Ultradeep Rocks and Diamonds in the Light of Advanced Scientific Technologies

Abstract

This is a review paper which summarizes recent achievements in studies of superdeep mantle rocks and diamonds from kimberlite and ultrahigh-pressure metamorphic (UHPM) terranes using advanced analytical techniques and instrumentations such as focused ion beam (FIB)-assisted transmission electron microscopy (TEM) and synchrotron-assisted infrared spectroscopy. In combination, they allow characterization of geological materials formed at varying pressures, temperatures, and stresses in different chemical environments, which has enabled us to make amazing advances in understanding large-scale processes operating in the Earth through plate tectonics. Mineralogical characterisations of the ultradeep earth materials using novel techniques with high spatial and energy resolution are resulting in unexpected discoveries of new phases, thereby providing better constraints on deep mantle processes. One of such results is that the nanometric fluid inclusions in diamonds from kimberlite and UHPM terranes contain similar elements such as Cl, K, P, and S. Such similarity reflects probably the high solubility of these elements in a diamond-forming C–O–H supercritical fluid at high pressures and temperatures. The paper emphasizes the necessity of further studies of diamonds occurred within geological setting (oceanic islands, foearcs and mantle sections of ophiolites) previously unrecognized as suitable places for high pressure minerals formation.