The composition of chromous pyropes lherzolitic paragenesis from diamondiferous kimberlites and palmisanos

Abstract

Pyropes are among the leading typomorphic minerals of the majority of mantle parageneses in kimberlites. In addition, it is undoubtedly the most informative and most studied as a representative of minerals of mantle origin of peridotite paragenesis and eclogite. It is remains classic to date the classification of the compositions of pyropes, which is based on the chart N. V. Sobolev CaO - Cr2O3 [1]. The discrete fields on the diagram allow us to refer the composition of pyrope to the definite parageneses. In this work it is shown that rare-earth elements are unevenly accumulated in the pyropes of diamondiferous kimberlite Seldyukarskaya pipe and barren kimberlite pipe Shandongu [2]. The bubble chart is complemented by information popular chart additional features. At the same time, additional information appears in the graph, which shows the criteria for the difference in these characteristics of the compositions of pyropes from diamondiferous and non-diamondiferous kimberlites. The study also identified additional characteristics to compositions of lherzolitic paragenesis pyropes from diamondiferous kimberlites and barren kimberlites contents of manganese and magnesium. For diamondiferous kimberlites typical of the compositions of pyropes of lerzolitic parageneses with high values of manganese oxide more than 0.4 wt% and with low values of magnesium oxide less than 20 wt%.