CRYSTALLOCHEMICAL AND GENETICS ASPECTS OF THE STUDY OF CLINOPYROXENES FROM PULTONIC ULTRAMAFIC INCLUSIONS IN KIMBERLITE

Abstract

Monoclinic pyroxenes are rock-forming minerals for a broad group of ultramafic upper mantle rocks (garnetiferous, garnet-spinel, garnet- or spinel-free, garnetilmenite, ilmenite-containing, etc.) which occur as inclusions in kimberlite. In addition, they occur in the kimberlite groundmass and to a lesser degree in its dispersion haloes. Analysis of their crystallochemical properties and identification of reliable tests for the paragenetic assignment of clinopyroxenes from ultramafic rocks of various depth facies is of the greatest importance for evaluating the physicochemical conditions under which such rocks were generated. This paper reports on a detailed study of the relationship between the optical and spectroscopic characteristics of Fe2+ (M2) and the crystallochemical characteristics of clinopyroxenes and an attempt to elucidate their typomorphic significance in certain genetic problems.