Experimental Studies on the interaction between crustal deformation and geo-fluids

地壳岩石的流变性主要受孔隙中的H2O流体、晶界中的薄水膜和少量溶解在晶体中的水的影响。为了研究水对地壳形变的影响，我们建立了安装在静冈大学的固体介质形变装置(MK65S)，并建立了在高达1 Gpa和1000度的高压和高温条件下获得高分辨率力学数据的实验技术。用玛瑙和蛇纹石(主要由安山岩组成)的圆柱形样品进行了恒应变率实验。这两个样本都在高温下释放出游离水。玛瑙样品重结晶成石英集合体，表现出稳定的蠕变行为。重结晶石英的c轴组构向压力轴集中，反映了应变能驱动的晶界迁移效应。用傅里叶变换红外光谱仪测量了高PT实验前后样品中水分含量的变化。蛇纹岩的变形实验分别在500℃和700℃的800 Mpa围压下进行，分别低于和高于脱水反应温度。样品由银管和银盘包裹。一些样品在静态条件下在700℃或750℃预热0.5-1小时。蛇纹岩在高温下(700℃)表现出强烈的弱化和蠕变行为，而在低温下(500℃)，即使差应力达到1 GPa时也不会屈服。与脱水反应有关的孔隙的形成和坍塌可能与蛇纹岩的脆韧性转变有关。认为蛇纹岩的脱水作用在双地震带板内地震的触发中起着重要作用。

Rheological properties of crustal rocks are significantly affected by H2O fluids in the pore spaces, thin water films in the grain boundaries, and a small amount of water that dissolved in crystals. In order to investigate the effects of water on crustal deformation, we set up a solid-medium deformation apparatus (MK65S), installed at the the Shizuoka University, and established experimental techniques to obtain high-resolution mechanical data at high-pressure and high-temperature conditions up to 1GPa and 1000 degrees. Constant strain-rate experiments were conducted by used cylindrical samples of agates and serpentinites (mainly composed of antigolite). Both samples release free water at elevated temperatures. Agate samples recrystallized into quartz aggregates and exhibit steady-state creep behaviors. The c-axis fabrics of recrystallized quartz concentrate to the compression axis, suggesting the effects of strain energy-driven grain boundary migration. The change of water contents in the sample before and after high PT experiments was measured by a FTIR microscopy. Deformation experiments of serpentinite were performed at 800MPa confining pressure at 500 C and 700 C, below and over the temperature of dehydration reaction, respectively. The samples were jacketed by Ag tubes and disks. Some samples were pre-heated at 700C or 750C for 0.5-1 hours under static conditions. At high-temperature runs (700C), serpentinite shows drastic weakening and creep behaviors, whereas it does not yield at the low-temperature run (500C), even when differential stress reaches to 1GPa. Formation and collapse of pores associated with dehydration reaction may be responsible to the britte-ductile transition of serpentinites. It is suggested that dehydration of serpentinites plays important roles in triggering intra-slab earthquakes in the double seismic zones.