Petrology of anthracite in the Permian Funabuseyama limestone, Mino Belt, central Japan

Abstract

Several coal seams occur in the Parafusulina and Neoschwagerina zones of the Permian Funabuseyama Limestone, which consist of shallow marine sediments overlying the top of a basaltic seamount. These coal seams are of limited extent, and show extreme variation in thickness. Reflectance measurements show that vitrinite in the coal is optically biaxial. Vitrinite reflectance ranges from 2.9 to 3.0% ̄Rmax, 2.7% ̄Rint, and 2.2 to 2.3% ̄Rmin (anthracite in rank). Although liptinite cannot be distinguished from vitrinite at the position of apparent maximum reflectance of vitrinite, original structures are still deiscernible at the position of apparent minimum reflectance. Fusinite, semifusinite and inertodetrinite ar consistuent macerals of inertinite group. The coal contains 69% vitrinite (original macerals: vitrinile+Liptinite) and 31% inertinite. Sea level fluctuation related to the Gondwana glaciation occurred in the late Paleozoic. The coal seams were formed on the surface of the island which was formed by the seamount exposure of the above the sea at the time of lowering of sea level. Anthracitization was caused by the igneous activities of the Late Cretaceous age in the Mino Belt.