日本地球惑星科学連合2019年大会

講演情報

[J] 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-CG52] 岩石・鉱物・資源

2019年5月30日(木) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:野崎 達生(海洋研究開発機構海底資源研究開発センター)、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)、土谷 信高(岩手大学教育学部地学教室)

[SCG52-P07] マラウイ南部の基盤岩類にみられる原生代火山弧火成作用と高度変成作用

*角替 敏昭1Uthup Sam1Nyirongo Mzee Wandembo2Rahman Md. Sazzadur1高村 悠介1髙橋 一輝1 (1.筑波大学、2.マラウイ科学技術大学)

キーワード:モザンビーク帯、クーンガ造山帯、東アフリカ造山帯、グラニュライト、相平衡モデリング

The basement rocks in southern Malawi form part of the Mozambique Belt (or the southern Irumide Belt) that correspond a typical example of Neoproterozoic collisional orogens in southeastern Africa. The dominant lithologies in Lilongwe-Zomba-Blantyre area in southern Malawi are biotite gneiss (biotite + quartz + microcline + plagioclase), charnockite (orthopyroxene + K-feldspar + quartz + plagioclase + ilmenite + magnetite), and mafic granulite (plagioclase + clinopyroxene + garnet + calcic amphibole + quartz + orthopyroxene + ilmenite) which are intruded by syenite (K-feldspar + calcic amphibole + biotite + quartz + clinopyroxene) and granite (quartz + K-feldspar + plagioclase + biotite). Garnet in the mafic granulite is often mantled by plagioclase + orthopyroxene coronae, suggesting post-peak decompression. Phase equilibria modeling of the mafic granulite in the system NCKFMASHTO yielded the peak metamorphic condition of 800-920 oC and ~10 kbar with a clockwise P-T evolution. Major, minor, and REE geochemical data for selected felsic orthogneisses suggest arc-magmatic signatures of the rocks. The results of this study suggest that the orthogneisses in southern Malawi corresponds to a Neoproterozoic magmatic arc unit that was probably metamorphosed at high- to ultrahigh-temperature conditions during the latest Neoproterozoic East-African and Kuunga orogens.