TRACE ELEMENT GEOCHEMISTRY AND GEOCHRONOLOGY OF IRAZÚ VOLCANO, COSTA RICA

Located ~15 kilometers northeast of Costa Rica’s second-largest city, Cartago lies the active andesitic Irazú Volcano. Tephra deposits from the last 2600 years confirm phreatomagmatic, magmatic, and phreatic eruptions that produced lahars, ashfalls, and pyroclastic flows. Despite the geologic research focused on the volcano’s recent eruptions (1963-1965), high-resolution geochemical analysis is scarce. Major and trace elements of whole-rock tephras and ash deposits were measured by inductively coupled plasma mass spectrometry (ICP-MS) and x-ray fluorescence (XRF). Coalescing this geochemical characterization with Irazú’s stratigraphic columns illustrates the volcano’s volatile propensities as the magmatic trends analyzed are a result of the magma’s mineral assemblage and viscosity. This geochemical approach to hazard mapping could benefit 60% of the nation’s population. The influence of this study is shown by our international and local partnerships with the National Risk Prevention Commission and Emergency Care (CNE) of Costa Rica, the Costa Rican National Park Service, the local ASADA (Community Water Management Association), and the University of Barcelona School of Geographic Sciences. Understanding the variety of volcanic hazards as they relate to the composition of tephra is crucial. Our findings contribute to the development of more robust and effective disaster preparedness and response systems, as well as, generate local educational programs regarding Irazú’s volcanic trends.