Rheological Complexity of Mafic Rocks and Effect of Mineral Component on Creep of Rocks

In the rheological experiments for natural mafic samples, there will be semi-brittle deformation under lower temperature, and in contrast, there will appear melts between grain boundaries in the sample under higher temperature, and this could greatly affect rheological behaviors of samples. In the published works, the stress exponent n is mostly reliable, and with high recurrence rate, the activation energy Q is, in some extent, reiterative; however, the coefficient A is poor reiterative. We performed creep tests using 6 kinds of samples with different mineral component. The mechanical data shows that it is more complicated for the effect of mineral component to rheology of rocks than physical models based on flow laws of two phase and polyphase aggregates determined by end-member components. For the sample consisting of plagioclase, clinopyroxene, and hornblende, rheological behaviors are controlled by plagioclase and clinopyroxene when the content of hornblende is less than 10%; however, the role of hornblende could become significant for deformation of samples when the content of hornblende is higher than 10%. For the sample with major mineral of plagioclase, quartz, and hornblende, rheological behaviors are dependent on plagioclase and hornblende when content of quartz is less than 10%, but plagioclase with content near 70% will decide the deformation behaviors of samples. In contrast to that, quartz could completely control the creep of samples when its content is higher than 20%. The most effective method to study rheology of mafic granulite is to perform creep tests using natural gabbro (or diabase) as well as using hot-pressed samples prepared from the major mineral components extracted from mafic granulite.