title: Reaction-induced rheological weakening enables oceanic plate subduction.
abstract: Earth is the only terrestrial planet in our solar system where an oceanic plate subducts beneath an overriding plate. Although the initiation of plate subduction requires extremely weak boundaries between strong plates, the way in which oceanic mantle rheologically weakens remains unknown. Here we show that shear-enhanced hydration reactions contribute to the generation and maintenance of weak mantle shear zones at mid-lithospheric depths. High-pressure friction experiments on peridotite gouge reveal that in the presence of hydrothermal water, increasing strain and reactions lead to an order-of-magnitude reduction in strength. The rate of deformation is controlled by pressure-solution-accommodated frictional sliding on weak hydrous phyllosilicate (talc), providing a mechanism for the 'cutoff' of the high peak strength at the brittle-plastic transition. Our findings suggest that infiltration of seawater into transform faults with long lengths and low slip rates is an important controlling factor on the initiation of plate tectonics on terrestrial planets.
authors: Department of Geosciences, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
authors: Ken-Ichi
authors: K
authors: Hirauchi
authors: Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
authors: Kumi
authors: K
authors: Fukushima
authors: Department of Earth Science, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
authors: Masanori
authors: M
authors: Kido
authors: Department of Earth Science, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
authors: Jun
authors: J
authors: Muto
authors: Department of Environmental Studies for Advanced Society, Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan.
authors: Atsushi
authors: A
authors: Okamoto