Experimental deformation of ordered natural omphacite : a study by transmission electron microscopy

摘要: The Ca–Na clinopyroxene omphacite and garnet are the defining minerals main phases of eclogites. rheological properties eclogites dominated by mechanical behaviour omphacite. Omphacite can occur in an ordered structure with space group P 2/ n and, above 800 °C, a disordered C c . Most found Earth’s crust contain omphacites While there is increasing number studies transmission electron microscopy (TEM) deformation effects from eclogites, corresponding TEM experimentally deformed -omphacite lacking. Natural Tianshan Weissenstein were at temperatures 500 to °C strain rates ca. 10 −4 −6 s −1 deformation-DIA (D-DIA) apparatus usually 2 GPa confining pressure. In seven experiments, specimens coaxially shortened; one specimen was simple shear. investigations revealed twin lamellae on (100) (001), traces failed attempts (100), dislocations, faults parallel (010) {110} non-crystallographic faults. These crystal defects not observed all specimens; however, correlation between experimental conditions apparent. produced also naturally omphacites. experiments show that sufficient mechanisms for lower temperatures, which compensate loss perfect dislocations Burgers vector 1/2〈110〉, available only -omphacite.