Zincian hercynite from the Ryoke Zone in the Seto Inland Sea area

Abstract

Zincian hercynite-bearing pelitic gneiss is found from the Ryoke Zone of the Seto Inland Sea area, southwest Japan. The rock has the mineral association of biotite, muscovite, hercynite, sillimanite, plagioclase, quartz, graphite, ilmenite, tourmaline and apatite. Andalusite, cordierite and K-feldspar are sometimes associated with the above paragenesis. The hercynite is always included in the porphyroblastic sillimanite and shows the chemical composition of He_{62.7_??_73.6}Ga_{13.5_??_25.4}Sp_11.9-13.1. Based on the microscopic texture and chemistry of hercynite and sillimanite, it has been inferred that the hercynite is recrystallized at the climax of the regional metamorphism at the expense of staurolhte.