R7: Petrology, Mineralogy and Economic geology (Joint Session with Society of Resource Geology)

[R7P-01] The formation of ultra-refractory peridotite from the Kamuikotan belt, Hokkaido

[Presentation award entry]

*Ikuya Nishio¹, Tomoaki Morishita¹, Keita Itano¹, Akihiro Tamura¹, Yuji Ichiyama², Shun Takamizawa², Shoji Arai¹ (1. Kanazawa Uni., 2. Chiba Uni.)

Keywords:Ultra-refractory, Peridotite, Mantle, Olivine, Orthopyroxene

Ultra-refractory peridotites characterized by high forsterite contents and Cr# of spinel were exposed in Takadomari and Horokanai complex from the Kamuikotan belt which represents the Cretaceous subduction zone (Tamura et al., 1999; Takeshita et al., 2018). We re-examine the origin of these peridotites using the mineral chemistry to understand the formation of ultra-refractory peridotites. The mineral chemistry indicates that the Takadomari and Horokanai peridotites are the most depleted peridotites on Earth and formed in the early stage of subduction (Umino et al., 2015).