Volcanism in compressional tectonic settings: Is it possible?

This study presents the first field evidence of emplacement of a huge stratovolcano within contractional tectonics, in spite of the widely accepted idea that volcanism can develop only in extensional or transcurrent tectonic settings. El Reventador volcano (Ecuador) started to grow 0.32 Ma BP and is still active. During pre‐El Reventador times, its substratum has been affected by N‐S‐ to NNE‐striking reverse faults. During late Pleistocene‐Holocene, some reverse faults with the same orientations were still active, locally with a component of right‐lateral strike‐slip motions. Seismicity shows widespread events with intensity up to 6.9 Mw and compression. Some of these faults cut the volcano creating differential uplift along N‐S‐ to NNE‐trending tectonic blocks. Hypocenter swarms and field data indicate east‐vergent basal thrusting under the volcano and N‐S‐trending fault‐propagation folds to the east. A model for magma migration in this setting is proposed, suggesting that similar cases of volcanism within a dominantly contractional tectonic regime may be more frequent than previously thought.