Knowledge Bank

Volcán de Pacaya is a volcanic complex that lies within the Central American Volcano Arc, formed by the subduction of the Cocos plate beneath the Caribbean Plate. In 1961, it began erupting following a 76-year dormancy. The dominant lithology of the lavas erupted during this time has been olivine-bearing basalt. Noble gas isotope ratios can provide chemical signatures for the source of magma, whether it be a subducting plate causing flux melting or mantle upwelling and decompression melting caused by crustal thinning. The 3He/4He ratio from this study indicated that mantle input has been occurring into Pacaya’s magma system since at least 1961. Helium isotope signatures of back-arc volcanism and midocean ridge basalts occur within these lavas. The argon isotopes indicate that the magma has been enriched with mantle material and that the magma did not fractionate before eruption. Lastly, the neon isotopes indicate that some crustal material is present within Pacaya’s magma, but it is dominated by a mantle signal.