続成作用および変成作用にともなう炭質物の構造変化(<特集>地球における炭素の循環)

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Carbonaceous material is a common constituent of metamorphosed and unmetamorphosed sedimentary rocks and shows progressive structural changes during diagenesis and metamorphism. Powder X-ray diffraction technique and Raman spectroscopy are applied to the evaluation of structural properties of carbonaceous material during graphitization. The crystallite thickness along c-axis, L_c (002), obtained from the X-ray diffraction profiles of (002) increases with progressing metamorphic grade of the rocks. The lattice strain along c-axis, ε_c, which is determined with (00l) lines of carbonaceous material, decreases with increasing L_c (002). These X-ray diffraction parameters are useful to estimate the degree of graphitization. Raman scattering of carbonaceous material shows two spectral lines around 1350cm^<-1> and 1620cm^<-1>. Raman spectra are sensitive to structural changes of carbonaceous material. Intesity ratio of two lines, I_<1350>/I_<1620> is an indicator to estimate the coal rank and the degree of graphitization. L_c (002) values in two contact aureoles, South Kitakami Mountains and the Kuga area, increase continuously with approaching the granite as a heat source. This fact shows that graphitization is mainly controlled by temperature and that graphitization processes can be applicable to a kind of geothermometer. However, graphitization in regional-metamorphosed rocks of the Hitachi area advances more, compared with that in the contact-metamorphosed rocks of the same metamorphic facies, suggesting that graphitization depends not only on temperature but also on the duration of metamorphism.
地学団体研究会の論文
1994-07-25

著者

土屋範芳
東北大学工学部資源工学科

続成作用および変成作用にともなう炭質物の構造変化(<特集>地球における炭素の循環)

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