Doctoral Defense in Geology - Byron Fabian Pilicita Masabanda

Doctoral candidate:
Byron Fabian Pilicita Masabanda

Title of thesis:
Fluid-rock interaction in the vicinity of felsic and mafic intrusions.

Opponents:
Dr. Agnes G. Reyes, Director and Chief Scientist, Reyes Geosciences Ltd, New Zealand
Dr. Peter Kodera, Professor at the Faculty of Natural Sciences, Comenius University Bratislava, Slovakia

Advisor:
Dr. Enikő Bali, Professor at the Faculty of Earth Sciences, University of Iceland

Other members of the doctoral committee:
Dr. Guðmundur Heiðar Guðfinnsson, Research Associate Professor at the Institute of Earth Sciences, University of Iceland Dr. Guðmundur Ómar Friðleifsson, Retired Geologist, founder and leader of the IDDP project, Iceland
Sigurður Garðar Kristinsson, Manager of Geology, Iceland Geosurvey, Iceland

Chair of Ceremony:
Dr. Andri Stefánsson, prófessor og deildarforseti Jarðvísindadeildar HÍ / Dr. Andri Stefánsson, Professor and Head of the Faculty of Earth Sciences, University of Iceland

Abstract:
This research deals with the thermal and geochemical evolution of the magmatic-hydrothermal transition within the Geitafell Central Volcano (GCV), SE Iceland, to provide critical insights for high-temperature geothermal exploration. By integrating petrography, bulk-rock geochemistry, micro-analytical techniques, and thermal modeling, this study establishes a framework for understanding how intrusions of different sizes drive high-enthalpy systems. The study reveals that geothermal maturation is sustained by a suite of heat sources. Small-scale basaltic dikes (0.5 m thick) generate high-temperature pulses, inducing localized cryptic partial melting (3–10%) and high-grade metamorphism (>800 °C). Although these dikes solidify in less than a day, their thermal impact elevates host-rock temperatures for up to three years; therefore, frequent injections maintain elevated temperatures for several decades. In contrast, the medium-scale (≈782 m thick) Hoffell Granite Intrusion (HGI) functions as a sustained heat engine. The HGI formed via extreme fractional crystallization (>95%), where high magmatic halogen concentrations (F, Cl) depressed its solidus; this extended the cooling process and allowed the HGI to remain a viable heat source for over 7000 years. Analysis of quartz-hosted fluid inclusions within the HGI further tracks the chemical transition from metal-rich, salt-saturated magmatic brines to circulating meteoric fluids. Overall, these findings provide evidence of the geodynamic maturation of the GCV, documenting its transition from a rift-axis to a flank-zone environment. This integrated model provides essential tools for identifying deep heat sources and mitigating technical risks, such as halite scaling and chlorine-active corrosion, when drilling into the deep roots of high-temperature geothermal systems in active volcanic areas.

About the doctoral candidate:
Byron Pilicita M. obtained his B.Sc. in Geological Engineering from the National Polytechnic School (EPN) in Ecuador (2012). After completing his B.Sc., he worked for one year in the mining sector (2013–2014) and four years in the geothermal industry (2014–2018) with national companies in Ecuador. During that period, he completed the six-month Geothermal Training Programme (GRÓ GTP / UNU-GTP) in Iceland in 2016. In 2021, he completed his M.Sc. in Geology at the University of Iceland, where he continued into his Ph.D. programme later that year. Byron's main ambition is to contribute to global climate solutions by actively participating in and advancing the development of the geothermal industry. Byron is the son of Héctor Pilicita and Eva Masabanda, and the oldest of three siblings, with a sister, Michelle, and a brother, Richard. Originally from Ecuador, he resides in Iceland with his wife, Sigrún Jónsdóttir, and their son, Emil Jörundur and proudly serves as a father figure to his sister Michelle's son, Jared Pilicita.