AN HIGH-TEMPERATURE AND HIGH-PRESSURE EXPERIMENTAL STUDY OF CHANGES BETWEEN BRITTLE AND DUCTILE DEFORMATIONS IN DIABASE
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摘要: 以天然叶腊石为传压介质, 在温度800~100 0℃、围压0.6~1.0 GPa和应变速率10-4~10-5 s-1条件下, 对Maryland辉绿岩的脆性-塑性转化进行了实验研究.实验结果表明, 在10-4~10-5 s-1应变速率和固定围压1.0 GPa条件下, 当温度低于800℃时, 岩石变形为典型脆性破裂; 温度高于1000℃时岩石变形以准稳态蠕变为主; 温度在800~950℃之间, 岩石变形从脆性破裂向准塑性流动转化.温度变化对岩石脆-塑性转化影响敏感度高于压力变化对变形的敏感度.显微构造观察显示, 辉绿岩脆-塑性转化以稀疏弥漫状共轭塑性流动网络为特征.Abstract: A series of experiments on the transfer between the brittle and ductile properties of the Maryland diabase was performed, with natural pyrophyllite as the medium for the pressure transfer, at the temperature ranging from 800 to 1 000 ℃, at the confining pressure ranging from 0.6 GPa to 1.0 GPa, and at the strain rate ranging from 10-4 to 10-5 s-1. The experiment results show that the rock is deformed into typical brittle fractures at the strain rate ranging from 10-4 to 10-5 s-1, at the confining pressure of 1.0 GPa, and at the temperature lower than 800 ℃. At the temperature higher than 1 000 ℃, the rock is deformed dominantly into the metastable creep. At the temperature ranging from 800 to 950 ℃, the deformation of the rock turns from the brittle fractures to the pseudo ductile flow. Therefore, the sensitive effect of the temperature change on the rock transfer between brittle and ductile properties is greater than that of the pressure change. The micro structural observation shows that the transfer between the brittle and ductile properties in the diabase is dominated by the conjugated ductile flow network in the form of the rarefaction and diffusion.
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图 1 实验样品装置结构
1.瓷柱(Al2O3); 2.碳化钨轴压头; 3.围压环(即上电极); 4.实验样品和镍封套; 5.传压介质(叶腊石); 6.碳化钨下压头(即下电极); 7.高压腔壁; 8.炉体金属管; 9.叶腊石绝缘套; 10.保护套(软钢); 11.叶腊石隔离层; 12.热电隅和瓷管
图 3 实验变形岩石的宏观结构
a.平行轴向主压应力方向的张性破裂结构(M-2样品: 800℃, 1 GPa, 1.5×10-4 s-1); b.稀密相间半延性塑性流动网络结构(M-7样品: 950℃, 1.0 GPa, 1.5×10-4 s-1); c.密集共轭塑性流动网络结构(M-1样品: 1000℃, 1.0 GPa, 1.5×10-4 s-1); d.含宽变形条带的准稳态均匀流动结构(M-8样品: 1000℃, 1.0 GPa, 2.0×10-5 s-1).比例尺1∶3
Fig. 3. Macrostructures of deformed samples of diabase
图 4 辉绿岩变形样品的显微构造
斜长石(a) 和单斜辉石(b) 晶内、晶界和穿晶微裂隙(M-2样品, 800℃, 800×); c, d.脆-塑性转化域中斜长石定向排列(M-7, M-8样品, 950℃, c.40×, d.25×); e, f.斜长石均匀塑性变形扭折带(M-1, M-8样品, 1000℃, e.500×, f.100×)
表 1 力学实验结果
Table 1. Mechanical experimental results
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