Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG61] Dynamics in mobile belts

Tue. May 28, 2019 9:00 AM - 10:30 AM Convention Hall A (2F)

convener:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology), Chairperson:Keisuke Yoshida(東北大学大学院理学研究科 地球物理学専攻), Masaoki Uno(東北大学)

9:15 AM - 9:30 AM

[SCG61-14] Experimental investigation of reaction-induced stress and permeability evolution in MgOH2O system

*Masaoki Uno1, Hisamu Kasahara1, Atsushi Okamoto1, Noriyoshi Tsuchiya1 (1.Graduate School of Environmental Studies, Tohoku University)

Keywords:Reaction-induced stress, Reaction-induced fracturing, permeability

Crustal and mantle hydration reactions at subduction zones accompany large solid volume change as much as several vol.% to several tens of vol.%. Such large solid volume change can generate stress and fractures, accelerate reactions and fluid migrations (e.g., Kelemen and Hirth, 2012), and potentially influence the fluid transport in the crust and mantle (e.g., Jamtveit et al., 2000). Field observations of serpentinization and peridotite carbonation suggest fracture generation and permeability enhancement by such “reaction-induced stress” (e.g., Jamtveit et al., 2008; Plumer et al., 2012). However, the permeability enhancement during hydration reaction have not been reproduced by experiments, and the mechanisms and conditions of permeability enhancement by volume-increasing reactions remain largely unknown.
To understand the controlling mechanisms of fluid flow during hydration reactions, we show one of the first experimental trial to measure the permeability evolution during hydration reactions. We use MgO–H2O system, where periclase (MgO) react with H2O to produce brucite (Mg(OH)2). The reaction involves solid volume increase of as much as +119%. Our earlier experiments have revealed that the reaction-induced stress in this system are controlled by the competition of reaction rate and stress-dependent deformation rate, and exceeds 40 MPa in this system which well exceeds the tensile strength of crustal rocks.
In this presentation, we have conducted flow thorough experiments to reveal the permeability evolution during hydration reactions. Experiments were conducted with sintered MgO with 4–14 vol.% porosity, under 100–300°C with 5–50 MPa confining pressure and 5–15 fluid pressures. Preliminary experiments showed rapid permeability decrease in 2–3 orders, and finally the stainless sleeve broke by the reaction-induced expansion. The rate of permeability decrease is a function of the confining pressure, suggesting that the deformation of the reactant (brucite) has significant control over the permeability evolution during hydration reactions. We will present further experiments with various reaction rate/deformation rate ratios, and discuss the controlling factors of permeability enhancement/reduction during hydration reactions.

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Jamtveit, B., Mathe-Sørenssen, A., Kstenko, Olga., 2008. Earth and Planetary Science Letters 267, 620–627.
Kelemen, P.B., Hirth, G., 2012. Earth and Planetary Science Letters 345–348, 81–89.
Plümper O., Røyne, A., Magrasó, A., Jamtveit, B., 2012. Geology 40, 1103–1106.