Kimberlite Genesis

Abstract

In the earlier chapters on the petrology and mineralogy of kimberlite, it has been shown that kimberlite is a hybrid rock consisting of varying proportions of crystals derived from the fragmentation of upper mantle rock types together with crystals derived from the crystallization of an ultramafic magma, these being finally cemented by the late-crystallization products of the magma. Since many of the kimberlite phenocrysts are broadly similar in composition (with the exception of features such as high titanium and low chromium) to the similar species derived by the fragmentation of peridotite, it will be seen that the essential problem is the origin of the phenocrysts and the kimberlite matrix itself. In particular, it is the source and reasons for the concentration within the kimberlite matrix of the high amounts of incompatible elements (see Chap. 5, kimberlite geochemistry) that have to be explained.