| 组构对花岗片麻岩高温流变影响的实验研究 |
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| 引用本文： | 刘贵,周永胜,姚文明,刘俊来,何昌荣,张媛媛.组构对花岗片麻岩高温流变影响的实验研究[J].地球物理学报,2013,56(7):2332-2347. |
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| 作者姓名： | 刘贵 周永胜 姚文明 刘俊来 何昌荣 张媛媛 |
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| 作者单位： | 1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029;
2. 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083;
3. 陕西省地震局监测中心, 西安 710068 |
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| 基金项目： | 国家自然科学基金项目(90814006、40972146);地震动力学国家重点实验室自主课题(LED2009A01)资助 |
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| 摘 要： | 深部岩石先存的变形组构对流变特性影响的实验研究是新的研究热点之一,然而目前相关的实验研究非常有限.本文利用3 GPa固体介质熔融盐三轴高温高压容器,选择华北克拉通北部辽东拆离断层带中具有变形组构的花岗片麻岩样品,在温度600~840℃、围压800~1200 MPa、应变速率1×10-4~2.5×10-6/S条件下,对不同组构方向的样品(实验压缩方向分别垂直和平行花岗片麻岩的面理)开展高温高压流变实验.实验结果表明,在相同的应变速率和温度条件下,垂直面理的岩石强度比平行面理的岩石强度要高.两组实验样品在600~700℃时,应力指数平均值为6.5,为半脆性流变;在800~840℃时,应力指数平均值为2,垂直面理样品的激活能为Q=380 kJ/mol,平行面理样品的激活能为Q=246.4 kJ/mol,以塑性变形为主,局部存在黑云母和角闪石的脱水熔融.微观结构研究表明,垂直面理的样品,在变形过程中形成了新的变形条带,把原有的面理破坏改造;而平行面理的样品,在实验变形过程中新的变形带主体继承了原有组构.EBSD分析显示花岗片麻岩原岩中石英轴极密区位于Z轴附近,为底面滑移;压缩方向垂直面理的样品,石英组构轴极密区位于X轴附近,为柱面滑移;压缩方向平行面理的样品,石英组构轴极密区位于Z轴附近,伴有少量的Y轴极密,底面滑移和柱面滑移.这表明垂直面理的样品中石英变形改造比平行面理的样品更彻底,这与微观结构分析结果一致.显然实验样品的非均匀组构对样品强度和石英轴定向等具有显著影响,但对样品的脆塑性转化和塑性变形机制没有实质影响,这对理解地壳深部普遍存在的形态各向异性岩石流变具有重要参考价值.
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| 关 键 词： | 组构 流变 微观结构 高温高压 |
| 收稿时间： | 2012-09-11 |
Experimental study on the effect of pre-existing fabric to deformation of granitic gneiss under high temperature and pressure |
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| LIU Gui,ZHOU Yong-Sheng,YAO Wen-Ming,LIU Jun-Lai,HE Chang-Rong,ZHANG Yuan-Yuan.Experimental study on the effect of pre-existing fabric to deformation of granitic gneiss under high temperature and pressure[J].Chinese Journal of Geophysics,2013,56(7):2332-2347. |
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| Authors: | LIU Gui ZHOU Yong-Sheng YAO Wen-Ming LIU Jun-Lai HE Chang-Rong ZHANG Yuan-Yuan |
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| Institution: | 1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;
3. Shaanxi Earthquake Administration, Xi'an 710068, China |
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| Abstract: | The experimental study on the effect of pre-existing fabric on the rheological properties of rocks is a new research focus. The related experimental studies are very limited. In this paper, deformation experiments on natural granitic gneiss from a detachment fault of eastern Liaoning in the North China Craton were carried out in a Griggs-type molten salt medium triaxial apparatus at temperatures of 600~840℃, confining pressure of 800~1200 MPa and strain rate of 1×10-4~2.5×10-6/S. To investigate the effect of pre-existing fabric to rheology of rocks, samples were drilled from natural granitic gneiss with the cylinder axis parallel to the foliation and normal to the foliation. The experimental results show that the flow strength of samples with compression direction perpendicular (PER) to the foliation is stronger than that of samples with compression direction parallel (PAR) to the foliation. In temperature range of 600~700℃, the deformation is accommodated by semi-brittle flow, with the average of stress exponent n=6.5. In temperature range of 800~840℃, the deformation is primarily plastic flow, with the average of stress exponent n=2 and activation energy Q=380 kJ/mol (PER), and Q=242.6 kJ/mol (PAR). Microstructure observations show that in the samples of PER, the new deformed bands developed in the deformation process replaced the original foliation; in the samples of PAR, the new deformed bands developed in the deformation process inherited the original foliation. Dehydration melting biotite and hornblende occurred in both PER and PAR samples at temperature of 800~840℃. EBSD analysis shows that the c-axis fabric of quartz of the original granitic gneiss localized within the Z-axis domains for basal slip, the c-axis fabric of quartz in samples with PER localized within the X-axis domains for prism slip; the c-axis fabric of quartz in samples with PAR localized within the Z-axis domains, and Y-axis, for basal slip and prism slip. This indicates that deformation of quartz in samples of PER is more thorough than that of samples of PAR, which is consistent with the microstructure analysis. Obviously, the heterogeneous fabric of samples has a significant impact on the strength and c-axis orientation of quartz, but no apparent effect in brittle-plastic transition and plastic deformation mechanisms. This study can help us to comprehensively understand bulk flow strength of rocks with pre-existing fabric. |
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| Keywords: | Fabric Rheology Microstructure High temperature and high pressure |
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