THE MORPHOLOGY AND REAL STRUCTURE OF MICRODIAMONDS FROM THE KOKCHETAV MASSIF METAMORPHIC ROCKS, KIMBERLITES, AND ALLUVIAL PLACERS

Abstract

A comparative study of the morphology and real structure of microdiamonds from the metamorphic rocks and alluvial placer of the Kokchetav Massif and from the Udachnaya kimberlite pipe and West-Australian alluvial placers has shown that these microdiamonds practically do not differ in the growth mechanisms, dislocation densities, and nitrogen impurity concentrations. In the Kokchetav Massif all morphological types of diamonds from kimberlites are found. The cuboids of diamonds from all types of deposits have a filamentary structure and usually contain a central core. The peculiar structure of the cuboids is explained in the context of the theory of crystal habit stability. The morphological variety of microdiamonds within a rock sample, the predominance of certain morphological types of crystals in rocks, and the inner structure and micromorphology of the cuboids allow the conclusion on the low mobility of the fluid phase during the high-pressure metamorphism responsible for the metamorphogenic-diamond formation.