Most changes in mineralogy, density, and rheology of the Earth’s lithosphere take place by metamorphism, whereby rocks evolve through interactions between minerals and fluids. These changes are coupled with a large range of geodynamic processes and they have first order effects on the global geochemical cycles of a large number of elements.
A. Håkon Austrheim and Kristina Dunkel conducting fieldwork in the Leka ophiolite Complex, Norway. B. Porosity generation during replacement of ternary magmatic feldspar from a larvikite intrusion by porous albite. BSE image by Oliver Plümper.
In the presence of fluids, metamorphic reactions are fast compared to tectonically induced changes in pressure and temperature. Hence, during fluid-producing metamorphism, rocks evolve through near-equilibrium states. However, much of the Earth’s lower and middle crust, and a significant fraction of the upper mantle do not contain free fluids. These parts of the lithosphere exist in a metastable state and are mechanically strong. When subject to changing temperature and pressure conditions at plate boundaries or elsewhere, these rocks do not react until exposed to externally derived fluids. Metamorphism of such rocks consumes fluids, and takes place far from equilibrium through a complex coupling between fluid migration, chemical reactions, and deformation processes. This disequilibrium metamorphism is characterized by fast reaction rates, dissipation of large amounts of energy as heat and work, generation of a range of dissipative structures which often controls transport properties and thus further reaction progress, and a strong coupling to far-field tectonic stress.
Serpentinization of oceanic lithosphere
This project focus on the effects of tectonic stress on the rate and progress of serpentinization of the oceanic lithosphere. Part of it is funded through the Marie Curie ITN project ABYSS (http://abyss-itn.eu/training) and includes the PhD project of Kristina Dunkel supervised by Bjørn Jamtveit and Håkon Austrheim.
Pore scale controls on reaction driven fracturing
This project focus on how pore scale processes may contribute to and sometimes control the porosity and permeability of rocks undergoing retrograde metamorphism. It involves studies of fluids in narrow confinement, and micrometer to nanometer-scale characterization of reaction produced porosity and permeability (Fig.2). The project includes Bjørn Jamtveit, Håkon Austrheim, Anja Røyne and Oliver Plümper (University of Utrecht) as an external collaborator.
Effects of porosity and tectonic stress on reaction driven fracturing
The project studies reaction driven fracturing by numerical modeling by Discrete Element Methods (DEM). The modeling is applied to phenomena observed during spheroidal weathering and during experimentally produced fluid consuming reactions. It is conducted by Ole Ivar Ulven, Anders Malthe Sørenssen, Håkon Austrheim and Bjørn Jamtveit.
Hövelmann, J., Austrheim, H., and Jamtveit, B., 2012, Microstructure and porosity evolution during experimental carbonation of natural peridotite. Chemical Geology, 334, 254-265
Jamtveit, B., Putnis, C., Malthe-Sørenssen, A., 2009, Reaction induced fracturing during replacement processes, Contributions to Mineralogy and Petrology, 157, 127-133
Jamtveit, B., and Austrheim H., 2010, Metamorphism: The role of fluids. Elements, 6, 153-158
Jamtveit, B., Austrheim, H., and Putnis, A., 2015, Disequilibrium metamorphism of the Earth’s lithosphere and some geodynamic implications. Earth-Science Reviews (submitted)
Plümper, O., Røyne, A., Magraso, A., and Jamtveit, B., 2012, The interface-scale mechanism of reaction-induced fracturing during upper mantle serpentinization. Geology, 40, 1103-1106
Plumper, Oliver; Piazolo, Sandra; Austrheim, Hakon , 2012, Olivine Pseudomorphs after Serpentinized Orthopyroxene Record Transient Oceanic Lithospheric Mantle Dehydration (Leka Ophiolite Complex, Norway) Journal of Petrology, 53, 1943-1968
Røyne, A., and Jamtveit, B., 2015, Pore scale controls on reaction driven fracturing. Reviews in Mineralogy and Geochemistry, 80 (in press)
Ulven, O. I.; Storheim, H.; Austrheim, H.; et al. 2014, Fracture initiation during volume increasing reactions in rocks and applications for CO2 sequestration. Earth and Planetary Science Letters, 389, 132-142
Ulven, O.I., Jamtveit, B., and Malthe-Sørenssen, A., 2014, Reaction driven fracturing of porous rocks. Journal of Geophysical Research, doi: 10.1002/2014JB011102