Major tectonic settings that commonly host geothermal systems include subduction zones, rift zones, extensional regimes, and transtensional or strike-slip zones. Hot spots are thought to occur independent of tectonic activity but will be considered a tectonic setting in the context of geothermal areas because they do not fit into any other category.
|Extensional Tectonics||Crustal extension (or lithospheric extension) results in a thinning of the crust, bringing the Earth’s surface closer to the hot mantle which increases heat flow. This high heat flow often results in moderate temperature (190-230°C) geothermal resources.|
|Subduction Zone||Subduction zones occur where one tectonic plate is pulled under another. Most often the subducting plate is oceanic crust and contains many hydrous minerals. As the oceanic plate subducts it dewaters into the mantle, lowering the melting temperature of the surrounding mantle which causes flux melting of the mantle into magma. This magma rises up and creates volcanic arcs. These volcanic arcs have high heat flow from the magma plumes and related intrusives. The associated deformation and heat is conducive to high temperature (230-300°C) geothermal systems.|
|Rift Zone||Rift valleys occur at divergent plate boundaries, resulting in large graben structures and increased volcanism. Rift zones may also give way to leaky transform faults that can contribute to increased volcanism.|
|Hot Spot||Hot spots are volcanic regions thought to be fed by magmatic plumes from the mantle or anomalously high heat flow. As plates move the hot spots remain in place, causing strings of progressively younger volcanoes to form.|
|Non-Tectonic||Many geothermal areas may be considered to have no tectonic contribution to the geothermal resource. These areas are thought to have high heat flow resulting from high radiogenic sources beneath the crust, typically located within continental interiors.|
|Strike-Slip||Regions affected by strike-slip tectonics show significant lateral displacement along major structures. These lateral structural trends create increased permeability for hydrothermal fluid migration where they intersect other major tectonic features.|