The Allende fine-grained inclusion Curious Marie is a unique CAI. It is depleted in uranium but contains large ^(235)U excess [1], providing new evidence that ^(247)Cm was alive in the Early Solar System, as has been previously suggested [2], and leading to an updated (^(247)Cm/^(235)U)initial ratio of (1.1±0.3)×10^(-4)

Dauphas, N.

Meshik, A.

Pravdivtseva, O.

Tissot, F. L. H.

Caltech Authors - Main

I-Xe  STUDIES  OF  AQUEOUS  ALTERATION  IN  THE  ALLENDE  CAI  CURIOUS  MARIE.  O. Prav-
divtseva1, A. Meshik1, F. L. H. Tissot2, N. Dauphas3. 1Laboratory for Space Sciences and Physics Department, 
Washington University, CB1105, One Brookings Drive, Saint Louis, MO 63130 (olga@physics.wustl.edu), 2 De-
partment of the Earth, Atmospheric and Planetary Sciences, MIT, Cambridge 02139, 3 Origins Lab, The University 
of Chicago. 
 
 
Introduction:  The Allende fine-grained inclusion 
Curious Marie is a unique CAI.  It is depleted in ura-
nium but contains large 235U excess [1], providing new 
evidence that 247Cm was alive in the Early Solar Sys-
tem, as has been previously suggested [2], and leading 
to an updated (247Cm/235U)initial ratio of (1.1±0.3)×10-4.   
A model initial 26Al/27Al ratio [(6.2 ± 0.9) ×10-5 has 
been calculated for Curious Marie using its bulk 
Al/Mg ratio and the uniform δ26Mg* ~ +4‰ [3] which 
is similar to the canonical initial solar system value 
within error.  This implies not only an early condensa-
tion of the CAI precursor, but also an early onset for 
the aqueous alteration as well. If this episode of aque-
ous alteration was responsible for the depletion of U in 
Curious Marie, the initial solar system value for 
247Cm/235U ratio is  (5.6±0.3)×10-5 [3]. 
Curious Marie, an extremely altered U-depleted fi-
ne-grained CAI, characterized by a group II REE pat-
tern with extensive replacement of high-T phases by 
low-T alteration products such as nepheline and soda-
lite. I-Xe chronometry for coarse- and fine-grained 
Allende CAIs have been previously reported [4,5] with 
I-Xe ages reflecting the time of alteration. To better 
delineate the aqueous alteration sequence in Allende 
CAIs we analyzed Ne, Ar, Kr and Xe isotopic compo-
sitions in Curious Marie CAI.  Here we discuss Xe 
isotopic composition and the I-Xe chronometry for this 
sample.   
Experimental: 27.1 mg of Curious Marie was ex-
tracted using dental tools under a stereoscopic micro-
scope. The sample was split into two aliquots, 6.7 mg 
and 20.4 mg.  The smaller one, together with the Shal-
lowater standard, was irradiated in the Missouri Uni-
versity Research Reactor (MURR), receiving  2×1019 
n/cm2. 
Xe from irradiated Curious Marie CAI was re-
leased in step-wise heating extractions in the W coil of 
our resistance furnace starting with 800C and up to 
the melting of Pt (1770°C), with 50°C steps in 1100‒
1700°C interval. The isotopic composition of the re-
leased Xe was measured by high transmission ion-
counting mass spectrometry [6] with sensitivity for 
132Xe of 5.88×10-16 cm3 STP/count. Unirradiated Curi-
ous Marie CAI was analyzed following the same step-
wise heating protocol, but in that sample, we also 
measured the isotopic compositions of Ne, Ar and Kr.  
Results:  Xe in both Curious Marie aliquots is 
dominated by natural radiogenic Xe components. Con-
centrations of 129*Xe are 3×103 higher than the trapped 
132Xe, with yet smaller additions of fission Xe. Anal-
yses of the unirradiated Curious Marie aliquot revealed 
80,82Kr contributions from natural neutron-capture on 
79,81Br, with 80Kr/82Kr ratio of 2.6, similar to what was 
previously reported for Allende inclusions [7]. A cos-
mogenic neutron contribution was also observed as 
excess 128Xe. In the unirradiated sample it resulted in a 
correlation between radiogenic 129Xe (from 129I decay) 
and 128Xe (from cosmogenic neutron capture). The 
129Xe/132Xe versus 128Xe/132Xe isochron for the MURR 
irradiated sample is ~1000 greater than for the natural-
ly irradiated sample. This means Curious Marie expe-
rienced a thermal equivalent cosmogenic neutron flu-
ence of 2×1016 n/cm2. 
Irradiation in the reactor with the thermal neutrons 
fluence of  2×1019 n/cm2 results in the 128*Xe concen-
trations that are compatible with those for 129*Xe, with 
typical 129Xe/128Xe ratios that are ~ 1. So, for the irra-
diated Curious Marie CAI, contribution to 128Xe from 
the cosmogenic component constitute only about 0.1% 
of the total measured 128Xe, and its effect on the result-
ing I-Xe age is negligible. Three-isotope plot for the 
irradiated Curious Marie aliquot is shown in Figure1.  
 
