地壳岩石变形行为的转变及其温压条件

DEFORMATION BEHAVIOR TRANSITION OF CRUSTAL BOCKS AND ITS TEMPERATURE PRESSURE CONDITIONS

岩石脆延性转化 (brittle ductiletransition)和脆塑性转化 (brittle plastictransition)是不同的概念。脆延性转化指从岩石的局部变形破坏到宏观均匀流动变形的转化 ,它与宏观结构和力学行为的变化相关。脆塑性转化指脆性向晶体塑性变形的转化 ,它与力学行为和微观机制的变化相关。通过地壳中最主要的石英、长石的实验室和野外变形温压条件对比发现 ,达到相同的变形特征 ,在实验室和野外所需温压条件不同。建立变形机制图使解决这一矛盾成为可能。但受实验资料的限制 ,目前几种主要岩石的变形机制图还无法建立。因此 ,通过对实验与自然环境下变形特征及微观机制对比 ,找出两者温压条件的差别 。

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.