Fuego, Guatemala

Eruptive Style

Fuego is located along at the trenchward end of 10 km fissure containing three other vents, most notably Acatenango. Eruptions of Fuego occur in clusters. Clusters last 20-70 years and are separated by 80-170 years. The latter period has been suggested as the period between magma batches from a lower chamber.

Chemistry and Proposed Magma System

Prehistoric lavas from Fuego are more silicic than historic lavas but all rocks share the same pattern of chemical variation. Historic lavas have been exclusively high-Al2O3 basalts. Chemistry of major elements is consistent with plagioclase, olivine, augite and magnetite fractionation (POAM) from high-Al2O3 basalts. Separate batches of magma can be recognized from trace-element data. This suggests that closed-system fractionation of distinct magma bodies is occurring. Deep fractionation of olivine and clinopyroxene and magnetite out of the primary olivine tholeiite in a deep reservoir is suggested by 1) high concentrations of incompatible elements 2) very low Ni and Sc and 3) highly variable V in Fuego's parent magmas. This reservoir may be located at the base of the crust. Closed-system behavior is indicated by 1) grouping of elements when plotted against stratigraphy, especially Sr 2) different parental trace element compositions required in Rayleigh calculations 3) fractionation trends within batches.

The historic trend toward mafic products is attributed to changes of the parental magma chamber. Current reposes on the order of months of a few years do not allow as silicic magmas to evolve. The Meseta vent, active prior to Fuego erupted more silicic lavas. Chesner et al. propose that the height of Meseta prohibited frequent low-pressure eruptions. After a summit collapse and a slight relocation of eruption, more basic magmas were able to erupt forming the newer Fuego vent. Alternatively, the magma production rate may be increasing thus prohibiting longer repose/assimilation periods.

The Fuego vent is probably fed by a shallow dike-like chamber (0.1 km3) which is supplied by the deeper larger parental chamber discussed above. The magmatic evolution of Fuego is considered less complex than the adjacent Acatenango and Agua vents.

Local Seismicity

Postscript version of plot

Notes and Questions

Selected References

Geochemistry and Evolution of the Fuego Volcanic Complex, Guatemala. JVGR, 21(1984) 25-44