My field of research is high-pressure and high-temperature (HPT) metamorphic terranes that have formed in the deep interiors of continental collision zones. HPT metamorphic rocks are prime recorders of the Earth’s crustal history and of processes acting at deep levels in tectonic zones. They are therefore of utmost importance for our understanding of large-scale tectonics, and of crustal reworking at depth. My research combines field geology, metamorphic petrology, and geochronology (i.e., metamorphic geology in its broad sense), with emphasis on structural control and analysis of carefully selected samples.
My present research focuses on two field areas in which we have excellent structural and petrological control from many years of research: The Eastern Segment of the Sveconorwegian orogen, southwest Sweden, and the Roan area, Vestranden, western Norway. This work is performed in collaboration with colleagues at different universities and at the Geological Surveys of Sweden and Norway, and PhD and MSc students at the Department of Geology at Lund University.
Roan, Vestranden, western Norway
The Roan area is situated in the westernmost Scandinavian Caledonides, in Vestranden, a region that is the northern equivalent of the world-famous eclogite-bearing Western Gneiss Region (WGR). The Scandinavian Caledonides was formed during continental collision and mountain-building c. 400 Ma ago; the WGR and Vestranden represent the deepest buried portions of the continental crust. The metamorphic geology of the Roan area was the topic of my PhD thesis (1984–1990). Vestranden was at that time a “white spot” on the geological and petrological maps, and in addition to my thesis work I took part in NGU’s bedrock mapping of the area. In our present research, we use new petrological and geochronological analytical methods and apply these tools to key samples, in particular high-pressure rocks. High-pressure rocks in Roan include a.o. kyanite-eclogite, garnet peridotite, and kyanite-garnet gneiss. These metamorphic rocks keep important records of the formation of the Caledonian mountain chain and of processes related to deep burial of continental crust.
The Eastern Segment, southwest Sweden
The Eastern Segment represents continental crust at the margin of the Baltic Shield that was deeply tectonically buried during continental collision c. 1000 Ma ago. The westernmost area exposes the deepest parts with eclogite- and high-pressure granulite-facies rocks. My research up until 2002 focused on the petrology and geochronology of eclogites and other high-grade rocks in the area. Thereafter, during work at the Geological Survey of Sweden in 2003–2009, I took part in (the first) regional bedrock mapping across the southern Eastern Segment. During 2009–2012 targeted and detailed structural field work led to the outline of the regional structure, showing that the eclogites are contained within a 50 km large recumbent fold (folded thrust sheet or fold nappe). Detailed petrology, performed by my PhD student Lorraine Tual, constrained a P–T path peaking at c. 18 kbar (corresponding to 65 km depth) and 870 ºC. My recent work documents the successive increase of metamorphic P and T across the Eastern Segment, from east to west. The Eastern Segment is important not only because of its (globally rare) presence of Precambrian eclogite, but also because it is an extremely rare (the only?) coherent exposure of an “India style” underthrusting lower continental plate. The Eastern Segment offers a unique opportunity to study geological processes systematically across a 200 km wide belt of gradually increasing pressures and temperatures up to >800 ºC and 10–11 kbar (corresponding to 40 km depth).
Science for the general public
In 2010 I published a book, directed towards the public and richly illustrated by photographs, that weaves together geology, art, handicraft, and history in southwesternmost Sweden: "Sten och människor–Den halländska gnejsen (Makadam publishing company).
Currently I am working on an exhibition for Roan kommune on the geology and the fantastic metamorphic rocks of the Roan area.
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