Fujiya, W.

Fukuda, K.

Hoppe, P.

Koike, M.

Lee, M.R.

Lindgren, P.

Sano, Y.

Shirai, K.

English

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CARBON ISOTOPIC RATIOS OF CARBONATE IN CM CHONDRITES AND THE TAGISH LAKE 
METEORITE. W. Fujiya1, P. Hoppe2, K. Fukuda3, P. Lindgren4, M. R. Lee5, M. Koike6, K. Shirai6, and Y. Sano6. 
1Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan (wataru.fujiya.sci@vc.ibaraki.ac.jp), 2Max Planck 
Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany, 3The University of Tokyo, 7-3-1 Hongo, 
Bunkyo-ku, Tokyo 113-0033, Japan, 4Lund University, Sölvegatan 12, 223 62 Lund, Sweden, 5University of Glas-
gow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, Scotland, 6Atmosphere and Ocean Research Insti-
tute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan. 
 
 
Introduction: Carbonate minerals are ubiquitous in 
CM chondrites and formed by aqueous alteration in the 
parent body. Previous studies have shown that C iso-
topic ratios of CM carbonates are highly variable at 
whole-rock scales as well as among individual grains in 
single meteorites [e.g., 1-3]. Despite extensive studies 
on C isotopic ratios of CM carbonates, the reasons for 
the variability in 13C values and the origin of the car-
bon in carbonates remain poorly understood. 
The Tagish Lake meteorite is an ungrouped carbo-
naceous chondrite that is believed to be derived from a 
D-type asteroid [4]. The C isotopic ratios of carbonates 
in Tagish Lake were measured for whole-rock samples 
[5], but as yet there are no measurements on individual 
grains. Therefore, the variation in C isotopic ratios has 
not been investigated for the Tagish Lake carbonates. 
Here we report C isotopic ratios of individual cal-
cite (CaCO3) grains in the LaPaz Icefield (LAP) 
031166 CM chondrite (CM 2.1), and of both calcite 
and dolomite (CaMg(CO3)2) grains in the Tagish Lake 
meteorite. We discuss the origin of the carbon in car-
bonates and explore a possible link between ice in CMs 
and Tagish Lake and cometary ice. 
Experimental: Carbon-isotope analysis on the cal-
cite grains in LAP 031166, whose O isotopic ratios 
were previously reported by Lindgren et al. [6], was 
performed with the NanoSIMS 50 at the Atmosphere 
and Ocean Research Institute, The University of To-
kyo. Negative secondary ions of 12C, 13C, 18O, 12C14N, 
and 28Si, produced by rastering a Cs+ primary ion beam 
(20-30 pA, ~1 m in diameter) over 6 x 6 m2 sized 
areas, were detected simultaneously with five electron 
multipliers. 
Carbon-isotope analyses on calcite and dolomite 
grains in Tagish Lake were performed with the Na-
noSIMS 50 at the Max Planck Institute for Chemistry, 
Mainz. Compared with CM carbonates, carbonate 
grains in Tagish Like are small (typically <10 m). 
Thus, we measured C isotopic ratios by recording ion 
images of 12C-, 13C-, 18O-, 12C14N-, and 28Si- (3 x 3 m2) 
produced with a Cs+ primary ion beam (~10 pA, ~a few 
100’s nm in diameter). 
Results and Discussion: The 13CPDB and 
18OSMOW values of the calcite grains in LAP 031166 
are plotted in Fig. 1, together with literature data of Ca-
carbonate in CM chondrites [2,3,7]. Figure 2 shows 
the13C values of the calcite and dolomite grains in 
Tagish Lake. Also shown in Fig. 2 are data obtained by 
acid dissolution of whole-rock samples [5]. 
0
20
40
60
80
100
15 20 25 30 35 40 45
Paris (Vacher et al., 2017)
Nogoya (Fujiya et al., 2016)
Murchison (Fujiya et al., 2015)
LAP 031166 (This study)

1
3
C
 (
p
e
rm
il)
18O (permil)
 
Fig. 1: 13C and 18O values of Ca-carbonate grains in 
CM chondrites. 
 
0
20
40
60
80
100

1
3
C
 (
p
e
rm
il)
Calcite
(This study)
Dolomite
(This study)
Bulk calcite
Grady et al. (2002)
Bulk dolomite
Grady et al. (2002)
Fig. 2: 13C values of carbonate grains in Tagish Lake. 
 
