Micro-Raman Spectroscopy Assessment of Chemical Compounds of Mantle Clinopyroxenes

The composition of clinopyroxenes is indicative for chemical and physical properties of mantle substrates. In this study, we present the results of Raman spectroscopy examination of clinopyroxene inclusions in natural diamonds (n = 51) and clinopyroxenes from mantle xenoliths of peridotites and eclogites from kimberlites (n = 28). The chemical composition of studied clinopyroxenes shows wide variations indicating their origin in different mantle lithologies. All clinopyroxenes have intense Raman modes corresponding to metal-oxygen translation (similar to 300-500 cm(-1)), stretching vibrations of bridging O-Si-O-br (nu(11)similar to 670 cm(-1)), and nonbridging atoms O-Si-O-nbr (nu(16)similar to 1000 cm(-1)). The peak position of the stretching vibration mode (nu(11)) for the studied clinopyroxenes varies in a wide range (23 cm(-1)) and generally correlates with their chemical composition and reflects the diopside-jadeite heterovalent isomorphism. These correlations may be used for rough estimation of these compounds using the non-destructive Raman spectroscopy technique.