Paulo J. Hidalgo

Ph.D., 2011, Igneous Petrology, Michigan State University
M.S., 2005, Geology, Michigan State University
B.A., 2000, Geology, University of Costa Rica

Igneous and Volcanic Petrology

My research involves applying geochemical and isotopic techniques to understand the origin and evolution of the continental crust. Earth is the only planet in the solar system that has an abundant silicic crust and vast amounts of water. Hence, it is fair to assume that water is necessary for the generation of the andesitic to granitic rocks commonly present underneath continents. In this respect, subduction zones are the most common tectonic setting where water can be readily recycled back into the mantle during magma generation processes. This is the reason why studies on the birthplace of juvenile continental crust have typically focused on subduction zones. The current state of knowledge indicates that some new continental crust appears to be generated by subduction at the edges of existing continents, e.g. in the Andes. This process is, however, dependent on the prior existence of continental crust, and presents a classical chicken-and-egg problem for the origin of the continents. The approach that I have taken to investigate continental crust evolution depends intensively in studying the magma plumbing system from deep to shallow crust using crustal cumulates from island arc settings (see figure below). Through the study of these cumulates I have proposed an alternative model to explain the production of new continental crust through subduction-related magmatism at island arcs that have developed over thick oceanic plateaus. In this model, an over-thickened oceanic basement (e.g. oceanic plateau) could allow for magma storage and differentiation that could result in the typical chemical composition of the continental crust.

Future Research

My future research plans will be oriented towards an integrated approach to shed light on the petrogenesis of a diverse range of volcanic and plutonic rocks. I expect to continue to address planetary processes such as the generation of the continental crust, mantle melting and its chemical domains. Specifically, I will explore experimentally the role of H2O in subduction zone magmas by modifying extensive and intensive variables. In subduction zone settings, mantle melting occurs in response to the addition of an H2O-rich component released from the subducted oceanic lithosphere. Arc magmas inherit their high H2O contents from this process. During my current research, I have found that to produce the typical continental crust (Archean crust) composition from subduction zone settings it is necessary to start with an enriched and hydrated (2-4%) peridiotitic mantle. I will like to place constraints on the degree of mantle enrichment and possible sources of enrichment by running experiments at different pressures and water contents. To understand shallow crustal processes at arcs, one needs to know the melting behavior of the mantle in the presence of excess H2O and my future research will examine this melting process. This new research venture will contribute to understanding arc processes worldwide and by critically reevaluating the wet peridotite solidus under specific enrichment and H2O conditions. Ultimately, my research could produce a viable model for continental crust generation during the Archean.