1377.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
An apparent contrast between carbonates in CMs 
and Tagish Lake can be seen: the 13C values of CM 
carbonates are highly variable, ranging from ~20 to 
80‰, whereas all Tagish Lake carbonates have high 
13C values of ~70‰, which are consistent with whole-
rock analyses [5]. The 18O values of CM carbonates 
range from ~15 to 40‰, and show no systematic corre-
lation with corresponding 13C values (Fig. 1). 
To explain these observations, we propose here 
mixing of at least two C reservoirs with different 13C 
values. The candidates of C reservoirs which may have 
contributed to the carbonate C include CO2 and CO 
accreted as ice, and organic matter. CO2 is the major C-
bearing species in cometary ice [10]. 
If C from organic matter contributed to the car-
bonate C, organic matter must have been oxidized to 
CO2 which requires strong oxidants such as peroxide 
[1,8]. The upper limit on the amounts of CO2 produced 
by oxidation of organic matter with peroxide is esti-
mated to be ~0.1 wt% [1], which is far smaller than the 
carbonate C abundance of Tagish Lake (~1.3 wt% [5]). 
Furthermore, no organic components with high 13C 
values of >80‰ have been identified, except for anom-
alous organic grains found in insoluble organic matter 
(IOM) from a CR chondrite [9]. Thus, the C reservoir 
with a high 13C value is almost certainly CO2 accreted 
as ice, which likely had a 13C value of >80‰. Interest-
ingly, the 13C value of CO2 in the coma of comet 
67P/Churyumov-Gerasimenko measured by Rosetta 
(64 ± 45‰ [11]) is consistent with the conclusion 
above. On the other hand, the C reservoir(s) with a low 
13C value is poorly constrained: both organic matter 
and CO are possible. The 13C values of IOM in CMs 
and Tagish lake are from -17 to -19‰ and from -13 to 
-15‰, respectively [12,13]. The 13C value of trapped 
CO in Murchison is approximately -32‰ [14].  
Here we assume that the 13C value of CO2 ice is 
80‰. Also, we assume that other C reservoirs (i.e., 
organic matter or CO) with low 13C values from -10 to 
-30‰ contributed to the carbonate C. The fact that 
Tagish Lake carbonates have homogenous and high 
13C values indicates larger contribution from CO2 ice 
to the Tagish Lake carbonates than the CM carbonates. 
The abundance of the carbonate C in Tagish Lake is 
~1.3 wt% and the 13C value of the Tagish Lake car-
bonates is ~70‰ as determined for whole-rock samples 
[5]. Thus, from mass balance calculation, CO2 ice ac-
counts for 89-91% of the carbonate C in Tagish Lake. 
Likewise, the average abundance of the carbonate C in 
CMs is ~0.17 wt% and the average 13C value of CM 
carbonates is ~45‰ [1]. For the case of CMs, CO2 ice 
accounts for 61-68% of the carbonate C. 
Based on the values above and water contents esti-
mated by subtracting H in organic matter from the bulk 
H contents [12,13,15], we can calculate CO2/H2O mole 
ratios of ice accreted to the CM and Tagish Lake par-
ent bodies to be ~0.018 and ~0.28, respectively. The 
CO2/H2O mole ratios of CM and Tagish Lake ice are 
compared with those of cometary ice in Fig. 3 (comet 
data from [16]). The CO2/H2O ratio of the CM ice is 
smaller than in any comet while the Tagish Lake ice 
has a CO2/H2O ratio within the range of comets (close 
to the upper limit). These observations may suggest a 
genetic link between D-type asteroids and comets. On 
the other hand, the CM parent body may have accreted 
closer to the Sun (and therefore, at higher temperature) 
than D-type asteroids and comets where CO2 ice par-
tially sublimated. 
0
1
2
3
4
5
6
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Jupiter-family comets
Oort cloud comets
F
re
q
u
e
n
c
y
CO
2
/H
2
O mole ratio
CM ice Tagish Lake ice
 
Fig. 3: Histogram of CO2/H2O ratios of comets and compari-
son with those of the CM and Tagish Lake ice. 
 
References: [1] Alexander C. M. O’D. et al. (2015) 
MAPS, 50, 810-833. [2] Fujiya W. et al. (2015) GCA, 161, 
101-117. [3] Vacher L. G. et al. (2017) GCA, 213, 271-290. 
[4] Hiroi T. et al. (2001) Science, 293, 2234-2236. [5] Grady 
M. M. et al. (2002) MAPS, 37, 713-735. [6] Lindgren P. et 
al. (2017) GCA, 204, 240-251. [7] Fujiya W. et al. (2016) 
LPS XLVII, Abstract #1712. [8] Cody G. D. and Alexander 
C. M. O’D. (2005) GCA, 69, 1085-1097. [9] Hashizume K. 
et al. (2011) Nat. Geosci., 4, 165-168. [10] Mumma M. J. 
and Charnley S. B. (2011) Annu. Rev. Astron. Astrophys., 49, 
471-524. [11] Hässig, M (2017). Astron. Astrophys., 605, 
A50. [12] Alexander C. M. O’D. et al. (2007) GCA, 71, 
4380-4403. [13] Herd C. D. K. et al. (2011) Science, 332, 
1304-1307. [14] Yuen G. et al. (1984) Nature, 307, 252-254. 
[15] Alexander C. M. O’D. et al. (2012) Science, 337, 721-
723. [16] Ootsubo T. et al. (2012) Astrophys. J., 752, 15. 
1377.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)


