Zambardi, T.; Poitrasson, F.; Quitte, G. and Anand, M.
Silicon isotope variations in the Earth and meteorites.
In: Challenges to Our Volatile Planet : Goldschmidt 2009, 21-26 June 2009, Davos, Switzerland.
A fluorhydric acid-free sample preparation method derived from Georg et al.  has been used to measure the natural variations of silicon isotope compositions in terrestrial
(including 12 geological standard materials) and meteoritic
All measurements were done using a Neptune MC-ICPMS
in medium resolution mode (m/Δm = 7000, peak-edge
definition). Magnesium was used as internal standard for
mass-bias drift correction. The δ30Si values are expressed relative to the NBS-28 silica standard.
IRMM-17 reference material yields a δ30Si of -1.4‰ ±
0.05‰ (2SD, n=11) in agreement with previous data [2-3].
Long-term reproducibilities were obtained for BHVO-2 (δ30Si
= -0.27‰ ± 0.08‰ (2SD, n=30)) and a in-house Si standard
(δ30Si = -0.01‰ ± 0.07‰ (2SD, n=20)) on a 7 months time scale.
Total variation of δ30Si in natural samples ranges from -
0.5‰ to -0.1‰. Comparison with δ29Si values shows that this
isotopic fractionation is mass-dependent. A 0.2‰ isotopic
variation occurs among terrestrial samples suggesting an
enrichment in the heavier silicon isotopes as a function of
magma differentiation, as initially hinted by Douthitt .
Terrestrial samples mean value (δ30SiEarth= -0.23‰) is heavier by about 0.24‰ in δ30Si compared to chondrites. This may be explained by silicon isotope fractionation during planetary accretion and/or differentiation.
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