断层脆塑性转化带的强度与变形机制及其流体和应变速率的影响

野外、实验和地震数据表明:浅部地壳的变形以脆性破裂为主,深部地壳的变形以晶体塑性流动为主.在这种认识的基础上,提出了地壳变形的2种机制模型,即发生脆性变形的上部地壳强度基于Byerlee摩擦定律以及发生塑性变形的下部地壳强度基于幂次蠕变定律.而位于其间的脆塑性转化带的深度与浅源地震深度的下限具有很好的一致性.然而,二元结构的流变模型局限性在于其力学模型过于简单,往往过高估计了脆塑性转化带的强度.问题的根源在于对脆塑性转化带的变形机制的研究已有很多,但没有定量的力学方程来描述脆塑性转化带强度;而且以往对断层脆塑性转化带的研究主要集中在温度引起的脆塑性转化方面,对因应变速率和流体对脆塑性转化的影响方面的研究也比较薄弱.对断层带内矿物变形机制研究表明,某些断层带脆塑性转化发生在相同深度(温度和压力)内,发生脆塑性转化的原因是应变速率的变化,而这种变化被认为与地震周期的同震、震后-间震期蠕变有关,这种变化得到了主震-余震深度分布变化的证实.对断层流体特征分析表明,断层带内可能存在高压流体,这种高压流体会随断裂带的破裂及愈合而周期性变化,在地震孕育及循环中起着关键性作用.高压流体的形成(裂隙愈合)有多种机理,其中,压溶是断层带裂隙愈合的主导机制之一.研究在水作用下的压溶,可以对传统的摩擦-流变二元地壳强度结构及其断层强度进行补充与修正.通过以上分析,认为有必要通过野外变形样品和高温高压实验,深入研究应变速率及流体压力对断层脆塑性转化的影响,同时,通过实验建立压溶蠕变的方程,近似地估计脆塑性转化带的强度.     

龙门山断层脆-塑性转化带流变结构与汶川地震孕震机制

汶川地震发震断层为高角度逆断层,这种断层滑动和发生强震需要断层深部具备特殊的力学条件。发震断层地区地表出露若干韧性剪切带,其中不同类型石英变形具有不同的变形温度。细粒糜棱岩中的石英表现为高温位错蠕变,变形温度为500~700℃;含残斑初糜棱岩中的石英表现为中温位错蠕变,其变形温度为400~500℃;早期石英脉中的石英表现为低温位错蠕变,变形温度为280~400℃;晚期石英脉以碎裂变形为主,其变形温度为150~250℃。石英的这些变形特征显示出断层带经历了多期脆-塑性转化。根据糜棱岩中的重结晶石英的粒度估计的断层塑性流动应力为15~80MPa。石英和长石内的微量水以晶体缺陷水、颗粒边界水和流体包裹体水的形式存在,水含量随岩石的应变增加而升高,变化范围为0.01~0.15wt%。断层脆-塑性转化带内石英含有大量与裂隙愈合相关的次生流体包裹体,其捕获温度为330~350℃,流体压力为70~405MPa,估计的流体压力系数为0.16~0.9,代表强震发生后,断层带内产生的大量微裂隙逐渐愈合过程中的流体特征。在考虑断层带流体压力和应变速率变化条件下,利用石英流变参数建立了从间震期到地震成核阶段断层脆-塑性转化带流变结构和震后快速蠕滑阶段断层脆-塑性转化带流变结构。结果表明,在间震期、地震成核阶段、震后快速滑动阶段,断层强度和脆-塑性转化深度随应变速率和流体压力变化而变化,且脆-塑性转化特征与石英的变形机制、断层速度弱化和强化转化深度、汶川地震震源深度等吻合,显示映秀-北川断层具备摩擦滑动速度弱化和地震成核的基础,而断层带内存在高压流体可能是触发高角度逆断层滑动和汶川地震发生的主要机制。     

