The largest volumes of peralkaline silicic rocks are found in areas of epeirogenic uplift and rift formation on the continents, but they may also form in several other tectonic settings, such as the oceanic islands, during the later stages of orogenic cycles, as isolated occurrences in active mobile belts, and in areas of extensional tectonics at or near continental plate margins. Their emplacement is effected during periods of dominantly tensional stresses.