For some volcanic, magmatic, or intrusive rock systems associated with Subduction 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 from subducted crust includes carbon components from organic matter, carbonates, water and hydrous materials. These fluids rise up and some end up in deep hydrothermal reservoirs.
Magmatism is melted slab 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 Moho 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. “Volatiles in subduction zone magmatism”, Georg F. Zellmer, Marie Edmonds and Susanne M. Straub, Geological Society, London, Special Publications, 410, 1-17, 13 November 2014, https://doi.org/10.1144/SP410.13agmatism”