2D rotation of rigid inclusions in confined bulk simple shear flow: a numerical study     

Fernando O. Marques  Rui M. Taborda  Jos V. Antunes 《Journal of Structural Geology》2005,27(12):2171-2180

We have used incompressible Navier–Stokes in 2D finite element modelling to investigate rigid inclusion rotation under confined bulk simple shear flow. Confinement is defined as the ratio (S) between the channel width (H) and the inclusion's least axis (e₂)(S=H/e₂). The numerical results show that (i) inclusion rotation is strongly influenced by S and, when the confinement is effective, aspect ratio (R) and shape also play an important role. (ii) Back rotation is limited because inclusions reach a stable equilibrium orientation (_se). (iii) There is also an unstable equilibrium orientation (_ue), which defines an antithetic rotation field with _se, and both _se and _ue depend on S, and inclusion R and shape.  相似文献   

Correlating multiple deformation events across the Mesoproterozoic NE Australia using foliation intersection axes (FIA) preserved within porphyroblasts     

Mohammad Sayab   《Gondwana Research》2008,13(3):331-351

Foliation Intersection/Inflection Axes within porphyroblasts (FIAs) allow the chronological and kinematic linking of deformation episodes with associated metamorphism. Measurement of FIAs in the Mesoproterozoic Eastern Fold Belt (EFB) of the Mount Isa Inlier, NE Australia, has revealed phases of deformation and metamorphism that could not previously be distinguished from one another. Both the ‘asymmetry switch’ and ‘FitPitch’ FIA measurement techniques have been applied to key localities of polymetamorphosed and multiply deformed EFB, and they yielded the same result. These independent techniques have revealed (1) E–W trending structures that formed during N–S bulk shortening (D₁) and associated metamorphism (M₁) formed during a period of orogenesis (O₁) and N–S oriented structures that formed during E–W bulk shortening (D₂) and associated metamorphism (M₂) during a period of orogenesis (O₂), and (2) the crustal scale tectonic processes associated with polymetamorphism. Middle to upper amphibolite facies metamorphic conditions occurred during O₁ with crustal thickening followed by near-isothermal decompression leading to low-pressure/high-temperature (LP/HT) conditions with the emplacement of Williams and Naraku Batholiths around 1550 Ma. This was followed by a second period of middle-to upper-amphibolite facies metamorphism, O₂. This history not only correlates better across the EFB, but also with the tectono-metamorphic model recently proposed for the Mesoproterozoic Georgetown Inlier of the north Australian Craton.  相似文献