Near mid-oceanic ridges, microseismicity develops in large volumes of the oceanic crust and is interpreted to result from the hydration of oceanic rocks with a solid volume increase of up to 50%. Our recent work has demonstrated that this process, called reaction-induced fracturing, occurs in a model system where periclase is hydrated into brucite, and breaks the rock around it. However, the effect of one critical parameter, the pore fluid pressure, remains to be studied because it may control the rate of fracture development. We plan to perform deformation experiments using the new KORE apparatus to elucidate the effect of pore fluid pressure on reaction-induced fracturing. For the first time, we will couple 1) dynamic X-ray tomography experiments under varying pore fluid pressure conditions, up to 80 MPa, and 2) recording of the acoustic emission activities produced by rapid crack growth (i.e., microseismicity). This proposal is part of the ERC Adv. Grant BREAK awarded to the PI.