Carbon Isotopic Ratios of Carbonate in CM Chondrites and the Tagish Lake Meteorite

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CARBON ISOTOPIC RATIOS OF CARBONATE IN CM CHONDRITES AND THE TAGISH LAKE METEORITE. W. Fujiya1, P. Hoppe2, K. Fukuda3, P. Lindgren4, M. R. Lee5, M. Koike6, K. Shirai6, and Y. Sano6. 1Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan (wataru.fujiya.sci@vc.ibaraki.ac.jp), 2Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany, 3The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, 4Lund University, Sölvegatan 12, 223 62 Lund, Sweden, 5University of Glas-gow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, Scotland, 6Atmosphere and Ocean Research Insti-tute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.   Introduction: Carbonate minerals are ubiquitous in CM chondrites and formed by aqueous alteration in the parent body. Previous studies have shown that C iso-topic ratios of CM carbonates are highly variable at whole-rock scales as well as among individual grains in single meteorites [e.g., 1-3]. Despite extensive studies on C isotopic ratios of CM carbonates, the reasons for the variability in 13C values and the origin of the car-bon in carbonates remain poorly understood. The Tagish Lake meteorite is an ungrouped carbo-naceous chondrite that is believed to be derived from a D-type asteroid [4]. The C isotopic ratios of carbonates in Tagish Lake were measured for whole-rock samples [5], but as yet there are no measurements on individual grains. Therefore, the variation in C isotopic ratios has not been investigated for the Tagish Lake carbonates. Here we report C isotopic ratios of individual cal-cite (CaCO3) grains in the LaPaz Icefield (LAP) 031166 CM chondrite (CM 2.1), and of both calcite and dolomite (CaMg(CO3)2) grains in the Tagish Lake meteorite. We discuss the origin of the carbon in car-bonates and explore a possible link between ice in CMs and Tagish Lake and cometary ice. Experimental: Carbon-isotope analysis on the cal-cite grains in LAP 031166, whose O isotopic ratios were previously reported by Lindgren et al. [6], was performed with the NanoSIMS 50 at the Atmosphere and Ocean Research Institute, The University of To-kyo. Negative secondary ions of 12C, 13C, 18O, 12C14N, and 28Si, produced by rastering a Cs+ primary ion beam (20-30 pA, ~1 m in diameter) over 6 x 6 m2 sized areas, were detected simultaneously with five electron multipliers. Carbon-isotope analyses on calcite and dolomite grains in Tagish Lake were performed with the Na-noSIMS 50 at the Max Planck Institute for Chemistry, Mainz. Compared with CM carbonates, carbonate grains in Tagish Like are small (typically <10 m). Thus, we measured C isotopic ratios by recording ion images of 12C-, 13C-, 18O-, 12C14N-, and 28Si- (3 x 3 m2) produced with a Cs+ primary ion beam (~10 pA, ~a few 100’s nm in diameter). Results and Discussion: The 13CPDB and 18OSMOW values of the calcite grains in LAP 031166 are plotted in Fig. 1, together with literature data of Ca-carbonate in CM chondrites [2,3,7]. Figure 2 shows the13C values of the calcite and dolomite grains in Tagish Lake. Also shown in Fig. 2 are data obtained by acid dissolution of whole-rock samples [5]. 02040608010015 20 25 30 35 40 45Paris (Vacher et al., 2017)Nogoya (Fujiya et al., 2016)Murchison (Fujiya et al., 2015)LAP 031166 (This study)13C (permil)18O (permil) Fig. 1: 13C and 18O values of Ca-carbonate grains in CM chondrites.  02040608010013C (permil)Calcite(This study)Dolomite(This study)Bulk calciteGrady et al. (2002)Bulk dolomiteGrady et al. (2002)Fig. 2: 13C values of carbonate grains in Tagish Lake.  1377.