基岩区断层黏滑与蠕滑的地质标志 和岩石力学实验证据

文中总结了基岩断层带黏滑与蠕滑的地质标志与岩石力学实验证据,分析了控制黏滑与蠕滑的物理机制。断层带内的矿物组成、矿物变形机制、流体作用和断层带变形方式等是控制黏滑与蠕滑的主要因素。富含黏土矿物的断层泥具有速度强化型摩擦滑动,控制着断层蠕滑,而以方解石、石英、长石及辉石等造岩矿物为主的断层泥在大陆浅源地震的震源深度条件下具备黏滑条件。脆性破裂伴随的扩容过程是断层黏滑的必要条件,而压实、碎裂和塑性剪切变形形成的叶理和小褶皱对应于蠕滑。在流体作用下,压溶使孔隙和微裂隙愈合,有利于断层强度的恢复和断层闭锁,既是断层发生不稳定滑动的根源,也是断层带局部存在高压流体的条件,而在流体作用下的退变质反应与水解反应生成黏土矿物和层状及环状硅酸盐矿物,不仅降低了断层带的强度,还导致断层向蠕滑转变。断层带内均匀分布多个剪切面和较宽的变形带对应于蠕滑,局部化的R剪切及Y剪切、窄变形带和摩擦镜面对应于黏滑。     

地震断层带流体作用的岩石物理和地球化学响应研究综述

断层活动导致断裂带裂隙广泛发育,成为地壳中流体运移与聚集的有利通道和场所.流体在地震过程中具有重要作用.流体与地震破裂带内的岩石相互作用导致其具有与其他完整岩石不同的性质,包括矿物-化学组成、粒度分布及传输性质(渗透率、孔隙度)等.这些特性可以视为流体与地震断层带岩石相互作用的响应.一方面,较高的孔隙流体压力导致断层的有效正应力降低.另一方面,流体会与断层岩发生一系列水-岩反应导致矿物蚀变、分解,生成大量摩擦系数较低的粘土矿物,同时一些不稳定元素可能会随流体发生迁移,导致大量物质流失.在地震周期过程中,伴随着流体运移,断层带的物理性质(渗透性、流体压力等)也随之发生变化.同震快速摩擦生热会导致流体产生热压作用,促进同震滑动.另外,同震破裂导致断层带的渗透性快速上升,较高的流体压力会很快释放.在间震期过程中流体会使破裂趋向于缓慢变形,矿物溶解-沉淀、重结晶及压溶等作用胶结并愈合裂隙,断层强度恢复的同时断层带渗透性逐渐降低,孔隙压力又逐渐积累.研究流体的这些物理化学行为对理解地震成核、同震滑动及震后断层愈合等过程有重要意义.本文介绍了有关流体对断层带物理化学性质的改造及流体的动力学意义等方面的研究进展,总结了流体在地震周期过程中所产生的一系列岩石物理化学效应及其对地震过程的影响.     

断层带流体对断层强度和强震孕育的影响

大量研究表明,流体在断层弱化中起着非常重要的作用.在地壳浅部脆性域,自由水通过流体孔隙压力减小断层有效正压力,从而降低断层摩擦强度;在地壳深部,矿物中的微量结构水弱化岩石流变强度.另外,流体-岩石相互作用等化学过程,如长石水解反应,对断层强度的影响也非常显著.断层深部流体通过物理作用与化学作用影响着岩石的变形机制,从而影响断层力学性质与地震孕育和发生.断层内部流体孔隙压力周期性变化是断层带脆-塑性转化、裂缝张开与愈合等的直接体现,这种变化控制着断层强度与强震周期性发生现象.     

花岗岩非稳态流变实验

脆塑性转化带对于研究岩石圈变形、断层强度和变形机制以及强震的孕育和发生具有重要意义。文中采用汶川地震震源区彭灌杂岩中具有代表性的细粒花岗岩样品,在固体压力介质三轴实验系统上开展了高温高压非稳态流变实验研究。实验设计模拟了汶川地震区地壳10~30km深度的实际温度和压力,温度为190~490℃,压力为250~750MPa,应变速率为5×10^-4s^-1,利用扫描电镜对实验样品进行微观结构观察。实验力学数据、微观结构及变形机制分析表明,在相当于地壳浅部10~15km深处的低温低压条件下,表现为应变强化,样品具有脆性破裂-半脆性流动的变形特征;在相当于地壳15~20km的深度条件下,随着应变量增加,应力趋于稳态,样品具有脆塑性转化特征;在相当于地壳20~30km的深度条件下,样品具有塑性流动特征。当样品处于半脆性域时发生非稳态流变,主要变形机制为碎裂作用,同时激活了动态重结晶作用、位错蠕变等塑性变形机制。样品强度随着深度不断增大,在深度为15~20km时达到极大值,深度为20~30km时强度逐渐减小。因此,花岗岩的强度随深度的变化规律与微观结构及变形机制均表明,在实验温度和压力条件下,花岗岩具有非稳态流变特征,在15~20km深处,龙门山断裂带处于脆塑性转化带,花岗岩强度达到最大值,该深度与汶川地震的成核深度一致,显示出彭灌杂岩的强度和变形对汶川地震的孕育和发生具有控制作用。     