 Figure 1. Three-isotope plot for the Allende Curious 
Marie CAI. The I-Xe isochrons (free-fit, not forced 
through Q-Xe) correspond to low- and high-
temperature releases of radiogenic Xe.  
 
Q-Xe
0
300
600
900
1200
0 400 800 1200 1600
slope = 0.767 ± 0.025
1550
1450
1350
1400 1250
1300
1500
1600
1650
1770
1700
slope = 0.829 ± 0.011
Allende fine-grained CAI
Curious Marie
129
Xe
/130
Xe
128Xe/130Xe
2959.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
Apparently, the I-Xe system survived intact in two 
different mineral phases in Curious Marie, contrary to 
what was previously observed for Allende CAIs [4]. 
The difference in slopes of the two isochrons corre-
sponds to a difference in closure times of 1.8 ± 0.4 Ma 
for these two phases (Fig1), independent of other fac-
tors.  Relative to the Shallowater standard (4562.4 ± 
0.2 Ma [8]), the low- and high-temperature host phases 
closed 3.2 ± 0.7 Ma and 1.4 ± 0.2 Ma after that stand-
ard, corresponding to absolute closure times of 4559.2 
± 0.7 Ma and 4561.0 ± 0.2 Ma. 
 Figure 2. The observed fission compositions in the 
Allende Curious Marie aliquots.  
The release profiles of fission Xe differed for the 
irradiated and unirradiated Curious Marie samples, 
suggesting multiple parent isotopes. Likely parents of 
fission Xe in meteorites are 238U (t1/2 = 4.47×109 y), 244Pu (t1/2 = 8.0×107 y) and 248Cm (t1/2 = 3.4×105 y) [9]. 
Presence of life 247Cm at the closure time of the I-Xe 
system will manifest itself only in the neutron irradiat-
ed sample since 247Cm decays into 235U. Both samples 
have major release peaks corresponding to the low-
temperature carrier phase. The observed fission com-
position in this peak for both samples is consistent with 
Xe from the spontaneous decay of 244Pu. The release 
profile of fission 132Xe for the irradiated Curious Marie 
aliquot also had smaller peak at 1600‒1650C tem-
perature steps (Fig.2), most likely due to neutron-
induced fission of 235U. 136Xe is always over represent-
ed in the neutron irradiated samples due to neutron 
capture on live 135Xe (T1/2 = 9.10 h) (235U*, Fig.2).  
The observed difference in the release profiles of 
the irradiated and unirradiated Curious Marie samples 
suggests that U is most likely associated with the high-
temperature iodine-carrier phase.  
Low-temperature iodine-carrier phase in both Cu-
rious Marie aliquots demonstrated 130Xe excesses that 
were not accompanied by excesses on 124Xe, expected 
in case of the spallation contribution (Fig3). We ob-
served similar excess in the same temperature range in 
one of the previously analyzed fine-grained Allende 
CAIs [4]. This may well be due to neutron capture on 
129Xe, phenomena observed in the (natural) neutron-
irradiated Oklo samples [9]. This is, however, also 
consistent with Xe component of noble gases carried 
by pre-solar grains of silicon carbide and points to the 
possibility that pre-solar SiC grains survived in CAIs.  
 Figure 3. Three-isotope plot for the unirradiated Cu-
rious Marie.  
Curious Marie has proven to be an unusual CAI, 
where two iodine-carrier phases preserved chronologi-
cal information. Uranium is most likely associated 
with a high-temperature phase in this sample. If the I-
Xe age of this phase of 4561.0 ± 0.2 Ma reflects the 
time of U loss, the initial 247Cm/235U ratio is higher 
than (5.6±0.3)×10-5.  The 130Xe excess associated with 
the low temperature iodine carrier phase suggests that 
pre-solar SiC may have survived processing of the CAI 
precursor material. 
Supported by NASA grants NNX13AD14G. 
References: [1] Tissot F.L H. et al. (2016) LPSC 
47, Abstract#1605. [2] Brennecka G. et al. (2010) Sci-
ence 327, 449–451. [3] Tang et al. (2017) GCA 207, 
1‒18. [3] Swindle T. et al. (1988) GCA 52, 2215–2229. 
[4] Pravdivtseva O. et al. (2003) GCA 67, 5011–5026.  
[5] Hohenberg C. M. (1980) Rev. Sci. Instrum. 51, 
1075–1082. [6] Göbel R. et al. (1982) GCA 46, 1777–
1792. [7] Pravdivtseva O. et al. (2017). GCA 201, 320–
330. [8] Ming T. and Anders E. (1988) GCA 52, 1235–
1244. [9] Meshik A. et al. (2004) PRL 93, 182302-1. 
0
0.4
0.8
1.2
1.6
2
244Pu
238U
235U
Q-Xe
134Xe/132Xe
136
Xe
/132
Xe
Allende fine-grained CAI
Curious Marie (unirradiated)
0
0.4
0.8
1.2
1.6
2
0 0.5 1 1.5 2
Allende fine-grained CAI
Curious Marie (irradiated)
Q-Xe
238U
235U
244Pu
235U*
16501600
0
0.4
0.8
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
1400
to Xe-S
130Xe/132Xe
13
1 Xe
/132
Xe 12501300
1200
1350
14501550
1500
244Pu
238U
248Cm
235U
Q-Xe
Xe-HL
Allende fine-grained CAI
Curious Marie (unirradiated)
2959.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)


