Lee, M.R.

Lindgren, P.

Sofe, M.R.

English

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Enlighten – Research publications by members of the University of Glasgow http://eprints.gla.ac.uk        Lee, M.R., Sofe, M.R., and Lindgren, P. (2012) Evolution of Carbonate Mineralogy Through the CM2-CM1 Series. In: 75th Annual Meeting of the Meteoritical Society, 12-17 Aug 2012, Cairns, Australia.  http://eprints.gla.ac.uk/69047/   Deposited on: 4th September 2012   EVOLUTION OF CARBONATE MINERALOGY THROUGH THE CM2-CM1 SERIESM. R. Lee1, M. R. Sofe1 and P. Lindgren1. 1School of Geograph-ical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, U.K. E-mail: Martin.Lee@Glasgow.ac.uk. Introduction: Carbonates are a volumetrically minor con-stituent of the CM carbonaceous chondrites, but their chemical and isotopic compositions and microstructures can provide cru-cial information about the environment of parent body aqueous alteration. Most CM2s contain only Ca-carbonates (cal-cite±aragonite) [1] but some of the more highly altered CM2s and the CM1s additionally have Mg- and Fe-rich carbonates (i.e. do-lomite±breunnerite) [2]. This correspondence between the miner-alogy of carbonates and the extent of aqueous alteration of their parent rock has been investigated here in order to ascertain what it may reveal about alteration conditions through the CM series. Methods: Carbonates in thin sections of twelve CMs were located and characterised using a Zeiss Sigma SEM, then quanti-tatively chemically analysed with a Cameca SX100 electron probe. The following meteorites were studied (in order of in-creasing degree of alteration): Murchison, Murray, Pollen, Mighei, EET 96029, LON 94101, Nogoya, Cold Bokkeveld, QUE 93005, LAP 031166, SCO 06043 and ALH 84045. Results: Those CM2s that have been less altered overall con-tain aragonite and one or two generations of calcite. In Murchi-son the aragonite crystallized first and was overgrown by calcite. Different generations of calcite can be distinguished petrographically, and the later generation may fill fractures [3] or replace olivine or pyroxene. Calcite in many of the CM2s has itself been replaced by Mg-serpentine [4], and this reaction has almost gone to completion in LAP 031166 (CM2-1). In Pollen the replacement took place between crystallization of the two calcite generations. QUE 93005 is a highly altered CM2 and con-tains the widest range of carbonate minerals yet recorded, namely breunnerite, Ca-poor and Ca-rich dolomite, and calcite, and both the dolomite and calcite can form veins. Carbonate mineralogy and abundance differ within the CM1s [2], but several of them contain veins of dolomite, which in SCO 06043 cross-cut the compacted meteorite matrix [5]. Dolomite in both QUE 93005 and SCO 06043 has been partially replaced by calcite [5]. Discussion: Almost all of the CM2s contain multiple genera-tions of carbonates, and recent work has shown that successive phases of calcite in the CM2s also have distinct O isotope com-positions [6]. The earlier carbonates have formed by cementation of primary pore spaces whereas later generations typically fill fractures or have replaced earlier carbonates or olivine/pyroxene. Taken together, this evidence indicates that most of the sampled parent body regions experienced multiple phases of carbonate mineralization, with intervening compaction and/or phyllosilicate crystallization. The challenge is to reconcile this evidence for a dynamic aqueous system with models for static solutions.  Acknowledgements: We thank NASA-JSC and the Natural History Museum (London) for loan of samples used in this study. References: [1] Lee M. R. and Ellen R. 2008. Meteoritics & Planetary Science 43:1219–1231. [2] Zolensky M. E. et al. 1997. Geochimica et Cosmochimica Acta 61: 5099–5115. [3] Lindgren P. et al. 2011. Earth & Planetary Science Letters 306:289–298.[4] Sofe M. R. et al. 2010. Meteoritics & Planetary Science 45:A193. [5] Lindgren P. et al. (2012). Abstract #1949. 43rd Lu-nar & Planetary Science Conference. [6] Tyra M. A. et al. 2012. Geochimica et Cosmochimica Acta 77:383–395.5246.pdf75th Annual Meteoritical Society Meeting (2012)

Evolution of Carbonate Mineralogy Through the CM2-CM1 Series

Enlighten: Publications

Enlighten – Research publications by members of the University of Glasgow 
http://eprints.gla.ac.uk 
 
 
 
 
 
 
 
