Quantitative understanding of solar wind (SW) elemental fractionation is required to improve knowledge of the solar nebula abundances from Genesis samples, in particular abundances of volatile elements, depleted in CI chondrites. Ratios of elements with low and high first ionization potential (FIP) in the solar wind, e.g., Fe/He, are higher than photospheric abundances. C, O, and N have intermediate FIP and are thus critical as to whether this fractionation is stepwise or gradual as a function of FIP

Chen, J. H.

Dauphas, N.

Eiler, J. M.

Guan, Y.

Ma, C.

Papanastassiou, D. A.

Remusat, L.

Roskosz, M.

Stodolna, J.

Acid leachates and residues of primitive meteorites have revealed

large variations in ^(54)Cr relative to terrestrial composition [1–9]. Despite two decades of extensive search, the nature of the carrier of ^(54)Cr excesses is still uncertain. Ion probes offer the opportunity to address directly this question by measuring ^(54)Cr/^(52)Cr ratios in individual grains [10–13]

Caltech Authors - Main

5110
SUPERNOVA NANOPARTICLES ARE THE CARRIERS OF 54Cr
ANOMALIES IN PLANETARY MATERIALS
N. Dauphas1,2, L. Remusat2,3, J. H. Chen4, M. Roskosz5, D. A.
Papanastassiou4,2, J. Stodolna5, Y. Guan2, C. Ma2 and J. M.
Eiler2. 1Origins Laboratory, Department of the Geophysical Sciences
and Enrico Fermi Institute, The University of Chicago. E-mail:
dauphas@uchicago.edu. 2Division of Geological and Planetary Sciences,
Caltech. 3Laboratoire de Mine´ralogie et Cosmochimie du Muse´um,
Muse´um National d’Histoire Naturelle 4Jet Propulsion Laboratory.
5Unite´ Materiaux et Transformations, Universite´ de Lille 1, France.
Acid leachates and residues of primitive meteorites have revealed
large variations in 54Cr relative to terrestrial composition [1–9]. Despite
two decades of extensive search, the nature of the carrier of 54Cr excesses
is still uncertain. Ion probes oﬀer the opportunity to address directly this
question by measuring 54Cr/52Cr ratios in individual grains [10–13].
We have measured the Cr isotopic composition of physical and
chemical separates from the primitive carbonaceous chondrites Orgueil
and Murchison. The colloidal fraction of Orgueil (median grain size of
approx. 30 nm) shows the largest 54Cr-excess ever measured in a bulk
meteorite residue (e54Cr = 170). This indicates that the carrier of 54Cr-
anomalies was eﬃciently concentrated by our procedure and that it must
be very ﬁne grained (<100 nm) [also see 3, 4]. In situ Cr isotopic analyses
by NanoSIMS of the <200 nm nominal size fraction of Orgueil (median
grain size 184 nm) revealed the presence of 54Cr-rich nanoparticles
(54Cr/52Cr > 3.6 · solar). Heterogeneous distribution of these
nanoparticles in the inner solar system is compatible with the variations
in 54Cr abundance measured in bulk meteorites and terrestrial planets.
Because of their small size, no direct mineralogical characterization of the
54Cr-rich grains could be performed. However, study by transmission
electron microscopy shows that 54Cr-rich grains are found in a fraction
where the sole chromium-bearing grains are oxides, mostly nanospinels.
At the present time, we cannot tell which of type Ia and II
supernovae produced the grains identiﬁed here, though the oxide
mineralogy would favor condensation from a type II. This question can
be addressed in the future by measuring the isotopic abundance of other
neutron-rich isotopes, in particular 48Ca [14, 15], in the same grains.
Study of these grains will shed new light on the nucleosynthesis of iron-
group nuclei and the evolution of supernovae.
References: [1] Rotaru M. et al. 1992. Nature 358:465–470. [2]
Podosek F. et al. 1997. Meteoritics & Planet. Sci. 32:617–627. [3] Nichols
Jr. R. H. et al. 1998. (Abstract #1748) 29th Lunar and Planetary Science
Conference. [4] Nichols Jr. R. H. et al. 2000. MAPS 35:A119. [5]
Alexander C. M. O’D. 2002. (Abstract #1872). 33rd Lunar and Planetary
Science Conference. [6] Shukolyukov A. and Lugmair G. W. 2006. EPSL
250:200–213. [7] Trinquier A. 2007. ApJ 655:1179–1185. [8] Birck J.-L.
et al. 2009. (Abstract #1683) 40th Lunar and Planetary Science