I-Xe studies of aqueous alteration in the Allende CAI Curious Marie

I-Xe  STUDIES  OF  AQUEOUS  ALTERATION  IN  THE  ALLENDE  CAI  CURIOUS  MARIE.  O. Prav-
divtseva1, A. Meshik1, F. L. H. Tissot2, N. Dauphas3. 1Laboratory for Space Sciences and Physics Department, 
Washington University, CB1105, One Brookings Drive, Saint Louis, MO 63130 (olga@physics.wustl.edu), 2 De-
partment of the Earth, Atmospheric and Planetary Sciences, MIT, Cambridge 02139, 3 Origins Lab, The University 
of Chicago. 
 
 
Introduction:  The Allende fine-grained inclusion 
Curious Marie is a unique CAI.  It is depleted in ura-
nium but contains large 235U excess [1], providing new 
evidence that 247Cm was alive in the Early Solar Sys-
tem, as has been previously suggested [2], and leading 
to an updated (247Cm/235U)initial ratio of (1.1±0.3)×10
-4.   
A model initial 26Al/27Al ratio [(6.2 ± 0.9) ×10-5 has 
been calculated for Curious Marie using its bulk 
Al/Mg ratio and the uniform δ26Mg* ~ +4‰ [3] which 
is similar to the canonical initial solar system value 
within error.  This implies not only an early condensa-
tion of the CAI precursor, but also an early onset for 
the aqueous alteration as well. If this episode of aque-
ous alteration was responsible for the depletion of U in 
Curious Marie, the initial solar system value for 
247Cm/235U ratio is  (5.6±0.3)×10-5 [3]. 
Curious Marie, an extremely altered U-depleted fi-
ne-grained CAI, characterized by a group II REE pat-
tern with extensive replacement of high-T phases by 
low-T alteration products such as nepheline and soda-
lite. I-Xe chronometry for coarse- and fine-grained 
Allende CAIs have been previously reported [4,5] with 
I-Xe ages reflecting the time of alteration. To better 
delineate the aqueous alteration sequence in Allende 
CAIs we analyzed Ne, Ar, Kr and Xe isotopic compo-
sitions in Curious Marie CAI.  Here we discuss Xe 
isotopic composition and the I-Xe chronometry for this 
sample.   
Experimental: 27.1 mg of Curious Marie was ex-
tracted using dental tools under a stereoscopic micro-
scope. The sample was split into two aliquots, 6.7 mg 
and 20.4 mg.  The smaller one, together with the Shal-
lowater standard, was irradiated in the Missouri Uni-
versity Research Reactor (MURR), receiving  2×1019 
n/cm2. 
Xe from irradiated Curious Marie CAI was re-
leased in step-wise heating extractions in the W coil of 
our resistance furnace starting with 800C and up to 
the melting of Pt (1770°C), with 50°C steps in 1100‒
1700°C interval. The isotopic composition of the re-
leased Xe was measured by high transmission ion-
counting mass spectrometry [6] with sensitivity for 
