Major and Trace Element Analysis of Irazú Volcano’s Upper Holocene Magmatic Evolution, Costa Rica

The Irazú Volcano is an active andesitic shield volcano located ~15 kilometers northeast of Costa Rica’s second-largest city, Cartago. Tephra deposits from the past 2600 years confirm that Irazú’s history is punctuated with phreatomagmatic, magmatic, and phreatic eruptions that produced ashfall, pyroclastic flows, and lahars. However, geological studies have concentrated on the 1963-1965 eruptions and lack a geochemical assessment of Irazú’s 2,400 years of activity. Employing inductively coupled plasma mass spectrometry (ICP-MS) and x-ray fluorescence (XRF), major and trace elements of ash and whole-rock tephra deposits are correlated with Irazú’s stratigraphy to provide a geochemical characterization, model Irazú’s magmatic evolution, and ascertain eruptive trends. The high-resolution magmatic trends measured in this project are directly linked to the magma's viscosity and mineral content. This work defines a geochemical approach to hazard mapping that could benefit 60% of the nation’s population.