The growing demand for hydrogen necessitates innovative production strategies beyond conventional fossil fuelderived methods. Stimulated geologic hydrogen generation through serpentinization of ultramafic rock is a promising alternative. However, the feedback mechanisms between fluid transport, mineral reactions, and rock deformation that govern the kinetics and evolution of serpentinization remain poorly constrained. This study investigates hydrogen yields and mineral phase transformations during laboratory serpentinization of peridotite. Experiments conducted at 90 degrees C and 0.1 MPa, and 200 degrees C and 6 MPa, show hydrogen yields of 0.5 to 0.9 & micro;mol/g rock and 20.8 to 31.2 & micro;mol/g rock after 30 days, respectively. High-resolution X-ray computed tomography captures the spatiotemporal (4D) evolution of serpentine vein networks during serpentinization, revealing serpentine growth primarily along pre-existing veins and sustaining fluid-mineral interactions through submicron vein permeability. Quantitative volume analyses show that serpentine volume fraction increases by 6.7 +/- 0.93 to 10.2 +/- 1.42 vol% from an initial value of 38 to 39 vol%, resulting in a volumetric strain of + 0.005 +/- 0.00025 to + 0.006 +/- 0.00012 (positive for volume increase) under zero effective stress. These results indicate that serpentine vein growth during serpentinization is primarily driven by mineral replacement at olivineserpentine interfaces rather than by stress-induced fracturing followed by mineral infill, with fluid transport playing an important role in reaction progression. Overall, the findings highlight serpentinization as a coupled hydro-thermo-chemo-mechanical process that can occur over short timescales and at relatively low temperatures in peridotite, features that are desirable for scalable geologic hydrogen stimulation and production.
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