Rapid Pleistocene to recent growth of Villarrica volcano

Abstract Villarrica (originally Rukapillán or Quitralpillán ) is the most active and hazardous volcano in the Andean Southern Volcanic Zone. In contrast to nearby Mocho-Choshuenco and Puyehue-Cordón Caulle volcanoes, which have erupted dacites and rhyolites during the last 20 ka, and Calbuco, which has erupted basaltic andesite and andesite since ~ 100 ka, Villarrica has erupted mainly basaltic andesite and is distinguished by two voluminous post-glacial basaltic andesite to andesitic ignimbrites, the 10 km 3 Licán (16.8 ka) and 5 km 3 Pucón (4.0 ka). How Villarrica evolved before, during, and after these ignimbrites remains obscure due to limited geochronology. Whole-rock and glass shard compositions coupled with 40 Ar/ 39 Ar, 3 He, 14 C, and 36 Cl age determinations reveal that Villarrica (1) has erupted basaltic through rhyolitic magmas, but mostly basaltic andesite to andesite, (2) grew at the highest eruptive rate in the arc (up to 1.7 km 3 /kyr) since 181 ka, (3) experienced collapse of the Caldera Pichillancahue during eruption of the Licán ignimbrite at 16.8 ka, and (4) produced multiple parasitic flank eruptions during the last 4 kyr. Magmas that produce the ignimbrites are hypothesized to have been generated by mixing basalt-basaltic andesite and andesite. The high rate of cone growth, young age relative to neighboring volcanoes, and monogenetic eruptions may reflect a thermally immature magma plumbing system beneath Villarrica wherein pre-eruptive magma storage is mainly in the mid- to lower crust and silicic reservoirs are unstable. Our findings allow comparisons of growth rates and magma evolution across several adjacent volcanoes and reveal insights into the differences in magmatic processes and plumbing systems.