (80Kr/128Xe)n ratio in Cumberland Falls is 10.9
 2.5. Marti et al. (1966) deduced values in the ranges 1.6 to
3.5 for (80Kr/82Kr)n and 12.4 to 42.0 for (80Kr/128Xe)n, depend-
ing on the hardness of the neutron energies. The (80Kr/82Kr)n
ratios reflect neutron fluences of epithermal energies (30?300
eV), the resonance region for neutron capture of Br (Marti et
al., 1966).
4.4. Preirradiation Effects
Above we discussed evidence for preirradiation effects in the
regolith on the parent body. Several types of monitors of
regolith exposure are known and may be used to study regolith
histories of meteorites: (a) the occurrence of clasts of distinct
composition in brecciated host material; (b) evidence for SW
loading; (c) evidence for neutron-capture effects; (d) discrep-
ancies of CRE ages of components in a breccia; (e) identifica-
tion of fission components due to neutron-induced fission of
235U. These records have successfully been used in studies of
the lunar regolith (Lingenfelter et al., 1972) and in a similar
manner may be used to assess processes in asteroidal regoliths.
Clear cases of complexity can be inferred if regolith evolution
from several monitors is observed. The Cumberland Falls me-
teorite exhibits evidence for the occurrence of clasts of chon-
dritic composition (Mason, 1962). This meteorite was classified
as an outlier sample in the O isotopic data (Clayton et al., 1984;
Newton et al., 2000). It also shows evidence for large neutron
fluences in the form of Sm and Gd isotopic shifts (Hidaka et al.,
1999). Large neutron-capture effects in Sm and Gd isotopic
abundances were also observed by these authors in four
aubrites: Norton County, ALH 78113, Bishopville, and Mayo
Belwa. Although small neutron capture effects have to be
expected for very long space exposure times, the implied neu-
tron flux is very large in the case of Cumberland Falls. Hidaka
et al. (1999) suggested that variable neutron fluences may be
expected for near-surface locations on their parent body. A
comparison of neutron effects with other regolith monitors is
useful.
The following aubrites were listed as regolith breccias by
Newton et al. (2000): Bustee, Khor Temiki, and Pesyanoe.
These three aubrites contain solar-type gases. This is also the
Fig. 4. CRE age histogram for aubrites. The CRE age of each aubrite was arranged to 10% age bins. The first bin contains
ages between 1 and 1.1 Ma. The Pesyanoe data document the light phase and the enstatite separates.
563History and origin of aubrites
case for EET 90033, LEW 87007, and Y 793592, which may
also be classified as regolith breccias. Support for this classi-
fication is obtained from petrographic properties, such as light-
dark structure and inclusions of different composition in a
brecciated host. We do not find evidence in aubrites for impact-
melt spherules such as those found in howardites and lunar
breccias (Bunch, 1975). Not all aubrites with foreign clasts are
solar gas carriers; Cumberland Falls is such an exception (Ta-
ble A4). Most aubrites are brecciated, but only Shallowater was
considered to have an impact origin (Keil et al., 1989).
It is informative to compare cosmic ray effects due to fast (

5 MeV) neutrons (21Nen) to those resulting from epithermal
neutrons (80Krn) and thermal neutrons (157Gd) (Hidaka et al.,
2000). 80Krn excesses were observed in the four aubrites,
Cumberland Falls, Khor Temiki, Mayo Belwa, and Shallowater
(Table 3), and thermal neutron effects were reported in two of
these (Hidaka et al., 1999). Neutron fluxes, n, for neutrons
with energies 
 5 MeV, as required for the reaction 24Mg (n,
) 21Ne, are obtained from:
n 
 P	(21Nen)/, (6)
where P'(21Nen) is the 21Nen atomic production rate per target
atom and  
 0.0562  1024cm2 (Michel, 1991, pers.
comm.), the capture cross section for 24Mg. The neutron flux
n results in neutrons/cm2 per second, if P	(21Nen) is inserted
in 21Nen atoms/24Mg atoms per second. P	(21Nen) in these
dimensions is calculated from
P	(21Nen) 
 4.38  1023 P(21Nen), (7)
where P	(21Nen) is obtained from 21Nen and Tpref in Table 3
and from Mg in Table A4:
P(21Nen) 

21Nen
Mg  Tpref. (8)
P(21Nen), given in Table 3, has the dimension
108cm3STP/g per wt.% and Ma. Thus, we use:
n 
 779 P(21Nen). (9)
The resulting (fast) neutron fluxes n(Ne) are given in Table 4.
