МОРФОЛОГИЧЕСКИЕ ОСОБЕННОСТИ ПИРОПОВ ИЗ АЛМАЗОНОСНЫХ ПОРОД БАССЕЙНА Р. ЛУГИ

Abstract

Discovery of the West-Russian diamond-bearing subprovince with crater facies kimberlites at this area (Mikhailov e. a., 1998, 2001) extends the notion on the final stages of formation of explosion pipes, and allow to improve the knowledge on morphology of minerals associated with diamond. Morphological and chemical study of pyrope grains from conglomerate-breccia occurring within Devonian terrigene deposits at the Luga river basin shows three major habit groups of pyropes, with variations of chemical compositions inside each of these gro-ups. Existence of those three types demonstrates dependence of their surface features on consecutive growth and/or dissolution processes. It has been found that chemical composition of internal parts and external nodular crusts of pyropes differs significantly reflecting the regeneration genesis of nodules overgrowing the grain surfa-ces. The study has confirmed dependence of morphology and chemical compositions of pyropes on conditions of their crystallization and, on this base, there may be suggested a possible model of final stages in formation of py-rope morphology.