Abstract

Studies of the sulphide–magnetite fabric at Golden Grove. Western Australia, metamorphosed under conditions of lower to middle greenschist facies, indicate that pyrite and magnetite deformed in a brittle manner, whereas pyrrhotite, sphalerite, chalcopyrite, and galena deformed as ductile sulphides. In the accompanying silicate assemblage, pressure-solution deformation has been a significant deformation mechanism. An optical-microscope study of etched sphalerite reveals a wide range of microstructures indicative of ductile deformation, including lattice dislocations, subgrains and subboundaries, annealing twins, variable grain-boundary geometry, and recrystallization. The microstructures are distributed randomly through the sphalerite fabric and are similar to that formed during steady-state creep of deformed metals and that reported in dynamic recovery and recrystallization of deformed quartz. It is concluded that the ductile sulphides are modified by synkinematic recovery and recrystallization and that postkinematic recovery, annealing, and recrystallization, which are commonly reported for sulphide deposits, are not present.

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