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在固体介质三轴实验系统中采用石英岩进行了石英-柯石英转化的实验研究.实验结果表明,在实验围压1.3GPa,温度950~1000℃,差应力1.5~1.67GPa,应变75%~81%的条件下,在塑性变形的实验样品石英岩接近端部的区域,经Raman光谱分析证实出现了细粒柯石英,显然,在差应力条件下出现柯石英的压力远小于静压条件下柯石英稳定存在的压力,这表明柯石英的形成条件不是惟一的.在差应力条件下石英-柯石英相变边界向低压方向迁移受最大主应力和差应力的控制,最大主应力形成了相对较高的应力环境,差应力导致了样品的变形.本实验柯石英出现在塑性变形的样品中,而前人报道柯石英既出现在半脆性变形的样品中,也出现在塑性变形的样品中.发生在低温半脆性域的相变机制是差应力产生的剪切变形引起力学不稳定,发生在高温塑性域的相变机制是在差应力环境下石英强烈变形产生的高位错密度引起应变不稳定,而这两种相变必须在围压大于一定值(如大于1GPa)时才能发生.
Quartzite was used in the solid medium triaxial experimental system to carry out the quartz-coke conversion experiment.The experimental results show that under the experimental confining pressure of 1.3GPa, the temperature of 950 ~ 1000 ℃, the differential stress of 1.5 ~ 1.67GPa, the strain of 75% At 81%, fine-grained coesite was confirmed by Raman spectroscopy in the area near the tip of the plastically-deformed quartz specimen of the plastically deformed specimen, apparently the coesite pressure under differential stress was much less than under static pressure The steady existence pressure of coesite suggests that the formation of coesite is not unique.The migration of quartz-coessential phase to low pressure under the condition of differential stress is controlled by the maximum principal stress and the differential stress, and the maximum principal stress forms a relative In the high stress environment, the differential stress leads to the deformation of the sample.The coesite in this experiment appears in the plastic deformation samples, whereas the coesite has been reported in both the semi-brittle deformation samples and the plastic deformation samples. The phase transition mechanism in the low-temperature and semi-brittle domain is the mechanical instability caused by the shear deformation caused by differential stress. The phase transition mechanism in the high-temperature plastic domain is the strong deformation of the quartz in the poor stress environment Students can occur when the high dislocation density due to strain instability, both of which must be a phase change pressure is greater than a certain value (e.g., greater than 1 GPa) in circumference.