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本文采集了映秀—北川断裂带南段出露的发生韧性变形的花岗岩样品,分析了脆塑性转化带内的岩石变形特征、变形温度和流动应力,并利用傅里叶红外吸收光谱仪(FITR)重点对石英和长石进行了测试.研究表明,龙门山断裂带深部发生过局部化塑性流动,以中、高温位错蠕变机制为主,重结晶细粒石英的粒度约15~100μm,估算得到的流动应力约15~80MPa.石英和长石内的微量水由晶体缺陷水、颗粒边界水和少量的包裹体水构成,两者的红外吸收光谱特点非常相似,主要吸收峰出现在波数3400cm~(-1)附近,次要吸收峰主要分布在波数3050cm~(-1)、3200cm~(-1)、3300cm~(-1)、3380cm~(-1)、3430cm~(-1)、3600cm~(-1)、3650cm~(-1)和3730cm~(-1)附近.花岗片麻岩内石英的水含量0.004~0.019wt%,长石的水含量0.013~0.043wt%;花岗初糜棱岩中石英的水含量0.004~0.018wt%,长石的水含量0.029~0.069wt%,愈合片麻岩中裂缝的早期石英脉中的细粒石英的水含量0.003~0.014wt%,发生半脆性-脆性变形的晚期石英脉的水含量0.016~0.032wt%.通过与前人的研究对比,认为龙门山地区韧性剪切带内微量水含量随变形程度增加而升高,弱化了脆塑性转化带内断层中心岩石流变强度,提高断层的应变速率,加强了脆塑性转化带向脆性域底部的闭锁断层的应变传递作用.对于难以滑动的高角度逆断层,这有利于强震在中地壳深度附近的孕育和发生.
In this paper, the samples of granite with ductile deformation exposed in the southern part of Yingxiu-Beichuan fault zone are collected, and the deformation characteristics, deformation temperature and flow stress of the rock in the brittle-plastic transition zone are analyzed. The FITR The quartz and feldspar were tested.The results show that local plastic flow occurs in the deep part of the Longmen Shan fault zone and mainly occurs in the medium and high temperature dislocation creep mechanism. The grain size of recrystallized fine quartz is about 15 ~ 100μm, Of the flow stress of about 15 ~ 80MPa. Quartz and feldspar trace water from the crystal defect water, grain boundary water and a small amount of water inclusions, the two infrared absorption spectra are very similar, the main absorption peak appeared in the wave number 3400cm ~ (-1), 3300cm -1, 3380cm -1, 3430cm -1, 3600cm -1, 3300cm -1, 3200cm -1, ~ (-1), 3650cm ~ (-1) and 3730cm ~ (-1), respectively.The water content of quartz in granite gneiss was 0.004 ~ 0.019wt%, the water content of feldspar was 0.013 ~ 0.043wt% Moss quartz water content of 0.004 ~ 0.018wt%, feldspar water content of 0.029 ~ 0.069wt%, healing gneiss cracks in the early stone The water content of fine quartz in the vein ranges from 0.003 to 0.014wt%, and the water content of late quartz vein with semi-brittle-brittle deformation is 0.016 ~ 0.032wt%. By comparison with previous studies, it is considered that the ductile shear zone The micro-water content increases with the increase of deformation, weakening the rheological strength of the center of the fault in the brittle plastic transition zone, increasing the strain rate of the fault and strengthening the strain transfer of the brittle-plastic transition zone to the latticed fault at the bottom of the brittle zone. For high-angle reverse faults that are difficult to slip, this is in favor of the occurrence and occurrence of strong earthquakes near the depth of the mid-crust.