Abstract
Amphibole peridotite samples from Åheim, Norway, were analyzed to understand the deformation mechanism and microstructural evolution of olivine and amphibole through the Scandian Orogeny and subsequent exhumation process. Three Åheim amphibole peridotite samples were selected for detailed microstructural analysis. The Åheim amphibole peridotites exhibit porphyroclastic texture, abundant subgrain boundaries in olivine, and the evidence of localized shear deformation in the tremolite-rich layer. Two different types of olivine lattice preferred orientations (LPOs) were observed: B- and A-type LPOs. Electron backscatter diffraction (EBSD) mapping and transmission electron microscopy (TEM) observations revealed that most subgrain boundaries in olivine consist of dislocations with a (001)[100] slip system. The subgrain boundaries in olivine may have resulted from the deformation of olivine with moderate water content. In addition, TEM observations using a thickness-fringe method showed that the free dislocations of olivine with the (010)[100] slip system were dominant in the peridotites. Our data suggest that the subgrain boundaries and free dislocations in olivine represent a product of later-stage deformation associated with the exhumation process. EBSD mapping of the tremolite-rich layer revealed intracrystalline plasticity in amphibole, which can be interpreted as the activation of the (100)[001] slip system.
Highlights
The relationship between the lattice preferred orientation (LPO) of olivine and the active slip system of dislocations is relatively well understood through theoretical and experimental studies [1,2,3]
The slip systems of olivine identified from the LPOs, subgrain boundaries, and free dislocations represent different deformation conditions and stages
The dominant slip systems of olivine inferred from the LPOs of olivine were (010)[100] for A-type LPO and (010)[001] for B-type LPO
Summary
The relationship between the lattice preferred orientation (LPO) of olivine and the active slip system of dislocations is relatively well understood through theoretical and experimental studies [1,2,3]. Crystal deformation associated with dislocation creep is considered an important mechanism for LPO formation, which is heavily influenced by the easiest slip system [1]. Various theoretical models, such as the Taylor-Bishop-Hill model [4,5] and the self-consistent approach [6,7], have been developed to calculate the formation of LPO by dislocation glide.
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