Reaction‐Induced Fracturing: When Chemistry Breaks Rocks.

Reaction‐induced fracturing occurs when fluid‐rock interactions lead to the growth of a mineral phase that produces a volume increase, which perturbs the stress field and can cause fracturing in the surrounding rock. This process may occur with a positive feedback loop because, as more fractures are formed, more water can infiltrate the pore space, enhancing the kinetics of reaction. Yoshida et al. (2020, https://doi.org/10.1029/2020JB020268) have studied and modeled reaction‐induced fracturing in oceanic rocks collected during the Oman Drilling Project. These rocks have been intensively hydrated by a process called serpentinization, which has profound geodynamic implications. The authors couple detailed microstructural observations and numerical modeling of reaction‐induced fracturing that incorporates permeability evolution. Building on the outcomes of their study, I discuss here the current knowledge of the reaction‐induced fracturing process, in which chemical forces control rock fracture in various geological environments. Based on recent experimental results and molecular dynamics simulations, I discuss the conditions under which reaction‐induced fracturing may either self‐amplify or slow down and even stop. Plain Language Summary: In the oceanic crust, rocks may interact with oceanic fluids and become hydrated, producing a new class of minerals called serpentine. These minerals have a larger specific volume (+50%) and smaller density (−25%) than the original rock. Two main hypothesis have been proposed to explain how this volume and mass difference may be accommodated: (1) either the transport of dissolved elements by intense fluid circulation removes significant mass from the original rock and thus keeps a constant volume, or (2) the volume of the initial rock increases by the opening of fractures that accommodate the volume increase of the new minerals. Rocks collected during the Oman Drilling Project have recorded microstructures that demonstrate that this second hypothesis better matches the observations. Both detailed observations of oceanic rocks and mechano‐chemical numerical simulations demonstrate that as mineral transformation occurs, the generated stresses are high enough to fracture the surrounding rock, and accommodate volume expansion. This mechanism, called reaction‐induced fracturing, involves an intricate coupling between chemical and mechanical forces that could self‐amplify or self‐stop the overall rock transformation process. Key Points: Couplings between chemical and mechanical forces may lead to rock fracturing, with important geodynamic consequencesThis process is called reaction‐induced fracturing and involves positive and negative feedback loopsSerpentinization of the Oman ophiolite rocks is controlled by reaction‐induced fracturing [ABSTRACT FROM AUTHOR]