差应力对石英-柯石英转化压力的影响

The Effect of Differential Stress on Quartz-Coesite Transition Pressure

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 ,这表明差应力对石英 -柯石英转化具有显著影响。根据柯石英形成条件 ,石英 -柯石英相变边界向低压方向迁移有两种不同物理机制 :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应力不稳定 。

Coesite was produced at certain differential stress conditions below its stability field under static pressure in laboratary, which shows that differential stress has obvious effect on the quartz-coesite transition pressure. According to the forming conditions of coesite, there are two different physical mechanisms for shifting quartz-coesite phase transition boundary to decreased forming pressure at differential stress conditions: the phase transition in semibrittle deformation region due to local shear deformation induced mechanical instability, and the phase transition in plastic flow region due to presence of high dislocation density within highly deformed quartz induced strain instability.