Isotope Analysis of Oxygen in Rocks and Minerals II. KHF2-CoF3Method for the Liberation of Oxygen from Silicate-and Oxide-Minerals

H. SAKAI; H. HONMA

doi:10.5702/massspec1953.15.95

H. SAKAI, H. HONMA

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1967 Volume 15 Issue 2 Pages 95-103

DOI https://doi.org/10.5702/massspec1953.15.95

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Published: June 25, 1967 Received: April 25, 1967 Available on J-STAGE: June 28, 2010 Accepted: - Advance online publication: - Revised: -
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Date of correction: June 28, 2010 Reason for correction: - Correction: ABSTRACT Details: Wrong : A new technique was described for the liberation of oxygen from various rock-forming minerals by which the samples are decomposed in the fused flux of KHF2 with CoF3 as an oxydizing agent. The liberated oxygen was converted to carbon dioxide by a graphite furnace for the mass spectrometric analysis of the oxygen isotope ratio. The technique has been satisfactorily applied to magnetite and olivine as well as to quartz. In the case of olivine, which is the most resistant to the decomposition among the three minerals, the yield of oxygen close to100%was obtained within10hrs. reaction at380°C. δ18Oow values, the isotope ratios of oxygen in the absolute mean oceanic water scale, found for a magnetite from a granodiorite, for an olivine from a peridotite and for a quartz from a pegmatite were-1.3±0.3, ±3.6±0.3and+12.0±0.9‰, respectively. These values are in fair agreement with those reported by other investigators for the minerals of the similar occurrences. It was also shown that the liberated oxygen tends to be enriched in the heavy isotope when the sample is only partially decomposed. This and other factors which bring serious errors into the final isotope measurements were discussed.
Right : A new technique was described for the liberation of oxygen from various rock-forming minerals by which the samples are decomposed in the fused flux of KHF₂ with CoF₃ as an oxydizing agent. The liberated oxygen was converted to carbon dioxide by a graphite furnace for the mass spectrometric analysis of the oxygen isotope ratio. The technique has been satisfactorily applied to magnetite and olivine as well as to quartz. In the case of olivine, which is the most resistant to the decomposition among the three minerals, the yield of oxygen close to 100% was obtained within 10 hrs. reaction at 380°C.
δ¹⁸O_ow values, the isotope ratios of oxygen in the absolute mean oceanic water scale, found for a magnetite from a granodiorite, for an olivine from a peridotite and for a quartz from a pegmatite were -1.3±0.3, +3.6±0.3 and +12.0±0.9⁰/00, respectively. These values are in fair agreement with those reported by other investigators for the minerals of the similar occurrences.
It was also shown that the liberated oxygen tends to be enriched in the heavy isotope when the sample is only partially decomposed. This and other factors which bring serious errors into the final isotope measurements were discussed.

Date of correction: June 28, 2010 Reason for correction: - Correction: CITATION Details: Wrong : E
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Right : H. P. Taylor, Jr. and S. Epstein, Geol. Soc. Amer. Bull., 73, 675(1962).
T. Tudge, Geochim. Cosmcchim. Acta, 18, 81(1960).
R. N. Clayton and T. Mayeda, ibid., 27, 43(1963).
R. N. Clayton and S. Epstein, J. Geo. l., 66, 352(1958).
E. T. Dontsova, Geokhimiya, 669(1959).
J. R. O'Neil and S. Epstein, J. Geophys. Res., 71, 4955, (1966).
T. Tokuda and K. Kashida, Sci. Pap. Osaka Univ., No. 6, 1(1949).
G.Brauer, “Handbuch Präparativ. Anorg. Chem.,” Ferdinand Enke Verlag, Stuttgart, 1954, p. 207.
H. Sakai and H. Honma, Mass Spectroscopy, 14, 183(1966).
H. Sakai, Mass Spectroscopy, 14, 72(1965).
J. M. McCrea, J. Chem. Phys., 18, 849(1950).
H. Craig, Geochim. Cosmochim. Acta, 12, 133(1957).
G. D. Garlick and S. Epstein, ibid., 31, 181(1967).

Abstract

A new technique was described for the liberation of oxygen from various rock-forming minerals by which the samples are decomposed in the fused flux of KHF₂ with CoF₃ as an oxydizing agent. The liberated oxygen was converted to carbon dioxide by a graphite furnace for the mass spectrometric analysis of the oxygen isotope ratio. The technique has been satisfactorily applied to magnetite and olivine as well as to quartz. In the case of olivine, which is the most resistant to the decomposition among the three minerals, the yield of oxygen close to 100% was obtained within 10 hrs. reaction at 380°C.
δ¹⁸O_ow values, the isotope ratios of oxygen in the absolute mean oceanic water scale, found for a magnetite from a granodiorite, for an olivine from a peridotite and for a quartz from a pegmatite were -1.3±0.3, +3.6±0.3 and +12.0±0.9⁰/00, respectively. These values are in fair agreement with those reported by other investigators for the minerals of the similar occurrences.
It was also shown that the liberated oxygen tends to be enriched in the heavy isotope when the sample is only partially decomposed. This and other factors which bring serious errors into the final isotope measurements were discussed.

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