热水条件下角闪石断层泥的摩擦滑动性质——与斜长石断层泥的对比  

Frictional sliding of hornblende gouge as compared with plagioclase gouge under hydrothermal conditions

作　　者：兰彩云[1] 何昌荣[1] 姚文明[1] 靖晨[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：《地球物理学报》2010年第12期2929-2937,共9页Chinese Journal of Geophysics

基　　金：地震行业科研专项(200708014);地震动力学国家重点实验室(LED2008A03)共同资助

摘　　要：基于速率与状态依赖性摩擦本构关系理论框架,在热水条件下研究了角闪石断层泥的摩擦滑动性质并与闪长岩的另一种主要矿物斜长石的摩擦滑动性质进行了对比.摩擦实验是在三轴实验系统上完成,有效正应力200MPa,孔隙压力30MPa,并将加载速率在1.22μm/s和0.122μm/s之间实施了切换.结果表明角闪石的摩擦系数均值为0.70±0.01,随着温度增加没有系统性的变化,整体低于斜长石的摩擦系数(0.75±0.01);计算与实验表明,角闪石和斜长石的摩擦系数的体积分数加权平均值与闪长岩的摩擦系数基本一致;角闪石在实验温度范围内(100～614℃)显示速率强化(a—b>0),与斜长石在整个温度范围内的速率弱化(a—b<0)正好相反;角闪石的速率依赖性在整个实验温度范围内无系统性的变化.Using a framework of rate and state friction laws, we report and discuss the results of friction experiments performed on hornblende simulated gouge and comparison of frictional sliding of hornblende simulated gouge against plagioclase simulated gouge. Hornblende and plagioclase are two major rock-forming minerals in a diorite sample from the Longmenshan area. We sheared a I-mm-thick gouge layer between saw-cut forcing blocks in a triaxial testing machine under conditions of effective normal stress 200 MPa and pore pressure 30 MPa. Temperature was varied from 100 to 614 ℃. To investigate the velocity dependence of friction we toggled the shear displacement rate between 1.22 and 0. 122 μm/s. Our results show that the hornblende gouge was much weaker than the plagioclase gouge and showed a steady-state friction coefficient μ＇＇ of -0.70 at sliding rate of 1.22 μm/s compared with -0.75 for the latter. The volume-weighted averages of the friction coefficients of plagioclase gouge and hornblende gouge （at 1.5 mm permanent axial displacement） agree well with a limited number of supplementary test results on the friction coefficient of diorite gouge. Hornblende gouge showed velocity strengthening in the whole range of temperature from 100 to 614 ℃, in strong contrast with the velocity-weakening behavior of plagioclase gouge in the same temperature range. These results imply that the hornblende gouge may have an effect of promoting velocity strengthening of diorite gouge whereas plagioclase gouge has the opposite effect. As hornblende gouge has finer grain size and easier to be comminuted, it is speculated here that hornblende powder may fill the gaps between plagioclase grains and may make plagioclase-hornblende mixture like diorite gouge exhibit velocity-strengthening behavior.

关 键 词：闪长岩 角闪石 斜长石 摩擦系数 速率依赖性 

分 类 号：P313[天文地球—固体地球物理学] P584[天文地球—地球物理学]