Conference. [9] Qin L. et al. 2010. GCA 74:1122–1145. [10] Ott U. et al.
1997. (Abstract #1278). 28th Lunar and Planetary Science Conference.
[11] Qin L. et al. 2009. Meteoritics & Planet. Sci. 44:A71. [12] Nittler L.R.
et al. 2010. (Abstract #2071). 41st Lunar and Planetary Science
Conference. [13] Dauphas N. et al. 2010. (Abstract #1073). 41st Lunar
and Planetary Science Conference. [14] Meyer B.S. et al. 1996. (Abstract
#875). 27th Lunar and Planetary Science Conference. [15] Woosley S.E.
1997. ApJ 476:801.
5130
A CONSTANT IDP FLUX BASED ON IRIDIUM ANALYSES OF
ARCHEAN SEDIMENTS
A. K. Davatzes1, D. R. Lowe2 and F. T. Kyte3. 1Department of Earth
and Environmental Science, Temple University, Philadelphia, PA 19122
E-mail: alix@temple.edu. 2Stanford University, Stanford, CA. 3IGPP,
UCLA, Los Angeles, CA, USA.
Introduction: In modern sediments, iridium (Ir) concentrations are
inversely correlated to sedimentation rate because of the near constant
ﬂux of Ir-bearing interplanetary dust particles (IDPs) to the Earth’s
surface [1, 2]. In order to calculate the sedimentation rate in ancient rocks
using Ir, the IDP ﬂux must be known. Previous studies [3] have reported
low Ir levels in late Hadean/early Archean metasedimentary and
metavolcanic rocks from Akilia, Greenland. They suggest that IDP mass
accretion rates do not scale to the rate of supply, and that increasing
abundance results in increasing collisional loss. Schmitz et al. [4] showed
that Ordovician-age sedimentary rocks record higher meteorite ﬂux than
modern sediments, but that the IDP ﬂux, based on 3He measurements,
was comparable to that of today [5] unless there was signiﬁcant loss of
3He due to alteration. In this study, we systematically analyzed a section
of 3.24 Ga core from the base of the Fig Tree Group in the Barberton
greenstone belt (BGB) in South Africa for Ir. The lithology is ﬁne
carbonaceous chert and black and white banded chert. There is little
coarse debris and the sediments lack evidence of current transport and
deposition. These characteristics indicate that this is a condensed section
formed at very low sedimentation rates.
Methods: A 4.8 m core was logged for lithology, sedimentary
structures, and post-depositional features. It was sliced into 5 cm-long
segments, from which a portion spanning the full length was powdered
and thin sections were made. Ir was measured in each sample by RNAA
and major and trace elements by XRF.
Results and Discussion: Ir concentrations in the 96 samples range
from 2 to 663 pg g)1, comparable to the range of concentrations found in
modern sediments, suggesting that IDP ﬂux in the Archean must have
may not been signiﬁcantly diﬀerent than the Phanerozoic mass ﬂux. More
than 85% of the Ir concentrations are less than 200 pg g)1, and likely
reﬂect IDP accumulation rates, but several samples had Ir >200 pg g)1,
including two spikes >600 pg g)1. These could represent extraterrestrial
‘‘events’’ such as impacts or increases in IDP ﬂux. Sedimentation rates in
various rocks throughout the BGB have been estimated to range from 10
to 1000 m Myr)1, consistent with estimates in this study (averaging 80 m
Myr)1) if IDP ﬂux is the same as modern rates. Rates higher than this are
unlikely as they would have resulted in suppression of microbial mat
formation and extraordinarily thick rock successions even assuming large
breaks in time. Such high rates of sedimentation are also unlikely given
that the sediments were deposited in a quiescent marine setting. Very high
levels of Ir in the underlying S3 impact layer and lower background levels
seen here suggest that though large impacts would have introduced
signiﬁcant amounts of Ir to the Earth’s surface, the ﬂux from dust is
unchanged compared to today.
References: [1] Barker and Anders 1968. Geochimica et
Cosmochimica Acta 32:627–645. [2] Bruns P. et al. 1996. J. of Sed. Res.
66:608–612. [3] Anbar et al. 2001. J. of Geophysical Res. 106:3219–3236.
[4] Schmitz B. et al. 1996. Earth and Planetary Science Letters 145:31–48.
[5] Patterson et al. 1998. Earth and Planetary Science Letters 163:315–325.
A42 73rd Meeting of the Meteoritical Society: Abstracts


