Doctoral defence in Geology - Simon Prause
Doctoral candidate: Simon Prause
Dissertation title: Surtsey: Basalt alteration by seawater in a low-temperature geothermal system
Dr. Alessio Langella, Professor at the University of Naples Federico II, Italy
Dr. Benjamin Tutolo, Associate Professor at the University of Calgary, Canada
Advisor: Dr. Tobias Björn Weisenberger
Supervisor: Dr. Andri Stefánsson, Professor and Head of the Faculty of Earth Sciences, University of Iceland.
Also in the doctoral committee: Dr. Barbara Irene Kleine, Postdoc at the Institute of Earth Sciences, University of Iceland
Chair of Ceremony: Dr. Guðfinna Aðalgeirsdóttir, Professor and Vice Head of the Faculty of Earth Sciences, University of Iceland.
The chemical interaction between seawater and basalt at low temperatures (≤150°C) ranks among the more significant factors controlling the composition of seawater and the oceanic crust. However, the time-integrated geochemical and petrographic outcomes of this process remain understudied. This work investigates the effects of time, temperature, crystallinity, and water-rock ratio on seawater-basalt interaction through a combination of petrographic and geochemical analyses of drill-cores obtained in 1979 and 2017 from the volcanic ocean island of Surtsey as well as through geochemical modeling.
The rates of basaltic glass palagonitization and formation of secondary minerals are positively correlated with temperature. Palagonitized glass undergoes maturation from mostly amorphous to increasingly crystalline clay mineral-rich textures. Direction and magnitude of the element flux associated with the different stages of glass alteration are distinct for most elements. Rare earth elements, Hf, Ta, Zr, Nb and Y remain immobile whereas FeO and TiO2 are slightly mobile during palagonite maturation. The entire process of basaltic tuff alteration at Surtsey indicates a net source of dissolved Ca, Al and SiO2 and a net sink of dissolved Mg and Na for seawater.
Geochemical modeling of the alteration process suggests that crystalline and glassy basalts progress through a similar series of reactions, characterized by initial dissolution of glasses and primary minerals, followed by formation of phyllosilicates, oxides, hydroxides, carbonates, sulfates, sulfides and eventually zeolites. Water-rock ratio and pH are identified as the main factors determining the dominant mineral assemblage, whereas temperature and rock crystallinity are less important for the outcome of alteration.
About the doctoral candidate
Simon was born in 1988 in Datteln, Germany. He received a Bachelor’s degree in Geoscience from the University of Muenster, followed by a Master’s degree from the University of Bremen, specializing in petrology, geochemistry, and water-rock interactions. In 2017 Simon moved to Iceland, participating in the ICDP’s Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) expedition for his PhD project. Aside from geology, Simon enjoys cooking, weightlifting, and hiking together with his wife Yingying, with whom he lives in Reykjavik.