Lee, M.R., Sofe, M.R., and Lindgren, P. (2012) Evolution of Carbonate 
Mineralogy Through the CM2-CM1 Series. In: 75th Annual Meeting of 
the Meteoritical Society, 12-17 Aug 2012, Cairns, Australia. 
 
http://eprints.gla.ac.uk/69047/ 
 
 
Deposited on: 4th September 2012 
 
 
EVOLUTION OF CARBONATE MINERALOGY 
THROUGH THE CM2-CM1 SERIES
M. R. Lee1, M. R. Sofe1 and P. Lindgren1. 1School of Geograph-
ical and Earth Sciences, University of Glasgow, Glasgow G12 
8QQ, U.K. E-mail: Martin.Lee@Glasgow.ac.uk. 
Introduction: Carbonates are a volumetrically minor con-
stituent of the CM carbonaceous chondrites, but their chemical 
and isotopic compositions and microstructures can provide cru-
cial information about the environment of parent body aqueous 
alteration. Most CM2s contain only Ca-carbonates (cal-
cite±aragonite) [1] but some of the more highly altered CM2s and 
the CM1s additionally have Mg- and Fe-rich carbonates (i.e. do-
lomite±breunnerite) [2]. This correspondence between the miner-
alogy of carbonates and the extent of aqueous alteration of their 
parent rock has been investigated here in order to ascertain what 
it may reveal about alteration conditions through the CM series. 
Methods: Carbonates in thin sections of twelve CMs were 
located and characterised using a Zeiss Sigma SEM, then quanti-
tatively chemically analysed with a Cameca SX100 electron 
probe. The following meteorites were studied (in order of in-
creasing degree of alteration): Murchison, Murray, Pollen, 
Mighei, EET 96029, LON 94101, Nogoya, Cold Bokkeveld, 
QUE 93005, LAP 031166, SCO 06043 and ALH 84045. 
Results: Those CM2s that have been less altered overall con-
tain aragonite and one or two generations of calcite. In Murchi-
son the aragonite crystallized first and was overgrown by calcite. 
Different generations of calcite can be distinguished 
petrographically, and the later generation may fill fractures [3] or 
replace olivine or pyroxene. Calcite in many of the CM2s has 
itself been replaced by Mg-serpentine [4], and this reaction has 
almost gone to completion in LAP 031166 (CM2-1). In Pollen 
the replacement took place between crystallization of the two 
calcite generations. QUE 93005 is a highly altered CM2 and con-
tains the widest range of carbonate minerals yet recorded, namely 
breunnerite, Ca-poor and Ca-rich dolomite, and calcite, and both 
the dolomite and calcite can form veins. Carbonate mineralogy 
and abundance differ within the CM1s [2], but several of them 
contain veins of dolomite, which in SCO 06043 cross-cut the 
compacted meteorite matrix [5]. Dolomite in both QUE 93005 
and SCO 06043 has been partially replaced by calcite [5]. 
Discussion: Almost all of the CM2s contain multiple genera-
tions of carbonates, and recent work has shown that successive 
phases of calcite in the CM2s also have distinct O isotope com-
positions [6]. The earlier carbonates have formed by cementation 
of primary pore spaces whereas later generations typically fill 
fractures or have replaced earlier carbonates or olivine/pyroxene. 
Taken together, this evidence indicates that most of the sampled 
parent body regions experienced multiple phases of carbonate 
mineralization, with intervening compaction and/or phyllosilicate 
crystallization. The challenge is to reconcile this evidence for a 
dynamic aqueous system with models for static solutions.  
Acknowledgements: We thank NASA-JSC and the Natural 
History Museum (London) for loan of samples used in this study. 
References: [1] Lee M. R. and Ellen R. 2008. Meteoritics & 
Planetary Science 43:1219–1231. [2] Zolensky M. E. et al. 1997. 
Geochimica et Cosmochimica Acta 61: 5099–5115. [3] Lindgren 
P. et al. 2011. Earth & Planetary Science Letters 306:289–298.
[4] Sofe M. R. et al. 2010. Meteoritics & Planetary Science 
45:A193. [5] Lindgren P. et al. (2012). Abstract #1949. 43rd Lu-
nar & Planetary Science Conference. [6] Tyra M. A. et al. 2012. 
Geochimica et Cosmochimica Acta 77:383–395.
5246.pdf75th Annual Meteoritical Society Meeting (2012)


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Evolution of Carbonate Mineralogy Through the CM2-CM1 Series

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