MINERALOGY OF DIAMONDS FROM THE YUBILINAYA PIPE (YAKUTIA)

Abstract

The paper contains results of a comprehensive study of the mineralogy and physical properties of diamonds, including results of IR and UV spectroscopy, EPR spectroscopy, x-ray luminescence, carbon isotopic composition, and mineralogy and chemical composition of solid inclusions in diamonds from the Yubileǐnaya pipe. Several mineralogical varieties of diamonds and solid inclusions in them are distinguished and studied in detail. Their existence indicates various origins of diamond crystals in kimberlites. The diamond features in the Yubileǐnaya kimberlite pipe are specific for individual productive columns and invariable with depth, which allows reliable planning of diamond development. The diamonds show some specific differences in kimberlites of various intrusive phases. The history of diamond formation is traced from nucleation and crystallization in the mantle with crushing and ductile deformation in deep-seated sheared mantle rocks, dissolution with formation of rhombic dodecahedral habits during the ascent of kimberlite magma, and etching (corrosion) at the hydrothermal-pneumatolytic stage and during the autometamorphism of kimberlites.