| Secondary-ion mass spectrometry (SIMS), electron probe microanalysis (EPMA), analytical scanning electron microscopy (SEM) and infrared (IR) spectroscopy were used to determine the chemical composition and mineralogy of sub-micrometer inclusions in cubic diamonds and in overgrowths (coats) on octahedral diamonds from Zaire, Botswana, and some unknown localities.;SIMS and EPMA analyses show that all the micro-inclusion-bearing diamonds are rich in water, carbonate, SiO;IR spectroscopy reveals the presence of hydrated sheet silicates, carbonate, and apatite. Water is probably associated with the silicates but may also be present as a fluid phase. Small quantities of molecular CO;It is suggested that the composition of the micro-inclusions represents a volatile-rich fluid or a melt trapped by the diamond during its growth. The high content of potassium and other incompatible elements suggests that the trapped material may represent an effective metasomatizing agent.;The origin of the fluid trapped in the micro-inclusions is still uncertain. While the high K... |