Supernova Nanoparticles are the Carriers of ^(54)Cr Anomalies in Planetary Materials

5110
SUPERNOVA NANOPARTICLES ARE THE CARRIERS OF 54Cr
ANOMALIES IN PLANETARY MATERIALS
N. Dauphas1,2, L. Remusat2,3, J. H. Chen4, M. Roskosz5, D. A.
Papanastassiou4,2, J. Stodolna5, Y. Guan2, C. Ma2 and J. M.
Eiler2. 1Origins Laboratory, Department of the Geophysical Sciences
and Enrico Fermi Institute, The University of Chicago. E-mail:
dauphas@uchicago.edu. 2Division of Geological and Planetary Sciences,
Caltech. 3Laboratoire de Minéralogie et Cosmochimie du Muséum,
Muséum National d’Histoire Naturelle 4Jet Propulsion Laboratory.
5Unité Materiaux et Transformations, Université de Lille 1, France.
Acid leachates and residues of primitive meteorites have revealed
large variations in 54Cr relative to terrestrial composition [1–9]. Despite
two decades of extensive search, the nature of the carrier of 54Cr excesses
is still uncertain. Ion probes offer the opportunity to address directly this
question by measuring 54Cr/52Cr ratios in individual grains [10–13].
We have measured the Cr isotopic composition of physical and
chemical separates from the primitive carbonaceous chondrites Orgueil
and Murchison. The colloidal fraction of Orgueil (median grain size of
approx. 30 nm) shows the largest 54Cr-excess ever measured in a bulk
meteorite residue (e54Cr = 170). This indicates that the carrier of 54Cr-
anomalies was efficiently concentrated by our procedure and that it must
be very fine grained (<100 nm) [also see 3, 4]. In situ Cr isotopic analyses
by NanoSIMS of the <200 nm nominal size fraction of Orgueil (median
grain size 184 nm) revealed the presence of 54Cr-rich nanoparticles
(54Cr/52Cr > 3.6 · solar). Heterogeneous distribution of these
nanoparticles in the inner solar system is compatible with the variations
in 54Cr abundance measured in bulk meteorites and terrestrial planets.
Because of their small size, no direct mineralogical characterization of the
54Cr-rich grains could be performed. However, study by transmission
electron microscopy shows that 54Cr-rich grains are found in a fraction
where the sole chromium-bearing grains are oxides, mostly nanospinels.
At the present time, we cannot tell which of type Ia and II
supernovae produced the grains identified here, though the oxide
mineralogy would favor condensation from a type II. This question can
be addressed in the future by measuring the isotopic abundance of other
neutron-rich isotopes, in particular 48Ca [14, 15], in the same grains.
Study of these grains will shed new light on the nucleosynthesis of iron-
group nuclei and the evolution of supernovae.
References: [1] Rotaru M. et al. 1992. Nature 358:465–470. [2]
Podosek F. et al. 1997. Meteoritics & Planet. Sci. 32:617–627. [3] Nichols
Jr. R. H. et al. 1998. (Abstract #1748) 29th Lunar and Planetary Science
Conference. [4] Nichols Jr. R. H. et al. 2000. MAPS 35:A119. [5]
Alexander C. M. O’D. 2002. (Abstract #1872). 33rd Lunar and Planetary
Science Conference. [6] Shukolyukov A. and Lugmair G. W. 2006. EPSL
250:200–213. [7] Trinquier A. 2007. ApJ 655:1179–1185. [8] Birck J.-L.
et al. 2009. (Abstract #1683) 40th Lunar and Planetary Science
Conference. [9] Qin L. et al. 2010. GCA 74:1122–1145. [10] Ott U. et al.
1997. (Abstract #1278). 28th Lunar and Planetary Science Conference.
[11] Qin L. et al. 2009. Meteoritics & Planet. Sci. 44:A71. [12] Nittler L.R.
et al. 2010. (Abstract #2071). 41st Lunar and Planetary Science
Conference. [13] Dauphas N. et al. 2010. (Abstract #1073). 41st Lunar
and Planetary Science Conference. [14] Meyer B.S. et al. 1996. (Abstract
#875). 27th Lunar and Planetary Science Conference. [15] Woosley S.E.
