Anorogen

Anorogen, or more commonly anorogenic, is a geological term used to describe regions or processes that are not associated with orogeny, the large-scale mountain-building typically linked to plate tectonics at convergent boundaries. The standard form in current literature is anorogenic, with anorogen as a less common noun form.

In practice, anorogenic settings are those characterized by relative tectonic stability and a lack of active orogenesis. They often occur in the interior of tectonic plates, known as cratons or shields, where crust is ancient, deformation rates are low, and there is little evidence of recent crustal thickening or major uplift. These regions may nonetheless experience intraplate volcanism or localized magmatic activity, but not the widespread deformation typical of orogenic belts.

Examples commonly cited as anorogenic contexts include parts of the Canadian Shield, the Fennoscandian Shield, and other ancient cratons that form the stable cores of continents. In contrast, orogenic regions include active mountain belts such as the Himalayas, the Alps, and the Andes, where compression, thrust faulting, and significant metamorphism shape the crust.

The term helps geologists contrast tectonic regimes: orogenic domains are associated with mountain building and crustal thickening, while anorogenic domains are associated with relative tectonic quiet and long-term stability. Etymologically, it derives from Greek roots meaning not mountainous or non-mountain forming.

See also: orogeny, craton, shield, intraplate tectonics.