Redox state of mantle wedge inferred from the mantle section of the Oman ophiolite

2016 Fiscal Year Final Research Report

• Project/Area Number: 26610173
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Niigata University
• Principal Investigator: Takazawa Eiichi 新潟大学, 自然科学系, 教授 (80222082)
• Co-Investigator(Renkei-kenkyūsha): SATISH-KUMAR M 新潟大学, 自然科学系, 教授 (50313929)
• Research Collaborator: AKASAKA Masahide
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: オマーンオフィオライト / マントルセクション / マントルウェッジ / 酸化還元 / フラックス溶融 / 沈み込み帯

Outline of Final Research Achievements

We studied the spatial distribution of oxygen fugacity in the Fizh mantle section of the northern Oman ophiolite as an analog for the redox state of mantle wedge. The delta log fO2 relative to FMQ buffer of harzburgites and dunites were calculated following the method of Ballhaus et al. (1991). The values range from FMQ-3.3 to +1.8 and tend to decrease from the crust-mantle boundary (Moho) to the basal part of the mantle section. Dunites are more oxidized than harzburgites. The Fe3+/∑Fe ratio of spinel were evaluated by Mossbauer spectroscopy. The difference is negligible compared to the whole range. The V/Sc and Zn/Fe ratios of whole rock peridotites show a strong negative and positive correlations with delta log fO2 (FMQ), respectively, indicating the observed variation and tendency of delta log fO2 (FMQ) are consistent with residues formed by flux melting of mantle section with a reduced melt/fluid derived from subducted sediment.

Free Research Field

岩石学