Accommodation Zone

GEOTHERMAL ENERGY

Accommodation Zone:

Accommodation zones occur at fault intersections consisting of belts of interlocking, oppositely dipping normal faults. Multiple subsurface fault intersections in these zones are a favorable host for geothermal activity.

Other definitions:Wikipedia Reegle

Controlling Structures

List of controlling structures typically associated with geothermal systems:

• Major Normal Fault
• Termination of a Major Normal Fault
• Stepover or Relay Ramp in Normal Fault Zones
• Apex or Salient of Normal Fault
• Fault Intersection

• Accommodation Zone
• Displacement Transfer Zone

• Pull-Apart in Strike-Slip Fault Zone
• Intrusion Margins and Associated Fractures
• Stratigraphic Boundaries
• Fissure Swarms
• Caldera Rim Margins
• Lithologically Controlled

Overlapping, oppositely dipping normal fault systems (accommodation zones) that generate multiple fault intersections in the subsurface. Strike and dip symbols indicate tilt directions of fault blocks. Illustration by James E. Faulds.

Faulds classified accommodation zones as a one of two major subsets of fault intersection types that act as structural controls on geothermal systems in the Basin and Range province of the US.

Fault intersections between normal faults and transversely oriented strike-slip or oblique-slip faults account for 22% of the Basin & Range structures known to host geothermal systems as of 2011. Multiple minor faults in these areas create connections between major structures, allowing fluids to flow through highly fractured dilational quadrants.

Accommodation zones between overlapping, oppositely dipping normal fault systems account for 8% of all Basin & Range structures hosting geothermal systems. Multiple fault intersections in the subsurface in these zones enhances permeability and hydrothermal fluid flow. According to Faulds et al. (2011):

"Accommodation zones in normal fault systems are more prevalent within the extensional terrane that characterizes much of the Great Basin northeast of the Walker Lane.”

Examples

Want to add an example to this list? Select a Geothermal Resource Area to edit its "Controlling Structures" property using the "Edit with Form" option.

CSV

Geothermal Resource Area	Geothermal Region	Tectonic Setting	Host Rock Age	Host Rock Lithology	Mean Capacity	Mean Reservoir Temp
Brady Hot Springs Geothermal Area	Northwest Basin and Range Geothermal Region	Extensional Tectonics	Mesozoic	metamorphic rocks	26.1 MW 26,100 kW 26,100,000 W 26,100,000,000 mW 0.0261 GW 2.61e-5 TW	455.15 K 182 °C 359.6 °F 819.27 °R
Stillwater Geothermal Area	Northwest Basin and Range Geothermal Region	Extensional Tectonics	Quaternary	sandstone	47.2 MW 47,200 kW 47,200,000 W 47,200,000,000 mW 0.0472 GW 4.72e-5 TW	447.15 K 174 °C 345.2 °F 804.87 °R