断层三维扩展过程的实验研究

实验研究三维断层的形成和扩展对于理解实际断层作用过程具有重要意义．在双轴压缩条件下开展了断层三维扩展过程的实验研究,利用多通道数字化高密度应变观测和基于可见光图像分析的数字散斑相关测量技术对岩石样品应变场的详细结构进行了动态观测和分析,同时利用多通道声发射全波形三维定位系统对样品内部微破裂的发育过程进行了观测．实验结果表明,断层在三维空间的扩展模式与二维明显不同,表现出更复杂的空间展布形态和变形机制．断层的三维扩展过程可以划分为3个基本阶段：第一裂纹扩展阶段——翼裂纹扩展阶段、转换阶段——花瓣裂纹活动阶段和第二裂纹扩展阶段——贝壳断面形成阶段．不同阶段具有不同的主导裂纹扩展方式,并对应不同的变形场和微破裂分布．其中,花瓣裂纹活动阶段在三维断层的发育过程中至关紧要,它是从表面似二维扩展向三维扩展转换的关键,也是三维断层扩展区别于二维断层的核心所在。     

砂岩变形方式和变形机制的实验研究

在温度为200°—700℃,围压为200—700MPa,恒定应变速率(1×10~(-4)/s)条件下,笔者对长石砂岩和石英砂岩完整的和带预切口的试样进行了变形实验。应力-应变曲线表明,完整砂岩发生了脆性的、脆延性过渡状态的和延性的变形;而带预切口的砂岩在整个实验条件下都发生了稳定摩擦滑动。显微观测表明,岩石变形的主要机制是晶内和穿晶微裂隙的产生和发展。根据实验结果笔者推测,砂岩组成的地壳在地下10km左右的深度有最大破坏强度和摩擦强度;而发育在岩石中的断层的活动一般以稳定摩擦滑动为主。     

珠江三角洲地区断层构造岩三维微观结构特征初步研究

岩石内部成分和结构反映其形成过程的环境条件。本文利用高分辨率X射线微观层析成像（微观CT）技术，对珠江三角洲地区断层构造岩（以断层角砾岩、碎裂岩为主）进行三维成像观测和定量分析，尝试从微观角度给出该地区断裂活动特征的解释。研究珠三角地区8个断层构造岩的样品，除一个样品中仅以孔隙状态呈现外，样品中均可见明显裂隙；样品孔隙度范围在1.4%到13.4%；大量样品中可见代表高密度矿物成分的白色影像，其体积占比范围从0.7%到15.6%；裂隙和白色影像具有很好的相关性。对裂缝大小、延伸方向和延伸尺度等参数进行定量分析，并提取了裂隙体积和裂隙长度的分形维数。样品内部，不同尺度的微裂隙的优势方向具有很好的一致性；定向样品还表明，微米CT样品中裂缝的优势方位与宏观断裂的主要活动方位具有一致性。背散射电子成像及能谱分析表明，断层角砾岩的基质以石英为主，白色影像为铁氧化物，可能是流体在孔隙、裂隙中流动所逐步沉淀形成。断层角砾岩的微观结构显示其形成的力学属性为拉张环境，至少经历了岩石破碎、流水作用形成含铁矿物沉淀、胶结，以及后期的进一步破碎三个发展阶段。      

花岗质岩石在脆塑性转化域的变形机制

地震精定位结果显示,大陆地震多数集中于大陆地壳的多震层内,该多震层向下收敛于中部地壳的脆塑性转化带。地壳脆塑性转化带的主要成分为花岗质岩石,前人通常用石英-斜长石的组合代替花岗岩进行变形研究,反演转化带的深度和变形特征,并且认为花岗岩的变形强度由弱项矿物——石英的塑性变形控制。近年来,实验和野外研究均表明钾长石的变形强度高于石英和斜长石。大应变量变形实验和野外韧性剪切带的研究结果显示,在中地壳脆塑性转化带内,钾长石变形以脆性破裂为主,斜长石和石英通常表现为动态重结晶。因此,用石英和斜长石的组合体代替花岗岩来反演断层的变形特征,无法全面、真实地解释断层深部脆塑性转化带的变形特征。文中总结了花岗岩在野外和实验变形条件下的研究结果,并分析了花岗岩的主要组成矿物——石英、斜长石和钾长石的变形特征以及其温压条件的不同步性,讨论了断层深部脆塑性转化带的失稳条件。     