1997. ApJ 476:801.
5130
A CONSTANT IDP FLUX BASED ON IRIDIUM ANALYSES OF
ARCHEAN SEDIMENTS
A. K. Davatzes1, D. R. Lowe2 and F. T. Kyte3. 1Department of Earth
and Environmental Science, Temple University, Philadelphia, PA 19122
E-mail: alix@temple.edu. 2Stanford University, Stanford, CA. 3IGPP,
UCLA, Los Angeles, CA, USA.
Introduction: In modern sediments, iridium (Ir) concentrations are
inversely correlated to sedimentation rate because of the near constant
flux of Ir-bearing interplanetary dust particles (IDPs) to the Earth’s
surface [1, 2]. In order to calculate the sedimentation rate in ancient rocks
using Ir, the IDP flux must be known. Previous studies [3] have reported
low Ir levels in late Hadean/early Archean metasedimentary and
metavolcanic rocks from Akilia, Greenland. They suggest that IDP mass
accretion rates do not scale to the rate of supply, and that increasing
abundance results in increasing collisional loss. Schmitz et al. [4] showed
that Ordovician-age sedimentary rocks record higher meteorite flux than
modern sediments, but that the IDP flux, based on 3He measurements,
was comparable to that of today [5] unless there was significant loss of
3He due to alteration. In this study, we systematically analyzed a section
of 3.24 Ga core from the base of the Fig Tree Group in the Barberton
greenstone belt (BGB) in South Africa for Ir. The lithology is fine
carbonaceous chert and black and white banded chert. There is little
coarse debris and the sediments lack evidence of current transport and
deposition. These characteristics indicate that this is a condensed section
formed at very low sedimentation rates.
Methods: A 4.8 m core was logged for lithology, sedimentary
structures, and post-depositional features. It was sliced into 5 cm-long
segments, from which a portion spanning the full length was powdered
and thin sections were made. Ir was measured in each sample by RNAA
and major and trace elements by XRF.
Results and Discussion: Ir concentrations in the 96 samples range
from 2 to 663 pg g)1, comparable to the range of concentrations found in
modern sediments, suggesting that IDP flux in the Archean must have
may not been significantly different than the Phanerozoic mass flux. More
than 85% of the Ir concentrations are less than 200 pg g)1, and likely
reflect IDP accumulation rates, but several samples had Ir >200 pg g)1,
including two spikes >600 pg g)1. These could represent extraterrestrial
‘‘events’’ such as impacts or increases in IDP flux. Sedimentation rates in
various rocks throughout the BGB have been estimated to range from 10
to 1000 m Myr)1, consistent with estimates in this study (averaging 80 m
Myr)1) if IDP flux is the same as modern rates. Rates higher than this are
unlikely as they would have resulted in suppression of microbial mat
formation and extraordinarily thick rock successions even assuming large
breaks in time. Such high rates of sedimentation are also unlikely given
that the sediments were deposited in a quiescent marine setting. Very high
levels of Ir in the underlying S3 impact layer and lower background levels
seen here suggest that though large impacts would have introduced
significant amounts of Ir to the Earth’s surface, the flux from dust is
unchanged compared to today.
References: [1] Barker and Anders 1968. Geochimica et
Cosmochimica Acta 32:627–645. [2] Bruns P. et al. 1996. J. of Sed. Res.
66:608–612. [3] Anbar et al. 2001. J. of Geophysical Res. 106:3219–3236.
[4] Schmitz B. et al. 1996. Earth and Planetary Science Letters 145:31–48.
[5] Patterson et al. 1998. Earth and Planetary Science Letters 163:315–325.
A42 73rd Meeting of the Meteoritical Society: Abstracts


