Granite plutons of high heat production (HHP) form “hot” anomalies that can be easily
identified against the background heat-flow field of the Earth. These zones of higher
than average heat flow are perspective sites for encountering high temperatures at
shallow depth, shallow enough to favor exploitation of geothermal energy. Thus, it is
not surprising that high heat-production granites, from a thermal point of view, are
potential geothermal resources that might someday be harnessed with developing
heat-extraction technologies based on an EGS concept. HHP granites occur throughout
Europe, though in different frequency and volume. Most HHP granites formed during the
Variscan orogeny such as those from SW England, the French Massif Central, and the
Erzgebirge of Germany and the Czech Republic. They also occur in older terranes as in
the Scottish Caledonides and the Proterozoic shields of Fennoscandia, Baltica, and
The nature of geothermal energy in HHP granites has been well investigated as part of
academic research throughout the last three decades. Thus, a wealth of earth-science
information is available that can be used for selecting the most promising sites for
developing a technological system to harness this type of geothermal energy.
This information includes (1) surface geophysical data that assess the lateral and
vertical extent of the granite intrusions and (2) well-logs and drillcore data that
include mechanical and thermal properties of granites and host rocks (geothermal
gradient, thermal conductivity/diffusivity, fracture density, fracture mineralization
etc.) and their chemical and petrological features, and (3) large-scale injection
experiment data to learn about the artificial stimulation of granites or their
metamorphic country rocks.
Other research, conducted especially for the purpose of nuclear-waste disposal, dealt
particularly with the issue of fluid flow and fluid pathways through granite bodies.
Thus, it is time to recycle all this important knowledge and channel an initiative
for the promotion of research and development of this geothermal resource.