Disequilibirum metamorphism of stressed lithosphere (DIME)

DIME is an ERC Advanced Grant funded project, focussing on mechano-chemical processes in rocks far from equilibrium, reaching from CO2 sequestration in basalts at the Earth’s surface to the development of shear zones in the lower crust. The Goldschmidt Lab and it's scanning electron microscopy and associated techniques (cathodoluminescence, electron backscatter diffraction) are crucial for this research.

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Especially in the absence of fluids, mineral reactions are often too slow to allow for constant equilibration of a rock to changes in pressure and temperature, so that major parts of the lithosphere are metastable. If fluids infiltrate such rocks and induce their re-equilibration under far-from equilibrium conditions, energy is dissipated in the form of heat and irreversible deformation.

DIME investigates such processes with a variety of petrological, geochemical, and microstructural techniques. Below do you find two examples of electron microscopy applications to such projects:

Example A: When characterizing basalts from the Faroe Islands, North Atlantic Ocean and their potential for CO2 sequestration, frozen-in reactions of one zeolite to another were observed in thinsection (figure A). Zeolites fill vesicles in the basalt and therefore influence its permeability. Their dissolution rates (influenced by their high-surface microstructures) affect later fluid chemistry and carbonation reactions.

Image Ca_zeolite grain_590px. Image: Max Meakins via SEM/Goldschmidt Lab`s Infrastructure
Figure A) Coronas of Na- and Mg-zeolites around a Ca-zeolite grain. Image: Max Meakins (2021), via SEM/Goldschmidt Lab`s Infrastructure.

Reference MScThesis/UiO: Meakins, MWJ. 2021. Understanding offshore flood basalt sequences using onshore analogues with application to permanent CO2 storage: Examples from the Faroe Islands. Permalink: http://urn.nb.no/URN:NBN:no-92044

Example B: When frictional melts produced during earthquakes are quenched to a glass or fine-grained crystals to form a pseudotachylyte, the system is far from equilibrium. One of the effects of strong undercooling is that crystals do not form their thermodynamically preferred shapes, but often become very elongated. Sometimes, those microlites radiate outwards from a common centre to form a spherulite (figure B), in which the orientation of the crystallites changes continuously around the centre.

B) Orientation map for plagioclase in a pseudotachylyte from Lofoten, Norway. Image: DIME via SEM/Goldschmidt Lab`s Infrastructure
Figure B) Orientation map for plagioclase in a pseudotachylyte from Lofoten, Norway. The image is acquired with the electron backscatter diffraction detector at the FE-SEM of the Goldschmidt Lab. Image: DIME via SEM/Goldschmidt Lab`s Infrastructure

Additional information

By The DIME project team
Published Apr. 22, 2022 11:43 AM - Last modified Apr. 22, 2022 12:16 PM
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