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-P17] Petrology of the Itagai gabbroic body, Aomori Prefecture

*岡澤  誠1山元 正継2 (1.島根大学、2.秋田大学)

キーワード:はんれい岩、ソレアイト、転移ピジョン輝石

Itagai gabbroic intrusion, on the border between Akita and Aomori prefectures along shore of Japan Sea, is one of typical tholeiitic bodies consisting of gabbronorite including inverted pigeonite, clinopyroxene, orthopyroxene, plagioclase, magnetite and ilmenite.
Northern end of the Itagai gabbroic body and the Cretaceous Shirakamidake granitic complex are juxtaposed by a fault. But their geological relationship has been unclear. Magnetic susceptibility of both bodies across the fault was mesured and shows increasing in magnetism of Shirakami granitic rocks near the Itagai gabbro. This suggests that the Itagai body is younger than the Shirakami granitic complex.
This body consists of three layers shown by variation of grain size being medium-, coarse-, and fine-grained from south to north. This indicates that Itagai gabbroic body was formed by at least three time's intrusions of magma, which is supported by the different ratio of Sr isotope and mineral chemistry of each layering.
There are more tholeiitic rocks inside and in contact with the Itagai gabbro such as small dykes, Sugozaki quartz diorite and an andecitic intrusion which covered by non-tholeiitic volcanic breccia, forming about 20Ma(Hayashi and Ohguchi,1998). This suggests that tholeiitic magmatism was continued during Paleogene to Early Miocene.