In hot dry rock (HDR) reservoirs, fracture networks control the dominant seepage pathways, while complex thermal-hydraulic-mechanical-chemical (THMC) processes occur throughout the reservoir, further complicating heat and mass transfer. Conventional HDR reservoir models typically align fractures with grid interfaces, necessitating extensive unstructured grids and local refinement, whereas embedded grid approaches can circumvent this limitation. However, existing models which are based on embedded grids, often employ a weak coupling scheme for the governing equations in the rock matrix and neglect the intra-fracture coupling effects due to the absence of direct parameters linking fracture aperture and permeability to contact stress on fracture surfaces. To overcome these limitations, this study develops a fully coupled THMC model that integrates the embedded discrete fracture model (EDFM) with the extended finite element method (XFEM), solving all governing equations within a unified embedded grid. The model explicitly relates the aperture and permeability of reduced-dimensional embedded fractures to contact stress, shear dilation, and mineral reactions, and incorporates water–rock interactions involving three reactive minerals. Application to a representative HDR reservoir demonstrates the capability of model to capture the long-term THMC evolution of mineral composition and porosity in the rock matrix, as well as the temporal variations in fracture aperture and permeability.