Structure of Active Fumarole Fields: An Integrated Geophysical and Geochemical Approach

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Physical models of flow in medium- and high-temperature fumarole fields suggest that mass flow will exert a strong control on fumarole temperature in most circumstances. The PIs plan to monitor temperature and mass flow continuously to test this relationship in three active fields. These fields are on Volcano Colima, Mexico, Poas, Costa Rica, and Galeras, Colombia, and encompass a range of hydrothermal regimes. At Galeras, young fumaroles are likely a manifestation of forced convection of magmatic and deeply circulating meteoritic fluids. At Poas, shallow free convection likely dominates flow. Colima represents a flow regime intermediate between the other two. The time scales and interdependence of temperature, mass flow, and geochemistry will vary between these systems. Geochemical data, particularly stable and cosmogenic isotopes, will help distinguish more clearly between shallow free convection and fumaroles fed by forced convection from relatively deep or magmatic sources. Differentiation of these transport mechanisms is important to the understanding and interpretation of observed changes in fumarole activity at active volcanoes.