High n (Ne) values are obtained for the aubrites EET
990033, LEW 87007, and Y 793592, which also contain SW
gas components and, therefore, reveal an evolution in a rego-
lith.
The abundant SW-Ne component in the dark phase of Pe-
syanoe precludes the evaluation of the spallation Ne ratio.
However, the (22Ne/21Ne)c ratios, as well as CRE ages of the
light phase and of the separated enstatite crystals of the dark
phase (Table 3), agree well with each other and permit the use
of approximately constant production rates P21 for Pesyanoe
dark and Pesyanoe light. As indicated earlier, the calculated
irradiation times (T21) for these two phases (Table 3) differ
considerably; this discrepancy documents a preirradiation of
components in the regolith before compaction of the Pesyanoe
aubrite. Furthermore, T21 of the Pesyanoe (dark) sample 90-2,
is higher than all the other Ne ages measured in Pesyanoe. A
complex regolith history is also evident by the identification of
a fractionated solar component, elementally and isotopically
fractionated solar-type gas (Mathew and Marti, 2002, pers.
comm.), and by large neutron-capture effects in Gd and Sm
(Table 1). To infer actual effective neutron fluences, the 80Krn
excesses (Table 1) need to be normalized to Br abundances in
aliquot samples, as the Br abundance is quite variable in
aubrites. Because no Br data are presently available, the neu-
tron fluxes cannot be calculated.
Hidaka et al. (1999) compared the neutron fluences inferred
from Sm of aubrites with those observed on the lunar surface.
These neutron fluences are of the same magnitude. However,
the neutron slowing-down densities may differ, since the ef-
fective capture cross sections are affected by strong resonance
capture on the moon (Lingenfelter et al., 1972) and because of
possible differences in the CR intensity and temperature on the
aubrite parent object at the time of irradiation. Using an inten-
sity of cosmic radiation corresponding to that at solar minimum
in the polar region of the Earth (8.4 n cm2s1) given by
Lingenfelter et al. (1972), a dependence of neutron production
on the average atomic mass of aubrites, and the procedure used
by these authors to estimate the contributions by -mesons and
leakage losses, we estimate a production rate of 17 n cm2s1
for neutrons (E  10 MeV) and an attenuation length of 165 g
cm2. Lingenfelter et al. (1972) pointed out that higher tem-
peratures shift the flux spectrum to higher energies. The capture
Fig. 5. (a) 80Kr/83Kr and 86Kr/83Kr ratios as measured in aubrites.
Cumberland Falls, Khor Temiki, Mayo Belwa, and Shallowater contain
80Krn components in addition to spallation Kr. (b) 82Kr/83Kr and
86Kr/83Kr ratios as measured in aubrites. Cumberland Falls, Mayo
Belwa, Khor Temiki, and Shallowater contain 82Krn components.
564 S. Lorenzetti et al.
rates with the lowest resonances (e.g., 157Gd) decrease, those
with slightly higher energy (e.g., 149Sm) increase, while epith-
ermal resonances are little affected (e.g., 79Br). Such system-
atics may be useful in assessing preirradiation conditions.
To disentangle 2-irradiation effects from space exposure in
4-geometry and to assess neutron capture systematics, we
may take advantage of the large preatmospheric size of Norton
County and of its long CRE age of 111  11 Ma (Table 3) as
a potential standard for 4-irradiation. In this model the CRE
age of Norton County represents the space exposure time.
