Laser-Raman spectroscopic studies on graphite from East Antarctica

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We report here the Laser-Raman spectroscopic data on the carbonaceous matter (CM) from Schirmacher Oasis (70°45'S, 11°40'E), East Antarctica for the first time. The sample was collected from the Precambrian rock, which consists of garnet-biotite gneiss. The first order Laser-Raman spectra of the sample shows a strong well-ordered Raman peak (0) at 1581 cm^<-1> and a weak broad peak due to disorder (D) at 1354 cm^<-1>. The intensity ratio disordered-to-ordered Raman peak (D/O)_<area> has been used to estimate the in-plan crystallite size (L_a) of the graphite. The experimental values of D/0=0.143 and D/D+O=0.125 indicate that the CM is well crystallized graphite, thereby indicating the high metamorphic grade of the host rocks. Powder X-ray diffraction studies on the same sample of CM also indicate that the CM is well-crystalline hexagonal graphite with d_<002>=0.3354 nm. The structural parameters obtained by Raman spectroscopic method and the estimated in-plane crystallite size (L_a=298A) indicate that the metamorphic grade of the host rock of the studied sample falls in the upper sillimanite zone. The present study suggests that the peak metamorphic temperature of the host rock could be in the temperature range of about 700℃.
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