For some volcanic or magmatic rock systems associated with Divergent or Hot Spot Zones, there could be either heated hydrothermal reservoirs or fractured hot dry rock, both able to be used to circulate fluids through the reservoirs from injection wells to production wells.
Volatile fluid release includes carbon components and water. These fluids rise up and some end up combining with meteoric water in hydrothermal reservoirs.
Magmatism is melted rock containing many elements which similarly rise up bringing significant heat closer to the surface including into petrothermal reservoirs (fractured hot dry rock).
Surface heat flux is a function of basement rock temperature, magma temperature, crustal thickness, and magma ponding levels with heat conduction through the crust and heat advection by rising melts.
These hydrothermal and petrothermal reservoirs are able to be exploited with production and injection wells to capture the heat for Geothermal energy from surface Binary ORC power generation equipment.
Adapted from Ref. “Groundwater flow and volcanic unrest” Jasim A., Hemmings B., Mayer K., Scheu B. (2018) .In: Gottsmann J., Neuberg J., Scheu B. (eds) Volcanic Unrest. Advances in Volcanology. Springer, Cham. https://doi.org/10.1007/11157_2018_33