Geochemical compositional changes of the upper mantle by subducting slab-derived aqueous fluid: Contraints from the Pinatubo peridotite xenoliths

2014 Fiscal Year Final Research Report

• Project/Area Number: 24540511
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Science of ore deposit
• Research Institution: Kyoto University
• Principal Investigator: YOSHIKAWA Masako 京都大学, 理学(系)研究科(研究院), その他 (00378605)
• Co-Investigator(Renkei-kenkyūsha): ARAI Shoji 金沢大学, 大学院自然システム学系, 教授 (20107684) ; KOBAYASHI Tetsuo 鹿児島大学, 大学院理学研究科, 教授 (70112430)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: かんらん岩捕獲岩 / 沈み込み帯 / 交代作用 / ピナツボ火山 / 微量元素組成 / Sr-Nd同位体比

Outline of Final Research Achievements

Mantle xenoliths brought by subduction-zone magmas can record metasomatism in the mantle wedge (e.g. Arai and Ishimaru, 2008). Pinatubo volcano is located at the volcanic front of the Luzon arc of the Philippines. We present mineral major element compositions, and trace element and Nd-Sr isotopic compositions of amphibole in the Pinatubo peridotite xenoliths, which were observed in the dacite of the 1991 Pinatubo pyroclastic flow deposit. The amphibole exhibits enrichment of fluid-mobile elements such as Rb, Ba, U, Pb, and Sr, and Nd-Sr isotopic features reflecting mixing between asthenospheric mantle and subducting oceanic crusts. These petrological and geochemical characteristics of these mantle xenoliths suggest that mantle wedge beneath the Pinatubo volcano was metasomatized by aqueous fluids derived from subducted oceanic crust.

Free Research Field

同位体岩石学