Regarding neutron effects in Norton County, we obtain an
upper limit for 80Krn of 0.4  1012cm3STP/g (Table 1), an
integral neutron capture rate in 157Gd per initial 157Gd atom of
14.1  104, and in 149Sm per initial 149Sm atom a capture rate
of 6.8  104. The ratio 157Gd/149Sm 
 2.07 is smaller
than the cross-section ratio for thermalized neutrons (157/149

 5.8), indicating that the neutron spectrum was not thermal-
ized. The observed 149Sm loss by neutron capture requires an
average neutron flux of 4.6 n cm2s1 during the CRE age
(using 149 
 4.2  104 barn), which happens to be consistent,
within uncertainties, with the flux inferred for the Abee ensta-
tite chondrite (Hidaka et al., 1999). All other Sm data reported
for aubrites suggest larger neutron fluxes, if the Gd and Sm
anomalies were assigned to 4-irradiation times corresponding
to the CRE data in Table 3. For example, the neutron flux
inferred for the Cumberland Falls aubrite, based on a CRE age
of 60.9  6.0 Ma (Table 3) yields 40 n cm2s1, which far
exceeds the earlier given neutron production rate (E  10
MeV). Cumberland Falls clearly indicates a regolith history.
This evidence is consistent with our results from Krn data and
with the presence of inclusions.
The neutron flux inferred for Bishopville, another member of
the 56  6 Ma cluster, is 20 n cm2 s1, also exceeding the
neutron production rate. In both cases the neutron exposure
time must have been considerably longer than the time indi-
cated by the CRE age. Hidaka et al. (1999) estimated irradia-
tion time intervals for aubrites of several 108 years, as typically
inferred for the lunar regolith. These preirradiation time inter-
vals invalidate the use of nominal (4-geometry) CRE ages,
since a significant fraction of the spallation component was
produced during the regolith history. Therefore, the existence
of a CRE age cluster at 56  6 Ma becomes questionable.
There is also evidence for a 80Kr excess due to neutron irradi-
ation in Khor Temiki (Table 3), another member of this ?clus-
ter.? And there is evidence for solar-type noble gases in Khor
Temiki, Y 793592, and LEW 87007 (Table 5), which requires
a regolith history for these aubrites before compaction into the
present meteorites. We have presented evidence for regolith
evolution for all six members of this cluster. The CRE ages
observed by Eberhardt et al. (1965a) are calculated from the
sum of the noble gases produced during the transfer time and
the preejection exposure on the parent body.
Therefore, a single collisional event, which is usually im-
plied to account for consistent CRE ages, appears doubtful.
Regolith revolution affects generally the spallation data of
meteorites in a different fashion.
5. CONCLUSIONS
We report nominal CRE ages for nine aubrites and reassess
an earlier suggestion that a cluster appears in the CRE histo-
gram. The new data confirm a non-uniform distribution of
exposure times but undermine the significance of clusters in
terms of collisional events, since many aubrites apparently
were preirradiated in a parent body regolith. About one-third of
all aubrites reveal the presence of solar wind (SW) gases, some
show very large neutron-capture anomalies, and some have
inclusions of non-aubritic composition. Table 4 presents infor-
Table 4. Characterization of the aubrites.