高温高压下红河断裂带断层泥力学性质的研究

断层泥在室温高压下的应力-应变曲线呈非线性、线性等阶段性变形,在高温高压下则呈非线性变形,两者均表现出渐进破坏。含水量、矿物成分和温压条件对变形特征和破坏强度有重要影响。曲线的初始弹性模量小于有效弹性模量。断层泥在温度T≥400℃和σ_3≥300MPa时发生岩化,据此岩化温压条件可估计出未岩化断层泥存在深度将不超过10—15km。由于断层泥具渐进破坏特征,故在高温高压条件下断层泥有利于断层活动呈现稳滑     

DEFORMATION OF THE BRITTLE-PLASTIC TRANSITION ZONE AT THE POST-SEISMIC RELAXATION PERIOD: A CASE STUDY OF THE RED RIVER FAULT

The transition from microscopic brittle deformation to microscopic plastic deformation is called brittle-plastic transition, which is considered as a key layer for determining the limit of lower continental crust seismicity. The depth and deformation mechanism of the brittle-plastic transition zone is controlled mainly by temperature. Besides, the strain rate and fluid pore pressure also affect the transition during the different deformation stages at the seismic cycle. In this paper, microstructure observation of catalcastic samples collected from the Red River Fault was carried out using optical polarized microscopy and scanning electron microscopy. The morphology, microstructures of deformation characteristics, mineral composition, water-rock reaction, pressure solution, exsolution, crack healing in the samples were systematically observed. The mineral components quantitative analyses were examined using the EDS. Water-rock reaction and pressure solution were systematically observed under SEM. The fabric of the main minerals in the samples was measured using electron backscattered diffraction(EBSD). Based on these analyses, the deformation mode was setup for the brittle-plastic transition zone of the fault during the post-seismic relaxation period. Both brittle deformation and plastic deformation were developed in the cataclastic samples. EBSD data shows that the c axial fabrics of quartz present low-temperature plastic deformation characteristics. The feldspar deformed as cataclastic rock, and the micro-fracture in feldspar was healed by static recrystallized quartz and calcite veins. The calcite vein underwent plastic deformation, which represents the post-seismic relaxation deformation. Based on the analysis of deformation mechanism of cataclastic samples in brittle-plastic transition zone of the Red River Fault, and combined with previous studies, we concluded that the brittle fracture and fracture healing is the main deformation mode at brittle-plastic transition zone in the post-seismic relaxation. High stress and high strain rate at post-seismic relaxation lead to brittle fracture of high-strength minerals such as feldspar in rocks. Plastic deformation occurs in low-strength minerals such as quartz and mica. Under the fluid condition, micro-fractures were healed by quartz and calcite. The minerals such as quartz and calcite in the fracture transformed from static recrystallization to dynamic recrystallization with stress gradually accumulating. With fracture healing and stress accumulation, the fault strength gradually increases which could accumulate energy for the next earthquake.     

Relation of deformation behavior with precipitation and groundwater of the Babaoshan fault in Beijing

Introduction The surface of the Earth is the main location where the fluid strongly interacts with solid, and where the atmosphere, hydrosphere, biosphere, and lithosphere strongly interact. Obviously, fault zones as the channels of fluid (water) flow are the focus area of this strong interaction. Earth-quakes, as the products of tectonic activity, occurred near or on the fault zones, can be regarded as one of the results of this strong interaction. Bolt (1999) pointed out that if there were …     

