Evolution of mica fish in mylonitic rocks

摘要: Abstract Mineral fish are lozenge-shaped porphyroclasts, single crystals in a finer grained matrix, which occur ductile shear zones and commonly used as sense indicators. of biotite, tourmaline, K-feldspar, garnet, hypersthene quartz mylonites but most common white mica fish. These can be subdivided into six morphological groups that develop by different mechanisms determined initial shapes orientations. The principal formation intracrystalline deformation combined with rigid body rotation. Concomitant selective grain size reduction occurs recrystallisation, cataclastic separation, pressure solution diffusional mass transfer. Microboudinage has been proposed for the breakdown large smaller ones many undergo shortening rather than extension along their long axes. Evidence is presented an alternative process tips isoclinally folded then break off hinge these microfolds. All fish-shaped porphyroclasts or mineral have specific shape-preferred orientation axis at small antithetic angle respect to foliation. They represent special group objects stable due flow partitioning narrow bands.