Brecciation Inclusions

10 vol %
metallic iron
Shock
blackening Solar 36Ar3) 80Krn4)
n(Ne)
n cm2s1
n (Sm)5)
(n cm2s1)
CRE age
(Ma)
ALH 78113 yes chondritic no 1) 0 ? 14.0 21.8 21.2
ALH 84007 yes none no 1) 0 ? 14.5 ? 26.0
ALH 84011 yes none no 1) 0 ? 14.4 ? 22.0
ALH 84008 yes none no 1) 0 ? 13.6 ? 16.0
ALH 84024 yes none no 1) 0 ? 16.4 ? 14.5
Aubres yes none no no 0 ? 11.1 ? 12.6
Bishopville yes none no no 0 ? 11.4 19.6 52.0
Bustee yes none no no 3.5 ? 12.5 ? 52.6
Cumberland Falls yes chondritic no no 0 15.3 14.1 41.0 60.9
EET 90033/90757 yes none no 2) 1.4 ? 15.0 ? 32.2
Khor Temiki (3m) yes none no no 19.3 0.52 10.5 ? 53.9
LEW 87007 yes none no 2) 10.8 ? 15.1 ? 58.5
Mayo Belwa yes none no yes 0 1.5 10.5 7.4 117
Mt. Egerton no none yes no 0  0.4 ? ? 26.9
Norton County yes none no no 0  0.4 11.7 4.7 111
Pena Blanca Springs yes none no no 0 ? 6.5 ? 72.1
Pesyanoe light yes chondritic ? no no 0.3 ? 10.6 ? 43.2
Pesyanoe dark yes chondritic ? no no 271 ? ? 23.8 47
QUE 97289/97348 no none yes no 0 ? 20.0 ? 40.6
Shallowater no chondritic yes no 0 10.5 5.9 ? 27.0
Y 793592 yes none no yes ? 3.9 ? 18.9 ? 55.0
1) Some ALH samples appear shock-blackened and some do not. We do not have the specific samples to determine if these samples are
shock-blackened. 2) EET 90033, EET 90757, and LEW 87007 are too small to determine shock-blackening. 3) In 108cm3 STP/g. 4) In 1012cm3
STP/g. 5) Calculated from Sm data of Hidaka et al. (1999) and Hidaka, priv. comm. (2001).
565History and origin of aubrites
mation on brecciation, foreign inclusions, neutron effects, and
SW components, which represent the markers of a regolith
breccia. The results confirm earlier reports of very long CRE
ages and indicate orbital elements for its parent body that are
distinct from those of enstatite chondrites. On the other hand,
the actual transfer times may be substantially shorter in cases
where the preirradiation in the regolith accounts for a signifi-
cant fraction of the integral exposure time.
Acknowledgments?We thank the NASA/NSF - Meteorite Working
Group and the National Institute of Polar Research, Tokyo, for the
aubrite samples. Thanks to H. Hidaka, G. Herzog, and two anonymous
reviewers for the useful comments and the help to get it into good
shape. We acknowledge the technical support by Amal Chaoui, Hans-
Erich Jenni, Armin Schaller, and Markus Zuber. This work was sup-
ported by the Swiss National Science Foundation, and in part by NASA
grant NAG5-8167 (to K.M.).
Associate editor: G. Herzog
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567History and origin of aubrites
Table A1. Chemical composition of aubrites (concentrations in wt. %).
Na Mg Al Si K Ca Ti Cr Mn Fe Ni References
ALH aubrites 0.073 23.6 0.16 27.1 0.012 0.46 0.027 0.037 0.13 0.48 0.030 1), 2), 3)
Aubres 0.071 23.4 0.18 27.6 0.052 0.38 0.069 0.027 0.10 0.65 0.034 4), 5)
Bishopville 0.54 21.5 1.09 27.4 0.108 0.92 0.020 0.018 0.030 0.62 0.026 4), 5)