English

A unique dmitryivanovite (CaAl_2O_4) -dominant Ca-,

Al-rich refractory inclusion (CAI), named “Cracked Egg” by [1], was

observed in the NWA 1934 CV3 carbonaceous chondrite. During our

nano-mineralogy investigation of this CAI, Cl-bearing mayenite,

Ca_(12)Al_(14)O_(32)Cl_2, was identified. Electron-microprobe, SEM, electron backscatter

diffraction (EBSD), and micro-Raman analyses have been used to

characterize its composition and structure. Pyrometamorphic and natural

Cl-bearing mayenites have been reported [2, 3] and synthetic

Ca_(12)Al_(14)O_(32)Cl_2 is well known [4]. Here, we report the first occurrence of

Ca_(12)Al_(14)O_(32)Cl_2 in a meteorite as a new alteration mineral in a CAI

Ma, Chi

Sweeney Smith, Stuart A.

Connolly, Harold C., Jr.

Beckett, John R.

Rossman, George R.

Schrader, Devin L.

5424
N2 SELF-SHIELDING IN THE SOLAR NEBULA: AN UPDATE
J. R. Lyons. Institute of Geophysics and Planetary Physics, UCLA, Los
Angeles, CA 90095-1567. E-mail: jimlyons@ucla.edu.
Introduction: The N2 molecule is isoelectronic to CO, and exhibits a
similar band system to CO in the VUV. The resolved rovibronic structure
and very strong bands make N2 a plausible candidate for self-shielding,
even though it is an order of magnitude less abundant than CO in a gas
of solar composition. The discovery of very large 15N enrichment in lithic
clasts in carbonaceous chondrites (e.g., [1–5]), in micrometeorites [6], and
in comets [7] could be due to either low temperature ion-molecule
chemistry that leads to NH3 formation [8] or to N2 self-shielding.
Nitrogen isotopes in the solar system may also be enriched in 15N as a
result of N2 self-shielding [9].
Previous Modeling: A preliminary assessment of N2 self-shielding in
the outer nebula [10, 11] suggests that although self-shielding does occur,
it produces substantial 15N enrichment in only a very small fraction of
nebular material at 30 AU (d15N is about +800& in <1 ppm of total N,
[11]). Also, the total enrichment in self-shielding product nitrogen (as
HCN) is about +100& over 106 yr at 30 AU. This enrichment may not
be large enough to distinguish Jupiter, with d15N = )380 ± 80& [12],
from the Sun, which has solar wind with d15N is about -450 ± 100&
[13].
Modeling in Progress: The preliminary model ([10, 11]) used a
reduced set of nitrogen reactions, and used an N2 shielding function
inferred from a Titan atmosphere photochemical model [14], with mean
N2 cross section representative of the 91–100 nm range applicable to the
solar nebula. Present modeling includes (1) a more complete set of
nitrogen reactions, and (2) a full integration over 911–100 nm of N2
dissociation in the presence of H2 absorption. The
28N2 and
29N2 cross
sections are from a coupled-channel model description of measured N2
cross sections, and were provided by A. Haeys and B. Lewis at ANU.
These calculations are in progress.
Implications: As I pointed at the 2010 LPSC, the preliminary model
results on nebular N2 self-shielding have implications for CO self-
shielding in the outer solar system. One criticism of outer solar nebula
CO self-shielding has been that Jupiter would become more enriched in
15N due to N2 self-shielding than is observed [12]. However, with present
uncertainties, a 100& increase in outer nebular d15N is not enough to
rule out the occurrence of N2 (and CO) self-shielding. Reduced
uncertainties on solar wind d15N, as well as a quantitative assessment of
fractionation during solar wind acceleration, could inﬂuence this
conclusion.
References: [1] Sugiura et al. 2000. Meteoritics & Planetary Science
35:987–996. [2] Ivanova et al. 2008. Meteoritics & Planetary Science
43:915–940. [3] Briani et al. 2009. (Abstract #1642). 40th Lunar and
Planetary Science Conference. [4] Bonal L. et al. 2009. (Abstract #2046).
40th Lunar and Planetary Science Conference. [5] Ishii et al. 2009.
(Abstract #2467). 40th Lunar and Planetary Science Conference [6] Floss
C. et al. 2009. (Abstract #1082). 40th Lunar and Planetary Science
