Accessory minerals of mantle xenoliths: First finds of Cl-free K-Fe sulfides

Abstract

Xenoliths of deep rocks from kimberlitic volcanic pipes are a direct source of information about struc� ture, composition, and the evolutionary processes in the Earth's lithosphere. The xenoliths from kimber� lites are of great interest, since kimberlitic melts are the deepest mantlegenerating melts. Thus, kimber� lites can contain mantle xenoliths, which can have the most complete information about the cross section of the upper mantle of ancient cratons up to the lithos� phere-asthenosphere boundary. Unfortunately, most kimberlitic rocks known in the world were subjected to synmagmatic and postmagmatic transformations, which had an influence on the mineral and chemical composition of the mantle xenoliths contained in kimberlites. Due to this, much of the information of the mantle material that could be obtained studying mantle xeno� liths was lost. The kimberlites opened in the central part of the eastern body of the Udachnaya pipe (Yakutia) at a depth of about 420 m are one of a few rare examples of unaltered kimberlites in the world (1, 2). The varia� tions in chemical composition of rocks of this block are still being studied. At present, only the chemical characteristics for some kimberlites have been obtained. In some samples a low water concentration