Bustee 0.23 23.0 0.25 26.8 0.014 1.44 0.030 0.026 0.12 0.82 0.018 4), 5)
LEW 87007 0.26 22.6 0.90 27.0 0.05 1.00 0.05 0.02 0.17 0.06 1)
EET aubrites 0.18 22.8 0.26 27.4 0.045 1.02 0.045 0.025 0.10 0.13 1)
Khor Temiki 0.29 22.8 0.50 27.6 0.048 0.47 0.024 0.026 0.05 0.95 0.04 4), 5)
Mayo Belwa 0.95 22.2 0.66 27.8 0.067 0.40 0.035 0.031 0.09 0.33 0.01 4), 5)
Mt. Egerton 0.01 19.0 0.08 23.0 0.25 0.01 0.01 0.03 19.0 1.20 13)
Norton County 0.17 25.0 0.14 25.3 0.012 0.85 0.029 0.032 0.11 1.22 0.027 4), 5), 6), 7)
Pena Blanca Spring 0.28 22.7 0.42 27.2 0.022 0.77 0.042 0.047 0.13 0.49 0.006 4), 5), 6), 8)
Y 793592 0.71 21.4 1.16 26.4 0.091 1.23 0.01 0.017 0.014 0.7 0.32 2)
QUE aubrites 0.56 15.2 1.07 19.8 0.03 0.39 0.17 0.21 0.01 23.0 1.71 1)
Shallowater 0.32 19.7 0.40 23.0 0.026 0.13 0.012 0.027 0.068 13.5 0.73 4), 5)
Pesyanoe (average) 0.12 22.6 0.76 27.3 0.033 0.67 0.033 0.028 0.072 0.56 0.35 4), 10)
(dark) 22.5 0.8 27.0 0.065 0.8 0.04 0.06 0.16 1.2 0.002 9)
(light) 25.8 0.04 27.1 0.003 0.34 0.02 0.01 0.07 0.2 0.002 9)
Pesyanoe (enstatite) 0.015 24.2 0.048 27.8 0.32 0.018 0.02 0.023 0.047 4)
Cumberland Falls (av.) 0.4 23.2 0.11 26.7 0.011 0.45 0.012 0.094 0.062 2.65 0.06 4), 6)
(Fe-rich incl.) 0.93 15.9 1.37 19.7 0.091 1.38 0.093 0.31 0.50 19.25 1.00 11), 12)
Average for Fe-poor (Fe 2%) aubrites
0.34 22.8 0.52 27.1 0.047 0.81 0.034 0.028 0.095 0.59 0.046 1)
1) This work
2) Yanai (1992)
3) Herpers et al. (1995)
4) Watters and Prinz (1979)
5) Easton (1985)
6) Wolf et al. (1983)
7) Wiik (1956)
8) Lodders et al. (1993)
9) Mu?ller and Za?hringer (1966)
10) Djakonowa and Charitonowa (1960)
11) Binns (1969)
12) Jarosewich (1967)
13) Calculated from data of Watters and Prinz (1979) assuming 21 wt. % metal and 79 wt. % enstatite.
568 S. Lorenzetti et al.
Table A2. Trace element abundances (ppm) of aubrites relevant for this work.
Rb Sr Y Zr Br Ba La Ce Nd Th U References
ALH 78113 0.667 2.38 1.18 0.231 0.632 0.429 1)
Aubres 0.605 0.347 0.241 2)
Bishopville 1.91 0.371 0.216 2)
Bustee 0.63 3)
Cumberland Falls 0.64 4)
Khor Temiki 4.3 0.14 5.4 5), 12)
Mayo Belwa 0.14 0.40 6)
Mt. Egerton (silicate) 0.111 0.06 2)
Norton County 0.084 1.4 2.6 3.15 2), 4), 7), 8)
Pen?a Blanca Spring 0.289 0.27 1.2 0.075 2), 9)
Pesyanoe (average) 1.67 3)
(dark) 2.41 0.28 10), 2)
(light) 0.26 10)
Pesyanoe enstatite 0.134 2)
Shallowater 0.86 0.051 3), 11)
Average for Fe-poor (Fe 2%) aubrites
0.93 1.9 3.45 0.23 3.24 0.21 0.59 0.24
Average given by Mason (1978). Figures in parentheses are number of meteorites analyzed.
1.81 1.4 2.09 0.9 0.14 2 0.21 0.81 0.63 0.028 0.0045
(2) (1) (1) (2) (2) (1) (1) (1) (1) (2) (2)
1) Shimizu and Masuda (1981)
2) Wolf et al. (1983)
3) Biswas et al. (1980)
4) Ehmann and Rebagay (1970)
5) Burger et al. (1989)
6) Graham and Henderson (1985)
7) Von Michaelis et al. (1969)
8) De Laeter and Hosie (1978)
9) Lodders et al. (1993)
10) Laul et al. (1972)
11) Keil et al. (1989)
12) Eugster (1967)
569History and origin of aubrites
Table A3. Results of He, Ne, and Ar measurements.