Conference. [7] Bockelee-Morvan D. et al. 2008. The Astrophysical
Journal Lett. 679:L49–L52. [8] Rodgers S. D. and Charnley S. B. 2008.
MNRAS 385:48. [9] Clayton R. N. 2002. Nature 415:860–861. [10] Lyons
et al. 2009. Geochimica et Cosmochimica Acta 73, 4998–5017. [11] Lyons
J. 2009. Abstract #5437. 72nd Metereological Society Meeting. [12] Owen
T. 2001. The Astrophysical Journal 553:L77–L79. [13] Kallio A. et al.
2010. (Abstract #2481). 41st Lunar and Planetary Science Conference.
[14] Liang et al. 2007. The Astrophysical Journal 664:L115–L118.
5134
DISCOVERY OF Cl-BEARING MAYENITE, Ca12Al14 O32Cl2, A NEW
MINERAL IN A CV3 METEORITE
Chi Ma1*, Stuart A. Sweeney Smith2, Harold C. Connolly Jr3,4,5, John R.
Beckett1, George R. Rossman1 and Devin L. Schrader5. 1Division of
Geological and Planetary Sciences, California Institute of Technology,
Pasadena, CA 91125. 2Department of Geology, Carleton College,
Northﬁeld, MN 55057. 3Department of Physical Sciences, Kingsborough
Community College of CUNY, Brooklyn, NY 11235 and Earth and
Environmental Sciences, The Graduate Center of CUNY, New York, NY
10024. 4Department of Earth and Planetary Sciences, AMNH, New York,
NY 10024. 5Lunar and Planetary Laboratory, University of Arizona,
Tucson, AZ 85721. E-mail: chi@gps.caltech.edu.
Introduction: A unique dmitryivanovite (CaAl2O4) -dominant Ca-,
Al-rich refractory inclusion (CAI), named ‘‘Cracked Egg’’ by [1], was
observed in the NWA 1934 CV3 carbonaceous chondrite. During our
nano-mineralogy investigation of this CAI, Cl-bearing mayenite,
Ca12Al14O32Cl2, was identiﬁed. Electron-microprobe, SEM, electron back-
scatter diﬀraction (EBSD), and micro-Raman analyses have been used to
characterize its composition and structure. Pyrometamorphic and natural
Cl-bearing mayenites have been reported [2, 3] and synthetic
Ca12Al14O32Cl2 is well known [4]. Here, we report the ﬁrst occurrence of
Ca12Al14O32Cl2 in a meteorite as a new alteration mineral in a CAI.
Occurrence, Chemistry, and Crystallography: Cl-bearing mayenite
occurs as small (80–300 nm) crystals forming ﬁne-grained aggregates (1–
20 lm in size) along with Zn-bearing hercynite, gehlenite and perovskite
in veins and inclusions within the dmitryivanovite-dominant CAI. The
mean chemical composition is (wt%) Al2O3 48.48, CaO 45.73, Cl 5.12,
FeO 0.80, Na2O 0.12, TiO2, 0.03, O -1.16, sum 99.12. An empirical
formula calculated on the basis of 34 O + Cl atoms is
(Ca11.93Na0.06)
P
11.99 (Al13.91Fe0.16Ti0.01)
P
14.08O31.94Cl2.11.
Synthetic Ca12Al14O32Cl2 has a cubic structure with a Ca-Al-O
framework forming ‘‘cages’’ in which the Cl is located [4]. The meteoritic
Cl-bearing mayenite showed no electron back-scatter diﬀraction pattern,
due to small crystal sizes and, probably, poorly ordered structures but
Raman microanalysis revealed a spectrum very close to that of synthetic
Ca12Al14O32Cl2, conﬁrming that the meteoritic phase has a similar
structure.
Origin and Signiﬁcance: Cl-bearing mayenite is not only a new
meteoritic Ca-, Al-phase, but also a new Cl-rich phase, joining the Cl-rich
meteoritic minerals sodalite (Na4Al3Si3O12Cl) and wadalite
(Ca6Al5Si2O16Cl3). Cl-bearing mayenite is a secondary alteration phase in
‘‘Cracked Egg’’. A simple scenario for its formation would be the parent
body breakdown of dmitryivanovite in a Cl-, Fe-rich vapor or ﬂuid to
produce Cl-bearing mayenite and hercynite, although we have not yet
ruled out the possibility that Cl-bearing mayenite formed during
terrestrial alteration or that preterrestrial Cl-free mayenite was later
chlorinated. Multiple-alteration events seem to have occurred in this CAI.
References: [1] Sweeney Smith S.A. et al. 2010. (Abstract #1877).
41th Lunar and Planetary Science Conference. [2] Zateeva S.N. et al.
2007. Geology of Ore Deposits 49:792–780. [3] Galuskin E.V. et al. 2009.
European Journal of Mineralogy 21:1045–1059. [4] Iwata T. et al. 2007.
Journal of Solid State Chemistry 181:51–55.
73rd Meeting of the Meteoritical Society: Abstracts A123


