Mapping water in the mantle: Constraints from seismic attenuation and electrical conductivity under high pressure and temperature

2015 Fiscal Year Final Research Report

• Project/Area Number: 24244087
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Petrology/Mineralogy/Science of ore deposit
• Research Institution: Okayama University
• Principal Investigator: Yoshino Takashi 岡山大学, 地球物質科学研究センター, 准教授 (30423338)
• Co-Investigator(Kenkyū-buntansha): YONEDA Akira 岡山大学, 地球物質科学研究センター, 准教授 (10262841) ; NISHIHARA Yu 愛媛大学, 地球深部ダイナミクス研究センター, 准教授 (10397036) ; YAMAZAKI Daisuke 岡山大学, 地球物質科学研究センター, 准教授 (90346693)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: マントル / 水 / 地震波減衰 / 電気伝導度 / 水素拡散 / 単結晶

Outline of Final Research Achievements

To determine the amount and distribution of water in the mantle, we have tried to determine Q value characterizing the seismic attenuation and the electric conductivity as a function of the water content. The development and installation of the short-period oscillation hydraulic system was carried out to determine the Q value of the water-bearing materials under high temperature and high pressure by in situ X-ray radiography observation. In order to determine electrical conductivity of olivine, wadsleyite and ringwoodite as a function of water, H-D inter-diffusion experiments were conducted using the synthesized single crystal pair. These results enable us to estimate the electrical conductivity at relatively high temperatures. Based on the comparison with the geophysical data, the average amount of water in mantle transition zone is found to be 0.1 wt.%, and there is a wide lateral variation. Hydrous olivine cannot account for the high conductivity anomaly in the asthesnosphere.

Free Research Field

高圧地球科学