Sample
weight
(mg)
4He 20Ne 40Ar 4He 20Ne 22Ne 36Ar 40Ar
108cm3STP/g 3He 22Ne 21Ne 38Ar 36Ar
ALH 84007,95 20.10 295  9 13.8 0.4 69.8  5.0 6.11 0.06 0.863  0.016 1.075  0.011 1.00  0.10 304  20
ALH 84024,11 20.72 200  6 9.54  0.30 92.0  5.0 7.43 0.08 0.950  0.010 1.089  0.011 2.09  0.12 249  20
30.13 114  3 7.22 0.30 60.0 3.5 7.12 0.07 0.898  0.010 1.084  0.012 1.80  0.10 229  17
20.04 162  5 7.65 0.25 67.5 6.0 6.97 0.12 0.887  0.010 1.067  0.011 1.82  0.20 225  20
20.44 180  6 8.87 0.25 73.4 6.0 6.85 0.07 0.878  0.009 1.063  0.011 1.83  0.17 218  20
ALH 84024,15 21.41 171  5 8.87 0.25 53.8 5.0 6.05 0.07 0.837  0.016 1.079  0.020 1.66  0.25 314  40
ALH 84024 average 165  20 8.43 0.70 69.3 10.0 6.88 0.40 0.890  0.30 1.079  0.010 1.84  0.10 247  30
EET 90033,7 21.17 782  24 45.6 2.0 1350  55 12.0 0.1 1.90  0.02 1.19  0.01 1.86  0.03 690  20
32.10 351  11 27.7 0.8 1206  40 13.2 0.1 1.58  0.02 1.17  0.02 1.89  0.03 904  20
20.61 773  23 52.40 1.6 1654 55 15.5 0.2 2.24  0.02 1.18  0.02 2.08  0.04 757  20
21.17 593  18 43.9 1.4 1521  50 14.8 0.2 2.10  0.02 1.19  0.02 2.15  0.04 723  20
average 625 110 42.4 5.0 1433  90 13.9 0.2 1.96  0.15 1.18  0.01 2.00  0.07 768  45
EET 90757,9 21.51 74.4  2.0 15.9 0.7 263  10 6.70 0.08 0.855  0.010 1.123  0.020 1.04  0.04 490  25
30.13 71.6  2.0 15.9 0.5 289  10 6.63 0.07 0.870  0.015 1.098  0.011 1.02  0.03 580  20
average 73.0 2.0 15.9 0.5 276  13 6.66 0.07 0.862  0.010 1.110  0.013 1.03  0.03 535  45
LEW 87007,11 20.19 193?000  16?000 461 18 13?200  1?000 1	063  12 6.52  0.07 2.15  0.03 3.68  0.05 1	060  40
31.74 114?100  3?500 359 11 5?710  200 1	027  11 6.08  0.06 2.00  0.02 3.42  0.04 566  10
5.48 145?500  6?500 399 17 7?890  250 969  10 6.32  0.06 1.97  0.03 3.18  0.08 675  20
4.99 148?800  12?000 425 13 7?410  250 965  10 6.22  0.07 1.98  0.02 3.42  0.10 622  15
average 150?400  16?000 411 20 8?550  1?700 1	006  25 6.29  0.08 2.02  0.04 3.42  0.09 731  110
Pesyanoe
enstatite
crystal 1
15.14 1?199  40 22.8  0.7 111.8  7.0 15.3  0.2 0.951  0.017 1.106  0.012 1.98  0.10 156  12
Pesyanoe
enstatite
crystal 2
16.41 550  17 19.9 0.6 247  10 7.10 0.07 0.862  0.010 1.116  0.020 1.20  0.07 492  30
Pesyanoe-90.2 24.53 853?600  48?400 4?290  130 4?620  140 2?605  145 11.07 0.11 8.91  0.09 4.94  0.05 30.9  0.3
QUE 97280,7 20.75 830  25 17.7 0.5 2?232  70 11.6  1.4 0.873  0.010 1.036  0.011 3.36  0.04 288  6
QUE 97348,6 20.59 190  6 14.8 0.5 2?246  70 7.38  0.08 0.970  0.009 1.029  0.011 3.02  0.06 345  8
Y 793592,86 20.88 9?040  350 172  5 5?241  160 94.8  0.9 3.49  0.04 1.38  0.02 2.64  0.04 1123  20
20.20 8?072  300 160  5 5?322  160 101.1  1.0 3.49  0.04 1.38  0.01 2.61  0.04 1134  20
average 8?556  400 166  5 5?282  160 98.0  1.0 3.49  0.04 1.38  0.02 2.62  0.04 1128  20
570
S.Lorenzetti
et
al.
