Investigating the role of Fe-Ti oxides on the rheology of the oceanic crust

Rudi Osti, Auburn University
Raphaël Gottardi, Auburn University
Jeremy Deans, University of Southern Mississippi
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Abstract

Strain localization processes are pivotal for the understanding of the plates tectonics processes resulting in the development of ductile shear zones that accommodate high proportion of strains at the plates interfaces. Owing their role, they are critical in defining our knowledge of the mechanical characteristics of the lithosphere and their effects on plates interaction. Despite gabbroic rocks being the most abundant lithology in the oceanic and lower continental crust (Dimanov et al., 2007) their rheology remains poorly understood. We aim to study the influence of Fe-Ti oxides (i.e. magnetite and ilmenite) on the mechanical deformation of gabbroic rocks during oceanic lithospheric generation and destruction processes taking place at mid-oceanic ridges and subduction zones. Fe-Ti oxides are known to have diminished mechanical resistance with respect to silicates and crystal-plastic deformation mechanisms are active down to temperature as low as 400°C (e.g. Siemens, 1977). The occurrence of Fe-Ti oxides in gabbroic rock appears to be higher in some oceanic core complexes and the link between OCC, Fe-Ti oxides and ophiolites may be significant as a great number of the latter are thought to have formed at slow spreading rate environments. Some past works (e.g. Natland et al., 2002) have suggested a possible connection between the presence of these phases and the occurrence of crystal-plastic fabric while others have questioned it (e.g. Miranda and John, 2010). We suggest the hypothesis that Fe-Ti oxides exert a weakening mechanism on gabbroic rocks and their distribution may act as a strain localization factor for the rocks of the oceanic and continental lower crust at spreading ridges and collision zones.

Session

Deformation in the upper crust