Deformation Mechanisms Of Hornblende Under Experimental High Temperature And Pressure

Hornblende is one of the seven most common rock-forming minerals (calcium, biotite, dolomite, feldspar, muscovite, olivine, pyroxene, quartz and hornblende), the deformation mechanisms of which play a very important role by way of understanding the rheological features and properties of the oceanic crust, the middle and lower continental crust. As a biaxial crystal enhydrite, hornblende tends to get its composition altered and metamorphosed. Thus, comparing to the other six common rock-forming minerals, the mechanisms of hornblende challenge the studies coming on its way for a long time. So far, there is no thorough study of the natural deformations of hornblende. With the understanding of the former studies, hornblende is taken as the research object and is experimented under high temperature and high pressure. Analysis on the features of the deformed hornblende is conducted to provide possible explanation on the mechanisms of brittle-ductile transformation and dynamicrecrystallization.As strain rate plays the most important role in natural-deformed rocks, temperature is the most important factor in rock’s experimental deformation. The deformation’s approaching towards ductility can be achieved by increasing confining pressure and/or decreasing the strain rate.Experimentally deformed hornblende starts to show ductile features as wavy extinctions and kinks under the temperature of500-600℃, mass wavy extinctions and recrystallized grains formed by dynamicrecrystallization under the temperature of600-700℃, and dominated ductile deformation under the temperature of700-800℃. Under the temperature condition of500℃---600℃---700℃---800℃, experimentally deformed hornblende shows brittle---brittle-ductile behaviors.