关键词: 流变, 变形机制, 长英质岩石, 影响因素

Abstract: In this paper,we summarized deformation mechanisms of crustal rocks and the progress of the rheological experiments under high temperature and pressure,and discussed the quality of rheological experiment data. Although a great amount of creep test data have been published,the data of natural felsic rock,as well as data of quartz published in early time are hard to be reduplicated. However, the creep data of quartz and feldspar published in recent years are of very high quality. Some studies show that flow laws of two-phase rocks could be fitted using the empirical and theoretical models and rheological parameters of end member minerals. However,the flow laws for felsic rocks are hard to be determined because of complicated components and special rheological properties. As a result,when rheological parameters of felsic rocks are used to estimate the strength profile of the continental crust,the stress envelope and the depth of brittle-plastic transition zone are different even in the same temperature and strain rate condition. Therefore,we suggest more creep experiments should be done in order to obtain high quality rheological data of felsic rocks.
Based on recent progresses in rheological experiment,the influence factors on rheology of felsic rocks in laboratory conditions are discussed,especially,the covering water,mineral component,grain size and fabric of the rock. Little water in the rock would have a significant weakening role on the rheological strength. The effect of the rheological strength of melt is dependent on the observations and the distribution of the melt. If grain boundaries are wetted by melt films,the weakening effect of the melt will become more obvious. The effect of mineral component on rock rheology is reflected not only by stress exponents of samples,but also transition temperature from semi-brittle state to plastic state. The grain size mainly influences the deformation mechanism of rocks. In diffusion regime,the flow stress has negative linear correlation with grain size of fine grain samples,which is not only used to estimate as stress piezometer,but also suitable to determine the rheological strength in the ductile shear zone. However,in dislocation regime,the flow stress is independent of grain size,which is the foundation in estimating the rheological strength of the crust rocks in natural condition using experimental data. Finally,the effect of rock fabric and anisotropy,which is the common phenomenon in the crust,on rheology of experimental samples is very limited,which needs further experimental studies to get more data.

Key words: rheology, deformation mechanism, felsic rocks, influence factors