Fig. 7. Negative log of the aqueous HCO-3 concentration in fractures (dashed lines) and matrix (solid lines) as a function of time at about 200 (red) and 400 (blue) m, for the conditions and time span represented in Fig. 5. Approximately 10000 yr of the initial steady-state conditions are shown. The period of time over which the infiltration flux and surface temperature changes occur is indicated by the shaded region labeled Perturbation Period.