Geological records of transient fluid drainage into the shallow mantle wedge

Kazuki Yoshida; Ryosuke Oyanagi; Masao Kimura; Oliver Plümper; Mayuko Fukuyama; Atsushi Okamoto

doi:10.1126/sciadv.ade6674

Geological records of transient fluid drainage into the shallow mantle wedge

Sci Adv. 2023 Apr 5;9(14):eade6674. doi: 10.1126/sciadv.ade6674. Epub 2023 Apr 5.

Authors

Kazuki Yoshida¹, Ryosuke Oyanagi^{2

3}, Masao Kimura⁴, Oliver Plümper⁵, Mayuko Fukuyama⁶, Atsushi Okamoto¹

Affiliations

¹ Department of Environmental Studies for Advanced Society, Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aramaki-Aoba, Aoba, Sendai, Japan.
² School of Science and Engineering, Kokushikan University, Tokyo 154-8515, Japan.
³ Research Institute for Marine Geodynamics, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan.
⁴ Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
⁵ Department of Earth Sciences, Utrecht University, 3584 CD, Utrecht, Netherlands.
⁶ Graduate School of Engineering Science, Akita University, Akita 010-8502, Japan.

Abstract

Pore fluid pressure on subduction zone megathrusts is lowered by fluid drainage into the overlying plate, affecting subduction zone seismicity. However, the spatial and temporal scales of fluid flow through suprasubduction zones are poorly understood. We constrain the duration and velocity of fluid flow through a shallow mantle wedge based on the analyses of vein networks consisting of high-temperature serpentine in hydrated ultramafic rocks from the Oman ophiolite. On the basis of a diffusion model and the time-integrated fluid flux, we show that the channelized fluid flow was short-lived (2.1 × 10^-1 to 1.1 × 10¹ years) and had a high fluid velocity (2.7 × 10^-3 to 4.9 × 10^-2 meters second^-1), which is close to the propagation velocities of seismic events in present-day subduction zones. Our results suggest that the drainage of fluid into the overlying plate occurs as episodic pulses, which may influence the recurrence of megathrust earthquakes.