HR: 0800h
AN: T21A-0502    [Abstracts]
TI: Laser Raman study on microdiamond in UHP marbles from the Kokchetav Massif
AU: * Adachi, T
EM: t-adatchi@fuji.waseda.jp
AF: Department of Earth Sciences, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo, 169-8050 Japan
AU: Ogasawara, Y
EM: yoshi777@waseda.jp
AF: Department of Earth Sciences, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo, 169-8050 Japan
AB: Laser Raman analyses were conducted on the microdiamonds in dolomite marble, calcite marble and garnet-biotite gneiss from Kumdy-kol, Kokchetav Massif, northern Kazakhstan. Raman spectra were obtained by a Jobin Yvon LabRam300 Raman Micro-Spectrometer equipped with confocal optics and air cooled CCD detector at Waseda University. The laser beam was 514.4 nm Ar laser at 10 mW and was focused at 1 micrometer diameter. Acquisition time was 5s and accumulation number was 5 times. Peak positions and full width at half maximum (FWHM) of a Raman band were determined by the Gaussian/Lorentzian fitting of spectra. The number of analyzed spots are 98 spots of 27 grains of S-type in dolomite marble (core: 42 spots, rim: 46 spots), 27 spots of 9 grains in calcite marble, and 15 spots of 13 grains in garnet-biotite gneiss. The peak positions of Raman band were at about 1332 cm-1, and significant differences of the peak positions did not detected. Significant differences in FWHM of Raman band were confirmed in each occurrence as follows: 1.S-type core in dolomite marble: 4.26 to 5.73 cm-1 (average: 4.69 cm-1) 2.S-type rim in dolomite marble: 3.59 to 5.01 cm-1(average: 4.17 cm-1) 3.Calcite marble: 2.99 to 3.64 cm-1 (average: 3.28 cm-1) 4.Garnet-biotite gneiss: 4.69 to 5.61 cm-1 (average: 5.17 cm-1) On S-type microdiamond, the rim has smaller FWHM than the core, and this is consistent with those by Ishida et al. (2003). Microdiamond in calcite marble has the smallest FWHM among all occurrences although other features are similar to R-type and the core of S-type. Microdiamond in garnet-biotite gneiss has relatively large FWHM. The cause of such differences in FWHM is still unclear; however, we may use FWHM of Raman band to characterize microdiamond in UHP metamorphic rocks. We also conducted mappings of Raman bands and related features covering area of several tens square micrometers for diamond-bearing composite inclusions in garnet. This technique is highly effective to understand FWHM distribution in diamond aggregates, phase identification and distribution in micrometer scale in composite inclusions. References Ishida et al. (2003): Journal of Metamorphic Geology, Vol. 21, p. 515-522.
DE: 3600 MINERALOGY AND PETROLOGY (replaces
DE: 3620 Crystal chemistry
DE: 3660 Metamorphic petrology
DE: 3694 Instruments and techniques
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting