Electrical conductivity of old oceanic mantle in the northwestern Pacific I: 1-D profiles suggesting differences in thermal structure not predictable from a plate cooling model

Earth, Planets and Space

Naoto Hirano¹  Natsue Abe²  Hisayoshi Shimizu³  Kiyoshi Baba³  Pengfei Liang³  Noriko Tada³  Ruibai Li³  Tetsuo Matsuno³  Hisashi Utada³  Masahiro Ichiki⁴  Luolei Zhang⁵ 

[1] Center for Northeast Asian Studies, Tohoku University;Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology;Earthquake Research Institute, The University of Tokyo;Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University;School of Ocean and Earth Science, Tongji University;

关键词: Geomagnetic induction;    Marine magnetotellurics;    Electrical conductivity;    Oceanic lithosphere and asthenosphere;    Northwestern Pacific;   

DOI  :  10.1186/s40623-017-0697-0

来源: DOAJ

【 摘 要 】

Abstract Seafloor magnetotelluric (MT) experiments were recently conducted in two areas of the northwestern Pacific to investigate the nature of the old oceanic upper mantle. The areas are far from any tectonic activity, and “normal” mantle structure is therefore expected. The data were carefully analyzed to reduce the effects of coastlines and seafloor topographic changes, which are significant boundaries in electrical conductivity and thus distort seafloor MT data. An isotropic, one-dimensional electrical conductivity profile was estimated for each area. The profiles were compared with those obtained from two previous study areas in the northwestern Pacific. Between the four profiles, significant differences were observed in the thickness of the resistive layer beyond expectations based on cooling of homogeneous oceanic lithosphere over time. This surprising feature is now further clarified from what was suggested in a previous study. To explain the observed spatial variation, dynamic processes must be introduced, such as influence of the plume associated with the formation of the Shatsky Rise, or spatially non-uniform, small-scale convection in the asthenosphere. There is significant room of further investigation to determine a reasonable and comprehensive interpretation of the lithosphere–asthenosphere system beneath the northwestern Pacific. The present results demonstrate that electrical conductivity provides key information for such investigation. Graphical Abstract .

【 授权许可】

Unknown