132Xe of 5.88×10-16 cm3 STP/count. Unirradiated Curi-
ous Marie CAI was analyzed following the same step-
wise heating protocol, but in that sample, we also 
measured the isotopic compositions of Ne, Ar and Kr.  
Results:  Xe in both Curious Marie aliquots is 
dominated by natural radiogenic Xe components. Con-
centrations of 129*Xe are 3×103 higher than the trapped 
132Xe, with yet smaller additions of fission Xe. Anal-
yses of the unirradiated Curious Marie aliquot revealed 
80,82Kr contributions from natural neutron-capture on 
79,81Br, with 80Kr/82Kr ratio of 2.6, similar to what was 
previously reported for Allende inclusions [7]. A cos-
mogenic neutron contribution was also observed as 
excess 128Xe. In the unirradiated sample it resulted in a 
correlation between radiogenic 129Xe (from 129I decay) 
and 128Xe (from cosmogenic neutron capture). The 
129Xe/132Xe versus 128Xe/132Xe isochron for the MURR 
irradiated sample is ~1000 greater than for the natural-
ly irradiated sample. This means Curious Marie expe-
rienced a thermal equivalent cosmogenic neutron flu-
ence of 2×1016 n/cm2. 
Irradiation in the reactor with the thermal neutrons 
fluence of  2×1019 n/cm2 results in the 128*Xe concen-
trations that are compatible with those for 129*Xe, with 
typical 129Xe/128Xe ratios that are ~ 1. So, for the irra-
diated Curious Marie CAI, contribution to 128Xe from 
the cosmogenic component constitute only about 0.1% 
of the total measured 128Xe, and its effect on the result-
ing I-Xe age is negligible. Three-isotope plot for the 
irradiated Curious Marie aliquot is shown in Figure1.  
 
 
Figure 1. Three-isotope plot for the Allende Curious 
Marie CAI. The I-Xe isochrons (free-fit, not forced 
through Q-Xe) correspond to low- and high-
temperature releases of radiogenic Xe.  
 
Q-Xe
0
300
600
900
1200
0 400 800 1200 1600
slope = 0.767 ± 0.025
1550
1450
1350
1400
1250
1300
1500
1600
1650
1770
1700
slope = 0.829 ± 0.011
Allende fine-grained CAI
Curious Marie
12
9 X
e/
13
0 X
e
128Xe/130Xe
2959.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
Apparently, the I-Xe system survived intact in two 
different mineral phases in Curious Marie, contrary to 
what was previously observed for Allende CAIs [4]. 
The difference in slopes of the two isochrons corre-
sponds to a difference in closure times of 1.8 ± 0.4 Ma 
for these two phases (Fig1), independent of other fac-
tors.  Relative to the Shallowater standard (4562.4 ± 
0.2 Ma [8]), the low- and high-temperature host phases 
closed 3.2 ± 0.7 Ma and 1.4 ± 0.2 Ma after that stand-
ard, corresponding to absolute closure times of 4559.2 
± 0.7 Ma and 4561.0 ± 0.2 Ma. 
 