Discovery of Cl-Bearing Mayenite, Ca_(12)Al_(14)O_(32)Cl_2, a new Mineral in a CV3 Meteorite

Heber, V. S.

Jurewicz, A. J. G.

Kallio, A. P.

Olinger, C.

Woolum, D. S.

McKeegan, K. D.

Burnett, D. S.

5181
IN-SITU OBSERVATION OF D-RICH CARBONACEOUS MATTERS
EMBEDDED IN NWA 801 CR2 CHONDRITE
M. Hashiguchi1, S. Kobayashi2 and H. Yurimoto1,2. 1Natural History
Sciences, Hokaido University. E-mail: mhashi@ep.sci.hokudai.ac.jp.
2CRIS, Hokkaido University.
Introduction: Insoluble organic matter (IOM) extracted from
carbonaceous chondrites is considered to have formed in cold molecular
clouds and/or outer solar nebula, because of its enrichment of D and 15N
[e.g., 1]. However, occurrences of IOM in chondrite are poorly
understood. This is because most of the previous studies for meteoritic
organic matters used extracted-IOM. In this study, we observed organic
matters in chondrite by in situ hydrogen isotopic analysis to reveal their
morphologies and occurrences.
Methods: The sample used in this study is a polished thin section of
NWA 801 CR2 chondrite. Hydrogen isotope imaging (isotopography)
was performed by a Hokudai isotope microscope system (Cameca ims
1270 equipped with SCAPS) [2]. We obtained 1H), 2D), and 12C) images
from 65 areas of 50 lm in diameter in the NWA 801 matrix. Hydrogen
isotopic composition of the matrix was normalized to a reported value of
phyllosilicate of Renazzo CR2, which is estimated to be +730& [3].
Morphologies of carbonaceous matters identiﬁed by isotopography were
observed by FE-SEM-EDS (JSM-7000F, Oxford INCA Energy) system.
Results and Discussion: D-rich spots with high C secondary ion
signals were found in isotopography in the 33 areas of 65 areas. Total
numbers of the D-rich carbonaceous spots were 84. dD values of the
carbonaceous spots are ranged over 1700–9600&. These carbonaceous
spots are not distributed randomly in the NWA 801 matrix. We identiﬁed
the morphologies of 48 D-rich carbonaceous spots. The other 36 spots
have been failed to determine the locations by the SEM-EDS because of
too small X-ray intensities of carbon. The 48 D-rich carbonaceous spots
are composed of carbonaceous matters which morphologies are basically
globular. Morphologies of the D-rich carbonaceous globules were
classiﬁed into four groups; round globules, irregular-shaped globules,
globule aggregates and ring globules. Round and irregular-shaped
globules consist of a separated globule embedded in silicate matrix, which
sizes distribute 0.2–1.0 lm. The globule aggregate consists of an aggregate
of carbonaceous globules with silicates. The aggregate sizes are 0.3–
2.6 lm. Ring globules are ring shaped carbonaceous globules with sizes of
0.3–0.8 lm that include silicate or void in their interior. The ring globules
including a void are similar in morphology to organic globules observed
in Tagish Lake meteorite [4]. Numbers of Round globules, Irregular-
shaped globules, Globule aggregates and Ring globules are 6, 9, 26, and 7
respectively.
The carbonaceous matters with H isotope anomaly found in this
study are mainly composed of H and C, and are enriched in D. These
characteristics indicate that these matters correspond to organic matters
