Heterogeneity in texture and crystal fabric of intensely hydrated ultramylonitic peridotites along a transform fault, Southwest Indian Ridge
نویسندگان
چکیده
Microstructures and olivine crystal fabrics were studied in amphibole-bearing peridotite samples obtained from the Marion Fracture Zone of Southwest Indian Ridge by dredge D19 1984 PROTEA Expedition Leg 5 cruise RV Melville. The peridotites show various textures ranging extremely fine-grained well-layered ultramylonites to heterogeneously strained tectonites. Electron back-scatter diffraction analyses revealed that crystal-preferred orientations (CPOs), which are developed primarily coarse granular mantle, become weaker with an increasing degree grain-size reduction coarser finer grains, for both porphyroclastic matrix grains. However, two characterized bimodal CPOs (010)[001] (B type) (001)[100] (E or a strong maximum [010] normal foliation girdle patterns [100] [001] on plane (i.e., axial pattern AG type). Moreover, spinel grains within these have not only been broken down form amphibole hydrous reactions, but also fractured their fragments pulled apart matrix. These features indicate shear deformation occurred as stress under conditions during final stage deformation, enabled local occurrence low-temperature plastic resulting development CPO ultramylonites.
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ژورنال
عنوان ژورنال: Tectonophysics
سال: 2022
ISSN: ['1879-3266', '0040-1951']
DOI: https://doi.org/10.1016/j.tecto.2021.229206