Host: Japan Association of Mineralogical Sciences
Orthopyroxene-bearing porphyritic granodiorite was found as a new lithotype in the Ohgi tonalite, of which main lithoptype is the porphyritic hornblende biotite granodiorite. Both lithotypes consist of quartz, plagioclase, orthoclase, biotite, hornblende, ilmenite ±titanite and ±magnetite and porphyritic orthopyroxene, clinopyroxene, hornblende and plagioclase are included in the new lithotype. Cooling process of the Ohgi tonalite was envisaged by applying geothermobarometers to core compositions of porphyritic orthopyroxene, clinopyroxene and plagioclase and to hornblende and plagioclase in the matrix of both lithotypes, suggesting that the Ohgi tonalite experienced an isobaric cooling from 820 - 880°C to 690 - 740°C at 2.5 - 4.5 kbar.
