R8: Metamorphic rocks and tectonics

[R8P-04] Origin and metamorphism of serpentinite in the Suo metamorphic rocks in the Nichinan area, SW Japan

*Shunsuke Endo¹, Makoto Okamoto¹, Taiki Nishikawa¹ (1. Shimane Uni.)

Keywords:Antigorite, Clinohumite, Olivine, Serpentinite, Suo metamorphic rocks

The Suo metamorphic rocks in the Nichinan area represent a deeper part of the fossil subduction channel in the Early Jurassic. Antigorite serpentinite occurs as sheet-like bodies in pelitic schist. Relict Cr-spinel in serpentinite shows Cr# = 0.65-0.72, suggesting a refractory mantle origin. Metamorphic assemblage olivine + antigorite + clinohumite + diopside + magnetite is consistent with metamorphic grade of sorrounding pelitic and mafic schists. These lines of evidence suggest an origin of the serpentinite bodies to be the forearc mantle above the subduction channel.