Petrological and geochemical features of the upper mantle beneath a volcanic front

日本鉱物科学会研究奨励賞第回受賞者 受賞記念研究紹介 火山フロント下，上部マントルの岩石学的・化学的特徴Petrological and geochemical features of the upper mantle beneath a volcanic front 石丸 聡子(Satoko ISHIMARU) Peridotite xenoliths derived from the upper mantle give us important information about partial melting and subsequent modiˆcation processes, i.e., mantle metasomatism.We examined a large number of mantle peridotite xenoliths from Avacha volcano, located on the volcanic front of southern Kamchatka arc, to reveal that they are residues of high degree of mantle melting and experienced extensive silica addition.We inferred that the slab-derived ‰uids are closely related with both of the processes, and the degrees of melt extraction and silica addition to the mantle wedge tend to decrease with an increase of the distance from the trench.In addition, we found several new mantle metasomatic events recorded in the Avacha peridotite xenoliths: e.g., the mantle reduction and Ni metasomatism.We consider such peculiar metasomatisms are possibly speciˆc to the sub-frontal mantle, although detailed petrological features and metasomatic processes from other volcanic front regions have not been fully understood due to the paucity of mantle peridotite xenoliths there.More thorough research about the petrological nature of sub-arc mantle and the mantle processes is needed for complete understanding of sub-arc mantle and its metasomatism by slab-derived ‰uids or melts.