天然变形岩石中的白云母压象

PRESSURE FIGURES OF MUSCOVITE IN NATURALLY DEFORMED ROCKS

天然变形岩石中白云母压象见于丹东市四道沟金矿区元古宙变质沉积岩,即变质长石石英砂岩的糜棱岩中。在白云母压象中,相邻两组裂理交角约为60°,其中一组裂理平行于白云母光轴面,另外两组则与光轴面斜交。白云母压象形成于韧性剪切带初始活动阶段,时间上早于石英中广泛的亚晶化及动态重结晶作用阶段,其形成的温度、压力条件大致相当于下部绿片岩相,即温度在300—400℃左右,压力0.2—0.5GPa,形成时应变速率参考值不小于10^(-13)S^(-1)。

Pressure figures of muscovite developed in mylonites of Sidaogou gold mine are the result of ductile deformation. Based on the character of partings, they are divided into two types. The first type of pressure figures, probably related with the weak strains, is common, in which one set of partings parallel to the optical axial plane is longer than the other two sets; the second type, probably related with the strong strains, is less common than the first, in which three sets of partings are similar. The pressure figures formed in the early stage of ductile shear deformation, earlier than the subgrain structure and dynamic recrystallization of quartz, under the temperature and pressure conditions corresponding to the green schist facies: 300--400℃, 0. 2--0. 5GPa.