Deformation of upper mantle rocks with contrasting initial fabrics in axial extension
نویسندگان
چکیده
To explore the role of olivine grain size and crystal preferred orientation (CPO), on evolution microstructure mechanical behavior upper mantle rocks up to large strains, we performed axial extension experiments at 1200 °C, 300 MPa confining pressure, constant displacement rate leading strain rates ~10?5 s?1 three natural peridotites: a fine-grained mylonitic harzburgite with weak CPO two coarse-grained well-equilibrated dunites variable intensity. Despite contrasting initial microstructures, flow stresses show limited range variation (115–165 ± 5 MPa), displaying highest strength. However, both differs markedly between fine peridotites. In harzburgite, necking is associated decrease in apparent differential stress. Focusing stress resulted increase intensity recrystallized fraction neck. Analysis final neck indicates softening response CPO. contrast, dunite samples either weaker or no This implies hardening, consistently (1) bulk intragranular misorientation increasing observed these (2) similar higher than ones. All displayed highly heterogeneous deformation. Crystals well oriented deform by dislocation glide became elongated developed marked undulose extinction, whereas crystals hard orientations remained almost undeformed. neck, concentration (local strains attained 365 15 240%, respectively) formation kinks “hard” crystals, dynamic recrystallization “soft” and, where overcame development extensional fractures. We interpret more effective strain-induced peridotite as due easier recrystallization, probably proportion boundaries acting nucleation sites.
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ژورنال
عنوان ژورنال: Tectonophysics
سال: 2021
ISSN: ['1879-3266', '0040-1951']
DOI: https://doi.org/10.1016/j.tecto.2021.228997