Cathodoluminescence spectral study of alkali feldspar and plagioclase in Yamato Martian nakhlite meteorites

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Cathodoluminescence spectral study of alkali
feldspar and plagioclase in Yamato Martian
nakhlite meteorites
M. Kayama1, A. Gucsik2, N. Matsuda3, H. Nishido1
and K. Ninagawa4
1Okayama Unversity of Science, RINS, Okayama,
Japan 2Max Planck Institute for Chemistry, Mainz,
Germany 3Okayama Unversity of Science, ISEI,
Tottori, Japan 4Okayama Unversity of Science,
Dept. of Applied Physics, Okayama, Japan
NIPR, Tokyo, 07 June 2007
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Introduction
CL measurement allows
1. Detection and Observation of structural
defects and impurity trace elements
2. Suggestion about crystal fields responsible
for a structural configuration, which is altered
by shock metamorphism
CL characterization of feldspar minerals in
Y000749
and
evaluation of shock event in Y000749
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Cathodoluminescence (CL)
electron irradiation
1 mm
1 mm
CL image of alkali feldspar
Micrograph of alkali feldspar
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Götze, 1998
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Götze, 1998
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CL spectral measurements were performed on
natural and experimentally shocked oligoclases
(An19.7 single crystal shocked between 10.5 GPa
and 45 GPa) and plagioclases from the
equilibrated ordinary chondrites (Dar al Gani,
Tenham) (Kaus and Bischoff, 2000).
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Terrestrial plagioclase (An85)
Plagioclase from lunar crystalline rocks
Plagioclase from lunar breccia
Maskelynite
In a pioneering study, Sippel and Spencer (1970)
observed that the shock metamorphism caused peak
shifts from green peak toward the red peak, peak
broadening and decrease of luminescence intensity
than in the undamaged counterpart in the CL
spectra of shock-metamorphosed lunar feldspars.
They noted that the distortions or disorder in
the crystal field results in crystal field
perturbations and these local variations occur
broadened distribution of excited state energies
due to shock metamorphism.
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Literature Review 1 Götze et al., (2000)
in M. Pagel, V.Barbin, P. Blanc, D. Ohnenstetter
(Eds.) Cathodoluminescence in Geosciences,
Springer, 245-270 2 Petrov (1994) Amer.
Miner. 79, 221-239 3 Marshall (1988), Unwin
Hyman, Boston. 146 pp 4 Hayward (1998), in
L.J. Cabri, D.J. Vaughan (Eds.) Modern Approaches
to Ore and Environmental Mineralogy,
Mineralogical Association of Canada Short Course
Series, 27, pp. 269-325 5 Götze et al.,
(1999) Amer. Miner. 84, 1027-1032 6 Sippel
and Spencer (1970), Proc. Apollo 11 Lunar
Sci.Conf. 3, 2413-2426 7 Ramseyer et al.,
(1992), Tectonophysics 216, 195-204 8 Kaus
and Bischoff (2000), Meteoritics Planet. Sci. 35
A 86 9 Boggs et al., (2001) Meteoritics
Planet. Sci. 36, 783-793.
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1 Measurement
2 Measurement
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A schematic figure showing relationships between
crystal field strength Dq, distance of O-Mn
a, and CL emission ? as a function of the
increasing shock pressure P
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Meteorite
Nakhlite Y000749 (Sub. No. 1-5) minerals
in mesostasis alkali feldspar, plagioclase and
silica minerals
CL image of Y000749
Micrograph of Y000749
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Alkali feldspar and plagioclase
Alkali feldspar (Or80) Plagioclase (Ab70) no
transformation to maskelynite
AF
PL
BSE image of plagioclase
BSE image of alkali feldspar
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Methods
Luminoscope
Observation of CL color image Comparison with
optical image
1 mm
CL image of alkali feldspar
Photograph of Luminoscope
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Methods
SEM-CL
Accelerating voltage 15 kV Beam current 1.0 nA
Measurement of CL spectra Observation of CL image
with SEM and BSE image
Photograph of SEM-CL
Schematic diagram of SEM-CL
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CL images of alkali feldspar and plagioclase
A
Figure (A) CL color images of mesostasis (B) CL
image of alkali feldspar (C) CL image of
plagioclase
B
C
PL
AF
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CL spectra of alkali feldspar
Peak position Blue spectral peak Terrestrial
Y000749 400 nm 420 nm Red spectral
peak Terrestrial Y000749 710 nm 755
nm
CL spectra of alkali feldspar
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CL spectra of plagioclase
CL spectra of plagioclase
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CL spectra of plagioclase
CL spectra of plagioclase
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CL spectra of plagioclase
Peak position Yellow spectral peak Terrestrial
Y000749 560 nm 575 nm Red spectral
peak Terrestrial Y000749 750 nm 780
nm
CL spectra of plagioclase
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Conclusion
CL emission peak of alkali feldspar and
plagioclase in Y000749 differ from that of
terrestrial analogues. UV spectral peak are not
observed in CL spectra of plagioclase in
Y000749 CL spectra of plagioclase in Y000749
show slight peak shift by comparing with
experimentally shocked plagioclase at 20 GPa
Impact pressure shocked on nakhlite is relatively
low
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Thank you very much for your attention