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)An apparent contrast between carbonates in CMs and Tagish Lake can be seen: the 13C values of CM carbonates are highly variable, ranging from ~20 to 80‰, whereas all Tagish Lake carbonates have high 13C values of ~70‰, which are consistent with whole-rock analyses [5]. The 18O values of CM carbonates range from ~15 to 40‰, and show no systematic corre-lation with corresponding 13C values (Fig. 1). To explain these observations, we propose here mixing of at least two C reservoirs with different 13C values. The candidates of C reservoirs which may have contributed to the carbonate C include CO2 and CO accreted as ice, and organic matter. CO2 is the major C-bearing species in cometary ice [10]. If C from organic matter contributed to the car-bonate C, organic matter must have been oxidized to CO2 which requires strong oxidants such as peroxide [1,8]. The upper limit on the amounts of CO2 produced by oxidation of organic matter with peroxide is esti-mated to be ~0.1 wt% [1], which is far smaller than the carbonate C abundance of Tagish Lake (~1.3 wt% [5]). Furthermore, no organic components with high 13C values of >80‰ have been identified, except for anom-alous organic grains found in insoluble organic matter (IOM) from a CR chondrite [9]. Thus, the C reservoir with a high 13C value is almost certainly CO2 accreted as ice, which likely had a 13C value of >80‰. Interest-ingly, the 13C value of CO2 in the coma of comet 67P/Churyumov-Gerasimenko measured by Rosetta (64 ± 45‰ [11]) is consistent with the conclusion above. On the other hand, the C reservoir(s) with a low 13C value is poorly constrained: both organic matter and CO are possible. The 13C values of IOM in CMs and Tagish lake are from -17 to -19‰ and from -13 to -15‰, respectively [12,13]. The 13C value of trapped CO in Murchison is approximately -32‰ [14].  Here we assume that the 13C value of CO2 ice is 80‰. Also, we assume that other C reservoirs (i.e., organic matter or CO) with low 13C values from -10 to -30‰ contributed to the carbonate C. The fact that Tagish Lake carbonates have homogenous and high 13C values indicates larger contribution from CO2 ice to the Tagish Lake carbonates than the CM carbonates. The abundance of the carbonate C in Tagish Lake is ~1.3 wt% and the 13C value of the Tagish Lake car-bonates is ~70‰ as determined for whole-rock samples [5]. Thus, from mass balance calculation, CO2 ice ac-counts for 89-91% of the carbonate C in Tagish Lake. Likewise, the average abundance of the carbonate C in CMs is ~0.17 wt% and the average 13C value of CM carbonates is ~45‰ [1]. For the case of CMs, CO2 ice accounts for 61-68% of the carbonate C. Based on the values above and water contents esti-mated by subtracting H in organic matter from the bulk H contents [12,13,15], we can calculate CO2/H2O mole ratios of ice accreted to the CM and Tagish Lake par-ent bodies to be ~0.018 and ~0.28, respectively. The CO2/H2O mole ratios of CM and Tagish Lake ice are compared with those of cometary ice in Fig. 3 (comet data from [16]). The CO2/H2O ratio of the CM ice is smaller than in any comet while the Tagish Lake ice has a CO2/H2O ratio within the range of comets (close to the upper limit). These observations may suggest a genetic link between D-type asteroids and comets. On the other hand, the CM parent body may have accreted closer to the Sun (and therefore, at higher temperature) than D-type asteroids and comets where CO2 ice par-tially sublimated. 01234560 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Jupiter-family cometsOort cloud cometsFrequencyCO2/H2O mole ratioCM ice Tagish Lake ice Fig. 3: Histogram of CO2/H2O ratios of comets and compari-son with those of the CM and Tagish Lake ice.  References: [1] Alexander C. M. O’D. et al. (2015) MAPS, 50, 810-833. [2] Fujiya W. et al. (2015) GCA, 161, 101-117. [3] Vacher L. G. et al. (2017) GCA, 213, 271-290. [4] Hiroi T. et al. (2001) Science, 293, 2234-2236. [5] Grady M. M. et al. (2002) MAPS, 37, 713-735. [6] Lindgren P. et al. (2017) GCA, 204, 240-251. [7] Fujiya W. et al. (2016) LPS XLVII, Abstract #1712. [8] Cody G. D. and Alexander C. M. O’D. (2005) GCA, 69, 1085-1097. [9] Hashizume K. et al. (2011) Nat. Geosci., 4, 165-168. [10] Mumma M. J. and Charnley S. B. (2011) Annu. Rev. Astron. Astrophys., 49, 471-524. [11] Hässig, M (2017). Astron. Astrophys., 605, A50. [12] Alexander C. M. O’D. et al. (2007) GCA, 71, 4380-4403. [13] Herd C. D. K. et al. (2011) Science, 332, 1304-1307. [14] Yuen G. et al. (1984) Nature, 307, 252-254. [15] Alexander C. M. O’D. et al. (2012) Science, 337, 721-723. [16] Ootsubo T. et al. (2012) Astrophys. J., 752, 15. 1377.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)

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Carbon Isotopic Ratios of Carbonate in CM Chondrites and the Tagish Lake Meteorite

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