Hydraulic properties of the crystalline basement

Hydraulic tests in boreholes, up to 4.5 km deep, drilled into continental crystalline basement revealed hydraulic conductivity (K) values that range over nine log-units from 10^sup -13^-10^sup -4^ m s^sup -1^. However, K values for fractured basement to about 1 km depth are typically restricted to the range from 10^sup -8^ to 10^sup -6^ m s^sup -1^. New data from an extended injection test at the KTB research site (part of the Continental Deep Drilling Program in Germany) at 4 km depth provide K=5 10^sup -8^ m s^sup -1^. The summarized K-data show a very strong dependence on lithology and on the local deformation history of a particular area. In highly fractured regions, granite tends to be more pervious than gneiss. The fracture porosity is generally saturated with Na-Cl or Ca-Na-Cl type waters with salinities ranging from 100 g L^sup -1^. The basement permeability is well within the conditions for advective fluid and heat transport. Consequently, fluid pressure is hydrostatic and a Darcy flow mechanism is possible to a great depth. Topography-related hydraulic gradients in moderately conductive basement may result in characteristic advective flow rates of up to 100 L a^sup -1^ m^sup -2^ and lead to significant advective heat and solute transfer in the upper brittle crust.[PUBLICATION ABSTRACT] Erratum DOI: 10.1007/s10040-007-0214-9