Abstract:

Serpentine minerals are among the minerals commonly found in the Earth’s subduction zones, and their unique physicochemical properties have a significant impact on subducting geodynamics. Friction experimental studies of serpentine minerals are essential to gain a deep understanding of the frictional sliding stability of serpentine-containing faults in subduction zones as well as explaining the complicated misalignment behavior of faults in subduction zone. Previous laboratory research has produced an abundance of results, and this work addresses two main aspects: the stable states of occurrence and interconversion relationships of serpentine minerals, and the parameters affecting the frictional strength and sliding stability of serpentine minerals. First of all, studies on the stable endowment state of serpentine minerals and the interconversion relationship show that different types of serpentines diaplay different stable phases under different conditions. Chrysotile and lizardite are stable at low temperatures, and the stability fields of both chrysotile and lizardite roughly overlap, but chrysotile is in a substable state. Antigorite is stable at high temperature conditions, such as subduction zone mantle wedges containing high pore fluid pressure conditions, and undergoes a transition from lizardite to antigorite with increasing temperature. Secondly, studies on the factors controlling the frictional strength and sliding stability of serpentine minerals have shown that temperature, pore fluid, and the effective normal stress are all critical factors, for example, an increase in temperature can significantly increase the frictional strength of lizardite and chrysotile. In addition, the friction strength of serpentine minerals shows an obvious pressure dependence, and it was found through previous experimental studies that the friction strength of chrysotile exhibits a high-pressure sensitivity, and that the friction strength of antigorite gradually increases with increasing temperature under low fluid pressure conditions, showing an obvious temperature strengthening phenomenon. In contrast, the change in frictional strength of antigorite with temperature under high-pressure fluid pressure conditions is diametrically opposed to the results of low-pore fluid pressure conditions, which shows a clear temperature weakening phenomenon. Previous studies have also found that antigorite-undergoes a dehydration reaction with increasing temperature under lower fluid pressure conditions, and then exhibits unstable velocity weakening phenomenon, while antigorite exhibits velocity weakening phenomenon under low shear deformation rate under high-pressure fluid conditions. By analyzing the variation of friction-slip stability of antigorite with the shear slip rate can help us to better explain the phenomenon of subduction-zone slow-slip. Overall, experimental studies of the friction of serpentine minerals provide a key experimental basis for a deep understanding of subduction zone geologic processes. The results of these studies are scientifically important for predicting earthquakes and explaining the evolution of the Earth’s internal tectonics and subduction zones, providing strong support for research and practice in the field of geosciences.

Key words: Serpentine, friction coefficient, velocity dependence, frictional stability, slow slip, subduction zone

摘要：

蛇纹石矿物大量存在于俯冲带中, 其独特的物理化学性质会对俯冲带动力学产生显著影响。开展蛇纹石矿物的摩擦实验研究有助于理解俯冲带中含蛇纹石断层的摩擦滑动稳定性及解释俯冲带断层的复杂错动行为。目前, 实验室对于蛇纹石矿物的研究已取得了很多成果。文中基于前人的研究工作, 对以下2个方面进行了综述: 1)蛇纹石矿物的稳定赋存状态及蛇纹石矿物之间的相互转换关系; 2)控制蛇纹石矿物摩擦强度及滑动稳定性的因素, 主要包括温度、 孔隙流体及有效正应力的大小。研究表明, 温度的升高可显著增大纤蛇纹石和利蛇纹石的摩擦强度。但对于叶蛇纹石而言, 在较低的流体压力条件下, 其摩擦强度表现出温度强化特征, 而在较高的流体压力条件下却表现出温度弱化特征。蛇纹石矿物的摩擦强度均表现出显著的压力依赖性, 其中纤蛇纹石的摩擦强度表现出更高的压力敏感性。在俯冲带地幔楔条件下叶蛇纹石可大量赋存。前人研究发现叶蛇纹石在较低的流体压力条件下随着温度升高会发生脱水反应, 进而表现出不稳定的速度弱化现象; 而在高压流体条件下, 叶蛇纹石在低剪切变形速率下会表现出速度弱化现象, 叶蛇纹石的摩擦滑动稳定性随剪切滑移速率的变化能够更好地解释俯冲带慢滑移现象。

关键词: 蛇纹石, 摩擦强度, 摩擦滑动稳定性, 慢滑移, 俯冲带