Occurrence of diamond in the mantle: a case study from the Siberian Platform

Abstract

The paper presents the results of detailed studies of diamond crystals from diamondiferous xenoliths and some kimberlite pipes of Yakutia. The morphology and physical properties (photoluminescence and infrared light absorption) of diamonds from mantle xenoliths allow identification of the specific characteristics of, and distinctions between, the diamonds of the peridotitic and eclogitic parageneses. The comparison of diamonds from kimberlites and mantle xenoliths has been carried out on the basis of their physical properties and morphology. It is confirmed that most if not all diamonds in kimberlites were derived from mantle peridotite and eclogite and were liberated into the kimberlite by the disaggregation of such xenoliths. Petrological investigations of mantle xenoliths indicate a significant lateral and vertical differentiation of the upper mantle under the Siberian Platform and illustrate regularities in the evolution of the mantle. Diamonds from different pipes show significant variations in morphology and physical characteristics, and there are large lateral variations and changes in the crystal morphology of diamonds from the south to the north in the Yakutian kimberlite province. It is proposed that the lateral heterogeneity of the upper mantle and the different evolution of mantle subregions determine the lateral variations in populations of diamonds.