PROPERTIES OF LAYER SILICATES FROM KIMBERLITE AND HOST ROCKS IN ZONES ACTIVELY AFFECTED BY TRAP MAGMATISM (ILLUSTRATED BY YAKUTIA)

Abstract

A kimberlite pipe found in Yakutia differs sharply in geologic structure from those studied earlier. Drillhole in kimberlite-hosting marls of the Kyllakh formation penetrated bands and lenses of andradite-grossular skarn inherit the original look of the rock and, in limestones, bodies of an essentially chloritic metasomatic rock. The latter is friable and abounds with small vugs, where euhedral pseudohexagonal chlorite crystals are coated with faceted marcasite, pyrite and calcite grains. These chlorite crystals are green in color and range in size from 5 to 8 mm. Under the binocular microscope, the chlorite flakes exhibit distinct zoning. The data indicate that the properties of the layer silicates depend both on their genesis and on the superposed effect of the dolerite sill intruded into the original host rocks. Chlorites, including the rare ordered ITC polytype, were formed at relatively low temperatures.