Figure 2. The observed fission compositions in the 
Allende Curious Marie aliquots.  
The release profiles of fission Xe differed for the 
irradiated and unirradiated Curious Marie samples, 
suggesting multiple parent isotopes. Likely parents of 
fission Xe in meteorites are 238U (t1/2 = 4.47×10
9 y), 
244Pu (t1/2 = 8.0×10
7 y) and 248Cm (t1/2 = 3.4×10
5 y) [9]. 
Presence of life 247Cm at the closure time of the I-Xe 
system will manifest itself only in the neutron irradiat-
ed sample since 247Cm decays into 235U. Both samples 
have major release peaks corresponding to the low-
temperature carrier phase. The observed fission com-
position in this peak for both samples is consistent with 
Xe from the spontaneous decay of 244Pu. The release 
profile of fission 132Xe for the irradiated Curious Marie 
aliquot also had smaller peak at 1600‒1650C tem-
perature steps (Fig.2), most likely due to neutron-
induced fission of 235U. 136Xe is always over represent-
ed in the neutron irradiated samples due to neutron 
capture on live 135Xe (T1/2 = 9.10 h) (
235U*, Fig.2).  
The observed difference in the release profiles of 
the irradiated and unirradiated Curious Marie samples 
suggests that U is most likely associated with the high-
temperature iodine-carrier phase.  
Low-temperature iodine-carrier phase in both Cu-
rious Marie aliquots demonstrated 130Xe excesses that 
were not accompanied by excesses on 124Xe, expected 
in case of the spallation contribution (Fig3). We ob-
served similar excess in the same temperature range in 
one of the previously analyzed fine-grained Allende 
CAIs [4]. This may well be due to neutron capture on 
129Xe, phenomena observed in the (natural) neutron-
irradiated Oklo samples [9]. This is, however, also 
consistent with Xe component of noble gases carried 
by pre-solar grains of silicon carbide and points to the 
possibility that pre-solar SiC grains survived in CAIs.  
 Figure 3. Three-isotope plot for the unirradiated Cu-
rious Marie.  
Curious Marie has proven to be an unusual CAI, 
where two iodine-carrier phases preserved chronologi-
cal information. Uranium is most likely associated 
with a high-temperature phase in this sample. If the I-
Xe age of this phase of 4561.0 ± 0.2 Ma reflects the 
time of U loss, the initial 247Cm/235U ratio is higher 
than (5.6±0.3)×10-5.  The 130Xe excess associated with 
the low temperature iodine carrier phase suggests that 
pre-solar SiC may have survived processing of the CAI 
precursor material. 
Supported by NASA grants NNX13AD14G. 
References: [1] Tissot F.L H. et al. (2016) LPSC 
47, Abstract#1605. [2] Brennecka G. et al. (2010) Sci-
ence 327, 449–451. [3] Tang et al. (2017) GCA 207, 
1‒18. [3] Swindle T. et al. (1988) GCA 52, 2215–2229. 
[4] Pravdivtseva O. et al. (2003) GCA 67, 5011–5026.  
[5] Hohenberg C. M. (1980) Rev. Sci. Instrum. 51, 
1075–1082. [6] Göbel R. et al. (1982) GCA 46, 1777–
1792. [7] Pravdivtseva O. et al. (2017). GCA 201, 320–
330. [8] Ming T. and Anders E. (1988) GCA 52, 1235–
1244. [9] Meshik A. et al. (2004) PRL 93, 182302-1. 
0
0.4
0.8
1.2
1.6
2
244Pu
238U
235U
Q-Xe
134Xe/132Xe
13
6 X
e/
13
2 X
e
Allende fine-grained CAI
Curious Marie (unirradiated)
0
0.4
0.8
1.2
1.6
2
0 0.5 1 1.5 2
Allende fine-grained CAI
Curious Marie (irradiated)
Q-Xe
238U
235U
244Pu
235U*
1650
1600
0
0.4
0.8
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
1400
to Xe-S
130Xe/132Xe
13
1 X
e/
13
2 X
e
1250
1300
1200
1350
14501550
1500
244Pu
238U
248Cm
235U
Q-Xe
Xe-HL
Allende fine-grained CAI
Curious Marie (unirradiated)
2959.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)


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I-Xe studies of aqueous alteration in the Allende CAI Curious Marie

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