[S-CG60] 岩石・鉱物・資源

[SCG60-P11] 角閃石地質圧力計を用いた甲斐駒ヶ岳花崗岩質岩体の固結深度の検討

渡邉 早姫¹、*齊藤 哲² (1.九州大学大学院理学府、2.愛媛大学大学院理工学研究科)

キーワード：甲斐駒ヶ岳岩体、花崗閃緑岩、角閃石地質圧力計

The Miocene Kaikomagatake pluton is one of the Neogene granitoid plutons exposed in the Izu Collision Zone. The pluton intrudes into the Cretaceous to Paleogene Shimanto accretionary complex of the Honshu arc along the Itoigawa-Shizuoka Tectonic Line. The pluton consists of hornblende– and biotite-bearing granodiorite, monzogranite and granite (sensu stricto). In order to constrain the emplacement depth of the pluton, we applied the Al-in-hornblende barometry. We used samples with mineral assemblage of hornblende + biotite + plagioclase + quartz - K-feldspar + Fe-Ti oxides. Rim compositions of hornblende were used for barometry. Applying the barometry for 6 samples yielded ~2.3 - 3.4 kbar showing relatively low pressures in northern area of the pluton. The estimated pressures correspond to ~9 - 13 km for the emplacement depth of the Kaikomagatake pluton.