Reseach on petrological features of sub-arc mantle by arc-derived peridotites: an ordinary or extraordinaly

2021 Fiscal Year Final Research Report

• Project/Area Number: 16K17834
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Kumamoto University
• Principal Investigator: ISHIMARU Satoko 熊本大学, 大学院先端科学研究部(理), 准教授 (60464046)
• Project Period (FY): 2016-04-01 – 2022-03-31
• Keywords: 島弧マントル / 記載岩石学 / 地球化学 / マントル交代作用 / 変形作用

Outline of Final Research Achievements

Based on our previous research, we detected some (fine-grained) peridotite xenoliths from Avacha volcano record various metasomatic events, and interpreted that the features were obtained by unknown type melt/fluid which derived down going slab. We speculate the characters are not atypical but typical in some mantle wedge beneath the volcanic front. To check the hypothesis, we made petrological and geochemical descriptions of sub-arc mantle derived peridotites and characterized their metasomatic process(es).
We obtained incompatible trace-element (light rare earth and large ion lithophile elements) rich features in some deformed (fine-grained) peridotites (e.g., Finero peridotite massif and Oman ophiolite) and which contain hydrous minerals (amphiboles and phlogopite) and orthopyroxene which implies that the perodotites are metasomatized by hydrous fluid(s) and/or melt(s). We are still not sure the feature is typical or atypical in a mantle wedge, and need much more detailed research.

Free Research Field

岩石学

Academic Significance and Societal Importance of the Research Achievements

カンラン岩捕獲岩や固体貫入カンラン岩体類を用いて，島弧マントルカンラン岩の基本的な特徴とそこで記録された交代作用を明らかにした．観察された特徴の一般性／特殊性についてはまだ明確な答えは得られていないが，条件が揃えばマントル中に遷移金属や白金族元素が濃集すると考えられ，そのメカニズムの解明は全地球的な元素の移動を検討する上で重要である．