关键词: 脆延性转化, 脆塑性转化, 石英, 长石, 变形与温度压力条件

Abstract: Brittle-ductile and brittle-plastic transition in rocks are two different concepts. The brittle ductile transition generally refers to a change from localized failure (by macroscopic fracture or faulting) to macroscopic homogeneous flow (by any deformation mechanism, including cataclastic flow, semi-brittle \ semi-plastic flow and plastic flow). This change is often associated with macroscopic texture and mechanical behavior. The brittle-plastic transition means the change from brittle (including fracture or faulting, cataclasis and fraction) to crystal-plastic deformation. With increasing temperature and pressure, the transition undergoes from localized brittle fracture, semi brittle deformation (cataclastic flow or semi-brittle faulting, semi-brittle flow) to homegeneous crystal-plastic flow. This change is assoiated with mechanical behavior and micro-mechanism. Such transitions are important to understanding earthquake source mechanics, the strength of the lithosphere, and the style of deformation. Through comparing experimental T-P condition and natural environment, and their effects on deformation of quartz and feldspar (which are the most important rock-forming minerals in the crust), it is found that the same deformation features in experiment and nature require different temperature and pressure. It is possible to resolve the conflict through setting up deformation mechanism map. In application, the mechanical behaviors and deformation mechanisms should be determined first, then the temperature and pressure are found according to isomechanical group. Unfortunately, the deformation mechanism maps of major crustal rocks are not available because of insufficient experimental data. So, It is a useful way for extrapolating experimental results to geological scales that comparing common deformation character and mechanisms in experimental results and that in nature, looking for the different temperature and pressure from experiment and nature condition, then determining physical mode of deformation by experiments.

Key words: Brittle-ductile transition, Brittle-plastic transition, Quartz, Feldspar, deformation temperature and pressure condition