formed in molecular clouds and/or outer solar nebula. Formation
processes of these morphorogies can be explained by a formation model
of organic matters in molecular clouds [e.g., 5].
References: [1] Busemann H. et al. 2006. Science, 312:727–730 [2]
Yurimoto H. et al. 2003. Appl. Surf. Sci. 203–204:793–797 [3] Deloule E.
and Robert F. 1995 Geochim. Cosmochim. Acta 59:4695–4706. [4]
Nakamura-Messenger et al. 2006. Science, 314:1439–1442. [5] Greenberg
J. M. 1998 Astron. Astrophys. 330:375–380.
5301
SOLAR WIND ABUNDANCES OF C AND O
V. S. Heber1, Y. Guan2, A. J. G. Jurewicz3, A. P. Kallio1, C. Olinger4, D.
S. Woolum5, K. D. McKeegan1 and D. S. Burnett2. 1Department Earth
and Space Sciences, UCLA, Los Angeles, CA. E-mail: heber@
ess.ucla.edu. 2CalTech, Pasadena, CA. 3Arizona State University, Tempe,
AZ. 4LANL, Neutron Science and Technology, Los Alamos, AZ.
5Department of Physics, CSU, Fullerton, CA.
Introduction: Quantitative understanding of solar wind (SW)
elemental fractionation is required to improve knowledge of the solar
nebula abundances from Genesis samples, in particular abundances of
volatile elements, depleted in CI chondrites. Ratios of elements with low
and high ﬁrst ionization potential (FIP) in the solar wind, e.g., Fe/He, are
higher than photospheric abundances. C, O, and N have intermediate FIP
and are thus critical as to whether this fractionation is stepwise or
gradual as a function of FIP.
Analyses: Genesis solar wind O and C ﬂuences are suﬃciently high
for precise SIMS analysis; however, surface contamination, mixed to
depths as large as 50–100 nm, is a major problem. We adopted 3
mitigations: (1) conventional front side depth proﬁling with low energy Cs
surface cleaning using the CalTech Cameca 7f, and backside depth
proﬁling on a Genesis bulk solar wind sample thinned to 350 nm using
(2) 7f, and (3) nanoSIMS. All three methods gave useful data with the
most precise data from (2).
Results: The Figure inset shows the 7f C concentration measured
versus distance from the backside of the thinned sample. The red portion
of the curve is ion beam mixed surface contamination reaching
instrumental background around 130 nm. Just prior to 200 nm, solar
wind C is measured, rising to about 8 · background levels until
contributions from epoxy binding the sample to a substrate terminate the
analyses at 350 nm. Similar proﬁles were obtained with O. The non-inset
part of the ﬁgure shows that the measured proﬁle matches theoretical
predictions. Interferometry showed that the maximum analysis depth was
set by non-normal incidence of the ion beam with the sample surface.
This eﬀect is reduced with the 20 lm size of the nanoSIMS pits; however,
no improvement in SW peak depth resolution was obtained, probably
because of a greater amount of mixing at the sample-epoxy interface with
the nanoSIMS than with the 7f.
Conclusions: Normalizing to Mg (low FIP element), the Genesis
solar wind (C/Mg) and (O/Mg) ratios are 3.7 and 5.1 respectively,
indicating a constant solar wind/photosphere depletion factor of about
0.38 despite the higher FIP for O (13.6 v 11.3 for C).
A78 73rd Meeting of the Meteoritical Society: Abstracts
