高温高压及干燥条件下斜长石和辉石断层泥的摩擦滑动研究  

Frictional sliding of pyroxene and plagioclase gouges in gabbro under elevated temperature and dry condition.

作　　者：谭文彬[1] 何昌荣[1] 

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029

出　　处：《地学前缘》2008年第3期279-286,共8页Earth Science Frontiers

基　　金：国家自然科学基金资助项目(40574080)

摘　　要：岩石摩擦滑动的力学行为能够很好地用速率和状态依赖性摩擦本构关系来描述。在速率和状态依赖性本构关系中,速度依赖性参数a-b是控制摩擦滑动稳定性的重要参数。且a-b<0是断层上不稳定滑动成核的必要条件。为了进一步研究控制摩擦滑动的矿物成分因素,在已有辉长岩摩擦滑动实验结果的基础上,对辉长岩中主要矿物(斜长石和辉石)在不同加载条件下进行了3个系列的摩擦滑动实验研究。通过对实验结果的分析得到如下结论:(1)斜长石断层泥在实验温度范围内(<617℃)显示速度强化,且在大于450℃的高温区其速度依赖性参数a-b随温度的增大而增加。辉石断层泥的实验显示其有利于速度弱化滑动行为的出现,是造成辉长岩在615℃出现速度弱化的原因。(2)斜长石与辉石断层泥的摩擦强度都没有随温度的增加而显著变化。辉长岩断层泥的摩擦强度(1.83mm滑动位移处的值)为斜长石与辉石断层泥摩擦强度按体积百分比加权的平均值(摩擦系数精确到2位有效数字一致)。这一结果表明,辉长岩断层泥的应力支承结构可以抽象为一种双组分并列单元模型。(3)尽管前人研究结果表明石英控制了花岗岩的摩擦特性,但是某种主要矿物对岩石整体摩擦滑动性质的控制作用并不具有普适性。对于中性岩、基性岩而言,不能以一种主要矿物(如斜长石等)来判断岩石整体的摩擦滑动稳定性,否则会导致错误结论。The mechanical behavior of frictional sliding of rocks can be described well by rate- and state-dependent friction laws. The ratedependence parameter a--b in the friction laws is important in controlling stability of frictional sliding, and unstable slip nucleates on fault planes for negative rate-dependence of friction （a-b〈0） . On the basis of a previous study on gabbro gouge and focusing on plagioclase and pyroxene, the major mineral constituents of gabbro, we have conducted three series of experiments on frictional sliding of mineral gouges with temperature up to 617℃ and normal stress at or around 300 MPa under different loading conditions in order to explore the effects of different minerals on the frictional sliding behavior. The following conclusions were drawn from the research results. （a） While the plagioclase gouge is favorable for the velocity-strengthening behavior, the pyroxene gouge tends to be favorable for the velocity-weakening behavior, which should be responsible for the velocity-weakening behavior of gabbro gouge at temperature of 615℃. （b） As seen in gabbro gouge, the friction coefficients of the two gouges in this study have no significant variations with the temperature elevation. The volume-weighted average of the friction coefficients of plagioclase gouge and pyroxene gouge （at 1.5 mm permanent axial displacement） agrees accurately with the friction coefficient of gabbro gouge （up to two significant digits）. This fact implies that the stress-bearing structure of the gabbro gouge can be abstracted as a model with two components connected in parallel. （c） Although the quartz proved to be the mineral that controls the sliding behavior of granite under hydrothermal conditions, this may not apply to other rocks in general. For intermediate and mafic rocks, it can be wrong to estimate the sliding stability of a certain rock based on the behavior of only one of its major mineral constituents （plagioclase for example）.

关 键 词：斜长石 辉石 辉长岩 摩擦滑动 稳定性 速度依赖性 

分 类 号：P579[天文地球—矿物学]