Fig. 4: Calcite sealing identified in flow paths and host rock matrix promoted by ‘concretion-forming resin’.

a, b All flow-path fractures are sealed by calcite identified in the rock core obtained by over-coring. c Calcite on a flow-path surface identified in the core drilled a distance of 20 cm from a resin injection hole no. 6. The surface of the fracture flow-path is covered only by calcite (there is no resin contributing to sealing) and the morphology of the calcite suggests the channel-like character of the flow-path. d, e SEM photos of calcite filling formed on the surface of the fracture flow path observed in (c). Euhedral calcite crystals (e) cover almost all the fracture surface thereby clogging the porosity of the fracture flow paths. f Core obtained by over-coring injection hole no. 6 shows calcite crystals have formed within the ‘concretion-forming resin’ thereby helping to maintain the durability of its sealing capability. EDZ excavated damaged zone.