Table A4. Aubrite analyses of other workers from the compilation of Schultz and Franke (2000).
Reference
4He 20Ne 40Ar 4He 20Ne 22Ne 36Ar 40Ar
108cm3STP/g 3He 22Ne 21Ne 38Ar 36Ar
ALH 78113 1) 427 10.6 1?220 12.00 0.845 1.090 1.45 1?584
ALH 84007 2) 338 12.67 330 8.00 0.850 1.090 2.33 524
ALH 84008 2) 313 8.06 620 12.08 0.851 1.100 2.36 939
ALH 84011 2) 295 11.23 400 8.17 0.844 1.090 2.79 597
Aubres 3) 208 5.50 454 15.07 0.833 1.119 2.11 1?195
Bishopville 4), 5) 638 21.3 5?370 6.95 0.854 1.112 1.58 9?944
Bustee 3), 6) 7?800 143 1?860 86.2 3.73 1.468 2.08 516
Cumberland Falls
Fe-poor
3), 5), 7) 309 27.0 573 10.6 0.853 1.091 1.52 474
Cumberland Falls
Fe-rich
5) 430 24.5 1?425 17.6 0.914 1.094 2.00 509
Khor Temiki
enstatite
8) 500 21.4 220 5.41 0.786 1.122 1.31 863
Mayo Belwa 9) 1?825 47.2 8?250 10.25 0.807 1.129 1.07 3?784
Norton County 4), 5), 10) 1?544 52.0 470 7.52 0.869 1.099 0.794 272
Pena Blanca Spring 5) 1?090 24.7 650 9.16 0.837 1.185 1.25 650
Pesyanoe light 11) 2?680 24.5 173 30.5 1.109 1.122 1.71 171
Pesyanoe dark 11) 1?068?000 3	610 4?620 2	507 11.5 14.8 5.33 17.0
Shallowater 3) 277 7.90 2?010 6.30 0.868 1.197 5.34 99
For data selection criteria see text. For each meteorite average values were calculated. References: 1) Vogt et al. (1986); 2) Herpers et al. (1995);
3) Eberhardt et al. (1965a); 4) Levsky (1972); 5) Mu?ller and Za?hringer (1969); 6) Poupeau et al. (1974); 7) Za?hringer (1968); 8) Eberhardt et al.
(1965c); 9) Heusser et al. (1978); 10) Herzog et al. (1977); 11) Mu?ller and Za?hringer (1966).
Table A5. Results of Kr measurements.
86Kr 78Kr 80Kr 82Kr 83Kr 84Kr 83Krc 80Krn
(80Kr/82Kr)n
83Krcage
1012cm3STP/g 86Kr 
 100 1012cm3STP/g 1012 cm3STP/g Ma
Norton County 19  3 4.57  0.18 25.4  0.7 8  3 86  3 343  15 3  0.6 106
Cumberland Falls 20  3 3.62  0.13 94  1.2 100.3  2.6 74.8  2.7 324  13 1.94  0.29 15.3  2.3 2.7  0.4 53  12
Mount Egerton 26  4 2.1  0.06 13.6  0.4 65.7  1.7 65.1  1.9 323  9
Mayo Belwa 26  4 3.86  0.09 26.8  0.5 79.1  1.5 80.1  1.5 340  7 3.8  0.6 1.5  0.2 105  23
Shallowater 308  46 2.04  0.02 16.62  0.19 67.7  0.6 65.9  0.6 325  3 2.2  0.3 10.8  1.6 1.7  0.8 59  13
571History and origin of aubrites