High CO2 content in magmas of the explosive andesitic Enco eruption of Mocho-Choshuenco volcano (Chile)

Abstract Mocho-Choshuenco volcano has produced several highly explosive eruptions during its history, which make it one of the most hazardous volcanoes in southern volcanic zone Chile, although is still relatively little studied to date. We present a geochemical study products sub-Plinian, andesitic, Enco eruption that occurred about 1600 years ago. determined major and trace elements compositions, as well volatile (H 2 O, CO , Cl, S) contents melt inclusions trapped minerals (olivine, plagioclase, pyroxene) using electron microprobe, ion microprobe (SIMS), 3D confocal Raman mapping. Though whole-rock composition magma andesitic (60.2 ± 1.1 wt.% SiO ), have ranging from 50.3 67.3 wt.%, following magmatic series Mocho-Choshuenco, compositions mafic are close those erupted magmas. Geochemical modeling indicates mixing between an andesitic-to-dacitic magma. Glass analysis revealed typical parental arc values for H O (2.6–3.8 wt.%), S (116–1936 ppm), Cl (620–1439 ppm). However, very high some with concentrations above 4000 ppm (measured glass), suggesting trapping depths > ~ 17–22 km. Presence solid carbonates inside inclusion-hosted bubbles clearly measured glass phase were minimum values. conclude -rich basaltic ascended mixed shallower The cooled exsolved amounts may dramatically increased pressure triggered eruption.