JpGU-AGU Joint Meeting 2017

講演情報

[JJ] ポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG73] [JJ] 岩石・鉱物・資源

2017年5月22日(月) 10:45 〜 12:15 ポスター会場 (国際展示場 7ホール)

コンビーナ:齊藤 哲(愛媛大学大学院理工学研究科)、門馬 綱一(独立行政法人国立科学博物館)、野崎 達生(海洋研究開発機構海底資源研究開発センター)、土谷 信高(岩手大学教育学部地学教室)

[SCG73-P21] 愛媛県南部、中新世御内花崗岩質岩体にみられる苦鉄質火成包有岩についての岩石学的研究

塩田 恵美2山崎 楓真2、*齊藤 哲1 (1.愛媛大学大学院理工学研究科、2.愛媛大学理学部)

キーワード:御内岩体、花崗岩、苦鉄質火成包有岩

Mafic igneous enclaves with sub-angular shape are commonly occurred in the Miocene Miuchi granitoid pluton, southern Ehime Prefecture. The mafic enclaves (61-64 wt.% SiO2, 0.5-2.6 wt.% K2O) are composed mainly of plagioclase, biotite, quartz and opaque minerals. Acicular apatites are common in the mafic enclaves. Intergrowth texture of biotite and quartz/plagioclase are locally observed in the biotite-rich mafic enclaves. K2O contents of the mafic enclaves increase with increasing SiO2. Orthopyroxene, locally surronded by biotite, occurs in the mafic enclave with the lowest SiO2 and K2O contents. Biotite-rich reaction rim is observed between the orthopyroxene-bearing mafic enclave and host granite. The host granite samples surrounding the mafic enclave are relatively depleted in the K-feldspar (granodiorite in composition) compared to the dominant rock type of the Miuchi granitoid pluton (monzogranite - granite in composition) (67-78 wt.% SiO2, 3.3-6.5 wt.% K2O). The petrographic and geochemical characteristics of the mafic enclaves are suggestive of interaction with host granite magmas through hydration crystallization reaction: hydrous granitic melt + pyroxene + Fe-Ti oxides ± calcic plagioclase = biotite + quartz ± sodic plagioclase (e.g. Bard et al. 2005, J. Geol.).