Trial Lecture
Title: "The economic importance of alkaline igneous rocks"
Time and place: April 10, 2026, 10:15 AM, Tøyen hovedgård
Public Defence
Adjudication Committee
- Dr. Sam Broom-Fendley, University of Exeter
- Professor Hilary Downes, School of Natural Sciences, Birkbeck University
- Professor Wolfram Michael Kürschner, Department of Geosciences, The Faculty of Mathematics and Natural Sciences, University of Oslo
Chair of the Defence
- Professor Torsten Struck, Natural History Museum, University of Oslo
Supervisors
- Professor Henrik Friis, Natural History Museum, University of Oslo
- Professor Emeritus Tom Andersen, Natural History Museum, University of Oslo and University of Johannesburg
- Dr. William Hutchison, School of Earth and Environmental Sciences, University of St Andrews
Summary
The Larvik Plutonic Complex (LPC) is one of the largest alkaline complexes on Earth. To date, a total of 246 minerals have been found in the LPC and 32 of these have their type locality from the complex. Most of the minerals are found in various nepheline syenite pegmatites hosted in the “larvikite”, a hypersolvus monzonite. The understanding of the relationship between the host rock larvikite and the pegmatites is important as the pegmatites are intraplutonic, meaning they are temporally, spatially and genetically related to its host rock. This thesis investigates the sources and processes that forms the alkaline pegmatites of the LPC, utilizing both radiogenic- and stable isotope geochemistry combined with crystallography and crystal chemistry.
Paper I provides the first lead-lead (Pb-Pb) systematics on single galena minerals from the LPC pegmatites and it is suggested that the Pb is derived from a single crustal source. Paper II presents the first sulfur (S) isotope data on single sulfide minerals from the LPC pegmatites and together with whole rock S-isotope data conducted on the host rock, show that both datasets correlate with a magmatic origin. Paper III investigates S-isotopes in helvine-group minerals from the LPC pegmatites and the results are similar to the S-isotopes from the sulfides. This offers a new way of utilizing isotope systems by expanding its applicability to new mineral groups.
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