Creation of Interface Petrology with a New Grain Liberation Method and X-ray CT Imaging

2015 Fiscal Year Final Research Report

• Project/Area Number: 25610154
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Tohoku University
• Principal Investigator: NAKAMURA MICHIHIKO 東北大学, 理学(系)研究科(研究院), 教授 (70260528)
• Co-Investigator(Kenkyū-buntansha): TANI Kenichirou 国立科学博物館, 研究員 (70359206) ; OKUMURA Satoshi 東北大学, 大学院理学研究科, 助教 (40532213)
• Co-Investigator(Renkei-kenkyūsha): YOSHIDA Takeyoshi 東北大学, 大学院理学研究科, 名誉教授 (80004505) ; SASAKI Osamu 東北大学, 学術資源公開センター, 准教授 (60222006)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 超臨界流体 / 捕獲岩 / 上部マントル / 下部地殻 / 二面角 / 粒界 / 地震波速度

Outline of Final Research Achievements

We have investigated mafic and ultramafic xenoliths from lower continental crust and upper mantle from various localities in the world by using a high voltage pulse power fragmentation method and X-ray CT imaging. Most of the xenoliths samples included intergranular pores that should have been filled with aqueous fluids at high pressure and temperature. The local volume fraction of the pores was at most 5 %.The three-dimensional shape of the pores were polyhedral - oblate spheroidal. Based on these volume fraction and shapes of the fluids, the relative decrease of dlnVs to dlnVp, the Rsp value, was estimated to be 0.9.The dihedral angles between mantle xenoliths and isolated intergranular fluids were variable, dependent on the localities of the xenoliths samples. This means that shapes of the intergranular fluids may represent the carbon dioxide content in the fluids.

Free Research Field

岩石学，火山学