Differential stress control on the growth and orientation of flame perthite: A palaeostress-direction indicator

摘要: Abstract Albite flames result from the replacement of K-feldspar by albite through alkali exchange. In flame perthites deformed granites within Grenville Front Tectonic Zone, is driven retrograde breakdown plagioclase and hydration K-feldspar. Within strain fabric host rock, preferentially form subparallel to inferred maximum compression direction also develop at high-stress points such as grain-to-grain contacts. Flame tips are generally parallel ‘normal’ perthite crystallographic i.e. Murchison plane, which orientation plane minimum lattice misfit between We propose that morphology an controlled coherent propagation its tip into crystal lattice, with respect rock differential stress imposed during metamorphism. This type requires dry conditions in there would be inefficient dissolution-reprecipitation along completely incoherent interfaces (normal replacement), increased strength feldspar. Under these coherency maintained avoid a very large kinetic barrier. The differences either high elastic energy (if fit coherent), or dislocation semi-coherent). Such might expected inhibit growth lamellae However, reduces direction. results (1) increase Helmholtz free K-feldspar, (2) reduction semi-coherent interface. Thus, allows decrease net without destruction alumino-silicate framework therefore favoured under stress. Since not has potential palaeostress-direction indicator.