Japan Geoscience Union Meeting 2016

Presentation information


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

[S-CG63] Dynamics in mobile belts

Mon. May 23, 2016 9:00 AM - 10:30 AM A08 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Norio Shigematsu(Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Aitaro Kato(Graduate School of Environmental Studies, Nagoya University), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Chair:Tohru Watanabe(Gradudate School of Science and Engineering, University of Toyama), Masaoki Uno(Graduate School of Environmental Studies, Tohoku University)

10:00 AM - 10:15 AM

[SCG63-05] Mechanical response of polycrystalline rock during hydration reactions –Experimental investigation of reaction-induced stress and strain in CaSO4-H2O system–

*Masaoki Uno1, Syuntaro Masuda1, Nobuo Hirano1, Atsushi Okamoto1, Noriyoshi Tsuchiya1 (1.Graduate School of Environmental Studies, Tohoku University)

Keywords:Reaction induced stress, Hydration reaciton, Mechanical behavior

Dehydration and hydration reactions deep in the Earth control the water budget in the subduction zone system. Hydration reactions in particular, associate large solid volume changes. Such solid volume changes can induce large stress by the release of Gibbs free energy during the reactions, which can be larger than the strength of rocks and generate fracturing. However, whether the volume change in hydration reactions causes fracturing, enhance fluid flow and promote further hydration reactions, or it fills in the pores, reduces fluid flow and suppresses further hydration, is largely unconstrained. Here we explored mechanical responses of polycrystalline rock through hydration reactions CaSO4 + 2 H2O → CaSO4•2H2O.
Although the samples have high porosity (ø = 20–35%), direct measurement of reaction-induced strain under constant load experiments revealed that reaction-induced bulk strain does occur under loadings of 0.01–10 MPa. The increase of loading enhances deformation mechanisms such as pressure-solution creep, and the amount of reaction-induced bulk strain decreases. Constant volume experiments revealed that reaction-induced stress increases linearly with reaction rate. These results suggest that the mechanical behavior during hydration reaction is primary controlled by the competition between the reaction rate and deformation rate.