Abstract In order to understand the friction properties of amphibole as a primary constituent mineral in subduction zones, we used hornblende as the simulated gouge material to conduct two series of shearing experiments at temperatures from 101 to 607 °C under confining pressures of 136 MPa and 83 MPa, a pore pressure of 30 MPa and loading rates of 0.0488–1.22 μm/s. Steady-state friction coefficients in the high confining pressure series exhibited values between 0.70 and 0.72 with an average of ~0.71, without showing a systematic temperature dependence. The counterpart in the low confining pressure series ranged from 0.67 to 0.73 and exhibited a temperature-dependent decline for temperatures above 400 °C. Velocity-weakening behaviors were observed at 303, 505 and 607 °C in the high confining pressure series, and at 303 and 403 °C in the low confining pressure series. The |a-b| parameter associated with velocity weakening of hornblende in our high and low confining pressure experiments are 0.0005–0.0014 and 0.0014–0.0015, respectively. The b values, which represent the evolution effect in friction, were found to increase with increasing temperature, suggesting a thermally-activated process that produced creep at asperity. Ubiquitously precipitated particles in the deformed gouge suggest that dissolution-precipitation creep may be the most likely mechanism associated with the evolution effect and therefore velocity weakening. The very low velocity weakening observed for hornblende (|a-b| ≤ 0.0015) provides a favorable condition for nucleation of slow-slip events to occur in subduction zones over a wider range of effective normal stress.

中文翻译：

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角闪石的摩擦特性及其对俯冲带慢滑事件的影响

摘要 为了解角闪石作为俯冲带主要成分矿物的摩擦特性，以角闪石为模拟凿岩材料，在101~607 °C、136 MPa和83 MPa的围压条件下进行了两组剪切实验。 MPa，孔隙压力为 30 MPa，加载速率为 0.0488–1.22 μm/s。高围压系列中的稳态摩擦系数在 0.70 和 0.72 之间，平均值约为 0.71，没有显示出系统的温度依赖性。低围压系列中的对应物在 0.67 到 0.73 之间，并且在高于 400 °C 的温度下表现出依赖于温度的下降。在高围压系列中，在 303、505 和 607 °C 下观察到速度减弱行为，以及在 303 和 403 °C 下的低围压系列。|ab| 在我们的高和低围压实验中，与角闪石速度减弱相关的参数分别为 0.0005-0.0014 和 0.0014-0.0015。发现代表摩擦演变效应的 b 值随着温度的升高而增加，表明热激活过程会在粗糙处产生蠕变。变形凿中无处不在的沉淀颗粒表明溶解-沉淀蠕变可​​能是与演化效应相关的最可能机制，因此速度减弱。对于角闪石观察到的非常低的速度减弱（|ab| ≤ 0.0015）为在更宽的有效正应力范围内的俯冲带中发生慢滑事件的成核提供了有利条件。