GENETIC TYPES OF ULTRAHIGH-PRESSURE MINERALS IN METEORITES

Abstract

Minerals formed in natural processes at a very high pressure serve as indicators for the genetic interpretation of both terrestrial rocks and meteorites. They contain, at least, three types of ultrahigh-pressure (UHP) minerals with principally different modes of occurrence and paragenetic relations: (1) minute diamond grains (up to 10 nm in size) that are overfilled with fluid hydrogen inclusions in association with moissanite (SiC) and incorporated into a kamacite matrix of chondrites of all chemical groups; (2) larger (10–10 000 nm) diamond grains enriched in fluid inclusions in association with daubreelite, troilite, and moissanite within kamacite injections into ureilites; and (3) ringwoodite, wadsleyite, majorite, and others in glassy veinlets within brecciated chondrites. The main stages of the evolution of the iron–stony meteoritic material of the solar system are recorded in the UHP minerals listed above.