龙门山断裂带金河磷矿剖面断层泥的低速至高速摩擦性质研究

本文对龙门山断裂带金河磷矿浅钻岩芯中的三种断层泥开展了低速到高速摩擦滑动的实验研究,并对实验变形样品开展了BET比表面积研究.摩擦实验在干燥和孔隙水压条件下开展,速率范围涵盖20 μm·s^-1~1.4 m·s^-1.实验结果显示,三种断层泥在干燥条件下的摩擦性质差别不大,但在孔隙水压条件下,三者的中低速摩擦强度与层状硅酸盐矿物的种类而非总含量紧密相关,蒙脱石和伊利石相比绿泥石更能有效地弱化断层.三种断层泥在孔隙水压条件下存在中低速率域的速度强化,暗示着对断层的加速滑动存在一定的阻碍作用.孔隙水压下,黄绿色和灰绿色断层泥的初始动态弱化非常迅速并伴随断层泥层的瞬时扩容,凹凸体急剧加热导致的局部热压作用可能是造成这种力学行为的物理机制.在经历高速滑动之后,三种断层泥在干、湿条件下的BET比表面积都显著降低,暗示着可能发生了颗粒烧结.中低速域内,孔隙水的存在使得断层泥呈现分散式的剪切变形,BET比表面积的增加因此比干燥条件下更加明显.对表面能的估算表明,颗粒磨碎所消耗的能量至多不超过摩擦力做功的8%,暗示着断层作用中颗粒磨碎所占的能量比例较低.     

流体对石灰岩断层摩擦滑动影响的实验研究

在气体介质三轴高温岩石力学实验仪器上,采用意大利Scaglia Bianca石灰岩,在温度50～300℃、围压150MPa,含50MPa孔隙压、无孔隙压含饱和水和完全干燥三种条件下,开展摩擦滑动实验.实验力学数据和显微结构表明,完全干燥样品在120℃时出现慢滑移,实验样品中没有出现溶解与沉淀.无孔隙压含饱和水条件下,100℃、120℃、150℃条件下出现典型的慢滑移,实验样品中含有微弱的溶解与沉淀;300℃条件下出现黏滑,实验样品中出现沉淀.在含50MPa孔隙压条件下,50℃时的实验表现为典型的稳滑,实验样品中以溶解为主;在100～150℃时,出现慢滑移,实验样品中以溶解为主,沉淀为辅;在200～300℃时,出现典型黏滑,实验样品中以沉淀为主.实验结果表明,石灰岩断层泥摩擦滑动稳定性随温度变化,受流体中碳酸钙的溶解和沉淀作用控制,因此,流体中矿物质的饱和度这一化学性质对断层带的摩擦强度和摩擦滑动稳定性具有显著影响.     

Modelling the stress-strain behaviour of saturated rocks undergoing triaxial deformation using complex electrical conductivity measurements

Measurement of complex electrical conductivity as a function of frequency is an extremely sensitive probe for changes in pore and crack volume, crack connectivity, and crack surface topography. Such measurements have been made as a function of pore fluid chemistry, hydrostatic confining pressure, as well as uniaxial and triaxial deformation. This paper will; (1) describe the effects of triaxial deformation on the complex electrical conductivity of saturated porous rocks, (2) use the electrical data to model the mechanical stress-strain behaviour, and (3) compare the modelled behaviour with the stress-strain behaviour measured during the deformation. Experimental conductivity data tracks how the rock undergoes compaction with progressive loss of crack volume, followed by dilatation due to new crack formation, growth of existing cracks, crack interlinkage, and finally failure, as axial strain is increased. We have used the complex electrical data to produce a direction-sensitive (anisotropic) crack damage parameter, and used it to calculate the effective Young's modulus by employing the models of Walsh and Bruner. Comparison of the synthetic stress-strain curves so produced, with the experimentally derived stress-strain curves shows good agreement, particularly for undrained tests. This modelling is an improvement on similar curves produced using isotropic crack damage parameters derived from acoustic emission data. The improvement is likely to be due to the directional sensitivity of the electrical conductivity measurement, and its ability to discriminate between the formation of isolated cracks, and those cracks that contribute to the inter-connected crack space i.e. those cracks upon which transport properties of the rock such as electrical conductivity, and mechanical properties depend most critically during triaxial deformation.     

八宝山断层的变形行为与降雨及地下水的关系

利用北京丰台大灰厂观测台站1970——2003年的长期综合观测资料,系统分析了降雨和地下水对北京八宝山断层变形行为的影响. 研究结果表明:当降雨量持续稳定周期性变化,则断层孔隙压也呈稳定周期性变化,断层变形行为也表现出明显的规则周期性变化;当降雨量明显偏低或偏离正常周期性变化,则断层孔隙压周期性消失,断层的变形行为方式也发生改变. 降雨通过改变断层带孔隙压力的变化而影响着八宝山断层的变形行为. 结合该断层已有研究结果,认为降雨和地下水有可能通过改变断层变形行为方式而影响着区域构造应力/应变场的调整. 这一结果将对研究地球浅部流体与固体相互作用提供直接的观测证据.      

