粘土矿物的摩擦滑动特性及对断层力学性质的影响

Frictional properties of clay minerals and their effect on fault behavior

粘土矿物在浅部断层带中广泛存在,而其特殊的力学性质会显著影响断层的强度以及断层错动的行为模式.因此在浅部断层地质条件下,针对粘土矿物摩擦滑动特性的研究对于我们解释和预测断层的活动行为有重要意义.本文系统地总结了前人的工作,发现含水条件,以及温度和压力的变化都会影响到粘土矿物的摩擦强度,在自然断层带中断层强度随着粘土含量的增加而系统性的降低,但是粘土矿物在断层带中不同的分布状态会造成显著不同的断层弱化.当断层带岩石中含有少量的粘土矿物时,粘土矿物对断层强度的组构弱化远大于其在断层带中均匀分布时所造成的弱化作用.粘土矿物对于断层滑动的弱化和稳定性作用在断层浅部(<8 km)的温度(<150℃)和压力条件下没有发生明显的变化.在断层带粘土矿物的研究中,相比于粘土矿物在断层岩石中的绝对含量,我们应更多的关注粘土矿物在断层带中分布的组构.

Ubiquitous occurrence of clay minerals has been found in shallow portions of actual fault zones and their unique mechanical properties can significantly weaken fault strength and influence the sliding behavior of fault surfaces, thus frictional properties of clay minerals is crucial in understanding and predicting fault behavior of the shallow portion. Previous works indicate that frictional strength of clay minerals can be affected by hydration state and the pressure and temperature conditions. In natural fault zones, fault strength decreases systematically with content of clay minerals, and if clay minerals form continuous and through-going layers along the fault surface, only a small content of clay minerals in fault rocks can significantly weaken fault strength. At shallow portion of fault zones（〈8 km）, the weakening and stabilizing effects of clay minerals do not change with variation of temperature and pressure. In the future work, more attention should be paid on foliation of clays in fault zones rather than their absolute content in fault rocks.