Fumarole incrustations at active central american volcanoes
In 11 yr of sampling at 14 volcanoes in Guatemala, El Salvador, Nicaragua and Costa Rica, we have identified 47 minerals in incrustations depositing at approximately 100 different high temperature fumaroles. Most of these minerals are sulfates. The most abundant and most frequently found minerals are: sulfur, hematite, halite, sylvite, gypsum, ralstonite, anhydrite, thenardite and langbeinite. Incrustation suites deposit around fumaroles to produce a zonal pattern which is a response to the rapidly changing temperature and oxygen pressure at the mouth of the vent. The observed zoning pattern can be explained by the reaction of a volcanic gas composed of H2O, SO2, CO2, HC1 and HF, along with trace amounts of volatile cations, which interacts with the atmosphere and the fumarole wallrock. This interaction is aided at lower temperatures by the formation of sulfuric acid. The mineralogies and descriptions of incrustations at fumaroles at a large number of other volcanoes from every part of the world are similar to what we have found in Central America. Thus we believe our conclusions have general applicability.
Geochimica et Cosmochimica Acta
Stoiber, Richard E. and Rose, William I., "Fumarole incrustations at active central american volcanoes" (2003). Department of Geological and Mining Engineering and Sciences Publications. 172.