Major element chemistry of the march-april (1982) Chichon volcanic

Abstract

Major-oxide chemical analyses and petrographic studies of Chichon volcano's March-April eruptive products showed a high percentage of juvenile material. Samples were generally classified as high-alkali andesites with zoned plagioclase, hornblende, augite and biotite as the main minerals. The K20-Si02, MgO-(FeO+ Fe203) and AFM diagrams suggest a calcalkaline-shoshonite, probably subduction related origin of the magma,that does not seem to be related to the Tuxtla volcanics. A high degree of evaporite contamination is reflected in the high alkali and calcium percentage as well as in carbonate xenoliths and anhydrite crystals in the ash. There is an apparent silica increase during each eruption.