Fig. 5: SXAM mapping of a cross-cut through rock core obtained by over-coring.

a Cutting surface of the over-coring core (hole no. 6). b Ca mapping of rock core obtained by over-coring a resin injection hole indicates all observed fractures are sealed by calcite for up to several centimeters from the resin injection hole and that matrix pores in the walls of fractures are also calcite-filled. Squares indicate the observation points shown in (c–e). c, d Optical microscope view (cross-polar) showing calcite clogging fracture flow paths shown in the points of (b). Calcite clogs the flow paths in the rock matrix. Interconnecting calcite crystals effectively fill pore space even in hair cracks observed in the rock matrix (d). e SEM micrograph showing a cross-section through a calcite-filled flow path shown in (b) in which the calcite has a zonal growth texture. f Conceptual view of zonal clogging features observed in and around the flow paths far from the resin injection hole. Within flow paths far from resin injection holes, synthetic calcite forms on both fracture surfaces directly. Microcrystals grew first and larger crystals developed on the microcrystals to reduce the flow-path porosity. Calcite is also developed in the rock matrix near the fracture flow paths due to matrix diffusion of concretion-forming solutes derived from the resin, as shown by Ca maps produced by SXAM (b) and optical microscope (c). The color bar shows the X-ray intensity of measured Ca is shown. EDZ excavated damaged zone. All figures were created by H. Yoshida.