EXPERIMENTAL STUDY ON THE EFFECT OF WATER ON THE STRENGTH AND DEFORMATION MECHANISM OF CARRARA MARBLE AT HIGH TEMPERATURE

We performed deformation experiments using Carrara marble in dry and wet conditions under temperature of 400~700℃ and confining pressure 300MPa with two different strain rates. Water contents of deformed samples were measured using FTIR spectroscopy. The microstructure and deformation mechanisms of samples were observed under optical microscopy, scanning electron microscopy and energy spectroscopy analysis. The mechanical data show that samples display strain hardening at 400℃, and transition to steady creep at temperature from 500~700℃. The strength of marble reduced gradually with elevated temperatures or decreased strain rate. However, water effect to the strength of the marble is significantly weak. Microstructures observed show that the deformation is cataclastic flow in dry samples, fracture and pressure solution in wet samples at 400℃. Samples underwent brittle-plastic transition at 500℃. Dislocation glide is major deformation mechanism for dry samples at 600℃. Dislocation climb and dynamic recrystallization are major deformation mechanism for wet samples at 600℃ and for all wet samples and dry samples at 700℃. Lower strain rate and higher water content could promote the process of pressure solution and diffusion as well as dynamic recrystallization.     

DEFORMATION MECHANISM OF GRANITIC ROCKS IN BRITTLE-PLASTIC TRANSITION ZONE

Field studies and seismic data show that semi-brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so-called frictional-plastic transition. As the bottom of seismogenic fault, the dynamic characteristics of the frictional-plastic transition zone and plastic zone are very important for the seismogenic fault during seismic cycles. Granite is the major composition of the crust in the brittle-plastic transition zone. Compared to calcite, quartz, plagioclase, pyroxene and olivine, the rheologic data of K-feldspar is scarce. Previous deformation studies of granite performed on a quartz-plagioclase aggregate revealed that the deformation strength of granite was similar with quartz. In the brittle-plastic transition zone, the deformation characteristics of granite are very complex, temperature of brittle-plastic transition of quartz is much lower than that of feldspar under both natural deformation condition and lab deformation condition. In the mylonite deformed under the middle crust deformation condition, quartz grains are elongated or fine-grained via dislocation creep, dynamic recrystallization and superplastic flow, plagioclase grains are fine-grained by bugling recrystallization, K-feldspar are fine-grained by micro-fractures. Recently, both field and experimental studies presented that the strength of K-feldspar is much higher than that of quartz and plagioclase. The same deformation mechanism of K-feldspar and plagioclase occurred under different temperature and pressure conditions, these conditions of K-feldspar are higher than plagioclase. The strength of granite is similar to feldspar while it contains a high content of K-feldspar. High shear strain experiment studies reveal that granite is deformed by local ductile shear zones in the brittle-plastic transition zone. In the ductile shear zone, K-feldspar is brittle fractured, plagioclase are bugling and sub-grain rotation re-crystallized, and quartz grains are plastic elongated. These local shear zones are altered to local slip-zones with strain increasing. Abundances of K-feldspar, plagioclase and mica are higher in the slip-zones than that in other portions of the samples (K-feldspar is the highest), and abundance of quartz is decreased. Amorphous material is easily formed by shear strain acting on brittle fine-grained K-feldspar and re-crystallized mica and plagioclase. Ductile shear zone is the major deformation mechanism of fault zones in the brittle-plastic transition zone. There is a model of a fault failed by bearing constant shear strain in the transition zone:local shear zones are formed along the fractured K-feldspar grains; plagioclase and quartz are fine-grained by recrystallization, K-feldspar is crushed into fine grains, these small grains and mica grains partially change to amorphous material, local slip-zones are generated by these small grains and the amorphous materials; then, the fault should be failed via two ways, 1)the local slip-zones contact to a throughout slip-zone in the center of the fault zone, the fault is failed along this slip-zone, and 2)the local slip-zones lead to bigger mineral grains that are in contact with each other, stress is concentrated between these big grains, the fault is failed by these big grains that are fractured. Thus, the real deformation character of the granite can't be revealed by studies performing on a quartz-plagioclase aggregate. This paper reports the different deformation characters between K-feldspar, plagioclase and quartz under the same pressure and temperature condition based on previous studies. Then, we discuss a mode of instability of a fault zone in the brittle-plastic transition zone. It is still unclear that how many contents of weak mineral phase(or strong mineral phase)will control the strength of a three-mineral-phase granite. Rheological character of K-feldspar is very important for study of the deformation characteristic of the granitic rocks.