抄録
Sedimentary rocks from the boreholes of MITI Rumoi, Soma-oki, and Nikaho were analyzed for 3-ethyl-4-methylmaleimide (EMMi) and 3,4-dimethylmaleimide (DMMi) by the chromic acid oxidation method. It had been demonstrated that a 3-ethyl-4-methylpyrrole unit in alkylporphyrins (e.g., etioporphyrin) was converted to a 3,4-dimethylpyrrole unit by heating experiments. The ratio of DMMi to EMMi (i.e., demethylation index) had been shown to have a strong positive correlation with the vitrinite reflectance of the Shinjo region sediments. The demethylation indices in the sediments analyzed in this study were increased with the depth of sediments and also proved to have a strong positive correlation with the vitrinite reflectance of the sediments. Therefore, we support that the demethylation index in sediments is useful as a maturity indicator for the sedimentary organic matter.
