METASOMATIC ZONALITY AND GENESIS OF SAPPHIRINE-BEARING ROCKS IN THE BUG REGION

Precambrian sapphirine-bearing rocks were discovered in the core of a borehole on the River Bug in the zone of the metasomatic changes of the pyroxene body. Their origin is a particular case of regional granitization and takes place in connection with the formation of charnockite. The area of modified pyroxenite, 1.7m thick in the core, has a symmetrical zonal structure and is subdivided into six subzones (in the direction to the center). I. Pyroxenite, serpentinized, carbonatized pyroxenite (initial rocks); II. Diopside-phlogopite-anorthite; III. Corundum-anorthite phlogopite; IV. Sapphirine -corundum- microcline -biotite; V. Corundum-sillimanite-sapphirine-microcline; VI. Sillimanite-sapphirine-corundum-prismatine-microcline. The minerals are not unstable together, some are replaced by others with a general tendency to forming a microcline rock. --Author's English Summary.