Zn-poor hercynite in felsic gneiss from the Yodoe area, Tottori Prefecture, Japan

Abstract

Gneissose rocks exposed at the Yodoe area, northwestern flank of Mt. Daisen, Tottori Prefecture have been considered as western extension of the Hida metamorphic rocks in the Hida Mountains. We describe a new occurrence of hercynite [(Fe²⁺,Mg,Zn,Mn)(Al,Fe³⁺)₂O₄] in garnet-bearing felsic gneiss from the Yodoe area. Green hercynite occurs exclusively as inclusions in garnet, and is not in direct contact with quartz. The Fe²⁺/(Fe²⁺ + Mg + Zn + Mn) and Al/(Al + Fe³⁺) values of the hercynite are 0.84-0.85 and 0.91-0.92, respectively. The hercynite is characterized by low ZnO content (2.21-2.41 wt%).