Structure and Significance of Planar Deformation Features in Synthetic Quartz

Abstract

Creep tests were performed on three polished cylinders of synthetic quartz stressed normal to(10l). Observations of slip bands in reflected light, orientations of planar deformation features on a universal stage, and dislocation structures of these features on a transmission electron microscope are used to deduce slip mechanisms and deformation structures. Experimental conditions of temperature, pressure, and stress were 600° and 800°C, 3 kb, and between 1.3 and 7 kb. Slip band data imply the operation of thejbllowing slip systems (100)[ c ], (011)[ a i ],(012)[ a 1 ],(101)[ a 3 ], (102) [ a 3 ], and possibly (112). Two sets of planar deformation features are developed, which are termed laminas and lamellas. Laminas are dense tangles of dislocations subparallel to (0001), probably caused by interference between minor slip on (0001) and slip on (101) and (112). Lamellas form subparallel to the major slip planes. Those near (100) comprise dense associations of dislocations generally parallel to [ a 2 ]. They are probably edge dislocations and are of undetermined sign. The observations support the model of Christie and others (1964) that explains the optical properties of such features.